Catalytic wet peroxide oxidation of phenol through mesoporous silica-pillared clays supported iron and/or titanium incorporated catalysts.

Catalytic performances of Silica Pillared Clay (SPC) supports synthesized in different silica amounts both from standard SWy-2 clay mineral and Hançili region bentonite rock (HWB), and iron (Fe) and/or titanium (Ti) incorporated SPCs in different combinations were evaluated in various advanced Catalytic Wet Peroxide Oxidation (CWPO) of phenol. Host clay mineral type led to different oxidation performances and metal loading created significant increases in the catalytic performance. CWPO performance of Fe-loaded SPCs was better than Ti-loaded ones, so oxidation parameters for Fe-SPCs were studied in detail. Catalyst amount and rise in temperature increased phenol conversion values significantly, and catalysts were more effective in lower pH reaction medium. Aromatic intermediates such as catechol, hydroquinone and benzoquinone formed at the beginning of oxidation were oxidized to carboxylic acids with an advancing oxidation time. The presence of carboxylic acids such as oxalic and formic acid resulted in relatively low total organic carbon (TOC) conversion values. The highest catalytic activity was obtained with high silica content Fe-SPCs synthesized with both host clays. Complete conversion was nearly achieved within 60 min with an experimental condition of T = 30 °C, pH = 3.7 and catalyst/solution ratio = 2 g/L for SWy-2 based catalyst by applying either CWPO or PCWPO (Photo Catalytic Wet Peroxide Oxidation) techniques. SCWPO (Sono Catalytic Wet Peroxide Oxidation) technique also yielded this value at the same oxidation conditions for HWB based catalyst. TOC conversion values at 240 min oxidation time were determined as 33% and 48% for SWy-2 based catalyst with CWPO and PCWPO techniques, respectively, and 37% for HWB based catalyst with SCWPO technique. SWy-2 based catalyst still retained its performance after 3 cycles.

The High Efficiency of Anionic Dye Removal Using Ce-Al13/Pillared Clay from Darbandikhan Natural Clay.

Natural clay from Darbandikhan (DC) was evaluated in its natural form, after acid activation (ADC), and after pillaring (PILDC) as a potential adsorbent for the adsorption of methyl orange (MO) as a model anionic dye adsorbate. The effect of different clay treatments was investigated using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR), and N2 physisorption analysis. Both acid activation and pillaring resulted in a significant increase in adsorption affinity, respectively. The adsorption favored acidic pH for the anionic dye (MO). The adsorption process was found to follow pseudo-second-order kinetics with activation energies of 5.9 and 40.1 kJ·mol-1 for the adsorption of MO on ADC and PILDC, respectively, which are characteristic of physical adsorption. The adsorption isotherms (Langmuir, Redlich-Peterson and Freundlich) were fitted well to the experimental data. The specific surface area of the natural clay was very low (22.4 m2·g-1) compared to high-class adsorbent materials. This value was increased to 53.2 m2·g-1 by the pillaring process. Nevertheless, because of its local availability, the activated materials may be useful for the cleaning of local industrial wastewaters.

Understanding adsorption selectivity in zirconium-pillared clays for biogas upgradation: the role of metal/clay ratio.

Biogas, as a sustainable energy source, encounters challenges in practical applications due to impurities, notably carbon dioxide (CO2), and nitrogen (N2). This study investigates the effect of metal/clay ratio on the adsorption selectivity of porous zirconium-pillared clay adsorbents for biogas upgradation. Comprehensive analyses including nitrogen adsorption/desorption, X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) were conducted to evaluate the physicochemical properties. Adsorption properties for Zr-pillared clays for biogas components such as CO2, CH4, and N2, at 25 °C under different pressures were investigated. The ideal adsorbed solution theory (IAST) was employed to assess selectivity for three binary gas mixtures (CO2/CH4, CO2/N2, and CH4/N2). Results revealed the substantial impact of Zr/Clay ratio on both adsorption capacity and selectivity of the prepared materials. For instance, the maximum adsorption capacity of gases varies as ZrPILC-4 > ZrPILC-2 > ZrPILC-8 > ZrPILC-1, whereas the adsorption selectivity for CO2/CH4 separation (at 1000 kPa) varies as ZrPILC-1 > ZrPILC-2 > ZrPILC-8 > ZrPILC-4. Interestingly, the ZrPILC-8 with maximum surface area (147 m2∙g-1) did not show maximum adsorption capacity for all the three gases, which was attributed to its lower pore volume, and basal spacing, as compared to ZrPILC-4. Amongst all the pillared samples, the ZrPILC-1 exhibited highest selectivity for all binary mixtures (at 1000 kPa), signifies increased nonspecific interactions due to its lower surface area. Its separation performance, particularly for CO2/CH4 mixture exceeded that of the parent clay by 1.5 times. A significant increase in the working capacity of the prepared samples underscores the efficacy of these pillared materials in separating biogas components. This study provides valuable insights into effects of Zr/clay ratio for developing robust pillared adsorbents, contributing to the advancement of sustainable biomethane production.

Titanium-Pillared Clay: Preparation Optimization, Characterization, and Artificial Neural Network Modeling.

Titanium-pillared clay (Ti-PILC), as one of the most suitable types of porous adsorbents/(photo)catalysts, was prepared from a local type of Iranian clay and titanium isopropoxide. The production process was optimized by changing three operating parameters, including the clay suspension concentration (in the range of 0.5-10% w/v), the H+/Ti ratio (2-8 mol/mol), and the calcination temperature (300-700 °C). The largest specific surface area for the Ti-PILC was about 164 m2/g under the clay suspension of 0.5% w/v, H+/Ti = 6, with a surface area 273% larger than that of the raw clay. The surface areas obtained from more concentrated clay suspensions were, however, comparable (159 m2/g for 3% w/v clay and H+/Ti = 4). An increase in the calcination temperature has a negative effect on the porous texture of Ti-PILC, but based on modeling with artificial neural networks, its contribution was only 7%. Clay suspension and H+/Ti ratio play a role of 56 and 37% of the specific surface area. The presence of rutile phase, and in some cases anatase phase of TiO2 crystals was detected. FTIR and SEM investigations of Ti-PILCs produced under different operating parameters were analyzed.

Removal of p-aminobenzenesulfanilamide from water solutions by catalytic photo-oxidation over Fe-pillared clay.

The catalytic photo-oxidation of p-aminobenzenesulfanilnamide (ABS) with hydrogen peroxide in the presence of Fe-pillared clay as heterogeneous catalyst has been investigated under UV-irradiation (λmax = 254 nm). Fe-pillared clay was synthesized by intercalating the iron polyhydroxycomplexes into the interlayer space of a natural layered aluminosilicate - montmorillonite and a subsequent heat treatment at 500 °C. The catalyst was characterized by chemical analysis, low temperature nitrogen adsorption and XRD. The kinetics of photocatalytic oxidative degradation of ABS in aqueous solutions under various experimental conditions was studied. The dependence of the photo-oxidation rate on such experimental factors as pH, hydrogen peroxide concentration and catalyst content was established. The conversion of ABS was 100% and the mineralization efficiency was 52.3% at optimal conditions. The intermediate products of ABS photo-oxidation identified by HPLC were a sulfanilic acid, benzenesulfonamide, benzenesulfonic acid, hydroquinone, pyrocatechol, benzoquinone and aliphatic acids. Fe-pillared clay remained highly active in three consecutive catalytic cycles without regeneration. The results of the study suggested that the heterogeneous photo-system «Fe-pillared clay/H2O2/UV¼ was effective in the oxidative degradation of aminobenzenesulfanilnamide. This system may be of interest for use in organic wastewater treatment processes.

Iron and molybdenum mixed oxide supported on Al-PILC for the catalytic oxidative desulfurization of dibenzothiophene in simulated diesel fuel.

In this work, three novel catalysts were prepared by 2.5, 5.0, and 10.0 wt.% facile impregnation with an iron and molybdenum mixed oxide (Fe/Mo) on an aluminum pillared clay (Al-PILC) support. These materials were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), temperature programed reduction (TPR), and nitrogen (N2) physisorption at 77 K. Characterizations indicated that the metal particles were dispersed on the surface of the three catalysts, and the interlayer d001 spacing of the pillared material remained unchanged after the impregnation process. The catalytic tests showed good results for DBT oxidation using the synthesized catalysts, with high turnover frequency (TOF) values, particularly for the material with 5.0 wt.% Fe/Mo. Theoretical calculations were carried out at the density functional theory (DFT) level, to investigate how the DBT molecules were adsorbed onto the surface of the mixed oxide. The lowest energy proposal was obtained when both Fe and Mo were present at the active sites, indicating a possible synergistic effect of the metals on catalyst activity. Reuse tests indicated that the catalysts could be employed effectively for up to 3 cycles in a row, then a decrease in activity occurred and the active sites needed to be regenerated.

Study of Catalytic Combustion of Chlorobenzene and Temperature Programmed Reactions over CrCeOx/AlFe Pillared Clay Catalysts.

In this study, both AlFe composite pillaring agents and AlFe pillared clays (AlFe-PILC) were synthesized via a facile process developed by our group, after which mixed Cr and Ce precursors were impregnated on AlFe-PILC. Catalytic combustion of organic pollutant chlorobenzene (CB) on CrCe/AlFe-PILC catalysts were systematically studied. AlFe-PILC displayed very high thermal stability and large BET surface area (SBET). After 4 h of calcination at 550 °C, the basal spacing (d001) and SBET of AlFe-PILC was still maintained at 1.91 nm and 318 m²/g, respectively. Large SBET and d001-value, along with the strong interaction between the carrier and active components, improved the adsorption/desorption of CB and O2. When the desorption temperatures of CB and O2 got closer to the CB combustion temperature, the CB conversion could be increased to a higher level. CB combustion on CrCe/AlFe-PILC catalyst was determined using a Langmuir⁻Hinshelwood mechanism. Adsorption/desorption/oxidation properties were critical to design highly efficient catalysts for CB degradation. Besides, CrCe/AlFe-PILC also displayed good durability for CB combustion, whether in a humid environment or in the presence of volatile organic compound (VOC), making the catalyst an excellent material for eliminating chlorinated VOCs.

MS2 coliphage inactivation by Al/Fe PILC-activated Catalytic Wet Peroxide Oxidation: multiresponse statistical optimization.

The optimization of the Catalytic Wet Peroxide Oxidation (CWPO) assisted by an Al/Fe-pillared clay (Al/Fe-PILC) was assessed in the inactivation of the MS2 coliphage in the presence of a synthetic surrogate of natural organic matter (NOM). The simultaneous effect of two experimental factors (i) H2O2 dose - (H2O2)d (3.00-25.50 % of the H2O2 theoretically required for full mineralization) and (ii) catalyst concentration (0.33-2.60 g/L), and four non-controllable variables (covariates) (a) circumneutral pH (6.00-9.00), (b) temperature (5.00-25.0 °C), (c) synthetic NOM concentration (2.0-20.0 mg C/L) and (d) MS2 titer (104, 105 and 106 PFU/mL) was investigated by Response Surface Methodology (RSM). Every response was modeled and maximized: (1) MS2 inactivation, (2) fraction of reacted H2O2, (3) decolourization and (4) NOM mineralization. Multi-response optimization via desirability function based on responses (1) to (3) achieved excellent fitting (0.94 out of 1.0) and following set of optimal experimental conditions: 0.33 g Al/Fe-PILC/L, 3.36 % (H2O2)d â€‹(Feactive/H2O2) = 0.46, giving rise to 92.9 % of MS2 inactivation and 100 % of reacted H2O2 at pH 7.07, 25.0 +/- 0.1 °C, 16.06 mg C/L as starting NOM concentration, and MS2 titer of 106 PFU/mL after just 70 min â€‹of reaction.

(Ce-Al)-oxide pillared bentonite: A high affinity sorbent for plutonium.

The ability of bentonite and montmorillonite pillared by Al-oxide and mixed (Ln-Al)-oxides (Ln = La, Ce) to remove 239plutonium solution species from water is comparatively investigated at pH 7 and pH 4. Small-angle scattering and neutron contrast variation with H2O/D2O mixtures is used to verify the ingress of water in the calcined products after hydrophilicity was introduced by an NH3-H2O vapor treatment. The size and shape of the (La/Ce)-Al oxo-hydroxy pillaring cations (2 nm spheres) is determined by small-angle x-ray scattering from the pillaring solutions. Not all of the oxide pillars improved Pu uptake compared with sodium montmorillonite. At neutral and acidic pH only (Ce-Al)-oxide pillared clays showed the ability to remove Pu over the concentration range studied (1.35 × 10-8-8 × 10-8 mol dm-3) with distribution coefficient (KD) values >104. XPS analysis of the (Ce-Al)-oxide pillared clays indicates the presence of Ce4+ as cerium dioxide. The progressive improvement in sorption performance in the order of pillar type Al2O3 < La2O3-Al2O3 << CeO2-Al2O3 reflects the increasing access of Pu solution species to the clay mineral layers by changes to the basal spacing and specific surface area, and also to the higher stability of the (Ce-Al)-oxide pillars.

Treatment of Methylene Blue and Methyl Orange Dyes in Wastewater by Grafted Titania Pillared Clay Membranes.

BACKGROUND: Amphoteric membranes such as Titania Pillared Clay (TiPILC) membranes exhibit different charges at different pH ranges, subsequently show efficient separation for cationic and anionic organic pollutants in wastewater based on solution pH. The structural properties of such membranes determine their permeability and selectivity to a large extent. The present work is initiated to explore the possibility of enhancing the surface area of TiPILC membranes by grafting with 3- aminopropyltriethoxysilane. METHOD: Grafted TiPILC membranes were fabricated by colloidal sol- gel route followed by dip coating, drying and sintering the membranes at 300°C. X-ray diffraction (XRD) spectra of the pillared photocatalyst membranes show the presence of only anatase phase, which exhibits better photocatalytic activity. Fourier Transform Infrared (FT-IR) spectra reveal the formation of delaminated TiPILC material. The specific surface area of TiPILC membrane obtained at pH3.5 is 183m2/g. RESULTS: Literature survey of 47 papers was carried out for the work. 10 papers were based on patents being dealt on degradation of organic dyes in wastewater by conventional methods, though reports of membrane technology are limited in literature. The rest 37 papers outlined the importance of widespread use of titania photocatalyst powder for degradation studies. CONCLUSION: The membrane material thus developed is efficient in complete decolouration of both Methylene Blue and Methyl Orange dyes on account of the high surface charge and high surface area in just one cycle of filtration.

Preparation of Al/Fe-Pillared Clays: Effect of the Starting Mineral.

Four natural clays were modified with mixed polyoxocations of Al/Fe for evaluating the effect of the physicochemical properties of the starting materials (chemical composition, abundance of expandable clay phases, cationic exchange capacity and textural properties) on final physicochemical and catalytic properties of Al/Fe-PILCs. The aluminosilicate denoted C2 exhibited the highest potential as starting material in the preparation of Al/Fe-PILC catalysts, mainly due to its starting cationic exchange capacity (192 meq/100 g) and the dioctahedral nature of the smectite phase. These characteristics favored the intercalation of the mixed (Al13-x/Fex)7+ Keggin-type polyoxocations, stabilizing a basal spacing of 17.4 Å and high increase of the BET surface (194 m²/g), mainly represented in microporous content. According to H2-TPR analyses, catalytic performance of the incorporated Fe in the Catalytic Wet Peroxide Oxidation (CWPO) reaction strongly depends on the level of location in mixed Al/Fe pillars. Altogether, such physicochemical characteristics promoted high performance in CWPO catalytic degradation of methyl orange in aqueous medium at very mild reaction temperatures (25.0 ± 1.0 °C) and pressure (76 kPa), achieving TOC removal of 52% and 70% of azo-dye decolourization in only 75 min of reaction under very low concentration of clay catalyst (0.05 g/L).

Effects of flue gas components on removal of elemental mercury over Ce-MnOx/Ti-PILCs.

The adsorption and oxidation of elemental mercury (Hg(0)) under various flue gas components were investigated over a series of Ce-MnOx/Ti-PILC catalysts, which were synthesized by an impregnation method. To discuss the mechanism, the catalysts were characterized by various techniques such as N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) analysis and X-ray photoelectron spectroscopy (XPS). The results indicated that the presence of 500 ppm SO2 in the flue gas significantly restrained the Hg(0) adsorption and oxidation over 6%Ce-6%MnOx/Ti-PILC due to the formation of SO4(2-) species. Hg(0) could be oxidized to HgCl2 in the presence of HCl, because the Deacon process occurred. NO would react with active oxygen to form NO2-containing species, which facilitated Hg(0) oxidation. While the presence of NO limited the Hg(0) adsorption on 6%Ce-6%MnOx/Ti-PILC due to the competitive adsorption of NO with Hg(0). The addition of NH3 in the flue gas significantly restrained Hg(0) adsorption and oxidation, because the formed NH4(+) species covered the active adsorption sites on the surfaces, and further limited Hg(0) oxidation. However, when NO and NH3 were simultaneously added into the flue gas, the Hg(0) oxidation efficiency of 6%Ce-6%MnOx/Ti-PILC exhibited a relatively high value (72%) at 250°C, which indicated the practicability to use Ce-MnOx/Ti-PILC for Hg(0) removal under SCR conditions.

Structural and thermal properties of inorganic-organic montmorillonite: Implications for their potential environmental applications.

Inorganic-organic clays (IOCs), clays intercalated with both organic cations such as cationic surfactants and inorganic cations such as metal hydroxy polycations have the properties of both organic and pillared clays, and thereby the ability to remove both inorganic and organic contaminants from water simultaneously. In this study, IOCs were synthesised using three different methods with different surfactant concentrations. Octadecyltrimethylammonium bromide (ODTMA) and hydroxy aluminium ([Al13O4(OH)24(H2O)12](7+) or Al13) are used as the organic and inorganic modifiers (intercalation agents). According to the results, the interlayer distance, the surfactant loading amount and the Al/Si ratio of IOCs strictly depend on the intercalation method and the intercalation agent ratio. Interlayers of IOCs synthesised by intercalating ODTMA before Al13 and IOCs synthesised by simultaneous intercalation of ODTMA and Al13 were increased with increasing the ODTMA concentration used in the synthesis procedure and comparatively high loading amounts could be observed in them. In contrast, Al/Si decreased with increasing ODTMA concentration in these two types of IOCs. The results suggest that Al-pillars can be fixed within the interlayers by calcination and any increment in the amount of ODTMA used in the synthesis procedure did not affect the interlayer distance of the IOCs. Overall the study provides valuable insights into the structure and properties of the IOCs and their potential environmental applications.

Preparation of ZrO2/Al2O3-montmorillonite composite as catalyst for phenol hydroxylation.

Zirconium dispersed in aluminum-pillared montmorillonite was prepared as a catalyst for phenol hydroxylation. The effects of varying the Zr content on the catalyst's physicochemical character and activity were studied with XRD, BET surface area analysis, surface acidity measurements and scanning electron microscopy before investigating the performance for phenol conversion. The zirconia dispersion significantly affects the specific surface area, the total surface acidity and surface acidity distribution related to the formation of porous zirconia particles on the surface. The prepared samples exhibited excellent catalytic activity during phenol hydroxylation.

Synthesis of magnetic FexOy@silica-pillared clay (SPC) composites via a novel sol-gel route for controlled drug release and targeting.

Novel magnetic silica-pillared clay (SPC) materials with an ordered interlayered mesopore structure were synthesized via a two-step method including gallery molecular self-assembly and sol-gel magnetic functionalization, resulting in the formation of FexOy@SPC composites. Small-angle XRD, TEM and N2 adsorption-desorption isotherms results show that these composites conserved a regular layered and ordered mesoporous structure after the formation of FexOy nanoparticles. Wide-angle XRD and XPS analyses confirmed that the FexOy generated in these mesoporous silica-pillared clay hosts is mainly composed of γ-Fe2O3. Magnetic measurements reveal that these composites with different γ-Fe2O3 loading amounts possess super-paramagnetic properties at 300K, and the saturation magnetization increases with increasing Fe ratio loaded. Compared to the pure SPC, the in vitro drug release rate of the FexOy@SPC composites was enhanced due to the fact that the intensities of the SiOH bands on the pore surface of SPC decrease after the generation of FexOy. However, under an external magnetic field of 0.15T, the drug release rate of the FexOy@SPC composites decreases dramatically owing to the aggregation of the magnetic FexOy@SPC particles triggered by non-contact magnetic force. The obtained FexOy@SPC composites imply the possibility of application in magnetic drug targeting.

Synthesis and characterization of TiO2 pillared montmorillonites: application for methylene blue degradation.

TiO2 pillared clay composites were prepared by modifying of montmorillonite (Mt) with cetyl-trimethyammoniumbromide (CTAB) and then using an acidic solution of hydrolyzed Ti alkoxide to intercalate into the interlayer space of the organic modified Mt. The as-prepared materials were characterized by XRD, FTIR, TEM, SEM TG-DTA, specific surface area and porosity measurements. The composites had a porous delaminated structure with pillared fragments and well dispersed TiO2 nanoparticles. Introduction of CTAB into the synthetic system accelerated the hydrolysis and condensation of the Ti source, which promoted TiO2 formation. In addition, the CTAB also significantly increased the porosity and surface area of the composites. A number of anatase particles, with crystal sizes of 5-10 nm, were homogenously distributed on the surface of the Mt as the result of the templating role of CTAB. The resultant TiO2 pillared Mt exhibited good thermal stability as indicated by its surface area after calcination at 800°C. No phase transformations from anatase to rutile were observed even under calcination at 900°C. The grain size of the anatase in prepared sample increased from 2.67 nm to 13.42 nm as the calcination temperature increased from 300°C to 900°C. The photocatalytic performance of these new porous materials was evaluated by using methylene blue degradation. The composite exhibited better photocatalytic property than P 25. The maximum removal efficiency of this composite was up to 99% within 60 min.

Evaluación de aggunas variables en la síntesis e arcillas pilarizadas y su imppacto en la oxidación de fenol en medio acuoso diluido / Evaluation f somme variable in the pillared clays synthesis and their impaact on the phenol oxidation in dilute qqueous / Avalação de alguumasvariáveis na síntese de argilas com pilares e sseu impacto sobre a oxidação de fenol em meio aquoso illuído

Distintas variables de síntesis se evaluaron en la modificación por pilarización de dos arcillas esmectíticas con soluciones mixtas de Al-Fe-Ce. El efecto del ultrasonido durante la intercalación de las especies pilarizantes, el tipo de arcilla y la remoción de los óxidos de hierro del mineral natural fueron determinantes en la obtención de materiales activos en la oxidación de fenol en medio acuoso diluido con una buena selectividad a CO2 en condiciones experimentales moderadas (20 °C y presión atmosférica). Los sólidos fueron caracterizados por difracción de rayos X (DRX), fluorescencia de rayos X (FRX), reducción a temperatura programada de hidrógeno (RTP-H2) y microscopía electrónica de barrido (SEM), evidenciando una modificación estructural exitosa en todos los materiales. Con el empleo del ultrasonido se logró la modificación de los sólidos en un tiempo considerablemente menor (20 min.) al proceso tradicional (24 h), conservando las propiedades físico-químicas y catalíticas de los materiales. Igualmente, se evidenció un efecto de la naturaleza de la arcilla de partida sobre las propiedades químicas y catalíticas del material, así como una mejora al remover los óxidos de hierro del material natural, logrando sólidos con mejor actividad catalítica.

Different variables in synthesis were evaluated in the modification of two pillared smectite clays with mixed solutions of Al-Fe-Ce. The effect of ultrasound during the intercalation of pillaring species, the clay type, and the iron oxides removal of natural mineral were analyzed to obtain active materials in the phenol oxidation in aqueous diluted with a good selectivity to CO2 through moderate experimental conditions (temperature 298K and atmospheric pressure). The solids were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), hydrogen temperature programmed reduction (TPR-H2), and scanning electron microscopy (SEM), showing a successful structural change in all materials. The use of ultrasound allows modifying solids considerably in less time (20 min) than the traditional process (24 hours) maintaining the physicochemical and catalytic properties of the materials. Likewise, evidence of effect of the nature of the starting clay on the chemical and catalytic properties of the material, as well as an improvement by removing iron oxides of natural materials, achieving solids with best catalytic activity.

Diferentes variáveis de síntese foram avaliadas na modificação por pilarização de duas argilas esmectíticas com soluções mistas de Al-Fe-Ce. O efeito do ultrassom durante a intercalação das espécies pilarizantes, o tipo de argila e a remoção dos óxidos de ferro do mineral natural foram determinantes na obtenção de materiais ativos na oxidação de fenol em meio aquoso diluído com uma boa seletividade a CO2 em condições experimentais moderadas (Temperatura 298K e pressão atmosférica). Os sólidos foram caracterizados por Difração de Raios-X (DRX), Fluorescência de Raios-X (FRX), Redução á Temperatura Programada de Hidrogênio (TPR-H2) e microscopia electrônica de barrido (SEM) evidenciando uma modificação estrutural exitosa em todos os materiais. Com o uso de ultrassom, conseguiu-se a modificação dos sólidos num tempo consideravelmente menor (20 min.) ao processo tradicional (24 horas) conservando as propriedades físico-químicas e catalíticas dos materiais. Igualmente, foi evidenciado um efeito da natureza da argila de partida sobre as propriedades químicas e catalíticas do material, assim como uma melhoria ao remover os óxidos de ferro do material natural, conseguindo-se assim sólidos com melhor atividade catalítica.

EXTRUIDOS DE AlFe-PILC EN LA OXIDACIÓN CATALÍTICA DE FENOL / AlFe-PILC EXTRUDED IN THE CATALYTIC OXIDATION OF PHENOL EXTRUDADOS / AlFe-PILC NA OXIDAÇÃO CATALITICA DO FENOL

Extruidos de AlFe-PILC con forma de cilindro compacto se emplearon como catalizadores en la reacción de oxidación de fenol en medio acuoso. Debido a que el proceso de elaboración de los extruidos con fase activa AlFe-PILC afecta la actividad intrínseca del catalizador, en este trabajo se determinaron la resistencia mecánica y la estabilidad química del catalizador conformado, así como las limitaciones difusionales por efecto de la aglomeración. Los extruidos se elaboraron con la proporción másica 42/28/30 de arcilla intercalada con AlFe, aglomerante (mezcla 50/50 de bentonita sódica y cálcica) y agua, exhibiendo elevada resistencia mecánica y estabilidad química a la inmersión en agua. Los extruidos de AlFe-PILC presentaron un factor de efectividad menor a 1; por tanto, la reacción se encuentra limitada por la difusión intrapartícula.

AlFe-PILC catalyst shaped as extruded compact cylinders was used in the oxidation of phenol in an aqueous medium. As the process of manufacturing AlFe-PILC extruded, affects the intrinsic activity of the catalyst, in this work the mechanical resistance, the chemical stability and the diffusional limitations of the catalyst conformed were determined. were manufactured with mass ratio 42/28/30 of intercalated clay with AlFe, binder (50/50 mixture of sodium and calcium bentonite) and water, exhibiting high mechanical resistance and chemical stability to immersion in water. The extruded AlFe-PILC showed an effectiveness factor less than 1, therefore, the reaction is limited by intraparticle diffusion.

Catalisador AlFe-PILC extrudado em forma de cilindro compacto foi utilizada na reação de oxidação do fenol em meio aquoso. Dado que o processo de desenvolvimento da fase ativa extrudados com AlFe-PILC afeta a atividade intrínseca do catalisador, neste trabalho determinar a resistência mecânica e estabilidade química do catalisador formando, e as limitações difusionais. Os extrudados foram produzidos com a relação massa 42/28/30 de argila intercaladas com AlFe, aglutinante (50/50mistura de bentonita de sódio e cálcio) e água, exibem alta resistência mecânica e estabilidade química de imersão em água. Os extrudados AlFe-PILC mostrou um factor de eficácia menor a 1, portanto, a reação é limitada pela difusão intrapartícula.

CARACTERIZACIÓN TÉRMICA Y ESPECTROSCÓPICA DE ARCILLAS PILARIZADAS CON SOLUCIONES POLIHIDROXOCATIÓNICAS DE Al, Ce, Fe / THERMAL AND SPECTROSCOPIC CHARACTERIZATION OF CLAYS PILLARED WITH Al, Ce, Fe POLYHYDROXOCATIONIC SOLUTIONS / CARACTERIZAÇÃO TÉRMICA E ESPECTROSCÓPICA DE ARGILAS PILARIZADAS COM SOLUÇÕES POLIHIDROXOCATIÔNICAS DE Al, Ce, Fe

Este trabajo presenta la caracterización por espectroscopía infrarroja (IR), análisis termogravimétrico (TGA), análisis térmico diferencial (DTA) y espectroscopía de resonancia magnética nuclear (RMN de 29Si y RMN de 27Al) de un conjunto de arcillas pilarizadas con soluciones polihidroxocatiónicas de Al, Al-Fe, Al-Ce o Al-Ce-Fe. Los análisis de TGADTA indican un efecto térmico favorable (mayor estabilidad térmica) con la adición de Ce, Fe o Ce-Fe. Los resultados de IR y deRMNde 29Si revelan una probable formación de enlace entre el pilar de alúmina y la capa tetraédrica de SiO4 de la arcilla, mientras que la RMN de 27Al no muestra evidencias de reemplazo isomórfico de Fe o Ce en los pilares de alúmina incorporados. Igualmente y por IR, no se observan diferencias estructurales entre los sólidos pilarizados con Al y los pilarizados con Al-Ce, lo cual indica que el cerio posiblemente se incorpora de manera independiente al pilar de alúmina.

This work shows the characterization by IR spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and nuclear magnetic resonance spectroscopy (29SiNMRand 27Al NMR) of a set of pillared clays synthesized with Al, Al-Fe, Al-Ce or Al-Ce-Fe polyhydroxocationic solutions. TGADTA analyses indicate a favorable thermal effect (higher thermal stability) when Ce, Fe or Ce-Fe are added. IR and 29Si NMR results reveal a probable formation of a bond between the alumina pillar and the clay (SiO4)-tetrahedral sheet, whereas the 27Al NMR does not evidence any isomorphous substitution of iron or cerium in the alumina pillars. Moreover, by IR spectroscopy was not observed any structural difference between solids pillared with Al and those pillared with Al-Ce, showing that cerium is possibly incorporated in an independent way to the alumina pillar.

Esse trabalho apresenta a caracterização mediante espectroscopia de absorção na região de infravermelho (IV), análise térmica (TGA/DTA) e espectrometria de ressonância magnética nuclear (RMN de 29Si yRMNde 27Al) de um conjunto de argilas pilarizadas com soluções polihidroxocatiônicas de Al, Al-Fe, Al-Ce o Al-Ce-Fe. As análises de TGA-DTA indicam um efeito térmico favorável (maior estabilidade térmica) com adição de Ce, Fe o Ce-Fe. Os resultados de IV e de RMN de 29Si revelam uma provável formação de ligação entre o pilar de alumina e a camada tetraédrica de SiO4 da argila, entretanto que RMN de 27Al não apresenta evidencias de substituição isomórfica de Fe ou Ce nos pilares de alumina incorporados. Além de mais, mediante IV não se observam diferencias estruturais entre os sólidos pilarizados com Al e os pilarizados com Al-Ce, indicando que o cério possivelmente incorpora-se de maneira diferente ao pilar de alumina.

Acidez e hidroioomerización de heptano en una vermiculita Colombiana modificada con aluminio / Aciity and hidrooisomerization of heptane over a Colombian vermiculite modified with aluminum

Una vermiculita colombiana ha sido modificada mediante un proceso de pilarización. En un primer paso, con el objetivo de disminuir la carga interlaminar, se realizó un tratamiento ácido seguido de calcinación. Las especies extra-red fueron removidas por un ácido complejante y luego llevadas a la forma homoionica. Finalmente se realizó una pilarización con aluminio. En el sólido modificado se verificó una reducción en la capacidad de intercambio catiónico (CIC) y un incremento en la acidez, evaluada por desorción de amoniaco y espectroscopia DRIFT. Los cambios estructurales y texturales se confirmaron por difracción de rayos-X (DRX) y sortometría. El comportamiento catalítico, evaluado por medio de la hidroisomerización de heptano, reveló un perfil superior en la arcilla modificada respecto al material de partida, conservando, además, sus propiedades a elevadas temperaturas.

A Colombian vermiculite has been modified by means of a pillaring process. In a first step, seeking to get a reduction of the interlayer charge, an acid treatment followed by calcinations was performed. The extra-framework species were removed using a complexing acid, and later taken it to the homoionic form. Finally a pillaring with aluminum was made. A reduction in the cation exchange capacity (CEC) and an increment in the evaluated acidity were found using ammonium desorption and DRIFT spectroscopy. The structural and textural changes were confirmed by X-ray diffraction (XRD) and nitrogen sorption measurements. The catalytic performance evaluated by means of the hidroisomerization of heptane, revealed a superior profile in the modified clay respect to the natural mineral, also preserving its properties at high temperatures.