催化学报

催化学报 ›› 2010, Vol. 31 ›› Issue (11): 1374-1380.DOI: 10.3724/SP.J.1088.2010.00451

• 研究论文 • 上一篇    下一篇

SBA-15 负载 β-Mg2V2O7 催化剂的制备及其催化丙烷选择氧化脱氢的性能

张胜红, 张鸿鹏, 孙吉莹, 刘海超   

  1. 北京大学化学与分子工程学院, 分子动态与稳态国家重点实验室, 北京分子科学国家实验室, 北京 100871
  • 收稿日期:2010-04-29 出版日期:2010-11-12 发布日期:2014-03-28

Preparation of SBA-15-Supported β-Mg2V2O7 Catalysts and Their Properties in Oxidative Dehydrogenation of Propane

ZHANG Shenghong, ZHANG Hongpeng, SUN Jiying, LIU Haichao*   

  1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Stable and Unstable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
  • Received:2010-04-29 Online:2010-11-12 Published:2014-03-28

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摘要： 以 MgO 修饰的 SBA-15 为载体, 采用浸渍法制备了负载 β-Mg2V2O7 催化剂, 并运用 X 射线衍射、拉曼光谱、紫外-可见漫反射光谱和 H2 程序升温还原等技术对催化剂 V 中心的结构和还原性能进行了表征. 结果表明, β-Mg2V2O7 具有与 α-Mg2V2O7 相同的结构单元, 但其催化丙烷氧化脱氢 (ODH) 反应的初始活性和初始选择性均低于后者. 与体相 β-Mg2V2O7 相比, 负载的 β-Mg2V2O7 上 V 中心分散度以及丙烷 ODH 反应活性和选择性更高, 520 oC 时丙烷 ODH 反应的初始活性提高了约 20 倍, 丙烯初始选择性也从体相的 88.3% 提高到 94.1%, 接近于 α-Mg2V2O7 (94.6%), 并且在 20% 的丙烷转化率时也表现出相似的规律. 这与表征催化剂选择性的两个本征动力学参数 k1/k2 (丙烷初级 ODH 和燃烧反应速率常数之比) 和 k3/k1 (次级丙烯燃烧和初级丙烷 ODH 反应速率常数之比) 反映出的规律一致. 这些对体相和负载的 Mg2V2O7 催化剂催化丙烷 ODH 反应本征特性的认识将有助于设计合成更高效的 Mg-V-O 催化剂, 如基于 α-Mg2V2O7 结构的高分散催化剂, 以获得更高的丙烷 ODH 反应活性和选择性.

关键词: 丙烷, 丙烯, 氧化脱氢, 焦钒酸镁, 负载型催化剂

Abstract:  β-Mg2V2O7 catalysts supported on MgO-modified SBA-15 with V surface density of 4.1-8.5 nm-2 were synthesized by impregnation of the support with a pre-prepared aqueous solution of ammonium metavanadate, citric acid, and magnesium nitrate. The structure and reducibility of the catalysts were characterized by X-ray diffraction, Raman spectroscopy, diffuse reflectance UV-Vis spectroscopy, and temperature-programmed reduction in H2. For oxidative dehydrogenation (ODH) of propane, bulk β-Mg2V2O7 phase was much less active and selective than α-Mg2V2O7 although they have the same dimeric tetrahedral VO4 units connected by bridging V-O-V bonds. Compared to the bulk phase, the greater accessibility of V sites on the supported β-Mg2V2O7 catalysts led to an increase in not only the initial propane ODH rates by about 20 times but also the initial propene selectivity from 88.3 to 94.1%, as high as that for α-Mg2V2O7 (94.6%) that has been considered as the most selective Mg-V-O phase for propane ODH reactions. The selectivity results are consistent with those reflected by the two kinetic parameters, k1/k2 and k3/k1, which represent the ratios of the rate constants for primary propane ODH (k1) to propane combustion (k2) and that for secondary propene combustion (k3) to k1. Such understanding on the intrinsic catalytic properties of the bulk and supported Mg2V2O7 catalyst provides useful information for design of new Mg-V-O-based catalysts, for example, dispersed α-Mg2V2O7 catalyst with high activity and selectivity for propane ODH reactions under mild conditions.

Key words: propane, propene, oxidative dehydrogenation, magnesium pyrovanadate, supported catalyst