In this work, the adsorption parameters of n-butane vapor on an absorbent were tested following the fixed-bed method. According to the corresponding experiments, the maximum adsorption capacity and breakthrough time of activated carbon (AC) are 0.2674 g·g^–1 and 924 min, respectively. According to the two-energy-state model formula and the classical adsorption heat formula, the values of theoretical and actual adsorption heat of AC adsorbing n-butane are 5.48 and 5.56 kJ·mol^–1, respectively. The model for adsorption of n-butane by an AC fixed bed is based on the analytical solutions to the mass, momentum, and energy conservation equations. The model is built using porous media zone in ANSYS Fluent, the implementation of the model into ANSYS Fluent under user-defined functions (UDFs) is also described, the mass source term S_i and energy source term S_T are loaded into Fluent through UDF, and then the mass- and heat-transfer processes of AC in the absorption of n-butane are simulated. Furthermore, the predictions by ANSYS Fluent are compared with in situ experimental data, and the deviation rate of breakthrough time and temperature of six monitoring points is less than 5%. The results verify the accuracy and feasibility of computational fluid dynamics (CFD). Therefore, the model can be used to predict the engineering application of the adsorption of organic gases by various porous media.