The microporosity of aluminium pillared montmorillonite has been investigated by nitrogen adsorpt... more The microporosity of aluminium pillared montmorillonite has been investigated by nitrogen adsorption, X-ray diffraction and electron microscopy. Control of the preparation conditions allowed the synthesis of solids with two types of micropores. Comparison of XRD measurements and Horvath-Kawazoe analysis of very low,pressure nitrogen adsorption have shown a new promising way to increase the micropore characterization. Disagreement between data from different techniques could be related to the different experimental conditions during measurements and to uncertain values of the interaction parameter in the Horvath-Kawazoe analysis.
... Abstract. In this work aluminium foams were studied as structured supports for the eliminatio... more ... Abstract. In this work aluminium foams were studied as structured supports for the elimination of volatile organic compounds (VOCs, toluene). ... Graphical abstract. Aluminium foams were studied as structured supports for the elimination of volatile organic compounds (toluene). ...
As an approach to deposition of zeolites on microreactors, MFI type zeolite was deposited over Fe... more As an approach to deposition of zeolites on microreactors, MFI type zeolite was deposited over Fecralloy monoliths containing micron size channels by two different methods: washcoating from a stabilized slurry and in situ growing of the zeolite on the metallic surface introduced in the synthesis medium. Repeated washcoating or synthesis over the same support has been proved as a good and efficient method to cover the entire surface of the support with a zeolite layer. The support surface was totally covered with a very adherent layer in both cases but the final textural properties were different. Due to the presence of different additives in the formulation of the slurry, the washcoating method produced a coating with additional mesoporosity to the microporosity of the starting zeolite powder. Deposition by in situ synthesis produced pure microporous zeolite coating on the support surface but required longer times than washcoating method. Washcoating produced a layer with zeolite crystals randomly oriented while deposition by synthesis directed the crystal growing to a preferential orientation.
Industrial Engineering Chemistry Research, Feb 17, 2010
The influence of the alumina layer nature which acts as the support on the preparation of structu... more The influence of the alumina layer nature which acts as the support on the preparation of structured catalysts and on the catalytic performance in VOC combustion was studied. Anodized aluminum and a ferritic alloy covered with colloidal alumina (Nyacol) and θ-δ-Al 2 O 3 were the materials used to prepare the monolith catalysts. The impregnation was performed in one and two stages using two different concentrations of manganese acetate solutions. The catalytic properties of these catalysts were evaluated in ethanol, ethyl acetate, and toluene combustion. The most active catalysts in the combustion of the three molecules were those prepared using a θ-δ-Al 2 O 3 as a support. The low activity of aluminum monoliths anodized with H 2 SO 4 is due to the presence of SO 4 2ions which act as catalyst poison. The anodization with H 2 C 2 O 4 is a preferable method to prepare MnOx monolithic catalysts.
ABSTRACT The influence of the method of preparation and type of support on the activity and selec... more ABSTRACT The influence of the method of preparation and type of support on the activity and selectivity of supported nickel catalysts was investigated. Silica and silica alumina were used as supports. Catalysts were prepared over these supports by incipient wetness impregnation and by precipitation-deposition. In each instance two different temperatures of reduction (300 and 500°C) were used. Physico-chemical characterization included total nickel content, total surface area, metallic surface area, degree of reduction, mean particle size and temperature-programmed reduction. The reactions of n-pentane in the presence of hydrogen and the hydrogenation of benzene were studied. The former was found to be structure sensitive with a well defined maximum of activity as the particle size increased. On the other hand, owing to the scatter of the data, the results obtained for the hydrogenation of benzene are open to discussion. The selectivity of the reaction of n-pentane in the presence of hydrogen was not affected by the type of support but it was significantly influenced by the method of preparation.
ABSTRACT Preparation of monolithic catalysts for VOCs abatement based on Al2O3/Al supports has be... more ABSTRACT Preparation of monolithic catalysts for VOCs abatement based on Al2O3/Al supports has been studied. The influence of electrochemical anodization variables of an aluminium foil (current density, electrolyte concentration and time) on the properties of the A(2)O(3) layer formed has been studied. Surface areas of up to 1600 m(2) of Al2O3 per square meter of aluminium foil having narrow pore size distribution of around 20 nm, can be produced under easily controlled experimental conditions. Monoliths made of this cermet material impregnated with platinum show higher activity for the complete oxidation of toluene than conventional Pt/Al2O3 powders. The presence of sulphate anions arising from the anodization step is proposed to explain the activity difference.
The purpose of this study was to evaluate the effect of the precursors on the synthesis of MnOx-S... more The purpose of this study was to evaluate the effect of the precursors on the synthesis of MnOx-SBA15 catalysts. The influence of the manganese phase on the activity of catalysts in the complete oxidation of ethyl acetate was also tested. SBA15 was synthesized according to a standard method reported in the literature and manganese was introduced onto the support following
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
Two MnO x catalyst as powder, prepared by decomposition of two different MnCO 3 , have been depos... more Two MnO x catalyst as powder, prepared by decomposition of two different MnCO 3 , have been deposited on a FeCrAlloy® metallic monolith by means of washcoating using slurry concentration of 25 and 40 wt(%) (PM25, PM40 and AM25). When increase slurry concentration increase the amount of deposited material, but lower adhesion of solid retained is observed. The obtained monoliths showed excellent catalytic activity in the combustion of ethyl acetate and toluene, being the monoliths activity order: PM40 > AM25 > PM25. Nevertheless, the conversion g -1 and conversion m -2 show that PM25 is the more active monolith.
The preparation and characterization of silica-alumina pillared clays have been studied. The form... more The preparation and characterization of silica-alumina pillared clays have been studied. The formation and aging of hydroxy -alumina oligocations followed by reaction with Si(OEt)4 have been studied in order to obtain hydroxy-SiAl oligocations. Two solutions of A113 (Keggin cation) containing an OWAI mole ratio equal to 2 have been used in the preparation of the hydroxy-silica-alumina solutions: solution A aged at room temperature for 48 h, and solution B aged at 393 K for 4 h. Different SUA1 ratios (0, 0.5, 1, and 2) and
Manganese oxide systems were prepared in the form of laminar octahedral compounds (birnessites) o... more Manganese oxide systems were prepared in the form of laminar octahedral compounds (birnessites) or octahedral molecular sieves (cryptomelanes) in order to test their efficiency as catalysts for the abatement of volatile organic compounds. Gelation routes and redox-reflux methods with different precursors were chosen such as KMnO 4 /glucose, KMnO 4 /polyvinyl alcohol for birnessites and KMnO 4 /Mn-oxalate, KMnO 4 /Mn-sulphate and KMnO 4 /Mn-acetate for cryptomelanes. Birnessite, prepared using glucose as the reducing agent, showed a high activity in the total oxidation of acetone in spite of the moderate surface area. Cryptomelanes, prepared from Manganese carboxylates, present the classical fibrous morphology with a high surface area and were extremely active for acetone total oxidation.
Structured catalysts for Fischer-Tropsch synthesis (FTS) have been obtained by deposition of thin... more Structured catalysts for Fischer-Tropsch synthesis (FTS) have been obtained by deposition of thin 20 wt. % Co/ -Al 2 O 3 catalyst layers washcoats onto the metallic surface of monolithic supports applying a preparation procedure involving: (a) preparation of metallic monoliths, (b) preparation of stable slurry of catalyst, (c) dip-coating of monolithic supports. The quality of catalyst coatings was evaluated in terms of loading, homogeneity and adhesion force. Through this procedure, Fecralloy® monoliths pretreated by thermal oxidation have been loaded with a 450 mg welladhered catalyst coating layer and tested in FTS at 250 ºC, 10 bar, under synthesis gas composition H 2 /CO = 2. Both the coated monoliths and catalyst powder tested in FTS under similar operating conditions revealed rather comparable results in terms of activity and selectivity as a consequence of using thin layers and small particle size of powder (below 250 m). Diffusion distances obtained for the catalytic materials resulted to be appropriate for minimizing the mass transfer effects or diffusion limitations.
The most important parameters controlling the washcoating of metallic structures from catalytic s... more The most important parameters controlling the washcoating of metallic structures from catalytic slurries are reviewed. The slurry must be stable with adequate rheological properties controlled by the solid content, particle size and additives. The metallic substrate must be pre-treated to obtain an adherent surface scale compatible with the coating and presenting appropriate surface roughness. The quality of the produced coating (homogeneity, specific load and adherence) depends essentially on slurry properties (viscosity and solid content) and on the technique used to remove slurry excess.
Zinc-aluminum hydrotalcite-like thin films were prepared by direct precipitation on the surface o... more Zinc-aluminum hydrotalcite-like thin films were prepared by direct precipitation on the surface of Al 2 O 3 /Al monoliths. The mesopores of anodic alumina provided channels and nano-sized wall-edges for supplying Al 3+ and highly active reaction sites. In this work, the influence of temperature, time and Zn:NH 3 molar ratio in the obtention of highly homogeneous and adherent hydrotalcite films is studied. We show that the amount loaded, integrity and textural properties of the Zn-Al hydrotalcite-like film are strongly influenced by the preparation conditions. The prepared monoliths were tested for VOC abatement (total oxidation of ethanol and ethyl acetate) showing good activity.
The microporosity of aluminium pillared montmorillonite has been investigated by nitrogen adsorpt... more The microporosity of aluminium pillared montmorillonite has been investigated by nitrogen adsorption, X-ray diffraction and electron microscopy. Control of the preparation conditions allowed the synthesis of solids with two types of micropores. Comparison of XRD measurements and Horvath-Kawazoe analysis of very low,pressure nitrogen adsorption have shown a new promising way to increase the micropore characterization. Disagreement between data from different techniques could be related to the different experimental conditions during measurements and to uncertain values of the interaction parameter in the Horvath-Kawazoe analysis.
... Abstract. In this work aluminium foams were studied as structured supports for the eliminatio... more ... Abstract. In this work aluminium foams were studied as structured supports for the elimination of volatile organic compounds (VOCs, toluene). ... Graphical abstract. Aluminium foams were studied as structured supports for the elimination of volatile organic compounds (toluene). ...
As an approach to deposition of zeolites on microreactors, MFI type zeolite was deposited over Fe... more As an approach to deposition of zeolites on microreactors, MFI type zeolite was deposited over Fecralloy monoliths containing micron size channels by two different methods: washcoating from a stabilized slurry and in situ growing of the zeolite on the metallic surface introduced in the synthesis medium. Repeated washcoating or synthesis over the same support has been proved as a good and efficient method to cover the entire surface of the support with a zeolite layer. The support surface was totally covered with a very adherent layer in both cases but the final textural properties were different. Due to the presence of different additives in the formulation of the slurry, the washcoating method produced a coating with additional mesoporosity to the microporosity of the starting zeolite powder. Deposition by in situ synthesis produced pure microporous zeolite coating on the support surface but required longer times than washcoating method. Washcoating produced a layer with zeolite crystals randomly oriented while deposition by synthesis directed the crystal growing to a preferential orientation.
Industrial Engineering Chemistry Research, Feb 17, 2010
The influence of the alumina layer nature which acts as the support on the preparation of structu... more The influence of the alumina layer nature which acts as the support on the preparation of structured catalysts and on the catalytic performance in VOC combustion was studied. Anodized aluminum and a ferritic alloy covered with colloidal alumina (Nyacol) and θ-δ-Al 2 O 3 were the materials used to prepare the monolith catalysts. The impregnation was performed in one and two stages using two different concentrations of manganese acetate solutions. The catalytic properties of these catalysts were evaluated in ethanol, ethyl acetate, and toluene combustion. The most active catalysts in the combustion of the three molecules were those prepared using a θ-δ-Al 2 O 3 as a support. The low activity of aluminum monoliths anodized with H 2 SO 4 is due to the presence of SO 4 2ions which act as catalyst poison. The anodization with H 2 C 2 O 4 is a preferable method to prepare MnOx monolithic catalysts.
ABSTRACT The influence of the method of preparation and type of support on the activity and selec... more ABSTRACT The influence of the method of preparation and type of support on the activity and selectivity of supported nickel catalysts was investigated. Silica and silica alumina were used as supports. Catalysts were prepared over these supports by incipient wetness impregnation and by precipitation-deposition. In each instance two different temperatures of reduction (300 and 500°C) were used. Physico-chemical characterization included total nickel content, total surface area, metallic surface area, degree of reduction, mean particle size and temperature-programmed reduction. The reactions of n-pentane in the presence of hydrogen and the hydrogenation of benzene were studied. The former was found to be structure sensitive with a well defined maximum of activity as the particle size increased. On the other hand, owing to the scatter of the data, the results obtained for the hydrogenation of benzene are open to discussion. The selectivity of the reaction of n-pentane in the presence of hydrogen was not affected by the type of support but it was significantly influenced by the method of preparation.
ABSTRACT Preparation of monolithic catalysts for VOCs abatement based on Al2O3/Al supports has be... more ABSTRACT Preparation of monolithic catalysts for VOCs abatement based on Al2O3/Al supports has been studied. The influence of electrochemical anodization variables of an aluminium foil (current density, electrolyte concentration and time) on the properties of the A(2)O(3) layer formed has been studied. Surface areas of up to 1600 m(2) of Al2O3 per square meter of aluminium foil having narrow pore size distribution of around 20 nm, can be produced under easily controlled experimental conditions. Monoliths made of this cermet material impregnated with platinum show higher activity for the complete oxidation of toluene than conventional Pt/Al2O3 powders. The presence of sulphate anions arising from the anodization step is proposed to explain the activity difference.
The purpose of this study was to evaluate the effect of the precursors on the synthesis of MnOx-S... more The purpose of this study was to evaluate the effect of the precursors on the synthesis of MnOx-SBA15 catalysts. The influence of the manganese phase on the activity of catalysts in the complete oxidation of ethyl acetate was also tested. SBA15 was synthesized according to a standard method reported in the literature and manganese was introduced onto the support following
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
Two MnO x catalyst as powder, prepared by decomposition of two different MnCO 3 , have been depos... more Two MnO x catalyst as powder, prepared by decomposition of two different MnCO 3 , have been deposited on a FeCrAlloy® metallic monolith by means of washcoating using slurry concentration of 25 and 40 wt(%) (PM25, PM40 and AM25). When increase slurry concentration increase the amount of deposited material, but lower adhesion of solid retained is observed. The obtained monoliths showed excellent catalytic activity in the combustion of ethyl acetate and toluene, being the monoliths activity order: PM40 > AM25 > PM25. Nevertheless, the conversion g -1 and conversion m -2 show that PM25 is the more active monolith.
The preparation and characterization of silica-alumina pillared clays have been studied. The form... more The preparation and characterization of silica-alumina pillared clays have been studied. The formation and aging of hydroxy -alumina oligocations followed by reaction with Si(OEt)4 have been studied in order to obtain hydroxy-SiAl oligocations. Two solutions of A113 (Keggin cation) containing an OWAI mole ratio equal to 2 have been used in the preparation of the hydroxy-silica-alumina solutions: solution A aged at room temperature for 48 h, and solution B aged at 393 K for 4 h. Different SUA1 ratios (0, 0.5, 1, and 2) and
Manganese oxide systems were prepared in the form of laminar octahedral compounds (birnessites) o... more Manganese oxide systems were prepared in the form of laminar octahedral compounds (birnessites) or octahedral molecular sieves (cryptomelanes) in order to test their efficiency as catalysts for the abatement of volatile organic compounds. Gelation routes and redox-reflux methods with different precursors were chosen such as KMnO 4 /glucose, KMnO 4 /polyvinyl alcohol for birnessites and KMnO 4 /Mn-oxalate, KMnO 4 /Mn-sulphate and KMnO 4 /Mn-acetate for cryptomelanes. Birnessite, prepared using glucose as the reducing agent, showed a high activity in the total oxidation of acetone in spite of the moderate surface area. Cryptomelanes, prepared from Manganese carboxylates, present the classical fibrous morphology with a high surface area and were extremely active for acetone total oxidation.
Structured catalysts for Fischer-Tropsch synthesis (FTS) have been obtained by deposition of thin... more Structured catalysts for Fischer-Tropsch synthesis (FTS) have been obtained by deposition of thin 20 wt. % Co/ -Al 2 O 3 catalyst layers washcoats onto the metallic surface of monolithic supports applying a preparation procedure involving: (a) preparation of metallic monoliths, (b) preparation of stable slurry of catalyst, (c) dip-coating of monolithic supports. The quality of catalyst coatings was evaluated in terms of loading, homogeneity and adhesion force. Through this procedure, Fecralloy® monoliths pretreated by thermal oxidation have been loaded with a 450 mg welladhered catalyst coating layer and tested in FTS at 250 ºC, 10 bar, under synthesis gas composition H 2 /CO = 2. Both the coated monoliths and catalyst powder tested in FTS under similar operating conditions revealed rather comparable results in terms of activity and selectivity as a consequence of using thin layers and small particle size of powder (below 250 m). Diffusion distances obtained for the catalytic materials resulted to be appropriate for minimizing the mass transfer effects or diffusion limitations.
The most important parameters controlling the washcoating of metallic structures from catalytic s... more The most important parameters controlling the washcoating of metallic structures from catalytic slurries are reviewed. The slurry must be stable with adequate rheological properties controlled by the solid content, particle size and additives. The metallic substrate must be pre-treated to obtain an adherent surface scale compatible with the coating and presenting appropriate surface roughness. The quality of the produced coating (homogeneity, specific load and adherence) depends essentially on slurry properties (viscosity and solid content) and on the technique used to remove slurry excess.
Zinc-aluminum hydrotalcite-like thin films were prepared by direct precipitation on the surface o... more Zinc-aluminum hydrotalcite-like thin films were prepared by direct precipitation on the surface of Al 2 O 3 /Al monoliths. The mesopores of anodic alumina provided channels and nano-sized wall-edges for supplying Al 3+ and highly active reaction sites. In this work, the influence of temperature, time and Zn:NH 3 molar ratio in the obtention of highly homogeneous and adherent hydrotalcite films is studied. We show that the amount loaded, integrity and textural properties of the Zn-Al hydrotalcite-like film are strongly influenced by the preparation conditions. The prepared monoliths were tested for VOC abatement (total oxidation of ethanol and ethyl acetate) showing good activity.
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