Catalytic conversion of sugarcane bagasse, rice husk and corncob in the presence of TiO2, ZrO2 and mixed-oxide TiO2-ZrO2 under hot compressed water (HCW) condition

The simultaneous hydrolysis/dehydration reaction of sugarcane bagasse, rice husk and corncob was studied under hot compressed water in the presence of TiO2, ZrO2 and TiO2-ZrO2 at 473-673 K. Among them, the reaction of corncob at 573 K in the presence of TiO2-ZrO2 produced the highest furfural and 5-hydroxymethylfurfural (HMF) yields (10.3% and 8.6%) with less by-products (i.e. glucose, fructose, xylose, and 1,6-anhydroglucose) selectivities. It was found that the catalyst preparation procedure and calcination temperature strongly affected its reactivity. Catalysts prepared by (co-) precipitation method gained higher reactivity than those prepared by sol-gel and physical mixing methods. The suitable calcination temperature for TiO2 and ZrO2 was at 773 K, whereas that for TiO2-ZrO2 was at 873 K; the XRD patterns revealed that different portions of phase formation were observed over catalysts with different calcination temperature. The portion of these phase formations affected the acidity-basicity of catalyst and thus the catalyst reactivity.