Adsorption performance of a MIL-101(Cr)/graphite oxide composite for a series of n-alkanes

Abstract

The adsorption performance of the MIL-101@GO composite for a series of linear long chain alkanes (from n-pentane to n-octane) was investigated for the first time. The MIL-101@GO composite based on MIL-101(Cr) and graphite oxide (GO) was prepared, characterized and tested for adsorption and desorption of n-alkanes. Isotherms of a series of n-alkanes on MIL-101@GO were measured. Temperature-programmed desorption (TPD) experiments were conducted to estimate desorption activation energies of n-alkanes on MIL-101@GO. Results showed that the adsorption capacities of n-alkanes on MIL-101@GO increased with the hydrocarbon chain length at regions of low pressure, while the trend was reversed at regions of high pressure. The adsorption capacities of n-alkanes on MIL-101@GO were about 1.6–11 times higher than those of conventional activated carbons and the zeolites. The isotherms of n-alkanes could be fitted favorably by the Langmuir–Freundlich equation. The desorption activation energy increased linearly with the carbon number of the n-alkanes. Consecutive cycle experiments of adsorption–desorption showed the isotherms of n-octane in all five cycles were nearly overlapping, suggesting that MIL-101@GO had excellent reversibility of n-alkane adsorption.