Production of 5-hydroxymethylfurfural (HMF) from cellulose catalyzed by solid acids and metal chlorides was studied in the 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) under microwave irradiation. Among the applied catalysts, the use of CrCl(3)/LiCl resulted in the highest yield of HMF. The effects of catalyst dosage (mole ratio of catalyst to glucose units in the feedstock) and reaction temperature on HMF yields were investigated to obtain optimal process conditions. With the 1:1 mol ratio of catalyst to glucose unit, the HMF yield reached 62.3% at 160 degrees C for 10 min. Untreated wheat straw was also investigated as feedstock to produce HMF for the practical use of raw biomass, in which the HMF yield was comparable to that from pure cellulose. After the extraction of HMF, [BMIM]Cl and CrCl(3)/LiCl could be reused and exhibited no activity loss after three successive runs. (C) 2010 Elsevier Ltd. All rights reserved.