Isocyanate formation and reactivity on a Ba-based LNT catalyst studied by DRIFTS

摘要: Abstract Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS), coupled with the use of isotopically-labeled reactants ( 15 N 18 O 13 CO), were employed to study formation isocyanate species during NOx reduction CO, as well reactivity toward typical exhaust gas components. DRIFTS demonstrated that both Ba–NCO Al–NCO simultaneously formed by CO under dry lean-rich cycling conditions. The band was more intense than Al–NCO, became comparatively stronger at high temperatures. During rich purging 300 400 °C, a near linear relationship found between increase in intensity decrease Ba–NO 3 intensity, suggesting is directly derived from reaction Ba nitrate CO. Both temperature-programmed surface (TPSR) isothermal modes (ISR) utilized lean Simultaneous spectrometric measurements TPSR indicated H 2 O, , NO NO/O took place almost immediately temperature raised above 100 °C, all NCO removed below 300 °C. evolution IR bands ISR 350 °C kinetics hydrolysis are fast, although delay not initial product reaction. In contrast, immediate observed NO + O . Overall, it can be inferred conditions sole reductant, mainly generated via after switch conditions, rather being evolved phase. However, presence water, undergoes rapid phase, generation proceeding NH