HETEROGENEOUS PROCESSES REPLACING HOMOGENEOUS CATALYSIS

The past fifteen years have seen evidence of great interest in homogeneous catalysis, particularly by transition metal complexes in solution predictions were made that many heterogeneous processes would be replaced by more efficient homogeneous ones. There are two motives in these changes—first, intellectual curiosity and the belief that we can define the active center with... 

Examples here are Friedel-Crafts alkylations and acylations, in which the zeolite catalyst replaces the homogeneous Lewis acid. Zeolite catalysts can also be used in place of mineral acids and organic acids. However, these catalyst substitutions also involve changing the process from homogeneous to heterogeneous catalysis. 

Base catalysis is of major importance in the production of fine chemicals but the number of available solid base catalysts is limited [1-3]. The research of solid bases for application in processes for the fine chemical industry is intensifying due to higher demands for limiting the waste stream. Advantages of solid bases, such as reusability, favor the replacement of homogeneous bases with their heterogeneous counterparts [4-7] and may stimulate the development... 

Since the 1950s, many processes based on homogeneous reactions have been introduced, either to replace heterogeneous catalytic reactions with routes offering milder and less expensive process conditions, or to make entirely new products. Fine chemicals in the pharmaceutical industry form an outstanding example of the latter. Nevertheless, heterogeneous catalysis also expanded immensely. 

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