He served as vicar to the Diocese of Haarlem and, on the death of Jacobus de la Torre, passing over his coadjutor Johannes van Neercassel, Catz was made vicar apostolic on 31 May 1662. On 9 September 1662, in Cologne he was consecrated titular archbishop of Philippi. He already seems to have been mentally weak at the time of his appointment as vicar apostolic and died insane in Leuven.
During his whole time in office he was wholly guided by Van Neercassel, who succeeded him.