Evolution of thE ChEmiCal industry and importanCE of multiphasE rEaCtors

Multiphase reactors have been at the cutting edge of technology development in the chemical industry. This premier status of multiphase reactors can be best appreciated in the context of the evolution of the chemical industry itself. It is therefore appropriate to discuss specific aspects relating to the growth and progress of the chemical process industries. This introduction starts with the evolution of the modern chemical industry and discusses the importance of green and sustainable methods and the inevitability of catalysts and multiphase catalytic reactors for carrying out highly efficient catalytic reactions. The chemical process industries took a long and arduous road of development from modest beginnings through processes such as brewing and distillation; manufacture of soap, sugar, and paper, etc. in small-scale units. Most of the development was based on serendipity and empiricism rather than application of sound chemical engineering principles. In view of the poorly defined methodology, the advancement was slow. The seventeenth and eighteenth centuries witnessed practically no scientific progress that could bring about significant improvements in chemical engineering principles required for rational design. In the early 1920s, a need was felt to have a unified approach for different disciplines of chemical engineering, and thus, the concept of unit operations (Walker et al. 1923) was introduced. Subsequently, the concept of unit processes (Groggins 1958), which allowed treatment of individual reaction types on a unified basis, was