Adsorption and diffusion of benzene and thiophene over Y/MCM-41 composite zeolite

Y/MCM-41 composite molecular sieve was successfully synthesized using ion exchange method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and infrared (IR) etc. Adsorption and diffusion behaviors of benzene and thiophene on NaY, Si-MCM- 41, NaY/Si-MCM-41 mixtures, and Y/MCM-41 composite molecular sieve were systematically studied to obtain adsorption isotherm and relative diffusion coefficient. It was found that the adsorption mechanisms of benzene and thiophene were different. The adsorption of benzene was mainly by physical adsorption, while π electrons played a most important role in the adsorption of thiophene. An inflection appears around the pressure of 30 mbar in all adsorption isotherms of benzene and thiophene. The pore filling occurs in the microporous below 30 mbar, but above 30 mbar the adsorption is mainly the capillary condensing in mesoporous pore. The acid amount and acid strength of adsorbent had a great influence on the adsorption capacity of thiophene, but had little effect on benzene. Both benzene and thiophene were preferred to be adsorbed in micro-porous channels of NaY, Si-MCM-41, NaY/Si-MCM-41 mixtures, and Y/MCM-41. The diffusion coefficient of thiophene on NaY, Si-MCM-41, NaY/Si-MCM-41 mixtures, and Y/MCM-41 is larger than that of benzene. Static desulfurization performance of different adsorbents followed the order below: Y/MCM-41 > NaY > YM (0.8) > YM (0.2) > YM (0.4) > YM (0.6) > Si-MCM-41. © 2013 by American Scientific Publishers.