Furfural acetalization over Keggin heteropolyacid salts at room temperature: effect of cesium doping

Furfural is a platform-molecule of biorefinery highly valuable due to numerous applications in different industries. Furfural acetals are fuel bioadditives, ingredients of fragrances, solvents, paints, and fine chemicals. The condensation of furfural with alcohols requires the presence of an acid catalyst, which should be desirably active, selective, and recyclable. In this work, Keggin heteropolyacids (i.e., HPAs) were converted to solid salts after the partial exchanges of their protons by Cesium ions. This modification makes HPAs insoluble in polar solvents, allowing that they can be easily recycled and reused. The effect of Cesium doping in different HPAs was assessed (i.e., H3PW12O40, H3PMo12O40, H4SiW12O40). Analysis of NH3-TPD (i.e., Ammonia temperature-programmed desorption) allowed to assessment the effect of protons exchange by Cesium on the strength of acidity of catalysts. Among the investigated HPA salts, Cs2.5H0.5PW12O40 was the most active and selective catalyst toward alkyl furfural acetals. An almost total acetalization of furfural with methyl alcohol was achieved after 1 h reaction using 0.0150 mol% of Cs2.5H0.5PW12O40 catalyst. The influences of main reaction parameters were evaluated such as catalyst load, temperature, and sort of alcohol. [GRAPHICS] .

Automated summary

Furfural is an important platform molecule in biorefinery with various applications across different industries. The conversion of Keggin heteropolyacids (HPAs) to solid salts by Cesium ions allows for insolubility in polar solvents, enabling easy recycling. Among the HPAs studied, Cs2.5H0.5PW12O40 showed the highest activity and selectivity towards alkyl furfural acetals.