Oxidative coupling of methane using catalyst modified dense perovskite membrane reactors

A comparative study modifying an ionic oxygen conducting membrane reactor for the oxidative coupling of methane to higher hydrocarbons with 3 different catalytic surface modifications is presented. Dense Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCFO) membrane disks were wash-coated with a Pt/MgO model catalyst as well as with more efficient Sr/La2O3 and LaSr/CaO catalysts. The role of the catalyst is underlined by the fact that the LaSr/CaO shows that highest yield between 900 and 1000 °C while yields decline for the Sr/La2O3 catalyst at temperatures above 900 °C. The latter observation agrees well with observations on conventional catalytic reactors using hydrocarbon/oxygen co-feeding at lower temperature and seems to relate to the formation of highly reactive oxygen species formed at the La2O3 surface. Operating a LaSr/CaO modified membrane reactor at 950 °C with a CH4 concentration of 34%, a C2-hydrocarbon yield of more than 18% was achieved (at a selectivity of more than 65%). Given the interesting performance, it is obvious that future membrane reactors should employ efficient catalyst systems and development should focus on maximizing the exposure of catalytically modified membrane surfaces.