CeO2 ZrO2 Al2O3 Research Articles

Improved Selectivity and Stability in Methane Dry Reforming by Atomic Layer Deposition on Ni-CeO2-ZrO2/Al2O3 Catalysts.

Ni can be used as a catalyst for dry reforming of methane (DRM), replacing more expensive and less abundant noble metal catalysts (Pt, Pd, and Rh) with little sacrifice in activity. Ni catalysts deactivate quickly under realistic DRM conditions. Rare earth oxides such as CeO2, or as CeO2-ZrO2-Al2O3 (CZA), are supports that improve both the activity and stability of Ni DRM systems due to their redox activity. However, redox-active supports can also enhance the undesired reverse water gas shift (RWGS) reaction, reducing the hydrogen selectivity. In this work, Ni on CZA was coated with an ultrathin Al2O3 overlayer using atomic layer deposition (ALD) to study the effects of the overlayer on catalyst activity, stability, and H2/CO ratio. A low-conversion screening method revealed improved DRM activity and lower coking rate upon the addition of the Al2O3 ALD overcoat, and improvements were subsequently confirmed in a high-conversion reactor at long times onstream. The overcoated samples gave an H2/CO ratio of ∼1 at high conversion, much greater than uncoated catalysts, and no evidence of deactivation. Characterization of used (but still active) catalysts using several techniques suggests that active Ni is in formal oxidation state >0, Ni-Ce-Al is most likely present as a mixed oxide at the surface, and a nominal thickness of 0.5 nm for the Al2O3 overcoat is optimal.

Synthesis of a homogeneous CeO2–ZrO2-Al2O3 composite material by a novel hydrothermal assisted precipitation method

CeO2-ZrO2-Al2O3(CZA) composites, combining the advantages of CeO2-ZrO2 (CZ) and Al2O3, are widely used in three-way catalyst as an indispensable support material. However, due to the adverse Zr-Al interaction and the different precipitation conditions for Ce3+/Ce4+ and Zr4+, the CZA prepared by conventional co-precipitation method has poor compositional homogeneity, resulting in degradation of redox properties. In this study, a homogeneous CZA composite is synthesized by a novel hydrothermal assisted precipitation method, in which the CZ-precipitates and Al-precipitates will be controlled separately. A quantitative EDX points analysis reveals that the Ce/Zr ratio in the resulting CZA material exhibits slight fluctuations between 0.72 and 0.91, which is much narrow than that from conventional precipitation method (0.38∼0.83). As a result, the resulting CZA material exhibits the better redox property, higher specific surface area, and more importantly, its supported Pd/CZA catalyst exhibit superior three-way catalytic activity, the T50 (temperature for 50% conversion) for CO, NO, C3H6 and C3H8 over which is 41 ℃, 26 ℃, 28 ℃ and 12 ℃, respectively, lower than that from conventional method.

Construct CeO2-ZrO2-Al2O3 support with relative CeO2-ZrO2-rich surface by peptization method to tame the thermal stability of Pd species in three-way catalysts

The sintering of Pd under high temperature operation conditions usually leads to serious deactivation of Pd-based TWCs. As the stronger Pd-CeO2-ZrO2(Pd-CZ) interaction in the form of Pd-O-Ce bond favors to anchor Pd species than that of Pd-Al2O3, to construct a CeO2-ZrO2-Al2O3(CZA) support with a relative CZ-rich surface is beneficial to selectively enlarger the Pd-CZ interface to maintain the excellent catalytic function of Pd/CZA TWCs. For the purpose, a facile one step peptizing method has been put forward to achieve the CZA material to stabilize Pd species. By XRD, TEM and Mapping, it could be inferred that comparing with the conventional precipitation method and peptization-precipitation method, the CZ nanoparticles could be homogeneously distributed on the network structure of porous Al2O3 by in-situ growth in the peptization method. Then the CZA with a relative CZ-rich surface could be obtained, which interacted strongly with the supported Pd species and thus stabilized the Pd species in oxidation states and smaller particle size. As a result, the Pd/CZA catalyst from peptization method exhibited the best activity for CO, NO, C3H6 and C3H8, the T90 (complete conversion temperature at 90% conversion) of which was reduced by 40 °C, 50 °C, 40 °C and 20 °C comparing with that of Pd/CZA derived from conventional precipitation method even being thermal aged at 900 ℃/3 h, respectively.

Engineering excellent Pd/CeO2-ZrO2-Al2O3 catalyst with abundant oxygen vacancies by Pr surface modification for eliminating NO and C3H8

In this work, a series of aliovalent additives M (M=La3+, Nd3+, Pr3+/4+, and Y3+) have been introduced to CeO2-ZrO2-Al2O3 (CZA) to increase the surface oxygen vacancies by surface modification according to electrical neutrality principle, in which Pr exhibited the most significant promotion effect. Then by in-situ infrared, X-ray photoelectron spectroscopy (XPS) and CO-Fourier transform infrared spectroscopy (CO-FTIR) measurements, it could be indicated that Pr/CZA with increased oxygen vacancies can establish strong electronic interactions with the supported Pd species, which stabilizes the Pd species in oxidation states and smaller particle size for achieving more active centers. Meanwhile, more monodentate nitrate/nitrite intermediates, which are highly active to be transformed by C3H8, could easily be formed on the surface of modified Pd/Pr/CZA catalyst. As a result, the Pd/Pr/CZA exhibited the best conversion efficiency of C3H8 and NO, the T90 (the light-off temperature at 90 % conversion) of which was reduced by 25 °C and 20 °C comparing with that of Pd/CZA even being thermally aged at 900 ℃ for 6 h, respectively.

Precursor effects in preparation CeO2-ZrO2-Al2O3 materials

In this work, a series of CeO2-ZrO2-Al2O3 (CZA) materials were prepared by deposition-precipitation method, among that, the Al(NO3)3.9H2O, pseudo-boehmite and Al2O3 were worked as aluminum precursor, respectively. The results of N2 adsorption-desorption, H2-TPR, TEM-mapping, XRD, and XPS show that the aluminum precursor has an impact on interaction between Al2O3 and CeO2-ZrO2 (CZ), resulting in differences in textural, structural and reduction properties of CZA materials. The CZA material from Al(NO3)3.9H2O displays superior textural properties and thermal stability due to the uniform distribution of Ce, Zr and Al. However, its reducing performance is limited own to stronger interactions among the components. On the contrary, the interaction between ZrO2 and Al2O3 is weaker when aluminum precursor is pseudo-boehmite or Al2O3, it facilitates the improvement of the reducing properties, but the obtained CZA material with a poor thermal stability due to the “mechanical-like” mixing mode between Ce-Zr and Al. Especially, the CZA deriving from pseudo-boehmite, possesses more oxygen vacancies and Oβ after aging, so it displays better redox performance.

Synergistic tuning of the phase structure of alumina and ceria-zirconia in supported palladium catalysts for enhanced methane combustion

CeO2–ZrO2–Al2O3 composite oxides supported palladium catalysts (Pd/CZA) are promising candidates for catalytic oxidation reactions. However, the efficient and stable oxidation of methane over Pd-based catalysts remains a longstanding challenge. Herein, we present a facile strategy to boost the catalytic performance of Pd/CZA through elaborately tuning the phase structure of supports. Calcining supports at relatively high temperatures (1200, 1300 °C) induced the phase transition of alumina (from γ-to α-) and the development of CeO2–ZrO2 solid solution (CZ). The weak interaction between α-Al2O3 and PdO resulted in an improved reducibility of catalysts. Meanwhile, the higher oxygen mobility originated from well-crystallized CZ phase contributed to the reoxidation of Pd to PdO, giving rise to abundant surface active Pd2+ species. Coupled with the hydrophobicity of α-Al2O3, the catalyst prepared with CZA supports calcined at 1300 °C demonstrated an excellent low-temperature activity, astounding stability and greatly enhanced water resistance towards methane combustion.

Nano-size effects of NH4Al(OH)2CO3 on construction CeO2-ZrO2-Al2O3 materials with high performance

Nanomaterials have been widely used in environmental catalysis and size dependency of these nanomaterials has always been a focus of intensive studies for technological applications. In this paper, a serials of NH4Al(OH)2CO3 (AACH) with different crystal size (6.3, 7.6, 8.8, 10.0 and 12.7 nm) was achieved through growth control by a facile hydrothermal treatment at different temperatures, after which the CeO2-ZrO2-Al2O3(CZA) materials were prepared through a deposition-precipitation method. Then the size dependencies of textural properties, thermal stability and redox properties in CZA materials were disclosed. The results indicate that the crystal size of AACH not only affected the driving force of sintering, but also played a significant role in coordinating the interaction among the multi-components. Among these materials, the AACH with moderate crystallite size of 8.8 nm facilitates to improve the thermal stability of pore structure, highly disperse CeO2-ZrO2(CZ) nanoparticles, adjust the interaction between Al2O3 and CZ, to form homogeneous CZ solid solution. Consequently, when the grain size of AACH is 8.8 nm, the resulting CZA material exhibits the largest specific surface, the lowest reduction temperature, the most active oxygen species and the best soot oxidation activity even being thermally aged at 1000 °C for 4 h compared with others.

Correlation between the morphology of NH4Al(OH)2CO3 and the properties of CeO2–ZrO2/Al2O3 material

Two distinct CeO2–ZrO2/Al2O3(CZA) materials were fabricated via deposition-precipitation method by regulating NH4Al(OH)2CO3 (AACH) morphologies in this work. Then, a correlation between the morphologies of AACH and the properties of resulting CZA materials has been concluded. As characterized, CZA2 from nanorod AACH displays stabled pore structures, thus exhibits higher surface area and pore volume (85.0 m2/g, 0.59 mL/g) with respective to CZA1 (66.5 m2/g, 0.35 mL/g) which derived from irregular AACH even being thermally aged at 1000 °C for 4h. While CZA1 from irregular AACH shows more surface vacancies and more active surface oxygen species due to its relatively stabled CZ phase structure, which is protected by the relatively stronger stabilization effect between CZ and irregular Al2O3.

The preparation of Pd/CeO2–ZrO2–Al2O3 catalyst with superior structural stability: effect of zirconia incorporation method

A series of CeO2–ZrO2–Al2O3 (CZA) supports were prepared by coprecipitation method with different mixed modes of precursors, and the corresponding Pd-only catalysts were acquired with incipient impregnation technique. Interestingly, the CZA3 prepared by mixing of Ce(NO3)3·6H2O–ZrO(CO3)2 mixed solution and ZrO(CO3)2–Al(NO3)3·9H2O mixed solution showed better structural stability; meanwhile, the relevant Pd/CZA3 presented better catalytic activity and the operation window. The characterization results displayed that Zr was introduced into Ce and Al, respectively, could enhance the moderate interaction between Pd and support and increase oxygen vacancies as well as inhibit particle growth, agglomeration and phase separation. Moreover, the Pd–O–Ce bond could be weakened for Pd/CZA3 with appropriate Zr content, which was helpful for enhancing redox activity. Combining the results of characterizations and catalytic performance, it is revealed that the Pd/CZA3 possessed the greatest application potential for (three-way catalysts) TWCs.

Designed synthesis of highly active CeO2-ZrO2-Al2O3 support materials with optimized surface property for Pd-only three-way catalysts

In this work, a series of CeO2-ZrO2-Al2O3 (CZA) support materials were prepared by co-precipitation method combing with hydrothermal treatment at different temperatures. Then their supported Pd-only three-way catalysts (TWCs) were prepared, characterized and compared with commercial Pd/CZAS catalyst. It is found that the catalytic performance of Pd-only TWCs shows a strong dependence on the surface properties rather than the bulk structures of CZA supports. Higher hydrothermal temperatures promote the self-assemble of Al2O3 into nanorods, and the formation of CeO2-ZrO2 (CZ) solid solution with larger crystal size, which widens the pore size distribution of CZA and improves the thermal stability of CZ nanoparticles with lower growth rate, respectively. However, the specific surface area, surface oxygen vacancies and surface Ce content of CZA decrease with hydrothermal temperature rising, which in return decreases the activity of the Pd/CZA catalysts. While it should also be noted that all the as prepared Pd/CZA exhibit better activity than the commercial Pd/CZAS, and the T50 (temperature for 50% conversion) for CO, NO, C3H6, C3H8 over Pd/CZA100 are 48 °C, 30 °C, 26 °C and 31 °C lower than those for Pd/CZAS, respectively. It further indicates that highly active Pd-only TWCs could be constructed by optimizing the surface properties of CZA support via hydrothermal treatment at modern temperature.

Bifunctional roles of Nd2O3 on improving the redox property of CeO2–ZrO2–Al2O3 materials

A series of Nd2O3 was introduced into CeO2–ZrO2–Al2O3(CZA) materials to improve their redox property, and then their soot oxidation activities were characterized. Although Nd2O3 incorporation obviously decreased the specific surface area, 7 wt% Nd2O3 modified CZA (fresh CZAN7) also exhibited the best activity, the temperature for 50% soot conversion (T50) over which is 25 °C lower than that over fresh CZA due to the more surface oxygen vacancies and the faster mobility of oxygen species. It indicates that redox property of CZA plays a critical role than specific surface area in determining the soot oxidation activity. Meanwhile, it is interesting that 31 °C lower of T50 is detected over the aged CZAN7 (1000 °C/4h) than its fresh counterpart (600 °C/3h). Combined with the results of Powder X-ray diffraction (XRD), High-resolution transmission electron microscope (HRTEM) and Raman, a new sight about the bifunctional roles of Nd2O3 on improving the redox property of CZA has been put forward. Nd2O3 could directly incorporate into CeO2–ZrO2 lattice to form CeO2–ZrO2-Nd2O3 solid solution. Meanwhile, it could also regulate the distribution of Zr species and promote them incorporate into CeO2–ZrO2 lattice during thermal treatment. Then CZAN7 could exhibit more surface oxygen species, increased surface oxygen vacancies and better soot oxidation activity even being thermally aged.

Designed synthesis of nanostructured Al2O3 stabilized homogeneous CeO2-ZrO2 solid solution as highly active support for Pd-only three-way catalyst

In this work, a highly active CeO2-ZrO2-Al2O3(CZA2) support material was successfully fabricated and the activity of its supported Pd-only three-way was also characterized. Pd/CZA2-a (aged catalyst) could maintain a superior activity and thermal stability, the T50 of CO, NO, C3H8 and C3H6 over which decrease by 34 °C, 32 °C, 29 °C and 28 °C than that over Pd/CZA1-a (reference catalyst). As characterized, the superior activity of Pd/CZA2 associates closely with the highly porous structure and advanced reducibility of the support material. By N2 adsorption–desorption analysis, TEM and SEM analysis, CZA2 displays large pore volume (0.66 mL/g) and wider pore radius (25.3 nm), which benefits the diffusion of reactant in emissions with high space velocity. And such larger pore volume and pore radius of CZA2, comparing to CZA1 (0.39 mL/g in pore volume, 8.6 nm in pore radius) with amorphous Al2O3 and those reported CZA materials, is associated with the morphology (nanorods and nanofibers) and stacking of primary particles. In addition, results of XRD and XPS manifest that the superior reducibility of CZA2 is associated with the homogenous CZ structure and the resulting increased surface oxygen vacancies. Then these vacancies maintain the smaller PdO crystal size and higher fraction of Pd2+ in the thermal treatment due to the increased metal-support interaction between CZA2 and Pd species. As a result, Pd/CZA2-a could keep a better three-way catalytic activity.

New Insights into the Role of Nd in CeO2–ZrO2–Al2O3 Composite and Supported Pd Catalyst

To improve the performance of CeO2–ZrO2–Al2O3 (CZA) composite, Nd was introduced and the role of Nd was deeply investigated. The characterization results revealed that introduction of appropriate amount of Nd (4 wt %) can effectively modify the textural and structural properties of CZA, in this case, Nd selectively combines with CZ and hardly interacts with Al2O3, which could incorporate into the lattice of CZ to form ternary CeO2–ZrO2–Nd2O3 (CZN) solid solution, thus more lattice defects and improved oxygen mobility are obtained. However, excessive doping amount of Nd (6–8 wt %) brings about formation of Nd0.5Ce0.5O1.75 and phase separation of CZ especially after thermal aging treatment. The XPS results demonstrate that the supported catalyst Pd/CZAN4 possesses higher surface Pd and Ce3+ concentrations compared with Pd/CZA, which consequently leads to improved reducibility and catalytic performance. Furthermore, higher thermal stability is obtained, after aging treatment, Pd/CZAN4a still exhibits enhanced reduction property along with superior three-way catalytic performance.

Influence of La precursors on structure and properties of CeO 2 -ZrO 2 -Al 2 O 3 composite oxides

Abstract Three La-doped CeO2-ZrO2-Al2O3 (CZA) composite oxide samples, namely, CZA-I, CZA-II and CZA-III, were prepared following a co-precipitation method in the presence of La2O3, La(NO3)3·6H2O and H[La(EDTA)]·16H2O precursors, respectively. When the precursor samples are sintered at 1000 °C, the as-prepared composite oxides mainly exhibit the CeO2-ZrO2 cubic fluorite phase, while the γ-Al2O3 and δ-Al2O3 phases appear when the precursor samples are subjected to sintering at 1100 and 1200 °C. CZA-III exhibits improved redox properties after high-temperature treatment compared with CZA-I and CZA-II. CZA-III presents the largest surface area of 97.46 m2/g among the three CZAs when the CZA-III precursor sample is sintered at 1000 °C. Furthermore, the corresponding oxygen storage capacity (OSC) is the largest with value of 400.27 μmol/g when CZA-III precursor sample is sintered at 1000 °C. Additionally, CZA-III exhibits the best thermal stability and the highest reduction temperature. However, by increasing the sintering temperature to 1200 °C, there is a dramatic decline in the properties of surface area and OSC. And a decrease for CZA-III in surface area by 58.94% and a decrease of the OSC value by 74.56% are observed.

CeO2–ZrO2–Al2O3 Modified by Selective Doping with SrO for Improved Pd-Only Three-Way Catalyst

Composite CeO2–ZrO2–Al2O3 (CZA) modified by selective doping with SrO was prepared by simple coprecipitation method. The characterization results reveal that the structural property of the modified sample is fundamentally different from that of undoped CZA, the doped SrO can selectively combine with Al2O3 and act as a stabilizer, meanwhile homogeneous CZ solid solution is formed which appears insusceptible to Al2O3. Consequently more lattice defects are created in CZAS, which facilitate the improvement of oxygen mobility. The UV–Vis DRS and XPS results demonstrate that after doping with SrO, the supported catalyst Pd/CZAS possesses higher surface Pd and Ce3+ concentrations, which consequently leads to improved reducibility and catalytic performance. Furthermore, the synergistic effect between CeO2–ZrO2 and SrO–Al2O3 helps improve the thermal stability of Pd/CZAS. As a result, after aging treatment, Pd/CZASa still maintains improved structural, textural, morphological and reduction properties along with enhanced three-way catalytic performance.

Designed synthesis of semi-embedded Pd over CeO2-ZrO2/Al2O3 as advanced three-way catalyst

Abstract For catalytic system consists of Pd as active component and CeO2-ZrO2/Al2O3 (CZ/A) as support, the dispersion and oxidation state of Pd species, which are crucial to the catalytic performance, are closely related to the metal-support interaction. In this work, Pd species were introduced into CZ/A system at different thermal treating stages of the support, which brought about different Pd–CZ interaction. The characterization results reveal that when CZ/A support was thermal treated at 300 °C prior to the introduction of Pd species, a special Pd/CZ/A catalyst with Pd species semi-embedded in CZ/A was acquired, which exhibits excellent thermal stability owing to the appropriate Pd–CZ interaction. During thermal aging process, encapsulation and aggregation of Pd species are effectively inhibited for Pd/CZ/A with semi-embedded structure. Thus, higher dispersion, more oxidative Pd2+ species and larger amount of oxygen vacancies are maintained after aging, which consequently lead to its superior three-way catalytic performance.

Preparation of CeO2–ZrO2–Al2O3 composite with layered structure for improved Pd-only three-way catalyst

In this study, two CeO2–ZrO2–Al2O3 composites with layered structure were prepared by sequential precipitation route (SP) and compared with that obtained from conventional coprecipitation method (CC). The structural, textural and redox properties of the Pd-supported three-way catalysts were investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, CO chemical adsorption, H2-temperature-programmed reduction and oxygen storage capacity (OSC). By adjusting the precipitation sequence of CZ and Al2O3 components, different combination styles of CZ and Al2O3 as well as different interaction between the two components are obtained, which consequently modifies the physicochemical properties, catalytic performance along with the thermal stability of the supported Pd/CeO2–ZrO2–Al2O3 catalysts. The catalysts derived from SP present comparable structural and textural thermal stability compared to that obtained from CC. From the aspects of XPS, TPR and OSC, more Ce3+ and improved redox properties are created by SP with respect to CC. In addition, the dispersion of palladium is enhanced due to the strong metal–support interaction. The catalytic performance evaluation results reveal that SP method leads to the formation of three-way catalysts with advanced catalytic activities for C3H8, CO and NO conversions especially when CZ is enriched in the outer layer.

CeO2–ZrO2–Al2O3 Ternary Oxides Synthesized via Supercritical Anti-Solvent and as a Support for Pd Catalyst for CO Oxidation

CeO2–ZrO2–Al2O3 ternary oxides as a support for CO oxidation was synthesized successfully via supercritical anti-solvent (SAS) precipitation using CO2 as the anti-solvent and methanol as the solvent. It was found that the CeO2–ZrO2–Al2O3 fabricated by SAS precipitation (CZA1) had superior resistance to sintering compared to the traditional co-precipitation method (CZA2). Meanwhile, the oxygen storage/release rate of CAZ1 was almost 1.5 times higher than that of CZA2 and the total oxygen storage capacity (OSC) of CAZ1 was almost twice as high as CZA2. The interactions between the Pd and the CeO2–ZrO2–Al2O3 support were stronger for the support synthesized by SAS precipitation. The conversion of CO oxidation of Pd/CZA1 was even better than that of Pd/CZA2, especially at high GHSV.

Effect of ethylene glycol on structure, thermal stability, oxygen storage capacity, and catalytic CO and CH4 oxidation activities of binary CeO2–Al2O3 and ternary CeO2–ZrO2–Al2O3 cryogels

Porous and homogeneous cryogels of binary ceria-alumina (CA) and ternary ceria-zirconia-alumina (CZA) were prepared from cerium nitrate, zirconium (IV) dinitrate oxide hydrate, and aluminium sec-butoxide by a one-pot sol–gel technique in an aqueous system and subsequent freeze drying, and effect of ethylene glycol (EG) used for chelation of cerium ions on structure, thermal stability, reducibility, oxygen storage capacity, and catalytic carbon monoxide and methane oxidation activities of the catalysts was investigated. EG did not significantly affect surface area, pore volume, mean pore size, and surface morphology of the catalysts after calcination and subsequent oxidative/reductive atmosphere heating at 900 °C. Whereas use of EG resulted in much finer particles of cerium oxides and ceria-zirconia solid solution for CA and CZA, respectively, distributed throughout alumina with high dispersion. X-ray diffraction (XRD) and Raman spectra suggested that while a cubic CeO2 phase was observed for CA after the oxidative heating regardless of whether or not EG was employed, finely-divided cerium oxides or crystalline CeAlO3 were respectively obtained after the reductive heating depending on whether EG was respectively used or not used. As for CZA, while a pseudo-cubic t″ phase was seen after the reductive heating regardless of whether EG was used or not, mixed phases of pseudo-cubic t″ and cubic or a cubic one were respectively observed after the oxidative heating depending on whether EG was respectively employed or not employed. The solid solubility of zirconia in ceria was improved by EG for CZA. The oxygen storage capacity and catalytic CH4 and CO oxidation activities were also enhanced by employing EG for both catalysts, which was ascribed fundamentally to the finer particles of cerium oxides and ceria-zirconia solid solution for CA and CZA, respectively, although CO oxidation on CA was unimproved by EG after the reductive heating.

Effects of H2O Addition on Oil Sand Bitumen Cracking Using a CeO2–ZrO2–Al2O3–FeOx Catalyst

The behavior of a CeO2–ZrO2–Al2O3–FeOx catalyst typically employed during heavy oil decomposition was investigated in conjunction with the addition of H2O, as a means of improving the upgrading activity and suppressing coke formation on the catalyst. The upgrading of oil sand bitumen diluted with benzene was examined with this catalyst at various FH2O/Fbitumen ratios [where FH2O is the water flow rate (g h–1) and Fbitumen is the bitumen feedstock flow rate (g h–1)] in a fixed-bed flow-type reactor. Under optimal conditions (FH2O/Fbitumen equal to approximately 20) and at a reaction temperature of 693 K, effective catalytic decomposition of the bitumen was observed with the lighter component (gas oil and vacuum gas oil) yield reaching 71 mol % C. In addition, the formation of coke on the catalyst was decreased to less than 14 mol % C. Analyses using quadrupole mass spectrometry determined that this catalyst upgrades the heavy oil through oxidation reactions, in which the lattice oxygen of the iron oxide is...