Acid-base nanocatalysts for hydrolysis of biomass components in the aquatic environment

Abstract

Acid-base nanocatalysts based on phosphorus-tungsten and phosphorus-molybdenum heteropolyacids with grafted α-amino acids for the process of acid hydrolysis of biomass in aqueous medium have been synthesized. Their physicochemical, structural-adsorption characteristics and catalytic properties during the hydrolysis of biomass components under hydrothermal conditions have been studied. Using IR spectroscopy, the presence of heteropolyacids and amino acids in the structure of the created hybrid materials has been established. By method of X-ray fluorescent energy dispersive analysis, the presence of heteropolyacids in the structure of the obtained acid-base nanocatalysts has been confirmed. The structural adsorption characteristics of the synthesized catalysts have been determined by adsorption of nitrogen vapors at liquid nitrogen temperature. The specific surface area of samples based on phosphorus-tungsten acid made up 600 m2/g, and for samples with phosphorus-molybdenum heteropolyacid – 200 m2/g. The adsorptiondesorption isotherms of nitrogen of the synthesized samples correspond to materials with mesoporous structure with a pore size of 5–6 nm. The synthesized acid-base nanocatalysts have been tested using the example of fructose hydrolysis. It has been shown that grafting of α-amino acids to heteropolyacids catalysts influences the yield of the target product – 5-hydroxymethyl furfural. The best yield of 5-hydroxymethyl furfural (28.3 %) has been obtained for catalyst H3PW12O40/lysine. In addition, when using catalysts with phosphorus-molybdenum heteropolyacid, a large amount of reaction by-products is formed.