CeO2 and binary La2O3-CeO2 oxides, with different La/Ce atomic ratios (1:4; 1:1; 4:1), were synthesized using sol-gel method in the presence of citric acid in ammonia solution, at pH similar to 9, and Ni (10 wt%) was added by wetness impregnation method. The physical-chemical properties, catalytic activity and long-run stability of the prepared catalysts were evaluated in DRM reaction. Characterizations of both fresh and spent catalysts were carried out using low-temperature N-2 adsorption, XRD, TGA, TPR, Raman and TEM analyses. The DRM gradient catalytic tests performed in the range of 400-800 degrees C revealed higher catalytic conversions for Ni/La2O3-CeO2 catalysts, especially for those with La/Ce ratio 1:4 and 1:1. The stable conversions of CH4 and CO2 (long run at 650 degrees C for 24 h) registered for such Ni/La2O3-CeO2 catalysts were attributed to the presence of small Ni crystallites. During long run tests, Ni/La2O3-CeO2 catalysts, with La/Ce atomic ratios 1:4 and 1:1, formed the same types of carbon, both as filaments and layered carbon with graphene structure, but their catalytic activity was retained. Ni/CeO2 showed the smallest content of carbon, however, exhibited lower CH4 and CO2 conversions in comparison with the Ni-La2O3-CeO2 systems, due to the presence of big Ni particles with sizes of up to 0.5 mu m.

10 wt%Ni/La2O3 catalysts for dry reforming of methane (DRM) were synthesized by wetness impregnation of lanthana supports prepared using sol-gel citric method with and without NH3 addition (Ni-La CA-NH3 and Ni-La CA, respectively). The support preparation conditions affect the nature, phase composition, and distribution of Ni phases (LaNiO3, NiO and La3Ni2O6). The gradient temperature DRM tests (400-800 degrees C) reveal higher catalytic activity of Ni-La CA (at 650 degrees C, X(CO2) = 65.7%, X(CH4) = 54.6%, H-2/CO = 0.71). The Ni-La CA-NH3 shows higher stability (at 650 degrees C and 24 h, X(CO2): 73.7% => 76.4%, X(CH4): 64.7% => 64.6%, H-2/CO: 0.77 => 0.72). For both catalysts, La2O2CO3 phase is formed after long run tests at 650 degrees C 24 h, with the greater TGA weight loss and stronger deactivation being observed for Ni-La CA. The H-2-reduced Ni La CA-NH3 features ultrasmall (1-2 nm) Ni NPs strongly interacting with the support. Catalyst nature affects the amount of carbon coke formed. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

LaMnO3 (LM) catalysts with a molar ratio of citric acid (CA) to metal (La3+ + Mn2+) nitrates ranging from 0.5 to 2 (LM0.5 to LM2) were synthesized by the citrate sol–gel method with the aim of studying the effect of the citric acid ratio on the physicochemical properties and the catalytic performance in hydrocarbon oxidation. Structural and morphological properties of these catalysts were characterized by X-ray diffraction (XRD) and specific surface area (N2 adsorption) measurements, while the chemical composition was determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In the selected samples, additional characterizations were carried out by thermogravimetric and differential thermal analysis (TGA/DTA), Fourier Transform Infrared Spectroscopy (FT-IR), temperature-programmed reduction by hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the amount of citric acid used significantly influenced the TGA/DTA profile of gels along with the physicochemical properties of the catalysts. The XRD patterns are consistent with the perovskite formation as the main phase. The segregation of a small amount of Mn3O4, detected for molar ratios ranging between 0.5 and 1.5, suggested the formation of a slightly nonstoichiometric LaMn1−xO3 phase with a relatively high content of Mn4+. The catalytic performance was evaluated in the total oxidation of two selected hydrocarbons, toluene and propene, which represent typical volatile organic compounds (VOCs). Typically, three consecutive catalytic cycles were performed in order to reach steady-state performance in toluene and propene oxidation. Moreover, the stability of the catalysts under reaction conditions was investigated through 24-h experiments at 17% of toluene conversion. The catalysts LM1.2, LM1.3, and LM1.5 showed the best catalytic performance in both hydrocarbon oxidations, well comparing with the Pd/Al2O3 used as a reference.

The correlations between surface and bulk properties of TiO2 and TiO2-doped oxides with their photocatalytic and catalytic performances are fundamental to understanding the basic mechanisms of action and to design new materials with enhanced properties. TiO2-based oxides have been most widely investigated in the past decades as photocatalysts and many comprehensive review articles have reported the advances made in the field of TiO2-based photocatalysis, while poor attention has been paid to the use of TiO2 in heterogeneous catalysis, as a catalyst itself, or as support for noble metals. Moreover, as far as we know, no previous review articles or book chapters have analyzed the relationship between characterizations of both surface/bulk properties of TiO2 and TiO2-doped oxides, with their photocatalytic and catalytic activity. This chapter aims to discuss some structural and surface properties of TiO2 and TiO2-doped oxides, investigated by using the following techniques: X-ray diffraction, transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and acidity measurements. To this purpose, some selected recent articles are presented and the relationship structure–activity and photocatalytic activity is attempted.

Ni catalysts with nominal loadings ranging between 2.5 and 20 wt% were synthesized over perlite by wet impregnation, then filtered, washed and calcined at 500 degrees C. Chemical analyses performed by MP-AES revealed that the maximum Ni content loaded over perlite corresponded to similar to 15 wt%. Therefore, for comparison reasons, a Ni(20 wt%)/perlite catalyst was prepared by wetness impregnation without performing any washing treatment. The so prepared catalysts were tested in methane dry reforming without performing any pretreatment reduction. The catalytic performances were compared by increasing the temperature from 500 up to 800 degrees C under the reaction mixture composed of 15 vol% CH4 + 15 vol% CO2/N-2. Ni(15 wt%)/perlite was the most active catalyst among the series of monometallic samples. The effect of co-impregnating perlite with Ni and Zr or Ni and Ce precursors in order to obtain catalysts with final composition, Ni(15 wt%), 10 and 20 wt% as Zr or Ce, perlite (75 or 65 wt%) was, then, investigated. Characterizations performed by XRD, BET, DRS and H-2-TPR evidenced that the physico-chemical and reduction properties are influenced by the Ni content and by the presence of zirconia and ceria oxides. It is worth of noting the increased reducibility of NiO species promoted by zirconia and ceria addition. The catalytic activity in the dry reforming of methane was also affected by the presence of doping oxides, in terms of enhanced CH4 and CO2 conversions and higher H-2/CO atomic ratios. Runs tests at 700 degrees C for 12 h were carried out and the spent catalysts were analysed by TGA and TEM. Over Ni(15 wt%)/perlite large amount of amorphous carbon grows on the surface blocking the active centres, while zirconia and ceria doping improved the resistance to carbon poisoning favouring growing of filamentous carbon residues in small amount. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF08), La0.6Sr0.4Co0.2Fe0.79Ni0.01O3-delta (LSCF08-Ni) and La0.6Sr0.4Co0.2Fe0.79Pd0.01O3-delta (LSCF08-Pd) perovskites were synthesized by Citrate-EDTA method, by using NiCl2 or PdCl2 as metal precursors, and their physicochemical properties were characterized by XRD, TGA, TPD and TPR. XRD data evidenced an expansion of the lattice parameters of LSCF08-Pd, while a contraction of the lattice occurred for LSCF08-Ni, with respect to the undoped LSCF, suggesting different oxygen vacancies content in the perovskite (confirmed by TGA) likely due to a different oxidation state of Ni and Pd species stabilized in the structure. TEM analyses performed over LSCF08-Pd revealed the presence of metallic Pd nanoparticles well dispersed in the matrix that accounts for the increased reducibility of the Co and Fe species with respect to LSCF08-Ni and undoped perovskite. AC impedance measurements that were carried out on symmetric cells consisting of LSCF-based materials deposited onto Ce0.8Gd0.2O2-delta (GDC) electrolyte proved the enhanced electrochemical performances of Ni/Pd doped LSCF. The electrochemical characterization of LSCF08, LSCF08-Ni and LSCF08-Pd electrodes was completed by performing cyclic voltammetry experiments in the range of temperature 600-800 degrees C, varying the potential (U) between 0.3 V and -1 V, at scan rates in the range 1-50 mV s(-1) and working under flow of 0.7 vol % O-2 in He (30 ml/min). (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Four different catalysts based on manganese oxide were prepared: a perovskite (LaMnO3), via sol-gel method; Mn203, rapid method and an Octahedral Molecular Sieve (OMS-2) by two different preparation methods, via solid state (OMSs) and hydrothermal method (OMSh). The physicochemical properties of these catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption at -196 degrees C, thermogravimetric and differential thermal analysis (TGA/DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and temperature-programmed reduction with hydrogen (H-2-TPR). Their catalytic performances were evaluated in the catalytic oxidation of toluene. Three consecutive catalytic cycles were performed for each catalyst in order to reach steady state performances. In order to assess the stability of the catalysts under reaction conditions, the catalytic performances were studied upon long term experiments running for 24 hat 25% of toluene conversion. For comparison purposes, the catalytic activity of the present manganese oxide catalysts was compared with that of typical industrial catalysts such as a commercial Pd/Al2O3 catalyst containing 0.78% Pd. The crystalline features detected in the XRD patterns, are well-consistent with the formation of the desired structures. Based on their specific surface area and their low-temperature reducibility, the catalysts were ranked as follows: OMSS > Mn2O3 > OMSh > LaMn03. This trend was in good agreement with the performances observed in the catalytic removal of toluene. A kinetic model was proposed and a good agreement was obtained upon fitting with the experimental data. (C) 2017 Elsevier B.V. All rights reserved.

A calcium phosphate oxide with composition analogous to the apatite phosphate, was synthesized by dissolution and precipitation of Moroccan natural phosphate, then, used as a carrier for deposition of different amount of nickel (2.5, 5, 10 wt%). The so obtained support and the resulting catalysts were characterized by several techniques, such as ICP-AES, XRD, BET, FT-IR, DRS, TPR. XRD characterization showed that the support has the crystalline structure typical of apatite and the chemical composition was close to that of fluoroapatite with some fluoride partially substituted by hydroxide ions.After impregnation of Ni, a portion of Ca2+ ions of the support was exchanged by Ni2+ ions, as confirmed by UV-visible-NIR analysis. The prepared catalysts were tested in the methane dry reforming reaction without performing any reduction pre-treatment except the exposure to the reaction mixture. High catalytic activity at 700 degrees C and good stability in the production of hydrogen were registered for such Ni loaded samples suggesting a good resistance to coke poisoning according to the basic nature of the support. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Pd/Ce0.6Zr0.4Ox/SiO2 and Pd/Ce0.73Tb0.27Ox/SiO2 catalysts were prepared by incipient wetness impregnation method using aqueous solutions of Ce(NO3)(3)center dot 6H(2)O, ZrO(NO3)(2)center dot nH(2)O, Tb(NO3)(3)center dot 5H(2)O and Pd(NO3)(2)center dot nH(2)O precursors. The catalysts were characterized by X-ray diffraction (XRD), Temperature Programmed Reduction (TPR-H-2), CO Chemisorption, Oxygen Storage Capacity (OSC) and Infrared spectroscopy of adsorbed CO (FTIR-CO). The catalytic activity was measured in the methane oxidation reaction. XRD patterns showed that after two activity cycles, the solids crystallinity was not modified, while TPR results revealed that reduction maxima were shifted to lower temperatures, indicating an improvement in sample reducibility. The CO/Pd ratio diminished with increasing the reduction temperature, suggesting both, Pd inward diffusion/covering by Ce3+ ions (geometrical effects) and/or increase in Pd particles size. The IR spectrum of adsorbed CO reported the presence of cationic palladium species interacting with CO regardless of reduction temperature as well as carbonate species and weak interactions with ceria and silica. Zr and Tb containing samples presented a high and stable OSC after undergoing various OSC cycles. The catalytic activity was enhanced after two reaction cycles due to the formation of large PdO particles. T-50 values indicated that reduction treatments prior to methane reaction generated more active catalytic species than those obtained by oxidation treatment; however, such active species were not stable at high temperatures.

Bamboo-like carbon nanotubes are members of the carbon nanotubes (CNTs) family, whose structure is made up of separated hollow compartments and bamboo knots. Due to the peculiar structure of the CNTs species, the growth mechanism and related features have been widely investigated. Bamboo-like carbon nanotubes are widely applied in several fields, such as sensors, adsorbents, catalysts, and lithium-ion battery electrodes materials. Different methods have been applied for the synthesis of carbon nanotubes, among them, catalytic chemical vapor deposition has been singled out as the most used procedure due to low cost with a high quality product. The present review is devoted to increasing the literature dealing with the design, synthesis, and characterization of bamboo-like carbon nanotubes grown over different catalysts. Results on the methane dry reforming reaction, hydrocarbon thermal decomposition, special chemical vapor deposition as well as other methods applied to the preparation of bamboo-like carbon nanotubes are discussed. The differences in the carbon deposits between the dry reforming reaction and other reaction methods are compared and possible formation mechanisms of bamboo-like carbon nanotubes are discussed.

We investigated the effect of nickel doping on the electronic structure and performance of nanostructured La0.6Sr0.4Co0.2Fe0.8-0.03Ni0.03O3-delta prepared by the one-pot sol gel method. The commercial undoped La0.6Sr0.4Co0.2Fe0.8O3-delta (ISCF0.8) was used as reference. Moreover, for comparison, Ni (3 mol %) was deposited by wetness impregnation over the La0.6Sr0.4Co0.2Fe0.8O3-delta. We show by in situ X-ray absorption spectroscopy at 900 degrees C under air flow that nickel enters the B perovskite site of the material and favors the stabilization of the cobalt oxidation state, as evidenced by the delay in the decrease of the average Co valence with respect to undoped samples. Our results are further supported by in situ X-ray Raman spectroscopy (YRS) that allowed us to monitor the temperature evolution of the 0 Kedge. XRS evidences that nickel-doped LSCF shows unmodified O2p-TM3d density of states, which proves that the Co oxidation state is preserved. Electrochemical impedance spectroscopy measurements were carried out over half-cell systems consisting of LSCF-based materials deposited onto a Ce0.8Gd0.2O2-delta electrolyte. The improvement of the electrochemical performances of the Ni-doped La0.6Sr0.4Co0.2Fe0.8-0.03Ni0.03O3-delta sample with respect to a reference Ni-impregnated LSCF is attributed to the stabilisation of the TM-O-6 structural units, which were recently proposed as the functional units for oxygen reduction.

Biodiesel can be obtained from waste cooking oils (WCO) and represents a promising renewable fuel alternative to fossil oil. However, its production from low-cost feedstock requires the lowering of the free fatty acids (FFAs) concentration below 1% in order to prevent soaps formation. In the present study, the biodiesel synthesis was performed from a high acidity feedstock using a three-step method: the first one is an in-situ esterification using sulfuric acid as catalyst, the second one is the neutralization and the third one is the transesterification. The last two processes were performed using lime stone as neutralizing agent and basic catalyst, as well. The neutralization was the crucial step and the aim of the present work was the optimization of the reaction parameters. The results showed that the conversion was almost complete in the three-step method. The 1 H-NMR, FT-IR, GC and TGA analyses of the final product confirmed that the purity of the biodiesel produced by such insitu three-step method and that its properties satisfy the European standards.

(La,Sr)(Co,Fe)O 3 (LSCF) perovskites are well known promising materials for cathodes of solid oxide fuel cells. In order to reduce cathode operational temperature, doping on B ‐sublattice with different metals was suggested. Indeed, as it was shown recently experimentally, doping with low Pd content increases oxygen vacancy concentration which is one of factors controlling oxygen transport in fuel cells. In this Communication, we modeled this material using first principles DFT calculations combined with supercell model. The charge density redistribution, density of states, and local lattice distortion around palladium ions are analyzed and reduction of the vacancy formation energy confirmed.

The transesterification reaction of two different types of raw materials, a refined cooking oil and a used cooking sample, was performed at small scale (10 L) at the constant temperature of 65 degrees C. The effects of several reaction parameters, such as KOH wt% with respect to the oil weight, methanol/oil molar ratio and reaction time, were investigated. Biodiesel yields as good as 97.5 and 93.2% were achieved for the refined and the cooking oils, respectively, in the following conditions: 1.2 wt% of KOH as catalyst, a methanol/oil molar ratio of 6:1 and reaction time of 60 min.The properties of the biodiesel obtained starting from the used cooking oil are as good as those of the biodiesels obeying the European standards. The resulting product was used in a diesel electricity generator engine, which operated in real conditions. The results showed that biodiesel combustion leads to higher concentration of CO and to a lower emission of NOx as compared to a petrodiesel-fueled engine. An optimization of the operating parameters of the engine would guarantee lower CO emissions in conformity with the regulation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A powder oxide with composition analogous to the apatite phosphate, was synthesized by dissolution and precipitation of Moroccan natural phosphate, then used as carrier for deposition of different amount of nickel. The support and the resulting catalysts were characterized by several techniques. XRD characterization showed that the support has the crystalline structure typical of apatite oxides. According with the chemical analysis, the composition is closed to the fluoroapatite where fluoride is partially substituted by hydroxide. After impregnation of Ni a portion of Ni2+ ions was exchanged with Ca2+ ions, as confirmed by UV-visible-NIR analysis. The so prepared catalysts were tested in the dry of methane without performing any reduction pre-treatment except the exposure to the reaction mixture. High catalytic activity at 700 °C and good stability in the production of hydrogen were found for such Ni loaded catalysts suggesting a good resistance to coke poisoning according to the basic nature of the support.

LaxSr1-xCoyFe1-yO3- perovskites were investigated as electro-catalytic materials for H2O2 and glucose electrochemical sensors. La0.6Sr0.4FeO3- and La0.6Sr0.4Co0.2Fe0.8O3- formulations have been synthesized by citrate method and characterized by XRD and SEM. TPR and XPS analyses were performed to evaluate the oxidation states of metal ions and surface composition. The electrochemical performances of H2O2 and glucose sensors fabricated by modifying commercial screen printed carbon electrodes with perovskites, were evaluated by cyclic voltammetry and amperometry in alkaline medium. Results demonstrated that the substitution of Fe with Co ions in the ferrite structure enhance the electrocatalytical activity towards the oxidation of H2O2 and glucose.