Experimental investigation, modeling and scale-up of hydrophilic vapor permeation membranes: Separation of azeotropic dimethyl carbonate/methanol mixtures

Abstract

The separation of azeotropic mixtures is a challenging task that is currently performed by special distillation processes, such as heteroazeotropic, extractive or pressure-swing distillation. In recent years, membrane materials that are used to separate different combinations of chemical compounds have constituted an energy-efficient and competitive alternative to special distillation processes. Vapor permeation is a promising type of membrane separation processes which enables to overcome limitations caused by the thermodynamic phase equilibrium. This characteristic facilitates the separation of azeotropic mixtures. However, the membrane needs to be large to handle high throughputs or to achieve high purities. Thus, the use of membranes in combination with established unit operations in so-called membrane-assisted separation processes is advantageous. Nevertheless, in addition to the reliable selection of a suitable membrane polymer for a given design task, a model-based scale-up is still challenging and complicates the design of said membrane separations. These disadvantages limit the application of vapor permeation in the chemical industry. Therefore, the aim of this paper is to enable scale-up by systematically identifying the influence of vapor permeation operating parameters at two different experimental scales with a scale-up factor of 50. Based on these experiments, a rigorous model was developed using experimental data from lab-scale to predict the separation characteristics in pilot-scale. These findings were validated against experimental data from this scale. In this work, the separation of dimethyl carbonate and methanol showing a low-boiling azeotrope with high methanol content was used as a case study. The separation of these two compounds is of significant interest because valuable dimethyl carbonate is usually produced from methanol feedstocks, thus necessitating the separation of both components.