Key Takeaways & Executive Findings
- •• • The In2Zr1Ox/SAPO-11 catalyst achieved 24% COx conversion and 68% C5−C11 selectivity at 380 °C, 3 MPa, and GHSV of 2400 mL/(min·g), surpassing the ~45% ASF limit for gasoline-range hydrocarbons, which is critical for cost-effective CO2-to-fuel conversion. • • Co-feeding CO/CO2 at a ratio of 0.5 suppressed CO byproduct formation, enhancing C5−C11 selectivity by 8.0% and 16.0% compared to In2O3/SAPO-11 and ZrO2/SAPO-11, respectively, demonstrating the synergy of In-Zr mixed oxides. • • The catalyst exhibited high isomerization activity: isoparaffins constituted 32.6% of the gasoline fraction with an iso/normal ratio of 12.3, improving octane number and combustion performance, a key factor for fuel quality. • • Stability testing over 150 h showed only a slight decline from 24% to 23% COx conversion and from 68% to ~65% C5−C11 selectivity, indicating robust industrial durability for long-term operation.
Abstract
The conversion of CO2 into gasoline-range hydrocarbons represents a sustainable pathway to achieve deep decarbonization in the transportation sector. Nevertheless, the traditional Fischer-Tropsch synthesis (FTS) suffers from a broad product distribution, which restricts the achievable selectivity toward C5−C11 gasoline-range hydrocarbons to roughly 45%. This study presents the development of a bifunctional catalyst that integrates In2O3/ZrO2 metal oxides with SAPO-11 molecular sieves, aiming at efficiently converting CO2/CO mixtures into C5−C11 gasoline hydrocarbons. Catalysts with varying In/Zr ratios were prepared via co-precipitation. By employing a COx (CO/CO2) co-feeding strategy (CO/COx = 0.5), the formation of by-product CO was significantly suppressed, thereby enabling the selectivity for gasoline hydrocarbons to exceed the maximum predicted by the Anderson-Schulz-Flory (ASF) model. Notably, under identical reaction conditions, the In2Zr1Ox/SAPO-11 catalyst exhibited higher performance compared with In2O3/SAPO-11 and ZrO2/SAPO-11. The COx conversion was elevated by 1.7% and 0.2%, while the selectivity toward C5–C11 hydrocarbons was enhanced by 8.0% and 16.0%, respectively. Furthermore, the In2Zr1Ox/SAPO-11 catalyst delivered a single-pass performance of 24% COx conversion and 68% selectivity for C5−C11 hydrocarbons at 380 °C, 3 MPa and a gas hourly space velocity (GHSV) of 2400 mL/(min·g). Within this product distribution, isoparaffins accounted for 32.6% of the total components, corresponding to an isoparaffin/neoparaffin ratio of 12.3. After 150 h of stability testing, the catalyst maintained a single-pass COx conversion of 23% and a C5−C11 selectivity of ~65%, demonstrating excellent catalytic activity and promising potential for industrial application.
1. Introduction
Traditional Fischer-Tropsch synthesis (FTS) for converting CO2-rich syngas into liquid fuels suffers from a fundamental limitation: the Anderson-Schulz-Flory (ASF) distribution caps the maximum selectivity for gasoline-range hydrocarbons (C5−C11) at approximately 45%. This broad product spectrum, which includes significant fractions of light gases (C1−C4) and heavy waxes (C12+), reduces process efficiency and necessitates costly downstream upgrading. The transportation sector's reliance on fossil-derived gasoline further exacerbates carbon emissions, underscoring the urgent need for a selective and sustainable route to produce high-quality gasoline from CO2.
This study addresses the selectivity bottleneck by employing a bifunctional catalyst system that couples In2O3-ZrO2 metal oxides with SAPO-11 molecular sieves. The oxide component hydrogenates COx to methanol, while the acidic SAPO-11 pores convert methanol to gasoline-range hydrocarbons via the methanol-to-hydrocarbons (MTH) mechanism, effectively bypassing the ASF constraints. By optimizing the In/Zr ratio and employing a CO/CO2 co-feed strategy, the catalyst achieves a C5−C11 selectivity of 68% at 24% COx conversion, far exceeding the ASF limit. This approach not only enhances gasoline yield but also promotes isomerization, yielding a high iso/normal paraffin ratio that improves fuel quality, offering a promising pathway for industrial CO2 utilization.
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ZHOU Tingting, LI Xueli, ZHANG Gang, YAO Jingang, YI Weiming (2026). Catalytic conversion of CO2-rich syngas to high-quality gasoline hydrocarbons over In2O3-ZrO2/SAPO-11 catalysts. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60671-8
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Frequently Asked Questions
What is the maximum C5−C11 selectivity achieved with the In2Zr1Ox/SAPO-11 catalyst, and how does it compare to the theoretical ASF limit?
The In2Zr1Ox/SAPO-11 catalyst achieved a C5−C11 selectivity of 68% at 380 °C, 3 MPa, and GHSV of 2400 mL/(min·g), which is significantly higher than the ~45% maximum predicted by the ASF model for traditional FTS. This was enabled by the bifunctional mechanism that converts COx to methanol over In2O3-ZrO2 and then to gasoline-range hydrocarbons over SAPO-11, effectively bypassing ASF constraints.
How does the CO/CO2 co-feeding ratio affect the product distribution and COx conversion?
At a CO/COx ratio of 0.5, the formation of by-product CO was significantly suppressed, leading to enhanced C5−C11 selectivity. Under identical conditions, the In2Zr1Ox/SAPO-11 catalyst showed a COx conversion of 24% and C5−C11 selectivity of 68%, outperforming single-oxide catalysts. The co-feed strategy likely modulates the surface hydrogenation activity, favoring methanol formation and subsequent hydrocarbon synthesis.
What is the role of SAPO-11 in the bifunctional catalyst, and how does it influence the iso/normal paraffin ratio?
SAPO-11 provides acidic sites that catalyze the conversion of methanol to hydrocarbons and its shape-selective pores promote isomerization of straight-chain alkanes to branched isomers. This results in an isoparaffin content of 32.6% and an iso/normal ratio of 12.3, which enhances the octane number and combustion properties of the gasoline product.
What are the long-term stability and deactivation characteristics of the catalyst under industrial conditions?
In a 150 h stability test at 380 °C, 3 MPa, and GHSV of 2400 mL/(min·g), the catalyst maintained a COx conversion of 23% (down from 24%) and a C5−C11 selectivity of ~65% (down from 68%), indicating minimal deactivation. This suggests good thermal and hydrothermal stability, though longer-term tests and regeneration studies would be needed for full industrial validation.
How does the performance of In2Zr1Ox/SAPO-11 compare to single-oxide catalysts like In2O3/SAPO-11 and ZrO2/SAPO-11?
Under identical conditions, In2Zr1Ox/SAPO-11 exhibited higher COx conversion by 1.7% and 0.2% compared to In2O3/SAPO-11 and ZrO2/SAPO-11, respectively. More notably, C5−C11 selectivity was enhanced by 8.0% and 16.0%, respectively. This demonstrates a synergistic effect between In2O3 and ZrO2, which likely improves methanol synthesis activity and selectivity.
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