An ethylene oxide (EO) production process for the epoxidation of ethylene comprising: contacting an inlet feed gas with a catalyst having a fluoride-mineralized alpha-alumina carrier, silver, a rhenium promoter, and one or more alkali metal promoters. At a cumulative EO production cumEO.sub.1 of at least 0.2 kton EO/m.sup.3 catalyst, the process is operating at a reaction temperature T.sub.1 and with the inlet feed gas having an optimum overall catalyst chloriding effectiveness value Cl.sub.eff.sub.1 to produce EO with an EO production parameter value EO.sub.1; and the process is subsequently operated such that at a cumulative EO production cumEO.sub.X, cumEO.sub.X is at least 0.6 kton EO/m.sup.3 catalyst greater than cumEO.sub.1, the reaction temperature has an increased value T.sub.X to maintain EO production parameter EO.sub.1 whilst the optimum overall catalyst chloriding effectiveness value of the inlet feed gas Cl.sub.eff.sub.X is controlled such that the ratio of Cl.sub.eff.sub.X/Cl.sub.eff.sub.1 is from 0.8 to 1.2.

An ethylene oxide (EO) production process for the epoxidation of ethylene comprising: contacting an inlet feed gas with a catalyst having a fluoride-mineralized alpha-alumina carrier, silver, a rhenium promoter, and one or more alkali metal promoters. At a cumulative EO production cumEO.sub.1 of at least 0.2 kton EO/m.sup.3 catalyst, the process is operating at a reaction temperature T.sub.1 and with the inlet feed gas having an optimum overall catalyst chloriding effectiveness value Cl.sub.eff.sub.1 to produce EO with an EO production parameter value EO.sub.1; and the process is subsequently operated such that at a cumulative EO production cumEO.sub.X, cumEO.sub.X is at least 0.6 kton EO/m.sup.3 catalyst greater than cumEO.sub.1, the reaction temperature has an increased value T.sub.X to maintain EO production parameter EO.sub.1 whilst the optimum overall catalyst chloriding effectiveness value of the inlet feed gas Cl.sub.eff.sub.X is controlled such that the ratio of Cl.sub.eff.sub.X/Cl.sub.eff.sub.1 is from 0.8 to 1.2.