Adsorption and separation of hydrocarbons by the metal organic framework MIL-101(Cr)

The aim of this work is to study the adsorption of several hydrocarbons by MIL-101(Cr) in order to find trends in adsorption behavior and relate those to the physicochemical properties of the sorbates. The separation of saturated, unsaturated and cyclic hydrocarbons was investigated on MIL-101(Cr) by means of gas chromatography equipped with a filled column of the MOF. MIL-101(Cr), proved to be very efficient to separate mixtures of saturated, unsaturated or aromatic hydrocarbons. The influence of hydrocarbons branching is evaluated towards their separation. We found that linear hydrocarbons are eluted firstly in the case of the n -hexane isomers series. We also demonstrated that xylenes are partially separated by MIL-101: metaxylene and paraxylene being eluted together, before orthoxylene. MIL-101 behaves therefore as a shape selective material with respect to the isomers of n -hexane, or xylenes. This separation could be predicted by the Henry’s constants which are calculated from the adsorption isotherms of single components by MIL-101(Cr). It is then demonstrated that these Henry’s constants establish a new tool for predicting the separation efficiency of any sorbent.