Synthesis of 5-hydroxymethylfurfural from fructose catalyzed by phosphotungstic acid

Article abstract of DOI:10.1016/j.cattod.2016.02.018

The dehydration of fructose to 5-hydroxymethylfurfural (HMF) is a way to produce a very versatile intermediate of the green chemistry. Heteropolyacid compounds are acid catalysts with singular properties (strong acidity and well-defined structure). This paper aims to analyze the activity of phosphotungstic acid (HPW) and Cs-exchanged phosphotungstic acid (HCsPW) in HMF synthesis, as well as HPW supported on MCM-41. The reactions were conducted in a batch reactor, using dimethyl sulfoxide (DMSO) as solvent, for 2 h. The initial tests indicated that HMF is formed in the absence of catalyst, but in presence of the catalysts, the maximum yield to HMF is higher and achieved in less time. The HPW showed promising results, reaching 100% of fructose conversion and 92% of HMF yield, after 30 min of reaction at 120 °C, with a catalyst:fructose mass ratio of 1:10. However, this heteropolyacid is soluble in DMSO. Besides, the Cs-exchanged HPW resulted in a reduction in HMF yield, because of the reduction in solid acidity. HPW supported in MCM-41 (HPW/MCM) showed to be a good solid acid catalyst for the production of HMF from fructose; moreover, it can be recovered and reused. The variables evaluated for this catalyst were the reaction temperature (100, 120 and 140 °C) and the catalyst:fructose mass ratio (1:10; 1:30 and 1:50). The best results obtained for HPW/MCM were 100% of fructose conversion and 80% of HMF yield in 60 min, at 120 °C.