Showing papers by "Sounak Roy published in 2007"
TL;DR: In this article, the three way catalytic activity of this catalyst was investigated by performing NO+CO reaction and CO and hydrocarbon oxidation and the rates and the apparent activation energies of the reaction for NO reduction by CO and CO/HCO and hydrocarbons oxidation were determined.
Abstract: The catalyst $Ce_{0.98}Pd_{0.02}O_{2-\delta}$ was synthesized by combustion synthesis method and characterized by XRD and XPS. The three way catalytic activity of this catalyst was investigated by performing NO+CO reaction and CO and hydrocarbon oxidation. The rates and the apparent activation energies of the reaction for NO reduction by CO and CO and hydrocarbon oxidation were determined and the rates were higher than the reported values. The $N_2$ selectivity in NO+CO reaction was around 80%all over the temperature region and showed complete selectivity at high temperatures. A reaction mechanism of NO+CO reaction was proposed and the experimental findings were verified with the predicted model. The high rates of the NO+CO reactions even in the presence of oxygen and the complete selectivity to the products are rationalized by the high dissociative chemisorption of adsorbed NO over the catalyst, which is for the vacant sites in $CeO_2$ lattice due to presence of $Pd^{2+}$ in $Ce^{4+}$ position. The catalyst also showed high rates and lower activation energies for the oxidation of CO and hydrocarbons.
80 citations
TL;DR: In this article, a photocatalyst for NO reduction and CO oxidation by creating redox adsorption sites and utilizing oxide ion vacancy in titania was developed, which was synthesized for the first time by solution combustion method.
Abstract: The present study aims at developing a new photocatalyst for NO reduction and CO oxidation by creating redox adsorption sites and utilizing oxide ion vacancy in titania. For this purpose, Pd ion-substituted TiO2, Ti1-xPdxO2-δ, was synthesized for the first time by solution combustion method. The photocatalytic activity was investigated with increasing Pd substitution and the optimum concentration was found to be 1 atom % Pd ion in TiO2. The reduction of NO was carried out both in the presence and in the absence of CO. Despite competitive adsorption of NO and CO on the Pd2+ sites, the reduction of NO was 2 orders of magnitude higher than unsubstituted TiO2. High rates of photooxidation of CO with O2 over Ti1-xPdxO2-δ are observed at room temperature. It was shown that enhanced CO oxidation at Pd2+ ion site and O2 or NO photo dissociation at oxide ion vacancy is responsible for the enhanced catalytic activity.
66 citations
TL;DR: In this article, a new catalytic activity was investigated by performing CO oxidation, hydrocarbon oxidation and NO reduction in the presence of CO, and the model based on competitive adsorption of NO and CO on $Pd^{2+}$, NO chemisorption and dissociation on oxide-ion vacancy fitted the experimental data.
Abstract: This study aims at synthesizing a new by substituting 1 atom% $Pd^2^+$ in ionic state in $TiO_2$ in the form of $Ti_{0.99}Pd_{0.01}O_{1.99}$ with oxide-ion vacancy. The catalyst was synthesized by solution combustion method and was characterized by XRD and XPS. The catalytic activity was investigated by performing CO oxidation, hydrocarbon oxidation and NO reduction. A reaction mechanism for CO oxidation by $O_2$ and NO reduction by CO was proposed. The model based on CO adsorption on $Pd^{2+}$ and dissociative chemisorption of $O_2$ in the oxide-ion vacancy for CO oxidation reaction fitted the experimental for CO oxidation. For NO reduction in presence of CO, the model based on competitive adsorption of NO and CO on $Pd^{2+}$, NO chemisorption and dissociation on oxide-ion vacancy fitted the experimental data. The rate parameters obtained from the model indicated that the reactions were much faster over this catalyst compared to other catalysts reported in the literature. The selectivity of $N_2$, defined as the ratio of the formation of $N_2$ and formation of $N_2$ and $N_2O$, was very high compared to other catalysts and 100% selectivity was reached at temperature of $350 ^oC$ and above. As the $N_2O + CO$ reaction is an intermediate reaction for NO + CO reaction, it was also studied as an isolated reaction and the rate of the isolated reaction was less than that of intermediate reaction.
56 citations
TL;DR: In this article, the reaction mechanism and kinetics of photoreduction of NO by CO were investigated in the presence of Pd-ion-substituted nano-TiO 2, Ti 1-x Pd x O 2-δ, which was synthesized via a solution combustion method.
Abstract: The objective of the present study is to develop the reaction mechanism and kinetics of photoreduction of NO by CO. For this purpose, the reactions were conducted in the presence of Pd-ion-substituted nano-TiO 2 , Ti 1-x Pd x O 2-δ , which was synthesized via a solution combustion method. The photocatalytic activity was investigated with unsubstituted TiO 2 , 1% Pd/TiO 2 (imp), and Ti 1-x Pd x O 2-δ (where x = 0.05-0.3). No appreciable NO conversion was observed over unsubstituted TiO 2 , although, despite competitive adsorption of NO and CO on the Pd 2+ sites, there was a significant reduction of NO over Ti 1-x Pd x O 2-δ . The kinetic model showed that the enhanced catalytic activity is due to the NO photodissociation at the oxide-ion vacancy.
19 citations