Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (02): 358-364.doi: 10.3866/PKU.WHXB201211143

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Effects of Na+ in Dilution Steam and Coke Deposition on Catalytic Performance of Methanol-to-Propylene Catalysts

WANG Feng1, YAN Shu-Jun1, YONG Xiao-Jing1, LUO Chun-Tao1, ZHANG Qing2, WEN Peng-Yu2, GONG Yan-Jun2, DOU Tao2   

  1. 1 Research and Development Division, Shenhua Ningxia Coal Industry Group Co. Ltd., Yinchuan 750411, P. R. China;
    2 The Key Laboratory of Catalysis of CNPC, China University of Petroleum-Beijing, Beijing 102249, P. R. China
  • Received:2012-09-12 Revised:2012-11-13 Published:2013-01-14
  • Supported by:

    The project was supported by the International S&T Coopperation Program of China (2010DFB40440) and S&T Programs of Ningxia, China (Industrial Operation and Key Technology Research for 500000 t/a Coal-Based Polypropylene Plant).

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Abstract:

The effects of Na+ in dilution steam and coke deposition on the physicochemical properties andcatalytic performance of ZSM-5 catalysts for the methanol-to-propylene (MTP) reaction were investigated.The deactivated and regenerated catalysts were characterized by means of X-ray diffraction (XRD),scanning electron microscopy (SEM), X-ray fluorescence (XRF) spectrum, nitrogen adsorption/desorption,temperature-programmed desorption of ammonia (NH3-TPD), and thermogravimetry (TG). Their catalyticperformance for MTP reaction was tested in a continuous flow fixed-bed micro-reactor at 470℃, 101325Pa, and with methanol weight hourly space velocity (WHSV) in the range of 1.0-3.0 h-1. The resultsindicated that the catalyst crystal structure and morphology was not significantly altered after 970 h onstream. In the MTP reaction, Na+ in the dilution steam can easily enter the pore channels of the catalyst,and partially replace H protons, thereby gradually decreasing the amount of acidity and acid strength of thecatalyst, which eventually causes deactivation. In addition, coke deposits on the catalyst surface blocking its micropores are the main reason for deactivation of the MTP catalyst. Coke deposits are mostlyeliminated through the burning charcoal regeneration process. The effect of framework dealumination fromthe catalyst by steam in the MTP process is slow but more serious. Through regeneration and ionexchange process, the catalytic activity of the deactivated catalyst can be fully restored. The conversion ofmethanol is consistently above 99%, and propylene selectivity is greater than 46% even after 470 h onstream. With increasing reaction time, the propylene selectivity gradually increases, while ethyleneselectivity gradually decreases.

Key words: Methanol-to-propylene catalyst, Coke deposition, Regeneration, Dilution steam