Structure Of Mesoporous Ni-Al Composite Oxides And Its Catalytic Dehydrogenation Of Ethane

At present,because of the excessive consumption of oil resources and its non-renewable energy crisis began to emergency.Ethylene as a raw chemical material to measure the development level of a country's petrochemical industry which is increasingly in short supply.The oxidation and dehydrogenation of low carbon alkanes to olefin can effectively alleviate the current embarrassing situation and reduce the cost of chemical raw materials.The oxidative dehydrogenation of ethane to ethylene under O2 and catalysts is an effective method for the comprehensive utilization of natural gas.Therefore,it is of great significance to design a catalyst with high ethane conversion and ethylene selectivity.The transition metal Ni-based catalyst with high activity could activate ethane at low temperature and lead to the occurrence of deep oxidative reaction,so the selectivity of ethylene reduces.Based on the literature and the previous research work of our group,Ni and Al were selected as the active component and the additive in the thesis,respectively.And the mesoporous Ni-Al mixed oxide catalysts were prepared by the hydrothermal condition.The effects of metal ratio,type of templates and non-metallic additive P on the structure and properties of the Ni-Al-O catalysts were investigated.The main results are as follows:1.The mesoporous Ni-Al composite oxide catalysts with different Al contents were synthesized by the hydrothermal method with PEG-4000 as the template.And the effects on the structure and performance of the catalysts were investigated.The results showed that the surface acidity,the interaction between metals,the specific surface area and the activity of those catalysts changed obviously with the Al content.Ni:Al=1:0.8 and T=500 ~oC,the ethane conversion and ethylene selectivity were up to 53%and 29%,rescpectively.2.Mesoporous Ni-Al-O catalystswere prepared by adjusting the type of templates under hydrothermal conditions.The catalytic performances of the catalysts were evaluated on a fixed-bed micro-reactor,and the physicochemical properties and structures of the catalysts were studied by a large number of characterization,and the relationships between the structure and performance were also explored.The results showed that the mesoporous structure and appropriate specific surface area were favorable for the transport and diffusion of ethane molecules,thus improving the selectivity of ethylene.PEG-4000-Ni-Al-O=1:1.8 catalyst showed 56%of ethane conversion and 28%of ethylene yield at 525 ~oC.3.P-Ni-Al-O catalyst was prepared by hydrothermal method with PEG-4000 as template.It was found that the addition of P could effectively reduce the reaction temperature.When the P content was 0.15 mol and T was 525 ~oC,the ethane conversion and the yield of ethylene were56% and 32%,respectively.