A Novel Catalytic Reactor For Conversion Of CO2 Into Benzene

Almost 15 million metric tons per year of essentially pure CO2 is captured in the United States from ethanol, hydrogen, ammonia, and natural gas processing plants. Some of this CO2 is used for merchant applications such as food and beverage and other applications, but a large portion of this captured CO2 is emitted to the atmosphere. This CO2 can be converted into high value chemicals, but the key challenge is to find cheap, carbon-free H2 for this conversion. Therefore, CO2 utilization has been confined to using hydrogen generated primarily by electrolysis from renewable energy like wind or solar, which is still not cheap enough to make most CO2 utilization routes cost-competitive with conventional commercial products. Susteon Inc. is proposing a novel catalytic reactor design with a microporous alumina membrane separating a dehydroaromatization (DHA) reactor from a methanation reactor. The DHA reaction, CH4 = C6H6 + 9H2, converts methane in natural gas into benzene and H2. Currently, efforts to catalytically exploit this reaction are limited by low methane conversion due to thermodynamics (high H2 partial pressure), catalyst coking, and reaction endothermicity. The microporous alumina membrane enables H2 diffusion from the DHA reactor, which will enhance methane conversion, into the methanation reactor, where this H2 is reacted with CO2 to generate more methane. The consumption of the H2 in the methanation reactor maintains an extremely low concentration of H2 optimizing the H2 diffusion rate and methane conversion in the DHA reactor. Because the methanation reaction is also very exothermic, the methanation reactor generates large amounts of heat for the DHA reaction. We also plan to incorporate inhibiting species in the CO2 feed to the methanation reactor that will strategically diffuse back into the DHA reactor significantly reducing the coking reaction. In Phase 1, we plan to experimentally demonstrate increased methane conversion into benzene caused by extraction of hydrogen using microporous alumina membrane and reduced catalyst coking by the controlled counter diffusion of an inhibiting species from the CO2 feed in the DHA reactor along with using H2 and CO2 for demonstrating methanation reaction under these conditions. The anticipated benefits of this novel catalytic reactor and integrated process design enable upgrading methane and CO2 into benzene and other aromatics, with a high profit margin, while effectively utilizing 1.65 tons of CO2 for ton of methane converted. The potential for small-scale modular application of this process also enables installation at remote and/or distributed sites to exploit stranded natural gas reserves or alternatively existing industrial CO2-rich sources while creating American jobs and more effectively utilizing American natural resources.