Exergy, economic and environmental analysis of an integrated pressure-swing reactive distillation process for the isobutyl acetate production via methyl acetate transesterification

As a greener bio-based solvent, isobutyl acetate (ISBAC) was widely applied in biorefineries around value-added production for environmental protection and ecological safety. The convention production of ISBAC, which was obtained by the reaction of alcohols and acids, can form by-product water to cause the multiple heterogeneous azeotropes and further enormously increase separation difficulty and production costs. This work adopted the transesterification of methyl acetate (MeAC) from the by-product (typical compositions MM20 (15.64 mol% MeAc, 84.36 mol% MeOH) and MM80 (65 mol% MeAC, 35 mol% MeOH) of polyvinyl alcohol (PVA) manufacture and isobutanol (ISBOH) to product ISBAC to avoid the multiple heterogeneous azeotropes. The ISBAC production by MeAC in MM20 and MM80 reacted with ISBOH adopted reactive distillation (RD) combining pressure-swing to break the limits of chemical equilibrium and azeotrope separation. Furthermore, heat integration, thermal coupling, and heat pump technologies were used to systematically recover waste heat and achieve energy-saving for ISBAC production processes. The exergy, economy, and environment evaluation displayed that the heat integration of MM20 pressure-swing RD was the best attractive process by reducing 19.35% total annual cost (TAC), 34.58% CO2 emissions, and improving 33.16% thermodynamic efficiency. The heat source of the low-pressure column and preheating process feed using top steam of the high-pressure column（heat integration-F） of MM80 pressure-swing RD process was the most promising process due to the decrease of 5.40% in TAC, 16.70% in CO2 emissions and obtained the improvement of 4.50% thermodynamic efficiency comparing with the conventional process.