(678d) A Combined Molecular Simulation and Process Simulation Study of Benzene Removal from Vinyl Acetate in MOFs

Vinyl acetate (VAc) is a widely used kind of organic raw material which is mainly synthesized by the carbide acetylene method in China. However, the trace amounts of benzene (about 100 ppm) impurities in the VAc product have seriously limited its application in fine chemical industry. It is an urgent requirement to separate trace benzene from VAc down to 10 ppm. Pressure swing adsorption (PSA) is an efficient method to remove trace impurities and its main challenge is to find an effective adsorbent. Metal-organic frameworks (MOFs) possess many advantages compared with traditional materials and are believed to have perspective applications in this field, although few investigations are reported. In this work, multi-scale simulation method including molecular level and process simulation are used to screen an effective adsorbent which could be employed in the PSA process. This work would provide the guidance for the removal of trace benzene.

Grand Canonical Monte Carlo (GCMC) and configure bias Monte Carlo (CBMC) are combined to investigate the adsorption behavior of benzene and VAC in different MOFs: Cu-BTC, Zn-BDC, IRMOFs and M-DOBDC. The effects of exposed metal sites, organic chain length and different functional groups attached to organic chains on adsorption and separation behaviors were studied. The highest selectivity factor of benzene over VAc is as high as 12, showing the great ability to remove trace amount of benzene from VAc product.

After the molecular simulation screening work, the most effective MOF material is selected for the following PSA process to remove trace benzene in an annual output of 250,000 tons of VAc plant. In the designed PSA process, benzene concentration in the VAc product could be reduced less than 1 ppm (wt%) . The result indicate that MOF is an excellent adsorbent for removing trace benzene, and the purity is able to meet the requirement of high-quality VAc product.