Studies On Preparation Of SnO_x/γ-Al₂O₃Catalyst And Its Catalytic Performance For Biomass Degradation

Biomass is the most abundant renewable resources in the world, and it has a potential ability to become an alternative to fossil resources for sustainable production of chemicals and fuels for preventing global warming by decreasing atmospheric CO2generated from the consumption of fossil fuels.A series of SnOx/y-Al2O3catalysts with different Sn loading were prepared by impregnation precipitation method. The effects of different Sn loading in the SnOx/y-Al2O3catalysts on the catalyst activity and product distribution in the alcoholysis reaction of microcrystalline cellulose were investigated. It is found that the conversion of microcrystalline cellulose and the yield of methyl lactate are increased with the Sn loading.82%of microcrystalline cellulose conversion with28.1%of methyl lactate yield could be obtained at240℃for10hours over the SnOx/y-Al2O3catalyst with6.75wt%of the Sn loading. The catalyst active sites characterized by X-ray photoelectron spectroscopy (XPS) were SnO or SnO2, The surface acidity of the catalysts were characterized by pyridine adsorption infrared spectroscopy (Py-IR). Strong Bronsted acid sites at the surface of the catalysts are beneficial to make microcrystalline cellulose convert to methyl levulinate. while Lewis acid sites are advantageous for the generation of methyl lactate. Besides, the effects of reaction temperature%the content of water and cocatalyst WC on catalytic efficiency were also studied.The optimal catalyst was applied to catalyzed degradation of different biomass materials. It turned out that methyl glucoside yield reached53.78%and methyl lactate yield3.74%at180℃for10hours when potato starch was used as material. Under the same reation conditions,16.44%、15.92%and16.96%%of methyl glucoside yield obtained from sucrose、glucose and fructose while the yield of methyl lactate reached11.64%、16.33%and8.91%respectively. The content of methyl glucoside was0.57g/g from the root of kudzu vine in which starch is the primary component. It indicates that the optimal temperature to produce methyl glucoside is180℃, the yield of methyl glucoside and the conversion of materials will decrease with the reduction of temperature, the methyl glucoside will decreases while the methyl lactate yield increases as the temperature raised. There was no methyl glucoside formed when the temperature reached240℃while most methyl lactate generated. High temperature is advantageous for the generation of methyl lactate. Similar results were obtained when SnOx/y-Al2O3was used to catalyze the degradation of other cellulose containing materials such as cabo peduncle powder^liquorice residue、sugar cane residue and straw stalk. However the catalytic activity was low because the structure of cellulose was robust, and the content of cellulose in these biomass materials was low.