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Nickel metal supported on HZSM-5 (zeolite) is a promising catalyst for lignin depolymerization. In this work, the ability of catalysts prepared via deposition-precipitation (DP) to perform hydrodeoxygenation (HDO) on two lignin model compounds in organic and aqueous solvents was evaluated; guaiacol in dodecane and 2-phenoxy-1-phenylethanol (PPE) in aqueous solutions. All Ni/HZSM-5 catalysts were capable of guaiacol HDO into cyclohexane at 523 K. The role of the HZSM-5 acid sites was confirmed by comparison with Ni/SiO2 (inert support) which exhibited incomplete deoxygenation of guaiacol due to the inability to perform the cyclohexanol dehydration step. The catalyst prepared with 15 wt% Ni, a DP time of 16 h, and a calcination temperature of 673 K (Ni(15)/HZSM-5 DP16_Cal673), performed the guaiacol conversion with the greatest selectivity towards HDO products, with an intrinsic rate ratio (HDO rate to conversion rate) of 0.31, and 90% selectivity to cyclohexane. Catalytic activity and selectivity of Ni/HZSM-5 (15 wt%) in aqueous environments (water and 0.1 M NaOH solution) was confirmed using PPE reactions at 523 K. After 30 min reaction time in water, Ni/HZSM-5 exhibited ~100% conversion of PPE, and good yield of the desired products; ethylbenzene and phenol (~35% and 23% of initial carbon, respectively). Ni/HZSM-5 in NaOH solution resulted in significantly higher ring saturation compared to the Ni/HZSM-5 in water or the NaOH solution control.

The conversion of levulinic acid over rhenium oxide catalysts supported on ZrO2 and SiO2 in a batch reactor at 200 °C and 5 MPa of H2 pressure was studied. The catalysts were prepared by incipient wetness impregnation with nominal loadings of 5–18 wt.%. The catalysts were characterized by N2 physisorption, field emission scanning electron microscopy, X-ray diffraction, H2-temperature programmed reduction, Fourier transform infrared spectroscopy of adsorbed pyridine, and X-ray photoelectron spectroscopy. The catalysts were highly active and selective to γ-valerolactone. Catalytic activity, expressed as initial reaction rate and based on catalyst weight, was correlated with dispersion. The difference in the activity trend was attributed to ReOx-support interaction: ZrO2 interacted more strongly with ReOx and modified the electronic character of the sites, whereas SiO2 interacted weakly with ReOx, leading to unmodified Re active sites, irrespective of Re loading. All the catalysts exceeded 90 % selectivity to GVL.

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.

The effect of Al2O3 modification by CeO2 addition (14 wt.% to obtain a maximum monolayer coverage) on the catalytic activity of three supported Re active phases (Re, ReOx and ReSx) for guaiacol conversion was studied. A 10 wt.% loading of Re was impregnated into CeO2-Al2O3 support and used to prepare the three rhenium active phases by calcination, reduction or sulfidation steps. The catalysts were characterized by different techniques in order to explain the catalytic behavior of the solids studied. The catalysts were then evaluated in a batch reactor at 300 °C and 5 MPa of H2. The characterization results showed that the addition of CeO2 modified the acidity of the support as well as the metal-support interaction, and consequently the catalytic activity. In fact, CeO2 addition doubled the activity of Re and ReSx catalysts in comparison to the corresponding γ-Al2O3-supported catalysts. These results were attributed to a higher dispersion of active sites in the case of metallic Re catalyst and higher concentration of non-stoichiometric sulfur species (ReS2-x) in the case of ReSx catalyst. On the other hand, a similar catalytic activity was observed over the two supported ReOx catalysts, indicating that the role of ReOx active phase on guaiacol conversion outweighs structural and surface modification induced by CeO2 addition. In relation to products distribution, it was observed that CeO2 addition enhanced phenol formation and generally led to higher degree of deoxygenation which is most likely related to decrease in acidity.

The present work evaluates the effect of ethylene content of a carburization mixture on the formation of carburized rhenium supported on activated carbon. The resulting catalysts were characterized by N2 physisorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction, and the results show a strong effect on the final phase obtained. A high amount of ethylene inhibited the carburization process, resulting in carbon formation, while a lower amount (≤ 35 %) of ethylene was favorable to the formation of the carbide phase. The catalysts were evaluated for the hydrodeoxygenation (HDO) of guaiacol, a bio-oil model compound, and a high yield of benzene (50 %), a desirable aromatic compound, was obtained at complete conversion over the catalysts containing the carbide phase.

Commercial carbon nanotubes have been oxidized with HNO3, H2O2 and air and they have been tested on the cyclization of citronellal. The materials have been characterized by N2 adsorption/desorption isotherms, transmission electron microscopy, X-ray diffraction, temperature programmed desorption, potentiometry titration and X-ray photoelectron spectroscopy. The HNO3-treated samples displayed the largest concentration of carboxylic acids which increased by increasing the oxidation time and by a previous ball-milling treatment. The carboxylic acid groups were found to be the active groups on the reaction and the activity increased by increasing its content. The selectivity to isopulegols was higher (98%) over the most active samples (activity 0.20–0.68 mmol/g min), which has been explained by their smaller pore size caused by the oxidation treatment. The stability of the most active CNT sample was also proved by recycling the catalyst in 3 cycles. Financial support for the present study was received from CON-ICYT Chile, project 3130483 (Postdoctoral), Generalitat Valenciana, Spain (PROMETEOII/2014/004) is also gratefully acknowledged.

High surface area (ca. 1700–3400 m2 g−1) activated carbons (ACs) were prepared from Chinese anthracite by chemical activation with KOH using KOH/Anthracite weight ratios (WKOH/WAnthracite) ranging from 1.6 to 5. The photocatalytic degradation of methylene blue (MB) at high concentration conditions up to 25 ppm under UV–vis irradiation was performed on AC and on TiO2-AC mixtures prepared by slurry methodology. The highest values of both BET surface area and of micropore volume to total pore volume ratio were found with a WKOH/WAnthracite ratio of 4. It was found that ACs developed photocatalytic activity and an important synergistic effect with TiO2. TiO2-AC mixtures showed enhancements in the photocatalytic activity up to 6 times higher than commercial TiO2. The photocatalytic activity of ACs and binary materials was discussed with respect to textural properties and surface functional groups of carbons. The ratio of micropore volume to total pore volume and the surface pH of the ACs play important roles upon the photocatalytic activity of TiO2-AC, and the combination of adsorption followed by photodegradation clearly contributed to the treatment of highly concentrated methylene blue. It was concluded that photochemical reactive microporous ACs have a beneficial influence upon the photocatalytic activity of TiO2.

Pd nanoparticles have been synthesized over carbon nanotubes (CNT) and graphite oxide (GO) by reduction with ethylene glycol and by conventional impregnation method. The catalysts were tested on the chemoselective hydrogenation of p-chloronitrobenzene and the effect of the synthesis method and surface chemistry on their catalytic performance was evaluated. The catalysts were characterized by N2 adsorption/desorption isotherms at 77 K, TEM, powder X-ray diffraction, thermogravimetry, infrared and X-ray photoelectron spectroscopy and ICP-OES. It was observed that the synthesis of Pd nanoparticles employing ethylene glycol resulted in metallic palladium particles of smaller size compared to those prepared by the impregnation method and similar for both supports. The presence of oxygen groups on the support surface favored the activity and diminished the selectivity. It seems that ethylene glycol reacted with the surface groups of GO, this favoring the selectivity. The activity was higher over the CNT-based catalysts and both catalysts prepared by reduction in ethylene glycol were quite stable upon recycling. Financial support for the present study was received from CON-ICYT Chile, project 3130483 (Postdoctoral), Generalitat Valenciana, Spain (PROMETEOII/2014/004) is also gratefully acknowledged.

TiO 2 –supported gold samples prepared by deposition-precipitation were tested as catalysts for methanol carbonylation to give methyl acetate at atmospheric pressure in the presence of methyl iodide as cocatalyst. Infrared (IR) spectroscopy was used to investigate the reactions of methanol, CO and CH 3 I on the surface of the samples. The results show the formation of methoxy species bonded to Ti 4+ sites upon adsorption of methanol on the supported gold samples. Admission of CO to the flow reactor/IR cell led to the formation of gold carbonyls, which reacted with the surface methoxy species only when CH 3 I was present to give methyl acetate. The data indicate that CH 3 I is necessary to form gold–acetyl species, which are attacked by neighboring methoxy species to give the carbonylation product. Our results show that the methanol carbonylation catalyzed by TiO 2 –supported gold in the presence of CH 3 I occurs by a reaction mechanism that is similar to that occurring on supported Rh catalysts.

Pt heterogeneous catalysts were prepared by the covalent immobilization of (4′R,5′S)-4′,5′-dihydro-4′,5′-diphenyl-2-(6-cyanopyridyl)imidazoline (PyIm) as the asymmetric modifier. These novel series of catalysts were studied in the 1-phenyl-1,2-propanodione (PPD) hydrogenation. The effects of the PyIm surface concentration, hydrogen pressure, solvent nature and recycles on the reaction were studied. These modified catalysts represent the first effective immobilized chiral non-Cinchona-type modifier of Pt for the enantioselective hydrogenation. The enantio-differentiation was attributed to the substrate–modifier interactions involving hydrogen bonding between the keto-carbonyl O atom and the NH moiety PyIm. The results confirmed that the variations in the H2 pressure and the solvent affect the activity and the enantioselectivity due to the substrate adsorption on the active sites of the metal. Additionally, this heterogeneous catalyst can be conveniently reused at least five times without loss of its catalytic efficiency, but the enantioselectivity decreased, which may be due to the leaching of the modifier., The authors would like to thank CONICYT for their financial support (FONDECYT GRANT 1061001, FONDECYT Initiation GRANT 11121631, FONDECYT postdoctoral 3140130 and 3140157) and the REDOC.CTA doctoral network.

In this report, poly[acrylic acid] gels containing Al2O3 were prepared by simultaneous free-radical polymerization and sol–gel chemistry using different amounts of 3-(trimethoxysilyl)propyl methacrylate (TMPM) as a compatibilizer. The hybrid materials were used as supports for a rhodium catalyst in the chemoselective hydrogenation of 3-substituted aromatic nitro-compounds. The supported rhodium catalyst was prepared by an ion-exchange process. In situ H2 flux was used to produce active species of the catalysts. The resulting materials were characterized by infrared spectroscopy, thermogravimetric analysis, solid-state 29Si and 13C NMR, X-ray diffraction, transmission/scanning electron microscopy, and X-ray photoelectron spectroscopy. All materials exhibited simultaneous interpenetrating hybrid network structures (SIHNs). The morphologies and physicochemical properties depended on the amount of TMPM used. The catalysts were found to be effective for the reduction of nitrobenzene in ethanol at room temperature and a hydrogen pressure of 20 atm. The most active and selective catalyst was used in the hydrogenation of different 3-substituted aromatic nitro-compounds. The hydrogenation reactions displayed high conversion levels and promoted exclusive –NO2 group reduction, resulting in the sole formation of the corresponding amino-compound, with the exception of 1,3-dinitrobenzene, in which over-hydrogenation was detected. The presence of electron-donating/electron-withdrawing substituents at the 3-position resulted in different rates of –NO2group hydrogenation. This effect was quantified in terms of the Hammett relationship, in which the catalyst displayed a linear correlation between the substituent constant (σi) and the hydrogenation rate, with the exception of –OH, –NH2, and –OCH3 groups. One explanation for this behavior is a proposed support-substrate hydrogen bond interaction during the catalytic reaction., The authors thank FONDECYT (grant no. 1110079), FONDECYT (grant no. 1100259), REDOC (MINEDUC Project UCO1202 at U. de Concepción). B.F. Urbano thanks to FONDECYT Initiation (grant no. 11121291) and CIPA CONICYT Regional Project R08C1002. C.H. Campos thanks CONICYT and BECAS CHILE for a postdoctoral fellowship. We also acknowledge the generous support of the National Science Foundation (USA, ER, CHE1049569)

The adsorption and reactions of ethanol on the surfaces of TiO2 and TiO2-supported gold samples were investigated by infrared (IR) spectroscopy and mass spectrometry. IR spectra measured as the samples were treated in flowing ethanol at room temperature indicate that the alcohol was adsorbed both molecularly and dissociatively in the form of ethoxy species bonded to Ti4+ sites. Our results suggest that the presence of neighboring gold particles facilitates cleavage of the β-C H bond of the ethoxy species at increasing temperature, leading to the formation of acetaldehyde linearly bonded to Ti4+ sites, which is readily desorbed. In the process, hydrogen adatoms are recombined on gold particles to give H2. In absence of gold, Ti4+ sites abstract hydrogen atoms from the ethoxy species to give titanium hydride species, which react with hydroxyl groups to produce water and leave oxygen vacancies on the TiO2 surface. Acetaldehyde is formed in the process and it is adsorbed in a bidentate configuration on the oxygen vacancies, where it undergoes reductive coupling to give butene. Our data show that the ability of gold particles to abstract and recombine hydrogen atoms prevents the formation of oxygen vacancies on the support and, in consequence, hinders the subsequent reactions of the produced acetaldehyde.

Molybdenum nitride catalysts supported on activated carbon materials with different textural and chemical properties were synthesized by nitriding supported Mo oxide precursors with gaseous NH 3 or N 2 /H 2 mixtures using a temperature-programmed reaction. The supports and catalysts were characterized by N 2 physisorption, XRD, chemical analysis, TPD, FT-IR and XPS. Guaiacol (2-methoxyphenol) hydrodeoxygenation (HDO) activities at 5 MPa and 300 °C were evaluated in a batch autoclave reactor. Molybdenum nitrides prepared using a N 2 /H 2 mixture resulted in more highly dispersed catalysts, and consequently more active catalysts, relative to those prepared using ammonolysis. The HDO activity was also related to pore size distribution and the concentration of oxygen-containing surface groups of the different carbon supports. Increased mesoporosity is argued to have facilitated the access to active sites while increased surface acidity enhanced their catalytic activity through modification of their electronic properties. The highest activity was thus attributed to the highest dispersion of the unsaturated catalyst species and the highest support mesoporosity. Surprisingly, addition of Co did not improve the HDO activity.

The hydrodeoxygenation of guaiacol (2-methoxyphenol) has been studied in a batch reactor over alumina- and SBA-15 silica-supported molybdenum nitride catalysts at 300 °C and 5 MPa of hydrogen pressure. The catalysts were prepared by nitriding supported Mo oxide precursors with ammonia gas or nitrogen–hydrogen mixtures via temperature-programmed reaction. The alumina-supported catalysts had a higher activity relative to the SBA-15 silica-supported catalysts which was essentially due to catechol production, an effect of the alumina support. The SBA-15 silica-supported catalysts transformed guaiacol directly to phenol by demethoxylation without noticeable catechol production. On both supports, nitridation by ammonolysis increased the activity by a factor of ∼1.1 relative to nitridation by nitrogen–hydrogen. On SBA-15, ammonolysis preferentially produced the γ-Mo 2 N phase while the N 2 /H 2 mixture produced the β-Mo 2 N 0.78 phase. The incorporation of Co led to a marginal improvement in exposed Mo species but generally had a diminishing effect on HDO activity. The lack of catechol production using the SBA-15 silica support is important in minimizing coking reactions and also opens up possibilities for utilizing silica supports with highly controlled pore sizes to possibly influence product distribution in HDO of more diverse feed streams derived from biomass conversion processes.

Fischer–Tropsch synthesis (493 K, 0.62 MPa CO, 1.24 MPa H2) has been performed over monometallic and bimetallic Co and/or Fe clusters deposited on mesoporous silicas (HMS and SBA-15). Catalysts have been prepared by incipient wetness impregnation and characterized by N2 adsorption–desorption isotherms, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), and transmission electron microscopy (TEM). HMS supported Co-Fe catalyst showed the highest activity and C5+ hydrocarbon selectivity, while Co-Fe/SBA-15 catalyst revealed the highest selectivity to alcohols. Both bimetallic catalysts were more active toward the C2–C4 hydrocarbon fraction, with an enhancement in the selectivity to C2 , C3 and 1-C4 olefins. Both bimetallic catalysts showed greater chain growth probability values than the monometallic iron based catalysts although their performance in catalytic tests were more close to the iron catalyst.

The effect of total coverage on alumina is evaluated for Mo 5 V 4 Nb 1 /Al 2 O 3 catalysts by operando Raman-GC spectroscopy during reaction, demonstrating structural changes during reaction that do not occur during catalyst calcination. XRD detects show no appreciable change but Operando Raman-GC studies are sensitive to changes occurring in the nanometer scale, which modulate the performance during propane oxidation, delivering the structure–activity relationship for deactivation. Raman spectra confirm the formation of nanocrystalline MoO 3 -type structures during reaction up to 375 °C, accompanied by coke deposits, able to block the active sites, being detrimental for the acrylic acid formation. Three new catalysts were preparing by the addition of tellurium as dopant, in this case, the presence of MoO 3 is not detected under reaction conditions, since the formation of a distorted rutile structure under reaction conditions is observed, and in this case acrylic acid is obtained as the main reaction product with a yield of ca. 25% at 400 °C.

Much attention has recently been devoted to the surface of bulk catalysts. It has been proved that the most critical phenomena occur at the surface, which differs significantly from the bulk. To evaluate the role of the bulk in VPO catalyst, vanadium and phosphorus were supported on γ-alumina by incipient wetness impregnation at a total V + P of two monolayers so that nanoscaled VPO phases (n-VPO) form on alumina, such size maximizes the surface-to-bulk ratio. Alumina support stabilizes V 5+ , which may be reduced, while V 4+ predominates in bulk vanadyl pyrophosphate phase. In addition, the support modifies acid–base and textural properties. The presence of VPO nanocrystals supported on alumina (n-VPO) facilitates investigating the interaction between alumina-dispersed vanadia and VPO-lattice vanadium ions. Both, bulk and supported phases are active for propane ammoxidation affording acrylonitrile yields of 41% and 48%, respectively, at 500 °C. The yield to acrylonitrile per mass unit of VPO increases by 150% at 500 °C in the alumina-stabilized n-VPO system when compared to the bulk VPO.

The COx-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.

Silica-supported nickel and cobalt phosphide catalysts were synthesized with low metal-loading (5 wt%). The formation of Ni 2 P and CoP phases was achieved by temperature-programmed reduction of phosphite-based precursors, Ni(HPO 3 H) 2 and Co(HPO 3 H) 2 , respectively. The catalysts were characterized by X-ray fluorescence (XRFS), N 2 adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and elemental analysis (CNHS). These catalysts were tested in the individual reactions of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of quinoline (Q), and also in the simultaneous HDS and HDN reactions. These tests were conducted by feeding 3000 ppm of DBT or 3000 ppm of Q. Additional tests were performed with the aim to evaluate S-removal capability by keeping constant Q concentration in the feed (3000 ppm) and varying DBT concentration (200 and 2000 ppm). The catalytic results show that these phosphide catalysts achieve high DBT and Q conversion values at high temperatures though the rate of HDS reaction is higher than that of HDN. In all cases Ni 2 P is more active than CoP. Moreover, the presence of N-containing molecules in the feed does not affect the S-removal as sulfur is almost completely removed after 48 h on-stream.

Heterogeneous photocatalysis using UV-radiation and TiO2 is an interesting method for the treatment of water polluted with organic substances. In this study, volcanic ashes (VA) and nanostructured titania supported over volcanic ashes (TVA) were used as photocatalysts for dye pollutants photodegradation using methylene blue as model molecule. The impregnation of VA with anatase-type TiO2, was carried out using a hydrothermal method. Natural and supported material samples were characterized by N2 adsorption–desorption at 77 K, mercury porosimetry, SEM, X-ray diffraction, XPS and UV–vis and IR spectroscopy. The TiO2-nanostructured material displayed good photocatalyst behaviour compared to a commercially used photocatalyst. The effects of type photocatalyst, pH of solution, catalyst amount and adsorption capacity were studied. In addition, the performance of TVA for dye removal under consecutive operation cycles was also investigated. The high photocatalytic activity and the excellent performance under cycling operation displayed by TVA system make it a good candidate to be considered in engineering applications.

The effect of the sulfiding mixture (H 2 /H 2 S and N 2 /H 2 S) over Re/ZrO 2 and Re/ZrO 2 -sulfated catalysts in the hydrodeoxygenation (HDO) of 2-methoxyphenol (guayacol) in the presence of CS 2 has been studied. The catalysts were prepared by wet impregnation and characterized by X-ray diffraction (XRD), BET surface area, X-ray photoelectron spectroscopy (XPS) and surface acidity techniques. The reaction was carried out in a batch reactor at 300 °C and 5 MPa. Reaction rates for both catalysts increased upon sulfiding in N 2 /H 2 S mixture. This N 2 /H 2 S mixture promotes the formation of ReS (2 − x ) species over support surfaces and leads to an increase in the rate of direct demethoxylation and an enhancement in the phenol/cathecol ratio. An increase in the concentration of CS 2 leads to an increase in the HDO and cathecol and inhibits the demethoxylation of guayacol.

Siliceous MCM-41 with different amount of alumina, from 0.25 up to 4.0 wt%, were prepared by impregnation of the MCM-41 with aqueous solution of Al(NO) 3 ·9H 2 O. The modified mesoporous silicas were then used as supports for Pd catalysts prepared by wet-impregnation from PdCl 2 precursor. Supports and corresponding Pd catalysts were characterized by XRD, XPS and NH 3 -TPD. The catalytic behavior was tested in the hydrodesulfurization (HDS) reaction of thiophene. An increase of the hydrodesulfurization activity with increasing alumina amount up to 0.5 wt% was observed. On the basis of the acidity change of the support and the structural modification underwent by the deposited palladium, the improved catalytic behavior was associated to the increased acidity of the supports and also to its effect on the palladium dispersion. A bi-functional mechanism, implying that metallic palladium activates the hydrogen and the thiophene molecules are adsorbed on the acid sites of the support, could be operative. However, the increased acidity was also responsible for the larger catalyst deactivation which limited the beneficial effect up to a certain amount of alumina content.

The influence of SBA-15 substrate modified with CeO 2 on the catalytic response of supported gold catalysts in the CO oxidation reaction was investigated. The mesoporous CeO 2 /SBA-15 materials (5, 10, 15 and 20 wt% of CeO 2 ) were prepared by incipient wetness impregnation of synthesized SBA-15 substrate whereas the supported gold catalysts were prepared by deposition–precipitation method. The dried Au/SBA-15 and Au/CeO 2 /SBA-15 catalysts were characterized by elemental analysis (EDX), N 2 adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high resolution transmission electronic microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) and their catalytic activity was investigated by the temperature-programmed CO oxidation reaction performed in temperature range 26–205 °C. Catalytic activity was found to increase with the CeO 2 loading even though this increase was not linear: the highest catalytic activity was observed for the catalyst loaded with 10 wt% CeO 2 . This result was explained in terms of the combined effects of the higher stability of gold particles on the support. It was found that the Au nanoparticles in the CeO 2 /SBA-15 substrates could be stabilized more efficiently than those on Ce-free SBA-15 material. For the Ce-containing catalysts, a superior performance of the Au/10%CeO x /SBA-15 catalyst was related to multiple factors such as (i) highest dispersion of Au species on the support surface (by XPS and HRTEM), (ii) highest surface exposure of the Au δ + species (by XPS), and (iii) probably a synergetic effect between the gold nanoparticles and the CeO 2 nanoparticle size (by XRD, UV–vis and HRTEM).

This contribution describes the effect of SBA-15 support modification with variable quantity of TiO 2 (0, 10, 20, 40 and 60 wt%) on the catalytic response of supported gold catalysts in CO oxidation. All gold catalysts were prepared by the deposition–precipitation method. These catalysts were characterized by chemical analysis (ICP), N 2 adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high resolution transmission electronic microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Catalytic activity was found to increase with the TiO 2 loading even though this increase was not lineal: the highest catalytic activity was observed for the catalyst loaded with 10 wt% TiO 2 . This behavior is explained in terms of the quantity of Au + species present on the surface of gold particles. In addition, an Au/TiO 2 reference sample was prepared and tested in CO oxidation reaction. This Au/TiO 2 catalyst exhibited the highest activity due to the higher gold dispersion achieved on the TiO 2 substrate. The importance of both Au + and Au 0 species present on the catalysts surface on the performance in the target reaction is discussed.

Alumina-stabilized nanosized rutile Mo–V–Nb–O oxide phases are prepared, characterized and used for the selective oxidation of propane to acrylic acid. Coverage on alumina support, atomic Mo/V molar ratio and calcination conditions (inert vs. oxidizing) affect the structure and catalytic performance. The effect of Mo/V ratio is opposite depending on calcination atmosphere. Segregated molybdenum oxides are not efficient while partially reduced rutile-type mixed molybdenum–vanadium oxide phases are efficient for the conversion of propane to acrylic acid. Niobium species would have a structural effect, stabilizing mixed molybdenum–vanadium oxide phases.

A series of Co/SiO 2 catalysts containing 10–30 wt.% Co were prepared by wet impregnation and tested in the Fischer Tropsch reaction using a simulated syngas (CO/H 2 ) mixture similar to that obtained in biomass gasification. The catalysts characterization included N 2 adsorption, temperature programmed reduction (TPR), X-ray photoelectron spectra (XPS) and transmission electron microscopy (TEM) techniques. The reaction was carried out in a stainless steel fixed bed reactor at 300 °C and 1 MPa. In general, activity increased almost linearly with increasing Co-loading, reaching maximum at about 20 wt.% Co and then levelled off. These results correlate with that derived from XPS. The Co/Si surface atomic ratios increased almost linearly up to about 20 wt.% Co due to gradual surface coverage by Co species. At higher loadings, cobalt form large crystal aggregates. The selectivity to C 8 –C 9 hydrocarbons increases whereas the C 14+ hydrocarbon follows an opposite trend upon increasing Co-loading. It was also observed that the selectivity to liquid fraction is a function of the Co crystallite size, that is longer hydrocarbons chains are formed on the smaller cobalt crystallites.

This paper reports a study on the effect of the support composition in Pt/Ta 2 O 5 –ZrO 2 catalysts in regard to their catalytic behaviour in the vapour phase selective hydrogenation of crotonaldehyde (2-butenol). Two Ta 2 O 5 –ZrO 2 supports with different Ta/Zr ratios and a pure Ta 2 O 5 were prepared by a sol–gel route. The platinum catalysts were characterized by CO chemisorption, infrared spectroscopy of adsorbed CO and X-ray photoelectron spectroscopy (XPS). The best catalyst in terms of activity and selectivity to crotyl alcohol (2-butenol) was Pt/Ta 2 O 5 , and this behaviour is tentatively related to the metal–support interaction. On the other hand, under the experimental conditions used, the acidic properties of the supports could not be correlated to the catalytic behaviour of these materials.

In this study we report a novel synthesis method for the preparation of silica supported nanosized gold catalysts using HAuCl 4 gold precursor and ammonia solution. Indirect evidences were obtained for the formation of gold ammine cation complexes in the presence of ammonia solution. Urea was also effective for the synthesis of Au/SiO 2 catalysts, but the particle size of supported gold was much larger compared to the samples prepared by using ammonia solution. The results show that the key step of the preparation using ammonia solution is the electrostatic interaction between the positively charged gold precursor and the negatively charged silica surface. The partial dissolution of the silica surface at high pH may provide unique binding sites for the gold complexes, which prevents the particle growth during the treatment in hydrogen at 350 °C and results in highly dispersed gold particles on the silica surface. The new method of synthesis resulted in highly dispersed gold particles on silica with high catalytic activity in carbon monoxide oxidation. XPS and FTIR spectroscopic results show that the gold is in metallic state after hydrogen treatment at 350 °C, while operando FTIR measurements in the presence of oxygen revealed that ionic forms of gold are formed. The formation of these surface entities was strongly hindered over inactive Au/SiO 2 catalyst containing large gold particles.

The catalytic activity of a wood char towards CH 4 decomposition in a pyrolysis gas was investigated in a fixed bed reactor for maximising hydrogen production from biomass gasification. Wood char is suggested to be the cheapest and greenest catalyst for CH 4 conversion as it is directly produced in the pyrolysis facility. The conversion of methane reaches 70% for a contact time of 120 ms at 1000 °C. Because steam and CO 2 are simultaneously present in the pyrolysis gas, the carbon catalyst is continuously regenerated. Hence the conversion of methane quickly stabilises. Such a phenomenon is shown to be possible through the oxidation of the char by CO 2 and H 2 O at high temperature, which prevents the blocking of the mouth of pores by the concurrent pyrolytic carbon deposition. In the experimental conditions, oxygenated functional surface groups are continuously formed (by steam and CO 2 oxidation) and thermally decomposed. The active sites for CH 4 chemisorption and decomposition are suggested to be the unsaturated carbon atoms generated by the evolution of the oxygenated functions at high temperature.

Cobalt-based catalysts doped with different amounts of ruthenium supported on Zr-MSU type materials were studied in the hydrogenation and hydrogenolysis/hydrocracking of tetralin at different temperatures. The catalytic tests were carried out in a high-pressure fixed-bed continuous-flow stainless steel catalytic reactor operating at a pressure of 6.0 MPa. Textural, structural, acidic and metallic properties were studied by XRD, XPS, H2-TPR, NH3-TPD and Elemental Chemical Analysis. Five catalysts were prepared with 10 wt% of cobalt and a ruthenium loading ranging from 0.5 to 5 wt%, along with a monometallic ruthenium catalyst with 3 wt% of metal, for comparison. From catalysts characterization, no interaction between cobalt and ruthenium can be established, however, the presence of ruthenium influences the reducibility of cobalt. Ruthenium-doped catalysts not only improve the catalytic activity of monometallic cobalt and ruthenium ones, but also ruthenium acts as a trap for sulphur organic molecules, preserving cobalt particles from sulphur poisoning and thus maintaining their high hydrogenation activity. The catalyst with a ruthenium loading of 3 wt% is found to be the most active, both, with or without sulphur in the feed. The most striking improvement of ruthenium-doped catalyst properties is their greater resistance to sulphur molecules than in the case of monometallic cobalt catalysts, which are otherwise rapidly deactivated under the same experimental conditions.

CeO 2 –ZrO 2 oxides with different CeO 2 content (1–12 wt%) were prepared by the impregnation method. The effects of CeO 2 content, calcination temperature and interaction between the components on the structure and reductive properties of CeO 2 –ZrO 2 oxides were evaluated by using different techniques such as XRD, DRS, FTIR, Raman, XPS, TGA and TPR. Spectroscopic data showed that the tetragonal phase of zirconia is preserved in all CeO 2 –ZrO 2 oxides, although they retain a high number of defect sites caused by a strong interaction between zirconia and cerium oxide species. An enrichment of the zirconia surface with a fluorite structure of CeO 2 is observed for the CeO 2 –ZrO 2 oxide with the highest CeO 2 content (12 wt%). The samples subjected to consecutive reduction–oxidation cycles at different temperatures showed good redox properties related to the increase of oxygen mobility. It was concluded that these CeO 2 –ZrO 2 oxide systems, displaying high surface and good thermal stability, are similar to chemically mixed oxides due to the strong interaction between the zirconia carrier and deposited ceria.

Two series of alumina-supported molybdenum phosphide (MoP) catalysts with low and high metal loadings were prepared by temperature-programmed reduction of the oxidic catalyst precursors in hydrogen to different temperatures (823, 923, 1023 and 1123 K, respectively). Effects of reduction temperature and metal loading on the surface distribution and the type of species formed were studied by TPR, S BET , XRD, HRTEM, 31 P NMR, 27 Al NMR and in the reaction of dibenzothiophene (DBT) hydrodesulfurization (HDS) performed in a flow reactor at 553 K and total hydrogen pressure of 3.4 MPa. HRTEM and 31 P NMR confirmed formation of MoP phase on all catalysts. The 9.9 wt% Mo catalyst activated at lowest reduction temperature (823 K) was found to be most active among the catalysts studied. The presence of a low amount of Mo 0 species on the surface of this catalyst does not appear to be a drawback for the catalytic activity. The increase in both metal loading (from 9.9 to 15 wt% Mo and from 3.2 to 4.8 wt% P) and reduction temperature (from 823 to 1123 K) was found to be detrimental for HDS activity due to sintering of active phase, and also to decrease in specific area and formation of phosphate species.

The upgrading of an aromatic-rich feedstock (pyrolysis gasoline) has been investigated over bifunctional Pt catalysts in order to evaluate the effect of the support on conversion, selectivity and deactivation. The experiments were conducted in a fixed-bed reactor at a pressure of 5 MPa and 350–450 °C. Pt was incorporated into five acidic supports: MFI, BEA and FAU zeolites, and an amorphous silica-alumina (ASA). Their surface properties and acidity were then assessed by means of several characterization techniques and related with their intrinsic activity–selectivity–deactivation. Using high hydrogen pressure (to minimize catalyst deactivation), we report the suitability of several catalysts for different purposes: Pt/MFI19 catalyst for a steam cracker feedstock production, Pt/BEA catalyst for isoalkane-rich gasoline pool manufacture and Pt/ASA catalyst for severe aromatic reduction while controlling the extent of ring scission. The results of accelerated deactivation experiments under low hydrogen pressure lead to the conclusion that MFI-supported catalysts (Pt/MFI19 and Pt/MFI95) yield less coke, but Pt/BEA deactivates to a lesser extent during hydrogenation.

The partial oxidation of methane over supported (ZrO2, CeO2-ZrO2) rhodium catalysts was investigated at atmospheric pressure. The effect of temperature, CH4/O-2 ratio, catalyst composition and pr ...

The effect of Ni content (1–12 wt%) 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 6 wt%.

Phosphate-containing hexagonal mesoporous silica (P/HMS) materials were used as supports of hydrotreating CoMo catalysts. Two series of catalysts were prepared by sequential and simultaneous impregnation of P/HMS substrates with cobalt and molybdenum salts solutions. Both bulk and surface structures of calcined and sulphided samples were determined by several techniques (SBET, XRD, UV–vis, TPD-NH3, TPR, FTIR of adsorbed NO and pyridine, HRTEM and XPS). The activity of P-containing CoMo catalysts was examined in hydrodesulphurization (HDS) of dibenzothiophene (DBT) and compared to that of a conventional commercial CoMo/Al2O3 catalyst. It was found that the dispersion of oxide and sulphide Co and Mo species depends on the presence of phosphate and also on the sequence of Co and Mo incorporation being co-impregnation more favourable than sequential impregnation. HRTEM analysis of sulphided samples (673 K) showed that larger stacking degree of MoS2 phase and better dispersion of Co and Mo species are achieved by co-impregnation. Activity tests revealed that sequential incorporation of Mo and Co is less effective for S-removal from DBT than co-impregnation. Contrary to sequential impregnation, the presence of P2O5 (up to 1.5 wt.%) on support surface enhanced S removal from DBT on the catalysts prepared by co-impregnation but the selectivity in this reaction was not influenced by phosphate and catalyst's preparation method. A close parallelism between active phase surface exposure and catalytic response was found.

Two series of NiRe catalysts supported on γ-Al2O3 and activated carbon having constant wt.% Re2O3 content (3.51 and 1.97, respectively) and various Ni/Re atomic ratios were prepared to investigate the promoting action of Ni on sulfided Re catalysts in the simultaneous hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of gas oil. The catalysts were characterized using textural analysis, X-ray diffraction, diffuse reflectance spectroscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. On both Ni(x)Re/Al2O3 and Ni(x)Re/C catalysts, the dependence of HDS and HDN activities showed initially an increase and subsequent decrease with increasing Ni content, with optimum Ni/Re atomic ratios of ∼0.94 for Ni(x)Re/Al2O3 catalysts and ∼1.25 for Ni(x)Re/C catalysts. The decline in activity was attributed to a reduction in Re dispersion and a low Ni sulfidation for the alumina-supported catalysts, and to a separate location of Re and Ni on the support surface, as well as to an incomplete Ni sulfidation for the carbon-supported catalysts. The synergetic effect in activity observed between Ni and Re was slightly higher for HDS than for HDN, especially at low reaction temperature (325 °C) and on carbon-supported catalysts. On the basis of these promotional effects on catalytic activities and HDN/HDS selectivity, and the characterization results, the nature of the promotion observed on NiRe supported catalysts was discussed.

Silica–alumina supported nickel catalysts (Ni/ASA) have been modified by the incorporation of electrodonor (Li) or electro acceptor (Pd) elements with the objective of determining the factors controlling the catalyst thioresistance in benzene hydrogenation. The catalysts were tested in benzene hydrogenation (HYD) in the presence of 1-butanethiol (C 4 H 9 SH 5 ppm of S) and in the hydroconversion of pyrolysis gasoline (PyGas) and compared with zeolite NaY-supported ones. In addition, the catalysts were characterized by variety of techniques (XRD, N 2 adsorption–desorption, TPD-H 2 , TPD-NH 3 , CO chemisorption, TPR, XPS, FTIR of adsorbed pyridine, TGA–DTA). It was found that the monometallic Ni/ASA catalyst with 24 wt.% of Ni was the most active among the catalysts studied in both benzene hydrogenation (+S) and hydroconversion of PyGas. The data of catalyst characterization suggests that the concentration of both metal and acid sites govern catalytic activity in both activity tests being the catalyst ability for hydrogen adsorption one of the most important factors to be taken into account. In general, it was found that the S-poisoning of the catalysts increased with an increase of the catalyst reactivity and diminished when “refractory-type” coke deposited on the metal sites inhibited the S-compound adsorption. For PyGas transformation, the importance of Pd promotion of the nickel catalysts was confirmed for both hydrogenation and ring-opening reactions.

The hydrodearomatization of pyrolysis gasoline (PyGas) over bifunctional catalysts, based on noble metals (Pt, Pd, Ir, Ni) supported on a HY zeolite, has been studied in a fixed-bed reactor. The surface structures of the catalysts were determined by CO chemisorption, photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and temperature-programmed desorption of H 2 (H 2 -TPD). Catalyst acidity was assessed by ammonia desorption measured by differential scanning calorimetry (DSC-NH 3 ) and Fourier transform infrared spectroscopy of adsorbed pyridine (FTIR-Py). The kinetic performance and product selectivity of the catalysts were discussed in terms of the data provided by surface characterization techniques. Kinetic interpretation was carried out by using individual step conversion, i.e. hydrogenation and ring-opening. The results under mild ring-opening (MRO) conditions indicate a strong dependence of the hydrogenation activity on the metal used. Operating under severe ring-opening (SRO) conditions, a linear dependency of conversion and n -alkane yield on total acidity of the catalyst was observed.

Mixed oxides La 1− x Ce x NiO 3 ( x = 0, 0.05, 0.4 and 0.7) have been prepared by the citrate method and tested, after reduction activation, in the CO 2 reforming of methane reaction into synthesis gas. The compounds were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), specific surface area measurements, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and temperature-programmed oxidation (TPO). The LaNiO 3 perovskite exhibited activity to methane reforming, but suffered a slow deactivation with time-on-stream. Nevertheless, substitution of the A site metal ion with a tetravalent metal cation (Ce) led to an increase in catalytic activity. Moreover, the insertion of Ce increased the stability of the catalysts with respect to the reforming reaction. The La 0.95 Ce 0.05 NiO 3 catalyst showed the highest activity, with CO 2 conversion of 62% at 1023 K. The XRD and TPR analyses confirmed that at high Ce contents, ceria appears as segregated CeO 2 phase and interferes with the rate of perovskite structure formation, so that NiO and La 2 NiO 4 are produced. As a consequence of the low solubility of cerium oxide, its insertion in the perovskite structure is also possible in the low Ce-content regions. This low amount of cerium incorporated is responsible not only for the enhancement of catalytic performance of the perovskite after its activation by reduction, but also for the inhibition of carbon formation.

The microemulsion technology was used in order to improve the preparation of iron-based catalysts for the CO and CO2 hydrogenation reactions. This technique led to a sample with a higher surface area when compared with a similar solid prepared by conventional precipitation. As a consequence, a higher catalytic activity was obtained. The hydrogenation of carbon oxides was also performed over promoted iron-manganese catalysts. The preparation of these samples by the microemulsion methodology yielded to homogeneous mixed oxides. Manganese-containing catalysts presented a higher activity towards the formation of hydrocarbons, at the same conversion levels, than the iron counterparts. These catalysts were promoted with copper, sodium and potassium. Carbon dioxide conversion was favoured by alkaline addition, especially by potassium, due to the promotion of the water-gas shift reaction. Furthermore, alkaline promotion enhanced selectivity towards long-chain products either in CO2 and CO hydrogenation processes. Addition of copper caused a more facile reducibility of the solids, resulting in a significant increment in both carbon monoxide and carbon dioxide conversion without modifying products selectivity.

A series of silica-supported iron samples has been prepared by the microemulsion technology. The samples were characterized by temperature programmed reduction (TPR), UV–vis spectroscopy, N2 adsorption isotherms, X-ray photoelectron spectra (XPS), SEM and transmission electron microscopy (TEM) microscopy and tested in the carbon monoxide and carbon dioxide hydrogenation reactions. Although all samples have similar composition and metallic loading, the preparation route was crucial for the actual nature of the samples, tuning also their catalytic performance. The main result of the preparation route was the extension of the degree of the interaction between the active phase and the support. As a consequence, samples where a metal–support interaction was promoted showed a lower reducibility and therefore a lower catalytic activity. The addition of Mn, Cu and K promoters improves the catalytic performance in carbon monoxide hydrogenation. The low activity of the samples in carbon dioxide hydrogenation is due to their low reverse water–gas shift activity.

The effect of mechanical–chemical activation (MCA) of Ni(Co)–Mo catalysts, supported on γ-Al 2 O 3 has been studied with respect to their phase composition, structure, catalytic activity and selectivity in the reaction of thiophene hydrodesulphurization (HDS). The mechanical-chemical treatment with a duration of 7 h has been accomplished with a planet-ball mill in air medium. The samples have been characterized by means of XRD, XPS, SEM and TPR prior to and after the MCA. The specific surface area and pore size distribution curves have been determined by recording of N 2 adsorption isotherms using BET method. The obtained results show that the HDS activity of the mechano-chemically-activated catalysts is considerably higher than their activity prior to this type of treatment. The applied mechanical–chemical activation caused a partial amorphization of the active components, deposited on the support, a decrease in the average particle size, separation and partial migration of the supported phase. The activation led to redistribution of the Mo 6+ ions on the surface, whereupon the share of the Mo 6+ ions, involved in the formation of the superficial Ni(Co)–Mo–O phase, became larger.