HZSM-5在线提质生物油及催化剂失活机理分析

对不同使用时间的HZSM-5分子筛在线催化提质制取的生物油进行理化特性和成分分析,从生物油品质角度对HZSM-5的催化性能进行评价;并采用TG、BET、XRD、SEM和TEM等方法对失活的HZSM-5催化剂进行表征分析,探讨了HZSM-5催化提质生物油的失活机理,并进行再生研究。研究表明,HZSM-5分子筛可转化生物油中的酸类、醛类和酮类等"非期望"有机物,生成较多"期望"有机物,如酚类和芳烃类物质,降低生物油的氧含量及酸性,提高生物油的热值;HZSM-5使用80 min后,生物油品质明显变差,催化剂活性明显降低;失活催化剂上沉积的焦炭主要呈纤维状,同时,还存在少量石墨状焦炭,焦炭总量达14.12%,且使用过程中催化剂的比表面积和孔容均下降,晶粒的团聚现象加剧,结晶度下降;在催化提质过程中,在孔道内生成的石墨状焦炭及在表面形成的纤维状焦炭大量覆盖活性位点,使得催化剂失活。经550℃再生后,催化剂可恢复催化性能。

Online catalytic cracking of bio-oil ov er HZSM-5 zeolite and analysis of catalyst deactivation

The online catalytic cracking of bio-oil over HZSM-5 was investigated. The HZSM-5 catalyst samples used for different reaction times were analyzed in terms of physicochemical properties and chemical compositions to investigate the effects of bio-oil catalytic online cracking. Simultaneously, the used HZSM-5 catalysts were analyzed by TG, BET, XRD, SEM and TEM to explore the mechanism of HZSM-5 catalyst deactivation. The regeneration of the deactivated catalyst was also studied. It was found that acids, aldehydes and ketones as the undesirable organics contained in the bio-oil were reduced by deoxidization over HZSM-5 and more desirable organics like phenols and aromatic hydrocarbons could be produced. Meanwhile, the activity of the catalyst declined after 80 min reaction, leading to the worse quality of the refined bio-oil. The coke deposited was mainly fibrous carbon with a little graphite carbon, where the total amount of the coke was 14.12%. The graphite coke deposited inside the pore of the catalyst and the fibrous coke deposited outside the surface of the catalyst were contributed to the deactivation of the catalyst. The basic structure of the catalyst remained unchanged, but the specific area and pore volume of the catalyst were decreased simultaneously and the agglomeration of grain was increased, leading to the decrease of crystallinity. The change of some crystal structure of the catalyst resulted in the deactivation of catalyst. After the regeneration, the catalytic activity could be recoveried.