Hydrothermal stability of Ru/SiO2-C: A promising catalyst for biomass processing through liquid-phase reactions

In this work, structural and morphological properties of SiO2-C composite material to be used as support for catalysts in the conversion of biomass-derived oxygenated hydrocarbons, such as glycerol, were investigated in liquid water under various temperatures conditions. The results show that this material does not lose surface area, and the hot liquid water does not generate changes in the structure. Neither change in relative concentrations of oxygen functional groups nor in Si/C ratio due to hydrothermal treatment was revealed by X-ray photoelectron spectroscopy (XPS) analysis. Raman analysis showed that the material is made of a disordered graphitic structure in an amorphous silica matrix, which remains stable after hydrothermal treatment. Results of the hydrogenolysis of glycerol using a Ru/SiO2-C catalyst indicate that the support gives more stability to the active phase than a Ru/SiO2 consisting of commercial silica

Correlation between Iron Reducibility in Natural and Iron-Modified Clays and Its Adsorptive Capability for Arsenic Removal

The study reports aspects that allowed to correlate structural and redox properties of iron species deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous clays as well as an iron-poor clay chemically modified with Fe(III) salt (ferrihydrite species) were investigated as adsorbents of the arsenate(V) in water. The study, carried out from minerals from abundant Argentinean deposits, was conducted with the aid of different techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), Raman Spectroscopy, ICP-AES (Inductively Coupled Plasma) chemical analysis and Temperature Programmed Reduction (TPR). This last technique allowed to detect availability of iron species in oxidic environment with different structural complexity and to determine active sites, accessible for arsenate(V) adsorption. The effect was observed through temperature dependence of the first Fe(III) reduction step (below 570°C) of iron-oxide species. The sequence of reducibility: ferrihydrite > hydrous oxide (goethite) > anhydrous oxide (hematite) > structural iron in clay was in agreement with the availability of iron active sites for the reducing process as well as for the arsenate adsorption. The important role of very high iron content in original samples was also observed. The chemical activation of iron-poor clay by a simple and feasible modification with Fe(III) solutions promoted the deposition of the ferrihydrite active phase with an increase of 2.81% (expressed as Fe2O3) respect to the original content of 1.07%, constituting an accessible and eco-friendly technological alternative to solve the environmental problem of water containing arsenic.Facultad de Ciencias ExactasCentro de Química InorgánicaInstituto de Recursos Minerale

Selective Photooxidation and Photoreduction Processes at Surface-Modified by Grafted Vanadyl

Titanium dioxide was surface-modified by grafting vanadyl species using vanadyl triisopropoxide as a precursor. The resulting material, (VOx)n/TiO2, was characterized by Raman spectroscopy and photoelectrochemical methods. Photocatalytic oxidation of benzyl alcohol and cyclohexene were used to test oxidation selectivity and 4-nitro-benzaldehyde to assess selective photoreduction. The surface-modified TiO2exhibits an enhanced selectivity to benzaldehyde in the photocatalytic oxidation of benzyl alcohol in an aqueous medium and an increase of cyclohexenol formation in the case of cyclohexene in nonaqueous solvent. The salient result is the 100% selective reduction of the nitrogroup in 4-nitro-benzaldehyde achieved under mild experimental conditions

Pyroclasts of the first phases of the explosive-effusive PCCVC volcanic eruption: physicochemical analysis

The morphology, texture, grain size and other physicochemical characteristics of pyroclastic material from the first phases of the Puyehue-Cordon Caulle volcanic complex (PCCVC) eruption, (Southern Andes, Chile), can be associated to the model recently reported for the magma storage and its ascent conditions. The eruption started June 4th 2011, and the studied volcanic material corresponds to that collected in Argentine territory at different distances from the source, between 4 and 12 June 2011. The explosive-effusive volcanic process of the first days occurred with the simultaneous emplacement of lava flows and the venting of pyroclastic material, ejecting two well differentiated types of particles. The more abundant was constituted by rhyolitic and light color pumice fragments, characterized by a typical vesicular texture, easy fragmentation and absence of occluded crystalline phases. Particles found in minor proportion were dark color, different in shape and texture and rich in Fe and Ti. They seemed to be more effective for the interaction with emitted gases in the upper part of the column, for this reason, they appeared partially covered by condensation products. The ascent conditions of the magma affected its rheological behavior through variations in the degassing, viscosity and fragmentation. On the other hand, distance to the source, depositional time, volcanic evolution and environmental conditions are factors that affect the chemical composition of collected ash. So, the SiO2/FeO ratio not only increases with the distance but also with the deposition time and volcanic activity. The work was done with the aid of several techniques such as a laser-sediment analyzer, X-ray diffraction (XRD), chemical analysis (bulk and surface), SEM microscopy and Raman “microprobe” spectroscopy. On the other hand, the physicochemical behavior of the pyroclastic material allows us to suggest eventual applications

Iron Activation of Natural Aluminosilicates to Remove Arsenic from Groundwater

Low-cost adsorbents constituted by Fe-modified-aluminosilicates (laminar and zeolite type minerals) were developed and characterized to be used in the arsenic removal from groundwater. Iron activation was carried out “in situ” by the synthesis and deposition of mesoporous ferrihydrite. Natural iron-rich aluminosilicate was used as reference. All samples were characterized by X-ray diffraction, Raman spectroscopy, BET N2-adsorption, SEM-EDS microscopy and ICP chemical analysis. Experimental results of arsenic sorption showed that iron-poor raw materials were not active, unlike iron activated samples. The iron loading in all activated samples was below 5% (expressed as Fe2O3), whereas the removal capacity of these samples reaches between 200-700 µg of As by g of adsorbent, after reusing between 17 cycles and 70 cycles up to adsorbent saturation. Differences can be associated to mineral structure and to the surface charge modification by iron deposition, affecting the attraction of the As-oxoanion. On the basis of low-cost raw materials, the easy chemical process for activation shows that these materials are potentially attractive for As(V) removal. Likewise, the activation of clay minerals, with natural high content of iron, seems to be a good strategy to enhance the arsenic adsorption ability and consequently the useful life of the adsorbent.Centro de Química InorgánicaInstituto de Recursos MineralesComisión de Investigaciones Científicas de la provincia de Buenos Aire

Spectroscopic and microscopic characterization of volcanic ash from puyehue-(Chile) eruption: Preliminary approach for the application in the arsenic removal

Volcanic ash from Puyehue Cordon Caulle Volcanic Complex (Chile), emitted from June 4 2011 and deposited in Villa La Angostura at ~ 40 km of the source, was collected and analyzed by Raman spectroscopy, optical and scanning electron microscopy (SEM-EDS) as well as X-ray Diffraction (XRD), surface area (BET) and Chemical analysis (ICP-AES-MS technique). The mineralogical and physicochemical study revealed that the pyroclastic mixture contains iron oxides in the form of magnetite and hematite as well as pyroxene and plagioclase mineral species and amorphous pumiceous shards. Carbonaceous material was also identified. Physicochemical techniques allow us to select two representative samples (average composition and Fe-rich materials) which were used to analyze their performances in the adsorption process to remove arsenic from water. Additional iron activation by means of ferric salts was performed under original sample. Results showed that the low cost feedstock exhibited a good adsorption capacity to remove the contaminant, depending on the iron content and the water pH.Fil: Botto, Irma Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; ArgentinaFil: Canafoglia, Maria Elena. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Gazzoli, D.. Dto de Quimica; ItaliaFil: V. Barone,. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentin

Iron Activation of Natural Aluminosilicates to Remove Arsenic from Groundwater

Low-cost adsorbents constituted by Fe-modified-aluminosilicates (laminar and zeolite type minerals) were developed and characterized to be used in the arsenic removal from groundwater. Iron activation was carried out “in situ” by the synthesis and deposition of mesoporous ferrihydrite. Natural iron-rich aluminosilicate was used as reference. All samples were characterized by X-ray diffraction, Raman spectroscopy, BET N2-adsorption, SEM-EDS microscopy and ICP chemical analysis. Experimental results of arsenic sorption showed that iron-poor raw materials were not active, unlike iron activated samples. The iron loading in all activated samples was below 5% (expressed as Fe2O3), whereas the removal capacity of these samples reaches between 200-700 µg of As by g of adsorbent, after reusing between 17 cycles and 70 cycles up to adsorbent saturation. Differences can be associated to mineral structure and to the surface charge modification by iron deposition, affecting the attraction of the As-oxoanion. On the basis of low-cost raw materials, the easy chemical process for activation shows that these materials are potentially attractive for As(V) removal. Likewise, the activation of clay minerals, with natural high content of iron, seems to be a good strategy to enhance the arsenic adsorption ability and consequently the useful life of the adsorbent.Fil: Botto, Irma Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Química Inorgánica; ArgentinaFil: González, María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Química Inorgánica; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Instituto de Recursos Minerales; ArgentinaFil: Gazzoli, Delia. Universita di Roma La Sapienza. Dipartimento di Chimica; ItaliaFil: Soto, Edgardo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Planta Piloto Multiproposito; Argentin

Preparation, Characterisation, and Photocatalytic Behaviour of Co-TiO2 with Visible Light Response

The preparation of cobalt-modifiedTiO2(Co-TiO2) was carried out by the incipient impregnation method starting from commercialTiO2(Degussa, P-25) and cobalt acetate. XPS data show that cobalt is incorporated as divalent ion, and it is likely present within few subsurface layers. No appreciable change in structural-morphologic properties, such as surface area and anatase/rutile phase ratio, was observed. Conversely, Co addition brings about conspicuous changes in the point of zero charge and in surface polarity. Diffuse reflectance spectra feature a red shift in light absorption that is dependent on the amount of cobalt. The influence of cobalt addition on the performance ofTiO2as a photocatalyst in the degradation of 4-chlorophenol and Bisphenol A is investigated. The results show that the modified oxide presents a higher photoactivity both for illumination with UV-visible (λ>360 nm) and visible light (λ>420 nm;λ>450 nm), and that this enhancement depends on the amount of the added species and on the final thermal treatment in the preparation step. We also show that Co-TiO2is a more active catalyst than pureTiO2for the reduction ofO2in the dark, which is an important reaction in the overall photocatalytic processes

Volcanic ash as reusable catalyst in the green synthesis of 3H-1,5-benzodiazepines

The volcanic ash from the Andes mountain range (Puyehue-Cordon Caulle volcanic complex situated in western South America on the Argentinean-Chilean border) was used as heterogeneous acid catalyst in the suitable synthesis of 3H-1,5-benzodiazepines. The natural ashes were classified according to their particle size to generate the different catalytic materials. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), vibrational spectroscopies (FT-IR and Raman), and textural properties were determined by N2 adsorption (SBET). Potentiometric titration with n-butylamine was used to determine the acidic properties of the catalytic materials. Several 3H-1,5-benzodiazepines were obtained by reaction of o-phenylenediamine and substituted 1,3-diphenyl-1,3-propanedione in solvent-free conditions, giving good to excellent yields of a variety benzodiazepines. The method was carried out in environmentally friendly conditions and it was operationally simple. The volcanic ash resulted in a safe and recyclable catalyst.Fil: Muñoz, Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Pasquale, Gustavo. Universidad Nacional de la Plata. Facultad de Cs.agrarias y Forestales. Centro de Investigacion En Sanidad Vegetal.; ArgentinaFil: Sathicq, Angel Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Romanelli, Gustavo Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentina. Universidad Nacional de la Plata. Facultad de Cs.agrarias y Forestales. Centro de Investigacion En Sanidad Vegetal.; ArgentinaFil: Cabello, Carmen Ines. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; ArgentinaFil: Gazzoli, Delia. Università di Roma; Itali

Estudio de la adsorción de HPOMs sobre alúmino-silicatos naturales modificados para su aplicación en reacciones limpias de oxidesulfurización

Se investiga el grado de interacción y adsorción de Mo a partir de iso y heteropolimolibdatos soportados en alúminoslicatos naturales (caolines y zeolitas) puros y modificados. Se presenta la caracterización y evaluación preliminar de estos sistemas en la reacción de oxidación selectiva de difenilsulfuro con peróxido de hidrógeno. Los minerales fueron sometidos a diferentes pretratamientos fisicoquímicos, para ser utilizados como soportes catalíticos. Con el objetivo de mejorar la adsorción de POMs y HPOMs sobre la superficie del mineral, se funcionalizó la misma con diferentes aminosilanos. Todos los materiales fueron caracterizados por diversas técnicas fisicoquímicas convencionales como DRX, y FTIR y térmicas. Los ensayos de TPR permitieron analizar el tipo de interacción de los HPOMs en cada superficie. La reacción de oxidesulfurización se realizó en “batch” a 75°C, empleando H2O2 como oxidante “limpio” y acetonitrilo como solvente. La mayor adsorción de Mo alcanzó un 11% en la superficie de caolín modificado y funcionalizado y 4% en las zeolitas. Las conversiones de difenilsulfuro obtenidas fueron superiores al 95% en los sistemas conteniendo POMs, con elevada selectividad a difenilsulfona.The degree of interaction and adsorption of Mo is investigated from iso- and heteropolymolybdates supported in pure and modified natural alúminoslicatos (zeolites and kaolins). Also, evaluation of these systems in the reaction of selective oxidation of diphenyl sulfide with hydrogen peroxide is presented. Minerals were subjected to various physico-chemical pretreatments, for use as catalyst supports. With the aim of improving adsorption of POMs and HPOMs on the mineral surface, it was functionalized with different aminosilanes. All materials were characterized by various physicochemical techniques such as conventional XRD and FTIR and thermal analysis. TPR tests helped analyze the type of interaction with HPOMs on every surface. The catalytic tests were performed in batch at 75 °C, using H2O2 as clean oxidant and acetonitrile as solvent. In functionalized systems the amount of Mo adsorbed reached close to 11% for acid metakaolins and 4% for zeolites. Diphenyl sulfide conversions obtained were above 95%, with high selectivity to diphenyl sulfone