Tomas Viveros - Academia.edu (original) (raw)
Papers by Tomas Viveros
Avances En Ciencias E Ingenieria, 2012
Catalysis Today, Oct 30, 2009
El uso del método de micro-emulsión permitió obtener nano-catalizadores de Ni/SiO2 con la estruct... more El uso del método de micro-emulsión permitió obtener nano-catalizadores de Ni/SiO2 con la estructura requerida, debido a la interacción entre los componentes que forman la micro-emulsión (tensoactivo, fase acuosa y fase orgánica) y las sales precursoras disueltas en la fase acuosa, produce catalizadores que presentan propiedades texturales sobresalientes, basado en los resultados mostrados, por las diferentes técnicas usadas que indican que la descomposición térmica de los sólidos obtenidos, ocurre en diferentes etapas hasta obtener como producto final, óxidos de níquel (II) estables y dispersos en sílice, produciendo una opción atractiva para ser aplicadas en reacciones de hidrogenación.
Se observa una clara ventaja de actividad HDS de 4,6-DMDBT para los catalizadores NiMo soportados... more Se observa una clara ventaja de actividad HDS de 4,6-DMDBT para los catalizadores NiMo soportados en alúmina con un contenido de óxido de zirconio del 10 y 15% respectivamente.
Computer Aided Chemical Engineering, 2015
ABSTRACT An integrated reactive distillation process for the production of biodiesel is proposed.... more ABSTRACT An integrated reactive distillation process for the production of biodiesel is proposed. The reactive separation process consists of two coupled reactive distillation columns considering the kinetically controlled reactions of esterification of the fatty acids (FFAs) and the trans-esterification of the tri-di and mono glycerides with methanol, respectively. The conceptual design of each reactive distillation column was performed through the construction of reactive residue curve maps in terms of elements. The design of the esterification reactive distillation column consisted of one reactive zone loaded with a solid catalyst (titanium oxide supported on silica TiO 2 /SiO 2) and for the trans-esterification reactive column two reactive zones loaded with solid catalyst (hydrotalcites (CHT) and MgO). Intensive simulation of the integrated reactive process including the complex kinetic expressions for the different reactions and the Cubic-Plus Association (CPA) thermodynamic model was performed using the computational environment of ASPEN Plus. Results showed that the amount of fatty acids (FFAs) and water in the oil fed play a key role on the performance of the trans-esterification reactive distillation column while for the esterification column is not significant.
An approximate method to evaluate global effectiveness factor has been developed. It results from... more An approximate method to evaluate global effectiveness factor has been developed. It results from the inclusion of external mass transfer in an earlier method, which considered intraphase effectiveness factor estimations. The method, based on the approximation of the reaction rate above the surface concentrations, requires only the solution of an algebraic equation, instead of solving the differential one that defines
Studies in Surface Science and Catalysis, 1997
... 0.2 0.0 o. 1 0.2 oe 0.0 lectivity to the intermediate action product. re-Coke Content (rr~rng... more ... 0.2 0.0 o. 1 0.2 oe 0.0 lectivity to the intermediate action product. re-Coke Content (rr~rng cat.) Figure 5. Influence of the reduction temperature on ethylene selectivity. ... 13 JA Montoya, JC Rodriguez, I. Schifter, A. Monzon and T. Viveros, Stud. Surf. Sci. and Catal., 88 (1994) 531. ...
Studies in Surface Science and Catalysis, 1997
Studies in Surface Science and Catalysis, 2000
In order to assess the effect of various synthesis parameters and the presence of a second oxide ... more In order to assess the effect of various synthesis parameters and the presence of a second oxide (TiO2 or ZrO2) at different concentrations on the Al2O3 structure, the corresponding samples were prepared by low-temperature sol-gel method. The oxides were characterized by N2 physisorption, XRD and 27A1 MAS-NMR. In all samples calcined at Tc≤973 K four-, five- and six-coordinated aluminum were
Fuel, 2014
ABSTRACT Compensation effects were found in isopropanol dehydration over alumina (A), titania (T)... more ABSTRACT Compensation effects were found in isopropanol dehydration over alumina (A), titania (T) and corresponding mixed oxides (Al/Ti = 2 and 25 mol ratio, AT2 and AT25, respectively) synthesized by low-temperature sol-gel. Prepared materials (calcined in the 573-1173 K) range were characterized by several techniques (N2 physisorption, XRD, thermal analysis and SEM). In general, Al2O3 had the highest reaction rate (at 473 K) in propylene formation meanwhile both mixed oxides had much lower activity. TiO2 had minimal dehydrating activity that, nevertheless, was the highest intrinsic one (in areal basis). Constable plots were obtained for materials annealed at various temperatures, but for titania series. A clear isokinetic temperature (Tθ) was observed for alumina series whereas for AT25 materials, a Tθ pole was registered but for the sample calcined at the most severe condition. Meanwhile, two Tθ poles were identified for AT2 solids, the first one corresponding to materials calcined at moderate temperature whereas the other set apart solids annealed under severe conditions. As expected, no isokinetic temperature was observed in Arrhenius plots corresponding to alcohol dehydration over TiO2 materials.
Alumina-zirconia and alumina-titania mixed oxides were prepared by coprecipitation of their corre... more Alumina-zirconia and alumina-titania mixed oxides were prepared by coprecipitation of their corresponding chlorides. Samples were synthezised at several concentrations, dried and calcined at temperatures between 400°C and 800°C. All dried samples showed the bayerite structure, which upon calcination became first amorphous and later Al2O3. Anatase was observed only on the high content, high calcination temperature sample, but no crystalline phase
Pt–Sn supported on magnesia and alumina were characterized, before and after treatment with hydro... more Pt–Sn supported on magnesia and alumina were characterized, before and after treatment with hydrogen, by Mssbauer spectroscopy and X-ray diffraction. For the calcined samples on both supports tin is present as SnO2 and platinum as metal. After reduction with hydrogen, platinum and tin diffuse into the magnesia lattice to form a solid solution. On alumina Sn(IV), Sn(II), Sn(0), Pt, Pt3Sn, PtSn and PtSn2 alloys are formed. The SnO interacts strongly with the alumina support. The catalytic activity of both Pt–Sn catalysts is strongly affected by the support. On alumina the dehydrogenation of cyclohexane is very high, whereas that on magnesia is almost non-active.
Computer Aided Chemical Engineering, 2002
... of a Reactive Distillation Process For Ultra-Low Sulfur Diesel Production Eduardo S. Perez-Ci... more ... of a Reactive Distillation Process For Ultra-Low Sulfur Diesel Production Eduardo S. Perez-Cisneros^^'^^ Salvador A. Granados-Aguilar^*'^ Pedro Huitzil ... out carefully, because of the presence of Hi and H2S in the reacting mixture and a modified Peng-Robinson Equation ...
Studies in Surface Science and Catalysis, 1999
The deactivation by coke of Ni supported on alumina-titania was studied in the hydrogenation of p... more The deactivation by coke of Ni supported on alumina-titania was studied in the hydrogenation of phenylacetylene. The method of preparation of the support, precipitation or sol-gel, had an important effect on the activity, selectivity and deactivation rate. The process was modelled using a consecutive reaction scheme and assuming the parallel formation of coke with phenylacetylene as the precursor.
Studies in Surface Science and Catalysis, 2000
The strong metal support interaction for Ni catalysts supported on alumina-and silica-promoted Ti... more The strong metal support interaction for Ni catalysts supported on alumina-and silica-promoted TiO2 was studied in hydrogenation of phenylacetylene and dehydrogenation of cyclohexane. The catalytic performance is modified by the nature of promotor. The activity and selectivity in the consecutive hydrogenation of phenylacetylene is sensitive to the Al-and Si-promotion into the TiO2 matrix. The cyclohexane dehydrogenation shows that the differences in the SMSI behaviour of these catalysts are related to the modification of the metal support interaction by the presence of Al and Si. Additionally, the effect of Al and Si on the structural, textural, and acid-base surface properties of TiO2 was studied.
MRS Proceedings, 1998
Ni/(P)Ti-HMS catalysts were prepared and characterized by several physicochernical techniques. Th... more Ni/(P)Ti-HMS catalysts were prepared and characterized by several physicochernical techniques. The addition of phosphorous to the original mesoporous materials modified the acid-base surface properties. The activity in cyclohexane dehydrogenation is higher than on conventional catalysts.
Biodiesel - Feedstocks, Production and Applications, 2012
Avances En Ciencias E Ingenieria, 2012
Catalysis Today, Oct 30, 2009
El uso del método de micro-emulsión permitió obtener nano-catalizadores de Ni/SiO2 con la estruct... more El uso del método de micro-emulsión permitió obtener nano-catalizadores de Ni/SiO2 con la estructura requerida, debido a la interacción entre los componentes que forman la micro-emulsión (tensoactivo, fase acuosa y fase orgánica) y las sales precursoras disueltas en la fase acuosa, produce catalizadores que presentan propiedades texturales sobresalientes, basado en los resultados mostrados, por las diferentes técnicas usadas que indican que la descomposición térmica de los sólidos obtenidos, ocurre en diferentes etapas hasta obtener como producto final, óxidos de níquel (II) estables y dispersos en sílice, produciendo una opción atractiva para ser aplicadas en reacciones de hidrogenación.
Se observa una clara ventaja de actividad HDS de 4,6-DMDBT para los catalizadores NiMo soportados... more Se observa una clara ventaja de actividad HDS de 4,6-DMDBT para los catalizadores NiMo soportados en alúmina con un contenido de óxido de zirconio del 10 y 15% respectivamente.
Computer Aided Chemical Engineering, 2015
ABSTRACT An integrated reactive distillation process for the production of biodiesel is proposed.... more ABSTRACT An integrated reactive distillation process for the production of biodiesel is proposed. The reactive separation process consists of two coupled reactive distillation columns considering the kinetically controlled reactions of esterification of the fatty acids (FFAs) and the trans-esterification of the tri-di and mono glycerides with methanol, respectively. The conceptual design of each reactive distillation column was performed through the construction of reactive residue curve maps in terms of elements. The design of the esterification reactive distillation column consisted of one reactive zone loaded with a solid catalyst (titanium oxide supported on silica TiO 2 /SiO 2) and for the trans-esterification reactive column two reactive zones loaded with solid catalyst (hydrotalcites (CHT) and MgO). Intensive simulation of the integrated reactive process including the complex kinetic expressions for the different reactions and the Cubic-Plus Association (CPA) thermodynamic model was performed using the computational environment of ASPEN Plus. Results showed that the amount of fatty acids (FFAs) and water in the oil fed play a key role on the performance of the trans-esterification reactive distillation column while for the esterification column is not significant.
An approximate method to evaluate global effectiveness factor has been developed. It results from... more An approximate method to evaluate global effectiveness factor has been developed. It results from the inclusion of external mass transfer in an earlier method, which considered intraphase effectiveness factor estimations. The method, based on the approximation of the reaction rate above the surface concentrations, requires only the solution of an algebraic equation, instead of solving the differential one that defines
Studies in Surface Science and Catalysis, 1997
... 0.2 0.0 o. 1 0.2 oe 0.0 lectivity to the intermediate action product. re-Coke Content (rr~rng... more ... 0.2 0.0 o. 1 0.2 oe 0.0 lectivity to the intermediate action product. re-Coke Content (rr~rng cat.) Figure 5. Influence of the reduction temperature on ethylene selectivity. ... 13 JA Montoya, JC Rodriguez, I. Schifter, A. Monzon and T. Viveros, Stud. Surf. Sci. and Catal., 88 (1994) 531. ...
Studies in Surface Science and Catalysis, 1997
Studies in Surface Science and Catalysis, 2000
In order to assess the effect of various synthesis parameters and the presence of a second oxide ... more In order to assess the effect of various synthesis parameters and the presence of a second oxide (TiO2 or ZrO2) at different concentrations on the Al2O3 structure, the corresponding samples were prepared by low-temperature sol-gel method. The oxides were characterized by N2 physisorption, XRD and 27A1 MAS-NMR. In all samples calcined at Tc≤973 K four-, five- and six-coordinated aluminum were
Fuel, 2014
ABSTRACT Compensation effects were found in isopropanol dehydration over alumina (A), titania (T)... more ABSTRACT Compensation effects were found in isopropanol dehydration over alumina (A), titania (T) and corresponding mixed oxides (Al/Ti = 2 and 25 mol ratio, AT2 and AT25, respectively) synthesized by low-temperature sol-gel. Prepared materials (calcined in the 573-1173 K) range were characterized by several techniques (N2 physisorption, XRD, thermal analysis and SEM). In general, Al2O3 had the highest reaction rate (at 473 K) in propylene formation meanwhile both mixed oxides had much lower activity. TiO2 had minimal dehydrating activity that, nevertheless, was the highest intrinsic one (in areal basis). Constable plots were obtained for materials annealed at various temperatures, but for titania series. A clear isokinetic temperature (Tθ) was observed for alumina series whereas for AT25 materials, a Tθ pole was registered but for the sample calcined at the most severe condition. Meanwhile, two Tθ poles were identified for AT2 solids, the first one corresponding to materials calcined at moderate temperature whereas the other set apart solids annealed under severe conditions. As expected, no isokinetic temperature was observed in Arrhenius plots corresponding to alcohol dehydration over TiO2 materials.
Alumina-zirconia and alumina-titania mixed oxides were prepared by coprecipitation of their corre... more Alumina-zirconia and alumina-titania mixed oxides were prepared by coprecipitation of their corresponding chlorides. Samples were synthezised at several concentrations, dried and calcined at temperatures between 400°C and 800°C. All dried samples showed the bayerite structure, which upon calcination became first amorphous and later Al2O3. Anatase was observed only on the high content, high calcination temperature sample, but no crystalline phase
Pt–Sn supported on magnesia and alumina were characterized, before and after treatment with hydro... more Pt–Sn supported on magnesia and alumina were characterized, before and after treatment with hydrogen, by Mssbauer spectroscopy and X-ray diffraction. For the calcined samples on both supports tin is present as SnO2 and platinum as metal. After reduction with hydrogen, platinum and tin diffuse into the magnesia lattice to form a solid solution. On alumina Sn(IV), Sn(II), Sn(0), Pt, Pt3Sn, PtSn and PtSn2 alloys are formed. The SnO interacts strongly with the alumina support. The catalytic activity of both Pt–Sn catalysts is strongly affected by the support. On alumina the dehydrogenation of cyclohexane is very high, whereas that on magnesia is almost non-active.
Computer Aided Chemical Engineering, 2002
... of a Reactive Distillation Process For Ultra-Low Sulfur Diesel Production Eduardo S. Perez-Ci... more ... of a Reactive Distillation Process For Ultra-Low Sulfur Diesel Production Eduardo S. Perez-Cisneros^^'^^ Salvador A. Granados-Aguilar^*'^ Pedro Huitzil ... out carefully, because of the presence of Hi and H2S in the reacting mixture and a modified Peng-Robinson Equation ...
Studies in Surface Science and Catalysis, 1999
The deactivation by coke of Ni supported on alumina-titania was studied in the hydrogenation of p... more The deactivation by coke of Ni supported on alumina-titania was studied in the hydrogenation of phenylacetylene. The method of preparation of the support, precipitation or sol-gel, had an important effect on the activity, selectivity and deactivation rate. The process was modelled using a consecutive reaction scheme and assuming the parallel formation of coke with phenylacetylene as the precursor.
Studies in Surface Science and Catalysis, 2000
The strong metal support interaction for Ni catalysts supported on alumina-and silica-promoted Ti... more The strong metal support interaction for Ni catalysts supported on alumina-and silica-promoted TiO2 was studied in hydrogenation of phenylacetylene and dehydrogenation of cyclohexane. The catalytic performance is modified by the nature of promotor. The activity and selectivity in the consecutive hydrogenation of phenylacetylene is sensitive to the Al-and Si-promotion into the TiO2 matrix. The cyclohexane dehydrogenation shows that the differences in the SMSI behaviour of these catalysts are related to the modification of the metal support interaction by the presence of Al and Si. Additionally, the effect of Al and Si on the structural, textural, and acid-base surface properties of TiO2 was studied.
MRS Proceedings, 1998
Ni/(P)Ti-HMS catalysts were prepared and characterized by several physicochernical techniques. Th... more Ni/(P)Ti-HMS catalysts were prepared and characterized by several physicochernical techniques. The addition of phosphorous to the original mesoporous materials modified the acid-base surface properties. The activity in cyclohexane dehydrogenation is higher than on conventional catalysts.
Biodiesel - Feedstocks, Production and Applications, 2012