Technology Research On Oxidative Dehydrogenation Process Of Butene To Butadiene

Butadiene(BD) is a basic raw material of petrochemical industry, it’s also an important monomer of synthetic rubber and polymer materials which is second only to ethylene and propylene. Butadiene is mainly obtained from the extraction of mixed C4 fraction by ethylene cracking unit, the technology is the main method for butadiene’s production, and the second method to obtain butadiene is the dehydrogenation of refinery mixed C4 fraction, According to the statistics, using the extraction technology can produce 92% butadiene in the world. In recent years, with the rapid development of the world automobile industry and increasing demand for synthetic rubber, the situation of shortage for butadiene is getting worse and worse. Domestic enterprises and foreign companies pay attention to the dehydrogenation technology of n-butane and n-butene again.Our country is rich in butene resources but lack in butadiene resources. Therefore, using the technology for oxidative dehydrogenation of butene to butadiene can not only make high value-added butadiene which is good for reducing the pressure on market demand, but also can improve enterprises’ competitiveness. In the background of demand for the technology, Lanzhou Research Center of Petro China cooperates with Lanzhou Institute of Chemical Physics has been developed the technology for oxidative dehydrogenation of butene to butadiene, providing a technology for butadiene’ production with high economic efficiency but low processing costs to meet enterprises’ technical needs. In conclusion this paper carries out the research on the oxidative dehydrogenation of butene to butadiene.Oxidative dehydrogenation of butene to butadiene is carried out in a 200 m L fixed bed reactor, using a new generation of butene oxidative dehydrogenation catalysts LH-39 loaded in the bed with a capacity of 50 mL which is developed by Lanzhou Institute of Chemical Physics. As the experiment materials, the mixed C4 fraction with the molar proportion of 1-C4H8 is 62.34%, t-C4H8 is 12.13%, c-C4H8 is 16.88%, i-C4H8 is 0.65%, n-C4H10 is 6.88%. Under the conditions of reaction temperature is 340~410℃,reaction pressure to atmospheric pressure, volume space velocity of butene is 400h-1, molar ratio of oxygen to butene is 0.68~0.72, molar ratio of water to butene is 12~17, we discover the effects of temperature, molar ratio of oxygen to butene, molar ratio of water to butene, volume space velocity of butene, ratio of raw material and other process conditions on the performance of LH-39 catalysts. The results show that with the increasing reaction temperature the conversion of butene increases, the optimum reaction temperature is between 380~390℃, the process react heavily and emit a lot of heat in the range of the temperature. The conversion of butene rate up to 85%, butadiene selectivity is 93%, butadiene yield up to 79%, the selectivity and yield of butadiene are high, the yield of COX, alkynes and oxygenated chemicals are relatively low. If we continue raising the reaction temperature, the yield of oxidative byproducts COX increased, selectivity of butadiene decreased, which can reduce the utilization of carbon atoms. The oxidative reaction temperature rises so quickly so that the catalysts coke heavily, which can affect the reaction’s effect. Therefore, the reaction temperature is the main factor to affect the process.The paper also studies the thermodynamic analysis and calculations for the reaction process of butene to butadiene. Using Kirchhoff formula we obtain the standard molar enthalpy(?fHmθ) of each component and standard molar reaction enthalpy(?rHmθ) of each reaction under different temperature. It is concluded that the heat of the reaction increased gradually with the increasing temperature. As the temperature reach to 382℃, the heat of reaction up to about 201.7kJ/mol, the theoretical value of adiabatic temperature rise 228℃ is obtained based on the experiment statistics, while we calculate the simulation value 237.5℃ by Aspen plus software with a difference of 9.5℃, which is consistent with the theoretical data. So it indicates that the simulation results can be used as the design basis for reactor’s engineering amplification of oxidative dehydrogenation of butene to butadiene.