Study On Preparation Of Silvercatalyst For Oxidation Ethylene Oxide To Ethylene Oxide

Ethylene oxide is an important organic chemical product second only to polyethylene and polyvinyl chloride among ethylene industrial derivatives.In recent years,the domestic production of ethylene oxide has been increasing,improving the selectivity of silver catalysts and reducing production costs are urgent requirements of current ethylene epoxidation production equipment.In this paper,α-Al2O3 is used as a catalyst carrier,a highly selective silver catalyst is prepared by the impregnation method,and the pore-forming technology of surfactant-pore additive is used to optimize the pore distribution of the carrier.Carrying out the loading of active components through carrier surface pretreatment-complexing impregnation technology,improve the activity and stability of the catalyst,thereby preparing a highly selective silver catalyst,reduce the production cost of ethylene oxide,and improve economic efficiency.The results show that the best preparation conditions are as follows:the amount of pore forming agent is 10%-15%,the amount of alumina trihydrate is 20%-30%,the acid concentration is more than 5%,and the calcination temperature is 1400-1470℃.The addition of Ti element can effectively reduce the transformation temperature of alumina crystal,which is conducive to the improvement of the specific surface ofα-Al₂O₃carrier;the addition of Sr element can improve the phase transformation temperature of alumina,and increase the specific surface area and pore volume at high temperature;the addition of Si element can effectively improve the specific surface area of spherical alumina carrier and enhance the load Ce can inhibit the sintering of alumina at high temperature,maintain a good pore pattern and larger pore volume.The results show that the best preparation conditions of silver catalyst are as follows:the average pore diameter is 2μm,the porousα-Al₂O₃is used as the carrier,the silver oxalate is used as the silver source,the silver amine complex impregnation thermal decomposition method is used,the activation temperature is 170℃,the activation time is 5min,the loading pressure is-0.08 to-0.10MPa,the aging time is 15-20h,the drying time is 4-8h,the treatment solvent is acetone.Physical properties of silver catalyst:silver crystal size 80-150nm,silver load 25%-30%,specific surface 2m²·g^-1,strength 55-70N/capsule,abrasion≤0.2%,the best way to introduce Cselement is Ag/Cs co impregnation,element content 600mg·kg^-1,the best way to introduce Re element is Ag first,then re impregnation,element content 300mg·kg^-1.The activity and selectivity of the synthesized silver catalyst were evaluated by the microreactor.The results show that under the conditions of reaction temperature:200-230℃,reaction pressure:2.05MPa,volume space velocity:6000hr^-1,space-time yield:100-300kg EO/（h·m³）,the optimized performance indexes of silver catalyst are as follows:ethylene single pass conversion rate≥8%,ethylene oxide initial selectivity reaches 85%(feed component content:ethylene 8.39L·h^-1,air 10.72L·h^-1,carbon dioxide 0.30L·h^-1,nitrogen10.58L·h^-1,no inhibition is added The best ratio of carbon dioxide feed is 1.25%.