Low-temperature oxidation of methanol to dimethoxymethane over Mo-Sn catalyst
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摘要: 采用水热合成法制备了甲醇合成甲缩醛的新型Mo-Sn催化剂。该催化剂可以在低Mo含量时实现甲醇低温氧化高选择性制取甲缩醛。通过考察Mo含量对催化剂结构及甲醇低温氧化制甲缩醛性能的影响,发现Mo1Sn10催化剂在甲醇氧化中表现出了较好的催化性能,在140 ℃、常压反应条件下,甲醇转化率为14.2%,甲缩醛选择性达到了88.9%,并且反应过程中无COx生成。采用XRD、Raman、FT-IR、XPS、NH3-TPD及H2-TPR等表征手段对催化剂进行深入研究。结果表明,不同Mo含量的催化剂结构性能存在着明显的差别,较低含量Mo的存在更有利于Mo5+及MoOx的生成,而由此引起的酸性及氧化还原性的变化是催化剂具有良好性能的重要原因。Abstract: A new Mo-Sn catalyst prepared by hydrothermal method was used for the synthesis of dimethoxymethane (DMM) from methanol oxidation. The catalyst with low Mo content can achieve low-temperature oxidation of methanol to DMM with high selectivity. The influence of Mo content on the structure and the catalytic performance of the catalyst was investigated. It was found that Mo1Sn10 catalyst showed the best catalytic performance under the conditions of 140 °C and atmospheric pressure, the methanol conversion was 14.2%, and the selectivity of DMM reached 88.9% without the formation of COx during the reaction process. The catalysts were characterized by XRD, Raman, FT-IR, XPS, NH3-TPD and H2-TPR. The results showed that the catalysts with different Mo content had obvious differences in structure and performance. Lower Mo content was more conducive to the formation of Mo5+ and MoOx, and the resulting changes in acidity and redox properties were the important reasons for the excellent performance of the catalysts.
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Key words:
- methanol /
- low temperature oxidation /
- dimethoxymethane /
- Mo-Sn catalyst /
- Mo5+ species
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表 1 不同Mo量Mo-Sn催化剂上甲醇转化的反应性能
Table 1 Effect of Mo content on the performance of Mo-Sn catalysts for methanol conversion
Catalyst CH3OH
conversion/%C-mol selectivity/% MF DME FA DMM COx MoO3 0 0 0 0 0 0 Mo2Sn1 17.2 22.4 23.1 0 54.5 0 Mo1Sn1 28.3 45.0 23.5 0 31.5 0 Mo1Sn2 33.9 43.8 17.2 2.9 36.1 0 Mo1Sn3 32.2 42.8 9.2 0 48.0 0 Mo1Sn4 26.5 36.3 5.0 0 58.7 0 Mo1Sn5 21.0 20.9 4.3 2.2 72.6 0 Mo1Sn8 14.5 10.5 1.7 0 87.8 0 Mo1Sn10 14.2 11.1 0 0 88.9 0 Mo1Sn20 10.5 11.8 0 0 88.2 0 SnO2 0 0 0 0 0 0 Reaction conditions: atmospheric pressure, tR = 140 ℃,n(CH3OH)∶ n(O2) = 1∶9.415, CH3OH flow rate = 0.817 mL/h, GHSV = 7200 h−1 表 2 不同Mo含量Mo-Sn催化剂的XPS-Mo 3d谱图分析
Table 2 XPS-Mo 3d analysis of Mo-Sn catalysts with different Mo contents
Catalyst Mo6+
3d3/2Mo6+
3d5/2Mo5+
3d3/2Mo5+
3d5/2Mo6+/
%Mo5+/
%Mo2Sn1 236.33 233.07 235.18 231.78 94.5 5.5 Mo1Sn2 236.27 233.10 235.10 231.80 93.1 6.9 Mo1Sn4 236.24 233.10 235.17 231.90 86.3 13.7 Mo1Sn8 236.18 233.02 235.06 231.84 69.6 30.4 Mo1Sn20 236.14 232.94 235.11 231.87 58.9 41.1 表 3 不同Mo含量Mo-Sn催化剂的XPS-O 1s谱图分析
Table 3 XPS-O 1s analysis of Mo-Sn catalysts with different Mo contents
Catalyst OOH Oad Olat OOH/OTotal Oad/OTotal Olat/OTotal Mo2Sn1 532.35 531.35 530.80 0.17 0.31 0.52 Mo1Sn2 532.30 531.36 530.90 0.24 0.34 0.42 Mo1Sn4 532.39 531.39 530.89 0.28 0.38 0.34 Mo1Sn8 523.40 531.30 530.84 0.32 0.32 0.36 Mo1Sn20 532.32 531.30 530.74 0.33 0.31 0.36 -
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