โ Scribed by Kozo Tanabe
No coin nor oath required. For personal study only.
Many chemical reactions are known to be catalyzed by acids and bases. The use of liquid acid and base catalysts, however, is responsible for the following problems in industrial processes. a. Corrosion of the reactor or reaction apparatus b. Difficulty in separating the catalyst from the reaction mixture c. Difficulty of repeated use of catalyst d. High cost of treating the catalyst to make its disposal environmentally safe e. Low activity and selectivity in some reactions
In order to overcome the difficulties, various kinds of solid acid and base catalysts such as metal oxides, complex oxides, zeolites, heteropoly acids, interlayer compounds, metal sulfates, metal phosphates, solid superacids and superbases, etc. have been applied to diversified reactions [ 1,2]. Some industrial processes which have been successfully achieved by the use of solid acid and base catalysts are the production of: t-butyl alcohol from i-butene with heteropoly acid, dimethylamine from methanol and ammonia with zeolite, ethyleneimine from monoethanolamine with cesium phosphate, ethylidene norbomene from vinyl norbomene with solid superbases, alkenes from methanol with zeolite or molecular sieve, methyl t-butyl ether from methanol and isobutene with acidic resin, xylene and benzene from toluene with ZSM-5, and of the other 35 chemicals [3-51. However, there are many other important processes which still use undesirable liquid acid and base catalysts. For example, the Beckmann rearrangement (cyclohexanone oxime l -caprolactam), esterification of long carbon chain fatty acids, alkylation of isobutane with alkenes, oligomerization of cr-alkenes, alkylation of benzene with ethylene or propene, etc. Even in the industrialized processes mentioned above, catalytic activity, selectivity, and life are not necessarily satisfactory.
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