Fructose dehydration to 5‐HMF over three sulfonated carbons: effect of different pore structures

Abstract

BACKGROUND To invesigate the effect of pore structure on catalysis behavior, three sulfonated carbons with hierarchically ordered pores (SCHOP), mesopores (SMC), or micropores (SAC) were compared in conversion of fructose with 5‐hydroxymethyl furfural (5‐HMF). Fructose and 5‐HMF adsorption by three carbons with different pore structures were also measured. Kinetic modeling was employed to correlate the reaction and the adsorption data. RESULTS SEM characterization showed that SCHOP has hierarchical ordered macropores (about 220 nm in pore diameter) and mesopores (4.81 nm), whereas N2 adsorption desorption, EDS and –SO3H group determination suggested both its specific surface area and –SO3H group content were close to those of SMC but quite distinct in comparison with SAC. The fitted active energies of fructose dehydration over SCHOP, SMC and SAC by a pseudo‐first‐order kinetic model were 84.54, 62.88, and 61.42 kJ mol−1, respectively. CONCLUSION It was found that pore structure has a significant effect on catalytic activity and 5‐HMF selectivity. SCHOP was a highly efficient catalyst for fructose dehydration to 5‐HMF. Adsorption capacity measurement confirmed SCHOP favored the internal diffusion of both fructose and 5‐HMF due to its hierarchical ordered porous structure, and possessed more effective specific area for fructose but less for 5‐HMF. In the presence of SCHOP the rate‐determining step was chemical reaction, whereas in the case of SMC or SAC the effects of molecular internal diffusion were not negligible. As a result, SCHOP was superior to both SMC and SAC for fructose conversion and 5‐HMF selectivity. © 2016 Society of Chemical Industry

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