Study On Direct Dehydrogenation Of Isobutane Over Metal Modified Vanadium-based Catalysts

The direct dehydrogenation of isobutane to isobutene is one of the important ways to broaden the source of isobutylene and increase the utilization of carbon tetra-alkanes.The selection and development of catalysts is an important step in industrial production.At present,platinum-and chromium-based catalysts are produced industrially.Non-precious metal catalysts such as vanadium-based catalysts have good stability and reaction performance,similar to those of the commercial catalysts.Hence,research on these catalysts has received significant attention.In this study,different additives were selected to modify the V₂O₅/Al₂O₃-based catalysts,and the effects on their properties and reactivities were investigated.The loading of vanadium oxide in the vanadium oxide catalysts supported by alumina were explored first,and the optimal result was obtained with 12 wt%loading.Based on this,Sn O₂ was selected as an auxiliary agent for the characterization of the catalyst and determination of the catalytic performance.It was found that the addition of an appropriate amount of Sn O₂ changed the interaction between the vanadium species and the carrier and reduced the valenc e state of the former.The performance evaluation revealed that 1 wt%promoter imparted the best overall catalytic performance.Further analysis showed that the addition of Sn O₂ could change the existing form of vanadium species on the surface of the catalyst,increase the degree of dispersion,and improve the dehydrogenation activity.At the same time,the choice of hydrogen as a diluent could effectively reduce the carbon deposition.The catalyst was also modified with K₂O and Mg O.The addition of the auxiliary agent rendered the surface of the catalysts acidic,allowing interaction between the vanadium species and the carrier.This was evident from the determination of the electron binding energy of the element and the catalytic performance.The KSV-3catalyst with 0.2 wt%added potassium exhibited better reaction selectivity and stability,and the reaction conversion and selectivity after 7 h were 41.8%and 90.5%,respectively.Finally,the influence of the reaction conditions and the long-term stability of the KSV-3 catalyst were investigated.It was found that the catalyst had a good stability for 24 h and was able to maintain the reaction conversion and selectivity at greater than 40%and 90%,respectively,up to 11 h.