Highly selective production of renewable methyl acrylate via aldol condensation over Cu modified nitrogen-containing Beta zeolites

Abstract

Highly selective synthesis of renewable methyl acrylate from bio-sourced formaldehyde and methyl acetate through one-step aldol condensation was successfully realized on Cu-modified nitrogen-containing Beta (NBeta) catalysts. Silicon-29 magic angle spinning nuclear magnetic resonance (29Si MAS NMR), Fourier transform infrared spectroscopy (FT-IR), temperature-programmed desorption of ammonia, temperature-programmed desorption of carbon dioxide, and element analysis indicate that nitridation weakens the acid strength, reduces the number of acidic sites and introduces basic sites through the formation of Si−N bond on Beta zeolites, thereby promoting methyl acrylate selectivity and reducing the coke formation. Adding Cu into NBeta further finely tunes the basicity and acidity balance and thus inhibits the by-product acetone. High methyl acrylate selectivity of 95% and formaldehyde conversion of 99% were achieved over Cu/NBeta catalyst under optimized conditions. The coke content decreases remarkably from 28% on H-form Beta (HBeta) zeolites to 17% on NBeta zeolites doped with Cu due to its appropriate basicity/acidity. Cu/NBeta has good regeneration capability, and the weakening of Si-N species may account for the decline of catalytic performance after successive regeneration. The catalytic performance was restored when the regenerated catalyst was nitridated again.