A chemical process involved in the production of industrial chemicals. Catalysis is relevant to many aspects of environmental science–for instance, the study of the catalytic converter in cars and the catalysis involved in the ozone hole. Substances that are catalysts change the rate of chemical reaction. Catalysts that increase reaction rates are called positive catalysts. Those that slow down chemical reactions are called negative catalysts. Catalytic reactions are generally preferred as they reduce the amount of waste generated.