That's a good point.
My question had to do with the last step of the process. Let's say you were making Chlorobenzene from Benzene and chlorine using Iron (III) Chloride as a catalyst.
I was confused as to which molecule/atom accepted the proton from the benzene ring. My problem was that if FeCl3 accepted to proton then why would it not become CoCl3. I was sure this way of thinking was wrong, and it was. The FeCl3 donates its electron to a chlorine atom, and then the chlorine anion accepts the proton to make hydrogen chloride.