1,1,3,3-Tetramethylguanidinium hydrogen sulfate (TMG center dot HSO4) catalyzed conversion of xylose to furfural in water enriched with carbon dioxide at high temperature is described. The presence of carbon dioxide exhibited significant enhancement in the reaction rates and produced product yield more than 90%. The probable reasons for this rate enhancement are the following: (i) carbon dioxide might be reducing the viscosity of the reaction medium for better mass transfer and therefore enhancing the reaction; (ii) the reaction between carbon dioxide and water at higher temperature produces carbonic acid, which subsequently dissociates to increase the hydronium ion concentration and in turn the acidity of the medium.