A novel and environmentally friendly NASICON-type material: Efficient catalyst for condensation of formaldehyde and acetic acid to acrylic acid and methyl acrylate

Abstract

The development of environmentally friendly and efficient catalysts for the production of essential chemicals has always been a desirable goal for technology in the chemical industry. In this paper, we fabricated a kind of sodium (Na) super ionic conductor (NASICON)-type materials (H1-xTi2(PO4)3-x(SO4)x) with different Ti/P ratios through tuning titanium content in synthetic mother liquor, and applied them to the aldol condensation reaction of acetic acid (HAc) and formaldehyde (FA) to acrylic acid (AA) and methyl acrylate (MA), which has never been not reported in previous researches. More importantly, these novel catalysts have showed their tremendous potential at the efficiency of AA + MA production, and over an optimized catalyst of NSC-Ti/P-0.53, the AA + MA selectivity being 71% (HAc input-based) was achieved at 360 ℃ when the reactant with FA/HAc molar ratio of 5:1 was fed; whereas, a highest space–time-yield (STY) of target products (∼37.2 μmol·g−1·min−1) was obtained with the FA/HAc molar ratio of 1:2.5, which is comparable to the best result reported previously. The detailed analysis of characterizations demonstrated that the change in the Ti/P ratio in the series NASICON catalysts led to the variation in the phase composition, the textural properties, surface titanium oxidation state, etc. thereby tuning the surface acid-base property, which is quite important for the present condensation reaction. More amounts of acidic sites and basic sites as well as their moderate distribution were proved to exert the promotional effects on the formation of AA and MA.