物理化学学报 >> 2015, Vol. 31 >> Issue (7): 1374-1382.doi: 10.3866/PKU.WHXB201504302

催化和表面科学 上一篇    下一篇

氢氧化钠-氟硅酸铵改性HZSM-5催化甲醇制丙烯

胡思1, 张卿2, 尹琪2, 张亚飞2, 巩雁军2, 张瑛1, 吴志杰2, 窦涛2   

  1. 1 中国石油大学(北京)理学院材料科学与工程系, 北京102249;
    2 中国石油大学(北京)中国石油天然气集团公司催化重点实验室, 北京102249
  • 收稿日期:2015-01-07 修回日期:2015-04-30 发布日期:2015-07-08
  • 通讯作者: 窦涛 E-mail:doutao@cup.edu.cn
  • 基金资助:

    国家重点基础研究发展规划项目(973) (2012CB215002)及国家自然科学基金(21206192)资助

Catalytic Conversion of Methanol to Propylene over HZSM-5 Modified by NaOH and (NH4)2SiF6

HU Si1, ZHANG Qing2, YIN Qi2, ZHANG Ya-Fei2, GONG Yan-Jun2, ZHANG Ying1, WU Zhi-Jie2, DOU Tao2   

  1. 1 Department of Materials Science and Engineering, College of Science, China University of Petroleum-Beijing, Beijing 102249, P. R. China;
    2 The Key Laboratory of Catalysis, China National Petroleum Corporation, China University of Petroleum-Beijing, Beijing 102249, P. R. China
  • Received:2015-01-07 Revised:2015-04-30 Published:2015-07-08
  • Contact: DOU Tao E-mail:doutao@cup.edu.cn
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2012CB215002) and National Natural Science Foundation of China (21206192).

摘要:

首次将氢氧化钠-氟硅酸铵复合改性应用于甲醇制丙烯(MTP)催化剂的制备中. 采用X射线衍射(XRD)、X 射线荧光光谱(XRF)、N2吸附-脱附、透射电镜(TEM)、NH3程序升温脱附(NH3-TPD)等测试技术对改性前后HZSM-5分子筛催化剂的晶体结构、元素组成、织构性质、酸性质等进行了表征. 结果表明, 采用氢氧化钠-氟硅酸铵复合改性不仅可以提高催化剂的介孔孔容, 还能有效调变催化剂的酸性. 复合改性方法成功克服了单纯碱处理容易破坏分子筛的骨架结构、单纯氟硅酸铵改性因受扩散限制仅限于修饰分子筛外表面的缺点. 改性后HZSM-5 分子筛催化剂在MTP反应中的诱导期大大缩短, 在常压、反应温度为470 ℃、甲醇质量空速(WHSV)为2 h-1的条件下, 初始丙烯选择性高达43%. 此外, 复合改性后HZSM-5分子筛在MTP反应中的稳定性大幅改善, 催化寿命延长至本体样品的3倍.

关键词: 碱处理, 氟硅酸铵, 复合改性, 介孔, 酸性, 甲醇制丙烯

Abstract:

A sequential modification by sodium hydroxide (NaOH) and ammonium hexafluorosilicate ((NH4)2SiF6) solution was used for preparing MTP (methanol to propylene reaction) catalyst for the first time. The parent and modified samples were characterized by diverse techniques including powder X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, N2 adsorption-desorption, transmission electron microscopy (TEM), and NH3 temperature-programmed desorption (NH3-TPD). The effect of modification on the physicochemical properties, such as framework, chemical composition, texture, and acidity, were investigated in detail. The results showed that the mesopore volume of the zeolite catalyst increased significantly following sequential NaOH and (NH4)2SiF6 modification. The acidity was also modulated effectively. The composite modification method successfully overcame the disadvantages associated with individual simple alkali and (NH4)2SiF6 treatments. For instance, using a simple alkali treatment would destroy the framework of the zeolite easily, whereas using a simple (NH4)2SiF6 treatment would only modify the external surface of the zeolite owing to the limited diffusion of the ammonium hexafluorosilicate molecule. When used in MTP reaction, the induction period of the composite modified sample was greatly shortened, and the initial selectivity for propylene increased to 43% under the following operating conditions: T=470 ℃, p=0.1 MPa (pMeOH=50 kPa), and weight hourly space velocity (WHSV)=2 h-1. Moreover, the composite modified zeolite catalyst exhibited significantly improved stability, and the catalytic lifespan was triple that of the parent sample.

Key words: Alkali treatment, Ammonium hexafluorosilicate, Composite modification, Mesopore, Acidity, Methanol to propylene

MSC2000: 

  • O643.3