Are catalysts ever permanently changed in a reaction?
Ideally no, but when has chemistry ever been ideal?
Catalysts are often said to be
With industrial operations, most of the time, catalysts are so active, that a little new stuff can be added periodically. Catalysts are so active that this can often be performed even if the catalyst is a high-value metal: the catalyst loading can be so low as to allow consideration of the cost of the catalyst to be trivial.