Para-selective methylation of toluene with methanol over nano-sized ZSM-5 catalysts: Synergistic effects of surface modifications with SiO2, P2O5 and MgO
发布时间：2019-03-09
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- 论文类型：
- 期刊论文
- 发表时间：
- 2014-09-15
- 发表刊物：
- MICROPOROUS AND MESOPOROUS MATERIALS
- 收录刊物：
- Scopus、EI、SCIE
- 文献类型：
- J
- 卷号：
- 196
- 页面范围：
- 18-30
- ISSN号：
- 1387-1811
- 关键字：
- Nano-sized ZSM-5; Single modification; Multiple modification; Para-selectivity; Synergistic effect
- 摘要：
- The nano-sized ZSM-5 catalysts were modified by surface coating with SiO2, P2O5, MgO and their combinations; the catalytic properties were investigated in the shape-selective methylation of toluene with methanol. The catalysts were characterized by XRD, XRF, N-2 adsorption-desorption, temperature programmed desorption of ammonia (NH3-TPD), Fourier-transform infrared spectra of adsorbed pyridine/2,6-di-tert-butylpyridine, and adsorption of n-hexane/cyclohexane. The passivation of Lewis acid sites occurs prior to that of the Bronsted acid sites over ZSM-5 modified by SiO2, while P2O5 or MgO preferentially neutralizes the Bronsted acid sites of ZSM-5. The deposition of MgO is more efficient in passivating the acid sites and narrowing the pore openings, compared to SiO2 or P2O5 modification with the same oxide content (<9 wt%). The single modification could not completely passivate the external surface acid sites and simultaneously narrow the pore openings to a proper extent; so the selectivity to para-xylene does not exceed 90% even at the highest oxide loading. The multiple modification by SiO2, P2O5 and MgO, with a suitable sequence can efficiently eliminate external surface acid sites, and simultaneously narrow the pore openings, which led to a higher para-selectivity (similar to 98%). The combined modification with SiO2, P2O5 and MgO in a proper sequence can lead to a synergistic effect for tailoring the acid property and pore mouth of the catalyst, thus enhancing the para-selectivity to similar to 98% and improving catalytic stability, as demonstrated by flow test for 1000 h on stream. (C) 2014 Elsevier Inc. All rights reserved.
- 第一作者
- Tan, Wei
- 合写作者
- Wang, Yiren,Song, Chunshan,Liu, Min,Zhao, Yan,Hou, Keke,Wu, Hongyu,Zhang, Anfeng,Liu, Haiou,Guo, Xinwen
- 通讯作者
- Song, CS (reprint author), Dalian Univ Technol, Sch Chem Engn, PSU DUT Joint Ctr Energy Res, State Key Lab Fine Chem, Dalian 116024, Liaoning Provin, Peoples R China.