催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (11): 1860-1869.DOI: 10.1016/S1872-2067(17)62898-5

• 论文 • 上一篇    下一篇

以Ca-M-Al(M=Mg,La,Ce,Y)层状双氢氧化物为前驱体的固体碱用于酯交换合成碳酸二甲酯

廖云辉a,b, 李枫a, 代鑫a,b, 赵宁a,c, 肖褔魁a,c   

  1. a 中国科学院山西煤炭化学研究所煤转化国家重点实验室, 山西太原 030001;
    b 中国科学院大学, 北京 100049;
    c 国家煤基合成工程技术研究中心, 山西太原 030001
  • 收稿日期:2017-07-11 修回日期:2017-08-15 出版日期:2017-11-18 发布日期:2017-11-24
  • 通讯作者: 李枫, 肖褔魁
  • 基金资助:

    山西省自然科学基金（201601D102006）；山西省煤基重点科技攻关项目（MD2014-09，MD2014-10）.

Solid base catalysts derived from Ca-M-Al (M=Mg, La, Ce, Y) layered double hydroxides for dimethyl carbonate synthesis by transesterification of methanol with propylene carbonate

Yunhui Liaoa,b, Feng Lia, Xin Daia,b, Ning Zhaoa,c, Fukui Xiaoa,c   

  1. a State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, Shanxi, China;
    b University of Chinese Academy of Sciences, Beijing 100049, China;
    c National Engineering Research Center for Coal-Based Synthesis, Taiyuan 030001, Shanxi, China
  • Received:2017-07-11 Revised:2017-08-15 Online:2017-11-18 Published:2017-11-24
  • Contact: 10.1016/S1872-2067(17)62898-5
  • Supported by:

    This work was supported by the Natural Science Foundation of Shanxi Province (201601D102006) and the Key Science and Technology Program of Shanxi Province, China (MD2014-09, MD2014-10).

PDF

1210

摘要：

碳酸二甲酯（DMC）是一种环境友好型绿色化学品，可作为甲基化和羰基化试剂用于取代传统剧毒的硫酸二甲酯和光气.另外，DMC具有良好的溶解性能，可用于高级溶剂；DMC分子中具有高的氧含量，可用作汽油添加剂来提高汽油的辛烷值；DMC还可用作聚碳酸酯的原料.随着人们环保意识的不断增强，DMC的生产和应用呈现出巨大的吸引力和市场潜力.DMC合成方法主要有光气法、甲醇氧化羰化法、尿素醇解法及酯交换法等.酯交换法具有反应条件温和、产率高等优点，是目前工业制备DMC的主要方法.研究发现，相对于酸性催化剂，碱性催化剂更有利于酯交换法合成DMC.金属氧化物催化剂具有活性高、热稳定性高及可连续重复回收利用等优点，因而引起了广泛关注.CaO对于酯交换合成DMC反应具有良好的催化活性，但其稳定性差.因此，通常采用复合金属氧化物来促进CaO的分散，并增加金属间相互作用以防止CaO流失.研究发现，经煅烧后的Mg-Al，Ca-Al和Ca-Mg-Al催化剂对于酯交换反应具有高的活性和稳定性.此外，通过碱性稀土金属（La，Ce和Y）的引入可以修饰催化剂上的碱性位点，从而调变催化剂的碱性.
本文合成了一系列以Ca-M-Al （M=Mg，La，Ce，Y）层状双氢氧化物为前驱体的固体碱催化剂，将其用于甲醇与碳酸丙烯酯酯交换合成DMC.通过X射线衍射、热重分析、红外光谱、X射线光电子能谱、电感耦合等离子体、CO2程序升温脱附和Hammett指示剂对催化剂进行了表征.研究发现，各催化剂的活性高低依次为：Ca-Y-Al < Ca-Al < Ca-Ce-Al < Ca-La-Al < Ca-Mg-Al，这与催化剂表面总碱量相一致.通过Mg和La的引入，催化剂表面出现了超强碱性位.其中，Ca-Mg-Al催化剂表面具有最高的（Ca+Mg）：Al原子比，从而导致催化剂表面产生更多的不饱和O2-离子，因而具有最高的碱性位数量.此外，通过Mg，La，Ce和Y的引入，催化剂的重复使用性能得到了提高.特别是Ca-Mg-Al催化剂，在10次循环后仍保持着高的活性，且其结构没有发生显著变化，表明其稳定性较高，因此该催化剂在非均相催化中具有高的应用价值.

关键词: Ca-M-Al层状双氢氧化物, 固体碱, 酯交换反应, 碳酸二甲酯

Abstract:

Composite solid base catalysts derived from Ca-M-Al (M=Mg, La, Ce, Y) layered double hydroxides (LDH) were synthesized, characterized and applied to the transesterification of methanol with pro-pylene carbonate. X-ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides. Compared with the Ca-Al LDH catalyst, the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg, La or Ce. The catalytic perfor-mance of these catalysts increases in the order of Ca-Y-Al < Ca-Al < Ca-Ce-Al < Ca-La-Al < Ca-Mg-Al, which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La. The Ca-Mg-Al catalyst shows the highest (Ca+Mg):Al atomic ratio, indicating that it likely contains more unsaturated O2- ions, providing it with the highest concentration of very strong basic sites. The recyclability of these cat-alysts is improved following the addition of Mg, La, Ce or Y, with the Ca-Mg-Al maintaining a high level of activity after ten recycling trials. X-ray diffraction analyses of fresh and used Ca-Mg-Al demonstrate that this catalyst is exceptionally stable, which could be of value in practical applica-tions related to heterogeneous catalysis.

Key words: Ca-M-Al layered double hydroxide, Solid base, Transesterification, Dimethyl carbonate