There are lots of different types of catalysts: Homogeneous (molecule, typically small, in solution), heterogeneous (solid or porous surface) and enzymes (biolo

There are lots of different types of catalysts: Homogeneous (molecule, typically small, in solution), heterogeneous (solid or porous surface) and enzymes (biological molecules.) Many do work by bringing reactants together so that the relevant fragments can combine. Chemical reactions are usually described as going through an energetic transition state and many catalysts stabilize this state so that the reaction can "get over the hill" and become product. Of course, it also stabilizes it for the reverse reaction so the products can become reactants again. The overall equilibrium is not changed. Both reactions speed up. If, however, one extracts the product as it is formed, more product will be formed and hence catalysts are incredibly useful since, by definition, they are not consumed by the reaction - i.e. you get the catalyst back so it can continue to do its work. Here's a good example of how enzymes catalyze reactions: https://pdb101.rcsb.org/learn/videos/how-enzymes-work https://pdb101.rcsb.org/learn/videos/how-enzymes-work The last 1/3 of this old video from Shell describes how catalytic cracking, a crucial part of oil refining, works. It covers practical reactor considerations, including getting the products out so more are formed and 'poisoning' where a catalyst's efficiency is reduced by contamination and how that's dealt with in a continuous process. https://www.youtube.com/watch?v=hC1PKRmiEvs https://www.youtube.com/watch?v=hC1PKRmiEvs