Available methods for the conversion of dichloropropane to allene and methylacetylene

Abstract

. The nature of the formation of allene and methylacetylene during the dehydrochlorination of 1,2-dichloropropane and intermediate products (1-chloropropene-1, 2-chloropropene-1, 2-chloropropane, and 3-chloropropene-1) on γ-Al2O3, CaX and expanded clay made it possible to establish that the main source of allene formation on CaX and expanded clay is 2-chloropropene-1, and methylacetylene - 1-chloropropene-1, and on γ -Al2O3, allene formation appears mainly from 2-chloropropane, methylacetylene - from 2-chloroprene. The highest value of the allene: methylacetylene ratio was obtained during the dehydrochlorination of 1,2-dichloro propane and 2-chloroprene on CaX and expanded clay (6.90 and 7.30; 7.70 and 8.19, respectively), while on alumina this indicator is much lower and does not exceed 0.2, and the total the content of the allene-methylacetylene fraction in the presence of the latter is also the lowest. It is also noteworthy that, regardless of the feedstock under study, the course of the dehydrochlorination reaction in the presence of aluminum oxide is characterized mainly by the formation of methylacetylene and an insignificant formation of allene, which is probably a consequence of all methylacetylene isomerization occurring on the catalyst surface. The totality of these data made it enable to establish that the DCP conversion mechanism is carried out in different ways regarding the acid-base nature of the active sites of the catalytic systems: in the presence of γ-Al2O3 - with the participation of Lewis acid sites, and CaX and expanded clay - with the participation of Brønsted acid sites.