A process for treating a carrier, or a precursor thereof, to at least partly remove impurities comprising contacting the carrier, or the precursor thereof, with a treatment solution comprising a salt; a process for preparing a catalyst;the catalyst; a process for preparing an olefin oxide by reacting an olefin with oxygen in the presence of the catalyst; and a process for preparing a 1,2-diol, a 1,2-diol ether or an alkanolamine.