Investigation Of Catalysts For Isobutane Direct Dehydrogenation

As an important basic petrochemical raw material,isobutane is widely used in the preparation of substantial high value-added fine chemical products.The traditional isobutene preparation technology can't meet the huge market demand.Because of the abundant resources of isobutane in China,the preparation of isobutene with high added value by using cheap isobutane has broad market prospect.At present,the commercial dehydrogenation catalysts are mainly Pt-Sn/Al2O3 catalyst and Cr2O3/Al2O3 catalyst.Among them,the Pt based catalyst has high cost and high operating process requirements,while the CrOx based catalyst has the disadvantages of easy deactivation and six chromium toxicity.Therefore,the development of a low cost and efficient catalyst is the key to the dehydrogenation of isobutane.In this paper,a kind of supported iron-based catalyst was prepared,and its catalytic performance in isobutane dehydrogenation was studied.The main contents are as follows:Firstly,the catalyst was optimized by optimizing the loading capacity of Fe2O3,adding different additives,and the catalyst was supported on different carriers.The experimental results show that Fe2O3-K2O/?-Al2O3 catalyst has high catalytic activity and selectivity,the loading of Fe2O3 and K2 O was 10 wt.% and 1.0 wt.%,respectively.Secondly,the effect of the content of K2 O on the dehydrogenation performance of Fe2O3-K2O/?-Al2O3 catalyst was investigated.Moreover,N2 adsorption-desorption,X-ray diffraction(XRD),temperature-programmed reduction(TPR),temperature-programmed oxidation(TPO),Thermogravimetric Analysis(TG),isobutene temperature-programmed desorption(TPD)and scanning electron microscope(SEM)were used to investigate the effect of K2 O on the dehydrogenation performance.The results show that the introduction of K2O can effectively improve the carbon deposition resistance of the catalyst.At the same time,the addition of K2O can promote the removal of isobutene from the catalyst during the reaction process,so as to improve the selectivity of the catalyst.Thirdly,the effects of reaction temperature,feed velocity and molar ratio of feed gas on the dehydrogenation performance of the catalyst were investigated.The optimum reaction conditions were determined: temperature 600 ?,catalyst weight 0.4 g,i-C4H10/N2 molar ratio =1.0,GHSV=1440 h-1.Meanwhile,the service life of the catalyst was investigated.It was found that the catalyst had good dehydrogenation performance after dehydrogenation of 100 h.Finally,the induction period of catalyst in dehydrogenation reaction was studied.The results show catalyst deactivation is mainly due to carbon deposition,and the Fe3C formed on the catalyst is the active site of the catalyst.