Lanthanum phosphate: an efficient catalyst for acrylic acid production through lactic acid dehydration

Abstract

In this work, biomass-based platform molecule lactic acid conversion to acrylic acid has been studied. A series of lanthanum phosphate (LaP) catalysts prepared by varying the lanthanum to phosphorus (La/P) mole ratio (i.e., 0.2, 0.35, 0.5, 1.0, and 2.0) and also prepared at different calcination temperatures (i.e., 400, 500, 600, and 800 °C) were investigated. The catalysts were characterized by using different techniques and tested in the dehydration of lactic acid (LA) to acrylic acid (AA) production. All the synthesized catalysts were characterized to analyze the physicochemical properties such as degree of crystallinity, total surface acidity, specific surface area, and morphology. The La/P mole ratio was found to be significant in designing the optimized catalytic system. The NH3-TPD results imply that all the catalysts exhibited varied amount of total acidity with phosphate loadings, which are mostly weak acid sites. The weak acid sites which are mainly Lewis acidity type played an important role in producing AA selectively and efficiently from the LA conversion. The most optimized reaction conditions were determined to obtain the highest LA conversion, selectivity, and AA yield. The catalyst with an La/P mole ratio of 0.35 and calcined at 500 °C exhibited the best performance with complete LA conversion, AA selectivity of ~ 74%, and a maximum yield of AA of ~ 74%. Furthermore, the LaP(0.35)[500] catalyst was successfully tested at three different time on streams and found to be stable.