This invention relates to a supported metal catalyst composition, a process of making such supported metal catalyst composition, and to a process of using such supported metal catalyst composition for hydrogenating a highly unsaturated hydrocarbon.
It is known to one skilled in the art that a less unsaturated hydrocarbon compound can be produced by a thermal cracking process. For example, a fluid stream containing a saturated hydrocarbon such as, for example, ethane, propane, butane, pentane, naphtha, and the like and combinations thereof can be fed into a thermal (or pyrolytic) cracking furnace. Within the furnace, the saturated hydrocarbon is converted to a less unsaturated hydrocarbon compound such as, for example, ethylene or propylene. Such less unsaturated hydrocarbons are an important class of chemicals that find a variety of industrial uses. For example, ethylene can be used as a monomer or comonomer for producing a polyolefin. Other uses of unsaturated hydrocarbons are well known to one skilled in the art.
However, such less unsaturated hydrocarbon produced by a thermal cracking process generally contains an appreciable amount of less desirable highly unsaturated hydrocarbon(s) such as alkyne(s) or diolefin(s). For example, ethylene produced by thermal cracking of ethane is generally contaminated with a highly unsaturated hydrocarbon, such as acetylene, which must be selectively hydrogenated to a less unsaturated hydrocarbon, such as ethylene, but not to a saturated hydrocarbon such as ethane, in a hydrogenation reaction.
In addition, catalysts comprising palladium and an inorganic support, such as alumina, are known catalysts for the hydrogenation of highly unsaturated hydrocarbons such as alkynes and/or diolefins. In the case of the selective hydrogenation of acetylene to ethylene, a palladium and silver catalyst supported on alumina can be employed. See for example U.S. Pat. No. 4,404,124 and U.S. Pat. No. 4,484,015, the disclosures of which are incorporated herein by reference. The operating temperature for this hydrogenation process is selected such that essentially all highly unsaturated hydrocarbon such as alkyne (e.g., acetylene) is hydrogenated to its corresponding less unsaturated hydrocarbon such as alkene (e.g., ethylene) thereby removing the alkyne from the product stream while only an insignificant amount of alkene is hydrogenated to a saturated hydrocarbon such as alkane (e.g., ethane). Such selective hydrogenation process minimizes the loss of desired less unsaturated hydrocarbons and, in the front-end and total cracked gas processes, avoids a xe2x80x9crunawayxe2x80x9d reaction which is difficult to control, as has been pointed out in the above-identified patents.
It is also generally known to those skilled in the art that impurities, such as carbon monoxide, and sulfur impurities, such H2S, COS, mercaptans and organic sulfides, which are present in an alkyne-containing feed or product stream can poison and deactivate a palladium-containing catalyst. For example, carbon monoxide is well known to temporarily poison or inactivate such hydrogenation catalyst. It is also generally known by those skilled in the art that a sulfur impurity such as a sulfur compound (such as H2S, COS, mercaptans, and organic sulfides), when present during the hydrogenation of highly unsaturated hydrocarbons such as diolefins (alkadienes) or alkynes to less unsaturated hydrocarbons such as monoolefins (alkenes), can poison and deactivate hydrogenation catalysts. This is especially true in a depropanizer hydrogenation process because the feed stream from the depropanizer being sent to the acetylene removal unit (also referred to as xe2x80x9cARUxe2x80x9d) of such depropanizer hydrogenation process typically contains low levels of a sulfur compound(s) with the possibility of transient spikes in the level of such sulfur compound(s). Thus, the development of a catalyst composition and its use in processes for the hydrogenation of highly unsaturated hydrocarbons such as diolefins (alkadienes) or alkynes to less unsaturated hydrocarbons such as monoolefins (alkenes) in the presence of a sulfur impurity such as a sulfur compound would also be a significant contribution to the art and to the economy.
A palladium-containing xe2x80x9cskinxe2x80x9d catalyst in which palladium is distributed on the surface or xe2x80x9cskinxe2x80x9d of the catalyst has been developed which is known to be more selective and active than a non-skin catalyst in converting acetylene in an ethylene stream to ethylene. See for example, U.S. Pat. No. 4,484,015. It is known that the catalyst selectivity is determined, in part, by the skin thickness. Generally, catalyst selectivity decreases as the skin thickness increases. There is therefore an ever-increasing need to develop a catalyst having a better xe2x80x9cskinxe2x80x9d on the catalyst for a better selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, without further hydrogenation to a saturated hydrocarbon, such as an alkane.
Palladium supported on alumina has been successfully used in dry hydrogenation processes for many years. However, in some processes such as the so-called xe2x80x9ctotal cracked gasxe2x80x9d process in which the steam is not removed from the olefins stream, the selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, must be accomplished in the presence of steam. In such process(es), the alumina supported catalyst may have a much shorter life because alumina is not stable in steam. Therefore, there is also an increasing need to develop a palladium-containing catalyst on a steam-stable support.
As such, development of an improved palladium catalyst and a process therewith in the selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, in the presence of an impurity would be a significant contribution to the art and to the economy.
It is also generally known that catalysts having a metal aluminate support, such as a zinc aluminate support, can be used in the selective hydrogenation and dehydrogenation of hydrocarbons. In general, prior art processes to produce such metal aluminate support typically involve physically mixing a metal component, such as metal oxide, and an aluminum component, such as aluminum oxide, followed by drying and calcining to produce a metal aluminate catalyst support containing a metal aluminate such as a zinc aluminate, also referred to as a zinc spinel. Another common process of producing such metal aluminate catalyst support comprises coprecipitating an aqueous solution of a metal component, such as metal nitrate, and an aqueous solution of an aluminum component, such as aluminum nitrate, followed by drying and calcining such as the process disclosed in U.S. Pat. No. 3,641,182. However, these processes are costly and time-consuming. Consequently, a process to produce a metal aluminate catalyst support, which does not involve physical mixing or coprecipitation, which can be incorporated with palladium and a catalyst component comprising either silver, an alkali metal compound, or both silver and an alkali metal compound, and which can be used in the selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, in the presence of an impurity would also be of significant contribution to the art and to the economy.
An object of this invention is to provide a catalyst composition that can be used for selectively hydrogenating a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene. Such catalyst composition can be useful as a catalyst in the hydrogenation of a highly unsaturated hydrocarbon such as a diolefin and/or alkyne to a less unsaturated hydrocarbon such as a monoolefin.
Another object of this invention is to provide a palladium-containing catalyst composition wherein the palladium is better distributed on the skin of the catalyst composition, as compared to known xe2x80x9cskinxe2x80x9d catalysts.
Yet another object of the present invention is to provide a catalyst composition which comprises a metal aluminate catalyst support wherein such metal aluminate catalyst support is prepared by a process that does not involve the physical mixing of a metal component and an aluminum component.
Still another object of the present invention is to provide a catalyst composition which comprises a metal aluminate catalyst support wherein such metal aluminate catalyst support is prepared by a process that does not involve a coprecipitation of a metal component and an aluminum component.
A further object of the present invention is to provide a catalyst composition which comprises a metal aluminate catalyst support which is prepared by a process that is economically cheaper and easier than a method(s) other than the inventive process(es) disclosed herein or prior art methods.
A still further object of the present invention is to provide a method of making such catalyst composition and to provide a process of using such catalyst composition to hydrogenate a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, without further hydrogenation to a saturated hydrocarbon, such as an alkane.
A yet further object of this invention is to employ this catalyst composition in the hydrogenation of a highly unsaturated hydrocarbon such as a diolefin or an alkyne to a less unsaturated hydrocarbon. An advantage of this invention is that there is an increased or enhanced selectivity to a desired product such as a less unsaturated hydrocarbon compared to a catalyst composition prepared by methods other than the inventive process(es) disclosed herein.
According to a first embodiment of this invention, a catalyst composition is provided which can be used for selectively hydrogenating a highly unsaturated hydrocarbon such as, for example, an alkyne or a diolefin. The catalyst composition comprises palladium, an inorganic support material comprising a metal aluminate (i.e., a metal aluminate catalyst support), and a catalyst component comprising either silver or an alkali metal compound, or both silver and an alkali metal compound. Such metal aluminate catalyst support is prepared by a process which comprises incorporating alumina with a metal component, preferably impregnating alumina with a melted metal component, to thereby provide a metal-incorporated alumina followed by drying and high temperature calcining to thereby provide a metal aluminate catalyst support. Such metal aluminate catalyst support contains a metal aluminate similar to those metal aluminate catalyst supports produced by physically mixing a metal component, such as metal oxide, and an aluminum component, such as aluminum oxide, or coprecipitating a metal-containing solution and an aluminum-containing solution, followed by drying and calcining.
According to a second embodiment of this invention, a process which can be used for selectively hydrogenating a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon is provided. The process comprises contacting a highly unsaturated hydrocarbon with hydrogen, in the presence of a catalyst composition, under a condition sufficient to effect a selective hydrogenation of the highly unsaturated hydrocarbon. The catalyst composition can be the same as the catalyst composition disclosed in the first embodiment of this invention.
Other objects and advantages of the invention will be apparent from the detailed description of the invention and the appended claims.
As used in the present invention, the term xe2x80x9cfluidxe2x80x9d denotes gas, liquid, vapor, or combinations thereof. The term xe2x80x9cpalladiumxe2x80x9d refers to palladium metal. The term xe2x80x9csilverxe2x80x9d refers to silver metal. The term xe2x80x9csubstantialxe2x80x9d or xe2x80x9csubstantiallyxe2x80x9d generally means more than trivial. The term xe2x80x9csaturated hydrocarbonxe2x80x9d refers to any hydrocarbon which does not contain any carbon-to-carbon double bonds or carbon-to-carbon triple bonds. Examples of saturated hydrocarbons include, but are not limited to, ethane, propane, butanes, pentanes, hexanes, octanes, decanes, naphtha, and the like and combinations thereof.
The term xe2x80x9chighly unsaturated hydrocarbonxe2x80x9d refers to a hydrocarbon having a triple bond or two or more double bonds between carbon atoms in the molecule. Examples of highly unsaturated hydrocarbons include, but are not limited to, aromatic compounds such as benzene and naphthalene; alkynes such as acetylene, propyne (also referred to as methylacetylene), and butynes; diolefins such as propadiene, butadienes, pentadienes (including isoprene), hexadienes, octadienes, and decadienes; and the like and combinations thereof.
The term xe2x80x9cless unsaturated hydrocarbonxe2x80x9d refers to a hydrocarbon in which the triple bond in the highly unsaturated hydrocarbon is hydrogenated to a double bond or a hydrocarbon in which the number of double bonds is one less, or at least one less, than that in the highly unsaturated hydrocarbon. Examples of less unsaturated hydrocarbons include, but are not limited to, monoolefins such as ethylene, propylene, butenes, pentenes, hexenes, octenes, decenes, and the like and combinations thereof.
The term xe2x80x9chydrogenation processxe2x80x9d refers to a process which converts a highly unsaturated hydrocarbon such as an alkyne or a diolefin to a less unsaturated hydrocarbon such as a monoolefin or a saturated hydrocarbon such as an alkane. The term xe2x80x9cselectivexe2x80x9d refers to such hydrogenation process in which a highly unsaturated hydrocarbon such as an alkyne or a diolefin is converted to a less unsaturated hydrocarbon such as a monoolefin without further hydrogenating the less unsaturated hydrocarbon to a saturated hydrocarbon such as an alkane. Thus, for example, when a highly unsaturated hydrocarbon is converted to a less unsaturated hydrocarbon without further hydrogenating such less unsaturated hydrocarbon to a saturated hydrocarbon, the hydrogenation process is xe2x80x9cmore selectivexe2x80x9d than when such highly unsaturated hydrocarbon is hydrogenated to a less unsaturated hydrocarbon and then further hydrogenated to a saturated hydrocarbon.
According to the first embodiment of this invention, a catalyst composition which can be used to selectively hydrogenate a highly unsaturated hydrocarbon (such as an alkyne or a diolefin) to a less unsaturated hydrocarbon (such as an alkene or a monoolefin) is provided. The catalyst composition comprises (a) palladium such as palladium metal, palladium oxide, or combinations thereof, (b) a catalyst component comprising silver or an alkali metal compound or both silver and an alkali metal compound, and (c) an inorganic support comprising a metal aluminate wherein the palladium can be present as xe2x80x9cskinxe2x80x9d on or near the surface of the catalyst composition and the silver or alkali metal compound, or both if present, can be distributed as skin with the palladium or throughout the catalyst composition.
The term xe2x80x9cskinxe2x80x9d refers to the exterior surface of the catalyst composition which can contain components, such as palladium, of the catalyst composition. The skin can be any thickness as long as such thickness can promote the hydrogenation process(es) disclosed herein. Generally, the thickness of the skin can be in the range of from about 1 micron to about 1000 microns, preferably in the range of from about 5 microns to about 750 microns, more preferably in the range of from about 5 microns to about 500 microns, and most preferably in the range of from 10 microns to 300 microns. Preferably, the palladium is concentrated in the skin of the catalyst composition whereas the catalyst component comprising silver or an alkali metal compound, or both silver and an alkali metal compound, is distributed throughout the catalyst composition.
The catalyst composition hydrogenates more effectively when the skin is relatively thin (such as the most preferable skin thickness of 10 microns to 300 microns) than when then the skin is thicker (such as greater than 300 microns). Thus, there is a significant benefit, better or more selective hydrogenation, by preparing a catalyst composition with a thin skin, rather than a thick skin. Further, there is a significant benefit, better hydrogenation, by preparing a catalyst composition with a skin than a catalyst composition without a skin.
Various skin catalysts have been developed. See for example U.S. Pat. No. 4,404,124 and U.S. Pat. No. 4,484,015, the disclosures of which are incorporated herein by reference.
One can use any suitable method to determine the concentration of the palladium in the skin of the catalyst composition. Determining the concentration of the palladium in the skin of the catalyst composition also helps in determining the thickness of the skin. One technique currently favored is the electron microprobe which is known to one skilled in the art. Another technique involves breaking open a representative sample of the catalyst composition (in catalyst particle form) and treating the catalyst particles with a dilute alcoholic solution of N,N-dimethyl-para-nitrosoaniline. The treating solution reacts with the palladium to give a red color which can be used to evaluate the distribution of the palladium. Another technique for measuring the concentration of the palladium in the skin of the catalyst composition involves breaking open a representative sample of catalyst particles followed by treatment with a reducing agent such as, for example, hydrogen, to change the color of the skin to evaluate the distribution of the palladium.
Generally, palladium can be present in the catalyst composition in any weight percent so long as the palladium is substantially concentrated as skin on or near the surface of the catalyst composition and that such weight percent is effective in selectively hydrogenating a highly unsaturated hydrocarbon (such as an alkyne) to a less unsaturated hydrocarbon (such as an alkene). Generally, the catalyst composition comprises palladium in the range of from about 0.0001 weight percent palladium based on the total weight of the catalyst composition to about 3 weight percent palladium, preferably in the range of from about 0.0005 weight percent palladium to about 1.5 weight percent palladium and, most preferably, in the range of from 0.001 weight percent palladium to 1.0 weight percent palladium.
Examples of suitable palladium compounds which can be used for incorporating the palladium of such palladium compounds into, onto, or with an inorganic support include, but are not limited to, palladium bromide, palladium chloride, palladium iodide, palladium nitrate, palladium nitrate hydrate, tetraamine palladium nitrate, palladium oxide, palladium oxide hydrate, palladium sulfate, and the like and combinations thereof. The palladium can have any available oxidation state. The presently preferred palladium compound is palladium chloride. Most preferably, hydrochloric acid is added to such palladium chloride (PdCl2) to form a PdCl4xe2x88x922 complex. Excess hydrochloric acid should be avoided. When added to the support by impregnation from solution, some of the compounds can be added from aqueous solution, but others will require non-aqueous solvents such as alcohols, hydrocarbons, ethers, ketones and the like.
The catalyst composition can additionally comprise a catalyst component comprising silver. Silver can be present in the catalyst composition in any weight percent as long as such weight percent is effective in selectively hydrogenating a highly unsaturated hydrocarbon (such as an alkyne) to a less unsaturated hydrocarbon (such as an alkene). Generally, the catalyst composition comprises silver in the range of from about 0.0003 weight percent silver based on the total weight of the catalyst composition to about 20 weight percent silver, preferably in the range of from about 0.003 weight percent silver to about 10 weight percent silver and, most preferably, in the range of from 0.003 weight percent silver to 5 weight percent silver. Generally, the weight ratio of silver to palladium (Ag:Pd weight ratio) in the catalyst composition can be in the range of from about 0.1:1 to about 20:1, preferably in the range of from about 1:1 to about 10:1 and, most preferably, in the range of from 3:1 to 8:1.
Suitable examples of silver compounds for use in incorporating, preferably impregnating, the silver of such silver compound(s) into, onto, or with the inorganic support include, but are not limited to, silver nitrate, silver acetate, silver cyanide and the like and combinations thereof. The presently preferred silver compound is silver nitrate.
In lieu of a catalyst component comprising silver or in addition to silver, the catalyst composition can additionally comprise a catalyst component comprising an alkali metal compound. Any alkali metal-containing compound(s) can be used in the catalyst composition as long as the resulting catalyst composition is effective in selectively hydrogenating a highly unsaturated hydrocarbon (such as an alkyne) to a less unsaturated hydrocarbon (such as an alkene). Suitable examples of alkali metal compounds for use in incorporating, preferably impregnating, the alkali metal compound(s) into, onto, or with the inorganic support generally include, but are not limited to, alkali metal halides, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, alkali metal nitrates, alkali metal carboxylates, and the like and combinations thereof. Preferably, the alkali metal compound is an alkali metal halide, more preferably the alkali metal compound is an alkali metal iodide or an alkali metal fluoride. Generally, the alkali metal of such alkali metal compound is selected from the group consisting of potassium, rubidium, cesium, and the like and combinations thereof. Preferably, the alkali metal of such alkali metal compound is potassium. Preferably, the alkali metal compound is potassium iodide (KI) and, more preferably, the alkali metal compound is potassium fluoride (KF).
Further examples of suitable alkali metal compounds include sodium fluoride, potassium fluoride, lithium fluoride, rubidium fluoride, cesium fluoride, sodium iodide, potassium iodide, lithium iodide, rubidium iodide, cesium iodide, sodium chloride, potassium chloride, lithium chloride, rubidium chloride, cesium chloride, sodium bromide, potassium bromide, lithium bromide, rubidium bromide, cesium bromide, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, sodium oxide, potassium oxide, lithium oxide, rubidium oxide, cesium oxide, sodium carbonate, potassium carbonate, lithium carbonate, rubidium carbonate, cesium carbonate, sodium nitrate, potassium nitrate, lithium nitrate, rubidium nitrate, cesium nitrate, and the like and combinations thereof.
Generally, the catalyst composition comprises alkali metal in the range of from about 0.001 weight percent alkali metal to about 10 weight percent alkali metal based on the total weight of the catalyst composition. Preferably, the catalyst composition comprises alkali metal in the range of from about 0.005 weight percent alkali metal to about 5 weight percent alkali metal and, most preferably, in the range of from 0.01 weight percent alkali metal to 2 weight percent alkali metal. Generally, the weight ratio of alkali metal to palladium is in the range of from about 0.05:1 to about 500:1. Preferably, the weight ratio of alkali metal to palladium is in the range of from about 0.1:1 to about 200:1 and, most preferably, in the range of from 0.2:1 to 100:1.
When the alkali metal compound is an alkali metal iodide, the catalyst composition comprises alkali metal iodide in the range of from about 0.03 weight percent iodine (chemically bound as iodide) (on a total catalyst composition weight basis) to about 10 weight percent iodine. Preferably, the catalyst composition comprises alkali metal iodide in the range of from about 0.1 weight percent iodine to about 5 weight percent iodine and, most preferably, in the range of from 0.2 weight percent iodine to 1 weight percent iodine. Generally, the atomic ratio of iodine to alkali metal is in the range of from about 0.5:1 to about 4:1. Preferably, the atomic ratio of iodine to alkali metal is in the range of from about 1:1 to about 3:1. When the alkali metal compound is an alkali metal iodide, it should be used in lieu of the silver.
When the alkali metal compound is an alkali metal fluoride, the catalyst composition comprises alkali metal fluoride in the range of from about 0.03 weight percent fluorine (chemically bound as fluoride) (on a total catalyst composition weight basis) to about 10 weight percent fluorine. Preferably, the catalyst composition comprises alkali metal fluoride in the range of from about 0.1 weight percent fluorine to about 5 weight percent fluorine and, most preferably, in the range of from 0.2 weight percent fluorine to 1 weight percent fluorine. Generally, the atomic ratio of fluorine to alkali metal is in the range of from about 0.5:1 to about 4:1. Preferably, the atomic ratio of fluorine to alkali metal is in the range of from about 1:1 to about 3:1.
The inorganic support material of this invention comprises a metal aluminate prepared by an inventive process(es) which does not involve the physical mixing of a metal component and an aluminum component and does not involve a coprecipitation of a metal component and an aluminum component. When a catalyst composition comprises an inorganic support material prepared according to the inventive process(es) disclosed herein and additionally comprises palladium and a catalyst component comprising either silver or an alkali metal compound, or both silver and an alkali metal compound, and is utilized in the hydrogenation of a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon, there is an increased or enhanced selectivity to a desired product such as a less unsaturated hydrocarbon when compared to a catalyst composition comprising an inorganic support material prepared by methods other than the inventive process(es) disclosed herein.
It has been discovered that a metal aluminate catalyst support can be readily prepared from existing pre-formed alumina (also referred to as aluminum oxide) tablets, pellets, extrudates, spheres, and the like and combinations thereof by incorporating, preferably impregnating, such alumina with a metal component, preferably a melted metal component, followed by drying, and then high temperature calcining. The resulting metal aluminate catalyst support contains a metal aluminate such as a zinc aluminate, also referred to as a zinc spinel, which is readily formed on the outside of, i.e., on the surface of, the alumina. Such metal aluminate catalyst support preparation is considerably cheaper and easier than preparation techniques involving physically mixing a metal component, such as metal oxide, and an aluminum component, such as aluminum oxide, or coprecipitating metal-containing and aluminum-containing solutions, followed by extended calcining and then pelletizing and/or extruding to form catalyst pellets or granules.
Generally, the alumina used in producing the metal aluminate catalyst support according to the inventive process(es) disclosed herein can be any suitable alumina such as, but not limited to, alpha alumina, beta alumina, delta alumina, eta alumina, gamma alumina, and the like and combinations thereof. Preferably, such alumina is gamma alumina. The alumina can also contain minor amounts of other ingredients, such as, for example, silica in a range of from about 1 weight percent silica to about 10 weight percent silica, which do not adversely affect the quality of the metal aluminate catalyst support. Generally, it is desirable to have an essentially pure alumina, preferably essentially pure gamma alumina, as a starting material for preparing the metal aluminate catalyst support. The starting alumina can be made by any manner or method(s) known in the art. As an example, a suitable commercially available starting alumina for use in preparing the metal aluminate catalyst support according to the inventive process(es) described herein are gamma alumina tablets or extrudate pellets or spheres such as those manufactured by UOP Inc., McCook, Ill., and Engelhard Company, Elyria, Ohio.
Alumina suitable for use in the inventive process(es) described herein can also be characterized by having the following characteristics. Generally, the surface area of the alumina is in the range of from about 5 m2/g (measured by the Brunauer, Emmett, Teller method, i.e. BET method) to about 400 m2/g, preferably in the range of from about 10 m2/g to about 300 m2/g and, most preferably, in the range of from 50 m2/g to 200 m2/g.
The pore volume of the alumina is generally in the range of from about 0.05 mL/g to about 2 mL/g, preferably in the range of from about 0.10 mL/g to about 1.5 mL/g and, most preferably, in the range of from 0.20 mL/g to 1 mL/g.
The average pore diameter of the alumina is generally in the range of from about 5 angstroms to about 600 angstroms, preferably in the range of from about 10 angstroms to about 500 angstroms and, most preferably, in the range of from 25 angstroms to 200 angstroms.
The alumina can have any suitable shape or form. Preferably such alumina is in the form of tablets, pellets, extrudates, spheres, and the like and combinations thereof. The alumina generally has a particle size in the range of from about 0.5 millimeters (mm) to about 10 mm, preferably in the range of from about 1 mm to about 8 mm and, most preferably, in the range of from 1 mm to 6 mm.
Any metal component which can form a spinel when utilized in accordance with the inventive process(es) disclosed herein can be used. Examples of a potentially suitable metal component for incorporating the metal of such metal component, preferably impregnating the metal of such metal component into, onto, or with the alumina to thereby provide a metal-incorporated alumina include, but are not limited to, a zinc component, a magnesium component, a calcium component, a barium component, a beryllium component, a cobalt component, an iron component, a manganese component, a strontium component, a lithium component, a potassium component, and the like and combinations thereof. Preferable examples of a potentially suitable metal component for incorporating the metal of such metal component, preferably impregnating the metal of such metal component into, onto, or with the alumina to thereby provide a metal-incorporated alumina include, but are not limited to, a zinc component, a magnesium component, a calcium component, and the like and combinations thereof. More preferably, such metal component is a zinc component.
Examples of a potentially suitable zinc component for incorporating zinc, preferably impregnating zinc into, onto, or with the alumina include, but are not limited to, zinc nitrate hexahydrate, zinc nitrate, hydrated zinc nitrate, zinc chloride, zinc acetate dihydrate, zinc acetylacetonate hydrate, zinc carbonate hydroxide monohydrate, zinc perchlorate hexahydrate, hydrated zinc sulfate, zinc sulfate monohydrate, zinc sulfate heptahydrate, and the like and combinations thereof. The preferred zinc component for incorporating zinc, preferably impregnating zinc into, onto, or with the alumina is hydrated zinc nitrate. The most preferred zinc component for incorporating zinc, preferably impregnating zinc into, onto, or with the alumina is zinc nitrate hexahydrate.
Examples of a potentially suitable magnesium component for incorporating magnesium, preferably impregnating magnesium into, onto, or with the alumina include, but are not limited to, magnesium nitrate hexahydrate, magnesium nitrate, hydrated magnesium nitrate, magnesium chloride, hydrated magnesium chloride, magnesium chloride hexahydrate, magnesium acetate tetrahydrate, magnesium acetylacetonate dihydrate, magnesium carbonate hydroxide pentahydrate, magnesium perchlorate, magnesium perchlorate hexahydrate, magnesium sulfate, magnesium sulfate heptahydrate, magnesium sulfate monohydrate, and the like and combinations thereof. The preferred magnesium component for incorporating magnesium, preferably impregnating magnesium into, onto, or with the alumina is hydrated magnesium nitrate. The most preferred magnesium component for incorporating magnesium, preferably impregnating magnesium into, onto, or with the alumina is magnesium nitrate hexahydrate.
Examples of a potentially suitable calcium component for incorporating calcium, preferably impregnating calcium into, onto, or with the alumina include, but are not limited to, calcium nitrate tetrahydrate, calcium nitrate, hydrated calcium nitrate, calcium chloride, hydrated calcium chloride, calcium chloride dihydrate, calcium chloride hexahydrate, calcium chloride hydrate, calcium acetate hydrate, calcium acetate monohydrate, calcium acetylacetonate hydrate, calcium perchlorate tetrahydrate, calcium sulfate, calcium sulfate dihydrate, calcium sulfate hemihydrate, and the like and combinations thereof. The preferred calcium component for incorporating calcium, preferably impregnating calcium into, onto, or with the alumina is hydrated calcium nitrate. The most preferred calcium component for incorporating calcium, preferably impregnating calcium into, onto, or with the alumina is calcium nitrate tetrahydrate.
Examples of a potentially suitable barium component for incorporating barium, preferably impregnating barium into, onto, or with the alumina include, but are not limited to, barium nitrate, hydrated barium nitrate, barium chloride, hydrated barium chloride, barium chloride dihydrate, barium acetate, barium acetylacetonate hydrate, barium carbonate, barium perchlorate, barium perchlorate trihydrate, barium sulfate, and the like and combinations thereof. The preferred barium component for incorporating barium, preferably impregnating barium into, onto, or with the alumina is hydrated barium nitrate. The most preferred barium component for incorporating barium, preferably impregnating barium into, onto, or with the alumina is barium nitrate.
Examples of a potentially suitable beryllium component for incorporating beryllium, preferably impregnating beryllium into, onto, or with the alumina include, but are not limited to, beryllium nitrate trihydrate, hydrated beryllium nitrate, beryllium chloride, hydrated beryllium sulfate, beryllium sulfate tetrahydrate, and the like and combinations thereof. The preferred beryllium component for incorporating beryllium, preferably impregnating beryllium into, onto, or with the alumina is hydrated beryllium nitrate. The most preferred beryllium component for incorporating beryllium, preferably impregnating beryllium into, onto, or with the alumina is beryllium nitrate trihydrate.
Examples of a potentially suitable cobalt component for incorporating cobalt, preferably impregnating cobalt into, onto, or with the alumina include, but are not limited to, cobalt nitrate hexahydrate, hydrated cobalt nitrate, cobalt chloride, hydrated cobalt chloride, cobalt chloride hexahydrate, cobalt chloride hydrate, cobalt acetate tetrahydrate, cobalt acetylacetonate, cobalt acetylacetonate hydrate, cobalt carbonate hydrate, cobalt perchlorate hexahydrate, hydrated cobalt sulfate, cobalt sulfate hydrate, and the like and combinations thereof. The preferred cobalt component for incorporating cobalt, preferably impregnating cobalt into, onto, or with the alumina is hydrated cobalt nitrate. The most preferred cobalt component for incorporating cobalt, preferably impregnating cobalt into, onto, or with the alumina is cobalt nitrate hexahydrate.
Examples of a potentially suitable iron component for incorporating iron, preferably impregnating iron into, onto, or with the alumina include, but are not limited to, iron nitrate nonahydrate, hydrated iron nitrate, iron chloride, hydrated iron chloride, iron chloride tetrahydrate, iron chloride hexahydrate, iron acetate, iron acetylacetonate, iron perchlorate hexahydrate, hydrated iron sulfate, iron sulfate heptahydrate, and the like and combinations thereof. The preferred iron component for incorporating iron, preferably impregnating iron into, onto, or with the alumina is hydrated iron nitrate. The most preferred iron component for incorporating iron, preferably impregnating iron into, onto, or with the alumina is iron nitrate nonahydrate.
Examples of a potentially suitable manganese component for incorporating manganese, preferably impregnating manganese into, onto, or with the alumina include, but are not limited to, manganese nitrate hexahydrate, hydrated manganese nitrate, manganese nitrate hydrate, manganese chloride, hydrated manganese chloride, manganese chloride tetrahydrate, manganese acetate dihydrate, manganese acetate tetrahydrate, manganese acetylacetonate, manganese carbonate, manganese perchlorate hexahydrate, hydrated manganese sulfate, manganese sulfate monohydrate, and the like and combinations thereof. The preferred manganese component for incorporating manganese, preferably impregnating manganese into, onto, or with the alumina is hydrated manganese nitrate. The most preferred manganese component for incorporating manganese, preferably impregnating manganese into, onto, or with the alumina is manganese nitrate hexahydrate.
Examples of a potentially suitable strontium component for incorporating strontium, preferably impregnating strontium into, onto, or with the alumina include, but are not limited to, strontium nitrate, hydrated strontium nitrate, strontium chloride, hydrated strontium chloride, strontium chloride hexahydrate, strontium acetate, strontium acetylacetonate, strontium carbonate, strontium perchlorate hydrate, hydrated strontium sulfate, strontium sulfate, and the like and combinations thereof. The preferred strontium component for incorporating strontium, preferably impregnating strontium into, onto, or with the alumina is strontium nitrate.
Examples of a potentially suitable lithium component for incorporating lithium, preferably impregnating lithium into, onto, or with the alumina include, but are not limited to, lithium nitrate, hydrated lithium nitrate, lithium chloride, hydrated lithium chloride, lithium chloride hydrate, lithium acetate dihydrate, lithium acetylacetonate, lithium perchlorate, lithium perchlorate trihydrate, lithium sulfate, lithium sulfate monohydrate, and the like and combinations thereof. The preferred lithium component for incorporating lithium, preferably impregnating lithium into, onto, or with the alumina is lithium nitrate.
Examples of a potentially suitable potassium component for incorporating potassium, preferably impregnating potassium into, onto, or with the alumina include, but are not limited to, potassium nitrate, hydrated potassium nitrate, potassium chloride, hydrated potassium chloride, potassium acetylacetonate hemihydrate, potassium carbonate sesquihydrate, potassium perchlorate, potassium sulfate, and the like and combinations thereof. The preferred potassium component for incorporating potassium, preferably impregnating potassium into, onto, or with the alumina is potassium nitrate.
The metal component(s) may be incorporated into, onto, or with the alumina by any suitable means or method(s) for incorporating the metal of such metal component(s) into, onto, or with a substrate material, such as alumina, which results in the formation of a metal-incorporated alumina which can then be dried and calcined to thereby provide a metal aluminate catalyst support. Examples of means or method(s) for incorporating include, but are not limited to, impregnating, soaking, spraying, and the like and combinations thereof. A preferred method of incorporating is impregnating using any standard incipient wetness impregnation technique (i.e., essentially completely filling the pores of the substrate material with a solution of the incorporating elements) for impregnating an alumina substrate with a metal component. A preferred method uses an impregnating solution comprising the desirable concentration of metal component so as to ultimately provide a metal-incorporated, preferably metal-impregnated, alumina which can then be subjected to drying and high temperature calcining to produce a metal aluminate catalyst support.
It can be desirable to use an aqueous solution of a metal component for the impregnation of the alumina. A preferred impregnating solution comprises an aqueous solution formed by dissolving a metal component, preferably such metal component is in the form of a metal salt, such as, but not limited to, a metal chloride, a metal nitrate, a metal sulfate, and the like and combinations thereof, in a solvent, such as, but not limited to, water, alcohols, esters, ethers, ketones, and the like and combinations thereof.
A preferred impregnating solution is formed by dissolving a metal component (such as zinc nitrate hexahydrate, magnesium nitrate hexahydrate, calcium nitrate tetrahydrate, barium nitrate, beryllium nitrate trihydrate, cobalt nitrate hexahydrate, iron nitrate nonahydrate, manganese nitrate hexahydrate, strontium nitrate, lithium nitrate, potassium nitrate, preferably, zinc nitrate hexahydrate) in water. It is acceptable to use somewhat of an acidic solution to aid in the dissolution of the metal component. It is preferred for the alumina to be impregnated with a zinc component by use of a solution containing zinc nitrate hexahydrate dissolved in water. In addition, magnesium nitrate hexahydrate or calcium nitrate tetrahydrate or barium nitrate or beryllium nitrate trihydrate or cobalt nitrate hexahydrate or iron nitrate nonahydrate or manganese nitrate hexahydrate or strontium nitrate or lithium nitrate or potassium nitrate can be used in place of zinc nitrate hexahydrate to impregnate the alumina with the metal of the respective metal component(s).
A more preferred method for incorporating a metal of a metal component into, onto, or with the alumina is to impregnate such alumina with a metal component which has been melted under a melting condition as described herein. Preferably such metal component is in the form of a metal salt, such as, but not limited to, a metal chloride, a metal nitrate, a metal sulfate, and the like and combinations thereof (such as, but not limited to, zinc nitrate hexahydrate, magnesium nitrate hexahydrate, calcium nitrate tetrahydrate, barium nitrate, beryllium nitrate trihydrate, cobalt nitrate hexahydrate, iron nitrate nonahydrate, manganese nitrate hexahydrate, strontium nitrate, lithium nitrate, potassium nitrate, and the like and combinations thereof, preferably, zinc nitrate hexahydrate). Addition of small amounts of an aqueous medium such as water to the metal component can be used to assist in the melting of such metal component.
Such melting condition includes a temperature below the decomposition temperature of the metal component for a time period and at a pressure that provides for a melted metal component, preferably a pourable melted metal component. The term xe2x80x9cdecomposition temperaturexe2x80x9d refers to the temperature at which the metal component is no longer soluble and is no longer suitable for incorporating, preferably impregnating, the metal of such metal component into, onto, or with alumina according to the inventive process(es) disclosed herein. The term xe2x80x9cpourable melted metal componentxe2x80x9d refers to a metal component that has been subjected to a melting condition and has become viscous enough to pour.
The temperature below the decomposition temperature of the metal component varies depending on the metal component but such temperature should be such as to provide a melted metal component. Such temperature is generally in the range of from about 25xc2x0 C. to about 160xc2x0 C., preferably in the range of from about 30xc2x0 C. to about 150xc2x0 C., more preferably in the range of from about 35xc2x0 C. to about 140xc2x0 C. and, most preferably, in the range of from 35xc2x0 C. to 130xc2x0 C.
Such melting condition can include a time period generally in the range of from about 1 minute to about 2 hours, preferably in the range of from about 5 minutes to about 1.5 hours and, most preferably, in the range of from 5 minutes to 1 hour. Such melting condition can include a pressure generally in the range of from about atmospheric (i.e., about 14.7 pounds per square inch absolute) to about 150 pounds per square inch absolute (psia), preferably in the range of from about atmospheric to about 100 psia, most preferably about atmospheric, so long as the desired temperature can be maintained.
The thus-melted metal component is then used to incorporate, preferably impregnate, the metal of such melted metal component into, onto, or with the alumina. The metal of such melted metal component is incorporated, preferably impregnated, into, onto, or with the alumina by adding such melted metal component to the alumina by pouring such melted metal component onto the surface of the alumina by any manner or method(s) which results in substantially all the surface area of the alumina being coated with the melted metal component. Preferably, such melted metal component is poured over the surface of the alumina while the alumina is under constant stirring or tumbling.
It can be desirable to pre-heat the alumina under a heating condition before such melted metal component is poured over the surface of the alumina. Such heating condition can include a temperature generally in the range of from about 80xc2x0 C. to about 150xc2x0 C., preferably in the range of from about 85xc2x0 C. to about 140xc2x0 C. and, most preferably, in the range of from 90xc2x0 C. to 130xc2x0 C. Such heating condition can include a time period generally in the range of from about 1 minute to about 2 hours, preferably in the range of from about minutes to about 1.5 hours and, most preferably, in the range of from 5 minutes to 1 hour. Such heating condition can include a pressure generally in the range of from about atmospheric (i.e., about 14.7 pounds per square inch absolute) to about 150 pounds per square inch absolute (psia), preferably in the range of from about atmospheric to about 100 psia, most preferably about atmospheric, so long as the desired temperature can be maintained. The metal-incorporated, preferably metal-impregnated, alumina can be further heated near the melting point of the metal component for a time period in the range of from about 0.5 hour to about 15 hours, preferably in the range of from about 1 hour to about 8 hours and, most preferably, in the range of from 1 hour to 5 hours.
In a most preferred method, melted zinc nitrate hexahydrate is used to incorporate, preferably impregnate, the zinc of such melted zinc nitrate hexahydrate into, onto, or with the alumina. The zinc of such melted zinc nitrate hexahydrate is incorporated, preferably impregnated, into, onto, or with the alumina by adding such melted zinc nitrate hexahydrate to the alumina by pouring such melted zinc nitrate hexahydrate onto the surface of the alumina by any manner or method(s) which results in substantially all the surface area of the alumina being coated with the melted zinc nitrate hexahydrate. Preferably, such melted zinc nitrate hexahydrate is poured over the surface of the alumina while the alumina is under constant stirring or tumbling. In addition, magnesium nitrate hexahydrate or calcium nitrate tetrahydrate or barium nitrate or beryllium nitrate trihydrate or cobalt nitrate hexahydrate or iron nitrate nonahydrate or manganese nitrate hexahydrate or strontium nitrate or lithium nitrate or potassium nitrate can be used in place of zinc nitrate hexahydrate to incorporate, preferably impregnate, the metal of such metal component(s) into, onto, or with the alumina in the same above-described manner as for incorporating, preferably impregnating, the zinc of such zinc nitrate hexahydrate.
Generally, the amount of metal component, preferably zinc component, incorporated, preferably impregnated, into, onto, or with the alumina is an amount which provides, after the metal-incorporated alumina has been dried and calcined according to the inventive process(es) disclosed herein, a metal aluminate catalyst support having an amount of metal aluminate generally in the range of from about 1 weight percent of the total weight of the metal aluminate catalyst support to about 100 weight percent. Preferably the amount of metal in, on, or with the metal-incorporated alumina is in an amount which provides a metal aluminate catalyst support having an amount of metal aluminate in the range of from about 15 weight percent of the total weight of the metal aluminate catalyst support to about 75 weight percent and, most preferably, in the range of from 25 weight percent to 65 weight percent.
The metal-incorporated alumina can then be dried under a drying condition. Generally, such drying condition can include a temperature in the range of from about 80xc2x0 C. to about 140xc2x0 C., preferably in the range of from about 90xc2x0 C. to about 130xc2x0 C. and, most preferably, in the range of from 100xc2x0 C. to 120xc2x0 C. Such drying condition can also include a time period for drying the metal-incorporated alumina generally in the range of from about 0.5 hour to about 60 hours, preferably in the range of from about 1 hour to about 40 hours and, most preferably, in the range of from 1.5 hours to 20 hours to produce a dried metal-incorporated alumina. Such drying condition can also include a pressure generally in the range of from about atmospheric (i.e., about 14.7 pounds per square inch absolute) to about 150 pounds per square inch absolute (psia), preferably in the range of from about atmospheric to about 100 psia, most preferably about atmospheric, so long as the desired temperature can be maintained. Any drying method(s) known to one skilled in the art such as, for example, air drying, heat drying, and the like and combinations thereof can be used.
The thus-dried metal-incorporated alumina can then be calcined under a calcining condition to thereby provide a metal aluminate catalyst support. The calcining condition is important in providing a metal aluminate catalyst support having physical characteristics, such as, for example, a surface area, pore volume, average pore diameter, and crystalline domain size, in the ranges as disclosed herein, suitable for using such metal aluminate catalyst support as a support for hydrogenation and dehydrogenation catalysts.
Generally, such calcining condition can include a temperature in the range of from about 600xc2x0 C. to about 1350xc2x0 C., preferably in the range of from about 675xc2x0 C. to about 1300xc2x0 C., more preferably, in the range of from about 800xc2x0 C. to about 1250xc2x0 C. and, most preferably, in the range of from 900xc2x0 C. to 1200xc2x0 C. Such calcining condition can also include a pressure, generally in the range of from about 7 pounds per square inch absolute (psia) to about 750 psia, preferably in the range of from about 7 psia to about 450 psia and, most preferably, in the range of from 7 psia to 150 psia, and a time period in the range of from about 1 hour to about 60 hours, preferably for a time period in the range of from about 2 hours to about 20 hours and, most preferably, for a time period in the range of from 3 hours to 15 hours.
Upon calcination of the dried metal-incorporated alumina, a metal aluminate will form in, on the outside surface of, or on, but not limited to, the surface of, the alumina to thereby provide a metal aluminate catalyst support of the invention. Examples of a suitable metal aluminate include, but are not limited to, a zinc aluminate, also referred to as a zinc spinel, a magnesium aluminate, also referred to as a magnesium spinel, a calcium aluminate, also referred to as a calcium spinel, a barium aluminate, also referred to as a barium spinel, a beryllium aluminate, also referred to as a beryllium spinel, a cobalt aluminate, also referred to as a cobalt spinel, an iron aluminate, also referred to as an iron spinel, a manganese aluminate, also referred to as a manganese spinel, a strontium aluminate, also referred to as a strontium spinel, a lithium aluminate, also referred to as a lithium spinel, a potassium aluminate, also referred to as a potassium spinel, and the like and combinations thereof. A preferred metal aluminate is selected from the group consisting of a zinc aluminate, also referred to as a zinc spinel, a magnesium aluminate, also referred to as a magnesium spinel, a calcium aluminate, also referred to as a calcium spinel, and the like and combinations thereof. A more preferred metal aluminate is a zinc aluminate, also referred to as a zinc spinel.
The amount of metal aluminate of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, is generally in the range of from about 1 weight percent based on the total weight of the metal aluminate catalyst support to about 100 weight percent. Preferably, the amount of metal aluminate of the metal aluminate catalyst support of the invention is in the range of from about 15 weight percent based on the total weight of the metal aluminate catalyst support to about 75 weight percent and, most preferably, in the range of from 25 weight percent to 65 weight percent.
The amount of alpha alumina of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, is generally in the range of from about 0 weight percent based on the total weight of the metal aluminate catalyst support to about 99 weight percent, preferably in the range of from about 10 weight percent to about 85 weight percent and, most preferably, in the range of from 15 weight percent to 70 weight percent. The crystalline domain size of the alpha alumina of the metal aluminate catalyst support is generally in the range of from about 25 angstroms to about 3000 angstroms, preferably in the range of from about 25 angstroms to about 2500 angstroms and, most preferably, in the range of from 50 angstroms to 2000 angstroms. The xe2x80x9ccrystalline domain sizexe2x80x9d is determined from the line broadening of the X-ray diffraction profile.
The amount of gamma alumina of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, generally ranges upwardly from about 0 weight percent based on the total weight of the metal aluminate catalyst support to about 60 weight percent, preferably in the range of from about 0 weight percent to about 50 weight percent and, most preferably, in the range of from 0 weight percent to 40 weight percent.
Generally, the surface area of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, is in the range of from about 1 m2/g (measured by the Brunauer, Emmett, Teller method, i.e. BET method) to about 200 m2/g, preferably in the range of from about 1 m2/g to about 150 m2/g, more preferably in the range of from about 5 m2/g to about 125 m2/g and, most preferably, in the range of from 10 m2/g to 80 m2/g.
The pore volume of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, is generally in the range of from about 0.05 mL/g to about 2 mL/g, preferably in the range of from about 0.10 mL/g to about 1.5 mL/g and, most preferably, in the range of from 0.10 mL/g to 1 mL/g.
The average pore diameter of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, is generally in the range of from about 50 angstroms to about 1000 angstroms, preferably in the range of from about 50 angstroms to about 750 angstroms and, most preferably, in the range of from 50 angstroms to 450 angstroms.
The crystalline domain size of the metal aluminate, preferably zinc aluminate, of the metal aluminate catalyst support is generally in the range of from about 25 angstroms to about 1750 angstroms, preferably in the range of from about 25 angstroms to about 1500 angstroms, more preferably in the range of from about 25 angstroms to about 1250 angstroms and, most preferably, in the range of from 25 angstroms to 1000 angstroms.
The particle size of the metal aluminate catalyst support, preferably zinc aluminate catalyst support, is generally in the range of from about 0.5 millimeter (mm) to about 10 mm, preferably in the range of from about 1 mm to about 8 mm and, most preferably, in the range of from 1 mm to 6 mm.
The catalyst composition can be fresh or it can be a used and thereafter oxidatively regenerated catalyst composition. The catalyst composition can have any suitable shape such as spherical, cylindrical, trilobal, or combinations thereof. The preferred shape is either spherical or cylindrical. The particles of the catalyst composition generally have a size in the range of from about 0.5 millimeters (mm) to about 10 mm, preferably in the range of from about 1 mm to about 8 mm and, most preferably, in the range of from 1 mm to 6 mm. Generally, the surface area of the catalyst composition is in the range of from about 1 m2/g (measured by the Brunauer, Emmett, Teller method, i.e., BET method) to about 200 m2/g, preferably in the range of from about 1 m2/g to about 150 m2/g, more preferably in the range of from about 5 m2/g to about 125 m2/g and, most preferably, in the range of from 10 m2/g to 80 m2/g.
The catalyst composition can be prepared by any suitable method(s) or means which results in palladium concentrated in the exterior surface skin of the catalyst composition with a catalyst component comprising silver or an alkali metal compound, or both silver and an alkali metal compound, distributed in the skin or throughout the catalyst composition. Generally, the extent of penetration of the palladium into the skin of the catalyst composition can be controlled by adjustment of the acidity of the palladium-containing solution, used in preparing the catalyst composition, with an acid such as, for example, hydrochloric acid. For example, if the palladium compound is palladium chloride (PdCl2), hydrochloric acid should be added to the palladium-containing solution containing the palladium chloride to form a PdCl4xe2x88x922 complex. Excess hydrochloric acid should be avoided. The catalyst composition components (a) palladium and/or at least one palladium oxide, and (b) a catalyst component comprising either silver or an alkali metal compound (preferably potassium fluoride), or both silver and an alkali metal compound, can be deposited onto and/or incorporated into or with the inorganic support material (comprising a metal aluminate prepared in accordance with the inventive process(es) disclosed herein) by any suitable means and in any suitable order.
The palladium can be incorporated (e.g., by ion exchange or impregnation) into, onto, or with the inorganic support comprising a metal aluminate. A preferred impregnation utilizes an incipient wetness impregnation technique in which a solution of the incorporating element(s) is used to essentially completely fill the pores of a substrate material (such as an inorganic support). The inorganic support can also be sprayed with an impregnating solution comprising a palladium compound. Generally, the concentration of the palladium compound in the impregnating solution is in the range of from about 0.01 mmol/L to about 5 mol,/L preferably in the range of from about 0.1 mmol/L to about 2 mol/L. Preferably, the solvent of the impregnating solution is water or an alcohol such as ethanol or mixtures thereof. The weight ratio of the impregnating solution comprising a palladium compound to the inorganic support can be any ratio that can produce the catalyst composition comprising palladium in the weight percent ranges disclosed herein.
For example, a catalyst component comprising silver or an alkali metal compound, or both silver and an alkali metal compound, can be incorporated into the inorganic support material comprising a metal aluminate (prepared in accordance with the inventive process(es) disclosed herein) by impregnation, followed by impregnation with at least one Pd compound (such as H2PdCl4) to obtain an impregnated material, drying the impregnated material under a composition drying condition as described herein to obtain a dried material, and then heating (calcining) under a composition calcining condition as described herein to obtain a final catalyst composition of this invention.
More preferably, an inorganic support material comprising a metal aluminate (prepared in accordance with the inventive process(es) disclosed herein) is impregnated with at least one Pd compound (such as H2PdCl4) to obtain a palladium-impregnated material, drying the impregnated material under a composition drying condition as described herein to obtain a dried material, and then heating (calcining) under a composition calcining condition as described herein to thereby obtain a dried and calcined palladium/metal aluminate composition. The palladium/metal aluminate composition can then be contacted with a solution (preferably aqueous) of at least one silver compound, preferably silver nitrate, (i.e., a silver-containing solution) or an alkali metal compound, preferably potassium fluoride, (i.e., an alkali metal compound-containing solution) followed by drying under a composition drying condition as described herein to obtain a dried material, and then heating (calcining) under a composition calcining condition as described herein to thereby obtain a final catalyst composition of this invention having a concentration of silver or alkali metal in the ranges as disclosed herein.
The palladium/metal aluminate composition can be contacted with a solution (preferably aqueous) of a silver compound (i.e., a silver-containing solution) followed by drying under a composition drying condition as described herein to obtain a dried material, and then heating (calcining) under a composition calcining condition as described herein to thereby obtain a palladium/silver/metal aluminate composition. Such palladium/silver/metal aluminate composition can then be contacted with a solution of an alkali metal compound (i.e., an alkali metal compound-containing solution) followed by drying under a composition drying condition as described herein to obtain a dried material, and then heating (calcining) under a composition calcining condition as described herein to thereby obtain a final catalyst composition of this invention having concentrations of silver and alkali metal in the ranges as disclosed herein.
In addition, an alkali metal compound (or an alkali metal compound-containing solution) can be incorporated (e.g., by impregnation or spraying) onto the inorganic support material comprising a metal aluminate before such support is impregnated with a suitable palladium compound (or a palladium-containing solution) and, if desired, with a suitable silver compound (or a silver-containing solution). Alternatively, an alkali metal compound can be incorporated (e.g., by impregnation or spraying) with an inorganic support material comprising a metal aluminate simultaneously with or after the impregnation with a suitable palladium compound. When silver is also present in the catalyst composition, an alkali metal compound can be incorporated with the inorganic support material between the palladium and silver impregnation steps or after the impregnation with palladium and silver compounds.
Also for example, a palladium/silver/metal aluminate composition as described herein can be contacted, preferably impregnated, with an aqueous solution of at least one alkali metal hydroxide and/or at least one alkali metal fluoride (preferably KOH and/or KF), followed by drying under a composition drying condition as described herein and calcining under a composition calcining condition as described herein. At least one xe2x80x9cwet-reducingxe2x80x9d agent (i.e., one or more than one dissolved reducing agent) can also be present during the contacting of the palladium/silver/metal aluminate composition with at least one alkali metal hydroxide and/or at least one alkali metal fluoride. Non-limiting examples of such xe2x80x9cwet-reducingxe2x80x9d agents are: hydrazine, an alkali metal borohydride, an aldehyde containing 1-6 carbon atoms per molecule such as formaldehyde, a ketone containing 1-6 carbon atoms per molecule, a carboxylic acid containing 1-6 carbon atoms per molecule such as formic acid or ascorbic acid, a reducing sugar containing an aldehyde or alpha-hydroxyketone group such as dextrose, and the like and combinations thereof.
Also for example, a palladium/silver/metal aluminate composition as described herein can be contacted, preferably impregnated, with a non-alkali metal fluoride (preferably selected from the group consisting of HF, NH4F, NH4HF2, and the like and combinations thereof, more preferably NH4F) disclosed herein in any suitable manner. The non-alkali metal fluoride (preferably NH4F) can be incorporated together with palladium and an alkali metal compound or a suitable silver compound (or palladium and both an alkali metal compound and a suitable silver compound). Or, the non-alkali metal fluoride can be incorporated after the impregnation of the inorganic support material comprising a metal aluminate with palladium and an alkali metal compound, or palladium and both an alkali metal compound and a suitable silver compound. After the incorporation of palladium, alkali metal, fluoride (and/or silver) compounds into the support material has been completed (as described herein), the thus-obtained material is dried under a composition drying condition as described herein and then calcined under a composition calcining condition as described herein. Optionally, the calcined material can then be reduced with hydrogen gas (preferably at a temperature in the range of from about 30xc2x0 C. to about 100xc2x0 C., for a time period in the range of from about 0.5 hour to about 20 hours), so as to reduce oxides of palladium and of silver (if present) to the corresponding metal(s).
Generally, the concentration of a silver compound or an alkali metal compound (preferably an alkali fluoride compound) in the contacting solution (preferably aqueous) is in the range of from about 0.01 mmol/L to about 10 mol/L (preferably in the range of from about 0.1 mmol/L to about 3 mol/L). The preferred silver contacting method is by soaking, i.e., essentially completely filling the pores and the external surface of the inorganic support material comprising a metal aluminate with a silver compound-containing solution. The preferred alkali metal contacting method is xe2x80x9cincipient wetness impregnation,xe2x80x9d i.e., essentially completely filling the pores of the inorganic support material comprising a metal aluminate with an alkali metal compound-containing solution (preferably an alkali fluoride-containing solution). Generally, the weight ratio of a silver-containing compound solution or an alkali metal compound-containing solution to the inorganic support material can be any ratio that can produce a catalyst composition having a concentration of silver or alkali metal, or both silver and alkali metal, in the ranges disclosed herein. The impregnated material can then be dried under a composition drying condition as described herein followed by calcining under a composition calcining condition as described herein to obtain the final catalyst composition.
Generally a composition drying condition, as referred to herein, includes a temperature in the range of from about 35xc2x0 C. to about 160xc2x0 C., preferably in the range of from about 40xc2x0 C. to about 155xc2x0 C. and, most preferably, in the range of from 45xc2x0 C. to 150xc2x0 C. Such composition drying condition includes a time period for conducting such drying generally in the range of from about 0.5 hour to about 6 hours, preferably in the range of from about 1 hour to about 5 hours and, most preferably, in the range of from 1.5 hours to 4 hours. Such composition drying condition includes a pressure in the range of from about atmospheric (i.e., about 14.7 pounds per square inch absolute) to about 100 pounds per square inch absolute (psia), preferably about atmospheric.
Generally a composition calcining condition, as referred to herein, includes calcining of the composition either in air or in a non-oxidizing gas atmosphere at a temperature in the range of from about 200xc2x0 C. to about 800xc2x0 C., preferably at a temperature in the range of from about 250xc2x0 C. to about 600xc2x0 C. and, most preferably, at a temperature in the range of from 350xc2x0 C. to 550xc2x0 C. Such composition calcining condition generally includes a time period in the range of from about 0.5 hour to about 40 hours, preferably for a time period in the range of from about 0.75 hour to about 30 hours and, most preferably, for a time period in the range of from 1 hour to 20 hours. Such composition calcining condition generally includes a pressure in the range of from about 7 pounds per square inch absolute (psia) to about 750 psia, preferably in the range of from about 7 psia to about 450 psia and, most preferably, in the range of from 7 psia to 150 psia.
According to the second embodiment of this invention, a hydrogenation process is provided. The hydrogenation process of this invention can comprise contacting a hydrocarbon-containing fluid which comprises one or more highly unsaturated hydrocarbon(s) such as an aromatic hydrocarbon(s), alkyne(s), and/or diolefin(s) with the catalyst composition disclosed herein in the presence of hydrogen in a hydrogenation zone under a hydrogenation condition to hydrogenate such one or more highly unsaturated hydrocarbon(s) to a less unsaturated hydrocarbon such as a monoolefin. The highly unsaturated hydrocarbon(s) is present in the hydrocarbon-containing fluid as an impurity generally at a level found in typical commercial feed streams. The highly unsaturated hydrocarbon(s) is present in the hydrocarbon-containing fluid generally in the range of from about 1 part by weight highly unsaturated hydrocarbon(s) per billion parts by weight hydrocarbon-containing fluid (i.e., about 1 ppb) to about 50 parts by weight highly unsaturated hydrocarbon(s) per 500 parts by weight hydrocarbon-containing fluid (i.e., about 10 weight percent), typically at a level in the range of from about 10 ppb to about 5 weight percent and, most typically, at a level in the range of from 100 ppb to 1 weight percent.
Hydrogen can be present either in the hydrocarbon-containing fluid or in a hydrogen-containing fluid which is mixed with the hydrocarbon-containing fluid before contacting with the catalyst composition disclosed herein. If a hydrogen-containing fluid is used, it can be a substantially pure hydrogen or any fluid containing a sufficient concentration of hydrogen to effect the hydrogenation disclosed herein. It can also contain other gases such as, for example, nitrogen, methane, carbon monoxide, carbon dioxide, steam, or combinations thereof so long as the hydrogen-containing fluid contains a sufficient concentration of hydrogen to effect the hydrogenation disclosed herein.
Optionally, the catalyst can be first treated, prior to the hydrogenation disclosed herein, with a hydrogen-containing fluid to activate the catalyst composition. Such reductive, or activation, treatment can be carried out at a temperature generally in the range of from about 20xc2x0 C. to about 200xc2x0 C., preferably in the range of from about 25xc2x0 C. to about 150xc2x0 C. and, most preferably, in the range of from 30xc2x0 C. to 125xc2x0 C. for a time period in the range of from about 1 minute to about 30 hours, preferably in the range of from about 0.5 hour to about 25 hours and, most preferably, in the range of from 1 hour to 20 hours at a pressure generally in the range of from about 1 pound per square inch absolute to about 1000 pounds per square inch absolute (psia), preferably in the range of from about 14.7 psia to about 500 psia and, most preferably, in the range of from 60 psia to 200 psia. During this reductive treatment, palladium and silver compounds (primarily oxides) which may be present in the catalyst composition after the composition drying step and the composition calcining step described herein are substantially reduced to palladium and silver. When this optional reductive treatment is not carried out, the hydrogen gas present in the reaction medium accomplishes this reduction of oxides of palladium and silver during the initial phase of the selective hydrogenation reaction(s) of this invention.
The hydrocarbon-containing fluid of the hydrogenation process(es) of this invention can also comprise one or more less unsaturated hydrocarbon(s) such as a monoolefin(s) and one or more saturated hydrocarbon(s) such as an alkane(s). These additional hydrocarbons can be present in the hydrocarbon-containing fluid at a level in the range of from about 0.001 weight percent to about 99.999 weight percent.
Examples of suitable alkynes include, but are not limited to, acetylene, propyne (also referred to as methylacetylene), 1-butyne, 2-butyne, 1-pentyne, 2-pentyne, 3-methyl-1-butyne, 1-hexyne, 1-heptyne, 1-octyne, 1-nonyne, 1-decyne, and the like and combinations thereof. The presently preferred alkynes are acetylene and propyne.
The alkynes are primarily hydrogenated to the corresponding alkenes. For example, acetylene is primarily hydrogenated to ethylene; propyne is primarily hydrogenated to propylene; and the butynes are primarily hydrogenated to the corresponding butenes (e.g., 1-butene, 2-butenes).
Examples of suitable diolefins include those containing in the range of from 3 carbon atoms per molecule to about 12 carbon atoms per molecule. Such diolefins include, but are not limited to, propadiene, 1,2-butadiene, 1,3-butadiene, isoprene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, 1,2-hexadiene, 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, 2-methyl-1,2-pentadiene, 2,3-dimethyl-1,3-butadiene, heptadienes, methylhexadienes, octadienes, methylheptadienes, dimethylhexadienes, ethylhexadienes, trimethylpentadienes, methyloctadienes, dimethylheptadienes, ethyloctadienes, trimethylhexadienes, nonadienes, decadienes, undecadienes, dodecadienes, cyclopentadienes, cyclohexadienes, methylcyclopentadienes, cycloheptadienes, methylcyclohexadienes, dimethylcyclopentadienes, ethylcyclopentadienes, dicyclopentadiene, and the like and combinations thereof.
Presently preferred diolefins are propadiene, 1,2-butadiene, 1,3-butadiene, pentadienes (such as 1,3-pentadiene, 1,4-pentadiene, isoprene), cyclopentadienes (such as 1,3-cyclopentadiene) and dicyclopentadiene (also known as tricyclo[5.2.1]2.6deca-3,8-diene). These diolefins are preferably hydrogenated to their corresponding monoolefins containing the same number of carbon atoms per molecule as the diolefins. For example, propadiene is hydrogenated to propylene, 1,2-butadiene and 1,3-butadiene are hydrogenated to 1-butene and 2-butene, 1,3-pentadiene and 1,4-pentadiene are hydrogenated to 1-pentene and 2-pentene, isoprene is hydrogenated to methyl-1-pentenes and methyl-2-pentenes, and 1,3-cyclopentadiene is hydrogenated to cyclopentene.
Examples of suitable aromatic hydrocarbons include, but are not limited to, benzene, toluene, ethylbenzene, styrene, xylenes, and the like and combinations thereof.
Examples of suitable monoolefins include, but are not limited to, ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-pentene, 2-pentene, methyl-1-butenes (such as 2-methyl-1-butene), methyl-2-butenes (such as 2-methyl-2-butene), 1-hexene, 2-hexene, 3-hexene, methyl-1-pentenes, 2,3-dimethyl-1-butene, 1-heptene, 2-heptene, 3-heptene, methyl-1-hexenes, methyl-2-hexenes, methyl-3-hexenes, dimethylpentenes, ethylpentenes, octenes, methylheptenes, dimethylhexenes, ethylhexenes, nonenes, methyloctenes, dimethylheptenes, ethylheptenes, trimethylhexenes, cyclopentene, cyclohexene, methylcyclopentene, cycloheptene, methylcyclohexene, dimethylcyclopentenes, ethylcyclopentenes, cyclooctenes, methylcycloheptenes, dimethylcyclohexenes, ethylcyclohexenes, trimethylcyclohexenes, methylcyclooctenes, dimethylcyclooctenes, ethylcyclooctenes, and the like and combinations thereof.
Examples of suitable saturated hydrocarbons include, but are not limited to, methane, ethane, propane, butane, methylpropane, methylbutane, dimethylbutane, pentanes, hexanes, and the like and combinations thereof.
Furthermore, the hydrocarbon-containing fluid can contain in the range of from about 0.001 weight percent hydrogen to about 5 weight percent hydrogen, and up to 5000 parts per million by volume (ppmv) of carbon monoxide.
The hydrocarbon-containing fluid disclosed herein may contain an impurity at a level which does not significantly interfere with the hydrogenation process of a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon as described herein. The term xe2x80x9cimpurityxe2x80x9d as used herein denotes any component in a hydrocarbon-containing fluid that is not a major component. Examples of impurities other than an alkyne or a diolefin include, but are not limited to carbon monoxide, hydrogen sulfide, carbonyl sulfide (COS), carbon disulfide (CS2), mercaptans (RSH), organic sulfides (RSR), organic disulfides (RSSR), thiophene, organic trisulfides, organic tetrasulfides, and the like and combinations thereof, wherein each R can be an alkyl or cycloalkyl or aryl group containing 1 carbon atom to about 15 carbon atoms, preferably 1 carbon atom to 10 carbon atoms. It is within the scope of this invention to have additional compounds (such as water, alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, other oxygenated compounds, and the like and combinations thereof) present in the hydrocarbon-containing fluid, as long as they do not significantly interfere with the hydrogenation process of a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon as described herein.
The hydrogenation process(es) of this invention is generally carried out by contacting a hydrocarbon-containing fluid comprising at least one highly unsaturated hydrocarbon, in the presence of hydrogen, with the catalyst composition of this invention under a hydrogenation condition. The hydrocarbon-containing fluid can be contacted by any suitable manner with the catalyst composition described herein which is contained within a hydrogenation zone. Such hydrogenation zone can comprise, for example, a reactor vessel.
The contacting step, of contacting the hydrocarbon-containing fluid with the catalyst composition disclosed herein, can be operated as a batch process step or, preferably, as a continuous process step. In the latter operation, a solid or fixed catalyst bed or a moving catalyst bed or a fluidized catalyst bed can be employed. Preferably, a fixed catalyst bed is employed. Any of these operational modes have advantages and disadvantages, and those skilled in the art can select the one most suitable for a particular hydrocarbon-containing fluid and catalyst composition.
The contacting step is preferably carried out within a hydrogenation zone, wherein is contained the catalyst composition disclosed herein, and under a hydrogenation condition that suitably promotes the hydrogenation process of a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon as described herein. Such hydrogenation condition should be such as to avoid significant hydrogenation of a less unsaturated hydrocarbon(s) being initially present in the hydrocarbon-containing fluid to a saturated hydrocarbon(s) such as an alkane(s) or cycloalkane(s).
Generally, such hydrogenation process comprises the presence of hydrogen, preferably hydrogen gas, in an amount in the range of from about 0.1 mole of hydrogen employed for each mole of highly unsaturated hydrocarbon present in the hydrocarbon-containing fluid to about 1000 moles of hydrogen employed for each mole of highly unsaturated hydrocarbon present in the hydrocarbon-containing fluid. Preferably, such hydrogenation process comprises the presence of hydrogen, preferably hydrogen gas, in an amount in the range of from about 0.5 mole to about 500 moles of hydrogen employed for each mole of highly unsaturated hydrocarbon present in the hydrocarbon-containing fluid and, most preferably, in the range of from 0.7 mole to 200 moles of hydrogen employed for each mole of highly unsaturated hydrocarbon present in the hydrocarbon-containing fluid.
Generally, such hydrogenation condition comprises a temperature and a pressure necessary for the hydrogenation process(es) of this invention depending largely upon the activity of the catalyst composition, the hydrocarbon-containing fluid, and the desired extent of hydrogenation. Generally, such temperature is in the range of from about 10xc2x0 C. to about 300xc2x0 C., preferably in the range of from about 20xc2x0 C. to about 250xc2x0 C. and, most preferably, in the range of from 20xc2x0 C. to 200xc2x0 C. A suitable pressure is generally in the range of from about 15 pounds per square inch gauge (psig) to about 2000 psig, preferably in the range of from about 50 psig to about 1500 psig and, most preferably, in the range of from 100 psig to 1000 psig.
Such hydrogenation condition further comprises the flow rate at which the hydrocarbon-containing fluid is charged (i.e., the charge rate of hydrocarbon-containing fluid) to the hydrogenation zone. The flow rate is such as to provide a gas hourly space velocity (xe2x80x9cGHSVxe2x80x9d) generally exceeding 1 liter/liter/hour. The term xe2x80x9cgas hourly space velocityxe2x80x9d, as used herein, shall mean the numerical ratio of the rate at which a hydrocarbon-containing fluid is charged to the hydrogenation zone in liters per hour at standard condition of temperature and pressure (xe2x80x9cSTPxe2x80x9d) divided by the liters of catalyst composition contained in the hydrogenation zone to which the hydrocarbon-containing fluid is charged. Typically, the gas hourly space velocity of the hydrocarbon-containing fluid will be in the range of from about 1 to about 50,000 liters of hydrocarbon-containing fluid per liter of catalyst per hour (liter/liter/hour), preferably in the range of from about 750 to about 40,000 liter/liter/hour and, most preferably, in the range of from 1000 to about 30,000 liter/liter/hour.
If it is desired to regenerate the catalyst composition of this invention after prolonged use in the hydrogenation process(es) described herein, the regeneration can be accomplished by calcining the catalyst composition in an oxidizing atmosphere such as in air at a temperature that does not exceed about 700xc2x0 C. to burn off carbonaceous and sulfur deposits. Optionally, the catalyst composition can be reimpregnated with palladium and a catalyst component comprising either silver or an alkali metal compound, or both silver and an alkali metal compound, and then dried and calcined as described herein for the production of a fresh catalyst composition of this invention.
The following examples are presented to further illustrate this invention and are not to be construed as unduly limiting the scope of this invention.