For catalyst It is understood a substance or element, both simple and compound, that plays an accelerating role in a given chemical reaction, shortening the times in which it occurs but without altering the final product at all and without losing its own mass in the process (something that it does occur in reagents). For example: enzymes, UV light, zinc, cobalt.
This process of acceleration of a chemical reaction is called “catalysis”. And the elements or substances that inhibit catalysis are known as inhibitors. Many chemical reactions need a suitable catalyst depending on whether you want to increase or decrease the rate at which they occur. In this sense, catalysis can be positive (the speed of the reaction increases) or negative (the speed of the reaction decreases).
The research in catalysis and production of catalytic agents is a prolific field of the chemical and biological industry, since they allow to accelerate reactions simply with the opportune addition of the suitable catalyst.
Examples of catalyst (and its function)
- Enzymes. They are substances biologically and naturally secreted by the body of living beings. Enzymes play a very important catalytic role, since they accelerate vital chemical processes that, if they occurred on their own, would require temperatures that are often incompatible with life. Pepsin and trypsin, for example, are involved in the breakdown of meats, speeding up digestion that would otherwise take much more time and effort.
- UV light. Ultraviolet light, together with a catalyst, enables photocatalysis: the acceleration of a chemical reaction by the work of a catalyst activated by the light energy of ultraviolet. Ozone and transition metal oxides are common photocatalysts.
- Palladium catalysts. Built into car systems that use unleaded gasoline, these devices contain palladium or platinum in small particles in a container that clings to car exhausts. These metals act as catalysts in the process of attenuating carbon monoxide and other toxic gases from combustion, and allow them to be reduced to water vapor or other less dangerous substances in record time.
- Aluminum chloride. This catalyst is used in the petrochemical industry to obtain synthetic resins or lubricating substances, without altering the delicate nature of the hydrocarbons in question, since it has acidic and basic properties at the same time (it is amphoteric).
- Fluorine derivatives. They accelerate the decomposition of ozone (O3 → O + O2), which is normally a fairly slow reaction. This is the problem of aerosols and refrigerants that release CFCs into the atmosphere: they dilute the ozone layer.
- Acidic substances. The protons released by most acidic substances can play the role of catalysts in certain chemical reactions, such as hydrolysis (breakdown of esters to form carboxylic acids and alcohols) of esters (organic petroleum derivatives).
- Zinc. It is a common catalyst in the constitution of cycloalkanes (saturated hydrocarbons) used in perfumery, the oil industry and others.
- Manganese dioxide (MnOtwo). This compound is a frequent catalyst to accelerate the decomposition of hydrogen peroxide or hydrogen peroxide (2H2O2 → 2H2O + O2).
- Iron (III). This metal is used as a catalyst in the Haber-Bosch process to obtain ammonia from hydrogen and nitrogen.
- Vanadium pentoxide (VtwoOR5). It is a highly toxic compound that reversibly loses oxygen when heated. That is why it is used as a catalyst in obtaining sulfuric acid from sulfur dioxide (SO2).
- Titanium. Mixed with aluminum, it is used in the Ziegler-Natta polymerization process to accelerate the production of high-density polyethylene (HDPE), used to manufacture plastic bottle caps and containers.
- Nickel. Finely divided, it is used in the hydrogenation of vegetable oils through which margarine is obtained: unsaturated fats become saturated by bombarding hydrogen and this metal accelerates this process.
- Silicon dioxide or silica (SOtwo). It is one of the most used catalysts in the oil catalytic cracking process, added to high pressure and temperatures. The cracking It consists of obtaining simpler substances from a complex hydrocarbon.
- Cobalt (Co) and Molybdenum (Mo). They are substances used on alumina in the catalytic reforming process of petroleum, in which heavy naphtha is separated from sulfur and nitrogen, to increase its octane number.
- Potassium permanganate (KMnO4). It is used as a catalyst for the chemical reaction that transforms alkenes (unsaturated hydrocarbons or olefins) into diols.
- Platinum. This metal is used as a catalyst in certain reactions to obtain benzene derivatives, such as cyclohexane, essential in the manufacture of nylon.
- Gold. Recent research shows the effectiveness of gold as a nanocatalyst, that is, when it is found in atomic groups of between eight and two dozen atoms.
- Citric acid. The acid contained in lemon or other citrus fruits slows down (negative catalysis) the process of oxidation of organic matter. This can be verified with a piece of apple.
- Silver. Polycrystalline silver and nanoporous silver in electrocatalysis experiments are effective accelerators of the carbon dioxide (CO2) reduction processes, which allow the efficient obtaining of useful chemical products.