what are heterogeneous
A catalyst in the same phase (usually liquid or gas solution) as the reactants and products is called homogeneous catalyst. A catalyst that is in a separate phase from the reactants is said to be a heterogeneous, or contact, catalyst. Contact catalysts are materials with the capability of adsorbing molecules of gases or liquids onto their surfaces. An example of heterogeneous catalysis is the use of finely divided platinum to catalyze the reaction of carbon monoxide with oxygen to form carbon dioxide.