Search

Glucose-free and glucose-containing LaCoO3(-G), La0.9Sr0.1CoO3(-G), and La0.9Ce0.1CoO3(-G) perovskite catalysts were synthesized via the sol–gel method, over which the oxidation performance of high-concentration CO was investigated. The experimental results indicate that the catalytic activity can be improved by facilely adding glucose during the preparation where glucose creates a reducing atmosphere and takes away the oxygen atoms of perovskites to form more oxygen vacancies and Co3+. CO self-sustained combustion is favorably achieved and La0.9Ce0.1CoO3-G shows the best catalytic performance. Combining the XPS, H2-TPR, O2-TPD and CO-TPD results, the outstanding performance of La0.9Ce0.1CoO3-G is mainly ascribed to the relatively higher concentrations of Co3+, Ce3+ and oxygen vacancies. The reaction was found to follow the Langmuir–Hinshelwood (L–H) mechanism by in situ IR spectroscopy and kinetic results. Furthermore, La0.9Ce0.1CoO3-G exhibits good high-temperature durability with unchanged CO conversion of 100% at 760 °C. It is suggested that the addition of glucose and the impregnation of Sr or Ce in perovskites is a feasible strategy to design industrial catalysts for CO self-sustained combustion. [ABSTRACT FROM AUTHOR]

Cubic Cu 2 O micro/nanocrystals were successfully synthesized by liquid-phase reduction using copper salt of CuSO 4 or CuCl 2 ·2H 2 O, and glucose or ascorbic acid as reducing agent, respectively. The activity of the catalysts was evaluated by light-off curves of CO self-sustained catalytic combustion via temperature-programmed oxidation of CO (CO-TPO), with the results showing the activity of catalysts following the order of Cu 2 O–Cl-GLU > Cu 2 O– S -GLU > Cu 2 O– S -AA > Cu 2 O–Cl-AA, (Cl denotes CuCl 2 ·2H 2 O, GLU denotes glucose, S denotes CuSO 4 and AA denotes ascorbic acid, respectively), corresponding to the ignition temperature of 109 °C, 122 °C, 137 °C and 186 °C, respectively. The crystal structure, elemental valence, morphology and redox property of the prepared catalysts were analyzed by using various characterization techniques. Combined with in situ infrared spectrum, the CO self-sustained catalytic combustion over Cu 2 O catalysts mainly follows the Mars-van-Krevelen (M-v-K) mechanism: the adsorbed and activated CO reacts with lattice oxygen to yield CO 2 and oxygen vacancy, and then the oxygen vacancy can be replenished by gaseous oxygen. Combined with catalytic performance of high-concentration CO, it is found that the catalysts prepared using glucose as reducing agent are more angular compared with ascorbic acid. The Cu 2 O–Cl-GLU synthesized with glucose and CuCl 2 ·2H 2 O exhibits the best catalytic activity among all the catalysts tested, attributing to its more obvious edge and rough crystal surface. The unique structure of Cu 2 O–Cl-GLU leads to the high exposure rate and coordination unsaturation of atoms on the cubic Cu 2 O micro/nanocrystals that can improve the ability of activating gaseous O 2 and low temperature reducibility, and consequently facilitating the catalytic activity. Cycle path diagram of CO oxidation reaction (a) and schematic diagram of CO oxidation reaction on Cu 2 O (b). [Display omitted] • Effects of reducing agent on catalytic properties is greater than that of copper salt. • High concentration CO can achieve self-sustained catalytic combustion on obtained Cu 2 O. • Glucose enhances unsaturation of Cu atoms contributing to high activity. • Chemically adsorbed oxygen on Cu 2 O surface promotes CO ignition. [ABSTRACT FROM AUTHOR]