镍硅改性对环氧乙烷合成用银催化剂及其载体性能的影响

氧化铝原料来源改变后,银催化剂活性和稳定性波动,为了改善银催化剂性能,分别对载体进行硅改性、镍改性及镍硅共同改性。采用X射线衍射、N2物理吸附-脱附、压汞和扫描电镜等对催化剂物性及微观结构进行表征,研究各种改性对载体孔结构、比表面积和强度等的影响。结果表明,经各种改性后载体的小孔增多,比表面积增大,载体强度增加。制成的银催化剂在空速6 000 h-1和出口环氧乙烷物质的量分数为2.50%条件下进行微反评价,银催化剂的活性和稳定性均提高,其中,以镍硅共同改性后的效果最佳,运行至第215天时,反应温度仅为231.7℃,而未改性催化剂运行至第8天时,反应温度已达227.0℃。

Effects of modification by silicon and nickel on behaviors of silver-based ethylene oxide synthesis catalyst and its carrier

The activity and stability of silver catalyst for synthesis of ethylene oxide(EO) fluctuate with the sources of alumina.The carriers of the catalyst were modified by silicon,nickel and combination of silicon and nickel,respectively,so as to improve the performance of the catalyst.The physical properties and microstructure of the silver catalyst were characterized by XRD,N₂ physical adsorpition-desorption,mercury intrusion method and SEM.The effects of different modification on pore structure,surface area and strength of the carriers were investigated.The results showed that the amount of micropores,surface area and strength of the carrier increased after the modification;the activity and stability of the silver catalyst were enhanced.Under micro-reactor condition of space velocity 6 000 h^-1 and EO molar fraction of 2.50%,especially of those modified by nickel and silicon in combination,with its reaction temperature remained 231.7 ℃ after 215 days of operation,in contrast with unmodified silver catalyst,whose reaction temperature climbed to 227.0 ℃ after 8 days of operation.