The effect of K2HPO4 and Al2(SO4)3 modified MCM-41 on the dehydration of methyl lactate to acrylic acid

Abstract

In this paper, Al₂(SO₄)₃ and K₂HPO₄ modified MCM-41 were developed as catalysts for efficient conversion of methyl lactate (ML) to acrylic acid (AA) and methyl acrylate (MA). By changing the loading amount of the two salts and their ratio, the catalytic performance was optimized and the highest AA + MA yield of 73.6% was achieved over the 45 wt% K₂HPO₄ and Al₂(SO₄)₃ (6 : 4)/MCM-41 catalyst at 410 °C. The physicochemical properties of the catalysts were investigated by various techniques including XRD, BET, NH₃-TPD, CO₂-TPD, pyridine adsorption-FTIR and CO₂ adsorption-FTIR. The 45% loading sample showed the smallest acidic amounts and a moderate basicity amount, and the acidic–basicity ratio was thought to be crucial for the AA selectivity. Further decrease or increase in the ratio would cause a drop in AA selectivity. Carbon deposition was the main reason for catalyst deactivation. The catalyst could be fully regenerated by air treatment and behaved with good activity after 10 regenerations.