华东师范大学学报（自然科学版） ›› 2023, Vol. 2023 ›› Issue (1): 95-103.doi: 10.3969/j.issn.1000-5641.2023.01.010

• 绿色催化反应和技术 • 上一篇    下一篇

化学链甲烷氧化偶联载氧体催化剂Na2WO4/Mn7SiO12-SiO2的研究

高雅1, 孙伟东1, 赵国锋1, 刘晔1, 路勇1,2,*()   

  1. 1. 华东师范大学 化学与分子工程学院 上海市绿色化学与化工过程绿色化重点实验室, 上海　200062
    2. 崇明生态研究院, 上海　202162
  • 收稿日期:2022-06-15 接受日期:2022-09-21 出版日期:2023-01-25 发布日期:2023-01-07
  • 通讯作者: 路勇 E-mail:ylu@chem.ecnu.edu.cn
  • 基金资助:
    国家自然科学基金 (22072043, 21773069, 21703069); 上海市科学技术委员会基础重点项目 (18JC1412100)

Study of an Na2WO4/Mn7SiO12-SiO2 oxygen-carrier catalyst for chemical looping-oxidative coupling of methane

Ya GAO1, Weidong SUN1, Guofeng ZHAO1, Ye LIU1, Yong LU1,2,*()   

  1. 1. Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai　200062, China
    2. Institute of Eco-Chongming, Shanghai　202162, China
  • Received:2022-06-15 Accepted:2022-09-21 Online:2023-01-25 Published:2023-01-07
  • Contact: Yong LU E-mail:ylu@chem.ecnu.edu.cn

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摘要：

通过提高Mn2O3-Na2WO4/SiO2中Mn2O3的含量并经原位化学链甲烷氧化偶联 (CL-OCM) 反应活化制得了具有良好活性和选择性的Na2WO4/Mn7SiO12-SiO2载氧体催化剂, 在750℃、12 s甲烷停留时间、27的较低剂烷比 (mCat/mCH4) 条件下, 获得了12%的CH4转化率和81.5%的C2-C3选择性; 进一步降低mCat/mCH4到13.5时, CH4转化率降至7%, 但C2-C3选择性可达90%. 要指出的是, C3产物中仅检测到了C3H6, 其选择性约为5%. XRD (X-ray diffraction) 分析表明, 随着CL-OCM氧化-还原循环次数的增加, 催化剂的载氧体逐渐由Mn2O3转变为Mn7SiO12, 同时伴随着CH4转化率的逐渐下降及C2-C3选择性的不断提高直至稳定. 基于上述认识, 将Na2WO4/Mn2O3-SiO2在800℃空气中直接焙烧, 可一步制得Na2WO4/Mn7SiO12-SiO2载氧体催化剂. 相比于Mn2O3, 载氧体Mn7SiO12中的晶格氧活度较低, 构建的Mn7SiO12 $ \leftrightarrow $ [MnSiO3 + MnWO4]的氧化-还原循环可适度减缓晶格氧的释放速率, 抑制了目标产物的深度氧化, 从而获得了较高的C2-C3产物选择性, 但CH4转化率有所降低. 上述研究结果对设计构建高效的CL-OCM载氧体催化剂具有借鉴意义.

关键词: 甲烷氧化偶联制乙烯, 化学链, 载氧体催化剂, 晶格氧氧化, 锰

Abstract:

A promising chemical looping-oxidative coupling of methane (CL-OCM) oxygen-carrier catalyst, Na2WO4/Mn7SiO12-SiO2, was obtained by adding extra Mn2O3 to Mn2O3-Na2WO4/SiO2 and in-situ activating in the reaction stream. After experiencing an induction period, the oxygen-carrier phase transformed from Mn2O3 to Mn7SiO12 in association with an improvement in C2-C3 selectivity but decreased CH4 conversion. The Na2WO4/Mn7SiO12-SiO2 oxygen-carrier catalysts could also be obtained by directly calcining the Na2WO4/Mn2O3-SiO2 precursor at 800 ℃ in air. At 750 ℃ and a CH4 residence time of 12 s, the catalyst achieved 12% (or 7%) CH4 conversion and 81.5% (or 90.0%) C2-C3 selectivity using a mCat/mCH4 weight ratio of 27 (or 13.5). Notably, only C3H6 was detected as C3 products, whose selectivity was about 5%. The CL-OCM reaction proceeded selectively through the redox cycle mode of Mn7SiO12 $ \leftrightarrow $ [MnSiO3 + MnWO4]. The lattice-oxygen mobility in Mn7SiO12 was much weaker than that in Mn2O3, which improved C2-C3 selectivity but decreased CH4 conversion. Our findings provide guidance for the exploration of more advanced catalytic oxygen-carrier catalysts toward efficient CL-OCM process.

Key words: oxidative coupling of methane to ethylene, chemical looping, oxygen-carrier catalyst, lattice-oxygen oxidation, manganese

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