La-H-zeolites: efficient catalysts for acetic acid ketonic decarboxylation and esterification

BACKGROUND: Cyclohexyl acetate and acetone are used as environmentally friendly solvents, while isobutene acts as an intermediate in the production of methacrolein, ethers, plastics and pharmaceuticals. Two La-zeolite catalysts have been studied for converting acetic acid to cyclohexyl acetate, acetone and isobutene. RESULTS: La-based zeolites were synthesized from Na-nFAU zeolites by ammonium ion exchange, followed by lanthanum ion exchange. The influence of Brønsted and Lewis acid sites on the activity in acetic acid esterification with cyclohexanol and in ketonic decarboxylation of acetic acid was studied. Fourier transform infrared (FTIR) spectroscopy of pyridine adsorption has been used for acid site evaluation. The presence of Brønsted acid sites on the surface leads to an increase in cyclohexyl acetate and acetone selectivity, while the presence of Lewis acidity favors further transformation of acetone in isobutene. CONCLUSION: The sample with the highest Brønsted acidity and the highest content in both La and Al, namely La-H-13X, showed the highest activity for both acetic acid esterification and ketonic decarboxylation – an indication that Brønsted acidity is very important for the studied reactions.