x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the αp process that describes a sequence of (α,p) reactions triggered by the 18Ne(α,p)21Na breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus 22Mg by measuring the 24Mg(p,t)22Mg reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of α-unbound states was identified and precise excitation energies were determined. Based on shell model and α-cluster model calculations we predict the level parameters for determining the stellar reaction rate of 18Ne(α,p)21Na for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.