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The objective of this paper was to design sustainable nickel catalysts supported on selected fly ash based zeolites to thermal processing of lignocellulosic feedstock towards hydrogen-rich gas. Moreover, in order to increase its catalytic performance in the studied process the catalyst supported on the most promising fly ash based zeolite was modified by selected rare-earth and transition metals (La, Pr, Ce, Y, Gd, Zr). The performed measurements exhibited that incorporation of nickel into the structure of zeolite A modified by lanthanum resulted in the most effective production of H2. The characterization of its physicochemical properties (XRD, TPR, SEM-EDS, TPD-NH3, BET and TGA-DTA) suggested that large pore size, moderate acidity, increased reducibility of an active phase and higher resistance to coke formation are the main factors responsible for increased activity of this catalyst.

The main goal of this work was to develop a highly active catalyst in lignocellulosic biomass conversion to hydrogen-rich gas. The studies were focused on the evaluation of an impact of dealuminati...

Olive stones obtained as a by-product from olive oil extraction in combination with the favourable climate in Mediterranean countries are value-added feedstocks for the energy sector due to low moisture content ( 20 wt. %), suitable calorific value ( > 18.7 MJ kg−1 as received) and high bulk density (about 750 kg m−3). The torrefaction process at Arigna Fuels with high energy efficiency of (above 90%) improves biomass properties for conversion to a high-value fuel for use in solid fuel stoves. This study reports the effect of moisture content, organic composition, inorganic matter, particle size, heat treatment temperature and residence time on product yields, O2/CO2 reactivity, calorific value, composition and thermal conductivity value of torrefied olive stones. Results showed that both lignocellulosic content and ash composition equally influenced the reactivity of torrefied material. For the first time, time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that the structure of torrefied material from small olive stone particles contains more cellulose than lignin when compared to large grains. Importantly from a technological standpoint, the lower heating values of torrefied olive stones (21.8 MJ kg−1) [1] from a small scale reactor were within the range of values for torrefied woodchip briquettes containing high starch binder content which was an energy increase of ≈ 15% when compared to the raw feedstock. The results showed that olive stones of particle size ≤ 2 mm produced during torrefaction at 270 °C for 30 min are the most suitable material and conditions for briquetting due to high solid yield, low reactivity and low thermal conductivity values. These conditions are recommended for the pilot plant operation using olive stones from the Mediterranean region.

Fast pyrolysis of lignocellulosic biomass is one of the most promising methods of the production of renewable fuels. However, an optimization of the conditions of bio-oil production is not possible without comprehensive analysis of the composition of formed products. There are several methods for the determination of distribution of products formed during thermal decomposition of biomass with chromatography being the most versatile among them. Although, due to the complex structure of bio-oil (presence of hundreds chemical compounds with different chemical character), an interpretation of the obtained chromatograms is not an easy task. Therefore, the aim of this work is to present an application of different chromatographic methods to the analysis of the composition of the mixture of products formed in high temperature decomposition of lignocellulosic feedstock. It includes pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), two dimensional gas (GC x GC) or liquid chromatography (LC x LC) and initial fractionation of bio-oil components. Moreover, the problems connected with the analysis of bio-oils formed with the use of various fast pyrolysis reactors and capabilities of multivariate analysis are discussed.

The main goal of this work was to determine the differences in the composition of the surface and bulk of lignocellulosic feedstock subjected to torrefaction. Miscanthus × giganteus and Willow were used as widely available types of second generation of biomass. The surface of the samples was primarily characterized by time-of-flight secondary ion mass spectrometry. The bulk of the investigated biomass was analyzed by Fourier transform infrared spectroscopy, thermogravimetry and classical chemical methods. The results obtained show that the destruction of the surface of both Miscanthus × giganteus and Willow begin at lower temperature than that observed for the bulk. Moreover, in the case of Miscanthus × giganteus the possibility of the partial surface decomposition of not only the hemicellulose and cellulose but also lignin structure is pointed out. The observed differences between the behavior of the uppermost and deeper layers of the studied biomass samples indicate that the efficiency of their thermal degradation is different and should be taken into account when discussing the torrefaction process.

Tubular-shaped hydrogel structures were obtained in the process of cathodic electrodeposition from a chitosan–hydroxyapatite solution carried out in a cylindrical geometry. The impact of the initial concentration of solution components (i.e., chitosan, hydroxyapatite, and lactic acid) and process parameters (i.e., time and voltage) on the mass and structural properties of deposit was examined. Commercially available chitosan differs in average molecular weight and deacetylation degree, therefore, these parameters were also studied. The application of Fourier-transform infrared spectroscopy, scanning electron microscopy, and time-of-flight secondary ion mass spectrometry allowed obtaining fundamental information about the type of bonds and interactions created in electrodeposited structures. Biocompatible tubular implants are highly desired in the field of regeneration or replacement of tubular-shaped tissues and organs, therefore, the possibility of obtaining deposits with the desired structural properties is highly anticipated.

This research demonstrates that supercritical extraction of the biomass has a remarkable and complex influence on Scots pine tree fractions changing the surface concentration of water, lipids, and metals simultaneously. Surprisingly, this surface composition modification makes a considerable impact on the pyrolysis of the bulk biomass mechanism, leading to the alternation of the volatile and inorganic matter composition. The unique combination of time-of-flight secondary-ion mass spectrometry analysis and utilization of pyrolysis gas chromatography-mass spectrometry data on the thermal behavior of woody biomass demonstrates, for the first time, the extraordinary influence of surface adsorbed metals on the composition of pyrolysis products. ScCO2 could extract the surface metals in the form of fatty acid salts, demonstrating a sustainable and environmentally friendly pretreatment method for controlling the pyrolysis products.

Tri-reforming of methane was examined over Ni/Mg/Al hydrotalcite-derived catalyst for CO2 utilization directly from simulated flue gas mixtures from natural gas-fired power plants. This catalyst showed promising results for the studied experimental conditions, revealing the following order of CH4 conversion: TRM3 (75.9 %)

A goal of this work was to investigate the influence of the preparation procedure and activation conditions (reduction temperature and reducing medium: pure hydrogen (100% H2) or hydrogen-argon mixture (5% H2-95% Ar)) on the activity of Co-containing BEA zeolites in Fischer&ndash, Tropsch synthesis. Therefore, a series of CoBEA zeolites were obtained by a conventional wet impregnation (Co5.0AlBEA) and a two-step postsynthesis preparation procedure involving dealumination and impregnation steps (Co5.0SiBEA). Both types of zeolites were calcined in air at 500 &deg, C for 3 h and then reduced at 500, 800 and 900 &deg, C for 1 h in 100 % H2 and in 5% H2&ndash, 95% Ar mixture flow. The obtained Red-C-Co5.0AlBEA and Red-C-Co5.0SiBEA catalysts with various physicochemical properties were tested in Fischer&ndash, Tropsch reaction. Among the studied catalysts, Red-C-Co5.0SiBEA reduced at 500 &deg, C in pure hydrogen was the most active, presenting selectivity to liquid products of 91% containing mainly C7&ndash, C16 n-alkanes and isoalkanes as well as small amount of olefins, with CO conversion of about 11%. The Red-C-Co5.0AlBEA catalysts were not active in the Fischer&ndash, Tropsch synthesis. It showed that removal of aluminum from the BEA zeolite in the first step of postsynthesis preparation procedure played a key role in the preparation of efficient catalysts for Fischer&ndash, Tropsch synthesis. An increase of the reduction temperature from 500 to 800 and 900 &deg, C resulted in two times lower CO conversion and a drop of the selectivity towards liquid products (up to 62%&ndash, 88%). The identified main liquid products were n-alkanes and isoalkanes. The higher activity of Red-C-Co5.0SiBEA catalysts can be assigned to good dispersion of cobalt nanoparticles and thus a smaller cobalt nanoparticles size than in the case of Red-C-Co5.0AlBEA catalyst.

The goal of this work is to determine an impact of the modification method of Ni/ZrO2 catalyst by alkali and alkaline earth metals on its activity in thermo-chemical conversion of cellulose to hydrogen-rich gas. MexO-ZrO2 supports (where Me = Ca, Mg, Na or K) were prepared by impregnation, precipitation and sol-gel methods. The obtained results reveal that an introduction of dopants to the zirconia support considerably enhances the H2 yield in comparison to unmodified catalyst. An increase in the hydrogen formation is accompanied by a rise in the total volume of the produced gases. It is demonstrated that the highest amount of hydrogen is formed in the presence of the catalysts containing CaO-ZrO2 support followed by Na doped materials. This phenomenon can be attributed to more efficient incorporation of Ca2+ and Na+ cations in the zirconia lattice making it more stable in the reaction conditions. Moreover, it is observed that an activity order of the investigated catalysts is consistent with the changes in the basic character of their surface.

Composite interfaces and interphases are critical regions that dictate the filler-matrix adhesion with an important output in terms of mechanical properties of the composites. Whilst much has been demonstrated with the filler surface modification, the diazonium interface chemistry has rarely been explored in this sense. Herein, zeolite Micro20 was modified with in situ generated diazonium salts from the 2- and 4-aminobenzyl alcohols and characterized by complementary analytical tools. Moreover, the substituent position effect of the CH2OH group is examined with the synthesis of 2- and 4-hydroxymethylbenzenediazonium compounds. Finally, the zeolites having CH2-OH groups were mixed with phenolic resins and the composites were obtained by thermal curing. It is found that the ortho position induces steric hindrance and results in lower extent of surface modification compared to the para-position. Before cure, the resin-filler was found to flow in the case of the ortho position, whereas the para position yields a viscous formulated blend. After cure, the composite shows superior mechanical properties in the case of use in the formulation of the para position. This could be due to two effects: the higher concentration of reactive sites in the para position borne by the filler for reaction towards resins, and ease of reaction between the surface bound groups in the para position with the resin. The ortho position yields less surface bound reactive groups and less efficient reaction with the resins due to steric hindrance. This works highlights subtle position effects of reactive groups employed to fabricate specially surface-modified fillers. It stresses the role of isomer position in the design of high performance composites.

Levulinic acid (LA) is a platform molecule, and its valorization toward biofuel additives like γ-valerolactone or tetrahydrofuran is considered as an important step in planning future biorefinery schemes. In this study, various Ni based catalysts were studied for the LA hydrogenation with formic acid (FA) used as a hydrogen source. Two different ways of catalytic activity improvement are discussed (nickel loading vs addition of dopants). The influence of Ni doping by small amount of noble metals (Pt, Pd, Ru, Rh) showed that Ni–Pd is the most active catalyst. Its high catalytic performance is attributed to the synergic effect between two metals and interaction with chlorine. The effect of chlorine on catalytic performance and properties of the catalysts was evaluated by variety of surface and bulk-sensitive characterization methods. It was shown that addition of chlorine is one of the key factors required for high catalytic performance. Chlorine influences distribution of metals on the surface of the catal...

This work focused on the investigation of the effect of zirconium incorporation into the structure of the Ni/AlSBA-15 catalyst on its performance in high-temperature conversion of cellulose (the main component of lignocellulosic feedstock) to hydrogen-rich gas. The modified supports were prepared by direct incorporation of zirconium and impregnation methods. The obtained results exhibited that introduction of zirconium into the structure of Ni/AlSBA-15 allowed for a considerable increase in the amount of hydrogen produced in the studied process in comparison to unmodified Ni/AlSBA-15 material. The characterization of physicochemical properties of the investigated materials (X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, time-of-flight secondary ion mass spectrometry, temperature-programmed reduction, temperature-programmed desorption of ammonia, etc.) showed that the preparation of mesoporous Ni/ZrAlSBA-15 with the use of the direct synthesis method led to obtaining ...

α, β, γ, and δ polymorphs of 4.6–4.8 eV wide band gap Ga2O3 photocatalysts were prepared via a soft chemistry route. Their photocatalytic activity under 254 nm UV-C light in the degradation of gaseous toluene was strongly depending on the polymorph phase. α- and β-Ga2O3 photocatalysts enabled achieving high and stable conversions of toluene with selectivities to CO2 within the 50–90% range, by contrast to conventional TiO2 photocatalysts that fully deactivate very rapidly on stream in similar operating conditions with rather no CO2 production, no matter whether UV-A or UV-C light was used. The highest performances were achieved on the high specific surface area β-Ga2O3 photocatalyst synthesized by adding polyethylene glycol (PEG) as porogen before precipitation, with stable toluene conversion and mineralization rate into CO2 strongly overcoming those obtained on commercial β-Ga2O3. They were attributed to favorable physicochemical properties in terms of high specific surface area, small mean crystallite size, good crystallinity, high pore volume with large size mesopore distribution and appropriate surface acidity, and to the possible existence of a double local internal field within Ga3+ units. In the degradation of hydrogen sulfide, PEG-derived β-Ga2O3 takes advantage from its high specific surface area for storing sulfate, and thus for increasing its resistance to deactivation and the duration at total sulfur removal when compared to other β-Ga2O3 photocatalysts. So, we illustrated the interest of using high surface area β-Ga2O3 in environmental photocatalysis for gas-phase depollution applications.

International audience; In this work, high surface area mono-and binary oxide materials based on zirconia and titania synthetized via the alginate route were applied as supports of ruthenium catalysts used in levulinic acid hydrogenation towards γ-valerolactone. The physicochemical properties of the catalysts were investigated using surface (like time-of-flight secondary ion mass spectrometry (ToF-SIMS), transmission electron microscopy (TEM)) and bulk techniques (temperature-programmed reduction (TPR), X-ray diffraction (XRD)). The obtained results exhibited that the proposed synthesis method allows for modification of the shape, morphology, and surface properties of the studied materials. These catalysts were tested in levulinic acid hydrogenation, in which catalytic support is known to be crucial. The results revealed that the titania-supported catalyst was the most active in the reaction mentioned above, while the highest mechanical stability was observed for zirconia-supported materials.

The main objective of this work was to evaluate an impact of a support on the efficiency of nickel catalysts in the high-temperature conversion of lignocellulosic biomass to hydrogen-rich gas. The most important parameters influencing catalytic performance of the catalysts were identified. The properties of three materials (ZSM-5, ZrO2, and MCF (mesostructured cellular foam)) used as a support differing in surface acidity, surface area, pore structure, ability to interact with an active phase, and resistance to coking, have been studied. The results revealed that Ni/MCF, characterized by large pore size and pore volume, low acidity, small NiO crystallites size, and moderate interaction with the active phase, is the most efficient among studied catalysts, while an application of Ni on ZSM-5 support with high-acidity was not beneficial. The results suggest that structure of the support, in particular larger pore size and a better contact between an active phase and reaction intermediates, play an important role in the formation of gaseous products during thermal decomposition of lignocellulosic feedstock. On the other hand, high acidity of the support did not increase the formation of large amounts of hydrogen-rich gaseous products.

Fast pyrolysis of Miscanthus, its hydrolysis residue and lignin were carried with a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) followed by online vapor catalytic upgrading with sulfated ZrO2, sulfated TiO2 and sulfated 60 wt.% ZrO2-TiO2. The most evident influence of the catalyst on the vapor phase composition was observed for aromatic hydrocarbons, light phenols and heavy phenols. A larger amount of light phenols was detected, especially when 60 wt.% ZrO2-TiO2 was present. Thus, a lower average molecular weight and lower viscosity of bio-oil could be obtained with this catalyst. Pyrolysis was also performed at different pressures of hydrogen. The pressure of H2 has a great effect on the overall yield and the composition of biomass vapors. The peak area percentages of both aromatic hydrocarbons and cyclo-alkanes are enhanced with the increasing of H2 pressure. The overall yields are higher with the addition of either H2 or sulfated catalysts. This is beneficial as phenols are valuable chemicals, thus, increasing the value of bio-oil. The results show that the hydrolysis residue has the potential to become a resource for phenol production.

A one-step room temperature photo-assisted synthesis has been implemented in liquid phase and under solar light for preparing highly dispersed TiO2 supported metallic Ru catalysts, with no need of final thermal treatment, external hydrogen, or chemical reductant. Whether RuCl3 chloride or Ru(acac)3 acetylacetonate precursor salt was used, sub-nanometric metallic Ru nanoparticles were synthesized on TiO2 with a sharp size distribution, the high dispersion and the metallic nature of the nanoparticles being evidenced by transmission electron microscopy and X-ray photoelectron spectroscopy. However, the use of the chloride salt was proposed to be more suitable for preparing Ru/TiO2 catalysts, due to the lower photodeposition efficiency observed with acetylacetonate, that did not allow to synthesize Ru nanoparticles with a loading higher than 1 wt.%. Different reaction mechanisms have been proposed for explaining the behaviour of both TiO2-salt systems during the Ru nanoparticle synthesis, involving respectively, both holes and electrons charge carriers in oxidation and reduction steps with acetylacetonate, and the sole photogenerated electrons with chloride.

Calcium-modified titania supported Ru catalysts were synthesized and evaluated for the hydrogenation of levulinic acid with formic acid as an internal hydrogen source and water as a green solvent. A new elegant photoassisted method was developed for the synthesis of uniform-size and evenly distributed Ru particles on the titania surface. Compared with the counterpart catalysts prepared by classical wet impregnation, enhanced levulinic acid conversion and γ-valerolactone yield were obtained and further improved through modification of the support by introduction of calcium into the titania support. This synthesis approach resulted in a change of the surface and bulk properties of the support, namely a decrease in the anatase crystallite size and the formation of a new calcium titanate phase. As a consequence, the properties of the catalysts were modified, and smaller ruthenium particles that had stronger interactions with the support were obtained. This affected the strength of the CO adsorption on the catalyst surface and facilitated the reaction performance. The optimum size of Ru particles that allowed for most efficient levulinic acid conversion was established.

International audience; In this work, calcium-modified titania supported Ru catalysts were synthesized and evaluated in the levulinic acid hydrogenation with formic acid as internal hydrogen source and water as green solvent. A new elegant photo-assisted method allowing the synthesis of uniform size and evenly distributed Ru particles on the titania surface was developed. Compared to the counterpart catalysts prepared by classical wet impregnation, enhanced levulinic acid conversion and-valerolactone yield were reached, and further exalted thanks to the support modification via the calcium introduction into the titania support. This synthesis approach resulted in a change of the surface and bulk properties of the support, namely a decrease in the anatase crystallite size and the formation of new calcium titanate phase. In consequence the properties of the catalysts were modified, and smaller ruthenium particles interacting stronger with the support were developed. This affected the strength of CO adsorption on the catalyst surface and facilitated the reaction performance. The optimum size of Ru particles allowing for most efficient levulinic acid conversion was established.

The importance of lignocellulosic biomass, especially used as a feedstock for synthesis of added-value molecules, has not diminished over several decades. The recalcitrant nature of this feedstock has forced scientists to search for new solutions allowing its facile depolymerization. Therefore, in the last decade novel methods of biomass pretreatment or their combinations have been developed. In this chapter we concentrate on the most recent works concerning this topic. The various methods are described and the role of the pretreatment process is explained and discussed.

The pyrolysis of lignocellulosic biomass is one of the most promising methods of alternative fuels production. However, due to the low selectivity of this process, the quality of the obtained bio-oil is usually not satisfactory and does not allow for its direct use as an engine fuel. Therefore, there is a need to apply catalysts able to upgrade the composition of the mixture of pyrolysis products. Unfortunately, despite the increase in the efficiency of the thermal decomposition of biomass, the catalysts undergo relatively fast deactivation and their stability can be considered a bottleneck of efficient pyrolysis of lignocellulosic feedstock. Therefore, solving the problem of catalyst stability is extremely important. Taking that into account, we presented, in this review, the most important reasons for catalyst deactivation, including coke formation, sintering, hydrothermal instability, and catalyst poisoning. Moreover, we discussed the progress in the development of methods leading to an increase in the stability of the catalysts of lignocellulosic biomass pyrolysis and strengthening their resistance to deactivation.

This work was devoted to the investigation of the influence of the surface properties of nickel catalysts supported on different mesoporous silicas on their activity in thermo-chemical conversion of cellulose (the main constituent of lignocellulosic biomass) to hydrogen rich gas. The catalysts containing 20% of Ni introduced by impregnation on SBA-15, SBA-16, KIT-6, MCM-41 and SiO 2 surface were synthesized. The surface properties of the prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), ultraviolet–visible spectroscopy (UV–Vis) and temperature programmed reduction (TPR) methods. Acidity of the catalysts, surface area, pore volume and pore diameter were also determined. The obtained results revealed that an application of the synthesized catalysts to high temperature cellulose conversion process increased the amount of produced hydrogen. A rise in the hydrogen yield was possible owing to the choice of stable catalysts having an optimal combination of surface acidity, surface area, pore volume, pore diameter and localization, and accessibility of nickel crystallites.

This work is focused on the study of the influence of the surface properties of different zirconia supports on the catalytic performance of ruthenium catalyst in hydrolytic hydrogenation of cellulose towards γ-valerolactone. The surface properties of the synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The reaction products were analyzed by high-performance liquid chromatography (HPLC). The obtained results evidenced that the presence of small ruthenium crystallites supported on the tetragonal zirconia phase was beneficial to achieve the highest γ-valerolactone yield in the studied reaction.

An activity and surface properties of nickel catalysts supported on ceria-zirconia used in thermo-chemical conversion of cellulose were studied. The CeO2–ZrO2 (containing 15% and 50% of CeO2) supports were prepared by impregnation, precipitation and sol–gel methods. In the subsequent step 20% of nickel was introduced on their surface by impregnation. The surface properties of the investigated catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR). An acidity and surface area of the studied samples were also determined. The composition of the gaseous products was identified using gas chromatography (GC). The performed studies exhibited that Ni/CeO2–ZrO2 catalysts were efficient in the hydrogen production in the cellulose conversion process and its activity decreased slower than in the case of Ni/ZrO2 sample.

The influence of the nature of carbon materials used as a support for Ru/C catalysts on levulinic acid hydrogenation with formic acid as a hydrogen source toward gamma-valerolactone was investigated. It has been shown that the physicochemical properties of carbon strongly affect the catalytic activity of Ru catalysts. The relationship between the hydrogen mobility, strength of hydrogen adsorption, and catalytic performance was established. The catalyst possessing the highest number of defects, stimulating metal support interaction, exhibited the highest activity. The effect of the catalyst grain size was also studied. It was shown that the decrease in the grain size resulted in the formation of smaller Ru crystallites on the catalyst surface, which facilitates the activity.

The main goal of this work was the evaluation of the effect of modification of zirconia by selected rare earth metals (praseodymium, yttrium and gadolinium) on the activity of nickel catalyst in the high temperature conversion of lignocellulosic biomass to hydrogen-rich gas. An influence of type of dopant, its content and introduction method was studied. The obtained results revealed that the modification of catalysts allowed for noticeable increase the efficiency of hydrogen-rich gas production in the high temperature conversion of lignocellulosic feedstock. The highest activity among studied catalysts was observed for nickel supported on zirconium oxide modified by praseodumium via sol-gel method. The performed experiments (XRD, XPS, TEM, TPR, TPD-NH3, TG-DTA-MS and BET) indicated that an increase in the activity of investigated catalysts can be not only related with larger surface area, pore volume and higher acidity, but also size and location of active phase crystallites, susceptibility of nickel oxide to the reduction and contribution of Pr3+ ions in zirconia lattice.

Ru/TiO2 are promising heterogeneous catalysts in different key-reactions taking place in the catalytic conversion of biomass towards fuel additives, biofuels, or biochemicals. TiO2 supported highly dispersed nanometric-size metallic Ru catalysts were prepared at room temperature via a solar light induced photon-assisted one-step synthesis in liquid phase, far smaller Ru nanoparticles with sharper size distribution being synthesized when compared to the catalysts that were prepared by impregnation with thermal reduction in hydrogen. The underlying strategy is based on the redox photoactivity of the TiO2 semi-conductor support under solar light for allowing the reduction of metal ions pre-adsorbed at the host surface by photogenerated electrons from the conduction band of the semi-conductor in order to get a fine control in terms of size distribution and dispersion, with no need of chemical reductant, final thermal treatment, or external hydrogen. Whether acetylacetonate or chloride was used as precursor, 0.6 nm sub-nanometric metallic Ru particles were synthesized on TiO2 with a sharp size distribution at a low loading of 0.5 wt.%. Using the chloride precursor was necessary for preparing Ru/TiO2 catalysts with a 0.8 nm sub-nanometric mean particle size at 5 wt.% loading, achieved in basic conditions for benefitting from the enhanced adsorption between the positively-charged chloro-complexes and the negatively-charged TiO2 surface. Remarkably, within the 0.5&ndash, 5 wt.% range, the Ru content had only a slight influence on the sub-nanometric particle size distribution, thanks to the implementation of suitable photo-assisted synthesis conditions. We demonstrated further that a fine control of the metal Ru nanoparticle size on the TiO2 support was possible via a controlled nanocluster growth under irradiation, while the nanoparticles revealed a good resistance to thermal sintering.

Calcium-modified titania supported Ru catalysts were synthesized and evaluated for the hydrogenation of levulinic acid with formic acid as an internal hydrogen source and water as a green solvent. A new elegant photoassisted method was developed for the synthesis of uniform-size and evenly distributed Ru particles on the titania surface. Compared with the counterpart catalysts prepared by classical wet impregnation, enhanced levulinic acid conversion and γ-valerolactone yield were obtained and further improved through modification of the support by introduction of calcium into the titania support. This synthesis approach resulted in a change of the surface and bulk properties of the support, namely a decrease in the anatase crystallite size and the formation of a new calcium titanate phase. As a consequence, the properties of the catalysts were modified, and smaller ruthenium particles that had stronger interactions with the support were obtained. This affected the strength of the CO adsorption on the catalyst surface and facilitated the reaction performance. The optimum size of Ru particles that allowed for most efficient levulinic acid conversion was established.

Gamma-valerolactone (GVL) is one of the key products of future biorefineries. We show here for the first time the superior activity of Ni-based, Au doped catalysts in levulinic acid hydrogenation towards GVL using formic acid as a hydrogen source. Their performances are strongly influenced by the preparation method, and the highest GVL yield is achieved for bimetallic Au–Ni catalysts prepared via co-impregnation of both metallic salts with a reductive thermal treatment under hydrogen. The very high catalytic activity is explained by the use of DFT calculations and the extensive characterization of the catalyst surface and bulk properties. We highlight the pivotal role played by the incorporated isolated metallic Ni atoms within Au nanoparticles. The nano-alloy composition is determined. It allows establishment of a surface model of such an alloy, thanks to which the high activity can be explained by the presence of an optimum energetic span of FA adsorption. The existence of strong interaction between Au and Ni in a surface alloy, Au–Ni, favors selective and fast decomposition of formic acid into hydrogen that consequently facilitates strongly the combined hydrogenation process.

This work was devoted to the investigation of the catalytic performance of a Ni catalyst supported on CeO 2 , ZrO 2 and CeO 2 –ZrO 2 in the upgrading of cellulose fast-pyrolysis vapors. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR) were used for the surface characterization of the prepared materials. The activity of the catalysts was evaluated by analytical pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). It was demonstrated that the use of 20%Ni/15%CeO 2 –ZrO 2 allowed one to obtain the highest olefin and paraffin contents, while owing to the application of 20%Ni/ZrO 2 catalyst the largest amount of aromatics was produced and a considerable decrease in the amount of carboxylic acid fraction was noticed.

In this work, an influence of Ni catalyst support on the product distribution in the upgrading of cellulose fast pyrolysis vapors was investigated. The catalysts containing 20% of Ni introduced by impregnation on Al2O3, SiO2, MgO, CeO2 and ZrO2 surface were prepared. In the case, of the zirconium oxide synthesis three different methods of support preparation were applied. The effects of surface acidity, type of the precursor and support preparation method, crystalline phase of the support, interactions between active phase and support, surface area of the catalyst and NiO crystallite size on the distribution of reaction products were studied. Moreover, an impact of CaO addition to the Ni/ZrO2 catalysts was evaluated. The composition of reaction products was identified using Py-GC/MS. The surface properties of the investigated catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR). Acidity and surface area of the catalysts were also determined. The obtained results, revealed that while surface acidity exerts a significant impact on the reaction yield, other factors can also considerably change the distribution of products in the upgrading of vapors from cellulose fast pyrolysis.

Modern analytical methods play an important role in archaeological objects, including ceramics. This review focuses on the use of analytical methods such as: gas chromatography coupled mass spectrometry, Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), powder X-ray diffraction with thermal analysis to study the chemical and mineralogical composition of archaeological samples and organic residues preserved inside. In this paper, special attention was paid to the ToF-SIMS method, which allows the determination of characteristic ions on the surface of ceramic samples.

α, β, γ, and δ polymorphs of 4.6-4.8 eV wide band gap Ga

Hydrogen is considered one of the most promising energy carriers. It can be also used as a reducing agent in numerous industrial processes. One of the main sustainable sources of hydrogen is lignocellulosic biomass. Therefore, this chapter was devoted to the presentation of the methods of the production of hydrogen-rich gas via conversion of this renewable feedstock and its decomposition products. In the first part of the work, high-temperature processes are discussed focusing on the influence of the composition and physicochemical properties of the used catalyst on the H2 yield. Moreover, the studies aiming at modification of the catalyst support are presented. The second part of the chapter covers the issue concerned the production of hydrogen by formic acid decomposition and the application of the obtained H2 for hydrogenation reactions. In this case, the factors that influence formic acid conversion and the types of the used catalysts are showed.

The aim of this work was to determine the surface properties of silica supported cobalt catalyst for Fischer–Tropsch synthesis. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used for this purpose as a main analytical tool. Moreover, X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis/differential thermal analysis/mass spectrometry (TG–DTA–MS) and BET surface area measurements were performed. The influence of a preparation method and treatment conditions on the surface composition (including the formation of different phases of cobalt oxides, cobalt silicate and decomposition of cobalt nitrate – catalyst precursor), cobalt oxidation degree and metal dispersion was studied. 10%Co/SiO 2 catalysts prepared by impregnation and deposition–precipitation methods were investigated. Moreover, pure Co 3 O 4 , CoO and Co powders were used as reference materials.

The aim of this work was to determine changes in the surface composition and structure of different biomass samples submitted to high temperature treatment. Cellulose and lignocellulosic biomass were pyrolysed in a stirred batch reactor under atmospheric pressure at 700 °C for 4 h. The reaction was executed without and in the presence of Ni/ZrO2 catalyst. Different biomass samples and the remaining residues after the pyrolysis were investigated by time-of-flight SIMS, infrared spectroscopy, and SEM. The results of the studies showed an alteration of the surface of materials submitted to high temperature treatment in comparison to untreated specimens. The composition of uppermost layer of biomass samples influenced the reaction yield and was notably different after pyrolysis in the presence of the catalyst. Copyright © 2014 John Wiley & Sons, Ltd.

Hydrogen and syngas from cellulose or cellulosic biomass gasification are environmentally clean gaseous fuels used for power generation. In this work, we explored the potential of several Ni/ZrO2 catalysts for the thermochemical conversion of cellulose to hydrogen. From the investigated catalysts the one consisting of tetragonal zirconia and containing the active phase with a small crystallite size and stable surface area, performed best in the cellulose conversion. Migration of zirconia on the nickel surface was found to be beneficial for catalytic performance. According to the XPS results, the highest Zr/Ni ratio was measured on the tetragonal phase of zirconia, followed by monoclinic ZrO2, with amorphous zirconia showing the lowest migration tendency.

Hydrolytic hydrogenation of cellulose toward fuel additive – γ-valerolactone (GVL) – has been studied, and the catalytic performance of Pt/TiO2 and Ru/TiO2 and reaction conditions were optimized. Additionally, new information about the changes of catalyst surface after the reactions of lignocelulose toward GVL was obtained. Two procedures were investigated: one-pot hydrolysis-hydrogenation and hydrolysis of cellulose followed by hydrogenation in two separate reactions. Spent catalysts were tested by time-of-flight SIMS (ToF-SIMS). Reaction conditions strongly influence the GVL yield, which was much lower during one-pot procedure where much higher carbon deposit and catalyst deactivation was observed by ToF-SIMS and temperature-programmed reduction. Ruthenium catalysts were more active than platinum ones in liquid phase reactions toward GVL, independently of the feedstock. Copyright © 2014 John Wiley & Sons, Ltd.

The application of time-of-flight (ToF)-SIMS to cellulose valorization is described. Cellulose samples subjected to ball milling or sulfuric acid impregnation, or combinations thereof, were subjected to hydrolysis. The material, which was impregnated in the last treatment step, no matter whether previously milled or not, exhibited the highest hydrolysis activity because of the highest accessibility of surface sulfonic groups. When milling followed impregnation, the activity was decreased because of possible encapsulation of sulfonic groups in the bulk. The ToF-SIMS analysis revealed that both the ball mill and the stainless steel reactor may be a source of chromium and iron impurities, which can decrease the hydrolysis yield. Copyright © 2014 John Wiley & Sons, Ltd.

International audience

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was applied for the first time to the surface characterization of carbonaceous material formed during thermochemical conversion of cellulose. Owing to that new information about the composition of solid residue formed in the cellulose pyrolysis was obtained. The use of ToF-SIMS allowed one to demonstrate the differences between the structure of the uppermost layer and subsurface region of the pyrolysed material which were not clear with the use of other analytical methods.

International audience; The catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into [gamma]-valerolactone (GVL) is considered as one of the crucial sustainable processes in today's biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate.