Learn more About the Types of Catalysts

A catalyst is an important part of a chemical reaction. The process is called catalysis. Catalyst determines the speed of reaction. It also functions to slow or sometimes stop a reaction process. There are various types of catalysts used in chemistry. Here are some of the important concepts related to catalysts and the types of catalysts you should know about. 

Catalysis meaning

Catalysis is the addition of a catalyst to a chemical reaction to speed up the rate of the reaction. Catalysts are not utilised and remain unaltered after the reaction. Small amounts of catalyst are frequently sufficient if the reaction is fast and the catalyst recycles quickly; mixing, surface area, and heat are all critical factors in reaction rate. Catalysts often interact with one or even more reactant molecules to produce intermediates, which then yield the ultimate reaction product, regenerating the catalyst in the process.

Types of catalysts in a chemical reaction

Positive catalysts

Positive catalysts are those that speed up the rate of a chemical reaction. It speeds the reaction and decreases the activation energy barriers, allowing a high number of reactive molecules to be transformed into products, increasing the percentage of product yield.

Positive catalysts example

In Haber’s method for preparing NH3, iron oxide functions as a positive catalyst, increasing the yield of ammonia despite less nitrogen reaction.

Negative catalysts

Catalysts slow down the reaction rate, as well as negative catalysts. It slows down the reaction by increasing the activation energy barrier, slowing down the process by reducing the number of molecules which can be transformed into products.

Acetanilide, which serves as a negative catalyst to slow down the hydrolysis process of peroxide into oxygen and water, is used as a negative catalyst to slow down the rate of decomposition of H2O2.

Homogeneous catalysts

The reacting chemicals in a reaction and the catalyst used in that action are not in a similar state of matter in this sort of catalysis. Adsorption and intermediate chemical production are both involved in heterogeneous catalysis. The reactant molecule is adsorbed on the catalyst’s surface’s activation centre. These come together to generate an active complex, which is a compound in between. This substance decomposes into products.

The products are dissolved from the surface as soon as they are created, with no time delay. Adsorption of reagents on the surface of the catalyst, synthesis of intermediate compounds, and dissociation into a product are all part of heterogeneous catalysis.

Examples

• On the top of the nickel, ethene is hydrogenated to ethane.
• On the surface of the catalyst, ether and hydrogen molecules are adsorbed.
• Occlusion occurs when hydrogen takes up the majority of the activation centre.
• To generate an active compound, ethane molecules attack their double bond area.
• Ethane is formed when ether combines with active hydrogen.
• This ethane is absorbed on the catalyst’s surface.

Heterogeneous catalysts

Homogeneous catalysis is defined as catalysis where the catalyst and the reactants are in a similar state of matter. Homogeneous catalysts work in the same order as the reactants. Homogeneous catalysts and substrates are often suitable solvents. One example of homogeneous catalysis is the effect of H+ on the esterification of carboxylic acids, like the creation of methyl acetate from acetic acid and methanol. High-volume processes such as hydroformylation, hydrosilylation, and hydrocyanation necessitate a homogeneous catalyst. For inorganic chemists, homogeneous catalysis is often confused with organometallic catalysts.

Many homogeneous catalysts, however, are not organometallic, as the use of cobalt salts to catalyse the oxidation of p-xylene to terephthalic acid demonstrates.

While transition metals receive a lot of attention in catalysis research, small organic molecules lacking metals can also have catalytic capabilities, as evidenced by the lack of transition metals in so many enzymes. In the early 2000s, such organocatalysts were termed a “new breed,” and they compete with metal-based catalysts.

Example – The lead chamber process is used in the manufacture of sulphuric acid. In this process, nitric oxide gas is used as catalysis.

Autocatalysis

An autocatalytic reaction is one in which one of the products catalyses the process. The rate of reaction in this sort of reaction is initially very sluggish, but as the reaction progresses and products are generated, the rate of reaction increases. In this case, the product catalyses self-production.

A + B →2B is an autocatalytic process in which A interacts with B to create B while the original B, which serves as a catalyst, is kept.

Example – The Mn2+ ions are a result of the interaction of oxalic acid with permanganate, and they also act as a catalyst. The reaction starts slowly and then picks up speed as more and more byproducts are generated.

Conclusion

Catalysts are important agents in a chemical reaction. Many industrial processes rely on chemical reactions to transform raw materials into valuable products, and catalysis is at the heart of them. Catalysts are used to make plastics and a variety of other industrial goods. These agents are also used in biofuels and other renewable sources.