杨媛, 高秀娟, 张伟, 王佳豪, 曹国壮, 梁加仓, 宋法恩, 姜仁政, 韩怡卓, 张清德. Mo-Sn相互作用对Mo1Sn2催化剂二甲醚低温氧化性能的影响[J]. 燃料化学学报(中英文). DOI: 10.3724/2097-213X.2024.JFCT.0005
引用本文: 杨媛, 高秀娟, 张伟, 王佳豪, 曹国壮, 梁加仓, 宋法恩, 姜仁政, 韩怡卓, 张清德. Mo-Sn相互作用对Mo1Sn2催化剂二甲醚低温氧化性能的影响[J]. 燃料化学学报(中英文). DOI: 10.3724/2097-213X.2024.JFCT.0005
YANG Yuan, GAO Xiujuan, ZHANG Wei, WANG Jiahao, CAO Guozhuang, LIANG Jiacang, SONG Faen, JIANG Renzheng, Han Yizhuo, ZHANG Qingde. Effects of Mo-Sn interactions on the performance of Mo1Sn2 catalysts for low-temperature oxidation of dimethyl ether[J]. Journal of Fuel Chemistry and Technology. DOI: 10.3724/2097-213X.2024.JFCT.0005
Citation: YANG Yuan, GAO Xiujuan, ZHANG Wei, WANG Jiahao, CAO Guozhuang, LIANG Jiacang, SONG Faen, JIANG Renzheng, Han Yizhuo, ZHANG Qingde. Effects of Mo-Sn interactions on the performance of Mo1Sn2 catalysts for low-temperature oxidation of dimethyl ether[J]. Journal of Fuel Chemistry and Technology. DOI: 10.3724/2097-213X.2024.JFCT.0005

Mo-Sn相互作用对Mo1Sn2催化剂二甲醚低温氧化性能的影响

Effects of Mo-Sn interactions on the performance of Mo1Sn2 catalysts for low-temperature oxidation of dimethyl ether

  • 摘要: 采用两步水热法制备了一系列Mo-Sn催化剂,通过改变锡氧化物焙烧温度,考察钼氧化物与不同性质锡氧化物之间的作用方式对二甲醚(DME)低温氧化制甲酸甲酯(MF)性能的影响。结果表明,催化剂的性能与处理条件密切相关,当80 ℃焙烧Sn氧化物,与Mo进行水热作用,通过500 ℃焙烧得到的Mo1Sn2-80Sn-500催化剂表现出较好的活性,110 ℃反应温度下,MF选择性达97.7%,二甲醚转化率为14.7%。通过XRD、Raman、FT-IR、低温ESR、NH3-TPD、CO2-TPD及H2-TPR对催化剂的表面物理化学性质以及钼物种的配位结构进行了表征。结果表明,Sn氧化物焙烧温度的改变影响了钼氧化物在SnO2表面的存在形式,较低温度处理Sn氧化物后,催化剂中MoO3与MoOx共存,且Mo-Sn界面处Mo5+配位结构增多,催化剂表面较多的酸量有利于DME氧化反应进行,强碱不利于MF生成。

     

    Abstract: Dimethyl ether (DME) is a colorless and non-toxic coal-based clean fuel, which can be synthesized from coal, biomass, syngas, etc. It is also an important platform compounds for the production of high value-added oxygenated chemicals and diesel oil additives (e.g. formaldehyde, methyl formate (MF), dimethoxymethane(DMM), polyoxymethylene dimethyl ethers (DMMx), etc.). Wherein, methyl formate, as one of the downstream products of DME, is a new starting material and structural unit of C1 chemistry. Due to its molecule contains ester group and formyl group, MF can be widely used to synthesize various valuable industrial chemicals such as formic acid, N, N-dimethyl formamide (DMF), formamide and dimethyl carbonate (DMC). At present, MF is produced in industry through the liquid-phase carbonylation of methanol, where methanol and CO are used as feedstock and sodium methoxide as catalyst. The selectivity of MF obtained by this method is relatively high. However, there are some disadvantages, such as low conversion of methanol, high reaction pressure and difficult separation of catalyst. Meanwhile, the methanol dehydrogenation is another method for synthesizing MF, which includes direct dehydrogenation or oxidative dehydrogenation, and the catalysts used mainly are copper-based catalysts. However, this reaction process has high energy consumption and is controlled by thermodynamics. In recent years, the synthesis of MF from DME by low-temperature oxidation has attracted more and more attention, which has the characteristics of short process, green and good atomic economy. The synthesis of MF by low-temperature oxidation of DME requires multi-functional catalysts containing both acid-base and redox active sites. Mo-Sn catalyst is widely used in this target reaction due to its adjustable valence state. In this paper, a series of Mo1Sn2 catalysts were designed and prepared by a two-step hydrothermal method. By tuning the calcination temperatures of tin precursors, tin oxides with different surface properties were synthesized. The effects of the interaction between tin oxides and the active component molybdenum oxides on the structure-activity relationship of the Mo1Sn2 catalysts and the low-temperature oxidation performance of DME to MF were investigated. The results showed that the performance of the catalysts was closely related to the treatment conditions. When tin oxide was calcined at 80 ℃, and subjected to hydrothermal reaction with Mo, then the Mo1Sn2-80Sn-500 catalyst obtained by calcining at 500 ℃ exhibited better low-temperature oxidation performance. At the reaction temperature of 110 ℃, the selectivity of MF reached 97.7%, and the conversion of DME was 14.7%. The surface physicochemical properties of the catalysts as well as the coordination structures of molybdenum species were characterized in detail by XRD, Raman, FT-IR, low-temperature ESR, NH3-TPD, CO2-TPD and H2-TPR. The results indicated that the change in calcination temperature of tin oxides affected the existence form of molybdenum oxides on the surface of SnO2. After treating tin oxides at lower temperatures, MoO3 and MoOx coexisted in the Mo1Sn2 catalysts. Moreover, at the Mo-Sn interface, Mo species mainly existed in the form of Mo5+ coordination structure. More acid content on the surface of the catalysts was conducive to the oxidation reaction of DME, while strong base sites were not conducive to the formation of MF.

     

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