Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (11): 2705-2712.doi: 10.3866/PKU.WHXB201207171

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Catalytic Conversion of Methanol to Propylene over (NH4)2SiF6-Modified Nanosized HZSM-5 Zeolite

HU Si1, ZHANG Qing1, XIA Zhi2, GONG Yan-Jun1, XU Jun3, DENG Feng3, DOU Tao1,2   

  1. 1 The Key Laboratory of Catalysis of CNPC, China University of Petroleum-Beijing, Beijing 102249, P. R. China;
    2 Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, P. R. China;
    3 Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, P. R. China
  • Received:2012-05-25 Revised:2012-07-17 Published:2012-10-17
  • Supported by:

    The project was supported by the State Key Development Program for Basic Research of China (973) (2012CB215002), National Natural Science Foundation of China (10979076, 21176255), and International Science and Technology Cooperation and Exchange Program of China (2010DFB40440).

Abstract:

(NH4)2SiF6-modified nanosized HZSM-5 zeolite was prepared and investigated as a catalyst formethanol to propylene conversion. The effects of this modification on the framework, textural propertiesand acidity of both the parent and the modified HZSM-5 zeolite were investigated by powder X-raydiffraction (XRD), 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), X-rayfluorescence (XRF), X-ray photoelectron spectroscopy (XPS), N2 adsorption, transmission electronmicroscopy (TEM), temperature-programmed desorption of ammonia (NH3-TPD), and infraredspectroscopy of adsorbed pyridine (Py-IR). The catalytic performance of these materials on the methanolto propylene (MTP) conversion process was tested under operating conditions of T=450℃, p=0.1 MPa(pMeOH=50 KPa) and WHSV=1 h-1. The results showed that surface aluminum on the nanosized ZSM-5zeolite could be selectively removed by the (NH4)2SiF6 solution and that the number of acidic sites on theHZSM-5 zeolite gradually decreased with increasing (NH4)2SiF6 concentration. Moreover, after modification with an optimally concentrated (NH4)2SiF6 solution, an obvious increase in specific surface area as well asmesopore volume was observed for the nanosized HZSM-5 with a resulting dramatic improvement in thecatalytic performance of this material for the MTP reaction. Both the propylene selectivity and propylene/ethylene (P/E) mass ratio resulting from use of the modified HZSM-5 increased significantly to 45.1% and8.0, as compared to results of 28.8% and 2.6 obtained with the original material. In addition, the catalyticlifespan of the modified zeolite was double that of the original.

Key words: Nanosized ZSM-5, Dealumination, Pore structure, Acidity, Propylene selectivity, Catalytic lifetime

MSC2000: 

  • O643.3