A catalyst is generally a substance that increases the rate of a reaction without altering the overall standard Gibbs free energy change. It can also be described as a substance that increases the rate of a chemical reaction without changing the chemical equilibrium, and whose mass and chemical properties remain unchanged before and after the reaction. Statistics show that catalysts are used in over 90% of industrial processes, such as chemical, petrochemical, biochemical, and environmental protection industries.
Catalysts are diverse. Based on their state, they can be classified as liquid catalysts and solid catalysts; based on the phase of the reaction system, they can be classified as homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts include acid, base, soluble transition metal compound, and peroxide catalysts. Catalysts play an extremely important role in modern chemical industry. For example, iron catalysts are used in the production of ammonia, vanadium catalysts are used in the production of sulfuric acid, and different catalysts are used in the polymerization of ethylene and the production of rubber from butadiene, three major synthetic materials.
