LaFeO3 Perovskites Obtained from Different Methods for NO + CO Reaction, Modeling and Optimization of Synthesis Process by Response Surface Methodology

Study of Ce, Ca, Fe, and Mn-Doped LaCoO3 Perovskite Oxide for the Four-Way Purification of PM, NOx, CO, and HC from Diesel Engine Exhaust

Perovskite-type catalysts were widely used in the field of automobile exhaust purification due to their inherent physicochemical properties and excellent doping characteristics. A series of La_1−xM_xCo_1−yN_yO₃ (M = Ce, Ca; N = Fe, Mn) perovskite-type catalyst samples were prepared by sol-gel method for the four-way purification of PM, NO_x, CO, and HC emitted by diesel exhaust. The activity of catalyst samples was tested by simulation experiments and hydrogen temperature-programmed reduction (H₂-TPR). Catalyst samples were characterized by means of XRD, FT-IR, SEM, BET, and XPS analysis. The results demonstrated that the perovskite-type catalyst samples with a particle pore size of 3–5 μm can be prepared by sol-gel method. When A-site of LaCoO₃ perovskite-type oxide was doped by cerium ions, the catalyst samples produced small distortion. The doping of cerium ions to A-site was more conducive to the four-way purification of diesel exhaust than calcium ions. La_0.8Ce_0.2CoO₃ perovskite-type samples showed the best purification efficiency, and the purification efficiencies of PM, NO_x, CO, and HC were 90%, 85%, 94%, and 100%, respectively. When the B-site of La_0.8Ce_0.2CoO₃ perovskite was doped with iron ions, the purification efficiency of catalyst samples for PM and NO_x can be further enhanced. When the B-site of La_0.8Ce_0.2CoO₃ perovskite was doped with manganese ions, the purification efficiency of the catalyst samples for PM can be further enhanced. It can be seen from the simulation experiments that La_0.8Ce_0.2Co_0.7Fe_0.3O₃ perovskite was the best doping amount, and the purification efficiencies of PM, NO_x, CO, and HC were 95%, 92%, 94%, and 100%, respectively.

The sol-gel autocombustion as a route towards highly CO2-selective, active and long-term stable Cu/ZrO2 methanol steam reforming catalysts

The adaption of the sol-gel autocombustion method to the Cu/ZrO₂ system opens new pathways for the specific optimisation of the activity, long-term stability and CO₂ selectivity of methanol steam reforming (MSR) catalysts. Calcination of the same post-combustion precursor at 400 °C, 600 °C or 800 °C allows accessing Cu/ZrO₂ interfaces of metallic Cu with either amorphous, tetragonal or monoclinic ZrO₂, influencing the CO₂ selectivity and the MSR activity distinctly different. While the CO₂ selectivity is less affected, the impact of the post-combustion calcination temperature on the Cu and ZrO₂ catalyst morphology is more pronounced. A porous and largely amorphous ZrO₂ structure in the sample, characteristic for sol-gel autocombustion processes, is obtained at 400 °C. This directly translates into superior activity and long-term stability in MSR compared to Cu/tetragonal ZrO₂ and Cu/monoclinic ZrO₂ obtained by calcination at 600 °C and 800 °C. The morphology of the latter Cu/ZrO₂ catalysts consists of much larger, agglomerated and non-porous crystalline particles. Based on aberration-corrected electron microscopy, we attribute the beneficial catalytic properties of the Cu/amorphous ZrO₂ material partially to the enhanced sintering resistance of copper particles provided by the porous support morphology.