Types of Catalysts and Loading Methods:- A catalyst is a material added to a chemical reaction to increase the rate or speed at which the reaction takes place. Every reaction proceeds by a certain path or mechanism called reaction mechanism. Each reaction mechanism has a specific activation energy associated with it. The activation energy of a chemical reaction is the minimum amount of energy required to bring the reactants to the condition where they begin to react with each other and thus carry out the chemical reaction. If so much energy is not available, no chemical reaction will take place. The introduction of a catalyst into a chemical reaction results in a different pathway or a different mechanism that has a much smaller activation energy associated with it than the pathway or mechanism without the catalyst.
When a catalyst is introduced into a chemical reaction, the reaction proceeds in two paths, but most reactants follow the path corresponding to the lower activation energy. All of the catalyst used during the reaction is recovered at the end of the reaction when it is complete. The catalyst can be in the same phase as the reactants and the reaction process is called homogeneous catalysis. If the catalyst is in a different phase from the reactants, the reaction process is called multiphase catalysis.
Types of catalysts
Homogeneous catalyst:
The catalyst belongs to the same phase as the reactants, so when the catalyst is introduced into a chemical reaction, it mixes easily with the reactants, leading to high selectivity and high activity due to their interaction. The reaction mechanism of such catalysts is usually well known. Catalyst regeneration is usually difficult because the separation of the components is inherently difficult.
Multiphase catalysts:
They have catalysts that do not belong to the same phase as the reactants. They are the most common type of catalyst in industry because it is much easier to separate them and recover the product and catalyst when they are introduced into a chemical reaction. They are available in powdered, granular, and loaded on a carrier form. The advantage of using catalysts in powder form is that there is a large surface area available for the reaction. The disadvantage is that the smaller particles tend to agglomerate and thus lose their catalytic ability. This problem can be solved if the catalyst is dispersed onto a carrier. They have relatively low activity and selectivity. The underlying reaction mechanism is unknown.
Biocatalysts:
Natural biocatalysts such as enzymes and nucleic acids are used in industry to carry out chemical reactions. They are becoming increasingly popular in industry compared to conventional catalysts because of their high activity, high reactivity and ease of product separation, and because catalyst regeneration is inherently optional.
Catalyst loading methods
Vacuum loading:
The catalyst is first placed in a hopper and then pneumatically conveyed into the reactor.
Direct loading from large bags:
The catalyst is placed in bags and the bags are lifted with the help of a crane. They pass through a dust protection system before falling into the reactor.
Intensive loading:
A device is used to distribute the catalyst evenly in the reactor to reduce void space and minimize channel flow. Rotary devices or propellants can be used.
Cloth bag loading:
The discharge tube is connected to the nozzle of the hopper and the flexible tube is connected to the other end of the tube. The cloth bag ensures that the tube is always filled with catalyst.
Tube reactor loading:
Catalyst is manually filled directly into the tubes inside the reactor. This is a labor intensive task.
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