The present invention provides a process for preparing a catalyst, wherein said process comprises:—(i) preparing a mixture of one or more aromatic alcohol monomers and/or non-aromatic monomers, solvent, polymerization catalyst, crosslinking agent, suspension stabilizing agent and one or more metal salts, under conditions sufficient to produce polymeric beads doped with one or more metals or salts thereof; (ii) carbonizing, activating and then reducing the polymeric beads produced in step (i) to produce metal nanoparticles-doped porous carbon beads; (iii) subjecting the metal nanoparticles-doped porous carbon beads produced in step (ii) to chemical vapour deposition in the presence of a carbon source to produce metal nanoparticles-doped porous carbon beads comprising carbon nanofibers; and (iv) doping the metal nanoparticles-doped porous carbon beads comprising carbon nanofibers produced in step (iii) with an oxidant; catalyst prepared by said process; and a process for treating waste water from an industrial process for producing propylene oxide, which process comprises subjecting the waste water to a catalytic wet oxidation treatment in the presence of said catalyst.