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A thorough investigation of two novel hybrid materials, namely, (2,2'-Hbpy)

Intermetallic compounds (IMCs) are interesting materials in the field of heterogeneous catalysis due to their ordered structure and tunable electronic properties. These IMCs can act as precursor to synthesize metal/metal oxide composite catalysts that are more active than just the starting IMCs. In this work, Sm2Co7 and SmCo5 IMCs were used as precursors to prepare highly active and stable Co_SmO, Co_Sm2O3 and Co3O4_Sm2O3 catalysts via controlled modification. Transmission electron microscopy (TEM) demonstrated that Co and Sm2O3 Nano crystallites were formed after the modification of the IMC. IMCs derived Co_SmO and Co_Sm2O3 were stable and active in NH3 synthesis with very low activation energy of 55 and 77 kJ mol−1 respectively. The structural, morphological and surface characterization revealed that a strong metal support interaction existed between Co and Sm2O3 (electronic effect) along with the presence of surface steps and edges of Co nano crystallites (structural effect) that activate the N2 at low temperature (360 °C). Similarly, Co3O4_Sm2O3 derived from the IMC were found to exhibit high CO2 and butane conversion in butane dry reforming at low temperature (550 °C) with excellent stability. The study revealed that the presence of Co3O4 and Sm2O3 active sites in close proximity (geometrical effect) promoted the simultaneous adsorption or activation of butane and CO2. The Co_Sm2O3 and Co3O4_Sm2O3 derived from IMCs exhibited superior catalytic performance in both NH3 synthesis and butane dry reforming compared to similar compositional catalyst synthesized by hydrothermal route. These studies pave the way to potential uses of IMCs as precursors to derive composite metal/metal oxide catalysts that are highly stable and active despite their low surface areas.

Chlorobenzene conversion over vanadia supported catalysts.

Catalytic activity of TiO2, 2%Re–TiO2 and 10%Re–TiO2 in the conversion of carbohydrates into levulinic acid under autoclave conditions was evaluated. These materials were prepared by aerogel method, for the first time to the best of our knowledge, and characterized by XPS, SEM-EDX, DRIFTS, DR UV-vis, Raman, N2 adsorption/desorption isotherms, TGA and XRD. Further, the surface acidity was probed by NH3-TPD and pyridine-FT-IR where it was observed that increasing the amount of rhenium doped into TiO2 led to an increase in the total number of acid sites (Lewis + Brønsted) but with an overall lower strength. The presence of both Brønsted and Lewis acid sites led to the hypothesis that these materials may be well suited for conversion of carbohydrates into levulinic acid. Indeed a levulinic acid yield of 57% was reached over 10%Re–TiO2 for a low mass ratio catalyst to glucose (1 : 5). Moreover, the 10%Re–TiO2 catalyst was reused in the conversion of glucose for four catalytic cycles without a significant loss of the catalytic activity.

TiO2 pillared clay was prepared by intercalation of titan polyoxocation into interlamelar space of an Algerian montmorillonite and used for the photocatalytic degradation of the linuron herbicide as a target pollutant in aqueous solution. The TiO2 pillared montmorillonite (Mont-TiO2) was characterized by X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electronic microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformed infra-red (FT-IR), specific area and porosity determinations. This physicochemical characterization pointed to successful TiO2 pillaring of the clay. The prepared material has porous structure and exhibit a good thermal stability as indicated by its surface area after calcination by microwave. The effects of operating parameters such as catalyst loading, initial pH of the solution and the pollutant concentration on the photocatalytic efficiency and COD removal were evaluated. Under initial pH of the solution around seven, pollutant concentration of 10 mg/L and 2.5 g/L of catalyst at room temperature, the degradation efficiency and COD removal of linuron was best then the other operating conditions. It was observed that operational parameters play a major role in the photocatalytic degradation process. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Understanding the origin and mechanism of the formation of methane from CO2 is important because its formation would be related also to the origin of life on Earth. Both processes seem indissociable. To form methane, CO2 is reduced to CO by hydrogen. The reduction of CO2 might also correspond to the first step allowing the transition from CO2 to organic molecules and then to the first block of life on Earth. In our experiments, we used a natural rock (chromitite) collected from an open mine. The major mineral phase naturally occurring in this sample is magnesiochromite (85–95%) with subordinate serpentine and chlorite (including Cr-bearing chlorite). For the first time, we provide an indisputable experimental proof of the (abiotic) formation of methane on a natural chromitite rock, without any previous pretreatment, in the presence of gaseous CO2 and H2 under low temperature and atmospheric pressure, which are the expected atmospheric environmental conditions that existed on Earth’s crust when methane was formed in Nature. Methane is formed by a heterogeneous catalytic hydrogenation process at low temperature and atmospheric pressure. These results suggest that this transformation also goes on in other natural rocks existing on the surface of Earth, probably with higher efficacity. This means that natural rocks on Earth may contain catalytic sites and play the role of catalysts. The catalytic activity can be assigned to the presence of crystallographic phases and their surface composition, which promote the surface adsorption and transformation of gaseous reactants. The results demonstrate that a natural rock can activate, via heterogeneous catalysis, a very stable molecule such as CO2. The literature demonstrates that N2 can be also activated by the same process suggesting a coherent pathway to explain the formation of organic molecules and amino acids in Nature. In situ catalytic CO2 hydrogenation in natural cavities should be considered as a realistic alternative method for CO2 mitigation. It is supported that catalysis would play an important role in the formation of the first block of life on Earth.

Imparting hydrophobicity to solid acid catalysts is critical to regulating their performances by allowing the creation of a less polar environment and improved partitioning of the reactants. Here we present different approaches for the preparation of silica-based catalysts comprising sulfonic acid (-SO3H) sites and hydrophobic decyl (-C10) chains by either simultaneous or sequential postfunctionalization of an azide-functionalized mesoporous silica platform. This set of hybrid bifunctional catalysts is compared in the model esterification of octanol with acetic acid, and the influence of the preparation methods together with the resulting site spatial distribution is discussed. In parallel, we show that pairing the two functional groups affords a maximum synergistic effect compared to more traditional mixed catalysts with random distributions of acid and hydrophobic functions.

The role of Bronsted and Lewis acid sites at the surface of heteropolyacid-based catalysts was studied in resorcinol alkylation with methyl-tert-butylether. Three sets of catalysts, SiO2/HPW, TiO2/HPW and ZrO2/HPW (where HPW stands for phosphotungstic acid hydrate), synthesized by the hydrolytic sol–gel method were investigated. The surface total acidity was characterized by ammonia chemisorption and thermo-programmed desorption. In addition, infrared analysis of adsorbed pyridine was performed to distinguish between Bronsted and Lewis sites. The resorcinol conversion was correlated to the fraction of Bronsted sites present at the catalyst surface based on the total acidity. The results pointed out the importance of considering both Bronsted and Lewis sites as active players in the mechanism of resorcinol alkylation: Lewis sites have the role of adsorbing the substrate close to the tert-butyl cation, which is formed on Bronsted sites. Resorcinol conversion can be increased to a maximum if the right Bronsted/Lewis ratio is attained at the catalyst surface.

A new composite heterogeneous catalytic system is proposed for the transformation of cheap unsaturated fatty acids into value-added molecules through their oxidative cleavage. The valorization of oleic acid to azelaic and pelargonic ones (which are demanded in pharmacology) is specifically studied. The reaction is efficiently performed with a novel composite catalyst inspired from metal recovery technology, namely Ru species supported on a carbon black that was previously oxidized and then functionalized with polydopamine. Being a polymer with hydroxyl and amine groups polydopamine provides moieties acting as tweezers able to complex Ru species. A representation of this novel composite catalyst is built from its characterization by FTIR, TGA, N2 physisorption TEM and XPS. Using NaIO4 as oxidizing agent in a biphasic system at room temperature the conversion of oleic acid, and selectivity towards pelargonic and azelaic acids, reached around 95% after 3 h. The reaction mechanism is explored by UV–Vis spectrophotometry, ICP elementary analysis and NMR spectroscopy, together with recyclability and hot centrifugation tests. The occurrence of a boomerang mechanism is demonstrated. The solid catalyst is indeed recyclable at least 5 times without activity loss, but at the same time Ru species are shown performing the reaction in homogeneous phase namely in a dissolved state. Actually, polydopamine is confirmed to recover Ru species once the reaction ends, guarantying the recyclability of the catalyst. The composite catalyst therefore combines the advantages of homogeneous and heterogeneous catalysis in the investigated reaction.

Pyrite reactivity with nitrate and nitrite was assessed in long-term batch tests to assess its possible oxidation in anoxic conditions at pH 8.5, at room temperature and atmospheric pressure. This was done in the frame of compatibility studies of nitrate-containing radioactive waste with a pyrite-containing clay host rock for geological disposal. Abiotic pyrite suspensions were prepared under inert atmosphere in 15 mM bicarbonate medium, as this simulates the inorganic carbon and pH conditions in the pore water of Boom Clay, which is a potential host rock for geological disposal in Belgium. Two forms of pyrite powder were used, formed via different genetic pathways and exhibiting a different morphology, namely pyrite obtained by crushing a large crystal cluster and pyrite extracted from Boom Clay by flotation. The reactivity of these two pyrite forms with nitrate and nitrite is reported and compared. Overall, after 2–2.5 years under abiotic conditions and inert atmosphere, no significant reaction between crushed pyrite and nitrate was detected, while a very limited reaction was observed between Boom Clay pyrite and nitrate. Between pyrite and nitrite, which is known to be more reactive than nitrate, a slow reaction took place for both forms of pyrite, with no significantly higher reactivity with the Boom Blay pyrite. The variability between the replicates of Boom Clay pyrite were also larger than for crushed pyrite. Overall, nitrate and nitrite induced a very limited, if any, oxidation reaction of the pyrite powders. These observations are important in assessing the safety of geological disposal of nitrate-containing radioactive waste.

This paper studies the effect of the direct incorporation of ZrO

Shaping is a crucial step to produce technical catalysts that remains as some sort of dark art for catalytic researchers in academia. This contribution discusses aspects concerning the fabrication of technical catalysts based on MnO2 powders aimed for the combustion of hazardous aromatic compounds; namely, benzene and styrene. Both laboratory and pilot plant scale catalytic tests were conducted over tablets and extrudates of the technical catalyst. Key physicochemical properties of these materials; namely, surface area, porosity, crystallinity, and mechanical resistance, were assessed and correlated to the catalytic behaviour. On the one hand, the paper describes the hurdles to be overcome when formulating and testing a technical catalyst whose characteristics must be a good compromise between its physicochemical properties and catalytic behaviour at the pilot plant scale. Furthermore, the importance of adopting adequate security and waste management protocols for testing technical catalysts is highlighted. On the other hand, the following conclusions were drawn from the analysis of results: (i) Between tableting and extrusion, only the latter was found to produce shaped bodies with suitable mechanical resistance for pilot plant scale tests. (ii) Calcination of the fabricated extrudates at temperatures from 500 °C leads to a crystallographic transformation of the MnO2 that had a positive impact on the intrinsic activity of the technical catalyst while favouring its mechanical resistance owing to densification at the expense of a decrease in surface area and enlargement of pore size distribution. (iii) Thanks to pilot plant testing of the catalysts, it was possible to identify a detailed reaction scheme for styrene combustion in which besides the occurrence of oxidation, reactions of hydrogenation, dehydrogenation, ring opening, and isomerization take place by a combination of both surface and free radical mechanisms.

Intermetallic compounds (IMCs) have diverse electronic and geometrical properties to offer. However, the synthesis of intermetallic nanoparticles is not always easy; developing new methodologies th...

In this paper, several TiO2 materials doped with zirconia precursor (0.7, 1.4, 1.6 and 2.0 mol%) were synthesized by an easy aqueous sol-gel synthesis at ambient temperature. This method consists in the peptization of the TiO2 colloid in presence of HNO3. The corresponding pure TiO2 material was also synthesized for comparison. The performances and the physico-chemical properties of these materials were compared to the well-known Evonik P25 photocatalyst. The physico-chemical characterizations showed that nano-crystalline anatase-brookite particles were produced with the sol-gel process, with higher specific surface area than P25 (∼200 m2 g-1 vs. 47 m2 g-1). All samples presented a higher visible absorption than P25. The XPS spectra showed that all the samples were doped with nitrogen and that mixed TiO2–ZrO2 oxide materials were obtained when doping with zirconia precursor. Photoactivity was evaluated through the degradation of p-nitrophenol in water. On the one hand, under UV/visible light, the ZrO2 doping increased the degradation efficiency of the pure TiO2 catalyst due to a better charge separation in the mixed TiO2–ZrO2 oxides. The activity of the sample with the highest dopant content was even higher than the one of P25. On the other hand, under visible light, all samples were much more efficient than P25. This activity shift towards visible range was due to the N-doping of the catalysts, with a slight improvement for the doped ones. Finally, the feasibility of producing films starting from an aqueous suspension of the photocatalyst was assessed on P25, pure TiO2 and the best doped material. The photoactivity of these films, evaluated on the degradation of methylene blue under UV-A light, showed that the sample with the highest dopant concentration had an efficiency 4 times higher than pure TiO2 and 20 times higher than P25.

Nanostructured metal oxides are good candidates for applications in heterogeneous catalysis. Recently our consortium has developed the preparation of such materials by exploiting the redox properties of the non-thermal gliding arc plasma (glidarc) in humid air. This contribution aims at sharing with the community active in the field of heterogeneous catalysis that the glidarc technique is an easy and accessible, but powerful technique with a very bright future that can be used for producing heterogeneous oxide catalysts. Therefore, we present here our most recent achievements in the preparation of titanium, iron and manganese oxide catalysts using glidarc. TiO2 nanorods containing both rutile and anatase phases with improved photocatalytic activity under visible light were obtained by oxidizing Ti3+ ions in aqueous solution with the plasma species. Fe2+ ions exposed to the plasma discharge were transformed into sea-urchin-like porous goethite (α-FeOOH) nanostructures via the consecutive oxidation-hydrolysis processes. The synthesized goethite was mesoporous with a high surface area. Clay supported catalysts were also prepared by depositing the goethite particles on kaolinite. Those catalysts (and their calcination products) were active in heterogeneous Fenton degradation of organic dyes. α-MnO2 nanorods were obtained by a rapid reduction of MnO4− ions after exposing an aqueous solution of potassium permanganate to the plasma discharge.

Pyridine is since a long time used as an infrared (IR) molecular probe to characterize the acidity of solids, in particular of heteropolyacids (HPAs). The latter are metal-oxygen-clusters nowadays widely used in acid catalysis. Indeed, thanks to their exceptionally strong Bronsted acidity, they allow operating chemical reactions under significantly milder conditions than required by conventional catalysts. In the case of H3PW12O40, the most acidic Keggin-type HPA, it is well-known that the exposure to pyridine leads to an unusual IR spectrum. Indeed, the band at about 1540 cm−1 associated to the ν19b pyridinium ring stretch mode is split in two. Up to now, this phenomenon was studied with the only aim of understanding its origin, which was proposed to be a tunneling effect related to a frustrated rotation of the pyridinium cation within the solid bulk of H3PW12O40. Here, we demonstrate for the first time that it can actually be used as an analytical tool, namely to probe the degree of dispersion of supported H3PW12O40 units, a key parameter dictating their catalytic performance. We support H3PW12O40 on TiO2 P25 (hydrophilic) and TiO2 T805 (hydrophobic), so yielding samples with different degrees of dispersion, as qualitatively assessed through X-ray photoelectron spectroscopy. Through in situ Fourier-transform IR spectroscopy upon pyridine adsorption, we show that the ν19b pyridinium vibration band only and systematically splits in the presence of agglomerated Keggin units. More precisely, the higher the fraction of agglomerated Keggin units, the more marked the band splitting. So, the latter appears as a fingerprint of agglomerated H3PW12O40. Furthermore, following an easy treatment, the IR spectra allow quantitatively evaluating the fractions of dispersed vs. agglomerated Keggin units within the samples, which is very difficult to achieve through any other technique.

Self-standing macrocellular titanosilicate monolith foams are obtained using a one-pot sol-gel route and show excellent performance in the epoxidation of cyclohexene. Thanks to the High Internal Phase Emulsion (HIPE) templating method, the materials feature a high void fraction, a hierarchically porous texture and good mechanical strength. Highly dispersed Ti species can be incorporated in tetrahedral coordination the silica matrix. These characteristics allow the obtained ‘SiTi(HIPE)’ materials to reach high catalytic turnover in the epoxidation of cyclohexene. The monoliths can advantageously be used to run the reaction in continuous flow mode.

The transformation of γ-valerolactone (GVL) into levulinic acid (LA) requires the use of bifunctional catalysts allowing the hydrogenation and lactonization steps to occur. The aim of this study is to clarify the role played by both redox (Ru) and acid (Nb) sites of the ruthenium-niobium-silicon mixed oxides catalysts, synthesized by sol-gel route, when this reaction is performed in mild conditions. The catalytic performances of the materials are related to an in-depth morphologic and structural characterization, demonstrating that the interaction between the two metals and their relative amount and dispersion are crucial in determining their activity. The results confirm the hydrogenation-dehydration consecutive reaction network and evidence the possibility to selectively produce either GVL or the intermediate γ-hydroxypentanoic acid by an accurate choice of the catalyst composition.

Titanosilicates (Ti-SiO2) are well-known catalysts for the epoxidation of olefins. Isolated Ti inserted in the silica framework in tetrahedral coordination are the active species. Recently, adjusting the hydrophobic/hydrophilic balance of such catalysts’ surfaces has appeared as a promising tool to further boost their performance. However, adjusting the hydrophobic/hydrophilic balance via a one-pot classical sol-gel generally leads to a decrease in the Ti dispersion and/or collapse of the pore network. To overcome this limitation, hydrophobic mesoporous Ti-SiO2 were here synthesized by aerosol-assisted one-pot sol–gel, which allowed the simultaneous control of their Ti loading, degree of methyl-functionalization, and textural properties. Methyl-functionalization was achieved by a partial substitution of tetraethoxy silane (TEOS) by methyltriethoxy silane (MTES) in different ratios. Solid-state29Si-NMR, FTIR, TGA, and vapor-phase water adsorption showed that methyl moieties were effectively incorporated, conferring a hydrophobic property to the Ti-SiO2 catalysts. ICP-AES, DRUV, XPS, and N2 physisorption demonstrated that Ti dispersion and textural properties were both successfully preserved upon the incorporation of the methyl moieties. In the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant, the hydrophobic Ti-SiO2 showed higher catalytic performance than pristine Ti-SiO2 prepared without MTES. In addition to disentangling the positive effect of adjusting the hydrophobic/hydrophilic balance of epoxidation catalysts on their performance, this contribution highlights the advantages of the aerosol procedure to synthesize mesoporous functionalized catalysts with very high dispersion of active sites.

The effect of adding secondary additives for tableting vanadium‑aluminum mixed-oxides, VAlO, on key physicochemical properties and on the catalytic performance in propane oxidation was investigated. Graphite was used as the primary shaping agent. The secondary additives were MgO, silica, BN, sepiolite, and ZnO. The hardness, fracture strength, and particle shape of the secondary additives were associated to the changes of the mechanical strength and porosity of the tablets. There was a compromise between mechanical strength and loss of mesoporosity and surface area. Meanwhile, the additives did not establish a chemical interaction with the VAlO material. Therefore, the secondary additives may act as co-catalysts during propane oxidation. BN and sepiolite were best for promoting both the reactivity of the catalytic formulations and the production of propene. This promotion may be due to the combination of a redox mechanism over the VAlO phase and to a surface radical mechanism occurring over the active moieties of BN and sepiolite.

We investigated how secondary additives for tableting vanadium-aluminummixed-oxides affect the mechanical resistance, surface chemistry, and catalytic performance inpropane oxidation of tablets based on this material. The secondary additives were magnesium oxide, silica, boron nitride, sepiolite, and zinc oxide while graphite was used as the primaryshaping agent. Our results showed that the changes in mechanical strength and porosity weredirectly related to the softness and ductility of the secondary additive. Overall, we learned thatwhen manufacturing catalyst tablets, there is a compromise between mechanical strength andloss in mesoporosity and surface area. On the other hand, the components of the formulatedtablets did not show signs of establishing a chemical interaction with the vanadium-aluminummixed oxide. Therefore, the effects of the additives that we found on the catalytic performancewere ascribed to the fact that the selected secondary additives may act as co-catalysts duringpropane oxidation. In this sense, boron nitride and sepiolite were best for promoting both thereactivity of the catalytic formulations while showing a better productivity of propene. The datawas interpreted suggesting that the promotion effect may be due to the combination of a redoxmechanism over the vanadium-aluminum mixed oxide phase and to a surface radical mechanismoccurring over the active moieties of these secondary additives.

Mesoporous Ti–SiO2 nanoparticles were prepared under alkaline conditions in the presence of a surfactant and were subsequently converted into a hierarchical micro-/macroporous TS-1 zeolite with large crystal size using steam assisted crystallization. In this procedure, the precursor nanoparticles were used both as macroporous hard template and as Si and Ti sources. The secondary macroporosity is a reminiscence of the nanoparticles which undergo dissolution and recrystallization upon steaming. The obtained catalyst has structural properties comparable to benchmark TS-1. We show that the successful conversion of the amorphous material into a fully crystalline catalyst stands for its excellent catalytic performance in aqueous media. Besides, the combination of large crystal size with a hierarchical pore structure ensures easy catalyst handling and processing without compromising on the catalytic activity.

In the field of heterogeneous catalysis, the successful integration of enzymes and inorganic catalysts could pave the way to multifunctional materials which are able to perform advanced cascade reactions. However, such combination is not straightforward, for example in the case of zeolite catalysts for which enzyme immobilization is restricted to the external surface. Herein, this challenge is overcome by developing a new kind of hybrid catalyst based on hollow zeolite microspheres obtained by the aerosol-assisted assembly of zeolite nanocrystals. The latter spheres possess open entry-ways for enzymes, which are then loaded and cross-linked to form cross-linked enzyme aggregates (CLEAs), securing their entrapment. This controlled design allows the combination of all the decisive features of the zeolite with a high enzyme loading. A chemo-enzymatic reaction is demonstrated, where the structured zeolite material is used both as a nest for the enzyme and as an efficient inorganic catalyst. Glucose oxidase (GOx) ensures the in situ production of H2O2 subsequently utilized by the TS-1 zeolite to catalyze the epoxidation of allylic alcohol toward glycidol. The strategy can also be used to entrap other enzymes or combination of enzymes, as demonstrated here with combi-CLEAs of horseradish peroxidase (HRP) and glucose oxidase. We anticipate that this strategy will open up new perspectives, leveraging on the spray-drying (aerosol) technique to shape microparticles from various nano-building blocks and on the entrapment of biological macromolecules to obtain new multifunctional hybrid microstructures., A spray drying technique is used to prepare hollow zeolite microparticles into which an enzyme can be entrapped. Via this “Lego-like” strategy, we create hybrid heterogeneous catalysts that can run multistep chemo-enzymatic cascade reactions.

AlSBA-15 catalysts possessing Bronsted acid and Lewis acid–base bifunctionalities catalyze the direct arylation of benzyl alcohols to diarylmethanes with an 85% product yield through C–O bond activation. 2 and 4wt%AlSBA-15 catalysts have been synthesised by adopting a simple and efficient post-synthetic metal implantation route. The synthesised catalysts were characterized using XRD, N2 adsorption and desorption, 27Al MAS NMR, XPS, HR-TEM, NH3 and CO2-temperature-programmed desorption (TPD) and pyridine-transmission-FTIR spectroscopy techniques to confirm the existence of Bronsted acid and Lewis acid–base bifunctionalities. Through various control experiments, it is verified that Bronsted acid sites activate the benzyl alcohol and Lewis base sites interact with phenylboronic acid concurrently to accomplish the coupling reaction. In the recyclability study, 4wt%AlSBA-15 preserves its activity and stability up to 5 cycles. The 4wt%AlSBA-15 catalyst unlike homogeneous catalysts does not require additives, long reaction time and expensive metals.

This work presents the synthesis of Me2+ (Co, Mg, Ni and Zn)/Al layered double hydroxides (LDH) with a 3:1 M ratio by the co-precipitation method. Structural characterization and comparison of the series has been achieved using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at 77 K, thermogravimetry measurements (TGA), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), ammonia temperature-programmed desorption (NH3-TPD) and point of zero charge (pHpzc). Batch experiments were performed to analyze the adsorption capacity of the different LDH on diclofenac and salicylic acid, as example of emergent pollutants. The pH, mass of adsorbent, contact time and concentration of pollutant were the parameters used to compare the adsorption performance of the synthesized materials. Samples showed different behavior and the equilibrium was reached at different times, Mg6Al2 and Zn6Al2 showed lower equilibrium times but had higher adsorption capacity. Various adsorption and isotherm equation models were employed to study both the kinetic and equilibrium results and, in general, the removal of diclofenac was greater than that of salicylic acid. 1-Butanol conversion was also used as a means of acidity and basicity characterization and the results were compared with the adsorption performance of the samples in order to explain the results found. A relationship between the amount of pollutants adsorbed and the butenes formed in the dehydrogenation reaction of 1-butanol was found. This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (AEI/MINECO) , and the European Regional Development Fund (ERDF) through project MAT2016-78863-C2-R and the Government of Navarra through projects PI017-PI039 CORRAL. LS thanks Universidad Pública de Navarra for a pre-doctoral grant. AG also thanks Santander Bank for funding through the Research Intensification Program.

In 1-butanol dehydration (gas phase) on a Keggin heteropolyacid (HPA) catalyst, the large size of 1-butanol and its significant hydrophobicity make the bulk-type (also called pseudo liquid-type) catalytic mechanism impossible. This drastically limits the catalytic effect on the surface of the HPA, with an activity lower than what it could be. To overcome this limitation, partially substituted ammonium Keggin acid salts with the formula (NH4)xH3−xPW12O40 were here synthesized. Still maintaining enough acidity for the dehydration reaction, the replacement of some protons of H3PW12O40 with NH4+ increases the hydrophobicity of the crystal matrix and allows 1-butanol to enter the bulk of the salt. This consequently makes the protons inside the solid able to catalyse the reaction. The penetration of 1-butanol in the bulk is demonstrated by a combination of in situ methods (Raman, FTIR and XRD) applied during the pre-treatment of the catalyst and the catalytic reaction. When properly activated the pseudo liquid-type mechanism taking place in (NH4)xH3−xPW12O40 leads to a markedly higher 1-butanol conversion in comparison to the surface-type mechanism which is the only one achieved with the non-modified pristine HPA.

The catalytic combustion of diesel soot is addressed with flexible and structured “paper catalysts”. Two different series of catalysts were prepared either by drip impregnation or by a spray method to deposit a mixture of Co, Ba, and K or a mixture of Co and Ce onto SiO2-Al2O3 ceramic paper matrixes. In every case, CeO2 nanoparticles were added to bind the ceramic fibers. SEM images showed that the impregnation method generated catalytic particles concentrated as large chunks (> 10 μm), mainly at ceramic fiber crossings, whereas the spray method produced smaller catalytic particles (< 1 μm) well distributed throughout the ceramic paper. Besides, Co-Ba-K particles appeared better dispersed on the surface of ceramic fibers than Co-Ce due to the presence of K. Additionally, FTIR spectra showed the formation of O2 2− and O2 − species associated with CeO2 (binder) on the samples containing potassium which gave the Co-Ba-K-ceramic paper good catalytic properties, thus making the Co-Ba-K drop impregnated the best catalyst both considering activity and stability. Successive temperature programmed oxidation (TPO) runs up to 700 °C caused the formation of cobalt silicates in the catalytic ceramic paper prepared by the spray method, as indicated by TPR. The formation of these species was probably favored by the smaller size of cobalt particulates and their higher dispersion in the catalysts prepared by the spray method. This provoked the partial loss of the redox properties of Co3O4. TPR experiments also indicated the formation of BaCoO3 in Ba-containing ceramic paper, which could help in maintaining the catalyst activity after several TPO runs through the capacity of this mixed perovskite-type oxide to trap and release NOx. Fil: Leonardi, Sabrina Antonela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Tuler, Fernando Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Gaigneaux, Eric M.. Université Catholique de Louvain; Bélgica Fil: Debecker, Damien P.. Université Catholique de Louvain; Bélgica Fil: Miro, Eduardo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Milt, Viviana Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina

The gas-phase glycerol (Gly) transformation in the presence of oxygen has been studied on cobalt oxide systems (10 and 20 wt% Co) supported on a synthetic mesoporous aluminium phosphate (AlPO4) calcined at 350 °C, as well as on a binary Co-Al phosphate with a Co content of 10 wt%. Synthetic binary phosphate of Al-M (M = Fe, V) have also been tested. The acidity (number and nature of acid sites) of the solids was determined by pyridine adsorption, whereas the reducibility was determined by H2 TPR. The propene oxidation was employed as a test reaction. The influence of the amount of oxidant agent and the reaction temperature on both the glycerol conversion and the yield to reaction products was studied. The formation of acrylic acid; acetic acid and carbon dioxide was favoured for values of O2/Gly ≥ 2 molar ratio and of temperatures beyond 250 °C. The Co oxide species in the supported systems that were the easiest to reduce (lower H2 desorption temperature) exhibited the highest activity to produce acrylic acid. The formation of acetic acid and carbon dioxide was also promoted, suggesting the participation of the acid sites in addition to redox sites. Among the metals investigated here, Co would form part of the required catalyst for the formation of acrylic acid from glycerol. Based on the identified products in this study, some possible reactions involved in the glycerol transformation into oxidized compounds, have been suggested.

Series of Ni catalysts supported on alumina and mixed xCeO2-Al2O3 oxides with different CeO2 content (1–12 wt%) were prepared by impregnation method. The effect of CeO2 loading on the structure and catalytic properties of supported Ni catalysts in dry methane reforming was studied. The texture, structure and surface properties of the catalysts in their calcined, reduced and used state were studied by using different techniques such as: adsorption-desorption isotherms, XRD, UV–vis DRS, XPS, Raman, H2-TPR, EPR, TPO and TEM. Variation in the electronic environments of the cerium and nickel as a function of the CeO2 content and pretreatment was observed for CeO2-containing Ni catalysts. The couples Ni2+/Nio and Ce3+/Ce4+ were detected in the oxidic, reduced and spent ceria-loaded Ni catalysts. CeO2-containing Ni catalysts exhibited higher activity and stability with time on stream relative to that of alumina-supported Ni. The obvious difference in the behaviors of Ni/xCeO2-Al2O3 and Ni/Al2O3 was related to the difference in their dispersions. Small nanoparticles of 4.7–6.3 nm were observed for CeO2-modified catalysts assuring their high activity and resistance to carbon deposition. The highest activity and stability of Ni catalyst with 6 wt.% CeO2 was due to the higher electron density and accessibility of the active sites caused by the close contact between nickel and cerium species. While, Ni/Al2O3 catalyst exhibited low activity and carbon resistant due to the agglomeration of nickel particles up to 20 nm.

Bio-oils require the elimination of most of the oxygen they contain to stabilize them before their use as fuels. The hydrodeoxygenation (HDO) process consists on eliminating oxygen from the bio-oil at high hydrogen pressures over a solid catalyst. However, catalysts often suffer from prompt deactivation due to extensive coke deposition. Therefore, searching more stable catalysts for HDO is still a challenge for biorefiners. In this work, the HDO of guaiacol as a model compound from bio-oil was carried out in a batch reactor at 523 K, p H2 = 5.5 MPa over potassium modified γ-Al 2 O 3 supported CoMo and NiMo catalysts. Potassium was shown to be an effective activity and selectivity modifier. It led to an increase in the yields to products that may hinder catalysts coking by shifting selectivity from demethylation and methyl substitution reactions to direct C Aromatic OH bond scission and hydrogenation reactions. Changes on selectivity were accompanied by a decrease in guaiacol conversion. The effect produced by potassium was shown to be related to: a reduction in acidity, a decrease in the relative number of Mo species in octahedral coordination, and to an increase in the relative concentration of catalytically inactive NiAl 2 O 4 and CoAl 2 O 4 species. Results of this work contribute to design more stable HDO catalysts from a rather simple modification of conventional hydrotreatment catalysts.

Keggin tungstophosphoric acid (H3PW12O40, HPW) was immobilized onto Santa Barbara Amorphous (SBA-15) type silica to obtain selective catalysts for the resorcinol tert-butylation with methyl-tert-butyl ether. The challenge was to enhance the reaction selectivity to the mono-alkylated product i.e. 4-tert-butylresorcinol at the expenses of other more thermodynamically favored products as the 4,6-di-tert-butylresorcinol. Using HPW@SBA15 catalysts, remarkable selectivity to 4-tert-butylresorcinol was obtained, up to 42% (at 20% of resorcinol conversion). Our finding is that the change in the product distribution was dependent on the catalyst surface chemistry: 4TBR selectivity can be increased adjusting the fraction of Bronsted acid sites versus Lewis ones at the catalyst surface.

Manganese (IV) oxide (MnO2) nanoparticles were synthesized, via a plasma-chemical route by using a gliding arc discharge at atmospheric pressure. α-MnO2 nanorods were obtained from the chemical reduction of KMnO4. The synthesis yield was 96.8% after 4.5 min of exposure of the solution to the plasma. Further increase of the exposure time induced a decrease of MnO2 yield because of its reductive transformation into Mn2+ ions. Particles were characterized by X-ray powder diffraction, scanning electron microscopy, Fourier Transform Infrared spectroscopy, and nitrogen physisorption. The plasma-catalytic properties of the synthesized material were tested in the bleaching of amaranth red (AR). AR bleaching efficiencies of 17 and 44% were respectively obtained when the plasma and plasma-catalyst processes were applied for 30 min with initial pH 10. The influence of the initial pH, and catalyst concentration were investigated: the AR bleaching efficiency increased linearly with the catalyst concentration and increased markedly when the pH of the solution decreased.