摘要
丁二烯是重要的化工原料,主要用于生产树脂、合成橡胶、丁二醇和己二腈等大宗化学品,还可以用于制备蒽醌、四氢苯酐等精细化学品.目前,工业上制备丁二烯的方法主要是乙烯副产抽提法.近年来,随着生物乙醇技术大力发展,催化乙醇制丁二烯成为很有吸引力的生产丁二烯的路线之一.目前催化乙醇制丁二烯的催化剂种类较多,合理设计具有活性位点结构和功能的催化新材料是提升催化剂活性的关键.稀土金属元素如Y,La和Ce等具有独特的电子层结构,并且具有中等强度的Lewis酸性,本文尝试将稀土磷酸盐与具有乙醇脱氢活性的过渡金属位点结合起来,设计过渡金属改性的稀土磷酸盐催化剂并用于乙醇转化制丁二烯.本文开发了Co-YPO_(4)双功能催化剂,应用于乙醇转化制丁二烯反应,所制材料表现出较高的催化活性与稳定性.在YPO4催化剂上,乙醇主要发生脱水反应,生成大量的乙烯和乙醚,且丁二烯选择性不超过5%;而在Co-YPO_(4)催化剂上,乙醇转化产物分布出现明显改变,丁二烯选择性增加.在乙醇重时空速和反应温度分别为1.0 gC2H5OH×gCat.‒1×h^(‒1)和350℃的条件下,乙醇转化率为78.2%,丁二烯选择性为68.5%.原位紫外-可见漫反射光谱、X射线光电子能谱以及H_(2)^(-)程序升温还原表征结果表明,Co2+中心与PO_(4)^(3‒)基团存在强的配位相互作用,形成稳定且高度分散的[Co-O-P]物种.通过NH_(3)^(-)程序升温脱附(TPD)和吡啶探针分子吸附红外对YPO4和Co-YPO4进行酸性表征,结果表明,YPO_(4)和Co-YPO4表面均是典型的Lewis酸性位点;结合CO_(2)-TPD表征发现,Co^(2+)与YPO4表面部分Y3+位点发生置换,即引入适量的Co会减弱酸性同时增强表面碱性.进一步通过停留时间、乙醇程序升温表面反应和原位乙醇吸附反应漫反射红外光谱测试对反应机理进行详细研究.结果表明,乙醇首先在Co^(2+)位发生脱氢生成乙�
Upgrading of sustainable ethanol into C_(4)olefins by C–C coupling contributes to alleviating the dependency towards petroleum.The reaction network consists several key steps,whereas dehydration often competes with dehydrogenation over acidic catalyst.Herein,we report a designed bifunctional Co-YPO_(4) catalyst with balanced active sites for dehydrogenation and condensation that can directly catalyze ethanol to butadiene.The YPO4 can stabilize Co^(2+) species to form highly dispersed[Co-O-P]sites,which catalyze ethanol dehydrogenation to acetaldehyde.Additionally,the YPO4 surface exposed Y^(3+) site,as Lewis acid center,which can effectively catalyze C–C coupling reaction.The addition of cobalt enhances the ethanol dehydrogenation process while reducing the surface acidity,thus inhibiting the formation of dehydration products and promoting the formation of butadiene.Kinetic measurements suggest that the rate-limiting step is the dehydrogenation of ethanol to acetaldehyde.The synthesized Co-YPO4 shows a 68.5%selectivity of butadiene under a conversion of 78.2% at 350°C and a weight hourly space velocity of 1.0 gC_(2)H_(5)OH×gCat.^(–1)×h^(–1).
作者
周百川
李文翠
王嘉
孙丹卉
向诗煜
高新芊
陆安慧
Bai-Chuan Zhou;Wen-Cui Li;Jia Wang;Dan-Hui Sun;Shi-Yu Xiang;Xin-Qian Gao;An-Hui Lu(State Key Laboratory of Fine Chemicals,Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources,School of Chemical Engineering,Dalian Universityof Technology,Dalian116024,Liaoning,China)
基金
国家重点研发计划项目(2021YFA1500300)
大连市科技创新基金项目(2021JJ12GX021)
辽宁省滨海实验室基金项目(LBLE-2023-04).
关键词
乙醇
丁二烯
脱氢
碳碳偶联
磷酸盐
Ethanol
Butadiene
Dehydrogenation
C–C coupling
Phosphate
