A process for producing ethylene glycol and/or ethylene carbonate, said process comprising contacting at least a portion of a recycle gas stream comprising an alkyl iodide impurity with a guard bed system positioned upstream of an ethylene oxide reactor to produce a treated recycle gas stream, wherein said guard bed system comprises a guard bed material comprising silver on alumina; contacting an epoxidation feed stream comprising an ethylene feed stream, oxygen, chloride moderator, and at least a portion of the treated recycle gas stream with an epoxidation catalyst in the ethylene oxide reactor to produce an epoxidation reaction product comprising ethylene oxide; and contacting at least a portion of the epoxidation reaction product comprising ethylene oxide with a liquid absorbent in the presence of an iodide-containing catalyst in an absorber to produce a product stream comprising ethylene carbonate and/or ethylene glycol and the recycle gas stream comprising the alkyl iodide impurity, wherein the epoxidation feed stream comprising ethylene feed stream, oxygen, moderator compound, and treated recycle gas stream contacted with the epoxidation catalyst in the ethylene oxide reactor comprises 1500 to 8000 ppmv of ethane, and wherein a vinyl chloride moderator is added to the epoxidation feed stream, wherein the concentration of vinyl chloride moderator added to the epoxidation feed stream is controlled such that the I-factor representing the relative quantity of chloride moderator species present in the epoxidation feed stream, defined as I factor = vinyl chloride + ethyl chloride + methyl chloride / 3 / ethylene + 70 * ethane is in the range of 0.02-0.4. contacting at least a portion of a recycle gas stream comprising an alkyl iodide impurity with a guard bed system positioned upstream of an ethylene oxide reactor to produce a treated recycle gas stream, wherein said guard bed system comprises a guard bed material comprising silver on alumina; contacting an epoxidation feed stream comprising an ethylene feed stream, oxygen, chloride moderator, and at least a portion of the treated recycle gas stream with an epoxidation catalyst in the ethylene oxide reactor to produce an epoxidation reaction product comprising ethylene oxide; and contacting at least a portion of the epoxidation reaction product comprising ethylene oxide with a liquid absorbent in the presence of an iodide-containing catalyst in an absorber to produce a product stream comprising ethylene carbonate and/or ethylene glycol and the recycle gas stream comprising the alkyl iodide impurity, wherein the epoxidation feed stream comprising ethylene feed stream, oxygen, moderator compound, and treated recycle gas stream contacted with the epoxidation catalyst in the ethylene oxide reactor comprises 1500 to 8000 ppmv of ethane, and wherein a vinyl chloride moderator is added to the epoxidation feed stream, wherein the concentration of vinyl chloride moderator added to the epoxidation feed stream is controlled such that the I-factor representing the relative quantity of chloride moderator species present in the epoxidation feed stream, defined as I factor = vinyl chloride + ethyl chloride + methyl chloride / 3 / ethylene + 70 * ethane is in the range of 0.02-0.4.