磁性MgFe_(2)O_(4)及其核壳催化剂制备与煤热解性能研究

Preparation and coal pyrolysis performance of magnetic MgFe_(2)O_(4)and its core-shell catalysts

采用溶胶-凝胶法制得MgFe_(2)O_(4)前体,经焙烧得到MgFe_(2)O_(4)催化剂,再经Stöber法制得核壳结构催化剂MgFe_(2)O_(4)@SiO_(2)和MgFe_(2)O_(4)@SiO_(2)@HZSM-5(MSH),利用VSM、XRD、SEM、FT-IR、N_(2)物理吸附等手段研究了催化剂的磁性能和结构特征;在固定床反应器上,考察了N_(2)气氛下磁性催化剂对补连塔富油煤的催化热解特性及回收再生性能。结果表明:MgFe_(2)O_(4)为立方尖晶石结构,饱和磁化强度达到181.50 emu/g,具有良好热稳定性能。上述系列磁性催化剂均呈现出良好的催化活性,其中MSH催化活性最好。与非催化热解相比,MSH催化热解焦油产率提高了57.7%,焦油中脂肪烃和苯类含量增加约2倍,稠环芳烃含量下降8.6%~9.8%。采用磁选方法可有效实现催化剂回收,经700℃下焙烧处理,可实现回收催化剂的再生。SiO_(2)包覆有助于提高核壳结构催化剂的磁热稳定性和催化寿命。

The MgFe_(2)O_(4)precursor was prepared by the sol-gel method,the MgFe_(2)O_(4)catalyst was obtained by calcination,and the core-shell structure catalyst MgFe_(2)O_(4)@SiO_(2)and MgFe_(2)O_(4)@SiO_(2)@HZSM-5(MSH)were prepared by the Stöber method.The magnetic properties and structural characteristics of the catalysts were investigated by VSM,XRD,SEM,FT-IR,and N_(2) physical adsorption.In a fixed bed reactor,under an N_(2) atmosphere,the magnetic catalysts were investigated for the catalytic properties and recovery and regeneration of tar-rich coal from the Bulianta(BLT).The results show that the MgFe_(2)O_(4)has a cubic spinel structure with a saturation magnetization of 181.50 emu/g and good thermal stability.The above series of magnetic catalysts all show good catalytic activity,among which MSH has the best catalytic activity.Compared with non-catalytic pyrolysis,the tar yield of MSH catalytic pyrolysis increased by 57.7%,the content of aliphatic hydrocarbons and benzene in the tar increased by about 2 times,and the content of polycyclic aromatic hydrocarbons decreased by 8.6%-9.8%.The magnetic separation method can effectively realize the recovery of the catalyst,and regeneration of the catalyst can be realized by roasting in 700℃.The SiO_(2)coating helps to improve the magnetocaloric stability and catalytic lifetime of the core-shell catalyst.