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Self-sustained catalytic combustion is a promising strategy to remove CO from the off-gas produced during steelmaking, where the potential catalysts are bulk copper-cerium-zirconium mixed oxides or those supported on TiO 2 or ZSM-5 substrates. In this study, the effects of the catalyst support on the CO catalytic ignition performance and reaction pathways were investigated by FTIR coupled with a novel in-situ cell, together with the state-of-the-art characterization techniques. The Infrared (IR) transmission cell equipped with a magnetically driven system, could effectively prevent overlaps between active intermediate peaks (Cu+-CO and Cu+(CO) 2) and gaseous CO peaks. The Cu+ cations located at the phase interface are the main active sites. The Cu and Ce interactions lead to the formation of solid solutions of CuCe 0.75 Zr 0.25 O δ (CuCeZr). The monocarbonyls [Cu+-CO] are the dominant species during CO oxidation, and the vacancies in the solid solutions are occupied by oxygen, accelerating the oxygen cycle. The TiO 2 or ZSM-5 supports promote copper dispersion over CuCe 0.75 Zr 0.25 O δ /TiO 2 (CuCeZr/T) and CuCe 0.75 Zr 0.25 O δ /ZSM-5 (CuCeZr/Z) catalysts, which can be attributed to their high surface areas (168.2 and 346.3 m2/g, respectively), while the Cu-Ce interactions are less relevant. Hence, CO oxidation mainly occurs at the phase interface between copper oxide and TiO 2 /ZSM-5. Dicarbonyls [Cu+(CO) 2 ] are the main intermediates for the CuCeZr/T and CuCeZr/Z catalysts, and the Cu2+ species are reduced to form dicarbonyls that also take part in the oxidation process. Although a well copper dispersion enhances the activity of individual copper sites on the CuCeZr/T and CuCeZr/Z catalysts, considering the redshift of the carbonyl bands and the increase in CO adsorption, the close interactions and high contents of Cu and Ce favor the local accumulation of heat and mass transfer over bulk CuCeZr, leading to the ignition of CO at low temperatures. [Display omitted] • CuCe 0.75 Zr 0.25 O δ and CuCe 0.75 Zr 0.25 O δ /TiO 2 and CuCe 0.75 Zr 0.25 O δ /ZSM-5 catalysts were designed. • The structure-activity relationship was obtained. • The self-sustained combustion and stability limit of CO were carried out. • The in-situ IR with a novel magnetically driven IR cell was designed and performed. • The intermediate species and reaction pathways over different catalysts were evidenced. [ABSTRACT FROM AUTHOR]

Catalytic oxidation technology is a promising strategy to eliminate carbon monoxide (CO), volatile organic compounds (VOC) and other emissions from industrial boilers and to address ammonia (NH 3) escape. Herein, we demonstrate the potential of copper-cerium-zirconium mixed oxides or those supported on TiO 2 or ZSM-5 substrates for the simultaneous catalytic removal of CO, toluene and NH 3. Among them, CuCeZr/ZSM-5 exhibits the best co-processing ability for mixed gases. In situ infrared spectroscopy analyses suggest that there is a competitive adsorption among CO, toluene and NH 3 , and the inhibition is in descending order of toluene＞CO＞NH 3. Based on the physical-chemical characterizations, the Cu-Ce interfacial structure plays an important role in CO ignition at low temperatures. More importantly, the abundant acidic sites on the ZSM-5 support can improve the stability of adsorbed NH 3 at high temperatures, resulting in the best NH 3 catalytic oxidation performance of CuCeZr/ZSM-5 with no secondary pollutants of NO x. This study provides a strategy for the catalyst design to eliminate multiple pollutants targeting the properties of pollutants. [Display omitted] • Simultaneous removal of CO, toluene and NH 3 was achieved by CuCeZr based catalyst. • The best mixed gas treatment was observed for CuCeZr/ZSM-5 catalyst. • Cu-Ce interfacial structure allows preferential ignition of CO at low temperature. • The acidic sites on the ZSM-5 promoted the adsorption and oxidation of NH 3. [ABSTRACT FROM AUTHOR]

CO self-sustaining catalytic combustion tends to be one of potential means to achieve efficient conversion of off-gases from steelmaking. Building model catalysts to investigate the reaction process academically is essential to design optimized catalysts and Cu 2 O exposing (1 0 0), (1 1 1) and (1 1 0) planes are excellent materials. Herein, morphological CeO 2 /Cu 2 O inverse model catalysts were synthesized to reveal the synergistic effect and reaction mechanism. It is demonstrated that the ignition temperature is lowered on the interface by synergistic effect, which dominates the ignition, while the combustion after ignition is controlled by Cu 2 O planes providing abundant lattice oxygen to react with CO. Additionally, exposure of different planes plays a significant role in the reaction since O-termination on (1 0 0) inhibits the interaction, whereas Cu-termination on (1 1 0) surface structure and coordinately unsaturated Cu+ on open (1 1 1) surface respectively contribute to their superior catalytic performance. [Display omitted] ● Inverse model CeO 2 /Cu 2 O catalysts with regular morphology were successfully prepared. ● Synergistic effect on Cu-Ce interface lowered ignition temperature, dominating the ignition. ● The catalytic activity and synergistic effect vary among planes with (1 1 1) performing the best. ● Exposure of crystal planes with higher activity assists in designing optimized catalysts. [ABSTRACT FROM AUTHOR]

Chemical looping combustion (CLC) and catalytic combustion (CC), which are potential technologies to promote CO→CO 2 efficient conversion and energy conservation for the steelmaking off-gas, are investigated in reaction activity, structure evolution catalysts/oxygen carriers (OCs) and energy recovery using Cu/CeO 2 materials. Activity results suggest that the rod-shaped samples with well-defined (100) crystal faces exhibit higher activity than the sphere-shaped samples with (111) crystal faces, obtaining the optimized copper content of 3 wt%. IR spectra confirmed the proposed reaction pathway that the CO adsorbed on copper sites (Cu+–CO) at the Cu–Ce interface reacts with adjacent surface lattice oxygen. The gaseous oxygen continuously migrates to the external surface of materials, thus resulting in strongly exothermic CO self-sustained combustion during CC. Such a violent reaction does not cause obvious evolution of chemical composition, crystalline phase and structure. Since the active lattice oxygen is gradually consumed but not replenished by external gaseous O 2 in time, CO combustion is not self-sustained during CLC. Therefore, the reduction cycle is no longer confined to the surface of the material but penetrates deep into its body, which accelerates Cu+ enrichment at the surface and leads to irreversible sintering and agglomeration of the material. • The activity of nanorod and nanosphere Cu/CeO 2 was compared. • CLC reaction is more exergy efficiency when burning. • The reason of catalyst deactivation in CLC was investigated. • The migration of active oxygen species in CC and CLC was compared. [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]