Synergistic sites over the Zn_(x)ZrO catalyst for targeted cleavage of the C-H bonds of ethane in tandem with CO_(2)activation  

Zn_(x)ZrO催化剂上协同位点用于乙烷C-H键靶向性断裂及CO_(2)活化

作　　者：Wenjun Qiang Duohua Liao Maolin Wang Lingzhen Zeng Weiqi Li Xuedong Ma Liang Yang Shuang Li Ding Ma 强文军;廖多华;王茂林;曾令真;李伟奇;马雪冬;杨亮;李爽;马丁(西北大学化工学院,陕西西安710069;北京大学化学与分子工程学院,北京分子科学国家实验室,北京100871)

机构地区：[1]School of Chemical Engineering,Northwest University,Xi’an 710069,Shaanxi,China [2]Beijing National Laboratory for Molecular Sciences,College of Chemistry and Molecular Engineering,Peking University,Beijing 100871,China

出　　处：《Chinese Journal of Catalysis》2025年第3期272-284,共13页催化学报(英文)

基　　金：国家自然科学基金(21878244,22472130);太原理工大学煤炭清洁高效利用国家重点实验室基金(MJNYSKL202407).

摘　　要：The CO_(2)-assisted oxidative dehydrogenation of ethane(CO_(2)-ODHE)provides a promising way to produce ethylene and utilize CO_(2).Simultaneous upgrading of ethane into the high value-added chemical products and the reduction of greenhouse gas CO_(2)emissions could be achieved.However,the targeted breaking of the C-C/C-H bonds of ethane is still a challenge for the designed catalysts.In this paper,ZnO-doped ZrO_(2)bifunctional catalysts(Zn_(x)ZrO)with different Zn/Zr molar ratios were prepared by the deposition-precipitation method,and the functions of various sites for CO_(2)-ODHE reaction were revealed by in situ characterizations and ethane pulse experiment:the medium-strength acidic Zn-O-Zr sites are responsible for the purposefully cracking of ethane C-H bonds to ethylene,while the more oxygen vacancies(OV)created by the introduction of Zn^(2+)are responsible for the efficient activation C=O bonds of CO_(2),thus promoting the RWGS reaction.In addition,the Zn0.2ZrO catalyst demonstrated excellent catalytic performances,with C_(2)H_(6)conversion,C_(2)H_(4)yield,and CO_(2)conversion about 19.1%,10.5%,and 10.6%within 5 h,respectively(600℃,GHSV=3000 mL/(g·h)).Especially,the initial ethylene space-time yield of 355.5μmol/(min·g)was obtained under 6000 mL/(g·h);Finally,the tandem reaction mechanism of ethane dehydrogenation and RWGS was revealed.CO_(2)辅助乙烷氧化脱氢(CO_(2)-ODHE)是将低碳烷烃(乙烷)和温室气体CO_(2)进行一体化资源利用的绿色工程,具有重要意义.该技术为碳资源有效利用、重要化工产品生产以及环境保护等提供了新的发展思路.然而,乙烷C-C/C-H键竞争性断裂仍然是研制高性能催化剂的重大挑战.工业上主要通过乙烷蒸汽裂解和催化裂化生产乙烯,但存在能耗高、碳排放大、结焦严重等缺点.利用CO_(2)作为温和氧化剂,选择性氧化乙烷脱氢制乙烯,是更为原子经济性的反应,并得到了工业界和学,术界的广泛关注.然而,乙烷和CO_(2)转化率以及烯烃的选择性强烈依赖催化剂的组成和结构,目前普遍存在活性有限、选择性不高、稳定性不够理想的问题.合理设计催化剂是实现C-H键选择性剪裁和高效活化CO_(2)的关键.本文采用沉积-沉淀法制备了一系列ZnO掺杂ZrO_(2)双功能催化剂(Zn_(x)ZrO),并通过原位表征和乙烷脉冲实验揭示了CO_(2)-ODHE反应重要的表面化学过程.X射线衍射、拉曼光谱、X射线吸收近边结构、X射线光电子能谱及二氧化碳程序升温脱附结果表明,ZrO_(2)中掺杂Zn^(2+)后形成了Zn-O-Zr位点以及产生了更多氧空位(O_v).通过原位红外及乙烷脉冲实验揭示了两种类型活性位点的功能:中等强度Lewis酸性位点(Zn-O-Zr位点)选择性地断裂乙烷C-H键,而强Br?nsted碱性位点(氧空位)有效地激活CO_(2)C=O键.在Zn_(x)ZrO催化剂上,CO_(2)-ODHE主要遵循乙烷脱氢和RWGS串联反应机理.即乙烷在Zn-O-Zr位点直接脱氢生成C_(2)H_(4)和副产物H;接着,CO_(2)与副产物H在氧空位上反应生成甲酸中间体,甲酸中间体进一步解离成CO和H_(2)O,同时Zn-O-Zr活性位点再生完成整个反应循环.在性能测试方面,Zn_(0.2)ZrO催化剂表现出最佳的催化活性,在5h内平均C_(2)H_(6)转化率,C_(2)H_(4)产率和CO_(2)转化率分别达到19.1%,10.5%和10.6%(600℃,GHSV=3000 mL/(g·h)).尤其当GHSV增

关 键 词：Zn-O-Zr site Oxygen vacancies CO_(2) Ethylene space-time yield Tandem reaction 

分 类 号：O643.3[理学—物理化学]