LaCl_3改性Nieuwland催化剂催化乙炔二聚反应

Acetylene dimerization catalyzed by LaCl_3-modified Nieuwland catalyst

乙炔二聚反应制备乙烯基乙炔(MVA)是氯丁橡胶合成工艺中的重要过程。传统的乙炔二聚反应因Nieuwland催化体系与MVA形成的配合物的活性高,会进一步与乙炔反应形成二乙烯基乙炔(DVA),甚至高聚物。控制Nieuwland催化剂的活性,减少DVA和高聚物的产生,提高反应选择性,可实现节能减排。加入LaCl3以改善Nieuwland催化剂活性,调控乙炔二聚的催化行为。实验结果表明,LaCl3-Nieuwland催化剂可抑制DVA的产生,减少DVA与乙炔继续反应形成高聚物,可提高MVA的选择性。在反应温度80℃下,MVA/DVA值从6左右提高至19,MVA选择性由80%提高至95%,高聚物的生成量大幅度减少。LaCl3-Nieuwland催化剂具有良好的低温反应活性,60℃时,反应产物气相中MVA的体积分数达到10%。计算结果表明,传统Nieuwland催化剂存在下,MVA-乙炔反应生成DVA能垒较乙炔二聚形成MVA高379.8 kJ·mol-1。而LaCl3-Nieuwland催化剂存在下,MVA-乙炔反应生成DVA能垒较乙炔二聚形成MVA高686.07 kJ·mol-1。LaCl3-Nieuwland催化体系可强化乙炔二聚形成MVA。

Acetylene dimerization is one of the key processes for production of neoprene via monovinylacetylene （MVA）. In traditional acetylene dimerization process, much divinylacetylene （DVA）, even polymer appeared catalytic system due to the high activity of Nieuwland catalyst for the formation of coordination compounds with MVA. In order to realize energy saving and emission reduction it is required to control the activity of Nieuwland catalyst and the formation of DVA and polymer, and to improve selectivity of MVA. So, LaCl3 selected as modifier and added into Nieuwland catalyst system to control its reaction activity for acetylene polymerization. The results show that LaC13- Nieuwland catalyst can inhibit DVA formation and reduce polymer amount, leading to improvement of MVA selectivity. The ratio of MVA/DVA in gas phase product increases from 6 to 19, and MVA selectivity goes up from 80% to 95% at 80℃. While at 60℃ the modified catalyst shows excellent low temperature activity, and MVA content in gas product is 10%. A theoretical calculation shows that the reaction energy barrier of MVA and acetylene to form DVA is higher than that of acetylene dimerization, which is 379.8kJ . mol-l and 686.07 kJ . mo1-1 for traditional Nieuwland catalyst and for LaC13- Nieuwland catalyst, respectively, indicating that the latter is of ability to intensify selectivity of acetylene dimerization to MVA.