Canon regular of the Lateran in September 1832, after graduating in theology at the Roman Athenaeum, he served as auditor of the nunciature in Naples in 1838 and then as professor of ecclesiastical history at the University of Rome. Procurator general of his Order in 1839, abbot of S. Agnese on the Via Nomentana two years later, on 3 April 1843 he was appointed bishop of Terni. After four years, he obtained dispensation from this office due to poor health: Pius IX then restored him to his university chair, assigned him the titular archdiocese of Nisibi, and shortly thereafter appointed him canon of the Basilica of the Lateran and chief chaplain of the Papal army. For reasons that remain obscure, in 1850 he survived an assassination attempt. Elevated to the dignity of Latin Patriarch of Antioch, he spent many of his later years in blindness, devoted to his beloved historical studies and fulfilling delicate assignments entrusted to him by the Pope, who held him in high esteem, especially during the time of the Vatican Council.
His name is linked to the special and constant friendship that bound him to G. G. Belli, whose first collection of poems he published at his own expense. Appointed executor of the poet’s will, with the duty to destroy all unpublished works—namely, almost all of the Romanesque sonnets—he disregarded Belli’s wishes and preserved for posterity such a distinguished poetic work. Among Tizzani’s writings worth recalling are: *I concili generali* (4 vols., Rome 1867–69; the French version by J.-A. Doussot was made from the manuscript, ibid. 1867–69) and *I Concili Lateranensi* (ibid. 1878).