Effect of Magnesium Oxide Modification on the Catalytic Performance of Nanoscale HZSM-5 Zeolite for the Conversion of Methanol to Propylene

Abstract

A series of nanoscale HZSM-5 zeolites modified with different amounts (0-8%, w) of magnesium were prepared by an impregnation method and characterized by X-ray diffraction (XRD), Al solid state magic angle spinning nuclear magnetic resonance (27Al MAS NMR), N2-adsorption/desorption, temperature-programmed desorption of NH3 (NH3-TPD), and pyridine adsorption Fourier transform infrared (FT-IR) methods. The conversion of methanol to propylene was tested in a continuous flow fixed-bed microreactor at atmospheric pressure, 500 ℃, and a methanol space velocity (WHSV) of 1.0 h-1. The results indicated that with an increase in the amount of Mg, the selectivity of propylene and butene increased but those of methane, ethylene and aromatics decreased consistently. With an increase in the amount of Mg the stability of the catalyst was found to increase initially, pass through a maximum at 2% and then decrease with higher amounts of Mg. The effect of modification with magnesium oxide on the catalytic performance of the nanoscale HZSM-5 zeolite for the conversion of methanol to propylene can be attributed to the resultant changes in acidity and texture of the modified nanoscale HZSM-5 zeolites.