The use of a sieve plate electrochemical reactor for the epoxidation of ethylene using indirect oxidation via electrogenerated bromine is described. Bromine is generated from the anodic oxidation of aqueous bromide solutions at graphite bipolar electrodes. The cathode reaction, hydrogen evolution, supplies the hydroxide ions required for the overall reaction processes. The emphasis is on the scale-up performance of a multi-stage sieve plate reactor (of cells in 4 stages) used to increase the degree of conversion of ethylene in the gas phase at lower gas recycle rates.