Bi1.5Y0.3Sm0.2O3- (BYS), a ceramic material showing great activity and selectivity to oxidative coupling of methane (OCM), has been fabricated into catalyst rings (i.e., capillary tubes) with a plurality of self-organized radial microchannels. The unique microchannels inside such BYS catalyst rings allow easier access of reactants, as well as increased the surface area, which potentially contributes to higher reaction efficiencies due to improved mass transfer. The micro-structured BYS catalyst rings were investigated systematically via two types of reactors; (1) randomly packed fixed bed reactor and (2) monolithic-like structured reactor. These two reactor designs have different flow patterns of reactants, that is, non-ideal and ideal flows, which can significantly affect the final OCM performance. A remarkable improvement in C2+ yield (YC2+>20%) was obtained in the monolith-like structured reactor, in contrast to randomly packed powder and micro-structured rings (YC2+<15%), which proves the advantages of using a micro-structured catalyst with an ideal flow in the feed for OCM. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 3451-3458, 2015