摘要
以Co基催化剂耦合沸石分子筛催化剂应用于合成气催化转化可以有效改善催化剂的产物选择性。本研究通过浸渍法制备得到Zr/Al_(2)O_(3)载体和Pt/ZSM-5催化剂,再通过超声分散法制备了Co/Al_(2)O_(3)、Co/Zr/Al_(2)O_(3)和Co/Zr/Al_(2)O_(3)-Pt/ZSM-5催化剂。通过系列表征技术对载体和催化剂理化性质进行分析,评价了催化剂费-托合成反应性能。结果表明,Zr的引入有助于提升Co/Zr/Al_(2)O_(3)上Co物种的还原性,改善催化活性,增加C_(12+)重质烃的选择性。当Co/Zr/Al_(2)O_(3)与Pt/ZSM-5耦合后,由于贵金属Pt的助剂效应,进一步促进Co物种的还原,Co/Zr/Al_(2)O_(3)-Pt/ZSM-5催化剂的CTY值提高至8.3×10^(−5) mmol/(g·s),同时具有较低的CH_(4)、C_(2)−C_(4)产物选择性。此外,Pt/ZSM-5的酸性促进C_(12+)产物的部分裂解,使产物分布向C_(5)−C_(11)液态烃偏移,C_(5)−C_(11)产物选择性达到45.9%。本研究为设计和制备高效的费-托合成催化剂提供了参考。
The Co catalysts exhibit high catalytic activity and low water gas shift activity,as well as excellent chain growth ability and low by-product selectivity for Fischer-Tropsch synthesis.The performance of the Co catalyst is influenced by several factors,including its structural composition and physical and chemical properties.The traditional cobalt Fischer-Tropsch catalyst follows the ASF distribution,resulting in a wide range of hydrocarbon products.This makes it difficult to achieve high selectivity for liquid hydrocarbons.Due to the presence of a large number of acidic sites on the surface of zeolite,it has excellent catalytic performance for hydrocracking.The integration of zeolite molecular sieves with Fischer-Tropsch catalysts to form a multi-component catalyst can significantly improve product selectivity,optimize liquid hydrocarbon yields and bypass conventional wax treatment steps.In this study,the catalysts Co/Al_(2)O_(3),Co/Zr/Al_(2)O_(3) and Co/Zr/Al_(2)O_(3)-Pt/ZSM-5 were prepared by ultrasonic dispersion method,and the effects of Zr promoter modification and multicomponent coupling catalyst on the activity and product selectivity of Fischer-Tropsch synthesis were investigated.In Co/Al_(2)O_(3),Co/Zr/Al_(2)O_(3) and Co/Zr/Al_(2)O_(3)-Pt/ZSM-5 catalysts,the Co species are uniformly dispersed on the support surface and have similar particle sizes.Pt and Zr were uniformly dispersed in the catalyst,Zr was mainly dispersed on the surface of Al_(2)O_(3) supports,and Pt was mainly dispersed on the surface of ZSM-5 molecular sieve.The reduction of Co species was promoted by Zrmodified alumina.With the addition of Pt/ZSM-5 catalyst,the adsorbed hydrogen is more easily dissociated and converted into active hydrogen,further promoting the reduction of Co species.The catalytic performance of Fischer-Tropsch synthesis was evaluated.Compared with Co/Al_(2)O_(3) catalyst,the selectivity of C_(12+)heavy hydrocarbon products on Co/Zr/Al_(2)O_(3) catalyst increased from 28.2%to 38.1%,with a corresponding decrease in CH_(4),C_(2)−C_(4) and C_(5)−C_(11) products,indicating that Zr promoter promoted the generation of heavy hydrocarbon products.Coupled with Pt/ZSM-5 catalyst,the Co/Zr/Al_(2)O_(3)-Pt/ZSM-5 catalyst showed low CH_(4) selectivity(10.0%)and C_(2)−C_(4) selectivity(15.0%),while the selectivity of C_(5)−C_(11) liquid hydrocarbon products increased from 32.1%to 45.9%,the selectivity of heavy hydrocarbon products(C_(12+))decreased from 38.1%to 29.1%.Compared to Co/Zr/Al_(2)O_(3),the TOF and CTY of Co/Zr/Al_(2)O_(3)-Pt/ZSM-5 catalysts are increased by 212.6%and 62.7%,respectively.The improvement in catalytic activity was mainly due to the addition of Zr promoter and Pt/ZSM-5 catalyst,which promoted the reduction of Co species.Under the synergistic effect of Zr promoter and Pt/ZSM-5 catalyst,Zr promoter promotes the formation of C_(12+)heavy hydrocarbons,while Pt/ZSM-5 catalyst promotes the hydrocracking of heavy hydrocarbons to C_(5)−C_(11) liquid hydrocarbons,thereby improving the selectivity of Co/Zr/Al_(2)O_(3)-Pt/ZSM-5 catalyst for C_(5)−C_(11) liquid hydrocarbons.In this study,a functional catalyst was constructed by coupling Fischer-Tropsch synthesis catalyst and hydrocracking catalyst at nanoscale,which achieved high selectivity of C_(5)−C_(11) liquid hydrocarbon and low selectivity of CH_(4) and C_(2)−C_(4) products,which provided a reference for the design and implementation of catalysts with high selectivity for liquid hydrocarbons.
作者
李航
张煜华
向容
艾心燕
闫浩宇
刘成超
李金林
LI Hang;ZHANG Yuhua;XIANG Rong;AI Xinyan;YAN Haoyu;LIU Chengchao;LI Jinlin(Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education&Hubei Key Laboratory of Catalysis and Materials Science,South-Central Minzu University,Wuhan 430074,China)
出处
《燃料化学学报（中英文）》
EI
CAS
CSCD
北大核心
2024年第5期656-666,共11页
Journal of Fuel Chemistry and Technology
基金
科技部重点研发计划(2022YFB4101201)
国家自然科学基金(21902187,21972170,U22A20394)
湖北省重点研发计划(2022BCA084)
中南民族大学中央高校基本科研业务费专项资金(CZY23016)资助。
关键词
钴基催化剂
ZSM-5
超声分散法
费-托合成
Co-based catalysts
ZSM-5
ultrasonic dispersion method
Fischer-Tropsch synthesis
