A layered transition metal oxide, HNbMoO6 is known to exhibit remarkable performances for a variety of acid-catalyzed reactions, and possess strong Br�nsted acid sites comparable to the strongest acid sites of H-ZSM5. Here, we examined a mechanochemical depolymerization of crystalline cellulose by using ball milling in the presence of layered HNbMoO6 as a potential solid acid additive.Ball-milling in the presence of the oxide successfully afforded 72% yield of water-soluble sugars from Avicel cellulose whereas that in the absence of the catalyst gave negligible yield (1%). HNbMoO6 exhibited the highest sugar yields among layered solid acids tested such as acid-treated kaolinite and montmorillonite. The product distribution and reaction mechanism were different from those of conventional liquid-phase hydrolysis. The resulting water-soluble sugars include cellooligomers (C1-C6) and anhydrosugars. The yields of water-soluble sugars increased with increasing reaction time, rotation speed and number of balls, keeping on the product distribution. This suggests that most of sugars were formed not via successive degradation of oligosaccharides but via direct depolymerization of cellulose by mechanocatalysis.The yields of soluble sugars were largely dependent on the amount of water added. The addition of a slight amount of water was effective to improve the yield of soluble sugars. In contrast, the addition of excess amount of water diminished product yields, which is attributable to the insufficient contact between particles.

Decomposition of crystalline cellulose by ball-milling in the presence of layered niobium molybdate solid acid

248th National Meeting (2014)

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