Molecular Simulation-Based Multidimensional Screening of Decarbonization Adsorbents for Oil-Associated Gas Under Wide Humidity Range

In order to solve the problems of low calorific value and pipeline corrosion caused by high concentration of CO2 in oil-associated gas, and promote the resource utilization of associated gas, this study used validated grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation to investigate the adsorption characteristics of 11 different topological structures (straight-channel MFI/BEA, cage-channel LTA/FAU/CHA) and cation types (Ca2+, Na+, H+) of commercial zeolites for CO2 and alkanes (CH4, C2H6, C3H8) at 0%~90% RH. The results showed that the CO2 adsorption capacity of all zeolites decreased with increasing humidity, but straight-channel zeolites (ZSM5-300, BETA-25) had excellent moisture resistance, with only a 20.8% and 30.6% decrease in capacity at 90% RH, respectively. The performance of cage-channel zeolite drops sharply under high humidity. Topology structure and cation synergistically regulate separation efficiency, maintaining stable diffusion order in straight channels. Ca2+ enhances dry state capacity but is prone to hydrophilic failure. The adsorption heat of CO2 on straight-channel zeolite is 25–38 kJ/mol, resulting in lower regeneration energy consumption. ZSM5-300 is preferred for PSA (CH4/CO2 kinetic separation coefficient of 809.52 at 90% RH), and NaFAU is preferred for TSA (CO2 adsorption capacity of 3.6 mmol/g and selectivity of 502.6 at 90% RH). This study clarifies the core structure-activity relationship and provides key theoretical support for the decarbonization of oil-associated gas.