催化学报

催化学报 ›› 2018, Vol. 39 ›› Issue (8): 1418-1426.DOI: 10.1016/S1872-2067(18)63117-1

• 论文 • 上一篇    下一篇

高硅ZSM-5原粉的外表面改性及其在甲醇制丙烯反应中的应用

赵学斌a,b,c, 洪杨b,c, 王林英b, 樊栋b, 闫娜娜b,c, 刘晓娜b,c, 田鹏b, 郭新闻a, 刘中民b   

  1. a 大连理工大学化工学院, 宾州州立大学-大连理工大学联合能源研究中心, 精细化工国家重点实验室, 辽宁大连 116024;
    b 中国科学院大连化学物理研究所, 甲醇制烯烃国家工程实验室, 国家能源低碳催化与工程研发中心, 洁净能源国家实验室, 能源材料化学协同创新中心, 辽宁大连 116023;
    c 中国科学院大学, 北京 100049
  • 收稿日期:2018-05-31 修回日期:2018-06-06 出版日期:2018-08-18 发布日期:2018-07-04
  • 通讯作者: 郭新闻, 田鹏, 刘中民
  • 基金资助:

    国家自然科学基金（21676262）；中国科学院前沿科学重点研究计划（QYZDB-SSW-JSC040）.

External surface modification of as-made ZSM-5 and their catalytic performance in the methanol to propylene reaction

Xuebin Zhaoa,b,c, Yang Hongb,c, Linying Wangb, Dong Fanb, Nana Yanb,c, Xiaona Liub,c, Peng Tianb, Xinwen Guoa, Zhongmin Liub   

  1. a State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China;
    b National Engineering Laboratory for Methanol to Olefins, State Energy Low Carbon Catalysis and Engineering R & D Center, Dalian National Laboratory for Clean Energy, Collaborative Innovation Center of Chemistry for Energy Materials(iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    c University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-05-31 Revised:2018-06-06 Online:2018-08-18 Published:2018-07-04
  • Contact: 10.1016/S1872-2067(18)63117-1
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21676262), and the Key Research Program of Frontier Sciences, CAS (QYZDB-SSW-JSC040).

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摘要：

使用来源广泛的甲醇为原料制取丙烯，是对石油路线生产丙烯的重要补充.尽管以ZSM-5分子筛为催化剂的固定床甲醇制丙烯（MTP）技术已经实现了工业应用，但进一步提高催化剂的寿命和丙烯的选择性一直是学术界和工业界的研究热点.MTP过程作为典型的酸催化反应，积碳是催化剂失活的主要原因，由于ZSM-5分子筛十元环孔道的空间限制作用，积碳主要分布在外表面.因此，消除外表面的酸性位点对延长催化剂的寿命至关重要，但修饰外表面酸性位点的同时往往会改变样品的其他性质，如孔径、整体酸量等.本文分别使用Na2H2EDTA和H3PO4处理高硅ZSM-5分子筛原粉（微孔内含有机模板剂）来选择性地减小或消除外表面的酸密度，而不影响分子筛内部的性质，并考察了处理后样品的MTP性能.使用N2物理吸附、SEM和27Al MAS NMR表征样品的织构性质、形貌和Al原子的化学环境，XPS和三异丙苯裂解实验表征外表面的硅铝比和酸密度.表征结果表明，Na2H2EDTA处理虽然可以选择性的脱除表面Al原子，但会在外表面产生新的酸点（可能是硅巢）.H3PO4处理虽然不能脱除表面的Al原子，但外表面残留的P物种能够有效的减小酸密度.MTP评价结果表明，H3PO4处理能够有效的延长催化剂的寿命和维持丙烯的选择性，这是因为H3PO4处理既提高了外表面的容碳能力，也抑制了积碳沉积的速率.Na2H2EDTA处理仅能增加外表面的容碳能力，所以其只能延长催化寿命.通过进一步优化H3PO4后处理的条件，处理后的ZSM-5样品的催化寿命可以延长至前体的1.5倍，同时，丙烯的选择性也略有提高，并且在失活前维持增加的趋势.

关键词: 甲醇制丙烯, ZSM-5分子筛, 改性, 磷酸, 乙二胺四乙酸

Abstract:

Post-synthetic treatment of high-silica as-made ZSM-5 with organic template in the micropores was explored to reduce/remove the external surface acid density of ZSM-5. It is found that Na2H2EDTA treatment can selectively remove the surface Al atoms, but generates new acid sites (likely silanol nests) on the external surface. H3PO4 treatment is unable to remove surface Al atoms, while small amount of P is left on the external surface, which effectively decreases the acid density. The catalytic performance of the resultant materials is evaluated in the methanol conversion reaction. H3PO4 treatment can effectively improve both the catalytic lifetime and the stability of propene selectivity. This occurs due to a combination of the increased tolerance to the external coke deposition and the depressed coking rate (reduced side reactions). Na2H2EDTA treatment only prolongs the catalytic lifetime, resulting from the improved tolerance to the external coke deposition. Under the optimized H3PO4treatment condition, the resultant ZSM-5 gives a catalytic lifetime of about 1.5 times longer than the precursor. Moreover, the propene selectivity is improved, showing a slight increasing trend until the deactivation.

Key words: Methanol to propene, ZSM-5 zeolite, Modification, Phosphoric acid, Ethylenediamine tetraacetic acid