Study On Iron-based Catalysts And Process Conditions Of C₄ Alkanes Dehydrogenation

In this paper,the n-butane and iso-butanes mixed n-butanes dehydrogenation over iron-based catalyst were investigated.The results showed that the iron-based catalyst was rather active both for the n-butane and mixed-butanes dehydrogenation reaction.The optimized catalyst composition determined by catalyst performance testing showed that the iron loading was 5%¹5%,and the additive was M1 with Fe:M1 molar ratio of 2:1.The suitable C₄ alkane dehydrogenation reaction conditions were as follows: temperature of 610 ?⁶30 ?,GHSV of 100 ml/?g·h?²00 ml/?g·h?and steam to gas molar ratio of 0.22.A 10 to 17 hours induction time was observed by the catalyst testing.The induction time catalyst was characterized by XRD,H2-TPR and TPO.The results show the crystal phase of iron-containing component is spinel Fe3O4,the catalyst has good olefins selectivity when carbon existed.This was identified by hydrogen reduced Fe2O3/Al2O3 catalyst and Fe2O3/C catalyst.The results indicate that the dehydrogenation active site may be the combination of Fe3O4 and C.Furthermore,the introduction time could be avoided by controlling the coke content on the spent catalysts by regeneration of removing part of coke of the catalyst.The results of stability test showed that the catalyst can meet the demands of recycling operation.The conversion of mixed butanes decreased merely 3%after 100 h running and the selectivity of total olefins remained stable at 90%.The catalytic performance was recovered and the induction period could be effectively controlled by removing part of coke of the catalyst.The results show that coke control is the key of the C₄ alkane dehydrogenation over Fe-based catalyst,and the Fe3O4-C is the active center of the catalyst for C₄ alkane dehydrogenation.