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 LaCl3-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 379.8 kJ·mol-1 and 686.07 kJ·mol-1 for traditional Nieuwland catalyst and for LaCl3-Nieuwland catalyst

respectively

indicating that the latter is of ability to intensify selectivity of acetylene dimerization to MVA.