催化剂,多孔材料的制备过程.doc

  1. 1、本文档共23页,可阅读全部内容。
  2. 2、有哪些信誉好的足球投注网站(book118)网站文档一经付费(服务费),不意味着购买了该文档的版权,仅供个人/单位学习、研究之用,不得用于商业用途,未经授权,严禁复制、发行、汇编、翻译或者网络传播等,侵权必究。
  3. 3、本站所有内容均由合作方或网友上传,本站不对文档的完整性、权威性及其观点立场正确性做任何保证或承诺!文档内容仅供研究参考,付费前请自行鉴别。如您付费,意味着您自己接受本站规则且自行承担风险,本站不退款、不进行额外附加服务;查看《如何避免下载的几个坑》。如果您已付费下载过本站文档,您可以点击 这里二次下载
  4. 4、如文档侵犯商业秘密、侵犯著作权、侵犯人身权等,请点击“版权申诉”(推荐),也可以打举报电话:400-050-0827(电话支持时间:9:00-18:30)。
查看更多
催化剂,多孔材料的制备过程

Processing of Catalysts, Porous Materials and Aerogels Processing of High Performance Catalysts INTRODUCTION Because of the purity of metal alkoxides and well understanding of the gelation mechanisms, sol–gel processing using metal alkoxides has been widely used for the preparation of supported metal or metal oxide catalysts. Although most of the work concerning sol–gel-prepared catalysts have been focused on the catalysts supported on silica and/or alumina, but, recently, bimetallic and mixed oxide catalysts prepared through the sol–gel processing have also been extensively studied. Accordingly, catalysts reported in this chapter will be classified into four groups as follows; silica supported catalysts, alumina supported catalysts, bimetallic catalysts and mixed oxide catalysts. SILICA SUPPORTED METAL OR METAL OXIDE CATALYSTS BY SOL–GEL TECHNIQUES Tetraethoxysilane (TEOS) has been generally used as a precursor of SiO2 powder in sol–gel techniques, since gelation mechanisms of TEOS were well revealed by Dislich (1971), Teichner et al. (1976), Mazdiyasni et al. (1969) and Sakka (1982). The gelation mechanisms of TEOS mixed with ethanol, water and a small amount of acid, as a catalyst for hydrolysis of TEOS, consist of two steps; the first step is the hydrolysis of TEOS and the second step is a condensation process, as follows: (22-1) (22-2) The structural frame of –Si–O–Si– generated in reaction (22-2) expands three-dimensionally to be transparent wet gels. The wet gels thus obtained are dried and calcined at temperatures higher than 500°C to be sol–gel SiO2 powder. BET surface area, pore volume and pore size of SiO2 powder are important factors to evaluate catalyst carriers, and can be modified to some extent by an addition of either acids or bases in the TEOS solution during gelation (Sakka, 1988). One can use the sol–gel SiO2 powder for a catalyst preparation by conventional impregnation method using an aqueous solution of metal salts such as metal nitrates and

您可能关注的文档

文档评论(0)

dajuhyy + 关注
实名认证
内容提供者

该用户很懒,什么也没介绍

1亿VIP精品文档

相关文档