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Abstract: The preparation of three different types of mixed nickel oxides is described. These systems include: (i) the perovskite LaNiO3 oxide, (ii) a mixed-oxide derived from a hydrotalcite Ni–Al (64:38) precursor, and (iii) the spinel-type NiAl2O4 oxide. These systems were prepared with the aim of studying the activation procedure that develops small nickel nanoparticles deposited on a La2O3 or Al2O3 substrate active in H2 production through catalytic decomposition of CH4. Different preparation procedures have been applied to each precursors (i)–(iii). Perovskite-type oxide LaNiO3 was prepared by the sol–gel methodology (citrates method). Mixed oxide derived from hydrotalcite was obtained by co-precipitation using urea as a basic agent. NiAl2O4 spinel synthesis was performed by the ceramic method. The three oxide-type materials were characterized by XRD, BET specific area, TPR and XPS. Characterization results showed that the preparation methods used allow formation of highly crystalline and homogeneous oxide precursors. After activation, the oxide precursors showed a high activity in the decomposition reaction of CH4. The catalysts derived from hydrotalcite mixed oxide showed the highest activity with CH4 conversions reaching 50% at 500°C. [Copyright &y& Elsevier]

Abstract: A very strong promotion effect of the presence of 1000ppmV C3H8 in the reaction feed on CH4–O2 reaction was found over unsulfated 1%Pt/γ-Al2O3 catalyst. This promotion was further increased on pre-sulfated 1%Pt/γ-Al2O3. The promoting effect of pre-sulfation on the activity of 1%Pt/γ-Al2O3 for propane combustion results in a further improvement on methane combustion due to propane combustion heat which is generated at lower temperatures, activating methane combustion over pre-sulfated 1%Pt/γ-Al2O3 at even lower temperatures relative to unsulfated 1%Pt/γ-Al2O3. These results suggest that small amounts of propane in the gas feed during CH4–O2 reaction over a pre-sulfated Pt/γ-Al2O3 catalyst may eliminate methane emissions at low temperatures from lean-burn NGV exhausts without being deactivated by sulfur poisoning as Pd supported catalysts. [Copyright &y& Elsevier]

The effect of platinum incorporated into Co-ferrierite catalyst on the selective catalytic reduction of NOx with CH4 was studied by means of in situ DRIFTS technique. NO adsorption on Co- and PtCo-ferrierite catalysts gave dinitrosyl and mononitrosyl species on Co2+ ions. The adsorption of NO + O2 on Co-ferrierite yielded NO2 (NO+) species and also nitrites and nitrates. Similar species were observed on PtCo-ferrierite, although chemisorbed NO2 was much more stable since it persisted at reaction temperatures as high as 723 K. The spectra of the pre-reduced bimetallic PtCo-ferrierite catalyst exposed to the CH4 + NO + O2 reaction mixture showed bands at 2200–2100 cm-1, which were similar to results for a Pt-free sample but slightly more intense. In addition, strong bands of nitrate, almost unchanged with temperature, were observed. A very stable Co2+–NO2 intermediate species was developed upon incorporation of Pt into the base Co-ferrierite catalyst. [ABSTRACT FROM AUTHOR]

Abstract: The CO x -free hydrogen production by decomposition of methane was carried out over metal-free carbons and bulk and supported metal catalysts. Catalysts based on Ni or Fe (oxides, spinels and ex-hydrotalcite mixed oxides) and carbon-catalysts of different types (carbon black, activated carbon, carbon nanotubes and graphite) have been used and the performance of both different kinds of catalyst compared in the target reaction, focussing the comparative study on the initial activity and the resistance against deactivation. Catalytic results showed that activity of carbon catalysts is similar to that of the non-prereduced metal catalysts. Carbon blacks, and specifically vulcan-type, were found to be most resistant catalysts against deactivation, while the most active ones were nickel catalysts derived from hydrotalcite-like precursors (ex-LDH). It was also shown that pre-reduction treatment of nickel precursor to generate the metallic Ni0 phase before the reaction decreases the threshold temperature to generate hydrogen by about 200°C. Along the course of the reaction, nanotubes and nanofibers are formed on the surface of metal catalysts. These carbon structures encapsulate metal particles and deactivate the catalysts. However, when carbons are used as catalysts, the nature of carbon deposits depends largely on the type of carbon material employed as catalyst in the methane decomposition. Thus, the use of carbon blacks and graphite yielded amorphous turbostratic carbon, whereas activated carbons mainly produced carbon, which showed the carbon black structure. Finally, the carbon by-product of the reaction, when carbon nanotubes were used bas catalysts, accumulates in the form of extra layers over the walls of carbon nanotubes thus increasing their wall thickness. [Copyright &y& Elsevier]

Abstract: A wide variety of carbon materials (ordered mesoporous carbons, carbon blacks, activated carbon, carbon nanotubes, coke and graphite) have been investigated as catalysts for hydrogen production by methane decomposition, with the aims of identifying the carbon properties which control in a greater extension the catalytic activity and determine the nature of the active sites involved in the reaction. The catalytic activity of the different carbon materials was determined and compared using temperature-programmed experiments in a thermobalance. The initial activity was followed through the threshold temperature, defined as the temperature at which hydrogen production starts being detected, whereas the average reaction rate was also calculated and compared. The lowest threshold temperature was observed with ordered mesoporous carbons (CMK materials), followed by activated carbon and carbon blacks. On the other hand, at long reaction times activated carbon was quickly deactivated yielding a relatively low average reaction rate. The deactivation process seems to be greatly linked to the presence of micropores while the long-term activity is retained in those materials with ordered mesoporosity (CMKs) or formed by nanoparticles (carbon blacks), which make them more resistant to deactivation by the formation of carbonaceous deposits. Whereas no clear dependence is observed between the threshold temperature and the surface area neither with the presence of polar groups in the carbon catalysts, characterization of these materials by XPS shows that a direct relationship exists with the amount of defects present on the graphene layers. This fact strongly supports that these defects are the main active sites for methane decomposition over carbon catalysts. [Copyright &y& Elsevier]

Abstract: The catalytic oxidation of methane was studied over calcined and reduced Pt–Pd/γ-Al2O3 catalysts, in the presence and the absence of SO2 in the CH4–O2 reaction feed. The effect of sulfation (SO2 +O2 for 4h at 500°C) was also studied on the catalyst resistance to deactivation by sulfur poisoning. Sulfating the calcined Pt–Pd/γ-Al2O3 catalysts resulted in a strong deactivation for the CH4–O2 reaction. However, the catalytic activity of the reduced-sulfated Pt–Pd/γ-Al2O3 catalyst for CH4–O2 reaction remained rather unaffected in the presence and in the absence of SO2 in the reaction feed. XPS analysis revealed, over reduced-sulfated Pt–Pd/γ-Al2O3 catalysts, the presence of Pt(0) metallic surface species on which SO2 interactions may be faster related to Pd surface species. The presence of Pt(0) may be necessary to prevent the interactions between SO2 and Pd surface species. Long time catalytic tests showed that the activity of a reduced Pt–Pd/γ-Al2O3 catalysts for CH4–O2 reactions remained rather unaffected despite the presence of SO2 in the reaction feed. [Copyright &y& Elsevier]

Abstract: Nickel–lanthanum (LaNiO3) and nickel–rhodium–lanthanum (LaNi0.95Rh0.05O3) perovskite-type oxide precursors were synthesized by different methodologies (co-precipitation, sol–gel and impregnation). They were reduced in an H2 atmosphere to produce nickel and rhodium nanoparticles on the La2O3 substrate. All samples were tested in the catalytic decomposition of CH4. Methane decomposed into carbon and H2 at reaction temperatures as low as 450°C—no other reaction products were observed. Conversions were in the range of 14–28%, and LaNi0.95Rh0.05O3 synthesized by co-precipitation was the most active catalyst. All catalysts maintained sustained activity even after massive carbon deposition indicating that these deposits are of the nanotube-type, as confirmed by transmission electron microscopy (TEM). The reaction seems to occur in a way that a nickel or rhodium crystal face is always clean enough to expose sufficient active sites to make the catalytic process continue. The samples were subjected to a reduction–oxidation–reduction cycle and in situ analyses confirmed the stability of the perovskite structure. All diffraction patterns showed a phase change around 400°C, due to reduction of LaNiO3 to an intermediate La2Ni2O5 structure. When the reduction temperatures reach 600°C, this structure collapses through the formation of Ni0 crystallites deposited on the La2O3. Under oxidative conditions, the perovskite system is recomposed with nickel re-entering the LaNiO3 framework structure accounting for the regenerative capability of these solids. [Copyright &y& Elsevier]

Oxygen-enriched boron carbonitrides – known as boron carbon oxinitrides, BCNOs – have exhibited remarkable properties with numerous works reporting on their performance as phosphors and some few ones as H 2 -adsorbents. However, the study of BCNOs capability for CO 2 uptaking has yet to be achieved. Herein, we have designed a simple process for preparation of freestanding three-dimensional (3D) BCNO structures via pyrolysis of supramolecular gels formed by H-bonding of melamine, boric acid and glucose. The 3D porous materials obtained by pyrolysis of supramolecular gels containing glucose exhibited a seaweed-like 3D structure formed by BCNO nanocrystals embedded within a carbonaceous matrix with a certain content of amorphous hydrogenated carbon. The particularly narrow porosities exhibited by these samples proved effective for CO 2 adsorption with uptakes of up to ca. 1.8 mmol/g at 25 °C. More interestingly, those samples prepared with high concentration of glucose behaved as molecular sieves and exhibited an excellent performance for CO 2 –CH 4 separation, especially at low pressures with k H values of up to 1.04∙10 3 . [ABSTRACT FROM AUTHOR]

A catalytic comparative study of CO x -free hydrogen production by methane decomposition was carried out. Catalytic performances of bulk Ni-mixed oxides derived from Ni/Mg/Al-hydrotalcites ( ex -HTs-Ni) were compared with those obtained with Ni supported on mixed oxides derived from Mg/Al-hydrotalcites (Ni/ ex -HTs), or on commercial supports (γ-Al 2 O 3 , MgO and MgO-modified γ-Al 2 O 3 ). Catalyst characterization and their catalytic performance showed both ex -HTs-Ni and Ni/ ex -HTs appear to be a similar regardless of their method of preparation. Ni/γ-Al 2 O 3 was the best supported catalyst, although the catalytic performances of the ex -HTs catalysts were better. Higher Ni Mg interaction in ex -HTs provides higher resistance to deactivation. Characterization by TG, Raman spectroscopy and TEM of spent catalysts in the reaction suggest the degree of ordering of the graphitic layers of the carbon deposit onto the catalyst surface is the key factor in the catalyst deactivation. The higher degree of ordering or graphitization of the carbon produced with the higher concentration of sp2 carbons on the surface of the Ni/γ-Al 2 O 3 favours its faster deactivation by Ni-coverage than the bulk catalyst ( ex -HT-Ni), in which the MWNT type carbon is mainly obtained. [ABSTRACT FROM AUTHOR]

Hydrogen production free of CO and CO 2 was carried out by methane decomposition process using Ni-mixed oxides from hydrotalcite like-materials ( ex -HTs) as catalysts. The chemical composition was changed in order to evaluate the influence of the Ni-loading on the main physicochemical (ICP-AES, XRD, XPS, TPR, adsorption/desorption of N 2 at 77 K and CO 2 -TPD) properties and on the catalytic performance. For all Ni-loadings (from 7.5 to 58 atomic%), the hydrotalcite structure was the only precursor. After calcination at 850 °C, different mixed oxides were formed as a function of Ni-loading, although Ni-Mg-Al mixed oxide matrix or non-stoichiometric spinel phase was the main phase for all catalysts, with the exception of the 58 Ni atomic% sample, in which the NiO segregated from the Mg-Al matrix was the main phase. Methane conversion close to 55% was achieved, hydrogen was the only gaseous product. The most active catalyst was that containing 46% Ni at. Transmission Electron Microscopy (TEM) images of the spent catalysts showed the appearance of multiwall carbon nanotubes (MWCNTs) although under severe reaction conditions, e.g. high temperatures for thermo-programmed temperature experiments, and the long reaction times for isothermal experiments produced low quality MWCNTs. [ABSTRACT FROM AUTHOR]

Two series of sulfated zirconia-ceria based catalysts have been prepared by coprecipitation of the Zr 4+ and Ce 3+ salts, which were then sulfated by impregnation using H 2 SO 4 and [(NH 4 ) 2 S 2 O 8 ] and calcined at 650 °C for 4 h. The sulfated and persulfated Zr-Ce-O samples were synthesized with Zr/Ce ratios ranging from 1 to 15. The textural, structural and surface characteristics of the resulting modified catalysts were determined by N 2 adsorption-desorption, XRD, XPS spectroscopy and TPD of NH 3 , and results were related to their catalytic behaviour. The catalysts were tested in the direct conversion of methane at high temperature (650 °C) under fuel-rich conditions to obtain C 1 oxygenates (CH 3 OH and HCHO). Experiments were conducted using low O 2 /CH 4 ratio mixtures and high space velocity. It was shown that O 2 /CH 4 feeds resulted in practically total combustion of CH 4 when sulfated/persulfated ceria-zirconia catalysts are used, while the nature of the different phases modifies the surface acidity, which plays a crucial role on the extent of deep oxidation reactions. [ABSTRACT FROM AUTHOR]

NiPd/Ce 0.5 Zr 0.5 O 2 /Al 2 O 3 and NiPd/La 2 O 3 /Ce 0.5 Zr 0.5 O 2 /Al 2 O 3 catalysts were prepared by incipient wetness co-impregnation method or sequential impregnation method for autothermal reforming of methane (ATR of CH 4 ). The influence of the preparation mode, Ce 0.5 Zr 0.5 O 2 and La 2 O 3 additives on the physicochemical properties of NiPd supported catalysts and the effect on their activity to produce hydrogen by ATR of CH 4 were investigated. Characterization of fresh and spent Ni-based catalysts by X-ray fluorescence spectroscopy, N 2 adsorption, X-ray diffraction, H 2 temperature-programmed reduction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were performed. It was demonstrated that support composition determines NiO dispersion as well as reducibility of Ni species through different strength of Ni-support interaction. The preparation method modifies the phase composition and catalyst ability for reduction. The catalyst evolution under reaction conditions was studied. The NiO (∼15 nm) and NiPd alloy (∼18 nm) phases were observed in the spent catalysts. It was found that the Ni o /NiO ratio can be regulated by support composition and preparation mode of catalysts. It is demonstrated that studied catalysts provide high methane conversion of 90–100%, CO yield of 55–85% and H 2 yield of 55–75% in ATR of CH 4 at 750–950 °C. The optimal composition and preparation method of catalyst were selected. The best ATR of CH 4 performance is provided by 10 Ni 0.5 Pd/10Ce 0.5 Zr 0.5 O 2 /Al 2 O 3 catalyst prepared by Pd/Ni sequential impregnation method that can be associated with peculiarity of NiPd particles structure and the optimal ratio between NiO species with different ability for reduction. [ABSTRACT FROM AUTHOR]

A new LaCr 0.85 Ru 0.15 O 3 perovskite-type catalyst for CH 4 partial oxidation with a high activity and selectivity for syngas with good thermal stability and resistance against coking has been developed. In this paper, the catalyst preparation method, catalyst characterization, results of catalytic tests in a micro-reactor and kinetic modeling are discussed. A partial incorporation of Ru in the perovskite support has been demonstrated which can be responsible for the reported high activity and stability for this catalyst. Reactivity tests have been carried out at both low and high GHSV regimes (≈1–2 × 10 7 h −1 ); for the latter case the CH 4 –O 2 partial oxidation reaction system has been studied at incomplete methane (7–18%) and O 2 (20–65%) conversion, as rarely reported in the literature. The variation of temperature (650–850 °C) and feed gas composition (in terms of CH 4 , CO, CO 2 , H 2 and H 2 O inlet partial pressure) allowed to study the reaction system over a wide range of experimental conditions gaining insight in the reaction mechanism. A kinetic model is proposed where CH 4 partial oxidation, H 2 and CO oxidation and water–gas shift are used to describe the involved lumped reaction network. External diffusion resistances have been found to be negligible whereas internal diffusion resistances have been accounted for by means of a single particle model able to describe the concentration profiles inside the catalyst pellet. Pre-exponential factors and activation energy values for all reactions have been estimated by means of a least square fitting of the experimental data. It is found that CH 4 partial oxidation dominates the first region of the catalyst bed while H 2 and CO oxidation become important in the remaining part of the bed. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed ATR catalysts Ni–Me/La2O3 (Me=Pt, Pd, Re, Mo, Sn, Me/Ni=0.01–0.05). [•] LaNiO3 perovskite single phase acts as a precursor of formed Ni–Me/La2O3. [•] Sequence of promoter effect on CH4 conversion and H2, CO yields is: Pt

Abstract: The catalytic study of the Ni-catalysts based on Ni/Mg/Al mixed oxides from hydrotalcite-like compounds (ex-LDH) shows a particular behaviour in the methane decomposition reaction. While deactivation of the catalyst occurs in the presence of methane within the range of temperature 600–700 °C, a subsequent and spontaneous “auto-regeneration” of the catalyst is observed above and below this temperature range. Increasing reaction temperature above 700 °C or decreasing it below 600 °C allows recover completely catalytic activity of the deactivated catalyst. This catalyst “auto-regeneration” process is an absolutely reversible process. XPS results of the spent catalysts suggest that the origin of this behaviour is a reversible change in the nature of the carbon deposit as a function of temperature. Consequently, the kinetic control of the carbon formation avoids the catalyst deactivation, and allows to reach the thermodynamic limit of the hydrogen produced. [Copyright &y& Elsevier]

Abstract: A series of bimetallic PdNi catalysts supported on alumina modified with different amounts of phosphorus (0.5–5 wt%) were prepared. The effect of phosphorus content on the structure, surface properties and catalytic behavior of supported PdNi catalysts in biogas reforming was studied. The physicochemical properties of the samples were characterized by using different techniques: N2 adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), temperature-programmed desorption of ammonia (TPD), thermogravimetric and differential thermal analysis (TG/DTA) and scanning transmission electron microscopy (STEM). The catalytic properties of the catalysts were evaluated in the reaction of reforming of methane with CO2. It was shown that increasing the P content (≥1 wt%) leads to agglomeration of the metal Ni particles, as well as to increase of the total acidity of the catalysts. Within bimetallic system, the PdNi catalyst with 0.5 wt% phosphorus showed the best performance and stability caused by the presence of highly dispersed nickel particles on the catalyst surface due to the strong interaction between supported species and alumina. [Copyright &y& Elsevier]

Abstract: This paper addresses the options developed over the past two decades for the conversion of methane into valuable chemicals and fuels while avoiding the high energy requirements of the steam reforming process for producing H2/CO mixtures. Several aspects of the approaches undertaken accordingly are briefly examined here. Each option has its own set of limitations. Nonetheless, the cost-effective separation of useful products is a common denominator across the board in these processes, with the other most important issue being the separation of oxygen from air, requiring C–H bond activation by oxygen. The widespread use of methane for producing fuels and chemicals appears to be within reach, but current economic uncertainties limit both the amount of research activity and the implementation of emerging technologies, although the extensive use of methane for the production of fuels and chemicals is expected to become a reality very soon. [Copyright &y& Elsevier]

Abstract: The aim of this work, concerning with the partial oxidation of methane to syngas in a self-sustained short contact time reactor using pure oxygen as oxidant, was the development of perovskite-based nickel–lanthanum (LaNiO3 with Ni partially substituted by Co and Pt) catalysts and the comparison of their performance with that of 5% nickel on alumina catalyst. The prepared catalytic materials were arranged in a fixed bed and the activity tests were carried out by increasing the WHSV from ∼130 to ∼560Nlh−1 gcat −1. Perovskite-based catalysts were characterized by performances lower than that of 5% Ni/Al2O3. The very low perovskites catalytic performance towards the partial oxidation of methane was mainly due to the high reducibility of their structures into La2O3, metallic Ni, and Ni oxides; moreover, La and Ni species further reacted with the CPO reaction products CO2 and H2O leading thus to the formation of the poorly active species La(OH)3, La2NiO4 and La2O2CO3. On the contrary, 5% Ni/Al2O3 catalyst showed a very satisfactory CH4 conversion always above 85%, remaining stable by varying WHSV. The same trend was noticed for H2 and CO selectivity, both around 90%. Furthermore, as concerns the bed temperature by increasing WHSV, 5% Ni/Al2O3 catalyst presented quite stable T in and T out (the latter around 1200–1250°C), whereas the perovskite-based catalysts showed a quick T in decrease and T out increase, anyway not exceeding 1200°C. The good performance and high thermal stability of 5% Ni/Al2O3 catalyst was probably related to the arrangement of the nickel particles, which resulted somehow thermally protected as partially embedded in the alumina carrier. [Copyright &y& Elsevier]

Abstract: Functionalized carbonaceous materials have been investigated as supports of PtRu nanoparticles for the electrooxidation of methanol, using such conventional electrochemical methods as cyclic voltammetry and chronoamperommetry and by measurements in a CH3OH/O2-fed single cell. Further, to understand the effect of oxygen-containing groups on the supports in the methanol oxidation reaction (MOR), a kinetic study of the catalyst that has the best behavior in this process has been performed. The study at different temperatures of PtRu nanoparticles supported in multiwall carbon nanotubes (MWCNTs) with a high amounts of functional groups—PtRuCNT-ST—show that there was low CO poisoning during the MOR on this catalyst. The low apparent energy on PtRuCNT-ST in the MOR was attributed to CO diffusion or to the dissociative adsorption of methanol. Both factors had a beneficial effect on the oxygen-containing groups on MWCNTs, facilitating oxidation of the carbonaceous intermediates to CO2 or HCOOH. These findings have been confirmed by studies in a single cell feeding with CH3OH/O2, demonstrating that PtRuCNT-ST is the best-performing anodic electrode. [Copyright &y& Elsevier]

Abstract: A series of bimetallic PdNi catalysts supported on mesoporous MCM-41 with different Ni content (Ni/Si ratio of 0.2–0.4) was synthesized. The effect of Pd addition to Ni-containing catalysts as well as the effect of the Ni content on the surface and catalytic properties of the catalysts was studied. The samples were characterized using various techniques, such as energy-dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction, thermogravimetric and differential analyses, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and temperature-programmed reduction. Reforming of methane with carbon dioxide was used as a test reaction. The results indicated that the addition of a small amount of Pd (0.5%) to Ni-containing catalysts leads to formation of small nano-sized, easy reducible NiO particles. Agglomeration of NiO as well as of metallic nickel phase over PdNi samples increased with increasing the Ni content. Formation of filamentous carbon over surface of spent monometallic Ni and bimetallic PdNi catalyst was observed. In spite of filamentous carbon deposition, the catalytic activity and stability of bimetallic PdNi catalysts are higher than those of monometallic Ni one. Within bimetallic system, the PdNi catalyst with Ni/Si ratio of 0.3 revealed the best performance and stability caused by presence of small nickel particles well dispersed on the catalyst surface. [Copyright &y& Elsevier]

Abstract: The CO2 reforming of CH4 over Pt catalysts supported on nanocrystalline mesoporous ZrO2 and CeO2–ZrO2 carriers was investigated at atmospheric pressure. The effect of CeO2 content (1–12wt%) on the surface and catalytic properties of the catalysts was studied. It was found that the pre-treatment temperature and the concentration of CeO2 influence on the morphology of Pt particles. The calcination temperature as high as 1073K leads to sintering of Pt particles deposited over zirconia- and CeO2-loaded zirconia substrates. Temperature-programmed reduction (TPR) results showed good reductive properties for Pt/CeO2–ZrO2 catalysts due to both, the high surface shell reduction of zirconia and the synergetic effect between Pt and CeO2. X-ray photoelectron spectroscopy (XPS) of reduced catalysts revealed the presence of different Pt oxidation state depending on the catalyst composition. Stabilization of partially oxidized platinum species by ceria was detected for the reduced Pt/CeO2–ZrO2 samples. An activation period was required for the stabilization of the activity of Pt/CeO2–ZrO2 catalysts. The high stability of Pt/CeO2–ZrO2 catalysts was related to the close contact between Pt and CeO2. [Copyright &y& Elsevier]

Abstract: The effect of La2O3 content on the structural properties and catalytic behavior of Pt/xLa2O3–Al2O3 catalysts in steam reforming of methane and partial oxidation of methane was investigated. There was a decrease in the density of Pt sites with the increase of La2O3 loadings according to Fourier transform infrared spectroscopy of adsorbed CO and to dehydrogenation of cyclohexane results. However, transmission electron microscopy data indicates an opposite trend. This apparent disagreement could be due to the partial coverage of Pt sites by LaO x species. CH4 turnover rates and specific rates of steam reforming of methane increased for higher La2O3 loadings. The Pt/Al2O3 catalyst was strongly deactivated during partial oxidation of methane, while La2O3-containing catalysts exhibited higher stability. The increase of activity observed during the reactions was ascribed to the ability of the [LaPt x O]Pt0-like species to promote the gasification of coke. This cleaning mechanism led to higher accessibility of the active sites to CH4. [Copyright &y& Elsevier]

Abstract: Alumina-supported bimetallic and monometallic Mn and Pd monolithic catalysts were prepared and tested in methane combustion. Two different reactor configurations were adopted for catalyst testing, i.e. a fixed-bed laboratory-scale reactor and a pilot-plant reactor which allowed work at different temperatures and pressures. The results of catalyst performance showed that all bimetallic catalysts are considerably more stable for methane combustion than the monometallic palladium catalyst. With the aim to explain the relationship between activity-stability and structure and surface properties, the catalysts were characterized by TPO, XRD, XPS and ICP-AES. The high stability displayed by the bimetallic systems is attributed to the influence of manganese in retarding the decomposition of PdO into metallic palladium. Thus, it appears that manganese oxides inhibit PdO decomposition, as a consequence of the increase in oxygen mobility in the manganese oxide spinel phase. [Copyright &y& Elsevier]

Abstract: The catalytic methane combustion was investigated over alumina-supported monometallic and bimetallic palladium and manganese oxide catalysts. The catalytic activity of these systems showed that palladium incorporation on MnO x /Al2O3 catalyst leads to an enhancement in methane combustion. The higher catalytic activity of the PdMn/Al2O3 catalysts is related to a greater mobility of lattice oxygen in manganese oxide in the presence of palladium. These bimetallic catalysts also showed a significant improvement in catalysts stability with respect the monometallic ones. Surface analysis of the used catalysts revealed less amount of coke and Mn/Al and Pd/Al atomic ratios almost unchanged, which is indication of absence of active phase sintering. [Copyright &y& Elsevier]

Abstract: The partial oxidation of methane over supported (ZrO2, CeO2–ZrO2) rhodium catalysts was investigated at atmospheric pressure. The effect of temperature, CH4/O2 ratio, catalyst composition and pre-treatment was studied. Ceria doping of the support material resulted in significant improvements concerning the methane conversion and syngas selectivity, which could be related to a higher noble metal dispersion on the Rh/CeO2–ZrO2 catalyst. In addition, the light-off temperature was decreased by 128°C when using CeO2–ZrO2 as support. X-ray photoelectron spectroscopy revealed the presence of different Rh oxidation states depending on catalyst composition and pre-treatment. A stabilization of partially oxidized (Rhδ+) species by ceria could be detected. An active and stable catalyst behavior could be observed for Rh/CeO2–ZrO2, irrespectively of catalyst pre-treatment, whereas an activation period was required for stabilizing the activity of the Rh/ZrO2 catalyst. The activity tests indicate that the indirect reaction mechanism, consisting of methane combustion followed by steam and dry reforming, prevails under the experimental conditions studied. [Copyright &y& Elsevier]

Abstract: The effect of Ni content (1–12wt%) on the surface and catalytic behavior of bimetallic PtNi catalysts supported on ZSM-5 for reforming of methane with CO2 was studied. The properties of the catalysts, before and after exposure to reaction conditions, were investigated employing N2 adsorption–desorption isotherms, XRD, TGA/DTA, FTIR spectroscopy of framework vibrations, DRIFT spectroscopy of adsorbed CO, XPS and TPR. It was shown that addition of a small amount of Pt (0.5%) to Ni catalyst leads to formation of small nano-sized NiO particles and easy reduction of NiO. It was found that the amount of Ni precursor plays an important role on the surface and catalytic properties of bimetallic catalysts. The improvement of catalytic activity and stability observed for bimetallic catalyst was attributed to an increase of the nickel metallic dispersion caused by an intimate contact between nickel and platinum at Ni-loading of 6wt%. [Copyright &y& Elsevier]

Abstract: The catalytic oxidation of methane was investigated over six catalysts with different palladium and platinum molar ratios. The catalysts were characterised by TEM, EDS, XPS, PXRD and temperature-programmed oxidation. The results suggest that in the bimetallic catalysts, an alloy between Pd and Pt was formed in close contact with the PdO phase, with an exception for the Pt-rich catalyst, where no PdO was observed. It was found that the molar ratio between palladium and platinum clearly influences both the activity and the stability of methane conversion. By adding small amounts of platinum into the palladium catalyst, improved activity was obtained in comparison with the monometallic palladium catalyst. However, higher amounts of platinum are required for stabilising the methane conversion. The most promising catalysts with respect to both activity and stability were Pd67Pt33 and Pd50Pt50. The platinum-rich catalyst showed very poor activity for methane conversion. [Copyright &y& Elsevier]

Abstract: In the present work, Ni/α-Al2O3 catalysts modified with different amounts of CaO and MgO were used for the production of hydrogen by catalytic partial oxidation (CPO) and wet-CPO processes of methane. In the wet-CPO process, small additions of water were introduced into the feed of the reactor to improve both the H2 yield and methane conversion. The addition of water is also beneficial because coke formation becomes thermodynamically unfavorable. The catalysts were characterized before and after the reaction with XRD, XPS, TPR and TPO techniques. Several methane decomposition tests and methane pulse experiments were carried out with a view to correlating the ability of metal sites to activate methane in the absence of oxygen with the performance for CPO and wet-CPO reactions. [Copyright &y& Elsevier]

Abstract: Pure hydrogen was obtained by catalytic methane decomposition over thermally stable nickel-based catalysts prepared from hydrotalcite-like precursors. Two different Ni–Mg–Al catalyst compositions were tested in the catalytic pyrolysis reaction of methane. The catalytic results were compared with those of a catalyst prepared by conventional impregnation of Ni–Mg phases on an alumina support. The high thermal stability of these catalysts was demonstrated in several reaction–regeneration cycles. The regeneration processes were performed with CO2 and O2 as regenerating agents. Using either CO2 or O2 gas, hydrogen production after regeneration increased with regard to the fresh catalyst. Upon catalyst regeneration, larger amounts of hydrogen were obtained on catalysts regenerated with CO2 than with O2. The high thermal stability of the Ni particles of the catalysts from hydrotalcite-like precursors was improved in the presence of Mg. This high Ni-stability is a key factor for increasing hydrogen production after consecutive reaction–regeneration cycles. [Copyright &y& Elsevier]

Abstract: Lanthana- and magnesia-supported nickel catalysts with Ni-loading ranging from 10 to 30wt.% and calcined at temperatures 1073–1273K are prepared and tested in the catalytic partial oxidation of methane. These catalysts are characterized by means of X-ray diffraction (XRD), N2 adsorption–desorption measurements, temperature-programmed reduction (TPR), thermogravimetric analysis (TG) and X-ray photoelectron spectroscopy (XPS) techniques. The main objective of this work is the development of more efficient catalysts to produce syngas (H2 +CO) from methane. For the catalysts developed the influence of the nickel content and the support on the activity are studied in a series of nickel catalysts. [Copyright &y& Elsevier]

PtCoZSM5 in powder form is an effective catalyst for the selective reduction of NOx with methane. In order to attach a stable film of this powder to a cordierite honeycomb monolith, several approaches were assayed. Either NaZSM5 or CoNaZSM5 were washcoated on the cordierite, and then either Co and Pt or Pt, respectively, was ion exchanged to obtain the desired composition. Another option explored was to washcoat the PtCoZSM5 powder. Al(NO3)3 used as a binder produced undesirable changes in the catalytic behavior due to the formation of non-stoichiometric cobalt aluminate during the calcination of the monolith at 550°C. The powder performance was matched when PtCoZSM5 was washcoated without binder. Inspection of the monolith after 80h on stream showed no deterioration. [Copyright &y& Elsevier]

ZrO2–TiO2 mixed oxides, prepared using the sol–gel method, were used as supports for platinum catalysts. The effects of catalyst pre-reduction and surface acidity on the performance of Pt/ZT catalysts for the reduction of NO with CH4 were studied. The diffuse reflectance infrared Fourier transformed (DRIFT) spectra of CO adsorbed on the Pt/ZT catalysts, and also on the Pt/T and Pt/Z references, pre-reduced at 773 K in hydrogen, revealed that an SMSI state is developed in the Ti-rich oxide-supported platinum catalysts. However, no shift in the binding energy of Pt 4f7/2 level for Pt/T and Pt deposited on Ti-rich support counterparts pre-reduced at 773 K was found by photoelectron spectroscopy. The DRIFT spectra of the catalysts under the NO+O2 co-adsorption revealed the appearance of nitrite/nitrate species on the surface of the Zr-containing catalysts, which displayed acidic properties, but were almost absent in the Pt/T catalyst. The intensity of these bands reached a maximum for the Pt/ZT(1:1) catalyst, which in turn exhibited a larger specific area. In the absence of oxygen in the feed stream, the NO+CH4 reaction showed DRIFT spectra assigned to surface isocyano species. Since the intensity of this band is higher for the Pt/ZT (9:1) catalyst, it seems that such species are developed at the Pt–support interface. [Copyright &y& Elsevier]