Gonzalo Aguila - Academia.edu (original) (raw)

Papers by Gonzalo Aguila

The selective reduction of NO with CO and naphthalene was investigated using a core-shell CeO2@Ti... more The selective reduction of NO with CO and naphthalene was investigated using a core-shell CeO2@TiO2 support impregnated with copper and potassium. The selective character of the reaction was due to the presence of oxygen, which induces the unwanted oxidation of CO and/or naphthalene. The latter constitutes a challenge in the reduction of NO because most of combustion processes occur in oxidizing atmospheres. The underway work shows that both Cu/SmCeO2@TiO2 and K/Cu/SmCeO2@TiO2 catalysts are able to achieve full conversion of NO at temperatures higher than 225 o C and 325 o C, respectively.

Applied Catalysis B: Environmental, 2012

The effect of surface area of copper/zirconia adsorbents on the adsorption of thiophene (T) and d... more The effect of surface area of copper/zirconia adsorbents on the adsorption of thiophene (T) and dibenzothiophene (DBT) was studied. Adsorbents were prepared with different loads of copper (1-6%), using as support zirconias with different surface areas, obtained by varying the calcination temperature. Lower calcination temperatures allowed obtaining zirconias with higher surface area, but lower crystallinity. The characterization results showed that high surface area zirconias have greater copper dispersion capacity, being the zirconia calcined at the lower temperature, the only able to completely disperse a load of 6% Cu, i.e., Z-300 surface has only highly dispersed copper species, while zirconias with higher calcination temperature have also bulk CuO species. The adsorption capacity of T or DBT on Cu/ZrO 2 increased with copper content, reaching a maximum, which coincides remarkably with the zirconia dispersion capacity. This result indicates that dispersed copper species, in Cu 1+ state, are responsible for the adsorption of these sulfur organic compounds. Therefore the best adsorption capacities were obtained in adsorbents with high content of such copper species, and these adsorbent can be prepared with high surface area ZrO 2 , that is with high dispersion capacity of copper.

Applied Catalysis A: General, 2006

The structural stability of a commercial hydrous zirconia and a hydrous zirconia synthesized in o... more The structural stability of a commercial hydrous zirconia and a hydrous zirconia synthesized in our laboratory by the sol-gel method has been improved by a post-synthesis reflux treatment with aqueous NH 4 OH and NaOH solutions (100 8C for 9 h). Direct calcination of both materials at 700 8C for 3 h, rendered zirconium oxides with a mixture of monoclinic and tetragonal structures and specific areas of 36 and 27 m 2 /g, respectively. In contrast, if the materials were refluxed before calcination with NaOH or NH 4 OH solutions, zirconium oxides with tetragonal structure and specific areas between 90 and 200 m 2 /g were obtained after calcination at 700 8C. In the treatments with NaOH solution, addition of Si coming from dissolution of the flask glass walls or from an external Si source in a plastic flask is responsible for the stability of the final zirconium oxides. Nevertheless, the porous structure of these materials is determined by the treatment conditions in basic solution, thus allowing to control the physical properties of the final oxide. Short treatment times are sufficient to stabilize the hydrous zirconia. On the contrary, if the reflux is made with a NH 4 OH solution, the stabilization mechanism appears to be different since there is no evidence of Si addition in the oxides. In this case, the pore size distribution strongly depends on the reflux time, and the highest specific area is obtained for the largest treatment time (9 h).

Applied Catalysis A: General, 2008

The effect of the support, Al 2 O 3 , ZrO 2 , and SiO 2 , on the activity for CO oxidation of a s... more The effect of the support, Al 2 O 3 , ZrO 2 , and SiO 2 , on the activity for CO oxidation of a series of CuO and CeO 2 monometallic and bimetallic catalysts was studied. The catalysts were prepared by coimpregnation of the support with the adequate amount of Cu and Ce nitrates to obtain a loading of 2% Cu and/or 8% Ce. It was found that the support has a strong influence on the activity of the different bimetallic catalysts. Interestingly, the SiO 2 supported catalyst shows the higher activity. The bimetallic supported catalysts follow the activity sequence CuO-CeO 2 /SiO 2 > CuO-CeO 2 /ZrO 2 > CuO-CeO 2 /Al 2 O 3. In the absence of CeO 2 , the most active monometallic catalyst was the CuO/ZrO 2 system. The different degree of interaction between CuO and CeO 2 particles, induced by the support, can explain the activity results for the bimetallic catalysts.

Applied Catalysis A: General, 2009

... In order to accurately determine the BE of the different element core levels, high resolution... more ... In order to accurately determine the BE of the different element core levels, high resolution spectra were always fitted using Gaussian–Lorentzian curves. Prior to curve fitting, a background was subtracted by the method devised by Shirley [22]. ...

RSC Advances

CuO–CeO2/SiO2 catalysts with Ce loading of 24% and above keep high activity after calcination at ... more CuO–CeO2/SiO2 catalysts with Ce loading of 24% and above keep high activity after calcination at 700 °C. Therefore, a catalyst with high thermal stability of CuO–CeO2 interface can be obtained able to work in a higher range of temperatures.

Water, Air, & Soil Pollution

Journal of the Chilean Chemical Society

The effect of the support on the formation of the Cu-CeO 2 interface and its thermal stability af... more The effect of the support on the formation of the Cu-CeO 2 interface and its thermal stability after calcination at 500, 700 and 900 ºC is studied. The supports used are SiO 2 , because of its inert character, and Al 2 O 3 , because it can interact with the Cu and Ce species on the surface. The catalysts were characterized by BET, XRD, UV-vis DRS, and TPR with H 2. The catalytic activity in the CO oxidation reactions with O 2 at low temperature and the decomposition of N 2 O were selected to visualize the effect of temperature on the concentration of Cu-CeO 2 interfacial sites. The results show that at a calcination temperature of 500 ºC the formation of the Cu-CeO 2 interface is favored over the SiO 2 support. However, the stability of the Cu-CeO 2 interface on SiO 2 is much lower than on Al 2 O 3 , causing a substantial decrease of the interfacial sites calcining at 700 ºC, and segregation of the Cu and Ce species on the surface of the silica, with complete loss of the catalytic activity in both reactions when calcining at 900 ºC. In contrast, on alumina the Cu-CeO 2 interface is more stable and presents a significant catalytic activity in both reactions, even when calcining at 900 ºC. The characterization results show that the sintering process of Cu species and CeO 2 particles is less on the alumina support due to the greater interaction of the Cu and Ce with this support.

Processes

The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based ... more The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic migration, and X-ray diffraction. The results showed that the adsorbent containing nickel had better adsorption capacity than the adsorbent modified with nickel and boron, which was attributed to its greater acidity and ability to generate π-complexation between the adsorbent and the molecules. In terms of selectivity, quinoline was more adsorbed than 4,6-dimethyldibenzothiophene in all systems, due to the basic nature of quinoline. The experimental data in all cases were adjusted by three kinetic models (Yoon–Nelson, Yan and Thomas), and the regression coefficients in all models were close to one. Finally, the values of the kinetic constant obtained by...

Catalysis Science & Technology

This work studied the reaction of common pollutants on a catalytic surface under oxidizing condit... more This work studied the reaction of common pollutants on a catalytic surface under oxidizing conditions. CO and naphthalene were used to reduce NO in the presence of oxygen during the...

Journal of the Chilean Chemical Society

The activity of Fe 2 O 3 /Al 2 O 3 catalysts prepared by impregnation of Al 2 O 3 with different ... more The activity of Fe 2 O 3 /Al 2 O 3 catalysts prepared by impregnation of Al 2 O 3 with different amounts of Fe and calcination temperatures (650 and 900 ºC) in the direct N 2 O decomposition reaction was studied. High calcination temperature was introduced to study the effect of "aging", which are the conditions prevailing in the process-gas option for N 2 O abatement. The catalysts were characterized by BET, XRD, UV-DRS, and H 2-TPR. The incorporation of Fe promotes the alumina phase transition (g-Al 2 O 3 to a-Al 2 O 3) when the catalysts are calcined at 900 ºC, which is accompanied by a decrease in the specific area. The activity of the catalysts and the specific surface area depend on Fe loading and calcination temperature. It was found that highly dispersed Fe species are more active than bulk type Fe 2 O 3 particles. We conclude that Fe 2 O 3 /Al 2 O 3 catalysts prepared by impregnation method are active in the decomposition of N 2 O, to be used at low or high reaction temperatures (tail-gas or process-gas treatments, respectively), as part of nitric acid production plant.

Materials Chemistry and Physics

Materials Chemistry and Physics

Journal of the Chilean Chemical Society, 2016

We studied the effect of the alkali metal type (Li, Na, and K) and the calcination temperature (5... more We studied the effect of the alkali metal type (Li, Na, and K) and the calcination temperature (500, 600 and 700 °C) in the activity for biodiesel production of catalysts prepared by impregnation method, with constant metal content of 10%w/w using ZrO 2 as support. The results of the catalytic activity allowed to find an activity sequence regarding the alkali tested metals: Na > Li > K, with this sequence remaining constant independent of the calcination temperature. The high activity of the Na/ZrO 2 system, and slightly lower activity of Li/ZrO 2 , can be explained by the fact that higher calcination temperatures promote the formation of alkali-based zirconate species, M 2 ZrO 3 (M = Na or Li). The presence of these species is correlated with the higher activity of these catalysts, specifically with the Na and Li-based catalyst calcined at high temperatures (600-700 °C). These M 2 ZrO 3 species show higher basicity respect to other alkali metal oxide species, as was demonstrated with CO 2-TPD results. The higher activity corresponded to 10% Na supported on ZrO 2 and calcined at 700 °C, which reached full conversion within just 30 minutes of reaction, which makes this system a promising heterogeneous replacement for the regular homogeneous systems.

Catalysis Letters, 2008

An experimental study is made of the time decay of activity of the CO-NO reaction on a Pd/Al 2 O ... more An experimental study is made of the time decay of activity of the CO-NO reaction on a Pd/Al 2 O 3 looking at the effect on reaction order and apparent activation energy. The optimum kinetics parameters fitting the steady state data at moderate pressures are determined. The time decay curves are analyzed through various catalyst deactivation models.

Catalysis Communications, 2012

The simultaneous presence of sodium and copper on novel Na/Cu/CeO 2 and Na/Cu/CeY catalysts resul... more The simultaneous presence of sodium and copper on novel Na/Cu/CeO 2 and Na/Cu/CeY catalysts resulted in a dramatic increase in the catalytic adsorption of NO. Copper catalyzes the oxidation of NO to NO 2 , which is further adsorbed by the sodium phase. The intimate contact of both phases favors the formation of nitrates on the surface. The cooperative effect between the copper and sodium phases increases the reduction temperature of copper. It was found that the addition of copper induced a stabilizing effect on the surface area of the catalysts.

Catalysis Communications, 2013

The activity in the WGS reaction of Cu/ZrO 2 catalysts prepared by a method of refluxing in an aq... more The activity in the WGS reaction of Cu/ZrO 2 catalysts prepared by a method of refluxing in an aqueous NH 4 OH solution is studied. It is shown that at 3% Cu load the methods of impregnation over monoclinic or tetragonal ZrO 2 do not produce active catalysts for the WGS reaction. However, the method of refluxing generates highly active catalysts with Cu loads of 3% (w/w) or higher. The activity of the catalysts prepared by refluxing is associated with the formation of small Cu clusters, which would allow the regrouping of the H atoms to generate molecular H 2 in the presence of the crystalline tetragonal ZrO 2 .

Catalysis Communications, 2008

The structure sensitivity of copper catalysts supported on monoclinic and tetragonal ZrO2 was stu... more The structure sensitivity of copper catalysts supported on monoclinic and tetragonal ZrO2 was studied on the water gas shift (WGS) reaction. The results show that the activity of copper supported on tetragonal ZrO2 is much higher than when supported on monoclinic ZrO2. The obtained results favour an associative mechanism, which considers the formation of formate species on the surface of

The selective reduction of NO with CO and naphthalene was investigated using a core-shell CeO2@Ti... more The selective reduction of NO with CO and naphthalene was investigated using a core-shell CeO2@TiO2 support impregnated with copper and potassium. The selective character of the reaction was due to the presence of oxygen, which induces the unwanted oxidation of CO and/or naphthalene. The latter constitutes a challenge in the reduction of NO because most of combustion processes occur in oxidizing atmospheres. The underway work shows that both Cu/SmCeO2@TiO2 and K/Cu/SmCeO2@TiO2 catalysts are able to achieve full conversion of NO at temperatures higher than 225 o C and 325 o C, respectively.

Applied Catalysis B: Environmental, 2012

The effect of surface area of copper/zirconia adsorbents on the adsorption of thiophene (T) and d... more The effect of surface area of copper/zirconia adsorbents on the adsorption of thiophene (T) and dibenzothiophene (DBT) was studied. Adsorbents were prepared with different loads of copper (1-6%), using as support zirconias with different surface areas, obtained by varying the calcination temperature. Lower calcination temperatures allowed obtaining zirconias with higher surface area, but lower crystallinity. The characterization results showed that high surface area zirconias have greater copper dispersion capacity, being the zirconia calcined at the lower temperature, the only able to completely disperse a load of 6% Cu, i.e., Z-300 surface has only highly dispersed copper species, while zirconias with higher calcination temperature have also bulk CuO species. The adsorption capacity of T or DBT on Cu/ZrO 2 increased with copper content, reaching a maximum, which coincides remarkably with the zirconia dispersion capacity. This result indicates that dispersed copper species, in Cu 1+ state, are responsible for the adsorption of these sulfur organic compounds. Therefore the best adsorption capacities were obtained in adsorbents with high content of such copper species, and these adsorbent can be prepared with high surface area ZrO 2 , that is with high dispersion capacity of copper.

Applied Catalysis A: General, 2006

The structural stability of a commercial hydrous zirconia and a hydrous zirconia synthesized in o... more The structural stability of a commercial hydrous zirconia and a hydrous zirconia synthesized in our laboratory by the sol-gel method has been improved by a post-synthesis reflux treatment with aqueous NH 4 OH and NaOH solutions (100 8C for 9 h). Direct calcination of both materials at 700 8C for 3 h, rendered zirconium oxides with a mixture of monoclinic and tetragonal structures and specific areas of 36 and 27 m 2 /g, respectively. In contrast, if the materials were refluxed before calcination with NaOH or NH 4 OH solutions, zirconium oxides with tetragonal structure and specific areas between 90 and 200 m 2 /g were obtained after calcination at 700 8C. In the treatments with NaOH solution, addition of Si coming from dissolution of the flask glass walls or from an external Si source in a plastic flask is responsible for the stability of the final zirconium oxides. Nevertheless, the porous structure of these materials is determined by the treatment conditions in basic solution, thus allowing to control the physical properties of the final oxide. Short treatment times are sufficient to stabilize the hydrous zirconia. On the contrary, if the reflux is made with a NH 4 OH solution, the stabilization mechanism appears to be different since there is no evidence of Si addition in the oxides. In this case, the pore size distribution strongly depends on the reflux time, and the highest specific area is obtained for the largest treatment time (9 h).

Applied Catalysis A: General, 2008

The effect of the support, Al 2 O 3 , ZrO 2 , and SiO 2 , on the activity for CO oxidation of a s... more The effect of the support, Al 2 O 3 , ZrO 2 , and SiO 2 , on the activity for CO oxidation of a series of CuO and CeO 2 monometallic and bimetallic catalysts was studied. The catalysts were prepared by coimpregnation of the support with the adequate amount of Cu and Ce nitrates to obtain a loading of 2% Cu and/or 8% Ce. It was found that the support has a strong influence on the activity of the different bimetallic catalysts. Interestingly, the SiO 2 supported catalyst shows the higher activity. The bimetallic supported catalysts follow the activity sequence CuO-CeO 2 /SiO 2 > CuO-CeO 2 /ZrO 2 > CuO-CeO 2 /Al 2 O 3. In the absence of CeO 2 , the most active monometallic catalyst was the CuO/ZrO 2 system. The different degree of interaction between CuO and CeO 2 particles, induced by the support, can explain the activity results for the bimetallic catalysts.

Applied Catalysis A: General, 2009

... In order to accurately determine the BE of the different element core levels, high resolution... more ... In order to accurately determine the BE of the different element core levels, high resolution spectra were always fitted using Gaussian–Lorentzian curves. Prior to curve fitting, a background was subtracted by the method devised by Shirley [22]. ...

RSC Advances

CuO–CeO2/SiO2 catalysts with Ce loading of 24% and above keep high activity after calcination at ... more CuO–CeO2/SiO2 catalysts with Ce loading of 24% and above keep high activity after calcination at 700 °C. Therefore, a catalyst with high thermal stability of CuO–CeO2 interface can be obtained able to work in a higher range of temperatures.

Water, Air, & Soil Pollution

Journal of the Chilean Chemical Society

The effect of the support on the formation of the Cu-CeO 2 interface and its thermal stability af... more The effect of the support on the formation of the Cu-CeO 2 interface and its thermal stability after calcination at 500, 700 and 900 ºC is studied. The supports used are SiO 2 , because of its inert character, and Al 2 O 3 , because it can interact with the Cu and Ce species on the surface. The catalysts were characterized by BET, XRD, UV-vis DRS, and TPR with H 2. The catalytic activity in the CO oxidation reactions with O 2 at low temperature and the decomposition of N 2 O were selected to visualize the effect of temperature on the concentration of Cu-CeO 2 interfacial sites. The results show that at a calcination temperature of 500 ºC the formation of the Cu-CeO 2 interface is favored over the SiO 2 support. However, the stability of the Cu-CeO 2 interface on SiO 2 is much lower than on Al 2 O 3 , causing a substantial decrease of the interfacial sites calcining at 700 ºC, and segregation of the Cu and Ce species on the surface of the silica, with complete loss of the catalytic activity in both reactions when calcining at 900 ºC. In contrast, on alumina the Cu-CeO 2 interface is more stable and presents a significant catalytic activity in both reactions, even when calcining at 900 ºC. The characterization results show that the sintering process of Cu species and CeO 2 particles is less on the alumina support due to the greater interaction of the Cu and Ce with this support.

Processes

The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based ... more The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic migration, and X-ray diffraction. The results showed that the adsorbent containing nickel had better adsorption capacity than the adsorbent modified with nickel and boron, which was attributed to its greater acidity and ability to generate π-complexation between the adsorbent and the molecules. In terms of selectivity, quinoline was more adsorbed than 4,6-dimethyldibenzothiophene in all systems, due to the basic nature of quinoline. The experimental data in all cases were adjusted by three kinetic models (Yoon–Nelson, Yan and Thomas), and the regression coefficients in all models were close to one. Finally, the values of the kinetic constant obtained by...

Catalysis Science & Technology

This work studied the reaction of common pollutants on a catalytic surface under oxidizing condit... more This work studied the reaction of common pollutants on a catalytic surface under oxidizing conditions. CO and naphthalene were used to reduce NO in the presence of oxygen during the...

Journal of the Chilean Chemical Society

The activity of Fe 2 O 3 /Al 2 O 3 catalysts prepared by impregnation of Al 2 O 3 with different ... more The activity of Fe 2 O 3 /Al 2 O 3 catalysts prepared by impregnation of Al 2 O 3 with different amounts of Fe and calcination temperatures (650 and 900 ºC) in the direct N 2 O decomposition reaction was studied. High calcination temperature was introduced to study the effect of "aging", which are the conditions prevailing in the process-gas option for N 2 O abatement. The catalysts were characterized by BET, XRD, UV-DRS, and H 2-TPR. The incorporation of Fe promotes the alumina phase transition (g-Al 2 O 3 to a-Al 2 O 3) when the catalysts are calcined at 900 ºC, which is accompanied by a decrease in the specific area. The activity of the catalysts and the specific surface area depend on Fe loading and calcination temperature. It was found that highly dispersed Fe species are more active than bulk type Fe 2 O 3 particles. We conclude that Fe 2 O 3 /Al 2 O 3 catalysts prepared by impregnation method are active in the decomposition of N 2 O, to be used at low or high reaction temperatures (tail-gas or process-gas treatments, respectively), as part of nitric acid production plant.

Materials Chemistry and Physics

Materials Chemistry and Physics

Journal of the Chilean Chemical Society, 2016

We studied the effect of the alkali metal type (Li, Na, and K) and the calcination temperature (5... more We studied the effect of the alkali metal type (Li, Na, and K) and the calcination temperature (500, 600 and 700 °C) in the activity for biodiesel production of catalysts prepared by impregnation method, with constant metal content of 10%w/w using ZrO 2 as support. The results of the catalytic activity allowed to find an activity sequence regarding the alkali tested metals: Na > Li > K, with this sequence remaining constant independent of the calcination temperature. The high activity of the Na/ZrO 2 system, and slightly lower activity of Li/ZrO 2 , can be explained by the fact that higher calcination temperatures promote the formation of alkali-based zirconate species, M 2 ZrO 3 (M = Na or Li). The presence of these species is correlated with the higher activity of these catalysts, specifically with the Na and Li-based catalyst calcined at high temperatures (600-700 °C). These M 2 ZrO 3 species show higher basicity respect to other alkali metal oxide species, as was demonstrated with CO 2-TPD results. The higher activity corresponded to 10% Na supported on ZrO 2 and calcined at 700 °C, which reached full conversion within just 30 minutes of reaction, which makes this system a promising heterogeneous replacement for the regular homogeneous systems.

Catalysis Letters, 2008

An experimental study is made of the time decay of activity of the CO-NO reaction on a Pd/Al 2 O ... more An experimental study is made of the time decay of activity of the CO-NO reaction on a Pd/Al 2 O 3 looking at the effect on reaction order and apparent activation energy. The optimum kinetics parameters fitting the steady state data at moderate pressures are determined. The time decay curves are analyzed through various catalyst deactivation models.

Catalysis Communications, 2012

The simultaneous presence of sodium and copper on novel Na/Cu/CeO 2 and Na/Cu/CeY catalysts resul... more The simultaneous presence of sodium and copper on novel Na/Cu/CeO 2 and Na/Cu/CeY catalysts resulted in a dramatic increase in the catalytic adsorption of NO. Copper catalyzes the oxidation of NO to NO 2 , which is further adsorbed by the sodium phase. The intimate contact of both phases favors the formation of nitrates on the surface. The cooperative effect between the copper and sodium phases increases the reduction temperature of copper. It was found that the addition of copper induced a stabilizing effect on the surface area of the catalysts.

Catalysis Communications, 2013

The activity in the WGS reaction of Cu/ZrO 2 catalysts prepared by a method of refluxing in an aq... more The activity in the WGS reaction of Cu/ZrO 2 catalysts prepared by a method of refluxing in an aqueous NH 4 OH solution is studied. It is shown that at 3% Cu load the methods of impregnation over monoclinic or tetragonal ZrO 2 do not produce active catalysts for the WGS reaction. However, the method of refluxing generates highly active catalysts with Cu loads of 3% (w/w) or higher. The activity of the catalysts prepared by refluxing is associated with the formation of small Cu clusters, which would allow the regrouping of the H atoms to generate molecular H 2 in the presence of the crystalline tetragonal ZrO 2 .

Catalysis Communications, 2008

The structure sensitivity of copper catalysts supported on monoclinic and tetragonal ZrO2 was stu... more The structure sensitivity of copper catalysts supported on monoclinic and tetragonal ZrO2 was studied on the water gas shift (WGS) reaction. The results show that the activity of copper supported on tetragonal ZrO2 is much higher than when supported on monoclinic ZrO2. The obtained results favour an associative mechanism, which considers the formation of formate species on the surface of