High propylene selectivity in methanol conversion over metal (Sm, Y, and Gd) modified HZSM-5 catalysts in the methanol to propylene process

Abstract

A protonated form of Zeolite Socony Mobil-5 (H-ZSM-5) catalyst (with Si/Al = 200) was synthesized through a hydrothermal method from various sources of silica, including Ludox, silicic acid, and tetraethyl orthosilicate. We also investigated the effect of loading the catalyst with yttrium (Y), samarium (Sm), and gadolinium (Gd), respectively, on the acidic properties of the catalyst. We compared the catalytic performance of the catalysts with different loadings in methanol to hydrocarbon conversion. The catalysts were characterized using X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area analysis measurements, thermogravimetric analysis, and temperature-programmed desorption. Among the metal-loaded Ludox-based H-ZSM-5 catalysts (LHZs), the Sm/LHZ catalyst had the best performance with 68.8 % propylene selectivity due to its high amount of weak and intermediate acid sites at 480 degrees C, WHSV =1 h-1 in a methanol to propylene conversion. However, the Gd-LHZ catalyst significantly increased the selectivity toward ethane and propane during the conversion.