Tight Contact Mode Research Articles

Nanostructured Pr-Rich CexPr1-xO2-δ Mixed Oxides for Diesel Soot Combustion: Importance of Oxygen Lability.

Soot combustion experiments with 5%O2/He were conducted using model soot, and four distinct compositions of CexPr1-xO2-δ oxides of varying nominal cerium compositions (x = 0, 0.2, 0.3, and 1) were prepared. The catalyst samples were comprehensively characterized using techniques such as XRD, Raman spectroscopy, HR-TEM, N2 adsorption at -196 °C, XPS, O2-TPD, H2-TPR, and work function measurements. The Pr-rich compositions, ranging from Ce0.3Pr0.7O2-δ to PrO2-δ, resulted in a significant increase in the total evolved O2 amounts and enhanced catalyst reducibility. However, a decrease in the textural properties of the catalysts was noted, which was particularly important for the pure praseodymia under the synthesis route conducted. The catalytic activity was investigated under the two following contact modes of mixing between soot and catalyst: loose and tight. The results revealed that the catalytic performance is associated with the surface contact in tight contact mode and with the combination of surface/subsurface/bulk oxygen mobility and the BET surface area in loose contact mode. Notably, the temperatures estimated at 10% and 50% of the conversion (T10 and T50) parameters were achieved at much lower temperatures than the uncatalyzed soot combustion, even under loose contact conditions. Specifically, the 50% conversion was achieved at 511 °C and 538 °C for Ce0.3Pr0.7O2 and Ce0.2Pr0.8O2, respectively. While no direct correlation between catalytic activity and work function was observed, a significant relationship emerges between work function values and the formation of oxygen vacancies, whatever the conditions used for these measurements. On the other hand, the ability to generate a high population of oxygen vacancies at low temperatures, rather than the direct activation of gas-phase O2, influences the catalytic performance of Pr-doped ceria catalysts, highlighting the importance of surface/subsurface oxygen vacancy generation, which was the parameter that showed a better correlation with the catalytic activity, whatever the soot conversion value or the mode of contact considered.

Enhanced Catalytic Soot Oxidation over Co-Based Metal Oxides: Effects of Transition Metal Doping.

A series of Co-M (M = Fe, Cr, and Mn) catalysts were synthesized by the sol-gel method for soot oxidation in a loose contact mode. The Co-Fe catalyst exhibited the best catalytic activity among the tested samples, with the characteristic temperatures (T10, T50, and T90) of 470 °C, 557 °C, and 602 °C, respectively, which were 57 °C, 51 °C, and 51 °C lower than those of the CoOx catalyst. Catalyst characterizations of N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photo-electron spectrometry (XPS), and the temperature programmed desorption of O2 (O2-TPD) were performed to gain insights into the relationships between the activity of catalytic soot oxidation and the catalyst properties. The content of Co2+ (68.6%) increased due to the interactions between Co and Fe, while the redox properties and the relative concentration of surface oxygen adsorption (51.7%) were all improved, which could significantly boost the activity of catalytic soot oxidation. The effects of NO and contact mode on soot oxidation were investigated over the Co-Fe catalyst. The addition of 1000 ppm of NO led to significant reductions in T10, T50, and T90 by 92 °C, 106 °C, and 104 °C, respectively, compared to the case without the NO addition. In the tight contact mode, the soot oxidation was accelerated over the Co-Fe catalyst, resulting in 46 °C, 50 °C, and 50 °C reductions in T10, T50, and T90 compared to the loose contact mode. The comparison between real soot and model Printex-U showed that the T50 value of real soot (455 °C) was 102 °C lower than the model Printex-U soot.

Highlights on the key roles of interfaces between CeO2-based oxide and perovskite (LaMnO3/LaFeO3) in creating active oxygen species for soot oxidation

Design efficient catalyst which can activate oxygen molecules or supply active oxygen species is a key challenge for soot abatement under the much lower concentration of oxygen from gasoline vehicle exhaust. Herein, combining with the advantages of both CeO2-based oxide (CeO2–ZrO2–Y2O3–La2O3, CZ for short) and perovskite (LaMnO3 and LaFeO3) in oxygen storage/release, two hybrids catalysts, CZ-LaMnO3 (LM) and CZ-LaFeO3 (LF), with more oxygen vacancies and enhanced lattice oxygen transport at lower temperatures due to the heterointerface effects have been successfully synthesized for soot oxidation. Combining with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption (O2-TPD) and H2temperature-programmed reduction (H2-TPR), it was found that electrons transfer from Ce3+ to Fe3+ and an interfacial La diffusion from LM to CZ may have been occurred in LF-CZ and LM-CZ, respectively, which leads to the increased unsaturated sites and oxygen vacancies. More importantly, the obvious enhancement of active surface lattice oxygen transport at low temperatures due to interfacial interaction has also been demonstrated in LM-CZ, which highly promotes the soot oxidation. And consequently, 5LM-CZ (with 5 wt% content of LM) showed the highest soot conversion activity, whose T50 (50 % soot conversion temperature) (379 °C) was lower than 5LF-CZ (395 °C) and CZ (401°C) at tight contact mode in 1 %O2/N2 atmosphere, indicating that the activation of lattice oxygen at the interface plays an important role in soot oxidation. Furthermore, when further varying the content of LM in xLM-CZ (x = 5 wt%, 10 wt%, 15 wt%, 20 wt%), it was found that 10LM-CZ, whose content of LM reached the monolayer dispersion capacity of CZ, exhibited the most abundant active surface lattice oxygen species due to the optimized interface area. As a result, 10LM-CZ displayed superior activity even than pure LM in both loose and tight contact with/without NO, indicating that the composite catalyst has a wide application environment. This work has a certain guiding significance for the utilization of heterointerface effect among different components to prepare effective soot oxidation catalyst with multi-components.

Soot Combustion over Cu-Co Spinel Catalysts: The Intrinsic Effects of Precursors on Catalytic Activity.

In this work, a series of CuCo2O4-x (x = N, A and C) catalysts were synthesized using different metal salt precursors by urea hydrothermal method for catalytic soot combustion. The effect of CuCo2O4-x catalysts on soot conversion and CO2 selectivity in both loose and tight contact mode was investigated. The CuCo2O4-N catalyst exhibited outstanding catalytic activity with the characteristic temperatures (T10, T50 and T90) of 451 °C, 520 °C and 558 °C, respectively, while the CO2 selectivity reached 98.8% during the reaction. With the addition of NO, the soot combustion was further accelerated over all catalysts. Compared with the loose contact mode, the soot conversion was improved in the tight contact mode. The CuCo2O4-N catalysts showed better textural properties compared to the CuCo2O4-A and CuCo2O4-C, such as higher specific surface areas and pore volumes. The XRD results confirmed that the formation of a CuCo2O4 crystal phase in all catalysts. However, the CuO crystal phase only presented in CuCo2O4-N and CuCo2O4-A. The relative contents of Cu2+, Co3+ and Oads on the surface of CuCo2O4-x (x = N, A and C) catalysts were analyzed by XPS. The CuCo2O4-N catalyst displayed the highest relative content of Cu2+, Co3+ and Oads. The activity of catalytic soot combustion showed a good correlation with the order of the relative contents of Cu2+, Co3+ and Oads. Additionally, the CuCo2O4-N catalyst exhibited lower reduction temperature compared to the CuCo2O4-A and CuCo2O4-C. The cycle tests clarified that the copper-cobalt spinel catalyst obtained good stability. In addition, based on the Mars-van Krevelen mechanism, the process of catalytic soot combustion was described combined with the electron transfer process and the role of oxygen species over CuCo2O4 spinel catalysts.

Fe-doped porous Co3O4 nanosheets with highly efficient catalytic performance for soot oxidation

A series of CoxFe1-x-PNS materials were synthesized at room temperature through the one-pot MgO-mediated method and were then used as catalysts for soot oxidation. Of all the catalyst samples prepared, the porous Co0.8Fe0.2-PNS nanosheets exhibited the highest catalytic performance for soot oxidation under both loose and tight contact modes. The 2D nanosheets provided a larger external surface area for contact between the catalyst and soot, and the porous structure was beneficial to the adsorption and diffusion of reactant gas. It was found that Fe was successfully doped in the lattice of Co3O4, and the mechanism regarding how Fe doping enhances intrinsic activity was investigated by a series characterization and DFT calculations. The results indicated that Fe doping made it easier to form oxygen vacancies and adsorb gaseous O2, which effectively improved the catalytic activity of soot oxidation. Hence, it is believed that the synergy between the well-defined porous nanosheets morphology and the properties induced by the doping of Fe resulted in better catalytic activity. This study also provided insight into the design of 2D transition metal oxides nanosheets as catalysts for soot oxidation.

Preparation of Cerium-Bismuth Oxide Catalysts for Diesel Soot Oxidation Including Evaluation of an Automated Soot-Catalyst Contact Mode.

Cerium‐bismuth oxides have emerged as promising candidates for Diesel soot oxidation. The catalysts are synthesized via automated co‐precipitation methods. T50 values, where 50 % of soot is oxidized, and the dynamic oxygen storage capacity (OSCdyn) are used to compare the catalytic activity. The activity is measured by thermogravimetric methods. The synthesized catalysts are characterized through powder X‐ray diffraction (PXRD), Raman spectroscopy, and specific surface area (SBET) measurements. This work investigates the influence of the contact mode between soot and catalyst. The literature‐known manual contact modes “loose”, “tight”, and “wet” are compared with our developed automated contact mode, using a dual asymmetric centrifuge. The rotation speed rs and mixing time tM have been varied independently. Both factors influence the T50 value. A continuous transition from loose to tight contact mode with increasing rotation speed rs can be shown. Furthermore, the automated contact mode shows better reproducibility behavior compared to manual contact modes.

Broccoli-like CeO2 with Hierarchical/Porous Structures, and promoted oxygen vacancy as an enhanced catalyst for catalytic diesel soot elimination

• Ce-MOFs is adopted for fabricating broccoli-like CeO 2 (BCL-CeO 2 ). • BCL-CeO 2 shows a higher activity than commercial CeO 2 (com-CeO 2 ). • BCL-CeO 2 fully converts soot to CO 2 while com-CeO 2 produced CO. • The tight contact modeenables BCL-CeO 2 to exhibit a low T ig of 295 °C. • The mechanism of NO-assisted soot oxidation is examined by DRIFTS. • BCL-CeO 2 is recyclable with high catalytic activity for soot oxidation. While CeO 2 is a promising catalyst for soot elimination, it is essential to develop CeO 2 with higher contact areas, and reactivity for effective soot oxidation as catalytic soot oxidation is dominantly controlled by structures, and surficial properties of catalysts. In this study, a Ce-Metal organic frameworks (MOFs) consisting of Ce and trimesic acid (TA) is employed as the precursor as CeTA exhibits a unique broccoli-like hierachitecture which is transformed into CeO 2 with a hierarchical structure consisting of nanofibers of CeO 2 bundled together, forming a broccoli-like CeO 2 nanostructure. More importantly, these CeO 2 nanofibers in this broccoli-like CeO 2 (BCL-CeO 2 ) possesses porous structures, and also more oxygen vacancies, enabling BCL-CeO 2 to become a promising catalyst for soot oxidation. Thus, BCL-CeO 2 shows a much higher catalytic activity than commercial CeO 2 nanoparticle (com-CeO 2 ) for soot oxidation with a significantly lower ignition temperature (T ig ). More importantly, while soot oxidation by com-CeO 2 leads to production of CO together with CO 2 , BCL-CeO 2 can completely convert soot to CO 2 . The tight contact mode also enables BCL-CeO 2 to exhibit a very low T ig of 295 °C, whereas the existence of NO and H 2 O also enhances the soot oxidation by BCL-CeO 2 to reduce the T ig . The mechanism of NO-assisted soot oxidation is also examined, and validated by DRIFTS to identify the presence and transformation of nitrogen-containing intermediates. BCL-CeO 2 is also recyclable over many consecutive cycles and maintained its high catalytic activity for soot oxidation. These results demonstrate that BCL-CeO 2 is a promising and easily-prepared hierarchitectured Ce-based catalyst for soot oxidation.

Enhanced Catalytic Soot Oxidation by Ce-Based MOF-Derived Ceria Nano-Bar with Promoted Oxygen Vacancy

As CeO2 is a useful catalyst for soot elimination, it is important to develop CeO2 with higher contact areas, and reactivities for efficient soot oxidation and catalytic soot oxidation are basically controlled by structures and surface properties of catalysts. Herein, a Ce-Metal organic framework (MOFs) consisting of Ce and benzene-1,3,5-tricarboxylic acid (H3BTC) is employed as the precursor as CeBTC exhibits a unique bar-like high-aspect-ratio morphology, which is then transformed into CeO2 with a nanoscale bar-like configuration. More importantly, this CeO2 nanobar (CeONB) possesses porou, and even hollow structures, as well as more oxygen vacancies, enabling CeONB to become a promising catalyst for soot oxidation. Thus, CeONB shows a much higher catalytic activity than commercial CeO2 nanoparticle (comCeO) for soot oxidation with a significantly lower ignition temperature (Tig). Moreover, while soot oxidation by comCeO leads to production of CO together with CO2, CeONB can completely convert soot to CO2. The tight contact mode also enables CeONB to exhibit a very low Tig of 310 °C, whereas the existence of NO also enhances the soot oxidation by CeONB to reduce the Tig. The mechanism of NO-assisted soot oxidation is also examined, and validated by DRIFTS to identify the formation and transformation of nitrogen-containing intermediates. CeONB is also recyclable over many consecutive cycles and maintained its high catalytic activity for soot oxidation. These results demonstrate that CeONB is a promising and easily prepared high-aspect-ratio Ce-based catalyst for soot oxidation.

Impact of the support on the catalytic activity of Ag nanoparticles for soot combustion

This study investigates the catalytic activity for soot combustion of Ag nanoparticles dispersed on various supports showing different redox properties. Temperature programmed soot oxidation and isotopic exchange experiments were performed to assess the impact of the soot/catalyst contact, the oxygen partial pressure and the ageing toward activity. Three different contact modes have been used to clearly highlight the catalytic performances: loose, tight and supertight. Whatever the support, in both loose and tight contact modes, the catalytic performances are linked with the Ag surface concentration which was found to be high on zirconia-based catalysts and low on ceria-zirconia. The ignition of the soot combustion process occurs on Ag nanoparticles except for catalysts supported on Yttria-Stabilized Zirconia (YSZ), a pure oxygen ionic conductor, where Ag nanoparticles only promote the run-away of the reaction at higher temperatures. Catalysts based on SiO2, ZrO2 and YSZ exhibit a remarkable hydrothermal stability as performances in tight contact mode are fairly similar after the hydrothermal ageing.

Catalytic removal of soot particles over MnCo2O4 catalysts prepared by the auto-combustion method

Soot removal for exhaust gas from diesel engine has been addressed due to the more stringent legislation and environmental concerns. MnCo2O4 catalysts were systematically prepared using glucose as a fuel via the auto-combustion method and applied for soot removal. The as-prepared samples were characterized by X-ray diffraction (XRD), O2-temperature-programmed oxidation (TPO) reaction and H2-temperature-programmed reduction reaction (H2-TPR). The catalytic activities for soot combustion were evaluated by micro activity test (MAT) with a tight contact mode between soot and catalysts. Compared with catalysts prepared by the solid state method without glucose, auto-combustion method in the presence of glucose can decrease the synthetic temperature, avoiding high temperature treatment and sintering. The catalysts prepared with glucose could catalyze soot oxidation effectively and the derived values of T10, T50, and T90 were 326, 408, and 468 °C in a tight contact mode, respectively, showing a significant drop of T10, T50, and T90 by 156, 177, and 178 °C for non-catalytic reaction.

SO2 resistant soot oxidation catalysts based on orthovanadates

Metal orthovanadates based on Fe, Al and Ce were prepared by co-precipitation and their structural, morphological and reduction properties were characterized by means of XRD, BET and temperature programmed reduction (H2-TPR). Catalytic soot oxidation was carried out with thermogravimetric analysis (TGA) and temperature programmed oxidation (TPO), respectively, to study the influence of the soot-catalyst contact (tight or loose) as well as the influence of SO2 contamination on the catalyst's activity. The catalysts were compared with CeO2 as reference material. Under tight contact mode, metal orthovanadates were able to oxidize soot at 466–483°C while in loose contact mode their activity was close to that of CeO2. However, the former did not suffer an activity loss due to SO2 poisoning, which is attributed to less adsorptive interactions between SO2 and the vanadates as could be proven by FT-IR and Raman spectroscopy.

Shape Effect of MnOx-Decorated CeO2 Catalyst in Diesel Soot Oxidation

Abstract A series of MnOx-decorated CeO2 (MnCeO) catalysts with different morphologies have been prepared by the shape-controlled synthesis of single-crystalline CeO2, such as nanorod, nanoparticle, and nanocube, by a hydrothermal method followed by the deposition of MnOx phase by a simple impregnation method. Their shape-dependent physicochemical properties were investigated by means of XRD, BET, UV–vis, HRTEM, XPS, TPR and oxygen storage/release properties measurements. The MnOx/CeO2 nanorod (MnCeO-NR) showed prominent carbon soot combustion activity at lower temperature under tight contact mode with a T50 temperature of 317 °C, which is attributed to larger surface area and higher oxygen release rate, as compared with particle and cubic catalysts. MnCeO-NR also exhibited higher catalytic activity (a shift of T50 by 127 °C) in NO-assisted soot combustion under a loose contact mode. Not only the higher surface area but also the superior NO conversion ability at low temperature as well as greater NO absorption contributes to the improved catalytic activities. The MnCeO-NR further displayed high stability and satisfactory recyclability without significant loss of catalytic activity. The use of cheaper combinations without noble metals makes the MnOx/CeO2 catalyst a promising candidate to satisfy future requirements in industry.

Silver and manganese oxide catalysts supported on mesoporous ZrO2 nanofiber mats for catalytic removal of benzene and diesel soot

Mesoporous zirconia (ZrO2) nanofibers were synthesized by an electrospinning method and calcination at 600°C. Ag and Mn oxides were separately or simultaneously deposited on the ZrO2 nanofibers by impregnation methods. The structure of the ZrO2 supported nanofiber materials were examined by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Ag and Mn oxides were homogeneously deposited on the surface of ZrO2 nanofibers. Metallic Ag species and Mn2O3 were formed on the ZrO2 nanofibers when they were separately deposited, whereas the codeposition of Ag and Mn changed the oxidation state of Mn oxides on the catalyst surface. The supported catalysts were evaluated for their soot and benzene oxidation performance. The co-deposition of Ag and Mn lowered the light-off temperature for benzene oxidation. The soot oxidation performance was comparable for the Ag/ZrO2, Mn/ZrO2 and Ag-Mn/ZrO2 catalysts under tight contact mode, whereas Ag/ZrO2 exhibited the highest activity and the activity decreased with decreasing the Ag content under loose contact mode.

Activity of Highly Dispersed Co/SBA-15 Catalysts (Low Content) in Carbon Black Oxidation

Cobalt supported on mesoporous silica SBA-15 (0.75, 1.5 and 3 wt% Co) were used as catalysts for the oxidation of carbon black. Catalysts were characterized by N 2 sorption, XRD, TEM and TPR. The catalytic activity in CB oxidation was measured. It has been shown that only small cobalt domains (less than 5 nm) are present on all samples. A homogeneous dispersion was obtained for all catalysts. With increasing cobalt loading, crystalline species start to appear. Using an intermediate contact between the CB and the catalyst, the best activity is that of 0.75Co/SBA-15 catalyst where the oxidation reaches the maximum (Tmax) 68 K before the non-catalyzed reaction. On the same catalyst used in tight contact mode with CB, even if Tmax didn’t decrease for more than additional 12 K but the Ti decreases by 38K and thus starts 83 K before.

Praseodymium oxide doped with Bi for diesel soot oxidation at low temperature

Abstract Effects of dopant and promoter on oxidation activity to carbon upon Pr 6 O 11 based oxide were investigated. It was found that Pr 4.8 Bi 1.2 O 11 is highly active to carbon oxidation and oxidation of graphitic carbon occurs at 550 K at tight contact mode, which is much lower than that of the CeO 2 based conventional catalyst. Furthermore, loading of CeO 2 promoter is highly effective for decreasing the ignition temperature of Pr 4.8 Bi 1.2 O 11 to carbon oxidation. The actual diesel soot can be oxidized at temperature as low as 473 K using CeO 2 /Pr 4.8 Bi 1.2 O 11 in the presence of CO 2 and H 2 O.

Role of yttrium loading in the physico-chemical properties and soot combustion activity of ceria and ceria–zirconia catalysts

Ce 1− x Y x O 2 and Ce 0.85− x Zr 0.15Y x O 2 mixed oxides have been prepared by 1000 °C-nitrates calcination to ensure thermally stable catalysts. The physico-chemical properties of the mixed oxides have been studied by N 2 adsorption at −196 °C, XPS, XRD, Raman spectroscopy and H 2-TPR, and the catalytic activity for soot oxidation in air has been studied by TG in the loose and tight contact modes. Yttrium is accumulated at the surface of Ce 1− x Y x O 2 and Ce 0.85− x Zr 0.15Y x O 2, and this accumulation is more pronounced for the former formulation than for the latter, because the deformation of the lattice due to zirconium doping favours yttrium incorporation. Yttrium and zirconium exhibit opposite effects on the surface concentration of cerium; while zirconium promotes the formation of cerium-rich surfaces, yttrium hinders the accumulation of cerium on the surface. For experiments in tight contact between soot and catalyst, all the Ce 1− x Y x O 2 catalysts are more active than bare CeO 2, and Ce 0.99Y 0.01O 2 is the most active catalyst. The benefit of yttrium doping in catalytic activity of ceria can be related to two facts: (i) the Y 3+ surface enrichment hinders crystallite growth; (ii) the surface segregation of Y 3+ promotes oxygen vacancies creation. High yttrium loading ( x = 0.12) is less effective than low dosage ( x = 0.01) because yttrium is mainly accumulated at the surface of the particles and hinders the participation of cerium in the soot oxidation reaction, which is the active component. For the mixed oxides with formulation Ce 0.85− x Zr 0.15Y x O 2 (operating in tight contact) the effect of zirconium on the catalytic activity prevails with respect to that of yttrium. For experiments in loose contact between soot and catalyst, the catalytic activity depends on their BET surface area, and the catalysts Ce 0.85− x Zr 0.15Y x O 2 (BET = 10–13 m 2/g) are more active than the catalysts Ce 1− x Y x O 2 (BET = 2–3 m 2/g). In the loose contact mode, the yttrium doping and loading have a minor or null affect on the activity, and the stabilising effect of the BET area due to zirconium doping prevails.

Diesel soot oxidation catalyzed by Co-Ba-K catalysts: Evaluation of the performance of the catalysts

Abstract The Co-Ba-K catalysts supported on alumina ceramic substrates were prepared. All the catalysts were characterized by X-ray diffraction and thermogravimetry/differential scanning calorimetry. The catalytic activities were evaluated by a soot oxidation reaction using the temperature-programmed reaction system. The catalytic activities of Co 3 O 4 , Ba(NO 3 ) 2 , Co-Ba, and Co-Ba-K catalysts were studied, and the effect of the contact mode on the soot onset ignition temperature and soot oxidation rate was also discussed. The soot onset ignition temperature is 373 °C for Co-Ba catalysts with molar ratios of 1:2, 1:1 and 2:1, which is the same as that of pure Co 3 O 4 . The Co-Ba catalysts containing KNO 3 can greatly lower the soot onset ignition temperature value. The catalytic activity of pure Co 3 O 4 and Ba(NO 3 ) 2 is affected by catalyst–soot contact intensity. The soot onset ignition temperature is not affected by contact intensity for the catalysts with proper Co-Ba-K ratios. The soot oxidation rate is greatly accelerated when the Co-Ba-K catalysts and soot are in the tight contact mode.

Potential of Supported Copper and Potassium Oxide Catalysts in the Combustion of Carbonaceous Particles

Different oxide carriers (TiO2 and ZrO2) as supports for low amounts of Cu2+ and K+ species (2 wt % as equivalent oxide) were tested in the catalytic oxidation of carbon black. The K-Cu/oxide catalysts were shown to have a lower soot combustion temperature than K/oxide, Cu/oxide, and pure oxide carriers. The K-Cu/ZrO2 catalyst was found to be the most active; it exhibited activity in a loose contact nearly similar to that obtained in a tight contact mode. Physicochemical characterization by EPR, XPS, and TPR revealed the interaction of K+ species with Cu2+ species and the ZrO2 carrier in K-Cu/ZrO2 as well as a strongly distorted Cu2+ species on the ZrO2 surface. The potassium ions ensure promoting effects towards the contact between the carbon black and the catalyst surface. Although potassium ions were found to lower the reducibility of the cupric oxide species, the oxidation rate of carbon black increased in the presence of K/oxide and K-Cu/oxide.