Cellulose samples with different crystallinities (33-85%) were prepared by treating a commercial cellulose (crystalline, 85%) with phosphoric acid under different conditions. Supported Fe, Co, Ni, Pd, Pt, Rh, Ru, Ir, Ag, and Au catalysts were examined for the conversion of cellulose with a crystallinity of 33% in water medium in the presence of hydrogen, and Ru was found to be the most effective catalyst for the formation of sorbitol. We demonstrated that carbon nanotubes (CNTs) were the most efficient support of Ru for cellulose conversion, and the mean size of Ru nanoparticles over CNT was similar to 8.8 nm. NH3-TPD and H-2-TPD characterizations suggest that plenty of acid sites and unique hydrogen species over the Ru/CNT are important for sorbitol formation through hydrolysis and hydrogenation of cellulose. A 40% yield of hexitols (including 36% of sorbitol) could be achieved over the Ru/CNT catalyst for the conversion of the commercial cellulose (crystalline, 85%), and this yield was the highest one reported to date for the direct conversion of cellulose into sugar alcohols.
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