The gas-phase epoxidation of 2-butene (trans or cis) has been conducted in a flow-through reactor at a pressure of 0.5 bar and a temperature of 325 degrees C using a N-2/O-2 mixture as the carrier gas. The primary oxidizing agent in the feed gas is ozone. Selectivity to epoxide (trans- and cis-epoxide in total) or about 90% is observed. Investigations using mixtures of trans-2-butene with 1-butene or n-butane revealed a clearly preferred reaction of trans-2-butene. Kinetic analysis of the overall process yielded ratios for the corresponding rate coefficients of k(trans-2-butene)/k(1-butene) = 5.4-7.2 and k(trans-2-butene)/k(n-butane) similar to 67. A few experiments showed a similar behavior for cis-2-butene. Using raffinate 2 (1-butene, 2-butene, n-butane, and iso-butane) as the feedstock for epoxidation, a selective production of 2-butene oxide (trans/cis mixture) is feasible. Additions of methane (1.7-12.5 vol %), H2O vapor (1.7-4.2 vol %), or CO2 (1.7-25 vol %) in the carrier gas do not influence the epoxidation reaction.