Modified HZSM-5 zeolites for intensifying propylene production in the transformation of 1-butene

Effect of lanthanum and phosphorus on the aromatization activity of Zn/ZSM-5 in FCC gasoline upgrading

The aim of this study is to investigate the promotional effect of Fe–Mo, Co–Mo, and Ni–Mo bimetallic additives on the activity and stability of H-ZSM-5 zeolite for isomerization of 1-hexene. The catalysts were synthesized by wet-impregnation method and characterized by XRD, FTIR, BET, ICP-AES, HRSEM-EDS, HRTEM, H2-TPR, NH3-TPD, and pyridine-DRIFT analysis. The isomerization of 1-hexene was carried out in a micro-scale system under the conditions: T = 250 °C, P = 4.0 MPa, FR = 0.1 ml/min, WHSV = 1 h−1. The conversion of 1-hexene over the 4 g bed of catalyst was in the range of 95–97% after 74 h time-on-stream with cis-3-hexene and cis-2-hexene as the principal products. It was shown that the appearance of the new strong Lewis acid sites, decreases the ratio of Bronsted/Lewis acid sites. Increase of the weak Lewis acid sites in the 2.5 wt%Ni2.5 wt%Mo-ZSM-5 catalyst facilitated the isomerization of 1-hexene and showed higher C6 olefin selectivity (48.4 mol%), research octane number (99.7), and bromine number (148.3) than other studied catalysts.

1-hexene isomerization over bimetallic M-Mo-ZSM-5 (M: Fe, Co, Ni) zeolite catalysts: Effects of transition metals addition on the catalytic performance

The catalytic dehydration of ethanol into ethylene was studied over 5 wt% Mo/HZSM-5 prepared by impregnation. The effect of calcination temperature on the structure, acidity and catalytic performance of the catalysts was investigated by XRD, N2 adsorption, NH3-TPD and TG. A correlation between the catalytic performance of Mo modified catalysts and the amount of weak and medium acidity was observed. It was found that 5 wt% Mo/HZSM-5 catalyst calcined at 500 °C exhibited the highest weak and medium acidity and much better catalytic performance in ethanol dehydration reaction compared with HZSM-5. TPR characterization showed that the Mo species on the external surface of HZSM-5 was easier to be reduced during the reaction. Combining quantitative analyses of NH3-TPD and H2-TPR profiles of fresh and used catalysts revealed that the decrease of weak and medium acidity could be correlated with the reduction of Mo species. It is proposed that reduction of Mo species caused the decrease of weak and medium acidity, which contributed to activity drop at the initial reaction stage.

Kunyuan Wang

Papers

Effect of acidity on n-octene reaction over potassium modified nanoscale HZSM-5