Redox cycling of CuFe2O4 supported on ZrO2 and CeO2 for two-step methane reforming/water splitting

CuFe₂O₄ supported on ZrO₂ and CeO₂ for two-step methane reforming was evaluated to determine if it could enhance the reactivity, CO selectivity and thermal stability of CuFe₂O₄. Two-step methane reforming consists of a syngas production step and a water splitting step. CuFe₂O₄ supported on ZrO₂ and CeO₂ was prepared using an aerial oxidation method. Non-isothermal methane reduction was carried out on TGA to compare the reactivity of CuFe₂O₄/ZrO₂ and CuFe₂O₄/CeO₂. In addition, a syngas production step was performed at 900 °C and water splitting was conducted at 800 °C alternatively five times to compare the methane conversion, CO selectivity, cycle ability and hydrogen production by water splitting in a fixed bed reactor. If the 1st syngas production step results are excluded due to over-oxidation, CuFe₂O₄/ZrO₂ and CuFe₂O₄/CeO₂ showed approximately 74.0–82.8% and 60.3–87.5% methane conversion, respectively, and 44.0–47.8% and 65.2–81.5% CO selectivity, respectively. Using CeO₂ and ZrO₂ as supports effectively improved the reactivity and methane conversion compared to CuFe₂O₄. CuFe₂O₄/ZrO₂ showed high methane conversion due to the high phase stability and thermal stability of ZrO₂ but the selectivity was not improved. After 5 successive cycles, the CeFeO₃ phase was found on CuFe₂O₄/CeO₂. Furthermore, methane conversion, CO selectivity and the amounts of hydrogen production of CuFe₂O4/CeO₂ increased with increasing number of cycles. Additional test up to the 11th cycle on CuFe₂O₄/CeO₂ revealed that CeO₂ is a better support that ZnO₂ in terms of the reactivity and CO selectivity.     

Hydrogen production by steam reforming of methanol in a micro-channel reactor coated with Cu/ZnO/ZrO2/Al2O3 catalyst

Hydrogen production by steam reforming of methanol is studied over Cu/Zn-based catalysts (Cu/ZnO, Cu/ZnO/Al₂O₃, Cu/ZnO/ZrO₂/Al₂O₃). Cu/Zn-based catalysts are derived from hydrotalcite-like precursors prepared by a co-precipitation method. The catalysts are characterized by N₂O chemisorption, XRD, and BET surface area measurements. ZrO₂ added to the Cu/Zn-based catalyst enhances copper dispersion on the catalyst surface. Among the catalysts tested, Cu/ZnO/ZrO₂/Al₂O₃ exhibits the highest methanol conversion and the lowest CO concentration in the outlet gas. A micro-channel reactor coated with a Cu/ZnO/ZrO₂/Al₂O₃ catalyst in the presence of an undercoated Al₂O₃ buffer layer exhibits higher methanol conversion and lower CO concentration in the outlet gas than in the absence of an undercoated Al₂O₃ buffer layer. The micro-channel reactor with a undercoated Al₂O₃ buffer layer produces large amounts of hydrogen compared with one without a buffer layer. The undercoated Al₂O₃ buffer layer enhances the adhesion between catalysts and micro-channel walls, which leads to improvement in reactor performance.     

Oxidative steam reforming of methanol over CuO/ZnO/CeO2/ZrO2/Al2O3 catalysts

The composition (CuO/ZnO/Al₂O₃ = 30/60/10) of a commercial catalyst G66B was used as a reference for designing CuO/ZnO/CeO₂/ZrO₂/Al₂O₃ catalysts for the oxidative (or combined) steam reforming of methanol (OSRM). The effects of Al₂O₃, CeO₂ and ZrO₂ on the OSRM reaction were clearly identified. CeO₂, ZrO₂ and Al₂O₃ all promoted the dispersions of CuO and ZnO in CuO/ZnO/CeO₂/ZrO₂/Al₂O₃ catalysts. Aluminum oxide lowered the reducibility of the catalyst, and weakened the OSRM reaction. Cerium oxide increased the reducibility of the catalyst, but weakened the reaction. Zirconium oxide improved the reducibility of the catalyst, and promoted the reaction. A lower CuO/ZnO ratio of the catalyst was associated with greater promotion of ZrO₂. The critical CuO/ZnO ratio for the promotion of ZrO₂ was approximately 0.75–0.8. Introducing of ZrO₂ into CuO/ZnO/Al₂O₃ also improved the stability of the catalyst. Although Al₂O₃ inhibited the OSRM reaction, a certain amount of it was required to ensure the stability and the mechanical strength of the catalysts.     

A comparative study of Ni catalysts supported on Al2O3, MgO–CaO–Al2O3 and La2O3–Al2O3 for the dry reforming of ethane

CO₂ utilization through the activation of ethane, the second largest component of natural and shale gas, to produce syngas, has garnered significant attention in recent years. This work provides a comparative study of Ni catalysts supported on alumina, alumina modified with CaO and MgO, as well as alumina modified with La₂O₃ for the reaction of dry ethane reforming. The calcined, reduced and spent catalysts were characterized employing XRD, N₂ physisorption, H₂-TPR, CO₂-TPD, TEM, XPS and TPO. The modification of the alumina support with alkaline earth oxides (MgO and CaO) and lanthanide oxides (La₂O₃), as promoters, is found to improve the dispersion of Ni, enhance the catalyst's basicity and metal-support interaction, as well as influence the nature of carbon deposition. The Ni catalyst supported on modified alumina with La₂O₃ exhibits a relatively stable syngas yield during 8 h of operation, while H₂ and CO yields decrease substantially for Ni/Al₂O₃.     

Ni/Pd-promoted Al2O3–La2O3 catalyst for hydrogen production from polyethylene terephthalate waste via steam reforming

Ni/Pd-co-promoted Al₂O₃–La₂O₃ catalysts for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR-H₂, SEM, TGA and DTA. The results showed that Ni-Pd-co-impregnated Al₂O₃–La₂O₃ catalyst has excellent activity for the production of hydrogen with a prolong stability. The feed conversion of 87% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 93.87% in the case of 10% Ni-1% Pd/Al₂O₃–La₂O₃ catalysts with an H₂ fraction of 0.60. The catalyst performance in term of H₂ selectivity and feed conversion was further investigated under various operating parameters, e.g., temperatures, feed flow rates, feed ratios and PET concentrations. It was found that the temperature has positive effects on H₂ selectivity and conversion, yet feed flow rate has the adverse effects. In addition, PET concentrations showed improved in H₂ selectivity in comparison to when only phenol as a solvent was involved. The Ni particles, which are the noble-based active species are more effective, thus offered good hydrogen production in the PET steam reforming process. Incorporation of La₂O₃ as support and Pd as a promoter to the Ni/Al₂O₃ catalyst significantly increased catalyst stability. The Ni–Pd/Al₂O₃–Al₂O₃ catalyst showed remarkable activity even after 36 h along with the production of carbon nanotubes, while H₂ selectivity and feed conversion was only slightly decreased.     

Dry reforming over mesoporous nanocrystalline 5% Ni/M-MgAl2O4 (M: CeO2, ZrO2, La2O3) catalysts

In this article mesoporous nanocrystalline 5 wt%M-95 wt%MgAl₂O₄ (M: CeO₂, ZrO₂, La₂O₃) powders were prepared by a novel on-step sol-gel process and employed as a support for the synthesis of 5 wt%Ni catalysts for synthesis gas production via dry reforming. The magnesium aluminate spinel prepared with this sol-gel method possessed a high BET area of 264 m² g⁻¹ with a high pore volume of 0.436 cm³ g⁻¹. The results indicated that the addition of promoters (CeO₂, ZrO₂, La₂O₃) to magnesium aluminate improved the BET area and pore volume and also decreased the crystallite size. Among the prepared powders and catalysts, 5 wt%La₂O₃-95 wt%MgAl₂O₄ and 5 wt%Ni/5 wt%CeO₂-95 wt%MgAl₂O₄ exhibited the highest BET area of 306 m² g⁻¹ and 263 m² g⁻¹, respectively. The catalytic results indicated that the 5 wt%Ni/5 wt%CeO₂-95 wt%MgAl₂O₄ catalyst exhibited the highest activity and the lowest carbon formation among the prepared catalysts with the same content of the promoter. The influence of the CeO₂ content on the textural and catalytic performance was also investigated and the results illustrated that the increment in CeO₂ content improved the methane conversion and reduced the amount of deposited carbon, which could be related to the redox properties of the catalyst support.     

Syngas production via dry reforming of methane over CeO2 modified Ni/Al2O3 catalysts

Syngas production via dry reforming of methane (DRM) was experimentally investigated using Ni-based catalyst. Ni/Al₂O₃ modification with CeO₂ addition and O₂ addition in the reactant were employed in this study to suppress carbon deposition and to enhance catalyst activity. It was found that DRM performance can be enhanced using CeO₂ modified Ni/Al₂O₃ catalyst due to CeAlO₃ formation. However, an optimum amount of CeO₂ loading exists to obtain the best DRM performance due to the decrease in specific surface area as the CeO₂ loading increases. Without O₂ addition, the reverse water-gas shift reaction plays an important role in DRM. It was found that CH₄ conversion and CO yield were enhanced while CO₂ conversion and H₂ yield are decreased as the CO₂ amount in feedstock increased in DRM. With O₂ addition in the fed reactant, it was found that the methane oxidation reaction plays an important role in DRM. CH₄ conversion can be enhanced by O₂ addition. However, decreases in CO₂ conversion and H₂ and CO yields occurred due to greater H₂O and CO₂ productions from the methane oxidation reaction. The thermogravimetric analysis (TGA) results showed that CeO₂ modified Ni/Al₂O₃ catalyst would have the lowest amount of carbon deposition when O₂ is introduced into the reaction.     

Hydrogen production from steam reforming of methanol over Cu-based catalysts: The behavior of ZnxLaxAl1-xO4 and ZnO/La2O3/Al2O3 lined on cordierite monolith reactors

The effect of ceramic support on the performance of methanol reforming process catalysts was studied by synthesizing Cu/Zn_1.11La_1.26Al_0.5O_4.27 and comparing it with optimized, conventional γAl₂O₃ based catalyst in a monolithic reactor. The physicochemical properties of the synthetic catalysts were studied using BET, FESEM, FTIR, XRD, TGA, TPR, TEM and XPS analyses for better evaluation of their catalytic performance. The results showed that the sponge like ceramic support Cu/Zn_1.11La_1.26Al_0.5O_4.27 catalyst is very highly efficient and active, has a lower reduction temperature and possess better pore size and pore volume compared with γ-Al₂O₃ based catalysts. Comparison of Cu/γAl₂O_3, Cu/La-γAl₂O_3, Cu-Zn/La-γAl₂O₃ and Cu-Zn/γAl₂O₃ catalysts shows that the presence of Zn undesirably affects methanol conversion at higher temperatures while positively affecting the conversion at lower temperatures. Unlike Zn, La functions better at higher temperatures with respect to conversion and selectivity to H_2. Therefore, Cu-Zn/La-γAl₂O₃ catalyst function better works uniformly at all temperatures. The conversion and selectivity to H₂ of the new Cu/Zn_1.11La_1.26Al_0.5O_4.27 catalyst (97% and 91% respectively) are greater than the alumina supported catalysts such as Cu-Zn/La-γAl₂O₃ (90% and 73% respectively)_. The obtained results show that in this process, the designed Monolith/Zn_1.11La_1.26Al_0.5O_4.27 structure has a remarkable impact on methanol conversion and carbon monoxide selectivity.     

Impact of Ce-Loading on Ni-catalyst supported over La2O3+ZrO2 in methane reforming with CO2

This paper investigated the effect of doping Ni supported catalysts with different ceria loading. The catalysts (5%Ni+x%Ce/La₂O₃+ZrO₂, where x = 0, 1, 2, 2.5, 3, 5) were synthesized via the wet impregnation technique and tested for methane reforming with carbon dioxide at atmospheric pressure, 700 °C and 42, 000 ml/g_cat.h gas hourly space velocity. The fresh catalysts were subjected to different characterization techniques such as X-ray diffraction, Surface area and pore analysis, H₂-temperature programmed reduction, CO₂-temperature programmed desorption and thermogravimetric analysis (TGA). A fine correlation between characterization results and catalytic activity is found. The results of the reactions indicated that 5%Ni/La₂O₃+ZrO₂ has the lowest conversion which increased with the percentage loading of CeO₂ up to 2.5 wt % and then began to decline. This suggests that 2.5 wt % loading is the optimum for CH₄ and CO₂ conversion. This particular catalyst composition has NiO species that could be reduced easily, as well as dense and wide distribution of all type of basic sites with respect to other catalyst system. The used catalysts were again subjected to TGA and RAMAN analysis where the least carbon deposition and the least deactivation factor was observed for 5%Ni+5%Ce/La₂O₃+ZrO₂ catalysts.     

Study on water–gas shift reaction performance using Pt-based catalysts at high temperatures

The water–gas shift reaction (WGSR) performance was experimentally studied using Pt-based catalysts for temperature, time factor and steam to carbon (S/C) molar ratio at ranges of 750–850 °C, 10–20 g_cat h/mol_CO, and 1–5, respectively. Al₂O₃ spheres were used as the catalyst support. For the high S/C cases, it was found that CO conversion can be enhanced when Pt/CeO₂/Al₂O₃ catalyst was used as compared with Pt/Al₂O₃. For the low S/C ratio cases, CO conversion enhancement was not significant with the addition of CeO₂. It was also found that CO conversion was not influenced by the CeO₂ amount to a large extent. Using bimetallic Pt–Ni/CeO₂/Al₂O₃ catalyst, it was found that higher CO conversion can be obtained as compared with CO conversions obtained from monometallic catalysts (Pt/Al₂O₃ or Pt/CeO₂/Al₂O₃). The experimental data also indicated that good thermal stability can be obtained for the Pt-based catalysts studied.     

One-step growth of CuO/ZnO/CeO2/ZrO2 nanoflowers catalyst by hydrothermal method on Al2O3 support for methanol steam reforming in a microreactor

CuO/ZnO/CeO₂/ZrO₂ nanoflowers catalyst was grown on an Al₂O₃ foam ceramic by a one-step hydrothermal process, while a naked Al₂O₃ foam ceramic and an Al₂O₃ foam ceramic grown with ZnO nanorods that directly impregnated into the catalyst precursor solution were also fabricated simultaneously. The morphology, composition, redox property and specific surface area of catalysts on the three ceramics were investigated in detail. The catalyst-loaded ceramics were used as catalyst supports in a microreactor to study the catalytic performance for methanol steam reforming. Results showed that the microreactor with Al₂O₃ support grown with nanoflowers catalyst achieved 99.8% methanol conversion rate, 0.16 mol/h H₂ flow rate at 310 °C, and an inlet methanol flow rate of 0.048 mol/h. Moreover, the microreactor exhibited 92% methanol conversion rate after 30 h continuous reaction.     

Mesoporous catalysts for dry reforming of methane: Correlation between structure and deactivation behaviour of Ni-containing catalysts

Mesoporous alumina doped with CeO₂, MgO, ZrO₂ or La₂O₃ demonstrated that the solid structure influences on the deactivation behaviour of the catalysts in dry reforming of methane. Ni-containing phases such as CeO₂–Al₂O₃, CeAlO₃, MgAl₂O₄, NiAl₂O₄, ZrO₂–Al₂O₃ and La₂O₃–Al₂O₃ were formed, but did not impede coking on the solids. Only nickel species on a high surface area MgAl₂O₄ or NiAl₂O₄ exhibited elevated resistance to physical degradation and enhanced promoting effect to labile carbon formation. In this solid, the NiO nanoparticles included between the MgAl₂O₄ and NiAl₂O₄ layer were almost certainly accessible to methane and carbon dioxide molecules and the source supporting for the formation of such amorphous reactive carbon, graphite and carbon nanotubes, as well.     

Aqueous-phase reforming of n-BuOH over Ni/Al2O3 and Ni/CeO2 catalysts

The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al₂O₃ and CeO₂ catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al₂O₃ catalyst showed significant deactivation compared to the Ni/CeO₂ catalyst, both in terms of production rates and the selectivity to H₂ and CO₂. The Ni/CeO₂ catalyst demonstrated higher selectivity for H₂ and CO₂, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al₂O₃ sample. For the Ni/Al₂O₃ catalyst, the selectivity to CO increased with temperature, while the Ni/CeO₂ catalyst produced no CO. For the Ni/CeO₂ catalyst, the activation energies for H₂ and CO₂ production were 146 and 169 kJ mol⁻¹, while for the Ni/Al₂O₃ catalyst these activation energies were 158 and 175 kJ mol⁻¹, respectively. The difference of the active metal dispersion on Al₂O₃ and CeO₂ supports, as measured from H₂-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al₂O₃ catalyst. It is unlikely that carbon would build up on the Ni/CeO₂ catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO₂ lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO₂ mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO₂ with H₂.     

Behavior of nickel catalysts in supercritical water gasification of glucose: Influence of support

The catalytic performance of Ni-based supercritical water gasification (SCWG) catalysts may be influenced strongly by the nature of support. In this paper, Ni catalysts with the different supports (CeO₂/Al₂O₃, La₂O₃/Al₂O₃, MgO/Al₂O₃, ZrO₂/Al₂O₃) were prepared by two-step impregnation method. The fresh and used catalysts were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy with an Energy Dispersive X-ray (SEM-EDX), Brunauer–Emmett–Teller (BET) specific surface area measurements, X-ray photoelectron spectroscopy (XPS) and Thermo-gravimetric analyses (TGA). The catalyst performance testing was conducted by SCWG of glucose at 673 K and 23.5 MPa with an autoclave reactor, to evaluate the influence of support on the hydrogen production. The results showed that H₂ yield for different supports decreased in order: CeO₂/Al₂O₃ > La₂O₃/Al₂O₃ > MgO/Al₂O₃ > Al₂O₃ > ZrO₂/Al₂O₃, and H₂ selectivity decreased in order: CeO₂/Al₂O₃ > La₂O₃/Al₂O₃ > ZrO₂/Al₂O₃ > Al₂O₃ > MgO/Al₂O₃. Ni catalysts were deactivated in SCWG reaction because of sintering and coke deposition. Compared with other supports, CeO₂ can be used as the promoter of carbon removal from catalyst surfaces.     

Oxidative steam reforming of ethanol over Ni/Al2O3 catalysts promoted by CeO2, ZrO2 and CeO2–ZrO2

Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al₂O₃ supports that were either unpromoted or promoted with CeO₂, ZrO₂ and CeO₂–ZrO₂. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO₂ and/or ZrO₂ showed that the variations induced in the Al₂O₃ by the addition of CeO₂ and/or ZrO₂ alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO₂–ZrO₂, improved catalytic activity by increasing the H₂ yield and the CO₂/CO and the H₂/CO values while decreasing coke formation. This results from the addition of ZrO₂ into CeO₂. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products.     

Mechanistic aspects of the low temperature steam reforming of ethanol over supported Pt catalysts

The influence of the support of Pt catalysts for the reaction of steam reforming of ethanol at low temperatures has been investigated on Al₂O₃, ZrO₂ and CeO₂. It was found that the conversion of ethanol is significantly higher when Pt is dispersed on Al₂O₃ or ZrO₂, compared to CeO₂. Selectivity toward H₂ is higher over ZrO₂-supported catalyst, which is also able to decrease CO production via the water-gas shift reaction. Depending on catalyst employed, interaction of the reaction mixture with the catalyst surface results in the development of a variety of bands attributed to ethoxy, acetate and formate/carbonate species associated with the support, as well as by bands attributed to carbonyl species adsorbed on platinum sites. The oxidation state of Pt seems to affect catalytic activity, which was found to decrease with increasing the population of adsorbed CO species on partially oxidized (Pt^δ+) sites. Evidence is provided that the main reaction pathway ethanol dehydrogenation, through the formation of surface ethoxy species and subsequently acetaldehyde, which is decomposed toward methane, hydrogen and carbon oxides. The population of adsorbed surface species, as well as product distribution in the gas phase varies significantly depending on catalyst reactivity towards the WGS reaction.     

Effects of synthesis route on the performance of mesoporous ceria-alumina and ceria-zirconia-alumina supported nickel catalysts in steam and autothermal reforming of diesel

Decline in catalyst performance due to coke deposition is the main problem in diesel steam (SR) and autothermal reforming (ATR) reactions. Good redox potential and strong interaction of CeO₂ with nickel increase activity and coke resistivity of Ni/Al₂O₃ catalysts. In this study, mesoporous Al₂O₃, CeO₂/Al₂O₃, and CeO₂/ZrO₂/Al₂O₃ supported nickel catalysts were successfully synthesized. The highest hydrogen yield, 97.7%, and almost no coke deposition were observed with CeO₂/ZrO₂/Al₂O₃ catalyst (Ni@8CeO₂-2ZrO₂-Al₂O₃-EISA) in SR reaction. The second highest hydrogen yield, 91.4%, was obtained with CeO₂/Al₂O₃ catalyst (Ni@10CeO₂-Al₂O₃-EISA) with 0.3 wt% coke deposition. Presence of ZrO₂ prevented the transformation of cubic CeO₂ into CeAlO₃, which enhanced water gas shift reaction (WGSR) activity. Ni@10CeO₂-Al₂O₃-EISA did not show any decline in activity in a long-term performance test. Higher CeO₂ incorporation (20 wt%) caused lower steam reforming activity. Change of synthesis route from one-pot to impregnation for the CeO₂ incorporation decreased the number of acid sites, limiting cracking reactions and causing a significant drop in hydrogen production.     

Catalytic steam reforming of complex gasified biomass tar model toward hydrogen over dolomite promoted nickel catalysts

The complex mixture of gasified tar model (phenol, toluene, naphthalene, and pyrene) was steam reformed for hydrogen production over 10 wt% nickel based catalysts. The catalysts were prepared by co-impregnation method with dolomite promoter and various oxide supports (Al₂O₃, La₂O₃, CeO₂, and ZrO₂). Steam reforming was carried out at 700 °C at atmospheric pressure with steam to carbon molar ratio of 1 and gas hourly space velocity of 20 L/h·g_cat. The catalysts were characterised for reducibility, basicity, crystalline, and total surface area properties. Dolomite promoter strengthened the metal-support interaction and basicity of catalyst. The Ni/dolomite/La₂O₃ (NiDLa) catalyst with mesoporous structure (26.42mn), high reducibility (104.42%), and strong basicity (5.56 mmol/g) showed superior catalytic performance in terms of carbon conversion to gas (77.7%), H₂ yield (66.2%) and H₂/CO molar ratio (1.6). In addition, the lowest amount of filamentous coke was deposited on the spent NiDLa after 5 h.     

Biohydrogen synthesis from catalytic steam gasification of furniture waste using nickel catalysts supported on modified CeO2

Present study evaluated the catalytic steam gasification of furniture waste to enhance the biohydrogen production. To do this, 10 wt% nickel loaded catalysts on the variety of supports (Al₂O₃, CeO₂, CeO₂-La₂O₃, and CeO₂–ZrO₂) were prepared by the novel solvent deficient method. The hydrogen selectivity (vol%) order of the catalysts was achieved as Ni/CeO₂–ZrO₂>Ni/CeO₂>Ni/Al₂O₃?Ni/CeO₂-La₂O₃. The best catalytic activity of Ni/CeO₂–ZrO₂ catalyst (~82 vol % H₂ at 800 °C) was ascribed to the smaller size of nickel crystals, finely dispersed Ni on the catalyst surface, and Ce_1-xZr_xO_2-δ solid solution. The role of Ce_1-xZr_xO_2-δ solid solution in Ni/CeO₂–ZrO₂ catalyst was observed as bi-functional; acceleration of water-gas-shift and oxidation of carbon reaction. The high resistance of Ni/CeO₂–ZrO₂ towards the coke formation showed its potential to establish a cost-effective commercial-scale biomass steam gasification process. This study is expected to provide a promising solution for the disposal of furniture wastes for production of clean energy (biohydrogen).     

Hydrogen purification for fuel cell using CuO/CeO2-Al2O3 catalyst

CuO/CeO₂, CuO/Al₂O₃ and CuO/CeO₂-Al₂O₃ catalysts, with CuO loading varying from 1 to 5 wt.%, were prepared by the citrate method and applied to the preferential oxidation of carbon monoxide in a reaction medium containing large amounts of hydrogen (PROX-CO). The compounds were characterized ex situ by X-ray diffraction, specific surface area measurements, temperature-programmed reduction and temperature-programmed reduction of oxidized surfaces; XANES-PROX in situ experiments were also carried out to study the copper oxidation state under PROX-CO conditions. These analyses showed that in the reaction medium the Cu⁰ is present as dispersed particles. On the ceria, these metallic particles are smaller and more finely dispersed, resulting in a stronger metal-support interaction than in CuO/Al₂O₃ or CuO/CeO₂-Al₂O₃ catalysts, providing higher PROX-CO activity and better selectivity in the conversion of CO to CO₂ despite the greater BET area presented by samples supported on alumina. It is also shown that the lower CuO content, the higher metal dispersion and consequently the catalytic activity. The redox properties of the ceria support also contributed to catalytic performance.