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低温加氢裂解脱除高硅ZSM-5分子筛内TPAOH模板剂
  • ISSN号:1000-6818
  • 期刊名称:物理化学学报,
  • 时间:2015.3.2
  • 页码:793-799
  • 分类:O643[理学—物理化学;理学—化学]
  • 作者机构:[1]中国科学院广州能源研究所,中国科学院可再生能源重点实验室,广州510640, [2]中国科学院大学,北京100049
  • 相关基金:国家自然科学基金(51106165,51202245); 广东省自然科学基金(10251007006000000,S2013010014896)资助项目
  • 相关项目:高CO2选择性有序碳纳米管复合膜的构建与微结构特性研究
中文摘要:

分子筛膜的合成和应用是近年来的研究热点,特别是具有独特孔道结构的MFI型分子筛膜.但由于膜内有机模板剂在高温脱除时会导致膜产生缺陷,进而影响分子筛膜的应用.所以分子筛膜及分子筛晶体中有机模板剂的低温脱除工艺一直是研究者们致力解决的问题之一.本文系统考察了高硅ZSM-5分子筛晶体内有机模板剂(四丙基氢氧化铵,TPAOH)在H2/N2气氛下的低温裂解脱除规律,采用低温加氢裂解工艺,在350°C以下可有效脱除分子筛晶体孔道内的有机模板剂.通过对裂解后分子筛晶体的比表面积(BET)、热失重(TG)、傅里叶变换红外(FTIR)光谱和拉曼光谱表征证实,相比于空气和氮气气氛,含氢还原性气氛更有利于模板剂的低温脱除,脱除率随温度的升高而增加;280°C时,加氢裂解后晶体的BET比表面积已达到252 m2g-1,仍有少量有机残余物;350°C时,加氢裂解后晶体的BET比表面积可达到399 m2g-1,仅有微量无机碳残余物.此外,低温加氢裂解后的分子筛表面相对洁净,且氨气程序升温脱附(NH3-TPD)结果表明低温加氢裂解后的ZSM-5分子筛晶体具有相对较多的酸性位.

英文摘要:

Zeolite membranes, especially the MFI-type zeolite membranes, have attracted significant attention for decades because of their special properties. While organic templates such as tetrapropylammonium hydroxide (TPAOH) have typically been used for the synthesis of ZSM-5 zeolite and zeolite membranes, the templates remain trapped in the as-synthesized zeolite crystals. A common method for removing organic templates and generating porous frameworks is calcination; however, during this process, the channel structure may be affected. In particular, for ZSM-5 membranes, membrane defects may be produced and the separation efficiency therefore may decrease to some extent. In this study, the low-temperature hydrocracking of TPAOH in ZSM-5 zeolite crystals was studied under H2JN2, while N2 adsorption, thermogravimetric (TG) analysis, Fourier transform infrared (FTIR) spectroscopy, temperature-programmed desorption of ammonia (NH3-TPD), and Raman spectroscopy were used to characterize zeolite samples. The results show that the organic template in the pores of ZSM-5 can be effectively removed below 350 ℃ by low-temperature hydrocracking. Characterization analyses by BET specific surface area, TG, FTIR, and Raman spectroscopy demonstrated that a reducing atmosphere containing H2 was more conducive to template removal at low temperature than atmospheres of air or N2. The degree of template removal increased with temperature increasing. The BET surface area of the crystal after hydrocracking at 280 ℃ reached 252 m2·g-1, although a small amount of organic residue remained. Furthermore, after hydrocracking at 350 ℃, the BET surface area reached 399 m2·g-1, and only trace amount of inorganic carbon residue remained. In addition, the introduction of hydrogen at low temperatures could prevent coke deposits on acid sites and thus ZSM-5 zeolite crystals had greater numbers of acidic sites after low-temperature hydrocracking.

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期刊信息
  • 《物理化学学报》
  • 中国科技核心期刊
  • 主管单位:中国科学技术协会
  • 主办单位:北京大学化学与分子工程学院承办
  • 主编:刘忠范
  • 地址:北京大学化学楼
  • 邮编:100871
  • 邮箱:whxb@pku.edu.cn
  • 电话:010-62751724
  • 国际标准刊号:ISSN:1000-6818
  • 国内统一刊号:ISSN:11-1892/O6
  • 邮发代号:82-163
  • 获奖情况:
  • 中文核心期刊
  • 国内外数据库收录:
  • 俄罗斯文摘杂志,美国化学文摘(网络版),荷兰文摘与引文数据库,美国科学引文索引(扩展库),英国科学文摘数据库,日本日本科学技术振兴机构数据库,中国中国科技核心期刊,中国北大核心期刊(2004版),中国北大核心期刊(2008版),中国北大核心期刊(2011版),中国北大核心期刊(2014版),英国英国皇家化学学会文摘,中国北大核心期刊(2000版)
  • 被引量:24781