elements in large, stationary, ng-fueled, spark-ignited engine cats can be and are cleaned routinely. this is done because these large bore, continuous-duty engines can pass a lot of lube oil additives[ash] in the exhaust that eventually coat the catalytically reactive elements, rendering them ineffective.
this cleaning can be cost effective for this industrial horsepower. whether it makes any economic sense for an automotive application cat would have to be explored. i sort of doubt it would, though.