Catalysts work by lowering the energy needed to start a reaction. They are not used up or destroyed in the process. A solid catalyst provides a special surface for the reaction to happen.
The reactant molecules stick to the active sites on this solid surface. This sticking process is called adsorption. Once stuck, the chemical bonds inside the reactant molecules become weak.
This makes it much easier for them to break and form new bonds. Finally, the new product molecules break free from the surface. This final step is called desorption and frees the active site for the next molecules.
Because the reaction only happens on the surface, the total surface area is critical. Factories often crush the catalyst into a fine powder. They might also form it into sponge-like pellets full of tiny holes.
This creates millions of active sites and speeds up the reaction even more. A huge benefit is that solid catalysts are very easy to remove. Chemists can simply filter the solid away from the liquid products. This saves money because the factory can reuse the catalyst many times.