催化学报

催化学报 ›› 2016, Vol. 37 ›› Issue (1): 177-183.DOI: 10.1016/S1872-2067(15)60976-7

• 论文 • 上一篇    下一篇

Ni/C催化剂上山梨醇氢解反应中碱对乳酸形成的影响

张俊杰a,b, 路芳a, 于维强a, 卢锐a,b, 徐杰a   

  1. a 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;
    b 中国科学院大学, 北京100049
  • 收稿日期:2015-08-28 修回日期:2015-09-24 出版日期:2015-12-26 发布日期:2015-12-26
  • 通讯作者: 徐杰, 路芳
  • 作者简介:徐杰, 路芳
  • 基金资助:

    国家自然科学基金(21203183, 21233008, 21473188).

Effects of alkaline additives on the formation of lactic acid in sorbitol hydrogenolysis over Ni/C catalyst

Junjie Zhanga,b, Fang Lua, Weiqiang Yua, Rui Lua,b, Jie Xua   

  1. a State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, Dalian 116023, Liaoning, China;
    b University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2015-08-28 Revised:2015-09-24 Online:2015-12-26 Published:2015-12-26
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21203183, 21233008, 21473188).

PDF

589

摘要：

山梨醇是重要的生物基平台化合物,其选择加氢裂解制备乙二醇和1,2-丙二醇等低碳二元醇,是一个具有重要科学意义和应用前景的催化过程.山梨醇氢解反应涉及C-C键和C-O键等化学键的裂解,裂解选择性尤为关键.通常情况下,添加NaOH,KOH,Ca(OH)2,CaO和Ba(OH)2等碱性物质可增加糖醇转化率和二元醇选择性,但也会生成大量乳酸等副产物.研究乳酸的生成途径,探索抑制乳酸生成的方法,对于提高山梨醇加氢裂解制备低碳二元醇的选择性具有重要意义.
本文以Ni/C催化剂上山梨醇加氢裂解反应为模型反应,研究了碱性化合物添加剂类型及其用量对乳酸生成的影响.根据加氢裂解机理分析可知,糖醇氢解主要涉及以下关键步骤:在碱的存在下,多元醇在金属催化剂上发生脱氢反应生成相应的羰基中间体;然后,羰基中间体在碱性介质中通过逆羟醛缩合反应,发生C-C键断裂.因此,在糖醇氢解反应和C-C键断裂中,添加碱性化合物将会不可避免地生成乳酸.
结果表明,以NaOH和Ca(OH)2为添加剂时,山梨醇加氢裂解生成乳酸的选择性分别为15.1%和8.9%.而以La(OH)3为添加剂时,生成乳酸的选择性仅为0.1%.以Ca(OH)2和La(OH)3为添加剂时反应具有高活性,山梨醇转化率均可达到99%以上.分别以Ca(OH)2和La(OH)3为添加剂,研究了碱性添加剂用量对山梨醇氢解反应的影响.结果表明,以Ca(OH)2为添加剂时,山梨醇转化率和乳酸选择性均随着Ca(OH)2用量增加而增加;当OH-投料量为11.06mmol时,乳酸选择性可达11.7%.而以La(OH)3为添加剂时,即使La(OH)3用量仅为0.08mmol时,山梨醇转化率也可高达99%;继续增加La(OH)3用量,对乳酸的选择性影响不大;当OH-投料量为11.06mmol时,乳酸选择性也只有0.3%.
对山梨醇加氢裂解反应分析可知,与Ca(OH)2相比,La(OH)3添加剂可使C2和C4产物的总选择性从20.0%增加到24.5%. 上述结果表明La(OH)3可高效促进山梨醇加氢转化.为了探索Ca(OH)2或La(OH)3为添加剂时山梨醇加氢裂解产物分布不同的本质原因,以Ni/C催化剂催化的丙酮醛加氢转化为探针反应,探讨了乳酸形成的可能路径.结果表明,丙酮醛可能是山梨醇氢解反应的关键中间体之一.在仅以Ni/C催化加氢时,丙酮醛容易被转化为1,2-丙二醇;当只存在碱性添加剂时,丙酮醛可发生重排并被转化为乳酸主产物,这可能是乳酸生成的主要原因.进一步研究表明,以Ca(OH)2为添加剂时,乳酸选择性是以La(OH)3为添加剂时的1.9倍.在Ni/C催化剂和碱性添加剂共存时,由于碱性添加剂的区别,则会得到不同选择性的1,2-丙二醇和乳酸.结果表明,通过丙酮醛催化加氢可得到1,2-丙二醇,也可以通过重排反应生成乳酸;这两类反应是竞争性的.在山梨醇氢解反应中,以Ca(OH)2为添加剂时,加氢反应和重排反应均可发生.而以La(OH)3为添加剂时,丙酮醛加氢反应占主导,仅生成微量乳酸.该研究对提高山梨醇催化加氢裂解选择性具有参考意义.

关键词: 乳酸, 碱, 山梨醇, 催化氢解, 镍催化剂

Abstract:

Lactic acid is produced as a major byproduct during sorbitol hydrogenolysis under alkaline conditions. We investigated the effects of two different alkaline additives, Ca(OH)2 and La(OH)3, on lactic acid formation during sorbitol hydrogenolysis over Ni/C catalyst. In the case of Ca(OH)2, the selectivity of lactic acid was 8.9%. In contrast, the inclusion of La(OH)3 resulted in a sorbitol conversion of 99% with only trace quantities of lactic acid being detected. In addition, the total selectivity towards the C2 and C4 products increased from 20.0% to 24.5% going from Ca(OH)2 to La(OH)3. These results therefore indicated that La(OH)3 could be used as an efficient alkaline additive to enhance the conversion of sorbitol. Pyruvic aldehyde, which is formed as an intermediate during sorbitol hydrogenolysis, can be converted to both 1,2-propylene glycol and lactic acid by hydrogenation and rearrangement reactions, respectively. Notably, these two reactions are competitive. When Ca(OH)2 was used as an additive for sorbitol hydrogenolysis, both the hydrogenation and rearrangement reactions occurred. In contrast, the use of La(OH)3 favored the hydrogenation reaction, with only trace quantities of lactic acid being formed.

Key words: Lactic acid, Alkali, Sorbitol, Catalytic hydrogenolysis, Nickel catalyst