Highly Dispersed CrO<i><sub>x</sub></i> Nanoparticle-Modified NaZSM-5 for Dehydration of Methanol to Dimethyl Ether
Tianyu Mo, Miao Yu, Hongyan Li, Songnan Li, Bin Lü, Jingxiang Zhao, Qinghai Cai
Abstract
In this work, CrO x nanoparticle- and H + -modified NaZSM-5 was prepared by impregnating in chromium nitrite aqueous solution to form Cr/HNaZSM-5 composites. They were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible (UV–vis), XPS, 29 Si and 27 Al MAS NMR, NH 3 –(CO 2 −) TPD, and N 2 adsorption/desorption measurements, revealing that the Cr/HNaZSM-5 composites possessed moderate surface acidity and basicity due to the Cr species or H + partly substituting for the counter Na + and highly dispersed CrO x nanoparticles on zeolites. The obtained composites thus provided promoting performance for catalyzing methanol dehydration to dimethyl ether with >90% conversion and ca. 100% selectivity at a lower reaction temperature. The promoted performance comes from acidic and basic sites for activating methanol to produce CH 3 + and CH 3 O – intermediates, respectively. Moreover, as the catalyst works in succession over 500 h, the reactivity abatement is not found, suggesting excellent running stability.