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

Abstract

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.

1. Introduction

Oil-associated gas produced during the oil field extraction process is rich in hydrocarbon components such as CH₄, C₂H₆, and C₃H₈, which can be recycled and utilized, and is an important commercial energy source. However, high concentrations of CO₂ not only significantly reduce the calorific value of the gas but also cause corrosion of the transportation pipeline, severely restricting the direct utilization of associated gas [1,2,3]. Therefore, achieving efficient separation of CO₂ and alkanes has become a key prerequisite for the resource recovery of associated gas in oil fields, and is also a core technical problem that urgently needs to be solved in the industrial field.

Among numerous CO₂ separation technologies, adsorption separation technology has become the preferred alternative to traditional technologies such as distillation and absorption due to its advantages of small equipment footprint, low operating costs, and short start-up process [4,5]. As the core functional material of this technology, zeolite is considered one of the ideal adsorbents for oil-associated gas decarbonization, thanks to its regular crystal structure, excellent thermal stability, and adjustable pore and surface properties [6,7]. Previous studies have shown that the topology, silicon–aluminum ratio, and compensatory cation type of zeolites significantly regulate their adsorption selectivity for CO₂ and alkanes by affecting the number of adsorption sites, pore size, and surface interactions [8,9,10]. The wide humidity characteristics of oil field-produced gas (relative humidity 20%~90%) can lead to competition between water molecules and CO₂ for adsorption active sites, further exacerbating the degradation of adsorbent performance and posing severe challenges to separation efficiency [11,12].

Although there have been many studies on CO₂ adsorption by zeolites, significant shortcomings remain. Most focus on dry or single humidity conditions [13,14], lacking systematic exploration of adsorption thermodynamics and kinetics over a wide humidity range; the micro-mechanism of synergistic regulation by topology, cation type, and humidity is unclear, and there is a lack of in-depth analyses of gas diffusion under a wide humidity range [15,16]. Traditional experimental methods have long cycles and high costs, making it hard to screen adsorbents for pressure swing adsorption (PSA) or temperature swing adsorption (TSA) [17,18]. Molecular simulation can obtain key microscopic parameters via Monte Carlo (GCMC) and molecular dynamics (MD) methods, reveal adsorption and separation mechanisms, and provide scientific guidance for adsorbent screening [19,20,21,22,23,24,25,26,27,28,29].

This study used GCMC and MD simulation techniques to systematically explore the adsorption and diffusion characteristics of 11 commercial zeolites with different topological structures (straight-channel MFI, BEA; cage-channel LTA, FAU, CHA) and cation types (Ca²⁺, Na⁺, H⁺) for CO₂ and typical alkanes (CH₄, C₂H₆, C₃H₈) over a wide humidity range of 0%~90% RH. By analyzing key parameters such as the adsorption capacity and separation coefficient, the influence mechanism of topology, cation type, and humidity was clarified, and a multidimensional screening system of “thermodynamics–kinetics–moisture resistance” was established to determine the optimal adsorbents for PSA/TSA industrial processes, providing key theoretical support for the precise screening of decarbonization adsorbents for oil-associated gas.

2. Computational Methods and Details

2.1. Models

The molecular sieve configurations (BETA-25, ZSM5-300, HLTA, HFAU, HCHA, NaLTA, NaFAU, NaCHA, CaLTA, CaFAU, CaCHA) used in this study are from the database of zeolite structures [30]. For example, BETA-25 molecular sieve is a three-dimensional structure of a twelve-membered ring cross-pore system, which has twelve-membered ring straight pores (0.76 nm × 0.64 nm) in the [100] and [010] directions and twisted twelve-membered ring pores (0.55 nm × 0.55 nm) in the [001] direction. The 1 × 1 × 1 unit cell is used in the simulation, with parameters of a = b = 1.2661 nm, c = 2.6416 nm, α = β = γ = 90° The programming method following the Löwenstein avoidance rule is used to randomly replace Si atoms with Al atoms in the original zeolite. The molecular formula of the molecular sieve after equilibrium is BETA-25 (H₅Al₅Si₅₉O₁₂₈). The adsorbates were optimized by the DMol³ quantum mechanics module.

2.2. Adsorbate–Adsorbent Interaction Potential

In this study, the geometric structure optimization after modeling was carried out under the Universal force field, and the COMPASSII force field was selected for thermodynamic and dynamic calculations. The interactive parameters, ε and σ, can be obtained according to the mixed calculation rule of Lorentz–Botherlot, as follows:

$$\left\{\begin{array}{c}{\sigma }_{ij}=({\sigma }_i+{\sigma }_j)/2\\ {\epsilon }_{ij}=\sqrt{{\epsilon }_i{\epsilon }_j}\end{array}\right.$$

(1)

where σ_i and σ_j are the collision diameters (Å); ε_i and ε_j are the potential energy well depths (kcal/mol); and subscripts i and j refer to the types of atoms or molecules.

2.3. Molecular Simulation Methods

2.3.1. GCMC Simulations

The GCMC method is used to study the adsorption behavior of different component molecules on the molecular sieve structure model. All GCMC simulations are conducted using the Sorption and Forcite modules in Materials Studio software (2025). The parameter settings are shown in Table 1. Set the temperature to 303 K, maintain the total pressure of 100 kPa, and set the partial pressures of water to 1.27 kPa (RH = 30%), 2.55 kPa (RH = 60%), and 3.83 kPa (RH = 90%).

Table 1. Simulation parameters.

Setting	Parameter
Task	Fixed pressure/Adsorption isotherm
Forcefield	CompassII
Equilibration steps	1 × 106
Production steps	1 × 107
Charges	Use current
Electrostatic	Ewald&Group
Van der Waals	Atom based

2.3.2. MD Simulations

The molecular dynamics (MD) method is used to simulate the diffusion process of gas in zeolite in order to obtain the diffusion coefficient of the gas in the zeolite. Before MD simulations, it is necessary to load a gas molecule into the zeolite and obtain a low-energy configuration, and then optimize its structure. In MD simulations, the NVT ensemble is used, with an initial velocity set to random. The Nose hot bath method is used, with a time step of 1 fs and a total simulation time set to 200 ps, with the first 50 ps used for the equilibrium structure and the last 150 ps used for the result calculations. The self-diffusion coefficient of a gas can be calculated from the Einstein equation:

$$D_S=\underset{t\to \infty }{\lim }{\displaystyle \frac{1}{6t}}⟨{\left|{}_r{}^{\to }\left(t\right)-{}_r{}^{\to }\left(0\right)\right|}^2⟩$$

(2)

where $⟨{\left|{}_r{}^{\to }\left(t\right)-{}_r{}^{\to }\left(0\right)\right|}^2⟩$ is the mean squared displacement (MSD) of gas molecules. When the slope of the log MSD–log t curves is 1, the simulation results converge. At this point, 1/6 of the slope of the MSD-t curve is the self-diffusion coefficient. When the gas concentration is quite low, the thermodynamic correction diffusion coefficient is approximately equal to the self-diffusion coefficient obtained from the simulation. The change in humidity is realized by the number of water molecules in the zeolite. After deriving the zeolite structure model with different numbers of water molecules, the subsequent adsorption and diffusion of gas molecules on the zeolite under different humidities conditions are carried out.

3. Results

3.1. Validation of Model and Simulation

The adsorption isotherms of pure components were computed and compared to experimental data to validate the parameters of the force field in previous work [31,32]. The calculated adsorption isotherms of CO₂ and H₂O were compared with the literature values [33]. The simulation results show good agreement with the experimental data. The simulation method, zeolite models, and force field parameters were well verified by the comparison results.

3.2. Adsorption Isotherms of Mixture

Figure 1 shows the adsorption isotherms of alkanes and CO₂ in 11 zeolites under different humidities. The q_CO2 and the separation coefficient of CO₂/alkanes (α_the^CO2/CnH2n+2 = q_CO2/(q_CH4+ q_C2H6+ q_C3H8)) at 100 kPa are shown in Table 2. The q_{CO2,100 kPa} of 11 zeolite decreased with the increase in humidity, due to the competition between water molecules and CO₂ for adsorption active sites (CO₂ is a polar molecule, and the hydrogen bond/dipole interaction between water molecules and zeolite preempts the adsorption sites). Cation priority is Ca²⁺ > Na⁺ > H⁺ (under dry conditions); the strong electrostatic effect of Ca²⁺ enhances the adsorption of CO₂. The adsorption capacity of cage-channel structure (LTA, FAU, CHA) is generally higher than that of straight-channel (ZSM5-300, BETA-25), because the pore volume of cage-channel structure is larger; But ZSM5-300 and BETA-25 had the smallest decrease in q_CO2 (for example, in ZSM5-300, q_{CO2, 0% RH} = 0.24 mmol/g, q_{CO2, 90% RH} = 0.19 mmol/g, decrease of 20.8%), reflecting the advantage of moisture resistance, due to the size limit of the straight-channel structure reduced the occupied sites of water molecule.

Figure 1. Adsorption isotherms at different humidities.

Table 2. Separation performance of alkanes/CO₂ in 11 zeolites at different humidities.

Zeolite	RH = 0%		RH = 20%		RH = 60%		RH = 90%
	qCO2 (mmol/g)	αtheCO2/CnH2n+2	qCO2 (mmol/g)	αthe CO2/CnH2n+2	qCO2 (mmol/g)	αthe CO2/CnH2n+2	qCO2 (mmol/g)	αthe CO2/CnH2n+2
BETA-25	1.44	1.06	1.24	1.5	1.32	1.59	0.64	2.70
ZSM5-300	0.24	7.69	0.19	10	0.21	9.09	0.19	10.00
HLTA	8.2	8.0	4.93	4	4.66	5	2.0	3.14
NaLTA	6.5	20.2	4.06	14	4.43	7	1.5	15.4
CaLTA	8.6	420.9	1.75	4933	1.72	71	1.9	395.0
HFAU	6.5	82.8	2.56	55	2.00	52	3.3	64.6
NaFAU	5.9	137.4	3.31	120	1.43	201	3.6	502.6
CaFAU	7.3	1929.7	2.21	115	1.73	1243	1.6	581.4
HCHA	4.4	29,181	3.65	838	3.34	5324	3.1	1059
NaCHA	4.1	4576.0	3.31	1601	3.19	71	2.7	19.0
CaCHA	5.0	7530.9	2.61	3448	1.96	3598	2.0	3598.9

From the calculation results of adsorption heat (Figure S1), the adsorption heat of CO₂ is higher than that of alkanes in all zeolites and decreases with humidity; the CO₂ adsorption heat of straight-channel zeolites is 25–38 kJ/mol, resulting in lower regeneration energy consumption. Humidity has a two-way effect on separation coefficients: 9 zeolites (e.g., HLTA, HCHA) show decreased coefficients with humidity, while NaFAU and ZSM5-300 increase to 502.6 and 10.00 at 90% RH, and the selectivity of cage-channel zeolites declines sharply under high humidity.

It can also be seen from Table 2 that the selectivity for long-chain alkanes is stronger. In all zeolites, α_the^CO2/C3H8 and α_the^CO2/C2H6 are higher than α_the^CO2/CH4 because the adsorption affinity of long-chain alkanes is weaker than that of CH₄. CH₄ is the main combustible component in the produced gas of the oil field, and the α_the^CO2/CH4 of ZSM5-300 and BETA-25 is still ≥10 under high humidity, meeting the industrial demand of preferentially capturing CO₂ and retaining CH₄. CHA zeolite has the best selectivity (drying conditions): α_the^CO2/CnH2n+2 of HCHA, NaCHA, and CaCHA are all >1000 (0% RH), and the confinement effect of cage-channel structure enhanced the selectivity of CO₂, but the moisture resistance is poor (in NaCHA at 90% RH, α_the^CO2/CnH2n+2 = 19.0), decreasing by 99.6%. The direct channel zeolite has the best moisture resistance selectivity: α_the^CO2/CnH2n+2 of ZSM5-300 and BETA-25 at 90% RH are 10.00 and 2.70, respectively. Although the value is lower than that of the CHA type, it has strong stability. H⁺ zeolites have the best selective moisture resistance, and Ca²⁺ zeolites are only suitable in a dry environment.

3.3. Self-Diffusion from Mixture

Based on the thermodynamic study, the diffusion of mixed components in zeolite in a wet atmosphere was calculated. The root mean square displacement versus time curves of high concentration alkanes and CO₂ on 11 molecular sieves under different humidities are shown in Figure 2 (Figure S2). The diffusion coefficient (Ds) results calculated by the Einstein equation and kinetic separation coefficient α_kin (Ds_CnH2n+2/Ds_CO2) are shown in Table 3.

Figure 2. Diffusion curves of 11 zeolites at different humidities.

Table 3. Diffusion and kinetic separation coefficient of 11 zeolites at different humidities.

Zeolite	RH	Ds (cm2/s)				α kinCnH2n+2/CO2
		CH4	C2H6	C3H8	CO2	CH4/CO2	C2H6/CO2	C3H8/CO2
BETA-25	0%	3.63 × 10−6	1.14 × 10−6	1.13 × 10−6	1.08 × 10−7	33.61	10.56	10.46
	20%	4.46 × 10−6	2.94 × 10−6	1.16 × 10−6	2.75 × 10−7	16.22	10.69	4.22
	60%	3.22 × 10−6	3.79 × 10−6	9.80 × 10−6	1.32 × 10−7	24.39	28.71	74.24
	90%	7.37 × 10−6	10.02 × 10−6	6.66 × 10−6	3.86 × 10−7	19.09	25.96	17.26
ZSM5-300	0%	2.22 × 10−6	3.78 × 10−7	1.87 × 10−6	3.84 × 10−7	5.78	0.98	4.87
	20%	16.9 × 10−6	13.32 × 10−6	2.06 × 10−6	8.53 × 10−10	19,882	15,615	2415
	60%	8.83 × 10−6	5.42 × 10−6	5.68 × 10−7	9.21 × 10−9	958.7	588.4	61.67
	90%	2.72 × 10−6	5.84 × 10−6	1.23 × 10−6	3.36 × 10−9	809.5	1738	366.1
CaCHA	0%	7.50 × 10−6	8.95 × 10−7	9.62 × 10−8	6.54 × 10−7	11.47	1.37	0.15
	20%	8.75 × 10−9	2.25 × 10−7	5.00 × 10−7	7.51 × 10−9	1.17	30.09	66.58
	60%	2.19 × 10−9	5.07 × 10−8	2.00 × 10−6	8.41 × 10−7	0.003	0.06	2.38
	90%	6.47 × 10−9	5.49 × 10−7	7.73 × 10−7	2.98 × 10−7	0.022	1.84	2.59
CaFAU	0%	5.15 × 10−5	9.80 × 10−8	4.15 × 10−6	3.34 × 10−6	15.42	0.03	1.24
	20%	9.71 × 10−9	5.37 × 10−8	6.15 × 10−8	3.07 × 10−7	0.03	0.18	0.20
	60%	2.40 × 10−4	3.81 × 10−4	1.03 × 10−4	2.67 × 10−6	90.04	142.7	38.58
	90%	8.17 × 10−6	1.82 × 10−8	2.33 × 10−8	1.28 × 10−5	0.64	0.001	0.002
CaLTA	0%	4.70 × 10−5	4.52 × 10−7	8.28 × 10−8	7.51 × 10−7	62.58	0.60	0.11
	20%	1.25 × 10−7	7.66 × 10−7	1.04 × 10−7	2.92 × 10−7	0.43	2.62	0.36
	60%	5.28 × 10−7	3.80 × 10−7	3.02 × 10−7	1.64 × 10−7	3.22	2.32	1.84
	90%	1.74 × 10−7	1.37 × 10−7	2.77 × 10−8	1.50 × 10−8	11.60	9.13	1.85
HCHA	0%	8.47 × 10−8	2.10 × 10−8	1.12 × 10−7	3.34 × 10−6	0.025	0.006	0.034
	20%	2.53 × 10−7	1.47 × 10−8	1.42 × 10−7	3.92 × 10−8	6.45	0.38	3.62
	60%	1.27 × 10−8	1.44 × 10−7	4.45 × 10−8	1.58 × 10−9	8.04	91.14	28.16
	90%	3.32 × 10−8	1.22 × 10−7	4.14 × 10−6	2.78 × 10−7	0.12	0.44	14.89
HFAU	0%	2.65 × 10−4	7.12 × 10−5	2.04 × 10−4	4.43 × 10−5	5.98	1.61	4.60
	20%	8.76 × 10−6	7.75 × 10−8	4.67 × 10−8	3.28 × 10−6	2.67	0.024	0.014
	60%	1.33 × 10−4	7.08 × 10−8	1.12 × 10−7	2.32 × 10−5	5.73	0.003	0.004
	90%	2.27 × 10−6	7.42 × 10−8	2.93 × 10−8	6.91 × 10−6	0.33	0.011	0.004
HLTA	0%	9.13 × 10−8	--	2.58 × 10−8	2.51 × 10−6	0.036	--	0.010
	20%	4.35 × 10−6	7.38 × 10−6	5.70 × 10−6	6.72 × 10−6	0.65	1.10	0.85
	60%	8.85 × 10−8	8.63 × 10−8	2.34 × 10−7	1.61 × 10−7	0.55	0.54	1.45
	90%	1.44 × 10−6	3.97 × 10−8	3.75 × 10−7	5.06 × 10−6	0.28	0.008	0.074
NaCHA	0%	7.25 × 10−6	1.45 × 10−8	--	7.11 × 10−7	10.20	0.002	--
	20%	1.11 × 10−8	2.42 × 10−7	1.60 × 10−7	1.38 × 10−7	0.008	1.75	1.16
	60%	2.46 × 10−9	1.06 × 10−7	4.92 × 10−7	3.47 × 10−7	0.001	0.31	1.42
	90%	6.28 × 10−9	1.38 × 10−7	1.04 × 10−6	3.60 × 10−7	0.017	0.38	2.89
NaFAU	0%	2.39 × 10−4	3.80 × 10−5	3.20 × 10−5	5.44 × 10−7	439.3	70.04	58.82
	20%	1.54 × 10−7	8.47 × 10−9	--	7.63 × 10−6	0.020	0.0011	--
	60%	1.46 × 10−7	3.11 × 10−9	--	4.61 × 10−6	0.032	0.0006	--
	90%	3.37 × 10−8	4.85 × 10−8	3.10 × 10−8	3.77 × 10−6	0.009	0.013	0.008
NaLTA	0%	1.86 × 10−7	1.87 × 10−7	8.77 × 10−8	3.01 × 10−6	0.062	0.062	0.029
	20%	4.35 × 10−8	3.62 × 10−6	3.20 × 10−8	1.10 × 10−7	0.395	32.91	0.29
	60%	2.09 × 10−7	1.45 × 10−7	1.70 × 10−7	1.37 × 10−7	1.525	1.058	1.24
	90%	--	1.43 × 10−7	9.14 × 10−10	--	--	1.239	0.008

The symbol “--“ indicates that the value has fallen below 10⁻¹⁰.

The stability of most zeolites is poor, except ZSM5-300 and BETA-25. The kinetic separation coefficients of the other 9 zeolites fluctuate significantly with the increase in humidity. For example, the separation coefficient of CaCHA at 0% RH is 11.47, and it decreases to 0.0217 at 90% RH, with a decrease of 99.8%. The kinetic separation coefficient was 62.58% at 0% RH and 11.60% at 90% RH, a decrease of 81.5%.

The straight-channel structure has significant advantages: the straight-channel topology of ZSM5-300 (MFI type) and BETA-25 (BEA type) can maintain the size screening effect of gas diffusion (CH₄ > C₂H₆ > C₃H₈ > CO₂), which is not damaged even under high humidity. However, cage-channel structures (LTA, FAU, CHA) are prone to being occupied by water molecules, resulting in disordered diffusion order (for example, the diffusion coefficient of HLTA at 90% RH is higher than that of C₃H₈).

The type of cation determines moisture resistance. Ca-zeolite: The adsorption capacity is high under dry conditions (0% RH), but the kinetic separation performance is very sensitive to humidity. Na-zeolite: NaFAU is the only zeolite whose separation coefficient increases with the increase in humidity, reflecting the weak interaction between Na⁺ and water molecules. H-zeolite: The separation coefficient of HLTA, HFAU, and other dry conditions is medium, and generally decreases under high humidity.

From the perspective of industrial application requirements, ZSM5-300 is preferred. The dynamic separation performance is better than that of other zeolites under medium and high humidity (20–90% RH). At 90% RH, α_kin^CH4/CO2 (809.52) and α_kin^C2H6/CO2 (1738.09) are the highest values, and are suitable for gas production scenarios in wet oil fields. In addition, BETA-25 zeolite is used as an alternative. The performance is balanced in the full humidity range, without extreme fluctuations. α_kin^CH4/CO2 under dry (0% RH) and high humidity (90% RH) conditions is 33.61 and 19.09, respectively, which is suitable for the working conditions with large humidity fluctuations. Ca-zeolite should be avoided.

3.4. Evaluation of Zeolite in Industrial Application

As the core functional material of pressure swing adsorption (PSA) and temperature swing adsorption (TSA), the performance of adsorbent directly determines the treatment efficiency, energy consumption cost, and operation stability of industrial plants. Under the complex working conditions of high humidity (20–90% RH) and multi-component (CO₂+CH₄+C₂H₆+C₃H₈) of oil field-produced gas, combined with the industrial design objectives and operating characteristics of PSA/TSA, 11 commercial zeolite adsorbents were systematically screened and sorted based on the adsorption thermodynamics (capacity, selectivity, adsorption heat), kinetics (diffusion coefficient, kinetic separation coefficient) and moisture resistance data obtained from the previous molecular simulation, and the industrial adaptation boundary and application priority of each adsorbent were determined.

The PSA process takes a “rapid adsorption–desorption cycle” as its core advantage, with core requirements for adsorbents including dynamic performance, cycle stability, and low regeneration energy consumption. Figure 3a shows that adsorbents with moisture resistance (defined as the ratio of carbon dioxide adsorption capacity under high humidity and dry conditions, q_{CO2, 90%RH}/q_{CO2, 0%RH}) > 0.4 and kinetic separation coefficient > 0.32 (lgαkin = −0.5) are ZSM5-300 and BETA-25. ZSM5-300 becomes the preferred PSA adsorbent due to excellent kinetic separation performance and high moisture resistance, while BETA-25 is an alternative with balanced performance; Na⁺ and H⁺ zeolites have insufficient kinetics, and Ca²⁺ zeolites have poor moisture resistance, making them unsuitable for PSA processes.

Figure 3. Comprehensive comparison of multidimensional performance ((a) for kinetics, (b) for thermodynamics).

The core of the TSA process is “high-capacity adsorption and mild regeneration”, with requirements for adsorbents focusing on adsorption capacity, thermal stability, and regeneration economy. Figure 3b shows that adsorbents with moisture resistance >0.4 and thermodynamic equilibrium separation coefficient > 10 (lgαthe = 1) are NaCHA, NaFAU, HCHA, and HFAU. NaFAU becomes the preferred TSA adsorbent due to its CO₂ adsorption capacity of 3.6 mmol/g (the highest among 11 zeolites) and selectivity of 502.6 at 90% RH, with HFAU, NaCHA, and HCHA as alternatives.

4. Conclusions

The CO₂ adsorption capacity of all zeolites decreases with humidity, but straight-channel zeolites (ZSM5-300, BETA-25) have excellent moisture resistance, with a capacity decrease of only 20.8% and 30.6% at 90% RH. The performance of cage-channel zeolite drops sharply under high humidity. Topology structure and cation synergistically regulate the separation efficiency; the straight-channel structure maintains stable diffusion order, Ca²⁺ enhances the adsorption capacity of dry CO₂, but hydrophilicity leads to a decrease in separation efficiency, H-zeolite maintains balanced moisture resistance selectivity. The adsorption heat of CO₂ on straight-channel zeolite is 25–38 kJ/mol, resulting in lower regeneration energy consumption. The selection criteria for adsorbents in industrial PSA/TSA processes have been clarified: based on the PSA process requirement, ZSM5-300 is the preferred adsorbent for the PSA process; BETA-25 can be used as an alternative due to its balanced performance; NaFAU is the optimal choice for the TSA process; and HFAU and NaCHA can be used as supplementary alternatives.