负载Pt催化生物柴油加氢脱氧性能研究

采用XRD、BET、SEM、NH_3-TPD对Pt/Al_2O_3、Pt/Al_2O_3-ZSM-5、Pt/ZSM-5催化剂进行表征,在不同反应工艺条件下考察三种分子筛的酸性、孔径分布、外部形貌、晶体结构对其加氢脱氧性能的影响。结果表明,Br■nsted酸性位点和中孔体积占比对脂肪酸甲酯的加氢脱氧反应来说至关重要,其中,Br■nsted酸性位点在脱氧反应中的C-O键断裂发挥主要作用,中孔孔径则能提高整个反应的质量传递效率以及避免C_(12-18)长链烷烃发生裂解。三种催化剂的加氢脱氧催化效果大小为:Pt/Al_2O_3-ZSM-5Pt/Al_2O_3Pt/ZSM-5;适宜的反应工艺条件为:t=350℃,p=2 M Pa,H2/oil=1000,WHSV=0.5 h~(-1),在此条件下Pt/Al_2O_3-ZSM-5的脂肪酸甲酯转化率为99.4%,目标产物液体收率为86.8%。

Research on the catalytic performance of supported Pt catalyst for hydrodeoxygenation of biodiesel

The Pt/Al₂O₃, Pt/Al₂O₃-ZSM-5 and Pt/ZSM-5 catalysts were prepared and characterized by XRD, BET, SEM and NH₃-TPD. The effects of crystal structure, acidity, pore size distribution and external shape of the three catalysts on the hydrodeoxygenation of fatty acid methyl esters were investigated under different reaction conditions. The results show that the Brønsted acidic sites and proportion of mesoporous volume were critical for the hydrodeoxygenation of fatty acid methyl esters. The Brønsted acidic site plays a major role in the C-O bond breakage of deoxygenation reaction,the mesopores improved the mass transfer efficiency of the entire reaction and avoided cracking of C_12-18 long chain alkanes. The hydrodeoxygenation activity of the three catalysts were as follow:Pt/Al₂O₃-ZSM-5>Pt/Al₂O₃>Pt/ZSM-5. The optimal reaction conditions were as follow:t=350 ℃, p=2 MPa, H₂/oil=1000, WHSV=0.5 h^-1. Under the optimal reaction conditions, the fatty acid methyl ester conversion of Pt/Al₂O₃-ZSM-5 was 99.4%, and the liquid yield of the target product was 86.8%.