Study On The Application Of CoCeMO(M=Zr,Al) Catalyst In Direct Dehydrogenation Of Ethylbenzene To Styrene

Styrene is an important foundation organic synthetic monomer,which is widely used in manufacturing organic polymers.With the acceleration of industrialization process,the demand for styrene has also increased.The traditional styrene production method needs water vapor in the reaction process,resulting in high energy consumption,high cost and other problems.Therefore,the preparation of styrene by direct dehydrogenation of ethylbenzene under the condition of anhydrous steam gas has potential application value.Metal oxide catalysts can catalyze ethylbenzene to produce styrene directly without using superheated steam.Among them,Co₃O₄-Ce O₂ shows good catalytic synergy,but its catalytic performance needs to be further improved.This problem can be solved by doping metal ions into the oxide matrix to change the chemical and texture properties of the oxide.Doping helps to form mixed oxides with unique properties.Therefore,in this thesis,different metal（Zr,Al）doped Co₃O₄-Ce O₂metal oxide catalysts were prepared,and the effects of metal doping on the catalytic performance and structure-activity relationship of the catalyst in the direct dehydrogenation of ethylbenzene to styrene were investigated.On this basis,the reaction conditions were optimized.The main research contents are as follows:（1）The metal oxide catalyst with molar ratio of Co/（Ce+Zr）=9:1,Zr/（Ce+Zr）=x（x=0-0.2）was prepared by oxalate pyrolysis.The activity and structure-activity relationship of the catalyst were investigated.The results show that the doping of Zr effectively improves the performance of the catalyst.When x=0.15,the catalyst has the best performance of ethylbenzene dehydrogenation,with ethylbenzene conversion of 30.41%and styrene selectivity of 95.22%.Combined with the analysis of the characteristics,it is found that when x=0.15,the catalyst has the maximum ratio of the surface area,rich lattice oxygen species,CO³⁺species and the best redox ability.The above factors are the main reasons for improving the direct dehydrogenation catalytic properties of ethylene.Based on the above work,the reaction conditions were optimized.The results show that the catalyst has good catalytic activity when calcined at 400℃for 4 hours.When the dosage is 0.5 g,the gas flow rate is 20 mL/min,the evaluation temperature is 723 K and the service time is less than 4 hours,the activity and stability of the catalyst are good.（2）A series of metal oxide catalysts with molar ratio of Co/（Ce+Al）=9:1 and Al/（Ce+Al）=y（y=0-0.6）were prepared with main group metal Al as doping element.The effects of Al doping on the activity and structure-activity relationship of the catalyst were investigated.The results show that Al doping can improve the activity of the catalyst.When y=0.4,the catalyst has excellent catalytic performance.The conversion of ethylbenzene is 28.63%and the selectivity of styrene is 94.91%.Combined with the analysis of the characteristics,it is found that when y=0.4,the catalyst has a large surface area,exposing more activity sites and better redox ability.On this basis,the reaction conditions were optimized.The results show that the catalyst has good activity and stability with the dosage of 0.5 g,the gas flow rate of 20 mL/min,the evaluation temperature of 723 K and the service time of less than 4 h.