Study on Adsorption and Desorption Performances of Trace C4–C6 Alkane Mixture on MIL-101(Cr) and WS-480

A deep purification treatment of trace volatile organic compounds (VOCs) in the tail gas emitted from the top of oil storage tanks was performed. Metal organic framework MIL-101(Cr) (hereinafter referred to as MIL-101) was used to remove trace C4–C6 alkane mixture in the tail gas. Compared with the commercial activated carbon, adsorption and desorption processes of trace C4–C6 alkane mixture as well as the adsorption thermodynamic property of n-hexane on MIL-101 were analyzed. Results demonstrate that the adsorption isosteric heat of n-hexane on MIL-101 is 48–52 kJ/mol, 9 kJ/mol lower than that on activated carbon. Trace C4–C6 alkanes on MIL-101 were desorbed by a nitrogen purge at 393 K, and the desorption efficiency of MIL-101 was up to 98.9%, which is 35% higher than that of activated carbon (∼64.3%). After 10 adsorption/desorption cycles, the desorption efficiency of MIL-101 exceeds 97%, indicating good cycle stability. The desorption process is affected by the spatial fit between the molecular configurations of alkanes and the three-dimensional tetrahedral cage of MIL-101 or by the one-dimensional slit pore of activated carbon. For alkanes with the same carbon, n-alkanes are preferentially desorbed on MIL-101, whereas isoalkanes are preferentially desorbed on activated carbon. Rich mesopores connected with the tetrahedral cages of MIL-101 are beneficial for desorption of trace C4–C6 alkanes. It provides basic data for the deep treatment of VOCs in the tail gas of oil storage tanks.