Li掺杂La_(2)O_(3)催化剂上甲烷氧化偶联反应中氧物种迁移及类型对CH_(4)解离影响的DFT研究  

DFT study on effects of oxygen species migration and its type on CH_(4) dissociation in oxidative coupling of methane reaction on Li-doped La_(2)O_(3) catalysts

作　　者：刘思 章日光[1] LIU Si;ZHANG Riguang(State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China)

机构地区：[1]太原理工大学省部共建煤基能源清洁高效利用国家重点实验室,山西太原030024

出　　处：《低碳化学与化工》2025年第3期12-22,共11页Low-Carbon Chemistry and Chemical Engineering

基　　金：国家重点研发计划(2021YFA1502804);山西省杰出青年科学基金(202103021221005)。

摘　　要：La_(2)O_(3)催化剂广泛应用于甲烷氧化偶联(OCM)反应,但确定该反应中关键氧物种的类型及其对甲烷解离活性的影响仍具有挑战性。基于密度泛函理论(DFT)计算,探究了Li掺杂La_(2)O_(3)催化剂上氧迁移过程、氧迁移过程中形成的氧物种类型以及氧物种类型对甲烷解离活性的影响。结果表明,对于Li/Ov-La_(2)O_(3)催化剂,O_(2)在催化剂表面氧空位上形成表面超氧物种O_(2(1st))^(-),随后表面超氧物种O_(2(1st))^(-)中的一个O迁移到次表层形成次表层过氧物种O_(2(2nd))^(2-),即Li/Ov-La_(2)O_(3)-O_(2(2nd))^(2-)催化剂。对于Li/La_(2)O_(3)催化剂,O_(2)解离与催化剂表面晶格氧结合生成两个表面超氧物种O_(2(1st))^(-),随后表面超氧物种O-2中的一个O迁移到次表层形成次表层过氧物种O_(2(2nd))^(2-),即Li/La_(2)O_(3)-O_(2(1st))^(-)+O_(2(2nd))^(2-)催化剂。Li/Ov-La_(2)O_(3)-O_(2(2nd))^(2-)和Li/La_(2)O_(3)-O_(2(1st))^(-)+O_(2(2nd))^(2-)催化剂中的次表层过氧物种O_(2(2nd))^(2-)提高了催化剂的甲烷解离性能,并使甲烷自发解离为吸附态CH_(3)和H。这主要归因于次表层过氧物种O_(2(2nd))^(2-)的存在使得催化剂表面O处于缺电子状态,进而提高了催化剂的甲烷解离性能。La_(2)O_(3) catalysts have been widely used in the oxidative coupling of methane(OCM)reaction,however,identifying the types of key oxygen species and its influence on methane dissociation activity is still a challenge.The oxygen migration,the types of oxygen species formed during oxygen migration and the influence of oxygen species types on methane dissociation activity over Li-doped La_(2)O_(3) catalysts were investigated by density functional theory(DFT)calculation.The results show that for the Li/Ov-La_(2)O_(3) catalysts,O_(2) forms the surface superoxide species O_(2(1st))^(-)at the oxygen vacancies on the surface of the catalysts,and then one O of the surface superoxide species O_(2(1st))^(-)migrates to the subsurface layer to form the subsurface peroxide species O_(2(2nd))^(2-),namely the Li/Ov-La_(2)O_(3)-O_(2(2nd))^(2-)catalysts.For the Li/La_(2)O_(3) catalysts,O_(2) dissociates and combines with the lattice oxygen on the surface of the catalysts to form two surface superoxide species O_(2(1st))^(-),and then one O of the surface superoxide species O-2 migrates to the subsurface layer to form the subsurface peroxide species O_(2(2nd))^(2-),namely the Li/-La_(2)O_(3)-O_(2(1st))^(-)+O_(2(2nd))^(2-)catalysts.Li/Ov-La_(2)O_(3)-O_(2(2nd))^(2-)and Li/La_(2)O_(3)-O_(2(1st))^(-)+O_(2(2nd))^(2-)catalysts with subsurface O_(2(2nd))^(2-)species,which enhance CH_(4) dissociation ability and make CH_(4) spontaneous dissociation occur to form adsorbed state CH_(3) and H.This is mainly due to the presence of the subsurface peroxide species O_(2(2nd))^(2-),which makes the surface O of the catalysts at a state of electron deficiency and improves the methane dissociation ability of the catalyst.

关 键 词：甲烷氧化偶联反应 La_(2)O_(3)催化剂 氧迁移 氧物种 Li掺杂 

分 类 号：TQ032[化学工程] O643.3[理学—物理化学]