Selective synthesis of polyamines in multipurpose plants

A number of reaction processes undergo yield drops since an intermediate target species can further react with one of the reactants generating lower volatility by-products. Such reactions are typically fast and non-selective, so that a gradual conversion of the reactants is recommended because of safety and quality constraints; when dealing with relatively low-volumes of a highly fragmented set of products, a semibatch reactor is normally adopted where the reaction selectivity is increased by increasing the excess of the selective reactant, therefore lowering the plant productivity. For increasing the process selectivity without reducing the plant productivity a different reactor configuration has been recently proposed: the so-called semibatch recycle reactor. However, the good performance of this configuration has never been experimentally confirmed. In this work, the unselective industrial synthesis of polyamines through alkylation of 1,2-dichloroethane with a diamine has been experimentally investigated both in a standard semibatch reactor as well as in a semibatch recycle reactor, showing that the latter can lead to a significant increase of both the process selectivity and productivity.