Modified versions of sulfated zirconia as catalysts for the conversion of xylose to furfural
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Catalysis Letters, Vol. 114, Nos. 3–4, April 2007 (Ó 2007) DOI: 10.1007/s10562-007-9052-6
Modified versions of sulfated zirconia as catalysts for the conversion of xylose to furfural Ana S. Dias, Se´rgio Lima, Martyn Pillinger, and Anabela A. Valente* Department of Chemistry, CICECO, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
Received 22 November 2006; accepted 16 January 2007
Conventional (per)sulfated bulk zirconia, mesoporous sulfated zirconia and (per)sulfated zirconia supported on an ordered mesoporous silica, with or without aluminium incorporation, were examined as acid catalysts for the dehydrocyclisation of xylose into furfural. Furfural yields of up to 50% could be achieved at >90% conversion with the modified zirconia catalysts, which is better than that achievable with H2SO4 (using approximately the same equivalent amount of sulfur.) KEY WORDS: xylose; furfural; dehydration; acid catalysis; sulfated zirconia; mesoporous materials; MCM-41.
1. Introduction Biomass, or plant matter, is a renewable energy source that is one of the most important alternatives to crude oil [1–3]. It is made up of four major components: cellulose, hemicellulose, lignin and starch. Bio sugars obtained from these components by hydrolysis are the raw materials to make chemicals, consumer and industrial products, and energy from biomass. The two primary sugars are glucose, a 6-carbon sugar made from the cellulose portion of biomass, and xylose, a 5-carbon sugar made from the hemicellulose portion. Glucose may be processed into a wide variety of products including ethanol, sorbitol, mannitol, gluconic acid and 5-hydroxymethylfurfural. Xylose derivatives include ethanol, xylitol, furfural, furfuryl alcohol and furan. Furfural is of high commercial interest because it can be used for the production of a wide range of important non-petroleum-derived chemicals [4–6]. It is produced by the acid-catalysed dehydration of xylose. Presently, several industrial processes for furfural production use H2SO4 as the catalyst under homogeneous conditions. Due to the hazardous properties of liquid acids such as H2SO4 and the well known drawbacks of homogeneous catalytic processes, there has been a great effort to replace toxic liquid acid catalysts by more environmentally friendly solid acid catalysts [7–9]. The most widely studied solid acids based on inorganic oxides are zeolites and zeotypes, heteropolyacids, metal phosphates and sulfated metal oxides [7–10]. Some of these materials have been studied as catalysts for the transformation of carbohydrates. Moreau and co-workers found that microporous zeolites such as *To whom correspondence should be addressed. E-mail: [email protected]
mordenites and faujasites catalyse the conversion of saccharides into furan derivatives with high selectivity (but only for conversions up to about 30%) [11]. Heterogeneous catalysts based on cubic zirconium pyrophosphates, c-titanium phosphate and vanadyl phosphate exhibit good performances, in terms of selectivity and activity, for the d
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