A Non‐Phosgene Route Synthesis of Carbamate in Continuous Fixed Bed Reactor

Abstract

AbstractA non‐phosgene route synthesis of carbamate was carried out in a continuous fixed‐bed reactor through oxidative carbonylation of aniline using palladium catalysts and sodium iodide as promoter. The activity, selectivity and stability of both carbon and alumina‐supported palladium catalysts were evaluated. It was found that the alumina‐supported catalyst system exhibited a higher activity and selectivity than that of the carbon‐supported system, and an average aniline conversion of 95.6% and carbamate selectivity of 74.6% were achieved for the Se‐Pd/Al2O3 catalyst after 91 h on stream. Reclamation analysis of the spent Pd/C catalyst suggested that the deactivation was mainly due to the leaching and sintering of palladium metal and the accumulation of insoluble chemicals on catalyst support also aggravated the decline of catalyst activity. When small amounts of selenium were added to the Pd/Al2O3 catalyst, its activity, selectivity and stability were significantly improved which indicated that a promotional effect existed for carbamate formation on a Pd‐Se catalyst system.