Research On New Catalyst And Reaction Process For Dehydrogenation Of Long Chain Alkanes

Long chain alkane and its ramification play an important role in petrochemical industry,products of long chain alkanes dehydrogenation are key materials for alkylbenzene and poly-a-olefins synthetic lubricant oil.The quality and output of these products are dominated by the performance of catalysts to some extent,thus research on long chain alkanes dehydrogenation catalysts is meaningful.In this paper,catalysts were prepared by mixed isovolumetric impregnation method,fixed bed micro reactor was used to evaluate the performance of catalysts.Firstly,the effect of hydrothermal treatment on the performance of catalyst was investigated,the results show the best HTT conditions are the temperature of 700℃ and the water flow of 32 ml/h.The catalysts were evaluated under different feeding method and different particle size to explore the effect of these variables.The conversion of alkanes and the deactivation of catalysts become larger as the number of carbon atoms increase.When C10,C12,C14 were mixed as a raw material,the initial molar conversion of alkanes was 10.87%and the initial molar selectivity of olefins was 91.81%,the selectivity of olefins has a increase compared with C10,C12,C14 used as materials separately.When the catalyst in 20-40 mesh,the reaction was influenced by interior diffusion to some extent,but when the catalyst in 40-60 mesh and 60-80 mesh,interior diffusion effect was eliminated basically.The conversion of alkanes is lower and the selectivity of olefins is higher with the existence of interior diffusion.MgAl2O4,Mg-Al-LDO and γ-Al2O3 were selected as supports to prepare dehydrogenation catalysts,when γ-Al2O3 was used as a support,the catalyst stability was superior.The result of N2-adsorption shows that the average pore size and the pore volume of MgAl2O4 and Mg-Al-LDO are much smaller than those of γ-Al2O3,which are bad for coke immigration,leading to fast catalyst deactivation.A mixture of steam and hydrogen was used as a diluent,loading of B,A,and platinium were optimized under the reaction conditions of T=420℃,P=0.14 MPa,water to oil molar ratio=4,hydrogen to oil volumetric ratio=50,total GHSV=7500 h-1.The best loading of each component were 0.3%of platinium,0.5%of B,3 of A:Pt molar ratio.The process conditions were optimized based on the optimization of loading as the mixture of steam and hydrogen was used as a diluent.The conditions include temperature,hydrogen to oil volumetric ratio,water to oil molar ratio and total GHSV.The process conditions after optimization were 420-430℃ of temperature,4 of water to oil molar ratio,50 of hydrogen to oil volumetric ratio,7500h-1 of total GHSV.The conversion of dodecane was between 15-16%,the selectivity of dodecene was about 88%under the condition of T=420℃,P=0.14 MPa,hydrogen to oil volumetric ratio=50,water to oil molar ratio=4,total GHSV=7500 h-1.