Na-W-Mn/SiO2催化剂上不同含量WO4活性位点在甲烷氧化偶联中的催化行为

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中文摘要：甲烷氧化偶联(OCM)作为生产C2(C2H6 和C2H4)的直接途径受到了广泛关注.在传统催化剂中,Mn/Na2WO4/SiO2(Na-W-Mn/SiO2)类催化剂具有甲烷转化率高、C2选择性高且在高温下也能保持相对高的稳定性等优点.本文利用硅钨酸作为前驱体,制备了一系列不同W载量的Na-nW-Mn/SiO2催化剂,并进行了X射线粉末衍射、透射电子显微镜、氢气程序升温还原、氧气程序升温脱附和X射线光电子能谱表征以及甲烷氧化偶联活性的评价.研究发现,所有催化剂上的Na2WO4、Mn2O3和α-方英石晶相之间均存在较强的相互作用,并通过协同催化作用来提高催化剂的OCM性能.随着W载量的持续增加,以硅钨酸作为前驱体制备的催化剂表面的W物种一直保持以四面体WO4的形式存在,而构效关系分析揭示了四面体WO4是此系列催化剂上OCM反应的活性中心.具有高含量四面体WO4的Na-10.0％W-Mn/SiO2催化剂有较低的W6+→W4+还原温度和较高的表面晶格氧占比,这可能是其获得最佳甲烷转化率和C2产率的主要原因.当温度为775℃时,Na-10.0％W-Mn/SiO2催化剂上CH4的转化率为44.2％,C2的产率为24.1％,其中乙烯的产率为18.7％.

外文标题：Catalytic Behavior of Different Amounts of WO4 Active Sites on Na-W-Mn/SiO2 Catalysts for Oxidative Coupling of Methane

外文摘要：Oxidative coupling of methane(OCM)served as a direct pathway for producing C2(C2H6 and C2H4)has received widespread attention.Among the conventional catalysts,Mn/Na2WO4/SiO2(Na-W-Mn/SiO2)catalysts have many advantages like:high methane conversion,high C2 selectivity,and relatively high stability even at high temperature.In this work,a series of Na-nW-Mn/SiO2 catalysts with different W loadings were prepared using silicotungstic acid as the precursor.In order to further investigate the effects of W loadings on the structure and OCM performance of the catalysts,X-ray diffraction(XRD),transmission electron microscopy(TEM),hydrogen tempera-ture programmed reduction(H2-TPR),oxygen temperature programmed desorption(O2-TPD),and X-ray photoelec-tron spectra(XPS)characterizations and the activity evaluation for oxidative coupling of methane were performed on all samples.The results demondtrated that there is a strong interaction among the crystal phases of Na2WO4,Mn2O3 and α-cristobalite,which enhances the OCM performance of these catalysts through synergistic catalysis.It is interesting that with the continuous increase of W loading,the W species maintained the form of tetrahedral WO4 on the surface of catalysts.Structure-activity relationship analysis shows that tetrahedral WO4 is the active center for the OCM reaction on this series of catalysts.Therefore,the Na-10.0％W-Mn/SiO2 catalyst with high tetrahedral WO4 content has a lower reduction temperature from W6+→W4+and a higher proportion of surface lattice oxygen,which may be the main reason for its optimal methane conversion and C2 yield.When the temperature reached 775℃,the conversion of methane over Na-10.0％W-Mn/SiO2 catalyst is 44.2％,the yield of C2 is 24.1％,and the yield of ethylene is 18.7％.

外文关键词：

Na-W-Mn/SiO2 catalystOxidative coupling of methaneDifferent W contentsYield of ethyleneC2

作者：

宋佳欣、范晓强、刘百军、赵震

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作者单位：

中国石油大学(北京)重质油国家重点实验室,北京 102249

沈阳师范大学化学化工学院,能源与环境催化研究所,沈阳 110034

关键词：

Na-W-Mn/SiO2催化剂甲烷氧化偶联不同W含量乙烯收率 C2

基金：

国家自然科学基金国家自然科学基金辽宁省应用基础研究计划项目沈阳市科技计划项目辽宁省"兴辽英才"青年拔尖人才计划项目沈阳师范大学重大项目孵化工程项目

项目编号：

22172101921453012023JH2/10160005922-322-3-28XLYC2203138ZD201901

出版年：

2024

DOI：

10.7503/cjcu20240174

高等学校化学学报

中华人民共和国教育部委托吉林大学和南开大学

高等学校化学学报

CSTPCD北大核心

影响因子：1.067

ISSN：0251-0790

年,卷(期)：2024.45(9)