One-pot catalytic conversion of xylose to furfural on mesoporous niobium phosphate

Abstract

The conversion of xylose to furfural normally involves two steps: the isomerization of xylose to xylulose catalyzed by an enzyme, a base or a Lewis acid, followed by the acid-catalyzed dehydration of xylulose to furfural. To allow a more efficient single-step conversion, a new water-tolerant solid acid catalyst, mesoporous niobium phosphate was synthesized. This synthesis was performed using a soft template approach, with cetyltriethylammonium bromide (CTAB) as the template. The structure and properties of the catalyst thus synthesized were investigated by X-ray diffraction (XRD), N 2 sorption, transmission electron microscopy (TEM), temperature-programmed desorption of NH 3 (NH 3-TPD), and pyridine sorption FTIR (Py-FTIR). These studies determined that the niobium phosphate not only had a large surface area (>200 m 2·g -1) and narrow pore size distribution (3.5 nm), but also had relatively strong Lewis and Bro/ nsted acidity. This catalyst was found to be capable of producing furfural via a simple one-pot process, including the isomerization of xylose to xylulose and subsequent dehydration. The influence of several variables including temperature, mass ratio of xylose/catalyst, and reaction time on the extent of xylose conversion and furfural yield were studied. Under optimal conditions, the yield of furfural in aqueous solution reached 49.8% with 96.5% xylose conversion. It was further determined that both the yield and the separation of furfural could be improved by employing a methyl isobutyl ketone (MIBK)/water (volume ratio 7:3) biphase containing NaCl in the aqueous phase, resulting in a 68.4% yield. © Editorial office of Acta Physico-Chimica Sinica.