催化学报

催化学报 ›› 2006, Vol. 27 ›› Issue (10): 916-920.

• 研究论文 • 上一篇    下一篇

MnCl2-H4SiW12O40/SiO2催化氧化二甲醚制取甲缩醛

张清德1,2,谭猗生1,杨彩虹1,柳玉琴1,韩怡卓1   

  1. 1 中国科学院山西煤炭化学研究所煤转化国家重点实验室, 山西太原 030001; 2 中国科学院研究生院, 北京 100049
  • 收稿日期:2006-10-25 出版日期:2006-10-25 发布日期:2010-11-28

Catalytic Oxidation of Dimethyl Ether to Dimethoxymethane over MnCl2-H4SiW12O40/SiO2 Catalyst

ZHANG Qingde1,2, TAN Yisheng1, YANG Caihong1, LIU Yuqin1, HAN Yizhuo1*   

  1. 1 State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, The Chinese Academy of Sciences, Taiyuan 030001, Shanxi, China; 2 Graduate University of The Chinese Academy of Sciences, Beijing 100049, China
  • Received:2006-10-25 Online:2006-10-25 Published:2010-11-28

PDF

703

被引次数

83

摘要： 采用浸渍法制备了H4SiW12O40/SiO2杂多酸催化剂,分别使用MnCl2, SnCl4和CuCl2对其进行修饰,并在常压连续流动固定床反应器中考察了催化剂对二甲醚选择氧化制取甲缩醛的催化活性. 结果表明, MnCl2修饰的H4SiW12O40/SiO2催化剂的活性和甲缩醛选择性均高于SnCl4和CuCl2修饰的催化剂. 进一步考察了不同MnCl2含量及反应温度对反应的影响. 在MnCl2含量为5%, 反应温度为593 K时, MnCl2-H4SiW12O40/SiO2催化剂的活性和甲缩醛选择性最佳,二甲醚转化率为8.6%, 甲缩醛选择性为36.3%. X射线衍射结果显示, MnCl2与H4SiW12O40相互作用并均匀地分散在载体上. 用红外光谱研究了MnCl2-H4SiW12O40/SiO2催化剂的结构,发现改性后的催化剂基本保持了杂多酸的Keggin结构. NH3程序升温脱附结果显示, MnCl2的加入较明显地降低了催化剂的酸强度和酸中心数目.

关键词: 二甲醚, 催化氧化, 甲缩醛, 氯化锰, 硅钨酸, 硅胶, 负载型催化剂

Abstract: The H4SiW12O40/SiO2 heteropolyacid catalyst for the catalytic oxidation of dimethyl ether to dimethoxymethane was prepared by the impregnation method. MnCl2, SnCl4, and CuCl2 were used to modify the catalyst to improve its activity and selectivity. The catalytic oxidation reaction was carried out in a continuous flow fixed-bed reactor. H4SiW12O40/SiO2 is active for the dimethyl ether oxidation, but the selectivity for dimethoxymethane is as low as 4.8%. Modification of H4SiW12O40/SiO2 with 5% MnCl2 significantly improves the dimethoxymethane selectivity up to 27.9% at 633 K, while SnCl4- and CuCl2-modified catalysts give dimethoxymethane selectivities of 16.4% and 0.4%, respectively, under the same conditions. The effects of the MnCl2 content (2%-20%) and reaction temperature (573-633 K) on the reaction were investigated. A dimethyl ether conversion of 8.6% and a dimethoxymethane selectivity of 36.3% were obtained under the optimum conditions of 593 K and 5% MnCl2 content. X-ray diffraction patterns of the catalysts show that MnCl2 and H4SiW12O40 interact and are dispersed uniformly on the support. Infrared spectra demonstrate that the Keggin structure of H4SiW12O40 remains almost unchanged over the modified catalyst. Ammonia temperature-programmed desorption profiles indicate that MnCl2 modification reduces the acidity of H4SiW12O40/SiO2 by decreasing the acid center numbers.

Key words: dimethyl ether, catalytic oxidation, dimethoxymethane, manganese chloride, tungstosilicic acid, silica, supported catalyst