镍基催化甲苯分解过程中无定形碳与石墨型碳生成及转化特性

FORMATION AND CONVERSION CHARACTERISTICS OF AMORPHOUS CARBON AND GRAPHITE CARBON IN CATALYTIC DECOMPOSITION OF TOLUENE OVER Ni-BASED CATALYST

采用等体积浸渍法制备Ni/α-Al2O3与Ni-Fe/α-Al2O3,在固定床反应器中进行催化甲苯裂解和重整性能实验,对不同反应阶段的催化剂进行程序升温氧化-质谱联用(TPO-MS)、扫描电子显微镜(SEM)等表征。结果表明:镍基催化剂表面积碳包括无定形碳和石墨型碳,其中石墨型碳主要为碳纳米管。随着反应的进行,积碳量先显著增大后保持稳定。在反应初期,催化剂表面主要生成无定形碳;反应中部分无定形碳转化生成石墨型碳,后者所占比例逐渐增大。在裂解反应(不添加水)中,Ni/α-Al2O3表面积碳以无定形碳为主,比例达到85%以上;在重整反应中,水的加入可显著促进石墨型碳(碳纳米管)的生成,石墨型碳比例达到30%以上。添加铁助剂改性明显抑制无定形碳的生成,Ni-Fe/α-Al2O3积碳以石墨型碳为主,比例达到70%以上。

Ni/α-Al2O3 and Ni-Fe/α-Al2O3 were prepared by using incipient impregnation method.Catalytic cracking and reforming of toluene were tested in fixed bed reactors.The spent catalysts via different reaction times were characterized by TPO-MS and SEM.It is found that the carbon deposition consisted of amorphous carbon and graphite carbon,and the graphite carbon is mainly in the form of carbon nanotubes.As the reaction proceeding,the quantity of carbon deposition remained stable after a significant increase At the beginning of the reaction,amorphous carbon is mainly formed on the surface of catalyst;part of the amorphous carbon converted into graphite carbon in the reaction,and the proportion of graphite carbon gradually increased.In the cracking reaction(without adding water),the carbon deposition on Ni/α-Al2O3 is mainly amorphous carbon whose proportion reached 85%or more.In the reforming reaction,the addition of water significantly promoted the formation of graphite carbon(carbon nanotubes).As a result,the proportion of graphite carbon reaches 30%or more.Addition of iron additives significantly inhibite the formation of amorphous carbon.The carbon deposition on Ni-Fe/α-Al2O3 is mainly graphite carbon.The proportion of graphite carbon reaches more than 70%.