(453c) Alcohol Synthesis in a High-Pressure Membrane Contactor Reactor Using Waste CO2 Feeds

We describe here a post-combustion CO₂ capture and utilization (CCU) technology that converts waste CO₂ into methanol (MeOH), a valuable chemical, thus providing a way to monetize the carbon captured to offset process costs. Methanol (MeOH) finds broad use as a transportation fuel and as an important raw material used in the production of other fuels and chemicals. Methanol synthesis (MeS) has been discussed recently for application to CCU, but thermodynamic limitations make it difficult to convert in a single pass a large CO₂ fraction. Conventional catalysts show slow kinetics in converting CO₂-rich syngas (or pure CO₂) into MeOH. Our Group has developed a novel MeS process, employing a membrane contactor reactor (MCR) system that attains carbon conversions significantly higher than equilibrium. In this study, a novel high-pressure MCR is used, in which a mesoporous inorganic membrane with the desired characteristics serves as an interface contactor between the MeS environment in the shell-side and a sweep liquid flow in the permeate-side. Two different types of sweep liquids have been employed in the study: High boiling point (BP) petroleum-derived solvents and ionic liquids (IL), chosen because MeOH has high solubility in both of them, while the syngas components have negligible solubility. Compared to the petroleum solvents, the IL have higher decomposition temperatures, which implies less demanding downstream processing for MeOH recovery; their lower vapor pressure means lower solvent loss, and their higher thermal capacity affords a broader range of MeS operating conditions and more efficient thermal management.

In this work, we study a novel direct CO₂ into MeOH conversion process that overcomes the limitations faced by current CO₂-based MeS processes. Our focus here is to process pure CO₂ streams by combining the MCR with a separate reactor, which converts the CO₂ into a syngas via the reverse water gas shift (RWGS) reaction. In our proof-of-concept effort, we have developed and tested a RWGS catalyst appropriate for use in the proposed process. We have also generated additional MeS kinetic rate data, beyond those in our earlier efforts, focusing on validating experimentally the ability of the MeS-MCR system to process as a feed the RWGSR exit stream. Our experimental efforts focus on the study of the performance of the integrated (RWGSR/MeS-MCR) system. The combined system is simulated using a data-validated model which is also utilized in a preliminary technical and economic analysis (TEA) of the process.