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Papers by Alessandra Fonseca Lucrédio

Catalysis Science & Technology, 2021

The oxidative coupling of methane reaction to produce C2 compounds was studied using La2(Ce1−xMgx... more The oxidative coupling of methane reaction to produce C2 compounds was studied using La2(Ce1−xMgx)2O7−δ catalysts with disordered defective cubic fluorite structures, varying the Mg content (0.0 ≤ x ≤ 1.0), CH4/O2 ratio, temperature, and WHSV.

Catalysis Letters, 2022

Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the ... more Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the role of gadolinium on ethanol conversion, H2 selectivity, and carbon formation on ethanol steam reforming reaction. For this, catalysts containing 5 wt% of Ni impregnated on supports of ceria modified with different amounts of Gd (1, 5, and 10 wt%) were used. Ex-situ studies of XRPD suggest an increase of the lattice parameters, indicating a solid solution formation between Gd and Ce. Results of TPR showed an increase in metal-support interactions as the content of Gd increased. In situ XRPD studies indicated the formation of a GdNiO ternary phase for the catalysts containing Gd, which is in agreement with the results obtained by XANES. The catalysts were tested at three temperatures: 400 °C, 500 °C, and 600 °C. The conversion and productivity showed dependence with the Gd content and also with the temperature of the reaction. After the catalytic tests, catalysts containing Gd presented filamentous carbon possible due to a change in the reaction pathway. The highest ethanol conversion and H2 productivity were obtained at 600 °C for all catalysts and the best catalyst at this temperature was 5Ni_5GdCeO2. The promising performance of this catalyst may be associate with the lowest formation of GdNiO ternary phase, among the catalysts containing Gd, which means more Ni0 active species available to convert ethanol.

Functional Properties of Advanced Engineering Materials and Biomolecules, 2021

The development of society is dependent on commodities such as fuels and chemical feedstock. Most... more The development of society is dependent on commodities such as fuels and chemical feedstock. Most of these commodities are obtained from oil as raw material. Although the need to find a friendly solution to couple an economically viable energy model with a greener solution, it is known that technologies applying renewable sources are in an early stage of development. The conversion of methane into clean fuels or chemical feedstock with high commercial value, such as hydrogen, ethylene, or methanol is interesting from the energetic and economic point-of-view. Among the methods of methane conversion, the industrially used is the steam reforming (MSR), in which methane reacts with water to produce syngas, a mixture of CO and H 2. Nevertheless, this reaction is highly endothermic and responsible for a large volume of CO 2 emitted by the reactor burners that provide energy to the reactors. An interesting alternative process for methane conversion is the dry reforming of methane (DRM), which consists of the reaction of methane with CO 2 , also yielding syngas. The advantage of this reaction is the utilization of two harmful gases to the atmosphere. The disadvantage of this reaction is due to the catalyst deactivation by carbon deposition. In heterogeneous catalysis, there is a strong relationship between catalytic performance and surface and textural properties, that are outlined by the number and distribution of available active sites. In this way, different synthetic routes may be used to design these properties and obtain products of commercial interest, such as ethylene. The commercial production of ethylene occurs by the recuperation of refinery gases, thermal cracking of light hydrocarbons, mainly ethane and propane, or a combination of both processes. An alternative process of ethylene production may be from natural gas and or biogas. This process can be performed by the syngas

Journal of Chemical Engineering, 2015

Molecular Catalysis, 2020

The metal-containing vanadate nanotubes namely MeVO-NT (Me = Ni, Co or Pt) were in situ transform... more The metal-containing vanadate nanotubes namely MeVO-NT (Me = Ni, Co or Pt) were in situ transformed into vanadate oxides nanostructures i.e., MeV x O y , during the methane dry reforming. All the experimental observations through Raman, HRTEM, XRD, XPS, SEM-EDS, TG-FTIR and elemental analysis, strongly suggested that the VO x (MeV 2 O 7 , V 2 O 5 and VO 2) support contained the metal species that were involved in the dry reforming of methane (DRM) reaction. The pristine VO-NT catalyst exhibited a fairly low activity in DRM due to its degradation. In the case of CoVO-NT, the Co 3 O 4 /VO 2 , Co 3 O 4 /Co 2 V 2 O 7 and Co 3 O 4 /V 2 O 5 phases were deactivated by oxidation of the Co particles, instead of being deactivated by sintering and coking, as well. In contrast to CoVO-NT, PtVO-NT having PtO x /V 2 O 5 , PtO x /VO 2 or even PtO x /V 2 O 7 phases inhibited heavy carbonaceous deposition on surface, but sintering was not avoided. The NiVO-NT was active due to the stability of the Ni°/ Ni 2 V 2 O 7 active phase in hindering heavy whisker and filamentous carbonaceous deposits on such catalyst. Using Halgren-Lipscomb algorithm in the frame of density functional theory (DFT), transition states energy for all three catalysts were obtained. It was found that PtVO-NT energy profile was lower than CoVO-NT and NiVO-NT counterparts. This suggested that the Pt sites dispersed on VO x structure was catalytic active during the methane activation in DRM whereas the CoVO-NT and CoVO-NT solids were prone to perform side reactions.

Materials Research Bulletin, 2018

Highlights 1) The oxides mixture containing NiO, ZnO, Al 2 O 3 , NiAl 2 O 4 and ZnAl 2 O 4 was de... more Highlights 1) The oxides mixture containing NiO, ZnO, Al 2 O 3 , NiAl 2 O 4 and ZnAl 2 O 4 was detected. 2) The results exhibited intermediate interactions between Ni 0 and other phases. 3) Dry reforming of methane was applied to production of synthesis gas. 4) Deposition of the carbon filamentous on the catalysts surface was observed.

Fuel Processing Technology, 2014

Nickel catalysts were prepared on single-oxide supports of Al 2 O 3 , CeO 2 , MgO and ZrO 2 by im... more Nickel catalysts were prepared on single-oxide supports of Al 2 O 3 , CeO 2 , MgO and ZrO 2 by impregnation of the oxide with a solution of Ni(NO 3) 2 in methanol. The catalysts were characterized by N 2 physisorption (BET method), TPR, XRD, SEM and Raman spectroscopy and tested in dry reforming of ethanol (DRE). It was observed that the interaction with the support and Ni reducibility depended on the support used. According to TPR results, NiO species supported on CeO 2 and Al 2 O 3 were the easiest to reduce. Possibly, this behavior combined to redox properties of CeO 2 inhibited side undesirable reactions and contributed to the higher selectivity for H 2 on the NiCe catalyst. The catalytic test at 750°C on NiCe showed better H 2 selectivity than the test at 700°C, suggesting that the higher temperature enhanced CO 2 conversion and hindered carbon deposition in dry reforming of ethanol reactions.

RSC Adv., 2016

Pillared interlayer clay (PILC) is a low cost material, which is characterized by a large specifi... more Pillared interlayer clay (PILC) is a low cost material, which is characterized by a large specific surface area, high pore volume and surface acidity that make it effective in catalytic reactions.

Chemical Engineering Journal, 2016

h i g h l i g h t s Decoration of Co or Ni into titanate nanotubes and partial incorporation of P... more h i g h l i g h t s Decoration of Co or Ni into titanate nanotubes and partial incorporation of Pt. Transformation of titanate nanotubes during dry reforming of methane. Catalytic activity affected by the nature of the active sites. Surface Ni°sites on NiTiO 3 exhibited high CH 4 and CO 2 conversions.

Fuel Processing Technology, 2014

Abstract Ni/Al 2 O 3 catalysts promoted by adding La 2 O 3 , La 2 O 3 –CeO 2 and La 2 O 3 –ZrO 2 ... more Abstract Ni/Al 2 O 3 catalysts promoted by adding La 2 O 3 , La 2 O 3 –CeO 2 and La 2 O 3 –ZrO 2 were investigated on oxidative and steam reforming aiming the hydrogen production. The samples were characterized by surface area estimation (BET), XRD, TPR, TPD-H 2 and XANES. Analysis of TEM and TPO was performed as complementary characterization for catalysts after reaction. The oxidative steam reforming of methane at temperatures above 500 °C reveals that all the promoted catalysts presented better activities than the unpromoted. Below 500 °C, the catalysts presented deactivation due to metallic nickel species oxidation and the TEM analysis of Ni/Al and Ni/La–Al catalysts revealed that the lanthanum addition led to a decrease in the Ni species particle size and also to a better active phase dispersion. The results suggest that below 500 °C the activity may be related to differences in the metallic area values, although the Ni/La 2 O 3 –Al 2 O 3 catalysts have shown a different behavior.

International Journal of Hydrogen Energy, 2013

Ni/Al 2 O 3 catalysts containing 5 wt% of Ni and modified by addition of CaO (0e5 wt%) were teste... more Ni/Al 2 O 3 catalysts containing 5 wt% of Ni and modified by addition of CaO (0e5 wt%) were tested in ethanol steam reforming reaction in order to reduce the dehydration ethanol reaction, which produces ethylene that may polymerize and produce coke. The catalysts were prepared by impregnation (I) and co-precipitation (C) methods. All catalysts were investigated for ethanol steam reforming and the catalytic performance was compared in terms of additive addition. The catalysts 5Nie5Ca/Al (I) and 5Nie5Ca/Al (C) were less selective to ethylene production and therefore were characterized by the following techniques: energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray absorption near edge structure (XANES), specific surface area by the BET method, scanning electron microcopy (SEM) and isopropanol decomposition reaction. By comparing the catalysts, the 5Nie5Ca/Al (I) catalyst presented the lowest acidity and carbon deposition, and also presented no deactivation in 24 h of catalytic test.

Fuel, 2011

Cobalt catalysts were prepared on supports of SiO 2 and c-Al 2 O 3 by the impregnation method, us... more Cobalt catalysts were prepared on supports of SiO 2 and c-Al 2 O 3 by the impregnation method, using a solution of Co precursor in methanol. The samples were characterized by XRD, TPR, and Raman spectroscopy and tested in ethanol steam reforming. According to the XRD results, impregnation with the methanolic solution led to smaller metal crystallites than with aqueous solution, on the SiO 2 support. On c-Al 2 O 3 , all the samples exhibited small crystallites, with either solvent, due to a higher Co-support interaction that inhibits the reduction of Co species. The TPR results were consistent with XRD results and the samples supported on c-Al 2 O 3 showed a lower degree of reduction. In the steam reforming of ethanol, catalysts supported on SiO 2 and prepared with the methanolic solution showed the best H 2 , CO 2 and CO selectivity. Those supported on c-Al 2 O 3 showed lower H 2 selectivity.

Fuel Processing Technology, 2012

In this study, catalysts containing 5 wt.% Ni deposited on a support composed of a CeO 2-ZrO 2 so... more In this study, catalysts containing 5 wt.% Ni deposited on a support composed of a CeO 2-ZrO 2 solid solution deposited on alumina were tested in the steam reforming of methane. The supports, with various ratios of Ce to Zr, were prepared by co-precipitation of the oxide precursors, followed by calcination in synthetic air. The catalysts were then prepared by Ni impregnation of the supports. The prepared solids were characterized by temperature-programmed reduction with H 2 (TPR-H 2), in situ X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES) spectroscopy. The XRD analysis confirmed the formation of a solid solution between ZrO 2 and CeO 2. In the catalytic tests, it was found that catalysts with higher Ce content did not exhibit deactivation during 6 h of reaction. The catalyst with highest Ce content, Ni(0.8 Ce 0.2 Zr)Al, provided the best result, with the highest rate of conversion of methane and the lowest carbon deposition, which may be partly due to the smaller Ni 0 crystallites in this sample and also the segregated CeO 2 particles may have favored H 2 O adsorption which could lead to higher C gasification.

Catalysis Communications, 2011

ABSTRACT Catalysts derived from Co/Mg/Al hydrotalcite-type precursors modified with La and Ce wer... more ABSTRACT Catalysts derived from Co/Mg/Al hydrotalcite-type precursors modified with La and Ce were characterized by XANES and tested in ethanol steam reforming. The reaction data showed that, with a molar ratio of water:ethanol=3:1 in the feed, addition of Ce and La favored acetaldehyde production. Increasing the water content (water:ethanol=5:1) decreased the acetaldehyde formation by favoring the adsorption of water molecules on these samples, enhancing the acetaldehyde conversion.

Applied Catalysis B: Environmental, 2008

CH 4 þ H 2 O ! CO þ 3H 2 ; DH 298 K ¼ þ206 kJ mol À1 (3) CH 4 þ CO 2 ! 2CO þ 2H 2 ; DH 298 K ¼ þ2... more CH 4 þ H 2 O ! CO þ 3H 2 ; DH 298 K ¼ þ206 kJ mol À1 (3) CH 4 þ CO 2 ! 2CO þ 2H 2 ; DH 298 K ¼ þ247:5 kJ mol À1 (4) Basile et al. [5] studied Ni/Mg/Al catalysts derived from hydrotalcites, prepared by thermal treatment at 900 8C, in POM, and observed that catalysts with low nickel content needed severe reduction treatment due to the formation of the solid solution of NiO-MgO, which presented high activity for the reaction. The catalysts with higher nickel content needed mild conditions for activation, but deactivated due to carbon formation. X-ray diffraction (XRD) and temperature-programmed reduction (TPR) analysis showed the presence of the NiO and (Ni, Mg)Al 2 O 3 phases for these catalysts. Choudhary and Mamman [6] compared the behavior of the solid solutions CoO-MgO and NiO-MgO in POM at 700 8C and showed an inferior performance of Co catalysts to Ni catalysts when compared at molar ratio of CH 4 :O 2 = 2:1, however when

Biomass and Bioenergy, 2014

Ni catalysts supported on calcined MgeAl hydrotalcite, Mg(Al)O, were prepared and the effect of t... more Ni catalysts supported on calcined MgeAl hydrotalcite, Mg(Al)O, were prepared and the effect of the addition of La and/or Rh was tested in the performance of the catalysts in the dry reforming of methane with excess of methane in the feed, simulating a model sulfur-free biogas. The effect of adding synthetic air was assessed. The catalysts were characterized by surface area (BET), XRD, TPR and XPD. The results showed the reconstruction of the hydrotalcite structure during the Ni(NO 3) impregnation, with the segregation of the lanthanum. In the catalyst without Rh and La, Ni showed a strong interaction with the support Mg(Al)O, showing high reduction temperatures in TPR test. The addition of Rh and La increased the amount of reducible Ni species and facilitated the reduction of the species interacting strongly with the support which resulted in high rates of carbon deposition. The NiMgAl catalyst presented the strong Ni-support interactions and the best performance with low carbon deposition at both conditions of reaction. The NiMgAl catalyst did not present deactivation during 24 h of stability testing in the oxidative reforming of a model biogas.

Catalysis Science & Technology, 2021

The oxidative coupling of methane reaction to produce C2 compounds was studied using La2(Ce1−xMgx... more The oxidative coupling of methane reaction to produce C2 compounds was studied using La2(Ce1−xMgx)2O7−δ catalysts with disordered defective cubic fluorite structures, varying the Mg content (0.0 ≤ x ≤ 1.0), CH4/O2 ratio, temperature, and WHSV.

Catalysis Letters, 2022

Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the ... more Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the role of gadolinium on ethanol conversion, H2 selectivity, and carbon formation on ethanol steam reforming reaction. For this, catalysts containing 5 wt% of Ni impregnated on supports of ceria modified with different amounts of Gd (1, 5, and 10 wt%) were used. Ex-situ studies of XRPD suggest an increase of the lattice parameters, indicating a solid solution formation between Gd and Ce. Results of TPR showed an increase in metal-support interactions as the content of Gd increased. In situ XRPD studies indicated the formation of a GdNiO ternary phase for the catalysts containing Gd, which is in agreement with the results obtained by XANES. The catalysts were tested at three temperatures: 400 °C, 500 °C, and 600 °C. The conversion and productivity showed dependence with the Gd content and also with the temperature of the reaction. After the catalytic tests, catalysts containing Gd presented filamentous carbon possible due to a change in the reaction pathway. The highest ethanol conversion and H2 productivity were obtained at 600 °C for all catalysts and the best catalyst at this temperature was 5Ni_5GdCeO2. The promising performance of this catalyst may be associate with the lowest formation of GdNiO ternary phase, among the catalysts containing Gd, which means more Ni0 active species available to convert ethanol.

Functional Properties of Advanced Engineering Materials and Biomolecules, 2021

The development of society is dependent on commodities such as fuels and chemical feedstock. Most... more The development of society is dependent on commodities such as fuels and chemical feedstock. Most of these commodities are obtained from oil as raw material. Although the need to find a friendly solution to couple an economically viable energy model with a greener solution, it is known that technologies applying renewable sources are in an early stage of development. The conversion of methane into clean fuels or chemical feedstock with high commercial value, such as hydrogen, ethylene, or methanol is interesting from the energetic and economic point-of-view. Among the methods of methane conversion, the industrially used is the steam reforming (MSR), in which methane reacts with water to produce syngas, a mixture of CO and H 2. Nevertheless, this reaction is highly endothermic and responsible for a large volume of CO 2 emitted by the reactor burners that provide energy to the reactors. An interesting alternative process for methane conversion is the dry reforming of methane (DRM), which consists of the reaction of methane with CO 2 , also yielding syngas. The advantage of this reaction is the utilization of two harmful gases to the atmosphere. The disadvantage of this reaction is due to the catalyst deactivation by carbon deposition. In heterogeneous catalysis, there is a strong relationship between catalytic performance and surface and textural properties, that are outlined by the number and distribution of available active sites. In this way, different synthetic routes may be used to design these properties and obtain products of commercial interest, such as ethylene. The commercial production of ethylene occurs by the recuperation of refinery gases, thermal cracking of light hydrocarbons, mainly ethane and propane, or a combination of both processes. An alternative process of ethylene production may be from natural gas and or biogas. This process can be performed by the syngas

Journal of Chemical Engineering, 2015

Molecular Catalysis, 2020

The metal-containing vanadate nanotubes namely MeVO-NT (Me = Ni, Co or Pt) were in situ transform... more The metal-containing vanadate nanotubes namely MeVO-NT (Me = Ni, Co or Pt) were in situ transformed into vanadate oxides nanostructures i.e., MeV x O y , during the methane dry reforming. All the experimental observations through Raman, HRTEM, XRD, XPS, SEM-EDS, TG-FTIR and elemental analysis, strongly suggested that the VO x (MeV 2 O 7 , V 2 O 5 and VO 2) support contained the metal species that were involved in the dry reforming of methane (DRM) reaction. The pristine VO-NT catalyst exhibited a fairly low activity in DRM due to its degradation. In the case of CoVO-NT, the Co 3 O 4 /VO 2 , Co 3 O 4 /Co 2 V 2 O 7 and Co 3 O 4 /V 2 O 5 phases were deactivated by oxidation of the Co particles, instead of being deactivated by sintering and coking, as well. In contrast to CoVO-NT, PtVO-NT having PtO x /V 2 O 5 , PtO x /VO 2 or even PtO x /V 2 O 7 phases inhibited heavy carbonaceous deposition on surface, but sintering was not avoided. The NiVO-NT was active due to the stability of the Ni°/ Ni 2 V 2 O 7 active phase in hindering heavy whisker and filamentous carbonaceous deposits on such catalyst. Using Halgren-Lipscomb algorithm in the frame of density functional theory (DFT), transition states energy for all three catalysts were obtained. It was found that PtVO-NT energy profile was lower than CoVO-NT and NiVO-NT counterparts. This suggested that the Pt sites dispersed on VO x structure was catalytic active during the methane activation in DRM whereas the CoVO-NT and CoVO-NT solids were prone to perform side reactions.

Materials Research Bulletin, 2018

Highlights 1) The oxides mixture containing NiO, ZnO, Al 2 O 3 , NiAl 2 O 4 and ZnAl 2 O 4 was de... more Highlights 1) The oxides mixture containing NiO, ZnO, Al 2 O 3 , NiAl 2 O 4 and ZnAl 2 O 4 was detected. 2) The results exhibited intermediate interactions between Ni 0 and other phases. 3) Dry reforming of methane was applied to production of synthesis gas. 4) Deposition of the carbon filamentous on the catalysts surface was observed.

Fuel Processing Technology, 2014

Nickel catalysts were prepared on single-oxide supports of Al 2 O 3 , CeO 2 , MgO and ZrO 2 by im... more Nickel catalysts were prepared on single-oxide supports of Al 2 O 3 , CeO 2 , MgO and ZrO 2 by impregnation of the oxide with a solution of Ni(NO 3) 2 in methanol. The catalysts were characterized by N 2 physisorption (BET method), TPR, XRD, SEM and Raman spectroscopy and tested in dry reforming of ethanol (DRE). It was observed that the interaction with the support and Ni reducibility depended on the support used. According to TPR results, NiO species supported on CeO 2 and Al 2 O 3 were the easiest to reduce. Possibly, this behavior combined to redox properties of CeO 2 inhibited side undesirable reactions and contributed to the higher selectivity for H 2 on the NiCe catalyst. The catalytic test at 750°C on NiCe showed better H 2 selectivity than the test at 700°C, suggesting that the higher temperature enhanced CO 2 conversion and hindered carbon deposition in dry reforming of ethanol reactions.

RSC Adv., 2016

Pillared interlayer clay (PILC) is a low cost material, which is characterized by a large specifi... more Pillared interlayer clay (PILC) is a low cost material, which is characterized by a large specific surface area, high pore volume and surface acidity that make it effective in catalytic reactions.

Chemical Engineering Journal, 2016

h i g h l i g h t s Decoration of Co or Ni into titanate nanotubes and partial incorporation of P... more h i g h l i g h t s Decoration of Co or Ni into titanate nanotubes and partial incorporation of Pt. Transformation of titanate nanotubes during dry reforming of methane. Catalytic activity affected by the nature of the active sites. Surface Ni°sites on NiTiO 3 exhibited high CH 4 and CO 2 conversions.

Fuel Processing Technology, 2014

Abstract Ni/Al 2 O 3 catalysts promoted by adding La 2 O 3 , La 2 O 3 –CeO 2 and La 2 O 3 –ZrO 2 ... more Abstract Ni/Al 2 O 3 catalysts promoted by adding La 2 O 3 , La 2 O 3 –CeO 2 and La 2 O 3 –ZrO 2 were investigated on oxidative and steam reforming aiming the hydrogen production. The samples were characterized by surface area estimation (BET), XRD, TPR, TPD-H 2 and XANES. Analysis of TEM and TPO was performed as complementary characterization for catalysts after reaction. The oxidative steam reforming of methane at temperatures above 500 °C reveals that all the promoted catalysts presented better activities than the unpromoted. Below 500 °C, the catalysts presented deactivation due to metallic nickel species oxidation and the TEM analysis of Ni/Al and Ni/La–Al catalysts revealed that the lanthanum addition led to a decrease in the Ni species particle size and also to a better active phase dispersion. The results suggest that below 500 °C the activity may be related to differences in the metallic area values, although the Ni/La 2 O 3 –Al 2 O 3 catalysts have shown a different behavior.

International Journal of Hydrogen Energy, 2013

Ni/Al 2 O 3 catalysts containing 5 wt% of Ni and modified by addition of CaO (0e5 wt%) were teste... more Ni/Al 2 O 3 catalysts containing 5 wt% of Ni and modified by addition of CaO (0e5 wt%) were tested in ethanol steam reforming reaction in order to reduce the dehydration ethanol reaction, which produces ethylene that may polymerize and produce coke. The catalysts were prepared by impregnation (I) and co-precipitation (C) methods. All catalysts were investigated for ethanol steam reforming and the catalytic performance was compared in terms of additive addition. The catalysts 5Nie5Ca/Al (I) and 5Nie5Ca/Al (C) were less selective to ethylene production and therefore were characterized by the following techniques: energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray absorption near edge structure (XANES), specific surface area by the BET method, scanning electron microcopy (SEM) and isopropanol decomposition reaction. By comparing the catalysts, the 5Nie5Ca/Al (I) catalyst presented the lowest acidity and carbon deposition, and also presented no deactivation in 24 h of catalytic test.

Fuel, 2011

Cobalt catalysts were prepared on supports of SiO 2 and c-Al 2 O 3 by the impregnation method, us... more Cobalt catalysts were prepared on supports of SiO 2 and c-Al 2 O 3 by the impregnation method, using a solution of Co precursor in methanol. The samples were characterized by XRD, TPR, and Raman spectroscopy and tested in ethanol steam reforming. According to the XRD results, impregnation with the methanolic solution led to smaller metal crystallites than with aqueous solution, on the SiO 2 support. On c-Al 2 O 3 , all the samples exhibited small crystallites, with either solvent, due to a higher Co-support interaction that inhibits the reduction of Co species. The TPR results were consistent with XRD results and the samples supported on c-Al 2 O 3 showed a lower degree of reduction. In the steam reforming of ethanol, catalysts supported on SiO 2 and prepared with the methanolic solution showed the best H 2 , CO 2 and CO selectivity. Those supported on c-Al 2 O 3 showed lower H 2 selectivity.

Fuel Processing Technology, 2012

In this study, catalysts containing 5 wt.% Ni deposited on a support composed of a CeO 2-ZrO 2 so... more In this study, catalysts containing 5 wt.% Ni deposited on a support composed of a CeO 2-ZrO 2 solid solution deposited on alumina were tested in the steam reforming of methane. The supports, with various ratios of Ce to Zr, were prepared by co-precipitation of the oxide precursors, followed by calcination in synthetic air. The catalysts were then prepared by Ni impregnation of the supports. The prepared solids were characterized by temperature-programmed reduction with H 2 (TPR-H 2), in situ X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES) spectroscopy. The XRD analysis confirmed the formation of a solid solution between ZrO 2 and CeO 2. In the catalytic tests, it was found that catalysts with higher Ce content did not exhibit deactivation during 6 h of reaction. The catalyst with highest Ce content, Ni(0.8 Ce 0.2 Zr)Al, provided the best result, with the highest rate of conversion of methane and the lowest carbon deposition, which may be partly due to the smaller Ni 0 crystallites in this sample and also the segregated CeO 2 particles may have favored H 2 O adsorption which could lead to higher C gasification.

Catalysis Communications, 2011

ABSTRACT Catalysts derived from Co/Mg/Al hydrotalcite-type precursors modified with La and Ce wer... more ABSTRACT Catalysts derived from Co/Mg/Al hydrotalcite-type precursors modified with La and Ce were characterized by XANES and tested in ethanol steam reforming. The reaction data showed that, with a molar ratio of water:ethanol=3:1 in the feed, addition of Ce and La favored acetaldehyde production. Increasing the water content (water:ethanol=5:1) decreased the acetaldehyde formation by favoring the adsorption of water molecules on these samples, enhancing the acetaldehyde conversion.

Applied Catalysis B: Environmental, 2008

CH 4 þ H 2 O ! CO þ 3H 2 ; DH 298 K ¼ þ206 kJ mol À1 (3) CH 4 þ CO 2 ! 2CO þ 2H 2 ; DH 298 K ¼ þ2... more CH 4 þ H 2 O ! CO þ 3H 2 ; DH 298 K ¼ þ206 kJ mol À1 (3) CH 4 þ CO 2 ! 2CO þ 2H 2 ; DH 298 K ¼ þ247:5 kJ mol À1 (4) Basile et al. [5] studied Ni/Mg/Al catalysts derived from hydrotalcites, prepared by thermal treatment at 900 8C, in POM, and observed that catalysts with low nickel content needed severe reduction treatment due to the formation of the solid solution of NiO-MgO, which presented high activity for the reaction. The catalysts with higher nickel content needed mild conditions for activation, but deactivated due to carbon formation. X-ray diffraction (XRD) and temperature-programmed reduction (TPR) analysis showed the presence of the NiO and (Ni, Mg)Al 2 O 3 phases for these catalysts. Choudhary and Mamman [6] compared the behavior of the solid solutions CoO-MgO and NiO-MgO in POM at 700 8C and showed an inferior performance of Co catalysts to Ni catalysts when compared at molar ratio of CH 4 :O 2 = 2:1, however when

Biomass and Bioenergy, 2014

Ni catalysts supported on calcined MgeAl hydrotalcite, Mg(Al)O, were prepared and the effect of t... more Ni catalysts supported on calcined MgeAl hydrotalcite, Mg(Al)O, were prepared and the effect of the addition of La and/or Rh was tested in the performance of the catalysts in the dry reforming of methane with excess of methane in the feed, simulating a model sulfur-free biogas. The effect of adding synthetic air was assessed. The catalysts were characterized by surface area (BET), XRD, TPR and XPD. The results showed the reconstruction of the hydrotalcite structure during the Ni(NO 3) impregnation, with the segregation of the lanthanum. In the catalyst without Rh and La, Ni showed a strong interaction with the support Mg(Al)O, showing high reduction temperatures in TPR test. The addition of Rh and La increased the amount of reducible Ni species and facilitated the reduction of the species interacting strongly with the support which resulted in high rates of carbon deposition. The NiMgAl catalyst presented the strong Ni-support interactions and the best performance with low carbon deposition at both conditions of reaction. The NiMgAl catalyst did not present deactivation during 24 h of stability testing in the oxidative reforming of a model biogas.