Reactivity of mesoporous ZSM-5 zeolite towards Friedel-Crafts acylation of anisole and propionic anhydride

Abstract

ZSM-5 zeolite is known as solid acid catalyst for many organic reactions. ZSM-5 zeolite is a microporous aluminosilicate catalyst which is not suitable for reactionsinvolving large molecules. Therefore, ZSM-5 with mesopores size needs to be synthesized. In this study, mesoporous ZSM-5 were synthesized in the presence and absence of sucrose as mesotemplate. As comparison, microporous ZSM-5 was also synthesized using standard method. The samples were characterized using XRD, FTIR and nitrogen adsorption analysis. Results from XRD and FTIR of sample with sucrose template showed the formation of crystalline ZSM-5 structure while sample without sucrose showed amorphous phase. Nitrogen adsorption analysis showed that the synthesized mesoporous ZSM-5 has mesoporous structure with type IV isotherm which the average pore is in the range of 4-6 nm and the BET surface area was 400 m2/g. The reactivity of all synthesized samples was tested in Friedel-Craft acylation of anisole and propionic anhydride to produce the main product, p-methoxypropiophenone and the side product, propionic acid. Results proved that synthesized mesoporous ZSM-5 with sucrose is the best catalyst in term of conversion and selectivity with 73.66% and 80.45% respectively as compared to sample without sucrose has comparable selectivity, 75.11% but low conversion, 22.63%. In contrast, microporous ZSM-5 has comparable conversion, 80.81% but low selectivity, 55.53%. This indicates that acidity and mesoporosity are responsible enhanced reactivity of ZSM-5 catalyst for Friedel-Crafts reaction involving large molecule.