二氧化碳气氛下改性SiO_2负载V催化乙苯脱氢

V Catalysts on Supported SiO_2 for OxidativeDehydrogenation of Ethylbenzene with CO_2

以三嵌段共聚物P123为模板剂,正硅酸乙酯为硅源,采用水热法和浸渍法制备改性SiO2负载钒V/ZrO2-TiO2-SiO2催化剂.在CO2气氛下考察其催化乙苯脱氢的反应性能,并采用X射线衍射、BET比表面积、扫描电镜等技术对催化剂体相及表面性质进行表征.结果表明:催化剂在600℃、乙苯空速(LHSV)0.44 h-1、n(CO2)/n(EB)=5.4的条件下具有较好的催化活性,ZrO2和TiO2在SiO2负载型催化剂表面有相互修饰的作用.改性ZrO2-TiO2-SiO2载体有助于提高V2O5在载体表面的分散程度,抑制VOx的聚合,减小V2O5的微晶尺寸,提高其氧化还原能力.

Modified V catalysts V/ZrO2-TiO2-SiO2 on supported SiO2 are synthesized by conventional hydrothermal process and impregnation method using tetraethylorthosilicate（TEOS） as silicon source and triblock copolymer P123 as template.These catalysts were found to be active,selective and catalytically stable at 600 ℃ LHSV 0.44 h-1 and n（CO2）/n（EB）=5.4,for the dehydrogenation of ethylbenzene（EB） to styrene（Sty） in the presence of CO2.Structural and textural characterizations of the catalysts were performed by means of X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and BET surface area methods.It is shown that the V/ZrO2-TiO2-SiO2 catalyst exhibited a better activity than other combinations.ZrO2 and TiO2 on the surface of silica can modify each other.ZrO2-TiO2-SiO2（ZTS） promotes the dispersion of V2O5 on the surface of catalysts.In general,V2O5 is easy to aggregate on the mesoporous zeolites surface.ZTS strengthens the interaction of V2O5 and ZTS,which effectively prevents VOx from aggregation,diminishes the size of crystalline V2O5 and makes it disperse well on the surface of ZTS.