J. Gottifredi - Academia.edu (original) (raw)
Papers by J. Gottifredi
Studies in Surface Science and Catalysis, 1998
Vanadium silicate gels (V2O5-SiO2) were prepared by the sol-gel method by hydrolysis of vanadium ... more Vanadium silicate gels (V2O5-SiO2) were prepared by the sol-gel method by hydrolysis of vanadium acetilacetonate and silicon alkoxide. The changes in the vanadium species and its interaction with SiO2 network upon heat treatment at various temperatures was studied by means of XRD, XPS and IR. The catalytic behavior for the oxidative dehydrogenation of n-butane was studied. It was found that
International Journal of Heat and Mass Transfer, 1979
ABSTRACT
International Journal of Heat and Mass Transfer, 1978
The paper shows that methods developed by Watkins (1975), Sparrow and Gregg (1958), Cess and Spar... more The paper shows that methods developed by Watkins (1975), Sparrow and Gregg (1958), Cess and Sparrow (1962), and Cess (1961) can be used to analyze unsteady heat transfer in impulsive Falkner-Skan flows. The short-term convective effect is found to be small, since both momentum and thermal boundary layers develop simultaneously. Thus, a very simple solution, valid for small Pr, is
Applied Catalysis A: General, 2006
... diluted in quartz. The reaction temperature range varied between 400 and 600 °C to achieve di... more ... diluted in quartz. The reaction temperature range varied between 400 and 600 °C to achieve different conversion levels. Blank tests on the same reactor showed no activity in all range of temperatures studied. Reactants and ...
Journal of Catalysis, 1968
Latin American …, 2004
Structural properties of vanadium dispersed species on γ γ γ γ-A1 2 0 3 are investigated with the... more Structural properties of vanadium dispersed species on γ γ γ γ-A1 2 0 3 are investigated with the scope to detect changes related with V loading in the oxidative dehydrogenation (ODH) of propane and nbutane. XPS, FTIR, and FTIR of absorbed pyridine were used to study the nature of vanadium supported species. Tetrahedral V 5+ and probably V 4+ species were detected. For vanadium loadings higher than 4.3 % wt octahedral species were also observed. In the n-butane ODH reaction, the selectivity to ODH products decreases when vanadium content increases. However, for propane ODH, the selectivity seems to be independent of vanadium loadings. Low oxygen/alkane feeding ratios favor selectivity to olefins. It is also shown that low V loading catalysts reach selectivities as good as best reported V-Mg-O catalyst.
Archivos latinoamericanos de nutrición, 1999
A supplementary sportman food, based on corn:soy extruded blend, freeze-dried egg albumen and pro... more A supplementary sportman food, based on corn:soy extruded blend, freeze-dried egg albumen and protein soy isolate, was developed. The resulting powder was subject to physico-chemical, functional, nutritional and sensorial test and then compared with a commercial food that was used as reference. Chemical and biological analysis of both foods revealed lower protein content in the formulated food (65%) than the commercial product (90%) although NPR values are larger in product showed (4.86) that than the observed in the second (4.03). On the other hand RNPR values of teh developed product also presented higher values than the commercial (Prot 90) (83.76 and 69.48 respectively). Casein was used as standard. Digestibility results were similar (93.65 and 95.7 for formulated and commercial products respectively). The absence of ureasic, antitryptic or hemagglutinating activity of the formulated product are also reported. Physico-chemical analysis shown that available lysine values are larg...
Matéria (Rio de Janeiro), 2018
RESUMEN Se sintetizó sílice mesoporosa a través del proceso sol-gel usando tetraetoxisilano (TEOS... more RESUMEN Se sintetizó sílice mesoporosa a través del proceso sol-gel usando tetraetoxisilano (TEOS) como fuente de sílice y bromuro de n-hexadeciltrimetilamonio (CTAB) como agente director de la estructura. La eliminación del surfactante post-síntesis, se realizó mediante dos técnicas: calcinación con incrementos programados de temperatura hasta alcanzar los 550°C y extracción con solventes usando HCl/EtOH como solución extractora y modificando algunas variables experimentales, tales como la concentración del ácido, el volumen de solución extractora, la duración del tratamiento y el solvente empleado para realizar el lavado. Las muestras fueron caracterizadas por adsorción de nitrógeno, espectroscopia de IR y SEM. Tanto la técnica de síntesis empleada como los procedimientos para eliminar el surfactante conducen a un material del tipo MCM-41. Mediante calcinación se obtienen materiales con un área superficial de 1100 m2/g mientras que la extracción con HCl/EtOH conduce a disminucione...
Latin American Applied Research - An international journal, 2020
Three-aminopropyltriethoxysilane modified MCM-41 mesoporous silicas were synthesized by grafting ... more Three-aminopropyltriethoxysilane modified MCM-41 mesoporous silicas were synthesized by grafting the organic groups on the support surface, using different molar ratios of SiO2:Aminosilane. The synthesized solids were characterized by N2 adsorption, XRD, FTIR and TG-DTA. MCM-41 has a specific surface area of about 1500 m2/g, while that of the functionalized materials falls around 600 m2/g, showing a tendency to decrease as the content of the functionalizing agent grows. The N2 adsorption isotherms of pure and functionalized materials are characteristic of mesoporous type IV materials. The structural properties were studied by FTIR and XRD. TG-DTA studies allow analyzing the thermal stability of the materials and determining the deposited amine content. The aminosilane modified mesoporous silica materials increase the CO2 adsorption capacity compared to that of the pure MCM-41. The results obtained are well interpreted by Freundlich physicochemical model and the model parameters show...
Modern Research in Catalysis, 2016
Nickel borides doped with transition metal (Cr, Mn, Fe, Co, Cu, and Zn) MNiB, 4% w/w respect to N... more Nickel borides doped with transition metal (Cr, Mn, Fe, Co, Cu, and Zn) MNiB, 4% w/w respect to Ni were prepared by chemical reduction of nickel and metallic salts in methanol solution with borane-tetrahydrofurane (BH 3-THF) complex obtained in aprotic solvent (THF anhydrous). Different techniques were used to characterize these materials. The MNiB amorphous structure was verified by XRD. Thermal treatment in N 2 shows Ni˚, Ni 2 Band NiO phases. Spongy-morphology was evident by SEM studies in all cases. XPS and TEM show that doped and non-doped nickel boride was present as Ni˚ in metallic state as principal phase and nickel alloying with boron was observed in minor quantities. The oxidation stability, magnetic susceptibility and catalytic effect are correlated with parameters of each dopant metal.
Catalysis Today, 2016
Immobilization and stabilization of an endoxylanase from Bacillus subtillis (XynA) for xylooligos... more Immobilization and stabilization of an endoxylanase from Bacillus subtillis (XynA) for xylooligosaccharides (XOs) production", Thais S.
The hydrogenation of cyclohexene was studied in both gas and liquid phases on six different palla... more The hydrogenation of cyclohexene was studied in both gas and liquid phases on six different palladium catalysts supported on silica gel and alumina between 264 and 308 K at hydrogen pressures from 4 to 89 kPa, cyclohexene partial pressures from 0.46 to 1.5 kPa, and cyclohexene concentrations from 0.15 to 3.0 M. Under these conditions the turnover frequency is independent of particle size (1.5 to 10 nm) in both liquid and gas phases, of the nature of the support, and of the nature of nonaromatic solvents (methanol, n-heptane, ethyl acetate, and cyclohexene). The order of reaction was one-half with respect to hydrogen for the reaction in both liquid and gas phases and zero with respect to cyclohexene partial pressure (gas phase) or with respect to cyclohexene molar concent’ration (liquid phase). At the same temperature and hydrogen pressure, the turnover frequency was about twice as high in the gas phase as in the liquid phase.
Chemical Engineering Communications, 1994
The estimation of effectiveness factor for the case of wave shell catalyst is attempted through a... more The estimation of effectiveness factor for the case of wave shell catalyst is attempted through an approximated procedure developed by the authors for other kind of catalytic pellets. It is shown that the approximate scheme can be used even with this kind of important catalysts and that the results so obtained are very accurate. The analysis is only restricted to
Procedia Materials Science, 2015
Due to environmental concerns, it is highly desirable to replace liquid HF or H 2 SO 4 by more be... more Due to environmental concerns, it is highly desirable to replace liquid HF or H 2 SO 4 by more benign solid acid such as sulfated zirconia (SZ). Sulfated zirconia materials have been demonstrated to be a good catalyst for the isomerization of lineal alkanes at relatively low temperatures. Our objective was: (1st) prepare nanostructured materials either by controlled hydrolysis of zirconium alkoxide or by impregnation of tetragonal zirconia with H 2 SO 4 1 M or ammonium sulfate, (2nd) carry out the characterization by conventional techniques (X ray diffraction, electron microscopy, N 2 adsorption, FT-IR/Raman spectroscopy, UV diffuse reflectance) and (3 rd) evaluate the acidity through the transesterification reaction of vinyl acetate with i-amyl alcohol to give i-amyl acetate and acetaldehyde and using toluene as solvent.
Catalysis Letters, 2018
Amorphous Cr-SiO 2 materials were synthesized by the sol-gel method and hydrothermally treated at... more Amorphous Cr-SiO 2 materials were synthesized by the sol-gel method and hydrothermally treated at temperatures between 150 and 220 °C. These materials were used as catalysts for cyclohexanol oxidation with H 2 O 2 as oxidant and CH 3 CN as a solvent. They were responsible for the decomposition of H 2 O 2 , which triggers, by a free radical mechanism in the homogeneous phase, the oxidation or degradation of the hydrocarbon chain. Metal leaching causes a drop in catalytic activity when the material is recycled. Studies on the hydrothermal treatment effect on the leaching process have demonstrated that the higher the hydrothermal treatment temperature, the higher the metal/support interaction, leading to a diminution of the leaching process. Under mild reaction conditions, and using TBHP as oxidant, leaching was reduced, and improvements were obtained on the selectivity towards the formation of cyclohexanone. The use of these catalysts in the oxidation of verbenol, an allylic alcohol, showed a significant increase in the substrate conversion and in the selectivity to carbonyl derivative formation.
Revista Latinoamericana De Transferencia De Calor Y Materia, 1982
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
In this contribution, effectiveness factor () calculations are performed by a perturbation and ma... more In this contribution, effectiveness factor () calculations are performed by a perturbation and matching technique developed by the authors which takes into account both the intrinsic kinetic expression and external heat and mass transfer resistances. The simplified method of Papadias et al. (2000) was used to consider the non-uniform washcoat thickness usually present in monolith channels. As a result a global effectiveness factor (o) is calculated at each point on the grid to simulate monolith reactor performance. The procedure was tested to predict experimental findings taking into account the actual kinetic expression to describe CO oxidation on Pt catalyst. Agreement among theoretical predictions and Ullah et al. (1992) and Holmgren and Andersson (1998) experimental results are fairly good.
The Chemical Engineering Journal, 1978
ABSTRACT
Reaction Kinetics and Catalysis Letters, 1989
Catalytic activity of ferric oxide was evaluated in the oxidative dehydrogenation of n-butane. Th... more Catalytic activity of ferric oxide was evaluated in the oxidative dehydrogenation of n-butane. The apparent activation energy determined in the kinetic region was 37.7 kcal/mol. The activity of this oxide was undetectable up to 430°C. Reaction product distributions are shown as functions of temperature in the range of 430–650°C.
Studies in Surface Science and Catalysis, 1998
Vanadium silicate gels (V2O5-SiO2) were prepared by the sol-gel method by hydrolysis of vanadium ... more Vanadium silicate gels (V2O5-SiO2) were prepared by the sol-gel method by hydrolysis of vanadium acetilacetonate and silicon alkoxide. The changes in the vanadium species and its interaction with SiO2 network upon heat treatment at various temperatures was studied by means of XRD, XPS and IR. The catalytic behavior for the oxidative dehydrogenation of n-butane was studied. It was found that
International Journal of Heat and Mass Transfer, 1979
ABSTRACT
International Journal of Heat and Mass Transfer, 1978
The paper shows that methods developed by Watkins (1975), Sparrow and Gregg (1958), Cess and Spar... more The paper shows that methods developed by Watkins (1975), Sparrow and Gregg (1958), Cess and Sparrow (1962), and Cess (1961) can be used to analyze unsteady heat transfer in impulsive Falkner-Skan flows. The short-term convective effect is found to be small, since both momentum and thermal boundary layers develop simultaneously. Thus, a very simple solution, valid for small Pr, is
Applied Catalysis A: General, 2006
... diluted in quartz. The reaction temperature range varied between 400 and 600 °C to achieve di... more ... diluted in quartz. The reaction temperature range varied between 400 and 600 °C to achieve different conversion levels. Blank tests on the same reactor showed no activity in all range of temperatures studied. Reactants and ...
Journal of Catalysis, 1968
Latin American …, 2004
Structural properties of vanadium dispersed species on γ γ γ γ-A1 2 0 3 are investigated with the... more Structural properties of vanadium dispersed species on γ γ γ γ-A1 2 0 3 are investigated with the scope to detect changes related with V loading in the oxidative dehydrogenation (ODH) of propane and nbutane. XPS, FTIR, and FTIR of absorbed pyridine were used to study the nature of vanadium supported species. Tetrahedral V 5+ and probably V 4+ species were detected. For vanadium loadings higher than 4.3 % wt octahedral species were also observed. In the n-butane ODH reaction, the selectivity to ODH products decreases when vanadium content increases. However, for propane ODH, the selectivity seems to be independent of vanadium loadings. Low oxygen/alkane feeding ratios favor selectivity to olefins. It is also shown that low V loading catalysts reach selectivities as good as best reported V-Mg-O catalyst.
Archivos latinoamericanos de nutrición, 1999
A supplementary sportman food, based on corn:soy extruded blend, freeze-dried egg albumen and pro... more A supplementary sportman food, based on corn:soy extruded blend, freeze-dried egg albumen and protein soy isolate, was developed. The resulting powder was subject to physico-chemical, functional, nutritional and sensorial test and then compared with a commercial food that was used as reference. Chemical and biological analysis of both foods revealed lower protein content in the formulated food (65%) than the commercial product (90%) although NPR values are larger in product showed (4.86) that than the observed in the second (4.03). On the other hand RNPR values of teh developed product also presented higher values than the commercial (Prot 90) (83.76 and 69.48 respectively). Casein was used as standard. Digestibility results were similar (93.65 and 95.7 for formulated and commercial products respectively). The absence of ureasic, antitryptic or hemagglutinating activity of the formulated product are also reported. Physico-chemical analysis shown that available lysine values are larg...
Matéria (Rio de Janeiro), 2018
RESUMEN Se sintetizó sílice mesoporosa a través del proceso sol-gel usando tetraetoxisilano (TEOS... more RESUMEN Se sintetizó sílice mesoporosa a través del proceso sol-gel usando tetraetoxisilano (TEOS) como fuente de sílice y bromuro de n-hexadeciltrimetilamonio (CTAB) como agente director de la estructura. La eliminación del surfactante post-síntesis, se realizó mediante dos técnicas: calcinación con incrementos programados de temperatura hasta alcanzar los 550°C y extracción con solventes usando HCl/EtOH como solución extractora y modificando algunas variables experimentales, tales como la concentración del ácido, el volumen de solución extractora, la duración del tratamiento y el solvente empleado para realizar el lavado. Las muestras fueron caracterizadas por adsorción de nitrógeno, espectroscopia de IR y SEM. Tanto la técnica de síntesis empleada como los procedimientos para eliminar el surfactante conducen a un material del tipo MCM-41. Mediante calcinación se obtienen materiales con un área superficial de 1100 m2/g mientras que la extracción con HCl/EtOH conduce a disminucione...
Latin American Applied Research - An international journal, 2020
Three-aminopropyltriethoxysilane modified MCM-41 mesoporous silicas were synthesized by grafting ... more Three-aminopropyltriethoxysilane modified MCM-41 mesoporous silicas were synthesized by grafting the organic groups on the support surface, using different molar ratios of SiO2:Aminosilane. The synthesized solids were characterized by N2 adsorption, XRD, FTIR and TG-DTA. MCM-41 has a specific surface area of about 1500 m2/g, while that of the functionalized materials falls around 600 m2/g, showing a tendency to decrease as the content of the functionalizing agent grows. The N2 adsorption isotherms of pure and functionalized materials are characteristic of mesoporous type IV materials. The structural properties were studied by FTIR and XRD. TG-DTA studies allow analyzing the thermal stability of the materials and determining the deposited amine content. The aminosilane modified mesoporous silica materials increase the CO2 adsorption capacity compared to that of the pure MCM-41. The results obtained are well interpreted by Freundlich physicochemical model and the model parameters show...
Modern Research in Catalysis, 2016
Nickel borides doped with transition metal (Cr, Mn, Fe, Co, Cu, and Zn) MNiB, 4% w/w respect to N... more Nickel borides doped with transition metal (Cr, Mn, Fe, Co, Cu, and Zn) MNiB, 4% w/w respect to Ni were prepared by chemical reduction of nickel and metallic salts in methanol solution with borane-tetrahydrofurane (BH 3-THF) complex obtained in aprotic solvent (THF anhydrous). Different techniques were used to characterize these materials. The MNiB amorphous structure was verified by XRD. Thermal treatment in N 2 shows Ni˚, Ni 2 Band NiO phases. Spongy-morphology was evident by SEM studies in all cases. XPS and TEM show that doped and non-doped nickel boride was present as Ni˚ in metallic state as principal phase and nickel alloying with boron was observed in minor quantities. The oxidation stability, magnetic susceptibility and catalytic effect are correlated with parameters of each dopant metal.
Catalysis Today, 2016
Immobilization and stabilization of an endoxylanase from Bacillus subtillis (XynA) for xylooligos... more Immobilization and stabilization of an endoxylanase from Bacillus subtillis (XynA) for xylooligosaccharides (XOs) production", Thais S.
The hydrogenation of cyclohexene was studied in both gas and liquid phases on six different palla... more The hydrogenation of cyclohexene was studied in both gas and liquid phases on six different palladium catalysts supported on silica gel and alumina between 264 and 308 K at hydrogen pressures from 4 to 89 kPa, cyclohexene partial pressures from 0.46 to 1.5 kPa, and cyclohexene concentrations from 0.15 to 3.0 M. Under these conditions the turnover frequency is independent of particle size (1.5 to 10 nm) in both liquid and gas phases, of the nature of the support, and of the nature of nonaromatic solvents (methanol, n-heptane, ethyl acetate, and cyclohexene). The order of reaction was one-half with respect to hydrogen for the reaction in both liquid and gas phases and zero with respect to cyclohexene partial pressure (gas phase) or with respect to cyclohexene molar concent’ration (liquid phase). At the same temperature and hydrogen pressure, the turnover frequency was about twice as high in the gas phase as in the liquid phase.
Chemical Engineering Communications, 1994
The estimation of effectiveness factor for the case of wave shell catalyst is attempted through a... more The estimation of effectiveness factor for the case of wave shell catalyst is attempted through an approximated procedure developed by the authors for other kind of catalytic pellets. It is shown that the approximate scheme can be used even with this kind of important catalysts and that the results so obtained are very accurate. The analysis is only restricted to
Procedia Materials Science, 2015
Due to environmental concerns, it is highly desirable to replace liquid HF or H 2 SO 4 by more be... more Due to environmental concerns, it is highly desirable to replace liquid HF or H 2 SO 4 by more benign solid acid such as sulfated zirconia (SZ). Sulfated zirconia materials have been demonstrated to be a good catalyst for the isomerization of lineal alkanes at relatively low temperatures. Our objective was: (1st) prepare nanostructured materials either by controlled hydrolysis of zirconium alkoxide or by impregnation of tetragonal zirconia with H 2 SO 4 1 M or ammonium sulfate, (2nd) carry out the characterization by conventional techniques (X ray diffraction, electron microscopy, N 2 adsorption, FT-IR/Raman spectroscopy, UV diffuse reflectance) and (3 rd) evaluate the acidity through the transesterification reaction of vinyl acetate with i-amyl alcohol to give i-amyl acetate and acetaldehyde and using toluene as solvent.
Catalysis Letters, 2018
Amorphous Cr-SiO 2 materials were synthesized by the sol-gel method and hydrothermally treated at... more Amorphous Cr-SiO 2 materials were synthesized by the sol-gel method and hydrothermally treated at temperatures between 150 and 220 °C. These materials were used as catalysts for cyclohexanol oxidation with H 2 O 2 as oxidant and CH 3 CN as a solvent. They were responsible for the decomposition of H 2 O 2 , which triggers, by a free radical mechanism in the homogeneous phase, the oxidation or degradation of the hydrocarbon chain. Metal leaching causes a drop in catalytic activity when the material is recycled. Studies on the hydrothermal treatment effect on the leaching process have demonstrated that the higher the hydrothermal treatment temperature, the higher the metal/support interaction, leading to a diminution of the leaching process. Under mild reaction conditions, and using TBHP as oxidant, leaching was reduced, and improvements were obtained on the selectivity towards the formation of cyclohexanone. The use of these catalysts in the oxidation of verbenol, an allylic alcohol, showed a significant increase in the substrate conversion and in the selectivity to carbonyl derivative formation.
Revista Latinoamericana De Transferencia De Calor Y Materia, 1982
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
In this contribution, effectiveness factor () calculations are performed by a perturbation and ma... more In this contribution, effectiveness factor () calculations are performed by a perturbation and matching technique developed by the authors which takes into account both the intrinsic kinetic expression and external heat and mass transfer resistances. The simplified method of Papadias et al. (2000) was used to consider the non-uniform washcoat thickness usually present in monolith channels. As a result a global effectiveness factor (o) is calculated at each point on the grid to simulate monolith reactor performance. The procedure was tested to predict experimental findings taking into account the actual kinetic expression to describe CO oxidation on Pt catalyst. Agreement among theoretical predictions and Ullah et al. (1992) and Holmgren and Andersson (1998) experimental results are fairly good.
The Chemical Engineering Journal, 1978
ABSTRACT
Reaction Kinetics and Catalysis Letters, 1989
Catalytic activity of ferric oxide was evaluated in the oxidative dehydrogenation of n-butane. Th... more Catalytic activity of ferric oxide was evaluated in the oxidative dehydrogenation of n-butane. The apparent activation energy determined in the kinetic region was 37.7 kcal/mol. The activity of this oxide was undetectable up to 430°C. Reaction product distributions are shown as functions of temperature in the range of 430–650°C.