This invention relates to the separation and oxygen-alkylation of phenols from phenol-containing hydrocarbonaceous streams such as coal liquids.
The presence of phenols in various hydrocabonaceous streams is troublesome. For example, the presence of phenols in liquids produced from coal causes instability of these liquids over a period of time by increasing the viscosity, the color intensity, and causing separation of resinous materials. Moreover, without extensive hydrotreatment, coal liquids are generally not compatible with petroleum liquids of comparable boiling point. Thus, solids separation caused largely by high concentrations of phenols, leads to severe operability problems for coal/petroleum liquid blends. Also, hydrodesulfurization and hydrodenitrogenation of coal liquids are required prior to reforming into motor gasoline. These steps require a very large consumption of hydrogen for phenol-rich coal liquids because of the extensive deoxygenation of phenols to water.
Various methods of removing these troublesome phenols from hydrocarbonaceous streams are taught in the art. For example, it is taught that weakly acidic organic substances such as phenols can be removed from hydrocarbonaceous streams by use of alkali metal or alkaline-earth metal oxides and hydroxides. See U.K. Pat. No. 494,450. It is also taught that phenols react with these oxides and hydroxides resulting in the formation of phenoxide salts which can be easily separated from the purified stream. See U.S. Pat. No. 4,256,568 and French Pat. No. 838,900. Further, it is known that certain phenoxide salts, such as calcium phenoxide, can be heated in the presence of carbon dioxide to yield phenols and calcium carbonate. See Franz Fischer and UDO Ehrahart. Ges. Abhandl. Kenninis Kohle 4,237-63 (1919).
Another method taught for separating phenols from hydrocarbonaceous streams is to wash the stream with large quantities of water or aqueous caustic solutions such as sodium or potassium hydroxide.
Although such methods are practiced on a commercial scale in various industries, there are various drawbacks associated with them. For example, most of the aforesaid methods consume a mol of expensive alkali or alkaline earth metal for each mol of phenol removed. Therefore, there is still a need to develop a more efficient process for removing troublesome phenols from hydrocarbonaceous streams, recovering the phenols in a more efficient and inexpensive way, and converting the phenols to more useful products such as ethers.