On Reactivity of Piperazine Aminogrups in Interaction With Ethylene Oxide

Abstract

Currently, the main method for producing N-(2-hydroxyethyl) piperazine in industry is the cyclization of ethylene glycols and ethanolamines in the presence of ammonia and hydrogen. The main disadvantage of this method is the production of a wide range of products and, as a consequence, low selectivity for N-(2-hydroxyethyl) piperazine. In this work, the object of study is the piperazine hydroxyethylation reaction in the presence of an “inert” solvent under the reaction conditions, as the most selective way to obtain N-(2-hydroxyethyl) piperazine. The solvent molecule acts as a homogeneous catalyst of the acid type and is characterized by the presence of a mobile proton for opening the oxirane ring of ethylene oxide by the acid-base mechanism. There was studied the dependence of the yield of reaction products on the parameters of the process in the temperature range of 60 - 130 ° C; solvent concentration (water, methylcellosolve) 1 - 75% wt. and molar ratio of reagents (ethylene oxide / piperazine) 0.2 - 1. Analysis of the reaction mass by gas-liquid chromatography showed that the main by-product is N, N'-bis (2-hydroxyethyl) piperazine - the product of the hydroxyethylation of N-(2-hydroxyethyl ) piperazine in the second amino group. The hydroxyl group of hydroxyethylation products are formed in a negligible amount. It was found that the composition and concentration of the solvent, as well as the temperature regime of hydroxyethylation, do not significantly affect the selectivity of the process. It was shown that piperazine hydroxyethylation is described by the kinetics of series-parallel reactions. The results obtained in the study may be of interest for the development of piperazine hydroxyethylation process technology, in terms of simplifying the mathematical model of the reactor unit by excluding from the description factors that do not significantly affect the selectivity of the formation of N-(2-hydroxyethyl) piperazine.