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Research On Catalytic Dehydrogenation Of Propane To Propylene

Posted on:2017-04-07Degree:MasterType:Thesis
Country:ChinaCandidate:H ZhouFull Text:PDF
GTID:2321330518993053Subject:Applied Chemistry
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In recent years,with the rapid development of the chemical industry,the demand for polypropylene,acrylic acid,acrylic aldehyde and other products increased year by year,making propylene production can not meet the needs of the industry.Propylene,as one of the most important petrochemical raw materials in the world,has become the second largest chemical monomer in the world after ethylene.At present,the excess capacity of propane which is rich in resources and low prices,but the shortage of propylene resources,the situation of production and supply should not be enough.Therefore,it has become a hot topic in the petrochemical industry to convert the propane with low added value to propylene with higher economic value,which has become a very significant research.’I’o develop the catalysts with high activity,high selectivity and long service life and the related technology has become a hot topic in the petrochemical industry.In this paper,the catalysts based chromium for anaerobic dehydrogenation of propane.It used active gamma alumina as carrier,chromium nitrate,chromium trioxide and other chromium compounds as precursors.A series of different catalysts were prepared by incipient-wetness impregnation method.The obtained catalysts were characterized by BET,XRD,SEM,ICP-OES,etc.The catalytic performance of propane dehydrogenation was evaluated under different reaction temperature and reaction pressure,Experimental results show that the different kinds of chromium compounds prepared catalysts are Cr2O3/Al2O3.The difference in the performance of propane dehydrogenation is mainly caused by the chromium load and the valence state of the chromium species.The catalyst for propane dehydrogenation was prepared by using chromium trioxide as precursor,and modified by the rare earth elements lanthanum,cerium and europium to obtain the catalysts for the modification of the rare earth element.The catalysts were characterized by XRD,SEM,NH3-TPD,etc.The catalytic performance of propane dehydrogenation was evaluated under different reaction temperatures and pressures.Experimental results show that the introduction of rare earth elements can adjust the acidity of the catalyst surface and improve the dispersion of’ the active center chromium on the surface of catalyst support,which can increase the conversion of propane and the selectivity of propylene,but the excessive addition of rare earth elements will inhibit the catalytic activity of the catalyst.The experimental catalyst was tested by reaction-regeneration,and the catalyst which were characterized by BET,XRD,SEM,TG,etc.The experimental results show that the experimental catalyst has high catalytic activity and good regeneration performance.When the reaction temperature is 590 ℃,the reaction pressure is 0.05MPa,and the propane hourly space velocity is 300/h,the initial conversion of propane can reach about 55%,the selectivity of propylene is more than 78%,and the operation of the catalyst has good catalytic effect under the condition of long time reaction and regeneration.Analyzing used catalyst,it can be seen that the activity of the catalyst reduced is mainly due to the coke produced in the reaction process.And the carbon jams pore channels of the catalyst,and covers the active center.So that the catalytic activity of the catalyst decreased,eventually lead to the deactivation of the catalyst.
Keywords/Search Tags:propane, propylene, catalytic dehydrogenation, chromium-based catalysts, rare earth element modification
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