What is the role of catalyst in various reactions?

In summary, catalysts play a crucial role in many reactions, particularly in heterogeneous catalysis where the reactants adsorb to the surface of a solid catalyst. The catalyst not only weakens bonds, but also increases effective concentration of the reactants. The selection of a specific metal for a reaction is often determined experimentally and can be influenced by factors such as cost and practicality. Despite advancements in understanding catalysis, there is still much to learn about the intricacies of catalyst design.
  • #1
jd12345
256
2
There are many reactions in which i don't understand what the role of catalyst is.

Reactions like hydrogenation of alkenes , use of Ni i understand - it kinda breaks the hydrogen-hydrogen bond and provide it for the alkene.
In contact process i.e. SO2 + 1/2O2 ----> SO3 catalyst is V2O5. I understand this as V2O5 reacts with SO2 to provide oxygen and then oxidses

But i don't understand catalyst in reactions like :- habers process i.e. N2 + 3H2 ----> 2NH3
catalyst is Fe but what is its role?
similarly CO + 2H2 ---> CH3OH catalyst is cobalt but what is its use??
CH3OH ----> HCHO + H2 catalyst is heated copper but how does it remove hydrogen

Plz tell me what are the role of catalyst in these 3 reactions -
There are many other reactions where catalyst are used and i don't understand but its not possible to ask them all so if you can tell me in general too it'll be very helpful
 
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  • #2
The processes you mention are all cases of heterogeneous catalysis. You have a catalyst (typically a solid in many applications) and the reactants adsorb to the surface. The bond weakens, such as in N2, with a triple bond between the nitrogen atoms. You also can gain an increase in effective concentration (instead of the reactants just floating around in the gas or liquid phase, they're all now adsorbed to the catalyst surface).

Be sure to read the link, and I would Google "heterogeneous catalysis." There's plenty of information out there, as it's both an example of really interesting chemistry but also very practical chemistry.
 
  • #3
how do we determine which metal to use in which reaction?
example: in habers process iron is used. This might be because it adsorbs nitrogen very efficiently. But what makes it such a good adsorbent of nitrogen?
 
  • #4
jd12345 said:
how do we determine which metal to use in which reaction?

Experimentally.

From what I know selecting catalysts is still kind of a voodoo.
 
  • #5
okay, but the question is :- why do certain metals adsorb specific gases better than others? Iron is used in habers process, why?
There must be some reason!
 
  • #6
jd12345 said:
okay, but the question is :- why do certain metals adsorb specific gases better than others? Iron is used in habers process, why?
There must be some reason!

Possibly due to the Iron having few variable oxidation states that makes it more suitable than say, Manganese.
 
  • #7
For the Haber-Bosch process, at least, there's an element of pure practicality. Back in the day, using iron was cheaper/less troublesome than getting an adequate amount of ruthenium or osmium (which are better catalysts, although I think there was also an issue with catalytic lifetime/catalyst poisoning, but don't quote me on that). The process is also sensitive to the surface topography.

Like Borek said - catalyst design still has vast amounts of voodoo in it. While there are methods to investigate the detailed molecular processes at work, there is still a long way to go before we can design catalysts off the top of our head and have them work just as we expect.
 
  • #8
ok thank you
 

1. What is a catalyst?

A catalyst is a substance that speeds up the rate of a chemical reaction without being permanently altered or consumed in the process. It works by providing an alternative pathway for the reaction with lower activation energy, making it easier for the reactants to form products.

2. What are the benefits of using a catalyst in a reaction?

Catalysts can significantly increase the rate of a reaction, which can save time and resources in industrial processes. They also allow reactions to occur at lower temperatures, reducing energy costs and decreasing unwanted byproducts. Additionally, catalysts can be reused multiple times, making them cost-effective in the long run.

3. How does a catalyst affect the overall energy of a reaction?

A catalyst lowers the activation energy of a reaction, meaning that less energy is required for the reaction to occur. This results in a lower overall energy for the reaction, making it more favorable and efficient.

4. Are all catalysts the same?

No, there are different types of catalysts that work in different ways. Some catalysts can only be used for specific reactions, while others are more general and can be used in a variety of reactions. Catalysts can also be classified as homogeneous (in the same phase as the reactants) or heterogeneous (in a different phase than the reactants).

5. Can a catalyst make a reaction go in the opposite direction?

No, a catalyst cannot change the thermodynamics of a reaction. It can only speed up the rate of the reaction in the forward direction. However, using a different catalyst or altering the conditions of the reaction may result in a different equilibrium position.

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