CO hydrogenation to ethanol over copper-nickel bimetallic catalyst prepared by isomorphous substitution method
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摘要: 采用定向同晶取代法制备了一系列镍孔雀石前驱体的Cu-Ni双金属催化剂。考察了前驱体结构以及催化剂表面组成对催化剂催化性能的影响，并采用浆态床反应器对催化剂的CO加氢制乙醇性能进行评价。实验结果表明，采用定向同晶取代法可以制备出（Cu，Ni）2CO3（OH）2纯物相，取代后的Ni2+主要富集在前驱体（Cu，Ni）2CO3（OH）2表面。焙烧后形成的（Cux，Ni1-x）O固溶体均匀地分散在CuO晶体结构中。还原后的催化剂中Cu、Ni相互均匀分散形成活性界面，促进了低碳醇的合成。其中，不连续分布的Ni活性位点阻止了碳链的进一步增长，从而提高了乙醇选择性。当Ni/Cu原料比为45：100时，（Cux，Ni1-x）O固溶体与CuO之间有较强的相互作用，表现出最好的反应活性和乙醇选择性。Abstract: A series of Cu-Ni bimetallic catalysts derived from nickel-malachite were prepared by an oriented isomorphous substitution method. The effects of the precursor structure and catalysts surface composition on the catalytic performance CO hydrogenation to ethanol were investigated in an agitated slurry autoclave reactor. The studies demonstrated that the pure (Cu, Ni)2CO3(OH)2 phase was obtained by oriented isomorphous substitution method and Ni2+ was rich on the (Cu, Ni)2CO3(OH)2 precursor surface. Uniform distribution of (Cux, Ni1-x)O solid solution were found in CuO crystal lattice. After calcination, the (Cux, Ni1-x)O solid solution dispersed in the crystal structure of CuO uniformly. Cu and Ni dispersed in the catalysts evenly to form an active interface after reduction, which promoted the synthesis of higher alcohols. Discontinuously distributed Ni-active sites prevented the carbon chain from growing further, and enhanced the selectivity of ethanol. The catalyst prepared by the feeding materials with Ni/Cu molar ratio=45:100 was found to exhibit higher activity and ethanol selectivity due to the strong interaction between (Cux, Ni1-x)O solid solution and CuO phase.
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Key words:
- syngas /
- ethanol /
- oriented isomorphous substitution method /
- malachite structure /
- Cu-Ni catalyst
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图 1 前驱体(Cu, Ni)2CO3(OH)2的XRD谱图
Figure 1 XRD patterns of the (Cu, Ni)2CO3(OH)2 precursors
图 2 前驱体(Cu, Ni)2CO3(OH)2的DTG曲线
Figure 2 DTG curves of the (Cu, Ni)2CO3(OH)2 precursors
图 5 孔雀石焙烧形成的CuO和Cu-Ni 45催化剂在不同倍数下的TEM照片
Figure 5 TEM images of the CuO catalyst derived from malachite and Cu-Ni 45 catalyst with different magnification times
(a): TEM image of CuO catalyst with 50 nm; (a1): TEM image of CuO catalyst with 5 nm;
(b): TEM image of Cu-Ni 45 catalyst with 50 nm; (b1): TEM image of Cu-Ni 45 catalyst with 5 nm
图 6 Cu-Ni催化剂的CO-TPD和H2-TPD谱图
Figure 6 CO-TPD (a) and H2-TPD (b) patterns of Cu-Ni catalysts
表 1 前驱体(Cu, Ni)2CO3(OH)2的晶胞参数和平均晶粒粒径
Table 1 Lattice parameters and average crystallite size of the (Cu, Ni)2CO3(OH)2 precursors
Catalyst d20-1a d21-1a va/nm3 Db/nm Cu 2.861 2.781 0.3646 28.5 Cu-Ni 25 2.859 2.777 0.3646 24.8 Cu-Ni 45 2.845 2.775 0.3644 15.4 Cu-Ni 65 2.844 2.769 0.3644 18.1 Cu-Ni 85 2.841 2.769 0.3632 18.3 Cu-Ni 200 2.836 2.768 0.3633 19.0 a: the lattice parameters of (Cu, Ni)2CO3(OH)2 were calculated from the XRD patterns;
b：D: crystallite size of the precursors, derived from XRD peak 2θ=31.3°
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表 2 前驱体(Cu, Ni)2CO3(OH)2的ICP分析
Table 2 ICP determination for the (Cu, Ni)2CO3(OH)2 precursors
Catalyst Feed molar ratio Ni/Cu Ni/Cu
(molar ratio)Ni/(Cu+Ni) by ICP(molar ratio) Ni/(Cu+Ni) by XPS(molar ratio) Cu-Ni 25 25:100 0.22 0.18 0.65 Cu-Ni 45 45:100 0.40 0.28 0.66 Cu-Ni 65 65:100 0.47 0.32 0.73 Cu-Ni 85 85:100 0.49 0.33 0.79 Cu-Ni 200 200:100 0.51 0.34 0.86
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表 3 Cu-Ni催化剂的织构性质
Table 3 Textural properties of the Cu-Ni catalysts
Catalyst ABET/(m2·g-1) D/nm CuO (Cux, Ni1-x)O Cu 14.7 24.7 - Cu-Ni 25 28.3 15.8 18.5 Cu-Ni 45 41.3 13.5 9.3 Cu-Ni 65 34.7 14.2 11.7 Cu-Ni 85 33.1 13.8 11.1 Cu-Ni 200 19.8 17.9 16.0 ABET: specific surface area of the Cu-Ni catalysts;
D: crystallite size of CuO, derived from XRD peak 2θ=38.7°
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表 4 Cu-Ni催化剂催化CO加氢合成醇性能
Table 4 Catalytic performance of the copper-nickel bimetallic catalysts for CO hydrogenation to ethanol
Catalyst xCO /% ectivity s/% CH4 CH3OH C2H5OH C3H7OH C4H9OH CxOH Cu-Ni 25 28.6 35.2 19.4 15.8 6.8 3.3 45.3 Cu-Ni 45 35.3 38.5 21.8 19.1 5.3 2.9 49.1 Cu-Ni 65 28.7 49.3 24.4 13.2 4.0 1.6 43.2 Cu-Ni 85 25.8 50.4 31.0 11.7 2.2 0.9 45.8 Cu-Ni 200 22.8 51.4 17.8 9.6 1.7 0.5 29.6 reaction conditions: 270 ℃, 5.0 MPa, CO:H2(volume ratio)=1:2, 3000 L/(kg·h)
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