How do the SOx and NOx in flue gas influence the adsorptive-catalytic performance of integrated carbon capture and in situ dry reforming?

(Press-News.org) Integrated carbon capture and utilization has become a promising technology to achieve carbon neutrality. However, conventional studies focused on the development of novel dual-functional materials while neglecting the impact of common impurities such as sulfur oxides (SOx) and nitrogen oxides (NOx), thereby limiting the practical industrial applicability of ICCU technology. A team of scientists has investigated the impact of SO2 and NO2 on the ICCU-dry reforming of methane (ICCU-DRM) process using a representative Ni-Ca dual-functional material. Their work is published in the journal Industrial Chemistry & Materials on 04 July 2025.

“We aim to understand the influence of SO2 and NO2 in flue gas on the integrated carbon capture and utilization,” explains Hui Zhou, an associate professor at Tsinghua University. Though SOx and NOx, as two of the most important pollutants in flue gas, have been proven to significantly influence the capture and conversion performance, few studies investigate the influence of impurity components in the realistic flue gas. The research team has performed a series of tests under different SO2 and NO2 concentrations to uncover the adsorptive-catalytic performance influence of the pollution in flue gas, and tried to understand the influence mechanism via systematic characteristics.

Fixed-bed reactor results revealed that a low concentration of SO2 (100 ppm) in flue gas showed a minor influence on the CO2 conversion, but could effectively inhibit the methane decomposition side reactions, therefore significantly reducing the carbon deposition. Moreover, the low concentration of SO2 in flue gas could effectively improve the stability of CO2 capture. However, with the increase of SO2 concentration to 500 ppm, the adsorption capacity and catalytic reforming capacity of the DFMs decreased significantly, and the materials were significantly deactivated after 10 cycles. The influence of NO2 in the flue gas was further investigated. NO2 exhibited a similar mode of influence to SO2, while its detrimental effects were significantly less pronounced.

In particular, the performance differences can be explained by the reaction kinetics. The research group compared the methane reforming kinetics of the 1st and 10th cycles, suggesting that catalytic sites rapidly deactivated with SO2. Interestingly, this deactivation exhibited a more pronounced inhibitory effect on CH4 decomposition rather than on the dry reforming, resulting in relatively unchanged CO2 conversion but a significantly decreased H2:CO ratio. This shift indicates a suppression of the side reaction responsible for excess methane consumption and carbon deposition.

To understand the influence mechanism of SO2 and NO2, the research group conducted a series of systematic characterizations to reveal the underlying mechanisms. In situ XRD found that CaSO4 was formed at the onset of the carbonation stage, which gradually converted into CaS under a reduced atmosphere. “Dynamic crystal changes of sulfur-containing species reveal the complexity of understanding the inner mechanism of the ICCU process,” said Zhou. The research group concluded that both SO2 and NO2 promote the formation of a coating layer of calcium-containing compounds on the surface of Ni nanoparticles, accounting for the partial or total deactivation.

Looking ahead, the research team hopes that their work might provide insights into the industrial applications of ICCU systems under realistic flue gas conditions. “We next plan to develop anti-SO2 and NO2 dual-functional materials based on the proposed mechanism and test them under realistic flue gas. We believe our efforts can promote the practical industrial application of ICCU technologies in power plants and other chemical processes,” said Zhou.

The research team includes Bocheng Yu, Muqing Yang, Yijian Qiao, Yaozu Wang, Yongqing Xu, Xuan Bie, Qinghai Li, Yanguo Zhang and Hui Zhou from Tsinghua University, and Shuzhuang Sun from Zhengzhou University.

This work is funded by the Beijing Natural Science Foundation, the National Natural Science Foundation of China, the National Key R&D Program of China, the Special support program for young talent innovation teams from Zhengzhou University, the Carbon Neutrality and Energy System Transformation project, the International Joint Mission on Climate Change and Carbon Neutrality, and the Tsinghua University Initiative Scientific Research Program.

Industrial Chemistry & Materials is a peer-reviewed interdisciplinary academic journal published by Royal Society of Chemistry (RSC) with APCs currently waived. ICM publishes significant innovative research and major technological breakthroughs in all aspects of industrial chemistry and materials, especially the important innovation of the low-carbon chemical industry, energy, and functional materials. Check out the latest ICM news on the blog.

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