2O3 Catalyst Research Articles

Improvement of hydrogen production via aqueous phase reforming of glycerol with Ni-Co catalysts synthesized through controlled urea matrix combustion

The effect of synthesis variable control during the combustion of urea in solution to obtain a Ni-Co/γ-Al2O3 catalyst with a low metallic loads for producting hydrogen by reforming glycerol was studied. Catalysts with the same urea/metal molar ratio but synthesized by controlled or uncontrolled urea matrix combustion were compared. It has been observed that adopting a urea/metal molar ratio between 2 and 6 and a heating rate of 10 °C∙min−1 results in a catalyst with an active surface and high Ni-Co interaction. This leads to significant improvements in H2 yield (from 34 to 50%), glycerol conversion (from 35 to 50%), and H2 selectivity (from 96 to 99%), while maintaining stability during 420 min of reaction. The repeatability of controlled synthesis has shown differences in results of less than 2%. Controlled synthesis is an attractive approach for scaling up the process for treating glycerinous waters, effluents in biodiesel plants.

Impact of gallium loading and process conditions on H2 production from dry reforming of methane over Ni/ZrO2-Al2O3 catalysts

Ni stabilized over zirconia-alumina support (10Ni/10ZrAl), and further enhanced with gallium promotion, was examined for its efficacy in dry reforming of methane. 1–3 wt % gallium addition to the 10Ni/10ZrAl catalyst led to an even distribution of gallium throughout the catalyst, increased formation of NiO species that are easily reduced, and deposition of less graphitic carbon compared to an unpromoted catalyst. 10Ni2Ga/10ZrAl catalyst has least carbon deposition and highest H2 yield (26 %) at 600 °C. Process optimization is performed over best catalyst, 10Ni2Ga/10ZrAl, by varying space velocity from 30,000 cm3 g−1h−1 to 48,000 cm3g−1h−1, reaction temperature from 550 °C to 800 °C, and CH4/CO2 from 0.5 to 1. A regression model equation is set as the function of factors, and the response as H2 yield through research surface methodology under center composite design. The model predicted an optimal H2 yield of 91.95 % which is closely validated by 90.09 % H2 yield experimental at optimized conditions.

Selective oxidation of methyl glycolate to methyl glyoxylate with molecular oxygen catalyzed by VOx/γ-Al2O3

The selective oxidation of methyl glycolate (MG) to methyl glyoxylate (MGO) using molecular oxygen in a fixed-bed reactor represents a greener and more efficient alternative to the traditional batch processing for producing this important fine chemical and intermediate. Despite its potential, detailed understanding of this catalytic reaction is still limited. In our study, VOx/γ-Al2O3 catalysts were identified as effective for the reaction, but their performance strongly depended on the structure of VOx species. The optimal catalyst with nearly monolayer dispersed VOx achieved a high MG conversion of 91% and an MGO selectivity of 71%, alongside maintaining stability for 300 h without noticeable deactivation. At a low V loading of 0.6%, isolated VOx species were formed, exhibiting the highest turnover frequency (TOF) but the lowest MGO selectivity. Increasing the V loading to 3.9% resulted in a blend of less polymeric and isolated VOx species, which decreased the TOF but enhanced MGO selectivity to 59%. With the V loading ranging from 5% to 6.2%, monolayer dispersed VOx became dominant, yielding a lower TOF and the highest MGO selectivity. A further increase in V loading caused the emergence of crystalline V2O5, which seemed to act as a bystander. Moreover, the redox cycles of V4+ and V5+ over the VOx/γ-Al2O3 catalyst played an important role in the selective oxidation of MG to MGO, while the overoxidation of MG to CO2 might take place through the V3+/V4+ redox pairs, the extent of which was determined by the structure of VOx species. These insights are crucial for developing high-performance VOx-based catalysts for the production of MGO through the selective oxidation of MG.

Synergistic growth of nickel and platinum nanoparticles via exsolution and surface reaction

Bimetallic catalysts combining precious and earth-abundant metals in well designed nanoparticle architectures can enable cost efficient and stable heterogeneous catalysis. Here, we present an interaction-driven in-situ approach to engineer finely dispersed Ni decorated Pt nanoparticles (1-6 nm) on perovskite nanofibres via reduction at high temperatures (600-800 oC). Deposition of Pt (0.5 wt%) enhances the reducibility of the perovskite support and promotes the nucleation of Ni cations via metal-support interaction, thereafter the Ni species react with Pt forming alloy nanoparticles, with the combined processes yielding smaller nanoparticles that either of the contributing processes. Tuneable uniform Pt-Ni nanoparticles are produced on the perovskite surface, yielding reactivity and stability surpassing 1 wt.% Pt/γ-Al2O3 catalysts for CO oxidation. This approach heralds the possibility of in-situ fabrication of supported bimetallic nanoparticles with engineered compositional distributions and performance.

Surface basic site effect on CoLa/m-Al2O3 catalysts for dry reforming of methane

Dry reforming of methane (DRM) is a novel technology that enables the direct utilization of greenhouse gases (CH4 and CO2) for the production of value-added products. In the DRM reaction, the acid-base characteristics of the catalyst support play a pivotal role in determining the performance of the catalyst. In this study, a series of Co-based catalysts with different alkali earth metal-modified Al2O3 composite supports, specifically m-Al2O3 (m=Ca, Mg, and Ba), were prepared using the impregnation method. Various characterization techniques were employed to investigate the impact of alkaline site modulation on the support surface with respect to anti-sintering and anti-coking properties. The results demonstrate that the m-Al2O3 composite support catalysts, prepared with Mg and Ca modulation, exhibit an abundance of basic sites and oxygen vacancies. This promotes the adsorption and activation of CO2, enhances the rate of carbon elimination, and effectively addresses carbon deposition and metal sintering issues. Notably, the CoLa/Mg-Al2O3 catalyst shows the highest performance under reaction conditions of 750 °C, with CH4 and CO2 conversions reaching 92.3 % and 97.5 %, respectively. On the other hand, the CoLa/Ba-Al2O3 catalysts display poor performance in dry reforming. Kinetic studies indicate that CoLa/Mg-Al2O3 catalyst significantly reduce the apparent activation energy required for CH4 and CO2 cracking. Furthermore, it is demonstrated that the introduction of alkali earth metals can promote the dissociation of CH4 and CO2.

Highly Efficient PtSn/Al2O3 and PtSnZnCa/Al2O3 Catalysts for Ethane Dehydrogenation: Influence of Catalyst Pretreatment Atmosphere

Increased demand for ethylene has motivated direct ethane dehydrogenation over Pt-based catalysts. PtSn/γ-Al2O3 and PtSnZnCa/γ-Al2O3 catalysts were investigated with the aim of understanding the effect of the pretreatment environment on the state of dispersed Pt for ethane dehydrogenation. The catalysts were prepared by the impregnation method and pretreated in different environments like static air (SA), flowing air (FA), and nitrogen (N2) atmospheres. A comprehensive characterization of the catalysts was performed using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Temperature-Programmed Reduction (TPR), NH3 Temperature-Programmed Desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM) techniques. The results reveal that the PtSn on Al2O3 catalyst pretreated in the static air environment (PtSn-SA) exhibits 21% ethylene yield with 95% selectivity at 625 °C. XPS analysis found more platinum and tin on the catalyst surface after static air treatment. The overall acidity of the catalysts decreased after thermal treatment in static air. Elemental mapping demonstrated that Pt agglomeration was pronounced in catalysts calcined under flowing air and nitrogen. These factors are responsible for the enhanced activity of the PtSn-SA catalyst compared to the other catalysts. The addition of Zn and Ca to the PtSn catalysts increases the yield of the catalyst calcined in static air (PtSnZnCa-SA). The PtSnZnCa-SA catalyst showed the highest ethylene yield of 27% with 99% selectivity and highly stable activity at 625 °C for 10 h.

Efficient reverse water gas shift reaction at low temperatures over an iron supported catalyst under an electric field

The development of high-performance Fe-based catalysts is attractive because Fe is a cost-effective and earth-abundant element. Application of an external electric field and an appropriate catalytic support to an Fe-based catalyst enabled the reverse water–gas shift reaction to proceed with high activity, selectivity, and durability even at the low temperature of 423 K. The Fe-supported catalyst showed superior CO selectivity (≈ 100%) compared to the Co- or Ni-supported catalyst. The apparent activation energy (5.9 kJ mol−1) over the Fe/Ce0.4Al0.1Zr0.5O2 catalyst under an electric field was much lower than that without an electric field (61.4 kJ mol−1).

Al-MIL-53 metal-organic framework supported Ru catalyst for selective hydrodeoxygenation of lignin-derived phenols into cyclohexane

Catalytic hydrodeoxygenation (HDO) of guaiacol, as a bio-oil model compound, was investigated employing Ru/Al-MIL −53 Metal-Organic Framework and Ru/γ-Al2O3 catalysts under external molecular hydrogen. Notably, the HDO results attributed the remarkable potential of the Ru/Al-MIL −53 MOF toward the comparatively high conversion of guaiacol (70%) together with a high proportion of cyclohexanol (23%) at a catalyst/feed (C/F) ratio of 1:5. However, only a 30% conversion was found with only 3.5% cyclohexanol for Ru/γ-Al2O3 for the same C/F ratio. This was due to the high porosity and presence of numerous vacancies in the MOF, which directly affects the H2-dissociation/ spillover that assists the transfer of produced H-radicals for further conversion of the adsorbed guaiacol molecules. Notably, the activity of Ru/Al-MIL −53 was remarkably increased by decreasing the amount of guaiacol. The maximum conversion was achieved (100%) for a C/F ratio of 1:1, with a higher (96.2%) selectivity for cyclohexane. The reusability test for the spent catalyst did not show any significant change in catalyst performance for up to five successive cycles.

Dry Reforming of Methane over Mn-modified Ni-based Catalysts

Ni-based bi- and trimetallic Mn, Mg and aluminum containing catalysts prepared by the solution combustion synthesis (SCS) method were tested in dry reforming of methane (DRM). As a comparison 12 wt.% Ni/α-Al2O3 catalyst prepared by wet impregnation was also investigated. The catalysts were characterized by means of XRD, N2 physisorption, H2-TPR, CO2-TPD, NH3-TPD, TPO, CHNS, TGA, SEM and TEM. Formation of crystalline MnAl2O4 was observed at high temperatures during SCS. The average nickel particle size varied in the range of 12–36 nm. Addition of Mn promoted reduction of Ni and elevated the amount and strength of the basic sites.Graphical

Temperature-driven dynamic evolution process of Ag species on silver-loaded Zr0.2Sn0.8O2 catalyst for selective catalytic oxidation of ammonia

Silver-based catalysts are extensively utilized in the selective catalytic oxidation of ammonia (NH3-SCO). However, enhancing low-temperature activity often causes a decline in N2 selectivity, presenting a substantial challenge in balancing activity and N2 selectivity. In this work, we introduced zirconium into the SnO2 support, resulting in a significant enhancement of low-temperature activity by 200 °C for the Ag/Zr0.2Sn0.8O2 catalyst; yet, this also led to the formation of N2O at low temperatures and NOx at high temperatures. Characterizations such as XPS and in situ DRIFTS revealed that the dynamic changes of silver species driven by temperature had a profound impact on the reaction mechanism and guided the formation of different products. Below 200 °C, the predominance of Ag+ directed the imide mechanism, with the –HNO species being the key intermediate leading to the production of N2O. Above 300 °C, Ag0 became dominant, favoring the internal selective catalytic reduction (i-SCR) mechanism and the production of NOx. This work provides novel insights into improving N2 selectivity of Ag-based catalysts and contributes to a deeper understanding of the reaction mechanisms.

Suppression of inactive sites in NiMo@amorphous alumina catalysts for hydrodesulfurization reaction: Effect of Ga doping

Hydrodesulfurization (HDS) reaction activity depends on the formation of active NiMoS (completely sulfided multilayer type 2 sites) and inactive NiAl2O4/NixSy phases on the catalyst surface. These inactive phases not only itself inactive for the reaction but also hinder the formation of active NiMoS phases. In addition, the formation of strong Mo-O-Al bonds also lowers the reducibility of the catalyst, suggesting lesser catalytic activity (type 1 sites, partially sulfided single-layer sites). To this end, we report the formation of NiMo/Ga doped amorphous alumina (A-Al2O3) catalysts prepared by the colloidal synthesis method. A-Al2O3 was chosen as a support because it has lower surface energy, better physicochemical properties, and enhanced acidic sites than the crystalline alumina phase, which favours the formation of type 2 sites or weak metal-support interaction (completely sulfided multilayer NiMoS sites). Further, the Ga doping in A-Al2O3 support substitute the tetrahedral Al sites and form GaAl2O4 phases by reducing NiAl2O4 inactive sites, and the free Ni decorate the edges of MoS2 to form HDS active NiMoS sites. Therefore, NiMo/Ga doped A-Al2O3 catalyst (at 1 wt% Ga loading) reported enhanced HDS catalytic activity (25%), HDS reaction rate constant (kHDS-2.15 times) and turn over frequency (TOF-1.3 times) than the conventional NiMo/γ-Al2O3 catalysts.

Catalytic ozonation of reverse osmosis concentrate from coking wastewater reuse by surface oxidation over Mn-Ce/γ-Al2O3: Effluent organic matter transformation and its catalytic mechanism

Degradation of organics in high-salinity wastewater is beneficial to meeting the requirement of zero liquid discharge for coking wastewater treatment. Creating efficient and stable performance catalysts for high-salinity wastewater treatment is vital in catalytic ozonation process. Compared with ozonation alone, Mn and Ce co-doped γ-Al2O3 could remarkably enhance activities of catalytic ozonation for chemical oxygen demand (COD) removal (38.9%) of brine derived from a two-stage reverse osmosis treatment. Experimental and theoretical calculation results indicate that introducing Mn could increase the active points of catalyst surface, and introducing Ce could optimize d-band electronic structures and promote the electron transport capacity, enhancing HO• bound to the catalyst surface ([HO•]ads) generation. [HO•]ads plays key roles for degrading the intermediates and transfer them into low molecular weight organics, and further decrease COD, molecular weights and number of organics in reverse osmosis concentrate. Under the same reaction conditions, the presence of Mn/γ-Al2O3 catalyst can reduce ΔO3/ΔCOD by at least 37.6% compared to ozonation alone. Furthermore, Mn-Ce/γ-Al2O3 catalytic ozonation can reduce the ΔO3/ΔCOD from 2.6 of Mn/γ-Al2O3 catalytic ozonation to 0.9 in the case of achieving similar COD removal. Catalytic ozonation has the potential to treat reverse osmosis concentrate derived from bio-treated coking wastewater reclamation.

Highly Reactive Peroxide Species Promoted Soot Oxidation over an Ordered Macroporous Ce0.8Zr0.2O2 Integrated Catalyzed Diesel Particulate Filter.

Particulate matter, represented by soot particles, poses a significant global environmental threat, necessitating efficient control technology. Here, we innovatively designed and elaborately fabricated ordered hierarchical macroporous catalysts of Ce0.8Zr0.2O2 (OM CZO) integrated on a catalyzed diesel particulate filter (CDPF) using the self-assembly method. An oxygen-vacancy-enriched ordered macroporous Ce0.8Zr0.2O2 catalyst (VO-OM CZO) integrated CDPF was synthesized by subsequent NaBH4 reduction. The VO-OM CZO integrated CDPF exhibited a markedly enhanced soot oxidation activity compared to OM CZO and powder CZO coated CDPFs (T50: 430 vs 490 and 545 °C, respectively). The well-defined OM structure of the VO-OM CZO catalysts effectively improves the contact efficiency between soot and the catalysts. Meanwhile, oxygen vacancies trigger the formation of a large amount of highly reactive peroxide species (O22-) from molecular oxygen (O2) through electron abstraction from the three adjacent Ce3+ (3Ce3+ + Vö + O2 → 3Ce4+ + O22-), contributing to the efficient soot oxidation. This work demonstrates the fabrication of the ordered macroporous CZO integrated CDPF and reveals the importance of structure and surface engineering in soot oxidation, which sheds light on the design of highly efficient PM capture and removal devices.

Study on the effect of promotors in CO2 utilization for syngas production via dry reforming of methane over Co-MOX/TiO2-Al2O3 (MOX = La, Ce, Mg, and K) catalysts

In this study, Co-based catalysts supported over Ti-Al oxide and promoted with La, Ce, Mg, and K metals were assessed for CO2 reforming of methane reaction to produce syngas. Titania-alumina mixed oxide supports were prepared using the template-assisted-solvothermal method, and then Co and promotors were co-impregnated over the as-prepared support. Different characterizations of catalysts showed that variation in promotor metal impacts these catalysts' physical and chemical properties. The Ti-Al oxide support possessed the perfect hexagonal morphology. Potassium-promoted catalysts possessed the highest number of basic sites, whereas the La-promoted catalyst possessed the highest number of acidic sites. La promotion improved the Co dispersion, while Mg promotion enhanced the metal support integration. La-promoted catalysts are deactivated because of active metal oxidation and the generation of hard carbon. The carbon was deposited in all catalysts; however, the activity of the Mg-promoted catalyst was unaffected. The intermediate surface basicity and strong metal support interaction improved the Mg-promoted catalyst's stability. The La and Mg-promoted catalysts possessed lower apparent activation energies.

Selective Stereoretention of Carbohydrates upon C-C Cleavage Enabling D-Glyceric Acid Production with High Optical Purity over a Ag/γ-Al2O3 Catalyst.

Chiral carboxylic acid production from renewable biomass by chemocatalysis is vitally important for reducing our carbon footprint, but remains underdeveloped. We herein establish a strategy that make use of a stereogenic center of biomass to achieve a rare example of D-glyceric acid production with the highest yield (86.8 %) reported to date as well as an excellent ee value (>99 %). Unlike traditional asymmetric catalysis, chiral catalysts/additives are not required. Ample experiments combined with quantum chemical calculations established the origins of the stereogenic center and catalyst performance. The chirality at C4 in D-xylose was proved to be retained and successfully delivered to C2 in D-glyceric acid during C-C cleavage. The remarkable cooperative-roles of Ag+ and Ag0 in the constructed Ag/γ-Al2O3 catalyst are disclosed as the crucial contributors. Ag+ was responsible for low-temperature activation of D-xylose, while Ag0 facilitated the generation of active O* from O2. Ag+ and active O* cooperatively promoted the precise cleavage of the C2-C3 bond, and more importantly O* allowed the immediate fast oxidization of the D-glyceraldehyde intermediate to stabilize D-glyceric acid, thereby inhibiting the side reaction that induced racemization. This strategy makes a significant breakthrough in overcoming the limitation of poor enantioselectivity in current chemocatalytic conversion of biomass.

Interfacial Metal-Support Interaction and Catalytic Performance of Perovskite LaCrO3-Supported Ru Catalyst.

Interfacial metal-support interaction (MSI) significantly affects the dispersion of active metals on the surface of the catalyst support and impacts catalyst performance. Understanding MSI is crucial for developing highly active and stable catalysts with a low metal loading, particularly for noble metal catalysts. In this work, we synthesized LaRuxCr1-xO3 catalysts with low Ru loading (x = 0.005, 0.01, and 0.02) using the sol-gel self-combustion method. We found that all of the Ru atoms immediately above or below the metal-support interface are closely bonded to the perovskite LaCrO3 surface lattice through Ru-O bonds, enhancing the MSI via interfacial reaction and charge transfer mechanisms. We identified a variety of Ru species, including small 3D Ru nanoparticles, 2D dispersed Ru surface atoms, and even 0D Ru single atoms. These highly dispersed Ru species exhibit high activity and stability under dry reforming of methane (DRM) conditions. The LaRu0.01Cr0.99O3 catalyst with very low Ru loading (0.42 wt %) was stable over a 50 h DRM test and the carbon deposition was negligible. The CH4 and CO2 conversions at 750 °C reached 83 and 86%, respectively, approaching the theoretical thermodynamic equilibrium values.

A site distance dependence of product selectivity in n-hexane dehydrogenation over alumina-supported chromium catalyst

Although CrOx/Al2O3 has been widely applied for light alkanes dehydrogenation, there is insufficient understanding on the dehydrogenation of long-chain alkanes that no solutions to the poor selectivity to mono-olefins and high yield of aromatics. Herein, dehydrogenation of n-hexane was studied on a series of CrOx/γ-Al2O3 catalysts with different densities of Cr sites, and it finds that the dehydrogenation performance is closely related to the distance between Cr sites. With densely populated Cr sites, multiple H atoms of n-hexane are adsorbed on the CrOx/γ-Al2O3 simultaneously (i.e., multi-point adsorption), promoting the formation of n-hexadiene, n-hexatriene and the resultant benzene and/or coke. Therefore, when the Cr loading exceeds the mono-layer coverage (5 wt% Cr loadings), the selectivities to n-hexenes and benzene are kept constant (about 23 wt% and 68 wt%, respectively). While decrease of Cr content in the mono-layer regime leads to a significant decrease in both the distance between Cr sites and the number of adsorbed H atoms, resulting in improved selectivity to n-hexenes. The CrOx@γ-Al2O3 catalyst with 3.6 Cr atoms/nm2 prepared by the equilibrium adsorption method (and the complexation of CrIII and 3,5-dimethylpyridine), exhibits 89 wt% selectivity to n-hexenes (<2 wt% for benzene). This work provides theoretical guidance for the precise design and synthesis of the high-performance CrOx-based catalyst for the dehydrogenation of alkanes, especially for long-chain alkanes.

Synergistic effect of Zr and K promoters on iron-based catalysts in CO hydrogenation reaction

There is a growing demand for decreasing fossil fuel usage. That being said, we should move toward renewable and sustainable energy sources. Iron-based catalysts are usually employed in this route. In this work, an incipient impregnation process was used for preparing four γ-Al2O3 supported iron-based catalysts with different weight percents including 20Fe/5Cu/γ-Al2O3, 20Fe/5Cu/2K/γ-Al2O3, 20Fe/5Cu/3Zr/γ-Al2O3 and 20Fe/5Cu/1.5Zr/1K/γ-Al2O3 under the pressure of 20 atm, the temperature of 285 °C, H2 to CO ratio of one, and a gas hourly space velocity of 2 NL/ (h. gCat). BET, FE-SEM, XRD, H2-TPR, ICP, and TEM techniques were used to determine the characteristics of the catalysts, while gas chromatography results were used to determine CO conversion and product selectivity. Due to the synergistic effect of the two promoters, the doubly-promoted catalyst exhibited a C5+ selectivity of 64.2 %, surpassing both the Fe/Cu/γ-Al2O3 catalyst and the singly-promoted catalysts. This result highlights the enhanced performance of the doubly-promoted catalyst. Compared to the other catalysts prepared, the doubly-promoted catalyst demonstrated a higher carbon monoxide (CO) conversion rate of 67.7 % and yield of 43.5 %. Moreover, The results demonstrate the significant impact of Zr and K promoters of the synthesized Fe-based catalysts on hydrocarbon product distribution.

Magnetically separable Cd/CdS-ZnFe2O4/α-Fe2O3 Z-scheme heterostructure for boosting the photo-Fenton removal of antibiotic

The photocatalytic degradation of antibiotic pollution under visible light is significant for environmental protection. However, developing photocatalysts that exhibit strong responsiveness to visible light, along with high efficiency and stability, poses a substantial challenge. In this study, we have successfully constructed Cd/CdS-ZnFe2O4/α-Fe2O3 heterostructured photocatalysts. ZnFe2O4/α-Fe2O3 nanoparticles would grow on the surface of Cd/CdS, which forms the Z-Scheme heterostructure. The samples were characterized by structure, morphology, elemental and electrochemical analysis. The results show that the Cd/CdS-ZnFe2O4/α-Fe2O3 catalyst has reached 91.72% tetracycline degradation performance in the photo-Fenton reaction. Through the experimental results and the energy band position, the internal Z-scheme heterojunction reaction mechanism of improving photo-Fenton degradation performance was proposed. This research would contribute to advancing the rational design and synthesis of heterojunction photocatalysts for efficient antibiotic removal under visible light.

Hydrogen production by biogas reforming using Ni/MgO-Al2O3 catalysts

Hydrogen has been pointed out as a highly potential energy source for the future due to its flexibility in production and utilization. In order to obtain hydrogen sustainably, technologies that use renewable raw materials must be developed. In this context, this work proposes hydrogen production from biogas reforming. Ni/MgO-Al2O3 catalysts, containing 20 wt% of NiO and 10 wt% of MgO, were prepared by three methodologies (wet impregnation, coprecipitation, and citrate) and compared with Ni/Al2O3. The catalyst prepared by impregnation exhibited the highest Ni dispersion and basicity, with the highest activity in methane reforming with CO2 (CO2/CH4 = 1) at temperatures between 600 and 800 °C. This catalyst presented high stability during 100 h of reaction at 700 °C (92 % of CH4 conversion and 95 % of CO2 conversion), with a lower coking rate than Ni/Al2O3. Coke was predominantly graphitic for all catalysts, but the catalyst prepared by coprecipitation showed a higher proportion of amorphous coke and the lowest coking rate.