New Findings on Transforming Carbon Dioxide into Sustainable Jet Fuel

Abstract
Catalytic CO2 hydrogenation facilitated by Fe3O4 produces long-chain hydrocarbons and light olefins through the combination of the reverse water–gas shift reaction and Fischer–Tropsch synthesis in a single reactor. Complementing Fe3O4-based catalysts, zeolites can be incorporated to modulate the product distribution of long-chain hydrocarbons in a dual-bed configuration. However, zeolites with strong acid sites induce the cracking of extended hydrocarbon chains, thereby impeding the production of hydrocarbons exceeding 12 carbon atoms. This paper introduces a novel Pt/WO3-ZrO2 (PtWZ) catalyst to produce liquid isoparaffins, aligning with the requirements of sustainable fuel characteristics. The precise adjustment of Pt and W contents in PtWZ enhances the hydrogenation and isomerization of linear olefins, amplifying the yield of isoparaffins. A dual-bed reactor integrating PtWZ (0.01 wt % Pt) with Na-promoted Fe3O4 catalyst achieved a CO2 conversion rate of 40% and a CO selectivity of 10%, while maximizing isomerization performance, attaining 42% isoparaffinic selectivity within liquid hydrocarbons at operating conditions of 340 °C, 20 bar, weight hourly space velocity = 4500 mL·h–1·gcat–1. In contrast to zeolite catalysts prone to coke deposition during the reaction, the PtWZ catalyst exhibited remarkable stability, sustained activity without discernible deterioration, and negligible coke deposition, even after continuous operation for more than 100 h. This outcome delineates an optimized catalyst technology for the sustainable production of fuel from CO2, offering a viable alternative to the prevailing dependence on fossil fuels.

A groundbreaking catalyst technology for the production of sustainable aviation fuel (SAF) has been developed, promising a significant reduction in carbon emissions through the utilization of carbon dioxide. This innovation is expected to contribute to carbon neutrality by capturing CO2 from the atmosphere and converting it into isoparaffins, high-value hydrocarbons.

A research team, led by Professor Kwangjin An in the School of Energy and Chemical Engineering at UNIST, in collaboration with the Carbon Neutrality Research TFT of LG Chem Ltd., has developed a catalyst specifically designed for producing isoparaffins suitable for SAF production from carbon dioxide. This new catalyst has successfully replaced traditional zeolite catalysts when used in conjunction with iron-based systems, resulting in a significant increase in the isoparaffin production rate.

Figure 1. Schematic diagram showing the overall production process of isoparaffin via direct hydrogenation of CO2 using solid acid catalysts.

Notably, aircraft fuel produced using platinum-based tungsten-zirconia (Pt/WZ) catalysts is anticipated to reduce carbon emissions by up to 80% compared to conventional fossil fuel-based aviation fuel. This innovative process features enhanced efficiency by enabling the direct conversion of carbon dioxide into isoparaffins.

The catalyst shows strong potential for commercialization due to its low carbon deposition and stable reactivity over extended periods. Its applications are expected to benefit not only the aviation industry but also other sectors of transportation in the fight against carbon emissions.

Professor An stated, “We have developed a new catalytic method that addresses the limitations of existing zeolite catalysts, which are prone to coke formation during reactions, thus maximizing the production rate of isoparaffins.” Won-Hee Kim from LG Chem Ltd., the lead researcher, emphasized, “This technology holds significant industrial application value as it can enhance fuel efficiency while minimizing additional costs associated with refining.”

Figure 2. Catalytic performance of various solid acid catalysts used with a NaFe catalyst for CO2 hydrogenation. Liquid hydrocarbon distribution of solid acid catalysts (Y-axis on the left represents the hydrocarbon distribution of the liquid product, and black dots represent the fraction of isoparaffins).

Currently, the air transport sector is responsible for 24.5% of total carbon dioxide emissions, making the commercialization of SAF a pressing challenge for achieving carbon neutrality. The International Air Transport Association (IATA) is intensifying regulations to promote the adoption of SAF.

This research was conducted with technical support from the Korea Basic Science Institute (KBSI) and the findings were published online in ACS Catalysis on August 9, 2024. The study was additionally supported by the National Research Foundation of Korea (NRF) and the Ministry of Trade, Industry and Energy (MOTIE).

Journal Reference
Hojeong Lee, Changhun Hur, Yong Hee Lee, et al., “Enhanced Isoparaffin Selectivity in CO2 Hydrogenation by Combining Na-Promoted Fe3O4 and Pt/WO3-ZrO2 Catalysts,” ACS Catal., (2024).