催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (7): 1148-1154.DOI: 10.1016/S1872-2067(17)62841-9

• 论文 • 上一篇    下一篇

非贵金属Co-N-C/MgO高效催化糠醛氧化酯化制糠酸甲酯

霍娜a,b, 马红b, 王新红a, 王天龙a,b, 王刚a,b, 王婷a,b, 候磊磊a,b, 高进b, 徐杰b   

  1. a 大连工业大学纺织与材料工程学院, 辽宁大连 116034;
    b 中国科学院大连化学物理研究所催化基础国家重点实验室, 洁净能源国家实验室(筹), 辽宁大连 116023
  • 出版日期:2017-07-18 发布日期:2017-06-27
  • 通讯作者: 徐杰, 高进
  • 基金资助:

    国家自然科学基金（21233008，21643013，21690084）；中国科学院重点战略研究项目（XDB17020300）；中国科学院青年创新促进会（2013121）.

High-efficiency oxidative esterification of furfural to methylfuroate with a non-precious metal Co-N-C/MgO catalyst

Na Huoa,b, Hong Mab, Xinhong Wanga, Tianlong Wanga,b, Gang Wanga,b, Ting Wanga,b, Leilei Houa,b, Jin Gaob, Jie Xub   

  1. a School of Textile and Material Engineering, Dalian Polytechnic University, Dalian 116034, Liaoning, China;
    b State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, Dalian 116023, Liaoning, China
  • Online:2017-07-18 Published:2017-06-27
  • Contact: 10.1016/S1872-2067(17)62841-9
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21233008, 21643013, 21690084), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB17020300), and the Youth Innovation Promotion Association CAS (2013121).

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摘要：

设计开发绿色、可持续的生物质资源高效转化制化学品催化过程具有重要的科学与应用研究价值.生物质基平台分子糠醛在分子氧存在下与甲醇发生氧化酯化，提供了一条糠酸甲酯的“非石油基”合成新路线.该反应采用贵金属/非贵金属催化体系，目前通常需要引入K2CO3或CH3ONa等碱性添加剂，以提高催化氧化酯化反应活性和选择性;但是存在活性组分流失、生成副产物及污染环境等问题，阻碍了其进一步应用.探索高性能非贵金属催化剂，实现无碱条件下糠醛高效氧化酯化，对于提高该生物质路线竞争力与推动工业化进程具有重要意义.
本文利用浸渍法将1，10-邻菲罗啉合钴（II）负载到碱性载体氧化镁上，在氮气气氛下800 ℃热解，制备了非贵金属Co-N-C/MgO催化剂.在糠醛氧化酯化制糠酸甲酯反应中，Co-N-C/MgO催化剂表现出优异的性能，在0.5 MPa O2，100 ℃条件下反应12 h，糠醛转化率达到93.0%，糠酸甲酯选择性达到98.5%，远超过相同方法制备的其他载体（活性炭、NaX、NaY和CaO）负载的钴基催化剂，实现了无碱性添加剂条件下糠醛高效氧化酯化制糠酸甲酯.X射线光电子能谱、X射线衍射、透射电镜、元素分析以及对比实验结果表明，Co-N-C/MgO催化剂上可能存在含钴的氮掺杂碳物种；该催化剂在糠醛氧化酯化中的高性能与其脱氢能力密切相关.并且在0.3-1.0 MPa氧气压力范围内，Co-N-C/MgO催化糠醛氧化酯化过程基本不受压力变化影响.
糠醛与甲醇的氧化酯化反应和缩合反应为两个竞争路径，反应路径决定了反应的主要产物.我们使用盐酸处理Co-N-C/MgO催化剂，脱除MgO载体，制备了Co-N-C （HCl）催化剂.当使用该催化剂时，糠醛与甲醇主要发生缩合反应，得到缩醛产物2-（二甲氧基甲基）呋喃.如果在Co-N-C （HCl）催化反应体系中引入MgO添加剂，则主要发生糠醛氧化酯化反应，主产物为糠酸甲酯.为了验证Cl-是否对反应产生影响，使用NaCl溶液对Co-N-C/MgO进行浸渍、清洗处理，或直接使用NaCl为添加剂；在这两种情况下，糠醛转化率与糠酸甲酯选择性均下降，表明Cl-对糠醛氧化酯化反应具有负面作用.根据实验结果，阴离子（Cl-）可能与Co （II）中心发生配位，从而影响了金属活性中心的催化性能.Co-N-C （HCl）加入氧化镁，使得糠醛主要遵循氧化酯化路径进行转化，降低Cl-对Co-N-C （HCl）催化活性中心的影响.以上研究可为生物质基醛类化合物氧化酯化转化过程以及高性能非贵金属催化剂的设计开发提供有益参考.

关键词: 催化, 钴-氮-碳, 糠醛, 糠酸甲酯, 氧化镁, 氧化酯化

Abstract:

From both fundamental and practical perspectives, the production of chemicals from biomass re-sources using high-efficiency non-precious metal catalysts is important. However, many processes require addition of stoichiometric or excess quantities of base, which leads to high energy consump-tion, leaching problems, and side reactions. In this study, we investigated the high-efficiency oxida-tive esterification of furfural to methylfuroate by molecular oxygen with a Co-N-C/MgO catalyst. The catalyst was prepared by direct pyrolysis of a cobalt(Ⅱ) phenanthroline complex on MgO at 800℃ under N2 atmosphere. From furfural, 93.0% conversion and 98.5% selectivity toward methylfuroate were achieved under 0.5 MPa O2 with reaction at 100℃ for 12 h without a basic additive. The con-version and selectivity were much higher than those obtained with cobalt catalysts produced by pyrolysis of a cobalt(Ⅱ) phenanthroline complex on activated carbon or typical basic supports, in-cluding NaX, NaY, and CaO. X-ray photoelectron spectroscopy, X-ray diffraction, transmission elec-tron microscopy, and experimental results revealed that the high efficiency of Co-N-C/MgO for pro-duction of methylfuroate was closely related to the cobalt-nitrogen-doped carbon species and its catalytic ability in hydrogen abstraction. In contrast, Co-N-C(HCl) that synthesized by removing MgO with HCl from Co-N-C/MgO, as the catalyst produced mainly an acetal as a condensation prod-uct, and chloride ions had a negative effect on the oxidative esterification. Although the catalytic performance of the cobalt-nitrogen-doped carbon species was greatly affected by HCl treatment, it could be recovered to a great extent by addition of MgO. Moreover, changes in the oxygen pressure hardly affected the oxidative esterification of furfural with Co-N-C/MgO. This study not only pro-vides an effective approach to prepare methylfuroate, but also for designing high-performance non-precious metal catalysts for the oxidative esterification of biomass-derived compounds.

Key words: Catalysis, Cobalt-nitrogen-doped carbon, Furfural, Methylfuroate, MgO, Oxidative esterification