摘要
利用原位X射线衍射(XRD)分析结合密度泛函理论(DFT)计算,揭示了采用溶胶-凝胶法合成的结构明确的钴铁尖晶石(CoFe_(2)O_(4))在催化CO_(2)加氢转化中的结构演变与催化特性。原位XRD分析结果表明,CoFe_(2)O_(4)在预还原过程中形成Co_(3)Fe_(7)合金,Co_(3)Fe_(7)合金在反应中保持稳定,且其催化加氢能力较强,转化产物主要为甲烷与C_(2)-C_(4)烷烃(C_(2)^(0)~C_(4)^(0))。K-CoFe_(2)O_(4)(将CoFe_(2)O_(4)用K_(2)CO_(3)助剂改性)的预还原过程中出现富钴合金(K-Co1Fe1)向富铁合金(K-Co_(3)Fe_(7))的转化,且需要更高的预还原温度才能使Co_(3)Fe_(7)合金完全形成。反应过程中,K-Co_(3)Fe_(7)逐渐被碳化并形成双金属碳化物K-(Co_(1-x)Fe_(x))5C2。K-(Co_(1-x)Fe_(x))5C2催化CC偶联能力较强,低碳烯烃(C2=~C4=)与液态烃类(C5+)的时空收率分别达到8.7 mmol/(g·h)与4.6 mmol/(g·h)。DFT计算结果表明,(Co_(1-x)Fe_(x))_(5)C_(2)具有适宜的加氢能垒与较低的C—C偶联能垒,利于碳链增长。
In situ X-ray diffraction(XRD) analysis and density functional theory(DFT) calculation were conducted to reveal the structural evolution and catalytic properties of well-defined cobalt-iron spinel(CoFe_(2)O_(4)) synthesized by sol-gel methods in CO_(2)hydrogenation. In situ XRD results show that Co_(3)Fe_(7)alloy is generated from CoFe_(2)O_(4)in the pre-reduction process and remains stable during the reaction, and it has strong catalytic hydrogenation ability, and the conversion products are mainly CH_(4) and C_(2)~C_(4) alkanes(C_(2)^(0)~C_(4)^(0)). During the pre-reduction of K-CoFe_(2)O_(4)(CoFe_(2)O_(4)modified with K_(2)CO_(3)additive), the cobalt-rich alloy(K-Co1Fe1) is gradually transformed to the iron-rich alloy(K-Co_(3)Fe_(7)), and higher temperature is required for the complete formation of Co_(3)Fe_(7)alloy. In the reaction, K-Co_(3)Fe_(7)is gradually carburized to form bimetallic carbide K-(Co_(1-x)Fe_(x))5C2. K-(Co_(1-x)Fe_(x))5C2shows strong CC coupling ability, and the space time yield of low carbon olefins(C2=~C4=) and liquid hydrocarbons(C_(5+)) reaches 8.7 mmol/(g·h) and 4.6 mmol/(g·h),respectively. DFT calculation shows that the(Co_(1-x)Fe_(x))_(5)C_(2) has suitable hydrogenation energy barrier and low C—C coupling energy barrier, which is conducive to carbon-chain growth.
作者
王明瑞
张蒙蒙
丁凡舒
袁菲
张光辉
聂小娃
郭新闻
WANG Mingrui;ZHANG Mengmeng;DING Fanshu;YUAN Fei;ZHANG Guanghui;NIE Xiaowa;GUO Xinwen(State Key Laboratory of Fine Chemicals,Frontiers Science Center for Smart Materials,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,Liaoning,China)
出处
《低碳化学与化工》
CAS
北大核心
2023年第1期41-49,共9页
Low-Carbon Chemistry and Chemical Engineering
基金
国家自然科学基金(22172013)
辽宁省“兴辽英才计划”(XLYC2008032)
中央高校基本科研业务费(DUT22LAB602,DUT22LK24)
新疆维吾尔自治区重大科技专项(2022A01002-1)。
