Dehydration of xylose into furfural over micro-mesoporous sulfonic acid catalysts

Surfactant-templated micro-mesoporous silicas possessing sulfonic acid groups (SAGs) have been prepared, characterized, and tested as catalysts in the dehydration Of D-xylose to furfural. All of the materials possessed catalytic activity. In general, selectivity to furfural was lower for a poorly ordered microporous hybrid material, prepared via the co-condensation of (3-mereaptopropyl)trimetboxysilane with bis(trimethoxysilylethyl)benzene, than for mesoporous MCM-41 silica anchored with SAGs via postsynthesis modification. The MCM-41 material with the highest loading of SAGs (0.7 meq g(-1)) displayed fairly high selectivity for furfural (ca. 82% in DMSO or water/toluene mixture) at high xylose conversion (>90% within 24 h, at 140 degreesC). Xylose conversion increased significantly with reaction temperature. At 170 degreesC, more than 85% conversion was achieved within 4 It with any of the sulfonic acid-functionalized catalysts. Furfural yield tended to increase with temperature. Xylose conversion increased with increasing amount of catalyst, and for a xylose/MCM-41-SO3H ratio of 0.5, 76% conversion was achieved within 4 It, at 140 degreesC. Catalyst deactivation was observed after long residence times, possibly because of the interaction of reaction products with the acid sites, leading to surface loading. (C) 2004 Elsevier Inc. All rights reserved.