The U-shaped alkaline-earth metal-free CO2-stable oxide hollow-fiber membranes based on (Pr0.9La0.1)(2)(Ni0.74Cu0.21Ga0.05)O4+ (PLNCG) are prepared by a phase-inversion spinning process and applied successfully in the partial oxidation of methane (POM) to syngas. The effects of temperature, CH4 concentration and flow rate of the feed air on CH4 conversion, CO selectivity, H-2/CO ratio, and oxygen permeation flux through the PLNCG hollow-fiber membrane are investigated in detail. The oxygen permeation flux arrives at approximately 10.5 mL/min cm(2) and the CO selectivity is higher than 99.5% with a CH4 conversion of 97.0% and a H-2/CO ratio of 1.8 during 140 h steady operation. The spent hollow-fiber membrane still maintains a dense microstructure and the Ruddlesden-Popper K2NiF4-type structure, which indicates that the U-shaped alkaline-earth metal-free CO2-tolerant PLNCG hollow-fiber membrane reactor can be steadily operated for POM to syngas with good performance. (c) 2014 American Institute of Chemical Engineers AIChE J, 60: 3587-3595, 2014