Study of modified zeolites as heterogeneous catalysts for synthesis of petrochemicals and other organic compounds

Abstract

The thesis thoroughly covers the esterification of glycerol and levulinic acid, transesterification of glycerol, and alkylation of indole. Esterification, transesterification, and alkylation of low-valued chemicals were done so as to convert these to industrially important products like monoacetin, diacetin, glycerol carbonate, levulinate ester, and indole derivatives etc. Various homogeneous and heterogeneous catalysts such as HZSM-5, USY, Beta, and ammonium form of mordenite zeolites were used in the esterification, transesterification, and alkylation reactions. A detailed description of the catalyst such as its composition, structure, and properties has been discussed. In order to enhance the catalyst activity and reactivity towards the desired reaction, zeolites were further altered with various metals and functional groups. In order to understand, the influences of loading on the catalytic performance of the zeolites, yield, and selectivity of the product in specific reactions, characterization of catalysts was done by EDS, XRD, FE-sSEM, HRTEM, XPS, DLS, BET, and TPD. The reactant conversion depends on the activity of the catalyst, catalyst loading, reactant mole ratio, and reaction temperature. The outlined mechanisms of different reactions showed that the catalyst pore size and the type of pore as well as the feed composition of binary mixtures play important roles in the formation of the desired product. The activity of the zeolite also depends on the type of ions exchanged with the Na+ and H+ ions present in the framework of the zeolite. Besides evaluating the catalytic performance, the kinetic parameters of the reactions were also evaluated. The activation energy for the transesterification reaction was found to be 34.60 kJ/mol. The activation energy for the esterification reaction of glycerol with acetic was found to be 63.72 kJ/mol and for levulinic acid and ethanol esterification, it came out to be 19.57 kJ/mol. In the esterification of glycerol, 98.32% conversion of glycerol was obtained at optimize