Catalytic urea hydrolysis by composite metal oxide catalyst towards efficient urea-based SCR process: performance evaluation and mechanism investigation

As a promising option to provide gaseous NH 3 for SCR system, catalytic urea hydrolysis has aroused great attention, and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis. Therefore, a composite metal oxide (TiO 2 @Al 2 O 3 ) catalyst was prepared by a simple hydrothermal method, with mesoporous alumina (γ-Al 2 O 3 ) as substrate. The results verify the mesoporous structure and submicron cluster of TiO 2 @Al 2 O 3 , with exposed crystal faces of (101) and (400) for TiO 2 and γ-Al 2 O 3 , respectively. The electronegativity difference of Ti 4+ and Al 3+ changes the charge distribution scheme around the interface, which provides abundant acid/base sites to boost the urea hydrolysis. Consequently, for an optimal proportioning with nano TiO 2 content at 10 wt.%, the hydrolysis efficiency can reach up to 35.2 % at 100 °C in 2 h, increasing by ∼7.1 % than that of the blank experiment. 13 C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis. Theoretical calculations are performed to clarify the efficient H 2 O decomposition at the interface of TiO 2 @Al 2 O 3 . The result offers a favorable technology for energy-efficiency urea hydrolysis.