Research on the catalytic performance of supported Pt catalyst for hydrodeoxygenation of biodiesel
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摘要: 采用XRD、BET、SEM、NH3-TPD对Pt/Al2O3、Pt/Al2O3-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，Brønsted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，Brønsted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C12-18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/Al2O3-ZSM-5 > Pt/Al2O3 > Pt/ZSM-5；适宜的反应工艺条件为：t=350 ℃，p=2 MPa，H2/oil=1000，WHSV=0.5 h-1，在此条件下Pt/Al2O3-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%。
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关键词:
- Pt/Al2O3-ZSM-5 /
- 加氢脱氧 /
- Brønsted酸 /
- 中孔体积 /
- 长链烷烃
Abstract: 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 C12-18 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%.-
Key words:
- Pt/Al2O3-ZSM-5 /
- hydrodeoxygenation /
- Brønsted acid /
- mesoporous volume /
- long chain alkanes
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图 1 催化剂的N2吸附-脱附等温线和孔径分布
Figure 1 N2 adsorption and desorption isotherms and pore size distribution curves of the catalyst
图 4 ZSM-5和ZSM-5-Al2O3的SEM照片
Figure 4 SEM images of the ZSM-5 and ZSM-5-Al2O3 catalyst
(a): ZSM-5(5k×); (b): ZSM-5(15k×); (c): ZSM-5-Al2O3 (2k×); (d): beta-Al2O3(5k×)
图 6 脂肪酸甲酯的加氢脱氧路径示意图
Figure 6 Schematic diagram of hydrodeoxygenation pathway of fatty acid methyl esters
表 1 催化剂的物性参数
Table 1 Physical parameters of the catalysts
Catalyst SBET /(m2·g-1)a vmiso /(m3·g-1)b vmeso /(m3·g-1)c 0.7%Pt/Al2O3 157 0 0.35 0.7%Pt/ZSM-5-Al2O3 181 0.04 0.25 0.7%Pt/ZSM-5 329 0.18 0.06 a: BET surface area; b: microporous pore volume; c: mecroporous pore volume obtained by BJH adsorption cumulative volume of pores between 1.6 and 300 nm in diameter 
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表 2 不同载体催化剂加氢脱氧对比
Table 2 Comparison of hydrodeoxygenation results of different supported catalysts
Parameter t /℃ p /MPa H2/oil WHSV/h-1 Conversion x/% Yield w/% P/A P/Z-A P/Z P/A P/Z-A P/Z Temperature 310 2 1000 0.5 15.3 43.5 6.5 13.5 31.0 4.5 330 2 1000 0.5 23.1 78.4 14.4 19.6 65.8 10.7 350 2 1000 0.5 30.7 99.4 24.8 25.3 86.8 19.5 370 2 1000 0.5 29.5 98.7 24.5 22.6 78.4 17.7 Pressure 350 1 1000 0.5 23.2 91.4 15.8 16.5 79.0 10.8 350 2 1000 0.5 30.7 99.4 24.8 25.3 86.8 19.5 350 3 1000 0.5 29.4 98.4 18.9 18.7 83.9 12.0 H2/oil 350 2 500 0.5 23.2 87.1 17.8 20.1 77.9 14.0 350 2 1000 0.5 30.7 99.4 24.8 25.3 86.8 19.5 350 2 1500 0.5 34.2 98.7 27.0 26.6 85.7 23.3 350 2 2000 0.5 35.7 99.2 28.5 27.8 87.2 24.4 WHSV 350 2 1000 0.5 30.7 99.4 24.8 25.3 86.8 19.5 350 2 1000 1 20.7 78.9 17.5 16.4 67.8 13.8 350 2 1000 1.5 12.4 50.3 11.2 10.1 43.6 9.0 350 2 1000 2 7.0 38.8 6.5 6.3 32.7 5.2
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