The epoxidation of allyl alcohol to glycidol by hydrogen peroxide over titanium silicate TS-1 ZSM-5 has been studied under conditions relevant for an industrial-scale process. In particular, the effects of different solvents, impurities and some side reactions known to occur due to those impurities have been examined. It was found that certain aldehydes (in particular, acrolein) are especially detrimental to glycidol yield. Conversely, some of the impurities added to the reaction mixture were found to promote the conversion of allyl alcohol. Possible mechanisms for this are discussed.