Influence of Supports on Pd Catalysts for the Selective Catalytic Reduction of NOx with H2 and CO

Abstract

A major concern of current commercial catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) (DeNO x ) is the lack of sufficient catalytic activity at low temperatures (below 200°C) that typically occur during cold start and urban driving conditions. To address this issue, a study was undertaken to develop an (H 2 + CO)-SCR Pd-based catalyst to obtain high DeNO x activity in this low-temperature range. A series of catalysts with Pd loaded on supports containing various amounts of γ-alumina (γ-Al 2 O 3 ) (0-65 wt%), CBV-2314 (15-100 wt%), and TiO 2 (0-20 wt%) were tested for DeNO x activity and aging in a catalyst testing unit (CTU). The results showed that each component in the support played a role in the NO x conversion, depending on the temperature. Catalysts with Pd supported on {[γ-Al 2 O 3 (60 wt%)+CBV-2314 (20 wt%)]-TiO 2 (20 wt%)} achieved the best overall DeNO x activity. Catalysts with various Pd loadings (0.05 wt% to 0.5 wt%) were prepared with a {[γ-Al 2 O 3 (60 wt%)+CBV-2314 (20 wt%)]−TiO 2 (20 wt%)} support. The catalysts loaded with 0.05 wt% and 0.2 wt% Pd demonstrated the best overall DeNO x activity (up to 90 % NO x conversion starting at 150°C). These catalysts were subjected to an accelerated aging regime. Based on the aging studies, the 0.2 wt% Pd/{[γ-Al 2 O 3 (60 wt%)+CBV-2314 (20 wt%)]− TiO 2 (20 wt%)} composition was the most active and stable catalyst.

Structural selectivity of supported Pd nanoparticles for catalytic NH3 oxidation resolved using combined operando spectroscopy

“…Therefore an increasing number of NH3 molecules are oxidised to N2O at the Pd surface, as per Equation 2. The formation of N2, as detected by MS can result from the NH3-SCR reaction of adsorbed N2O with incoming gaseous NH3, as in Equation 3 45.…”

The influence of support composition on the activity of Cu:Ce catalysts for selective catalytic reduction of NO by CO in the presence of excess oxygen

“…4 Due to the co-existence of CO and NO in most of the exhaust gases, the reduction of NO by CO as a reducing agent (CO-SCR) has attracted more attention in recent decades. 2,[5][6][7] Noble metal catalysts as efficient catalysts for CO-SCR have been widely used; however, due to the unavailability and high cost of these metals, their practical application is limited. Therefore, development of efficient non-precious and transition metal catalysts has attracted more attention.…”

Green Synthesis of a Cu/SiO2 Catalyst for Efficient H2-SCR of NO

“…For instance, Pt supported on Al 2 O 3 exhibits high activity for NO reduction. Nevertheless, the selectivity to N 2 decreases with increasing reaction temperatures [16][17][18][19][20]. In order to improve its catalytic performance, alternative supports have been systematically tested: SiO 2 , TiO 2 , MnO x , and zeolites, together with perovskite type solids, etc.…”