| Abstract |
The H-MCM-22 zeolite possessing an MWW (medium-pore) framework and its delaminated counterpart. ITQ-2, with enhanced external surface area, are effective and recyclable solid acid catalysts in the batch-wise, aqueous-phase dehydration of xylose, at 170 degrees C. Up to 71\% furfural (Fur) yield is reached at 98\% conversion using a biphasic aqueous-organic solvent system (for the simultaneous extraction of Fur); using solely water as the solvent gives up to 54\% Fur yield at 97\% conversion. Sulfuric acid, used in an approximately equivalent amount to the total acid site concentration of the solid acids, gave 55\% Fur yield at 93\% conversion. Decreasing the Si/Al ratio of H-MCM-22 zeolite improves the acid properties and consequently the catalytic activity, without affecting significantly the Fur selectivity. While the delamination process considerably enhanced the external surface area of ITQ-2 in comparison to H-MCM-22, it caused modifications in the acid properties, leaving the two prepared materials with the same Si/Al atomic ratio of 24, on a comparable footing in terms of catalytic performance in the studied catalytic reaction. Nevertheless, these solid acid catalysts are fairly stable (similar Fur yields are reached in recycling runs; no structural modifications and no leaching phenomena were detected). (C) 2012 Elsevier B.V. All rights reserved. |
