The structure and hydrogenation performance for methyl benzoate of MnOx/ZrO2-Cr2O3 catalyst
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摘要: 采用并流共沉淀和浸渍法制备了MnOx/ZrO2-Cr2O3催化剂。利用X射线衍射(XRD)、N2物理吸附(BET)、氢气程序还原(H2-TPR)、X射线光电子能谱(XPS)等手段对催化剂的结构和表面性质进行了表征。结果表明,Cr的引入导致ZrO2晶型由m-ZrO2向t-ZrO2转变,随着Cr含量的增加,ZrO2-Cr2O3复合氧化物的比表面积逐渐增大,平均孔径逐渐降低,孔结构也发生变化;Mn的引入会造成ZrO2-Cr2O3复合氧化物中Cr的迁移,同时也有利于ZrO2晶型由m-ZrO2向t-ZrO2转变,从而引起催化剂比表面积、孔结构的变化;含4% Mn和2.5% Cr的MnOx/ZrO2-Cr2O3催化剂对苯甲酸甲酯加氢反应的单程转化率和选择性分别达到93.86%和86.05%。Abstract: MnOx/ZrO2-Cr2O3 catalysts were prepared by cocurrent coprecipitation and impregnation. The structure and surface properties of the catalyst were characterized by X-ray diffraction (XRD), N2 physical adsorption (BET), hydrogen temperature programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). These results showed that the addition of Cr led to the transformation of ZrO2 crystal form from m-ZrO2 to t-ZrO2. With the increase of Cr content, the BET of the composite oxide ZrO2-Cr2O3 increased gradually, the average pore size decreased and the pore structure also changed. The impregnation of Mn caused the migration of Cr in the ZrO2-Cr2O3 composite oxide, and promoted the transformation of the ZrO2 crystal form from m-ZrO2 to t-ZrO2, the BET and pore structure of the catalyst changed also. The conversion and selectivity of MnOx/ZrO2-Cr2O3 catalysts containing 4% Mn and 2.5% Cr for methyl benzoate hydrogenation were 93.86% and 86.05%, respectively.
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Key words:
- methyl benzoate /
- benzaldehyde /
- benzyl alcohol /
- selective hydrogenation /
- catalyst
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表 1 ZrO2-Cr2O3复合氧化物的孔径及比表面积
Table 1 Textual properties of ZrO2-Cr2O3
Cr content w/% SBET/(m2·g−1) v/(cm3·g−1) d/nm 0 28.6 0.097 13.7 2.5 86.1 0.201 9.3 5.0 109.1 0.194 7.1 7.5 144.1 0.182 5.0 10 135.1 0.152 4.5 表 2 bMnOx/ZrO2-aCr2O3的孔径及比表面积
Table 2 Textual properties of bMnOx/ZrO2-aCr2O3
Mn content
w/%Cr content
w/%SBET/(m2·g−1) v /(cm3·g−1) d/nm 0 2.5 86.1 0.20 9.3 4 2.5 82.1 0.18 8.6 8 2.5 72.2 0.16 8.9 10 2.5 63.0 0.14 8.9 8 2.5 72.2 0.16 8.9 8 5.0 84.9 0.14 7.1 8 10 87.6 0.12 5.3 表 3 bMn/2.5Cr-Zr的Mn元素结合能
Table 3 Binding energy of Mn 2p3/2 determined from XPS
Sample Mn 2p3/2 /eV Mn 2p1/2 /eV ΔEB
/eVRelative ratio of Mn oxide w/% MnO2 Mn2O3 Mn3O4 8Mn/
2.5Cr-Zr641.6 653.3 11.7 37.37 36.04 26.58 表 4 bMnOx/ZrO2-aCr2O3催化剂的苯甲酸甲酯加氢性能
Table 4 Performance of bMnOx/ZrO2-aCr2O3 catalysts
Mn content w/% Cr content w/% Methyl benzoate x/% s/% Selectivity s/% benzaldehyde benzyl alcohol toluene benzyl benzoate 0 0 19.84 81.29 48.43 32.87 3.85 11.60 0 2.5 57.27 67.23 41.92 25.31 22.37 5.68 0 5.0 92.68 52.12 27.45 24.67 38.66 3.11 4 2.5 93.86 86.05 36.14 49.91 8.49 4.21 8 2.5 89.47 87.71 40.89 46.81 6.91 4.29 8 5.0 87.66 83.32 38.99 44.33 10.47 4.47 8 10 86.76 82.44 40.04 42.40 12.00 4.04 10 2.5 88.43 87.54 38.82 48.72 6.52 4.56 *reaction conditions: t = 390 ℃, p = 1.0 MPa, weight hourly space velocity of methyl benzoate = 0.5 h−1, n(H2)/ n(MB) = 10 -
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