Title : Complete oxidation of CO and propene as model component of diesel exhaust and VOC using manganese oxide supported on octahedral (AlO63-)-Ce3+
Abstract:
The complete oxidation of propene and CO as model components of diesel engine exhaust and VOC has been investigated on series of Ce doped MnOx/Al2O3 catalysts. The optimized MnOx/Al2O3 doped with 0.05 mol Ce showed higher CO and propene oxidation activity at 200 oC and 215 oC respectively. The physicochemical properties of catalysts were analyzed by using XRD, RAMAN, NMR, H2-TPR, HRTEM, and XPS techniques. The formation of Mn3O4 and Mn4+ species were observed on the catalyst surface. 27Al Solid-state NMR showed formation of octahedral [AlO63-]-Ce3+ species, which was responsible for the donation of oxygen required for CO and propene oxidation. The formation of adsorbed oxygen and oxygen vacancies were observed on the catalyst surface due to the synergistic interaction between Mn, Ce, and Al1,2. The HRTEM results showed formation of well dispersed Mn over Al-O-Ce, which facilitate the proton abstraction required for the activation of hydrocarbon. The mechanistic and kinetic aspects of CO and propene oxidation on catalyst surface have been reported in detail.
The MnOx/0.05Ce-0.45Al2O3 showed facile redox properties of Mn3O4 and MnO2. The well-dispersed manganese oxides and Ce on Al2O3 support lead to increase in distortion and consequently oxygen vacancies, which eventually increases the mobility of oxygen from bulk to surface of the catalyst3. The increase in Ce concentration causes the Mn agglomeration, which shifts the catalytic activity towards higher temperature. However, coating the catalyst on the monolith and their investigation under realistic conditions is the challenge and would be the next step of the research work.
Audience take-away:
- For abatement of VOCs and CO emission from automobiles the non-noble metal-based catalyst system like Ce doped MnOx/Al2O3 has shown relatively low temperature activity.
- It shows effect of support (Al2O3) modification on CO and Propene oxidation activity.
- After Ce doping in MnOx/Al2O3 generation of different active sites, active O-species and structural defects required for low temperature oxidation.
- The improvement in low-temperature oxidation activity of CO and Propene was observed due to the strong synergistic interaction of Mn-Ce, enhancement of redox properties of Ce (Ce3+/Ce4+), formation of surface oxygen vacancies and availability of active oxygen species (O-, O2-, O2-, etc.)
- The formation of oxygen vacancies is responsible for the activation of gaseous oxygen at a lower temperature.
