Synthesis of 5-hydroxymethylfurfural from fructose catalyzed by phosphotungstic acid

Iron(III)‐modified tungstophosphoric acid supported on silica‐pillared montmorillonite as catalysts for fructose conversion to methyl levulinate

“…The results showed that ML yield through 4‐HPWFe‐MMTSi was higher than that from HPW‐MMTSi, indicating that the iron substituted HPW supported on MMTSi was more active compared with parent HPW supported on MMTSi. This might be due to the generation of Lewis acid sites (Fe 3+ ions), which was in line with previous research that the combination of Brønsted acid with Lewis acid could effectively promote the alcoholysis of fructose to levulinate esters . Combining the physiochemical properties of the catalysts with catalytic results, it could be deduced that the number of accessible active acid sites, the acid types and the accessibility of the organic reactants to the active sites markedly effected the overall activity resulting from the relationship of catalyst properties and catalytic results.…”

“…For sample encapsulating HPWFe, namely, HPWFe‐MMTSi samples, the strong acid center shifted to around 520°C and weak acid center barely changed. At the same time, the strong acid intensity and the total acid amount was significantly enhanced, resulting from the fact that HPW is a strong acid and has a strong acid center at around 550°C . The reason that the strong acid center of HPW decreased to around 520°C might be attributed to the interaction between partial protons of HPW and Si‐OH of MMTSi, which could obviously improve the stability of catalysts but also make some strong acid sites change to weak acid sites.…”

“…Heteropoly acids (HPAs), owing to their strong acidity, especially those with the Keggin structure (such as H 3 PW 12 O 40, HPW) have shown excellent catalytic performance in both heterogeneous and homogeneous catalytic reactions . HPW as a Brønsted acid has even higher acidity than H 2 SO 4 but HPW utilization is limited due to its low surface area, poor thermal stability, and so on . According to several reports, even if HPW was loaded in porous materials such as alumina, active carbon, titania, molecular sieve and ordered mesoporous silica, large HPW loss from the supports appeared in polar reaction media .…”

Synthesis of 5‐hydroxymethylfurfural from fructose and inulin catalyzed by magnetically‐recoverable Fe3O4@SiO2@TiO2–HPW nanoparticles

“…Thus, researchers have used organic solvents for HMF production, achieving high HMF yields from fructose in dimethyl sulfoxide (DMSO) using various catalysts . One advantage of using DMSO is that the conformation of fructose is in the form of furanose to a greater extent than in water, and this conformation favors the formation of HMF . In addition, the solvating ability of DMSO may stabilize positively charged intermediates of the formation of HMF, and therefore may reduce the formation of byproducts .…”

“…Currently, HPW is emerging as a popular catalyst for the synthesis of HMF due to its high acidity and stability . Since HPW is soluble in water and many organic solvents, it must be first immobilized on an insoluble support, such as SiO 2 , titanium dioxide (TiO 2 ), zeolite and/or active carbon, in order to make heterogeneous HPW catalysts . Some studies have shown that supported HPW catalysts might have similar or even higher activities, compared to bulk HPW, for catalyzing dehydration reactions .…”