Processes for producing propylene glycol are disclosed. The processes may comprise subjecting a polyol to a hydrogenolysis reaction, thus producing propylene glycol and a product stream including an unreacted polyol and at least one unwanted compound. The process may include subjecting the product stream to a process that removes at least a portion of the at least one unwanted compound, thus producing a cleaned product stream, and subjecting the cleaned product stream to the hydrogenolysis reaction. Systems for implementing such processes are also described.