Study On Bismuth Molybdenum-based Catalysts For Oxidative Dehydrogenation Of 1-Butene To 1,3-Butadiene

1,3-Butadiene is an important petrochemical raw materials and one of the most important monomer for production of polymer composite materials. Furthermore, it can react with a variety of compounds by copolymerization to manufacture various synthetic rubber and synthetic resins, such as butadiene rubber, styrene-butadiene rubber, nitrile rubber, and etc. In addition,1,3-butadiene is also raw materials of a variety of coatings and organic chemical. With the rapid development of automobile industry and more tire production, the global demand for 1,3-butadiene has increased significantly in the last decades. There are two main methods for production of 1,3-butadiene. One is to extract 1,3-butadiene from a mixed C4 hydrocarbons byproduct of ethylene cracking reactor, the other one is from oxidative dehydrogenation of C4 hydrocarbons, which is supplied by the byproduct of refinery, coal chemical industry and bio-based chemical industry. However, extraction method is largely dependent on oil. The dehydrogenation of 1-butene to 1,3-butadiene can not only break the dependence on oil resources but also use C4 fraction efficiently. The preparation of high activity and stability of the catalyst is the key factor to oxidative dehydrogenation of 1-butene to 1,3-butadiene process. The main contents of the dissertation are as followings:This dissertation aims to improve the BiMo based catalyst to enhance the catalytic activity of the catalyst. Two aspects are investigated in this dissertation. On the one hand, three components catalysts were prepared by the introduction of heteroatoms in BiMo catalyst using coprecipitation method. In other word, Bi or Mo in BiMo catalyst is replaced by heteroatoms to investigate the change of catalytic performance. Firstly, BiMoVx with different V content was investigated by partial substitution for Mo in BiMo catalyst with V element. Secondly, Bi element in BiMo catalyst was also conducted by partially substitution with Zr, La, Ce element, respectively. On the other hand, we combined BiMo and CNTs catalyst to synthesize composite catalyst by sol-gel method, and the prepared catalyst exhibits good activity and stability in the reaction.BiMoVx catalysts with different V content were prepared by coprecipitation method to explore the effects of V elements on catalytic activity. The formation of new crystal phase was confirmed by XRD. Meanwhile, the change of oxygen mobility was confirmed by XPS and TPRO. Compared with other composition, BiMoV0.15 shows the superior catalytic activity. In addition, the mechanism of oxygen mobility is preliminarily proposed by investigating the change of metal valence during the reaction.Bi element in BiMo catalyst was substituted partially with Zr by co-precipitation to produce three-component catalyst. The changes in the crystal structure of the catalyst were characterized by XRD. TEM and N2 adsorption were conducted to explore the changes of pore structure of the catalyst. We also observed that the introducation of Zr element in BiMo catalyst exhibited porous structure and improved surface area of the catalyst effectively. Furthermore, activity and oxygen mobility of the catalyst was studied with the XPS and TPRO.Three-component BiMoLa catalysts were prepared by coprecipitation method. The influence of the La content over catalytic activity and oxygen mobility of the catalyst was studied by H2-TPR and TPRO. BiMoLao.2 exhibits the good catalytic activity and stability, and dynamics model of the reaction process over BiMoLao.2 catalyst was established and optimized. Compared to the BiMo catalyst, the activation energy over BiMoLao.2 catalyst is reduced effectively, making the reaction happen more easily.Three component BiMoCe catalysts were synthesized by partial substitution Bi with Ce in BiMo catalyst. The change of oxygen mobility was investigated by TPRO and XPS. BiMoCeo.2 shows the best oxygen mobility and catalytic activity in this reaction, and kinetics model of the reaction process was built and optimized. In addition, the mechanism of oxygen migration was explored. The pulse experiment was conducted and the results show that bismuth molybdenum-based catalysts and Ce(MoO4)2 acted as the role of acceptor and donor of oxygen, respectively.BiMo/CNTs composite catalyst was prepared by sol-gel method. XPS characterization results indicate that the introducation of Bi and Mo can improve oxygen mobility effectively. Composite catalyst exhibits excellentlly catalytic performance in the oxidative dehydrogenation of 1-butene. The 0.018(BiMo)/CNTs composite catalyst shows the best catalytic activity and the yield of butadiene is 52.2% under anhydrous conditions. TEM results reveal BiMo uniformly dispersed on CNTs. The composite catalyst under anhydrous reaction conditions exhibits good catalytic activity and stability.