The term ‘Catalyst’ is widely used in chemistry, particularly while studying chemical processes. Although some chemical reactions occur fast, others take a long time and need the use of additional materials or effort. Catalysts are chemical substances that support chemical reactions by increasing their pace. A catalyst is often used to accelerate or raise the pace of a chemical process. Catalysts can be crystalline, fluid, or gas in nature. Metals or their equivalents, including sulfur compounds and halides, are among the solid catalysts. They are also made from semi-metallic components such as boron, aluminum, and silicon. Catalysts can also be liquid or gaseous materials in their pure state. Let us understand what is a catalyst and its types in detail.

Brief History of Catalysts
Gottlieb Kirchhoff, a Russian scientist of German ancestry, researched the first chemical process in organic synthesis that used a catalyst in 1811. In 1835, a Swedish scientist called Jöns Jakob Berzelius has used the term catalysis to refer to crucial techniques that were accelerated by certain substances. The compounds remained unchanged after the reaction.

Types of Catalysts with Examples
Depending on the necessity or demand of the chemical reaction, many types of catalysts can be utilized. They are as described in the following:
●    Positive Catalysts: Positive catalysts are the ones that accelerate the pace of a chemical process. It accelerates the process by decreasing the activating intrinsic limitations, allowing a high number of reactant intermediates to be transformed into products, raising the production yield.
Example: In the manufacture of NH3 using Haber's method, iron oxide works as a positive catalyst, increasing ammonia output despite less nitrogen reactivity.
●    Negative Catalysts: These are the catalysts that slow down the pace of a chemical reaction. It decreases the occurrence of reactivity by raising the activation energy required, which reduces the number of reactant molecules that may be converted into products, and therefore the time is taken to complete a reaction increases.
Example: Acetanilide is used as a negative catalyst to slow down the breakdown of hydrogen peroxide into oxygen and water.
●    Catalyst Poisons or Inhibitors: Catalyst toxins or blockers are compounds that reduce catalyst action. In the electrolysis of water of an alkyne to an alkene, the catalyst palladium is dissolved with barium sulphate in quinolone solutions, and the process is terminated at the alkene level. The catalyst is named Lindler's catalyst.
●    Promoter or Accelerators: A promoter or accelerator is a chemical that boosts the activity of the catalyst. In Haber's method, for instance, molybdenum or a combination of potassium and aluminum compounds operate as Promoters.

What are the units of Catalysts?
There is a separately formulated SI unit to evaluate a catalyst's enzymatic performance and it is named "katal." It is also measured in moles per second. If we were to characterize a catalyst's efficiency, we might use the turnover frequency (or TON). The flip-over frequency (TOF), which is TON per temporal unit, can be used to measure catalytic activity. Similarly, the enzyme unit is its scientific counterpart.

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What is a catalyst?