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Nitrogen oxides (NO x ) in fluid catalytic cracking (FCC) units, which are major atmospheric pollutants, are hazardous to the human body and environment. In this work, the CuO−CeO 2 catalyst prepared by the co-precipitation method (CuCe−CPM) is applied in the CO-selective catalytic reduction (CO-SCR) reaction. NO and CO can be completely converted to exhaust gas, CO 2 and N 2 , in the temperature range of 600−700 °C. Subsequently, we propose a new method of application of the generated exhaust gas, where the exhaust gas is employed to enhance shale gas recovery and achieve sequestration within the shale reservoir. A series of comparisons of CH 4 displacement efficiency and sequestration capacity of reaction gas (CO + NO) and generated waste gas (CO 2 + N 2 ) in kerogen slit nanopores were performed. It is found that the displacement efficiency of CO 2 + N 2 as the driving gas is higher than that of CO + NO within the formation depth from 0.33 to 3 km. The displacement efficiency of CO 2 + N 2 reached 70 and 76% when the reservoir depths reached 1 and 3 km, respectively, with a pressure increase of 30 MPa and a temperature increase of 54.6 °C during this period. The displacement process is dominated by the interaction between kerogen and driving gas. The sequestration capacity of CO 2 + N 2 is slightly weaker than that of CO + NO, but direct CO 2 + N 2 sequestration has the advantages of being harmless and less corrosive and with fewer operational safety hazards. The proposed scheme may provide a feasible guide to the NO x treatment process and the application of the generated exhaust gas from FCC units.

Shale gas, as a promising alternative energy source, has received considerable attention because of its broad resource base and wide distribution. The establishment of shale models that can accurately describe the composition and structure of shale is essential to perform molecular simulations of gas adsorption in shale reservoirs. This Review provides an overview of shale models, which include organic matter models, inorganic mineral models, and composite shale models. Molecular simulations of gas adsorption performed on these models are also reviewed to provide a more comprehensive understanding of the behaviors and mechanisms of gas adsorption on shales. To accurately understand the gas adsorption behaviors in shale reservoirs, it is necessary to be aware of the pore structure characteristics of shale reservoirs. Thus, we also present experimental studies on shale microstructure analysis, including direct imaging methods and indirect measurements. The advantages, disadvantages, and applications of these methods are also well summarized. This Review is useful for understanding molecular models of gas adsorption in shales and provides guidance for selecting experimental characterization of shale structure and composition.