There are a few products out there that claim to clean a catalytic converter, BUT chances are If you have a P0420 or a P0430 you need a new one anyhow.
Cleaning a cat is a farce In my opinion anyhow, as your engine should be well tuned and any emissions from it will likely burn off in the cat due to the heat of combustion/conversion.
If you have a "dirty" cat
chances are you are using oil or excess fuel, or even coolant and the cat isnt running hot enough to digest it.
Running a vehicle with a check engine light runs the risk of damaging a cat depending on the code/malfunction/system. A continuous rich or lean condition can damage a cat, extended operation in rich conditions ( beyond the capabilities of fuel trim operation) , Like leaky injectors will melt the core or monoliyth down to a cinder and plug your exhaust.
Cats wear out as the noble metals used as the catalizing agent are depleted from years of operation, nothing you can do about it except freshen it up with a new one.