Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO_(2)and methanol over ceria catalysts  

氧化铈催化剂表面性质对催化CO_(2)和甲醇合成碳酸二甲酯影响的机理研究

作　　者：Lei Dong Shengjie Zhu Yangyang Yuan Xiaomin Zhang Xiaowei Zhao Yanping Chen Lei Xu 董磊;朱圣洁;袁扬扬;张晓敏;赵晓炜;陈艳平;许磊(中国科学院大连化学物理研究所,洁净能源国家实验室(筹),辽宁大连116023;中国科学院大学,北京100049;浙江师范大学,杭州高等研究院,浙江杭州311231)

机构地区：[1]National Laboratory for Clean Energy,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Hangzhou Institute of Advanced Studies,Zhejiang Normal University,Hangzhou 311231,Zhejiang,China

出　　处：《Chinese Journal of Catalysis》2024年第10期138-152,共15页催化学报（英文）

基　　金：国家自然科学基金(21978282,21902154);国家重点研发计划(2021YFA1501900)。

摘　　要：The direct synthesis of dimethyl carbonate(DMC)from CO_(2)and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO_(2)and methanol,and the structure-performance relationship was investigated in detail.Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)studies indicated that the adsorption rate of methanol is slower than that of CO_(2)and the methanol activation state largely influences the formation of key intermediate.Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO_(2),the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation.Moreover,with the use of 2-cyanopyridine as a dehydration reagent,the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.碳酸二甲酯(DMC)是一种重要的环境友好绿色化学品,具备低毒、无腐蚀和较好的生物降解性,出色的物理特性和分子结构中多功能有机官能团带来的高反应活性等优点使其在工业生产中得到了广泛应用.以CO_(2)和甲醇为原料直接合成DMC是一种环境友好且可替代传统路线的新型合成方法,凭借其高的原子利用率和避免使用有毒试剂等特点,正受到越来越多的关注。然而,CO_(2)的化学惰性及反应自身严重的热力学平衡限制导致DMC产率极低,严重制约了其工业化应用.尽管在高效催化剂研发及表面功能化调变方面已付出巨大努力,并广泛筛选高效脱水剂以期显著提升DMC产率,但对于催化剂表面性质如何影响底物分子的活化途径、活性中间体的形成以及耦合反应体系中羧化与水合过程的协同匹配,仍缺乏深入的机理研究.本文通过一锅法制备了一系列具有不同微观结构和表面功能的CeO_(2)催化剂,用于CO_(2)和甲醇直接合成DMC的反应评价,详细探索了催化剂理化性质与反应性能间的关系.X射线衍射、扫描电镜、透射电镜、拉曼光谱、X射线光电子能谱及CO_(2)/NH_(3)程序升温脱附结果表明,随着合成温度的降低和样品结晶度的减小,催化剂表面酸碱性和氧空位含量均逐步增加,DMC产率却呈现先升后降的火山型变化趋势.原位漫反射红外结果表明,CO_(2)的吸附与活化过程相比甲醇更易进行,同时甲醇的活化则更易受到催化剂表面预先形成的碳酸盐,尤其是单齿和多齿碳酸盐的影响.尽管低温殿烧带来的酸碱性增强及缺陷位生成有助于促进底物分子的活化,但低结晶度CeO_(2)上于过量强碱位点处形成的高稳定性、非活性的单齿和多齿碳酸盐物种却阻碍了甲醇的活化,进而抑制了单齿碳酸单甲酯中间体及后续DMC的生成.此外,以2-氰基吡啶(2-CP)为脱水剂,研究阐明了耦合反应体系过程中,2-CP�

关 键 词：CeO_(2) Dimethyl carbonate Surface property Methanol activation 2-Cyanopyridine 

分 类 号：O62[理学—有机化学]