LCA of a Semi-Batch Reactor and a Semi-Batch Recycle Reactor to Produce Polyamines

Polyamines are applied as curing agents for epoxy resins, to produce functionalized polyamides and chelating agents. These compounds are a valuable substrate for the synthesis of several fine chemical additives. Triethylenetetramine (TETA) is an additive for asphalts, fuels and textile fibres. Moreover, they are market products as surfactants and corrosion inhibitor. We investigated the unselective synthesis of polyamines through alkylation of 1,2-dichloroethane with a diamine in a standard semi-batch reactor (SBR) as well as in a semi-batch recycle reactor (SBRR) (Figure 1), aiming at increasing TETA productivity and showing that the latter leads to a selectivity of 70 % of TETA compared to the 50 % obtained with SBR. The main purpose of the industrial research is to develop processes that lead to the production of TETA with the highest concentration achievable. However, information lacks regarding the environmental burdens of the synthesis processes. Life cycle assessment (LCA) calculates the energy and material consumptions, the quantity and type of emissions and other important factors all related to the entire life cycle of a product, a process or a service (from the extraction of raw materials to the distribution / use / maintenance / disposal / recycling). We apply LCA to assess the impact of a lab-scale plant that produces enriched air and we optimized the process concerning the environmental burdens. Here we study and compare the impacts of SBR and SBRR processes to synthesize TETA. The SBRR configuration needs more units than the SBR one, indeed there is an additional reboiler (and consequently its heat/electricity) and a Claisen condenser (with a cooling water flowrate). On the other hand, SBRR reaches better TETA selectivity. In this work, we want to investigate these contrasting contributions using the LCA analysis tool to evaluate and compare the two processes, for the first time. We select 1 kg of TETA as functional unit and thus we correct the impacts calculated by the selectivity of the two processes. A Monte Carlo simulation estimate the confidence interval. SBRR configuration is environmentally favourable to the SBR.