A membrane reactor that incorporated hollow fiber in combination with an established catalyst was used for the oxidative coupling of methane (OCM). A perovskite membrane of the composition BaCo x Fe y Zr z O3−δ (BCFZ, x + y + z = 1) allows a controlled oxygen feed into the reactor over its axial length. Using this novel hollow fiber membrane reactor with a 2 wt % Mn/5 wt % Na2WO4 on SiO2 catalyst as a packed bed around the fiber, oxygen separation from air and C2 formation could be established at 800 °C with long-term stability. The highest C2 selectivity of ∼75% was observed at a methane conversion of 6% with a C2H4:C2H6 ratio of 2:1. The highest C2H4:C2H6 ratio of 4:1 and maximum C2 yield of 17% was obtained at 50% C2 selectivity. It is known from the literature that such results can be obtained without a catalyst in a similar membrane reactor only at temperatures 150 °C higher.

Carbon membranes have great potential for highly selective and cost-efficient gas separation. Carbon is chemically stable and it is relative cheap. The controlled carbonization of a polymer coating on a porous ceramic support provides a 3D carbon material with molecular sieving permeation performance. The carbonization of the polymer blend gives turbostratic carbon domains of randomly stacked together sp hybridized carbon sheets as well as sp hybridized amorphous carbon. In the evaluation of the carbon molecular sieve membrane, hydrogen could be separated from propane with a selectivity of 10 000 with a hydrogen permeance of 5 m (STP)/(m hbar). Furthermore, by a post-synthesis oxidative treatment, the permeation fluxes are increased by widening the pores, and the molecular sieve carbon membrane is transformed from a molecular sieve carbon into a selective surface flow carbon membrane with adsorption controlled performance and becomes selective for carbon dioxide.

In three case studies, (i) 1-butene/i-butene separation on a ZSM-5 membrane, (ii) carbon dioxide/methane, and (iii) ethene/ethane separations on a zeolitic imidazolate framework 8 (ZIF-8) type metal organic framework (MOF) membrane, it is demonstrated that the membrane selectivity for the separation of a gas mixtures can be well described and even predicted by the interplay of mixture adsorption and mixture diffusion according to the simple relation membrane selectivity = adsorption selectivity × diffusion selectivity. The mixed gas adsorption and diffusion data which are necessary for the above calculation can be derived cost and time effective by sorption uptake/desorption studies on giant single crystals with IR microscopy (IRM) detection.

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