The present invention relates to a manufacturing method for 1,1,1,3,3-pentafluoropropane and/or 1-chloro-3,3,3-trifluoropropene.
1,1,1,3,3-Pentafluoropropane is industrially important compound used as an HFC foaming agent, refrigerant or jetting agent, and is widely accepted as a fluoride that is kind to the environment since it does not destroy the ozone layer even when released into the air.
The following manufacturing methods for 1,1,1,3,3-pentafluoropropane are currently available.
Namely, the method described in WO 95/04022 first obtains 1,1,1,3,3,3-hexachloropropane by the addition reaction of carbon tetrachloride with vinylidene chloride. 1,1,1,3,3,3-hexachloropropane is fluorinated to give 1,1,1,3,3-pentafluoro-3-chloropropane. This is then reduced with hydrogen to obtain the desired product. Another method described in EPO 611744 uses 1,1,1,3,3-pentafluoro-2,3-dichloropropane and 1,1,1,3,3-pentafluoro-2, 3, 3-trichloropropane obtained in the previous process. These are reduced with hydrogen to give the desired product.
However, all of these manufacturing methods are not suited to industrial processes and are uneconomical because they require two different processes: a fluorinated process to obtain the precursor by fluorination of the chloride, and a reduction process to further reduce the precursor with hydrogen; and involve complicated steps.
Further, there are relatively new manufacturing methods using more simplified processes that first obtain 1,1,1,3,3-pentachloropropane by an addition reaction of carbon tetrachloride with vinyl chloride. 1,1,1,3,3-pentachloropropane is fluorinated using the following known methods: (1) fluorination by HF (hydrogen fluoride) in the liquid phase in the presence of a fluorination catalyst to give the desired product (WO 96/01797); and (2) fluorination by HF in the gaseous phase similarly in the presence of a fluorination catalyst to give the desired product (Japanese Patent Laid-Open No. 183,740/97).
In another method, 1,1,1,3,3-pentafluoropropane is produced as an objective product by fluorinating 1,1,3,3-tetrachloropropene and 1,3,3,3-tetrachloropropene. In this case, it is known that also 1-chloro-3,3,3-trifluoropropene is produced, which is a useful by-product.
In the fluorination reaction of 1,1,1,3,3-pentachloropropane as described here, a Lewis acid catalyst such as an antimony halogenide or a halogenochromium oxide is generally used as a catalyst.
However, although the aforementioned reaction in the liquid phase gives good selectivity in the HF solvent only in the early step, as the reaction proceeds the catalyst slowly deactivates, and so it does not give the desired product in a short time. To recover the reaction, superfluous work is required, such as additional supplementation of the catalyst and treatment to regenerate the catalyst.
Further as the reaction proceeds, in addition to the deactivation of the catalyst, organic substances that have high boiling points accumulate in the reactor and it has been observed that these significantly inhibit the reaction.
Also in the reaction in the gaseous phase described above, since the activity of the catalyst is significantly reduced by water contained in the material and the HF, the progress of the reaction i s significantly inhibited. Also a high reaction temperature and continuous contact time between the catalyst and the gas must be maintained to achieve the desired conversion rate. For these reasons, it is impossible to avoid increases in running costs.
The present invention was studied from these stated viewpoints with the following aims in fluorinating specific organic chlorides as materials, which are represented by 1,1,1,3,3-pentachloropropane, with HF in the presence of a catalyst: providing a continuously efficient manufacturing method for 1,1,1,3,3-pentafluoropropane and/or 1-chloro-3,3,3-trifluoropropene; simultaneously preventing deactivation of the catalyst; and preventing the reaction from being inhibited by the accumulation of organic substances with high boiling points.
A manufacturing method for 1,1,1,3,3-pentafluoropropane and/or 1-chloro-3,3,3-trifluoropropene by the present invention is characterized by using all dehydrated materials and HF in order to obtain the objective products by fluorinating one or more of the materials selected from 1,1,1,3,3-pentachloropropane, 1,1,3,3-tetrachloropropene and 1,3,3,3-tetrachloropropene with HF in the presence of a catalyst. One of the intended products, 1-chloro-3,3,3-trifluoropropene may be used as the starting material for another intended product, 1,1,1,3,3-pentafluoropropane.
As described above, if water is removed from the materials and the HF before submitting them to the reaction, phenomena such as deactivation of the catalyst and accumulation of organic substances with high boiling points can be effectively controlled as described later, and useful 1,1,1,3,3-pentafluoropropane and/or 1-chloro-3,3,3-trifluoropropene can be manufactured continuously and efficiently.
By intense investigations on factors causing the afore-mentioned deactivation of the catalyst, the present inventors could find that a primary factor in the deactivation of said catalysts was the water contained in said materials and HF, especially the presence of water in the materials, because of the reaction with the catalysts. In addition, water in said HF and materials chemically reacts with the materials themselves under the reaction condition of the fluorination to generate organic substances with high boiling points. These substances slowly accumulate in the reactor to significantly inhibit the fluorination reaction, obstructing the continuous production of the intended products.
Thus, for a continuous and smooth fluorination reaction of said materials, before submitting said materials and HF to the reaction, it is necessary to remove water as much as possible from them, preferably to remove it about completely or to achieve a substantially anhydrous state, if possible.
Water inevitably becomes mixed in the materials and HF during the processes of manufacture and handling, and removal of this water to a high level of a few ppm is difficult using conventional techniques.
The present inventors found, as the results of repeated trial-and-error experiments to precisely investigate methods of dehydration, that the most effective method is to apply highly adsorbable zeolite to said materials and to use a distillation method for the HF.
Industrial Application
According to the manufacturing method of the present invention, when fluorinating three of said materials, which are typically represented by 1,1,1,3,3-pentachloropropane, with HF in the presence of a catalyst, more than sufficient water can be removed before submitting them to the reaction, preventing unwanted phenomena such as the deactivation of the catalyst by the water and the accumulation of organic substances with high boiling points as described previously. Thus, industrially important 1,1,1,3,3-pentafluoropropane and/or 1-chloro-3,3,3-trifluoropropene can be manufactured continuously and efficiently in a smooth fluorination reaction.