CO2 utilization in syngas conversion to dimethyl ether and aromatics: Roles and challenges of zeolites-based catalysts

Several studies have proven a strong correlation between global warming and CO2 emissions. Annually, 38 billion tons of CO2 are approximately emitted into the atmosphere. Utilizing CO2 via chemical conversion to clean fuels and value-added aromatics can substantially contribute to controlling the problem. Considering the thermodynamic and environmental limitations of hydrogenation of CO2 alone to value-added aromatics and fuels, CO2 utilization has currently emerged as a promising and practical approach for the production of fuels and aromatics with simultaneous utilization of both CO and CO2 wastes. As such, the approach is economically preferable. CO2 could be converted directly to fuels by the hydrogenation process or as a part of a syngas mixture. Dimethyl ether (DME) is a clean fuel with a higher energy density, which could be used as a substituent for several fuels such as diesel. In the same vein, value-added aromatics such as benzene, toluene, and xylene (BTX) can be produced from a similar process. Herein, we report a review that collects the most recent studies for the conversion of CO2 to DME and aromatics via zeolite-based bifunctional catalysts. We highlighted the main routes for producing DME and aromatics, as well as thoroughly discussed the conducted studies on CO2 hydrogenation and CO2-rich syngas utilized as feedstock for conversion to DME and aromatics. The CO2 hydrogenation mostly occurs through the methanol-mediated reaction route but is most often limited by low selectivity and catalyst deactivation, particularly in the utilization of CO2 alone for the reduction reaction. The review takes an overview of the progress made so far and concluded by identifying the roles and challenges of zeolite-based catalysts for CO2 utilization and conversion to DME and aromatics. Accordingly, despite the incredible growth the field received in the last couple of years, however, many research challenges and opportunities associated with this process are still abounded and required to be addressed. Special attention is required for the development of approaches to block diffusion of H2O through zeolite to suppress the excess formation of CO2 in CO2-rich syngas hydrogenation to DME and aromatics, exceed the product distribution limits, and suppress catalysts deactivation.