催化学报

催化学报 ›› 2011, Vol. 32 ›› Issue (4): 672-681.DOI: 10.3724/SP.J.1088.2011.01132

• 研究论文 • 上一篇    下一篇

合成气制 C2 含氧化合物 Rh-Mn/SiO2 催化剂上 CO 吸附的红外光谱研究

陈明英1, 翁维正1,a, 华卫琦2, 伊晓东1, 万惠霖1,b   

  1. 1厦门大学化学化工学院化学系, 固体表面物理化学国家重点实验室, 醇醚酯化工清洁生产国家工程实验室, 福建厦门 361005; 2烟台万华聚氨酯股份有限公司, 山东烟台 264002
  • 收稿日期:2010-11-15 修回日期:2011-02-10 出版日期:2011-04-18 发布日期:2014-08-30

Infrared Spectroscopy Study of CO Adsorption on Rh-Mn/SiO2 Catalyst for C2-Oxygenates Synthesis from Syngas

CHEN Mingying1, WENG Weizheng1,a, HUA Weiqi2, YI Xiaodong1, WAN Huilin1,b   

  1. 1State Key Laboratory of Physical Chemistry of Solid Surfaces, National Engineering Laboratory for Green Chemical Productions of Alcohols, Ethers and Esters, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China; 2Yantai Wanhua Polyurethanes Co., Ltd., Yantai 264002, Shandong, China
  • Received:2010-11-15 Revised:2011-02-10 Online:2011-04-18 Published:2014-08-30

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摘要： 采用浸渍法制备了一系列不同 Mn 含量的 Rh-xMn/SiO2 (x 为 Mn/Rh = 0~3) 催化剂, 在对催化剂进行透射电镜、X 射线衍射表征和 CO 加氢制 C2 含氧化合物催化性能评价的基础上, 采用红外光谱技术分别考察了 50 和 280 oC 下 CO 在催化剂上的吸附, 以及 50~280 oC 内合成气在 Rh/SiO2 和 Rh-0.5Mn/SiO2 催化剂上的程序升温反应, 并在真空和 CO 气氛中考察了 Rh-3Mn/SiO2 催化剂上孪生 CO 吸附物种随温度的变化情况. 结果表明, 在 CO 气氛中, 当温度升至 200oC 时, 孪生 CO 吸附物种消失, 表明在反应温度下可能不存在 Rh+, 即 Rh+可能不是 CO 插入的活性位; Mn 的添加有助于倾斜式 CO 吸附物种的生成; 在合成气反应中 Mn 通过促进高位能甲酰基中间态的生成, 提高了催化剂氢助解离 CO 的能力. 这与适量添加 Mn 使催化剂上 CO 转化率提高的结果一致. 同时, Mn 的添加还有助于削弱线式 CO 吸附物种的 Rh–C 键, 使其更易于在表面上迁移, 进而有利于 CO 的插入, 提高 C2 含氧化合物的选择性.

关键词: 一氧化碳, 加氢, 碳二含氧化合物, 铑, 锰, 二氧化硅, 负载型催化剂, 红外光谱

Abstract: The Rh-xMn/SiO2 (x is Mn/Rh atomic ratio = 0~3) catalyst samples were prepared by conventional co-impregnation. The samples were characterized by transmission electron microscopy, X-ray diffraction and catalytic performance evaluation using CO hydrogenation to C2-oxygenates. CO adsorption behavior over Rh-xMn/SiO2 catalyst under CO and syngas atmosphere at 50 and 280 °C, temperature-programmed reaction of CO with H2 on the Rh/SiO2 and Rh-0.5Mn/SiO2 catalyst samples between 50 and 280 °C, and the change of the gem-dicarbonyl species with increasing temperature under CO atmosphere and vacuum were also studied by infrared spectroscopy. The results showed that, when the temperature was higher than 200 °C, the gem-dicarbonyl species was undetectable on the catalyst in the presence of CO, implying that Rh+ site is unlikely the active site for CO insertion. The addition of Mn promoter resulted in the formation of tilted CO. The addition of Mn could be also in favor of weakening the Rh-C bond in the linear CO adspecies, which facilitated the linear CO migration on the catalyst surface and enhanced the rate of CO insertion into CHx. This is consistent with the results from the experiment to improve C2-oxygenates selectivity with addition of Mn into Rh/SiO2 catalyst. The formyl adspecies was detected by infrared spectroscopy in the experiment of temperature-programmed reaction of syngas over Rh-0.5Mn/SiO2 catalyst. This result suggests that addition of Mn to Rh/SiO2 is helpful to stabilize formyl species and this will be favorable to enhance the rate of hydrogen-assisted CO dissociation during the hydrogenation of CO to C2-oxygenates.

Key words: carbon monoxide, hydrogenation, C2 oxygenate, rhodium, manganese, silicon dioxide, supported catalyst, infrared spectroscopy