Adsorption and separation properties of n-pentane/isopentane on ZIF-8

•ZIF-8 shows a high potential for n-pentane/isopentane separation.•The equilibrium adsorption capacity and rate of n-pentane are higher than isopentane on ZIF-8.•ZIF-8 shows higher adsorption capacity and lower desorption temperature for n-pentane than 5A molecular sieve. Adsorption equilibrium and kinetic data is essential for the design of an adsorption process. In this work, the adsorption isotherms of n-pentane/isopentane on zeolitic imidazolate framework material (ZIF-8) were measured at 308, 343 and 373K over the pressure range from 0 to 9.7kPa by a gravimetric system. The equilibrium adsorption capacity at 303K and 9.7kPa is 0.2504gg−1 for n-pentane and 0.1439gg−1 for isopentane. Langmuir model was used to fit the adsorption isotherms. The adsorption kinetics of n-pentane/isopentane was studied at 308K in the pressure range from 0 to 69.9kPa. The data was well fitted with linear driving force model (LDF) model. The adsorption rate constant of n-pentane is from 0.0019 to 0.0326s−1, which is higher than that of isopentane, represented 0.0007–0.0036s−1. The adsorption selectivity of n-pentane/isopentane on ZIF-8 was contrast by the measurement of the binary breakthrough experiments at 343K, 363K and 393K in the partial pressure of 7kPa. When the adsorption temperature is 363K, the adsorption selectivity of n-pentane/isopentane on ZIF-8 reaches the maximum 55. Compared with 5A molecular sieve, the desorption temperature of n-pentane on ZIF-8 was analyzed by temperature-programmed-desorption (TPD) method. The peak temperature of n-pentane desorption on ZIF-8 is 361K. However are 392K and 443K on a 5A molecular sieve. Thus, ZIF-8 is more selective or preferential adsorption for n-pentane in comparison to isopentane molecules at low temperature.