The ethylbenzene hydrogenation over Ni-H_3PW_(12)O_(40)/SiO_2 in the presence of thiophene

摘要

Ni-HPW/SiO_2 catalysts with H_3PW_(12)O_(40) (HPW) loading in the range of 0.1-8% were prepared by a modified sol-gel method. The as-prepared catalysts with bimodal pore distribution not only possess relatively large pore and surface area, but exhibit high activity for ethylbenzene hydrogenation even in the presence of thiophene up to 640 ppm. It is evident that nickel oxide particles are small and well-dispersed on the surface of these catalysts from X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization. The results of temperature-programmed reduction of hydrogen (H_2-TPR), temperature-programmed desorption of hydrogen and ammonia (H_2 and NH_3-TPD) also strongly suggest the interaction between Ni component and HPW takes place, and consequently results in remarkable H_2 spillover and considerable increase of acidic site concentration of Ni-HPW/SiO_2 catalysts. Further, the results of Fourier transform infrared spectroscopy (FT-IR) with pyridine adsorption also show that most of the acid sites are related to Lewis acid and the metal Ni species on the surface of catalysts are therefore prone to be electron-deficient. It is confirmed that HPW plays a critical role in the improvement of sulfur resistance for Ni-based catalysts.