Cu-Ce/γ-Al_2O_3对硬脂酸催化水热脱氧产生烷烃的效果
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摘要
利用等体积浸渍法制备Cu-Ce/γ-Al_2O_3催化剂,并在无H_2存在的条件下对硬脂酸进行催化水热液化。对催化剂进行BET比表面积分析和X射线衍射(XRD)分析可知,Cu-Ce/γ-Al_2O_3催化剂中存在CuO和CeO_2两种晶型,在300℃条件下水热反应12 h后具有更好的热稳定性。通过对硬脂酸进行水热液化实验和对生物油进行气相色谱-质谱(GC-MS)分析发现,加入Cu-Ce/γ-Al_2O_3催化剂能够获得最高的硬脂酸转化率(94.71%)和总烃产率(81.41%),水热液化脱氧效果最好。分析正烷烃的产率,结果发现硬脂酸在高温水热条件下主要发生脱羧反应。Cu-Ce/γ-Al_2O_3催化剂的加入能够同时促进反应过程中脱羧反应、加氢脱氧反应和裂化反应。此外,Cu-Ce/γ-Al_2O_3还能够促进羰基基团的脱除,有效减少产物中的醛和酮类物质。
In order to improve the hydrothermal deoxygenation of organic acids as well as to reduce the cost, we prepared a Cu-Ce/γ-Al_2O_3 catalyst to study the hydrothermal deoxygenation of stearic acid in the absence of H_2. The Brunauer-Emmett-Teller surface area and X-ray diffraction pattern suggest that both CuO and CeO_2 exist in the Cu-Ce/γ-Al_2O_3 catalyst. The crystals of Cu-Ce/γ-Al_2O_3 were more stable compared with those of the Cu/γ-Al_2O_3 catalyst after 12 h of hydrothermal liquefaction at 300 ℃, thereby indicating a better thermal stability of the former. The presence of Cu-Ce/γ-Al_2O_3 catalyst could greatly improve the conversion of stearic acid(94.71%) and the yield of hydrocarbon(81.41%). A preliminary analysis of the mechanism suggests that decarboxylation is the main step in the deoxygenation during the hydrothermal liquefaction of stearic acid. The addition of Cu/γ-Al_2O_3 and Cu-Ce/γ-Al_2O_3 decreased the yield of n-heptadecane and increased the yield of n-octadecane. Besides, the yields of n-paraffins increased drastically from 0.45% to 49.72% along the series from n-nonane to n-hexadecane. Thus, the cracking reactions could be improved in the presence of Cu-Ce/γ-Al_2O_3, suggesting that it is an efficient deoxygenation catalyst in the hydrothermal liquefaction of organic acid. In addition, the Cu-Ce/γ-Al_2O_3 catalyst could help in removing the carbonyl groups, and this effectively reduced the amounts of aldehydes and ketones in the bio-oil.
In order to improve the hydrothermal deoxygenation of organic acids as well as to reduce the cost, we prepared a Cu-Ce/γ-Al_2O_3 catalyst to study the hydrothermal deoxygenation of stearic acid in the absence of H_2. The Brunauer-Emmett-Teller surface area and X-ray diffraction pattern suggest that both CuO and CeO_2 exist in the Cu-Ce/γ-Al_2O_3 catalyst. The crystals of Cu-Ce/γ-Al_2O_3 were more stable compared with those of the Cu/γ-Al_2O_3 catalyst after 12 h of hydrothermal liquefaction at 300 ℃, thereby indicating a better thermal stability of the former. The presence of Cu-Ce/γ-Al_2O_3 catalyst could greatly improve the conversion of stearic acid(94.71%) and the yield of hydrocarbon(81.41%). A preliminary analysis of the mechanism suggests that decarboxylation is the main step in the deoxygenation during the hydrothermal liquefaction of stearic acid. The addition of Cu/γ-Al_2O_3 and Cu-Ce/γ-Al_2O_3 decreased the yield of n-heptadecane and increased the yield of n-octadecane. Besides, the yields of n-paraffins increased drastically from 0.45% to 49.72% along the series from n-nonane to n-hexadecane. Thus, the cracking reactions could be improved in the presence of Cu-Ce/γ-Al_2O_3, suggesting that it is an efficient deoxygenation catalyst in the hydrothermal liquefaction of organic acid. In addition, the Cu-Ce/γ-Al_2O_3 catalyst could help in removing the carbonyl groups, and this effectively reduced the amounts of aldehydes and ketones in the bio-oil.
引文
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