(324d) Production of Dialkly Carbonates Via Reactive-Extractive and Pressure-Swing Distillations Using Unifac-CI VLE Model Predictions

Dialkyl  carbonates like dimethyl carbonate (DMC) and diphenyl carbonate (DPC) are environmentally benign and biodegradable products and have found wide applications in polycarbonates plastics and as  important solvents in the emerging  battery markets. In particular, DMC is the solvent of choice for lithium ion battery solutions. The synthesis of dialkyl carbonates are generally carried out by continuous reactive distillation that produce  azeotropic mixtures of  the dialkyl carbonates and linear alcohols followed by the  recovery of the dialkyl carbonates. The recovery of a typical  dialkyl carbonate from the azeotropic mixture is achieved by either using  pressure swing distillation process where the pressure sensitive azeotropic mixture is separated or by using extractive distillation process where the azeotropic mixture is contacted with an entrainer like phenol, aniline and diethyl oxylate to produce high purity dialkyl carbonate. In all of  these distillation processes (reactive, pressure-swing, and extractive distillations),  accurate predictions of the binary VLE systems involving the carbonate group (-OCOO-) and other components  especially the linear alcohols in the production of high purity dialkyl carbonates  are very important. The UNIFAC group interaction parameters (GIPs) involving the carbonate group are very limited in the literature. We have  used the UNIFAC-CI model where all the group interaction parameters (GIPs) are predicted  and/or fine tuned using the GC^Plus/UNIFAC-CI method in the latest ICAS regressed atom interaction parameters (AIPs). Typical  GIPs generated will be presented. With these parameters,  we were able to accurately predict the VLE of the azeotropic mixtures. The results were used for the design of the reactive-extractive  and  reactive-pressure swing distillations to produce high purity dialky carbonates. The energy consumption of  the extractive distillation is less than the pressure-swing distillation. Overall, a heat integrated reactive and extractive distillation system provides the best option for energy savings than those without the heat integration.