High Conversion to Aromatics via CO₂-FT over a CO-Reduced Cu-Fe₂O₃ Catalyst Integrated with HZSM-5

Abstract

Direct hydrogenation of carbon dioxide (CO2) to value-added chemicals is a promising strategy to relive the greenhouse effect and replace the diminishing fossil fuels, but the huge CO2 inertness and C–C coupling barrier usually bring about numerous difficulties and count against catalytic performance. Here, a highly active and more economical composite catalyst composed of Cu-promoted Fe2O3 (nCu-Fe2O3) and HZSM-5 was developed for the selective conversion of CO2 to aromatics with 56.61% selectivity at a single pass. An extremely low CO selectivity of 3.51 at 57.30% CO2 conversion outperforming the previously reported conversion was achieved because of the beneficial synergism between Cu and Fe and the distinctive CO reduction prior to reaction which is favorable to the formation of oxygen vacancies for CO2 adsorption and iron carbide for Fischer–Tropsch synthesis (FTS). Additionally, through integrating HZSM-5 synthesized by the phase-transfer method (HZSM-5-pt) with nCu-Fe2O3, the distribution of benzene, toluene, and xylene in aromatics can be noteworthily increased to 54.18% and aromatics selectivity can be increased to 61.94%, without depression of catalyst activity. More significantly, a “H recycling” mechanism was found between oxide and zeolite, which plays a crucial role in “the disposal of H” within dehydrogenative aromatization, facilitating the formation of aromatics. In summary, nCu-Fe2O3/HZSM-5 demonstrates a prospective industrial application in aromatics production from CO2.

Aromatics Production via Methanol-Mediated Transformation Routes

“…), using similar strategies to prepare the catalysts for CO 2 conversion is also promising. The conversion of CO 2 to C 2+ hydrocarbons could involve RWGS reaction first to produce CO, followed by syngas transformation via the FTS route. − Sun et al reported that the combination of a Na-modified Fe 3 O 4 with H-ZSM-5 could produce the gasoline hydrocarbons with a selectivity of 78% at a CO 2 conversion of 22% . It was proposed that CO 2 was first converted to CO via the RWGS reaction on Fe 3 O 4 , followed by hydrogenation of CO to α-olefins (the FTS route) on χ-Fe 5 C 2 .…”

Dynamic structural evolution of iron catalysts involving competitive oxidation and carburization during CO 2 hydrogenation

“…The stronger oxidation capability of CO 2 compared with CO makes the structural evolution more complicated in CO 2 hydrogenation. In general, Fe 3 O 4 and Fe 5 C 2 are the main phases on spent catalysts (22,23). Skrypnik et al (24) investigated the steady-state composition of Fe x O y C z catalysts (mixture of -Fe, iron carbides, and oxides) along the catalyst bed, which suggests that Fe 3 O 4 , FeO, and Fe are converted into iron carbides under reaction conditions.…”

Unraveling the Role of Zinc on Bimetallic Fe5C2–ZnO Catalysts for Highly Selective Carbon Dioxide Hydrogenation to High Carbon α-Olefins

“…The production of LAOs directly from CO 2 hydrogenation via the reverse water–gas-shift (RWGS) reaction followed by FTS has proven to be a promising process for CO 2 utilization; meanwhile, iron-based catalysts are a preferential alternative due to their prominent capability of catalyzing both RWGS and FTS − reactions and excellent selectivity toward olefins. Due to the high activity and tunable chain growth ability of χ-Fe 5 C 2 , − it is widely applied in CO 2 hydrogenation to high value-added hydrocarbons. − More recently, Guo et al have even reported a LAO synthesis process directly from CO 2 hydrogenation, while selectivities of 50.3% for C 4–18 alkenes and 80% for LAOs were achieved over a biopromoted Fe catalyst (Fe/C-bio), probably due to the interaction of Fe active species and carbon.…”