Post-synthetically modified hierarchical Mordenite and ZSM-5 zeolite and their catalytic performances in benzylation of acetic acid to benzyl acetate
Authors :- Koshti H.; Bandyopadhyay M.; Bandyopadhyay R.
Publication :- Journal of Materials Science, 58, 11914–11936 (2023).
Micro-mesoporous Mordenite and ZSM-5 zeolites with tailor-made pore structures are produced using post-synthetic dealumination and desilication treatment. Inductively coupled plasma–optical emission spectroscopy (ICP-OES) analysis showed that post-synthetic acid and base treatment resulting into tuning the Si/Al ratio, thereby increasing the acidity of sample. Acidic characteristics of the samples were confirmed using pyridine FTIR and NH3− TPD. Acetic acid was converted to benzyl acetate by reacting with benzyl alcohol, over both hierarchical samples and their parent counterparts. Acid-modified zeolites were compared with those of base-modified one and also with the unaltered parent materials. Mesoporous pore volume of all zeolites significantly increased due to base alteration compared to the acid alteration and the parent samples. In other studies, the micro-/meso-H-ZSM-5 catalyst showed considerable potential for benzylation, exhibiting an impressive AA conversion rate of 94% with 95% benzyl acetate selectivity. In comparison, in the current study, an alternative catalyst consisting of base-altered Mordenite was found to surpass these results, achieving a 100% AA conversion and 98.2% selectivity towards benzyl acetate. Optimization of the process was investigated by altering time, temperature and catalyst amount. Analysis of reaction products was validated by GC and GC–MS. The reaction rate constants exhibited a positive correlation with increasing reaction temperature, as per the principles of first-order reaction kinetics (R2 > 0.94); and activation energy for AA benzylation over Mor-0.1 M NaOH was found to be 13.87 kJ mol−1, which is significantly lower than the previously reported value.