Effect of Ce doping on the performance of MoSn catalyst in the selective oxidation of dimethyl ether to methyl formate
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摘要: 采用无沉淀剂一步水热法合成了不同含量Ce掺杂的MoSn催化剂，考察了Ce的掺杂量对其二甲醚（DME）选择氧化催化性能的影响。结果表明，当Ce含量为0.5%时，MoSn催化剂的活性最高，在130℃下DME的转化率达11.8%，MF的选择性为92.2%。采用氮吸附、XRD、NH3-TPD、CO2-TPD、H2-TPR、XPS和in situ-IR等表征技术对催化剂进行了表面性质和结构分析，发现Ce的掺杂虽然没有从根本上改变MoSn催化剂的结构，但明显提高了MoSn催化剂中五价钼的含量。Abstract: A series of MoSn catalysts doped with different Ce loadings were prepared by hydrothermal method and their catalytic performance in the selective oxidation of dimethyl ether (DME) to methyl formate (MF) was investigated. The results indicate that the introduction of 0.5% Ce can significantly improve the activity of the MoSn catalyst over the 0.5%Ce-MoSn catalyst, the conversion of DME reaches 11.8% at 130 ℃, with a selectivity of 92.2% for MF. The MoSn catalysts were characterized by nitrogen sorption, XRD, NH3-TPD, CO2-TPD, H2-TPR, XPS and in situ-IR; the results illustrate that a small amount of Ce in the MoSn catalyst can obviously increase the quantity of Mo5+, though it has little effect on the structure of the MoSn catalyst.
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Key words:
- MoSn catalyst /
- dimethyl ether /
- selective oxidation /
- methyl formate /
- hydrothermal method
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图 1 不同Ce含量的钼锡催化剂N2吸附鄄脱附等温线和孔径分布
Figure 1 N2 adsorption-desorption isotherms and pore distribution of the Ce-doped MoSn catalysts with different Ce loadings
图 2 不同Ce含量的MoSn催化剂的XRD谱图
Figure 2 XRD patterns of the Ce-doped MoSn catalysts with different Ce loadings
图 3 不同Ce含量的MoSn催化剂的NH3-TPD (a)和CO2-TPD (b)谱图
Figure 3 NH3-TPD (a) and CO2-TPD (b) profiles of the Ce-doped MoSn catalysts with different Ce loadings
图 4 不同Ce含量的MoSn催化剂的H2-TPR谱图
Figure 4 H2-TPR profiles of the Ce-doped MoSn catalysts with different Ce loadings
图 5 不同Ce含量的MoSn催化剂的XPS-Mo 3d谱图
Figure 5 Mo 3d XPS spectra of the Ce-doped MoSn catalysts with different Ce loadings
图 6 不同Ce含量MoSn催化剂的原位红外光谱谱图
Figure 6 In situ-IR spectra of the Ce-doped MoSn catalysts with different Ce loadings
表 1 Ce含量对MoSn催化剂上DME氧化制备甲酸甲酯的影响
Table 1 Effect of the Ce loading on the activity of Ce-doped MoSn catalyst in the selective oxidation of DME to MF
Ce
wmol/%DME
con. x/ %Selectivity sC-mol/% MF CH3OH CO FA CO2 0 10.3 84.6 14.3 1.1 0 0 0.5 11.8 92.2 6.1 1.7 0 0 1 10.6 84.5 14.1 1.4 0 0 5 7.8 78.2 21.1 0.7 0 0 10 6. 8 76. 2 23. 4 0. 4 0 0 reaction conditions: 130 ℃; GHSV = 1800 h-1; DME/O2 = 1; Mo/Sn = 1:2 
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表 2 反应温度对0.5%Ce-Mo1Sn2催化剂上DME氧化制备甲酸甲酯的影响
Table 2 Effect of reaction temperature on the selective oxidation of DME to MF over the 0.5%Ce-Mo1Sn2 catalyst
tR/℃ DME
con. x/ %Selectivity sC-mol/% MF CH3OH CO FA CO2 150 90.2 1.2 0.3 98.5 0 0 150* 10.8 78.2 8.3 13.5 0 0 140 15.4 86.9 0.7 12.4 0 0 130 11.8 92.2 6.1 1.7 0 0 120 7.8 89.5 4.4 6.1 0 0 110 7.2 77.1 17.6 5.3 0 0 100 5.8 65.2 31.6 3.2 0 0 reaction conditions: GHSV = 1800 h-1; DME/O2 = 1; Mo/Sn=1:2; *: for the reaction over the undoped Mo1Sn2 catalyst
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表 3 不同Ce含量的MoSn催化剂的织构性质
Table 3 Textural properties of the Ce-doped MoSn catalysts with different Ce loadings
Catalyst Surface area A / (m2·g-1) Pore volume v / (cm3·g-1) Average pore diameter d / nm Mo1Sn2 141.16 0.118 3.52 0.5%Ce-Mo1Sn2 140.87 0.139 3.57 5% Ce-Mo1Sn2 136.05 0.130 3.61 10% Ce-Mo1Sn2 120.07 0.112 3.48
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表 4 不同Ce含量的MoSn催化剂XPS-Mo 3d谱图
Table 4 Analysis of the Mo 3d XPS spectra of the Ce-doped MoSn catalysts with different Ce loadings
Catalyst Mo6+3d3 / 2 Mo6+3d5 / 2 Mo5+3d3 / 2 Mo5+3d3 / 2 Mo6+ / % Mo5+ / % Mo1Sn2 236.18 233.05 235.17 231.95 82.6 17.4 0. 5% Ce-Mo1Sn2 236.18 233.05 235.17 231.95 79.9 20.1 5% Ce-Mo1Sn2 236.12 233.05 235.17 231.95 83.1 16.9
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