A general method to prepare a catalytic coating on the surface of stainless steel microreactors h... more A general method to prepare a catalytic coating on the surface of stainless steel microreactors has been developed. The catalytic support consists of a layer of randomly oriented, highly accessible carbon nanofibers (CNFs), directly grown on the surface of the channels by chemical vapor deposition (CVD) of ethanol. These CNFs are functionalized to acquire a positive charge before a solution containing metallic nanoparticles (Pt) is flown through the channels. The nanoparticles adhere to the surface of the CNFs thanks to electrostatic interactions. This process is carried out in-situ and the method can be easily adapted to larger scale production. These catalyst-coated microchannel reactors have been tested in the selective oxidation (SELOX) of CO in the presence of H 2. The results were compared to those obtained in a conventional fixed bed reactor packed with Pt/CNTs. The microreactor clearly outperformed the fixed bed reactor at the same space velocity (WSHV = 2220 l/h g Pt),), achieving total CO conversion at temperatures 50 ºC lower.
h i g h l i g h t s " Y-Co catalyst is active and stable in carbon tetrachloride oxidation. " The... more h i g h l i g h t s " Y-Co catalyst is active and stable in carbon tetrachloride oxidation. " The presence of water in the feed is necessary to avoid the catalyst deactivation. " Kinetics results are consistent with a mechanism double site LHHW. " O 2 and CCl 4 are adsorbed on different type of sites.
The 21st century arrived with global growth of energy demand caused by population and standard of... more The 21st century arrived with global growth of energy demand caused by population and standard of living increases. In this context, a suitable alternative to produce COx-free H2 is the catalytic decomposition of methane (CDM), which also allows for obtaining high-value-added carbonaceous nanomaterials (CNMs), such as carbon nanotubes (CNTs). This work presents the results obtained in the co-production of COx-free hydrogen and CNTs by CDM using Ni–Cu and Co–Cu catalysts supported on carbon derived from Argan (Argania spinosa) shell (ArDC). The results show that the operation at 900 °C and a feed-ratio CH4:H2 = 2 with the Ni–Cu/ArDC catalyst is the most active, producing 3.7 gC/gmetal after 2 h of reaction (equivalent to average hydrogen productivity of 0.61 g H2/gmetal∙h). The lower productivity of the Co–Cu/ArDC catalyst (1.4 gC/gmetal) could be caused by the higher proportion of small metallic NPs (<5 nm) that remain confined inside the micropores of the carbonaceous support, h...
This work addresses the preparation and application of the synthesis of graphene in Ni-Cu catalys... more This work addresses the preparation and application of the synthesis of graphene in Ni-Cu catalysts supported on carbonaceous materials. The catalysts have been prepared by a biomorphic mineralization technique which involves the thermal decomposition, under reductive atmosphere, of commercial cellulose previously impregnated with the metallic precursors. The characterization results indicate that the preparation method leads to the formation of carbonaceous supports with a moderate microporosity (ca. 33% pore volume) and adequate surface area (343 m 2 /g), maintaining the original external texture. The catalytic performance of these materials was previously tested in liquid phase reactions [11]. In order to extend the use of these catalysts, in this work we present a study corresponding to a gas phase reaction: the synthesis of graphenic nanomaterials by catalytic decomposition of methane (CDM). The influence of the reaction temperature and of the feed composition (i.e. %CH 4 and %H 2) has been studied. The graphenic nanomaterials obtained after reaction were characterized by nitrogen adsorption-desorption isotherms, Raman spectroscopy and transmission electron microscopy (TEM). The results indicate that the carbonaceous nanomaterial with the highest quality is obtained operating at 950 °C and feeding 28.6% of CH 4 and 14.3% of H 2. The evolution of the carbon mass during the reaction time was analysed using a phenomenological kinetic model that takes into account the main stages involved during the formation of carbonaceous nanomaterials (NCMs). The results obtained from the kinetic model along with the characterization results enable the influence of the operating variables on each stage of the carbonaceous nanomaterial formation to be discerned.
... N. Latorre 4 JI Villacampa 4 T. Ubieto 4 E. Romeo 4 C. Royo 4 A. Monzón (&) Institute of ... more ... N. Latorre 4 JI Villacampa 4 T. Ubieto 4 E. Romeo 4 C. Royo 4 A. Monzón (&) Institute of Nanoscience of Aragon (INA), Department of Chemical and Environmental Engineering, University of Zaragoza, Zaragoza 50009, Spain e-mail: amonzon@unizar ... Carbon content (g/g.cat) ...
A Phenomenological Kinetic Model has been developed that includes all the relevant steps involved... more A Phenomenological Kinetic Model has been developed that includes all the relevant steps involved in CNT growth by CCVD,that is, carbon source decomposition, nanoparticle surface carburization, carbon diffusion, nucleation, CNT growth, and growth termination by catalyst deactivation or by the effect of steric hindrance. Here we emphasize the importance of using a proper kinetic description of all the stages, in particular the initial carburization-nucleation and the growth cessation. We have discussed the different mechanisms proposed to explain the critical step of carburization-nucleation and have used an autocatalytic kinetic model to describe it. The two parameters involved in this autocatalytic equation allow a very good fit of the initial induction period usually observed during the growth of CNTs. In addition, rigorous formulations of the main causes of CNT growth cessation (catalyst deactivation by several causes and steric hindrance) have been proposed. The developed model is a versatile tool of potentially general application. In this paper, we have applied it to fit data obtained in our lab, and also to super growth of VA-SWNT experimental data published in the literature. In all cases the values obtained for the kinetic parameters have realistic physical meaning in good agreement with the mechanism of CNT formation.
ABSTRACT We have studied the coupling of mass transport and chemical reaction rates in a biphasic... more ABSTRACT We have studied the coupling of mass transport and chemical reaction rates in a biphasic emulsion system. The emulsion is stabilized by the presence of solid nanoparticles that, in addition, act as a catalyst for the reaction. These solid nanoparticles are composed of carbon nanotubes (CNTs) attached to SiO2 nanoparticles. Both components, CNTs and silica, can be selectively impregnated by a catalytic active phase (e.g. Pd) forming the so-called nanohybrids. We have studied the application of the catalytic nanohybrids in emulsions of type (w/o), during the reaction of hydrodeoxygenation of vanillin (4-hydroxy-3-methoxy-benzaldehyde). This is a model reaction that occurs in the aqueous side of the interface of the emulsion. The main target for this work is to analyze the impact of mass transport of the main compounds between the aqueous and organic phases on the global performance of the reaction.
Ni-containing catalysts for selective acetylene hydrogenation to ethylene have been prepared by c... more Ni-containing catalysts for selective acetylene hydrogenation to ethylene have been prepared by controlled calcination of hydrotalcite-like precursors. In addition to Ni and Al, Cr and Zn were added to improve the catalytic performance. The hydrotalcite-like precursors and the calcined catalysts have been characterized by powder X-ray diffraction, FT-IR and Vis-UVrDiffuse Reflectance spectroscopies, temperature-programmed reduction, and specific surface area assessment by nitrogen adsorption at 77 K. Despite addition of Zn hinders coke formation, the activity to gaseous products decreases as the Ni content is increased. An increase in coke concentration increases activity and selectivity to ethylene, specially in those samples with not too high Ni Ž . contents. The highest selectivity to ethylene is achieved for ZnrNif 4 molar ratio .
The catalytic decomposition of methane over nickel catalysts is a potential alternative route to ... more The catalytic decomposition of methane over nickel catalysts is a potential alternative route to steam reforming or partial oxidation for the production of hydrogen from natural gas and other feedstocks. In the present paper, we report the results of characterization and catalytic behaviour of a Ni(30%)/Al 2 O 3 catalyst during the catalytic decomposition of methane. The influence of the operating and reduction temperatures and feed composition on the methane conversion, hydrogen production and coking rate has been studied. The effects of the regeneration cycles with oxygen on activity and carbon formation are also investigated. It has been shown that H 2 inhibits both the carbon filament formation and the encapsulation of metallic particles by coke. An increase in the reaction temperature increases both the deactivation rate and the growth rate of filaments. However, at high reduction temperatures, there is a decrease in the number of filaments formed due to sintering of the Ni particles. A kinetic model has been developed for the prediction of H 2 production and of carbon, taking into account both stages of carbon formation, nucleation and filament growth.
The effect of the Ni/Zn molar ratio on the activity, selectivity, and coke formation of NiO·ZnO·A... more The effect of the Ni/Zn molar ratio on the activity, selectivity, and coke formation of NiO·ZnO·Al2O3 catalysts (modified with Fe3+ or Cr3+) during acetylene hydrogenation has been studied. Coke formation is decreased significantly in the presence of ZnO, and a similar effect is also found when the catalysts are doped with Cr3+ instead of with Fe3+. An optimum Ni/Zn ratio
with benzaldehyde and concentrated aqueous hydrochloric acid forms a 5 ring benzylidene acetal-6-... more with benzaldehyde and concentrated aqueous hydrochloric acid forms a 5 ring benzylidene acetal-6-ring lactone 6 (Fig. 1).
International Journal of Chemical Reactor Engineering
This work is an advance on the development of structured catalytic reactors. Here, we present the... more This work is an advance on the development of structured catalytic reactors. Here, we present the results of the effect of the main operational variables (reaction temperature, % H2 and % C2H6) on the kinetics of carbonaceous nanomaterials (CNMs) formation by catalytic decomposition of ethane over stainless steel foams. Some of the main drawback problems that occur during the operation of chemical structured reactors are related to the preparation of long term stable coatings. The washcoating is the most used technique to deposit the catalytic layer over the substrate. The application of this procedure is quite complex in the case of geometries such as foams or cloths. In the case of the deposition of layers of carbonaceous nanomaterials, an alternative route, avoiding the washcoating, is their direct growth by catalytic decomposition of light hydrocarbons over the surface of the metallic substrate. In the case of structured steel foams, the substrate already contains the catalytic ...
In this work, we present the results of production of carbonaceous nanomaterials by decomposition... more In this work, we present the results of production of carbonaceous nanomaterials by decomposition of methane on a catalyst of Ni supported on a Biomorphic Carbon. The catalyst was prepared by thermal decomposition in a reductive atmosphere of vine shoots previously impregnated with the Ni precursor. In order to optimize the reaction productivity and selectivity, the effect of the main operational conditions (reaction temperature and feed composition) has been studied in a thermobalance. The main textural properties, BET area of 63 m 2 /g and 56% of microporosity, of the catalyst synthesized indicates that these materials are suitable for gas-phase reactions even in harsh conditions. Thus, the catalyst has proved to be active in the synthesis of carbon nanofibers and graphene related materials at elevated temperatures. The productivity, type, and quality of the carbonaceous nanomaterials obtained are deeply dependent on the operating conditions during the reaction. As an important fact, is has been obtained that the reaction temperature strongly affects the type of the nanomaterial produced. Thus, it is produced CNFs of bamboo type at temperatures until 850 • C. Above this critical temperature, it is mainly obtained nanolayers of graphitic nature. The characterization results indicate that the highest quality graphenic materials were obtained operating at 950 • C with 14.3% of CH 4 and 14.3% of H 2. The kinetic model used to analyze the experimental data is based on the more relevant stages of the mechanism of reaction.
The Chemical Engineering Journal and the Biochemical Engineering Journal, 1995
In the deactivation of commercial catalysts by coke formation, complete deactivation of the catal... more In the deactivation of commercial catalysts by coke formation, complete deactivation of the catalyst is seldom observed and frequently a certain lower activity level is maintained. In the present work, several kinetic models that predict partial catalyst deactivation have been analysed. The presence of active sites with different strengths on the catalyst surface and reversible coke formation have been considered as possible causes of the residual activity of the catalyst. In order to check these kinetic models, they have been applied to the isopropylbenzene cracking reaction over silica-alumina catalyst. From the results obtained, the model which gave the best fit to the experimental data was that of reversible coke deposition.
... E. Romeo 1 , AJ Marchi 2 , A. Borgna 2 and A. Monzón 1 , E-mail The Corresponding Author. ...... more ... E. Romeo 1 , AJ Marchi 2 , A. Borgna 2 and A. Monzón 1 , E-mail The Corresponding Author. ... Total flow rate 700 ml/min Feed composition study of H2 influence: from 30/15/55 to 75/15/10 (HJC2HJN2) study of C2H2 influence: from 45/5/50 to 45/20/35 W/F a O 2560 mg cat s/m ...
Some of the problems that occur during the operation of chemical reactors based of structured cat... more Some of the problems that occur during the operation of chemical reactors based of structured catalytic substrates, as monoliths, foams, membranes, cloths, fibres and other systems, are related to the preparation of long term stable coatings. Frequently, the deposition of the catalytic layer is carried out by washcoating, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths. In the case of the deposition of layers of carbonaceous materials (CNMs), an alternative route, avoiding the washcoating, it is their direct growth by catalytic decomposition light hydrocarbons (also called CCVD), over the surface of the metallic substrate. In this case, if the metallic substrate is of stainless steel, it already contains the catalytic active phases like Fe and Ni. In order to optimize the process of CNMs growth over structured metallic substrates, we are studying the effect of the main operational variables of the ethane decomposition reaction on stainless steel foams. In this contribution we present a study of the influence of the temperature of the activation (oxidation and reduction) stage on the type and morphology of the carbonaceous materials formed. The results obtained allow us to determine the optimal operating conditions to maximize the amount and the selectivity of the process to obtain a given type of CNM.
... 3. JC Rodriguez, E. Romeo, A. Monzdn, A. Borgna and AJ Marchi, XV Iberoamer. Symp. Catal., Co... more ... 3. JC Rodriguez, E. Romeo, A. Monzdn, A. Borgna and AJ Marchi, XV Iberoamer. Symp. Catal., Cordoba, Argentina, (1996) 909. 4. LS Lobo, DL Trimm and JL Figuereido, 5 th Int. Cong. on Catal., Palm Beach, 1972, JW Hightower (Ed.), North-Holland, Amsterdam, 2 (1973) 1125 ...
A general method to prepare a catalytic coating on the surface of stainless steel microreactors h... more A general method to prepare a catalytic coating on the surface of stainless steel microreactors has been developed. The catalytic support consists of a layer of randomly oriented, highly accessible carbon nanofibers (CNFs), directly grown on the surface of the channels by chemical vapor deposition (CVD) of ethanol. These CNFs are functionalized to acquire a positive charge before a solution containing metallic nanoparticles (Pt) is flown through the channels. The nanoparticles adhere to the surface of the CNFs thanks to electrostatic interactions. This process is carried out in-situ and the method can be easily adapted to larger scale production. These catalyst-coated microchannel reactors have been tested in the selective oxidation (SELOX) of CO in the presence of H 2. The results were compared to those obtained in a conventional fixed bed reactor packed with Pt/CNTs. The microreactor clearly outperformed the fixed bed reactor at the same space velocity (WSHV = 2220 l/h g Pt),), achieving total CO conversion at temperatures 50 ºC lower.
h i g h l i g h t s " Y-Co catalyst is active and stable in carbon tetrachloride oxidation. " The... more h i g h l i g h t s " Y-Co catalyst is active and stable in carbon tetrachloride oxidation. " The presence of water in the feed is necessary to avoid the catalyst deactivation. " Kinetics results are consistent with a mechanism double site LHHW. " O 2 and CCl 4 are adsorbed on different type of sites.
The 21st century arrived with global growth of energy demand caused by population and standard of... more The 21st century arrived with global growth of energy demand caused by population and standard of living increases. In this context, a suitable alternative to produce COx-free H2 is the catalytic decomposition of methane (CDM), which also allows for obtaining high-value-added carbonaceous nanomaterials (CNMs), such as carbon nanotubes (CNTs). This work presents the results obtained in the co-production of COx-free hydrogen and CNTs by CDM using Ni–Cu and Co–Cu catalysts supported on carbon derived from Argan (Argania spinosa) shell (ArDC). The results show that the operation at 900 °C and a feed-ratio CH4:H2 = 2 with the Ni–Cu/ArDC catalyst is the most active, producing 3.7 gC/gmetal after 2 h of reaction (equivalent to average hydrogen productivity of 0.61 g H2/gmetal∙h). The lower productivity of the Co–Cu/ArDC catalyst (1.4 gC/gmetal) could be caused by the higher proportion of small metallic NPs (<5 nm) that remain confined inside the micropores of the carbonaceous support, h...
This work addresses the preparation and application of the synthesis of graphene in Ni-Cu catalys... more This work addresses the preparation and application of the synthesis of graphene in Ni-Cu catalysts supported on carbonaceous materials. The catalysts have been prepared by a biomorphic mineralization technique which involves the thermal decomposition, under reductive atmosphere, of commercial cellulose previously impregnated with the metallic precursors. The characterization results indicate that the preparation method leads to the formation of carbonaceous supports with a moderate microporosity (ca. 33% pore volume) and adequate surface area (343 m 2 /g), maintaining the original external texture. The catalytic performance of these materials was previously tested in liquid phase reactions [11]. In order to extend the use of these catalysts, in this work we present a study corresponding to a gas phase reaction: the synthesis of graphenic nanomaterials by catalytic decomposition of methane (CDM). The influence of the reaction temperature and of the feed composition (i.e. %CH 4 and %H 2) has been studied. The graphenic nanomaterials obtained after reaction were characterized by nitrogen adsorption-desorption isotherms, Raman spectroscopy and transmission electron microscopy (TEM). The results indicate that the carbonaceous nanomaterial with the highest quality is obtained operating at 950 °C and feeding 28.6% of CH 4 and 14.3% of H 2. The evolution of the carbon mass during the reaction time was analysed using a phenomenological kinetic model that takes into account the main stages involved during the formation of carbonaceous nanomaterials (NCMs). The results obtained from the kinetic model along with the characterization results enable the influence of the operating variables on each stage of the carbonaceous nanomaterial formation to be discerned.
... N. Latorre 4 JI Villacampa 4 T. Ubieto 4 E. Romeo 4 C. Royo 4 A. Monzón (&) Institute of ... more ... N. Latorre 4 JI Villacampa 4 T. Ubieto 4 E. Romeo 4 C. Royo 4 A. Monzón (&) Institute of Nanoscience of Aragon (INA), Department of Chemical and Environmental Engineering, University of Zaragoza, Zaragoza 50009, Spain e-mail: amonzon@unizar ... Carbon content (g/g.cat) ...
A Phenomenological Kinetic Model has been developed that includes all the relevant steps involved... more A Phenomenological Kinetic Model has been developed that includes all the relevant steps involved in CNT growth by CCVD,that is, carbon source decomposition, nanoparticle surface carburization, carbon diffusion, nucleation, CNT growth, and growth termination by catalyst deactivation or by the effect of steric hindrance. Here we emphasize the importance of using a proper kinetic description of all the stages, in particular the initial carburization-nucleation and the growth cessation. We have discussed the different mechanisms proposed to explain the critical step of carburization-nucleation and have used an autocatalytic kinetic model to describe it. The two parameters involved in this autocatalytic equation allow a very good fit of the initial induction period usually observed during the growth of CNTs. In addition, rigorous formulations of the main causes of CNT growth cessation (catalyst deactivation by several causes and steric hindrance) have been proposed. The developed model is a versatile tool of potentially general application. In this paper, we have applied it to fit data obtained in our lab, and also to super growth of VA-SWNT experimental data published in the literature. In all cases the values obtained for the kinetic parameters have realistic physical meaning in good agreement with the mechanism of CNT formation.
ABSTRACT We have studied the coupling of mass transport and chemical reaction rates in a biphasic... more ABSTRACT We have studied the coupling of mass transport and chemical reaction rates in a biphasic emulsion system. The emulsion is stabilized by the presence of solid nanoparticles that, in addition, act as a catalyst for the reaction. These solid nanoparticles are composed of carbon nanotubes (CNTs) attached to SiO2 nanoparticles. Both components, CNTs and silica, can be selectively impregnated by a catalytic active phase (e.g. Pd) forming the so-called nanohybrids. We have studied the application of the catalytic nanohybrids in emulsions of type (w/o), during the reaction of hydrodeoxygenation of vanillin (4-hydroxy-3-methoxy-benzaldehyde). This is a model reaction that occurs in the aqueous side of the interface of the emulsion. The main target for this work is to analyze the impact of mass transport of the main compounds between the aqueous and organic phases on the global performance of the reaction.
Ni-containing catalysts for selective acetylene hydrogenation to ethylene have been prepared by c... more Ni-containing catalysts for selective acetylene hydrogenation to ethylene have been prepared by controlled calcination of hydrotalcite-like precursors. In addition to Ni and Al, Cr and Zn were added to improve the catalytic performance. The hydrotalcite-like precursors and the calcined catalysts have been characterized by powder X-ray diffraction, FT-IR and Vis-UVrDiffuse Reflectance spectroscopies, temperature-programmed reduction, and specific surface area assessment by nitrogen adsorption at 77 K. Despite addition of Zn hinders coke formation, the activity to gaseous products decreases as the Ni content is increased. An increase in coke concentration increases activity and selectivity to ethylene, specially in those samples with not too high Ni Ž . contents. The highest selectivity to ethylene is achieved for ZnrNif 4 molar ratio .
The catalytic decomposition of methane over nickel catalysts is a potential alternative route to ... more The catalytic decomposition of methane over nickel catalysts is a potential alternative route to steam reforming or partial oxidation for the production of hydrogen from natural gas and other feedstocks. In the present paper, we report the results of characterization and catalytic behaviour of a Ni(30%)/Al 2 O 3 catalyst during the catalytic decomposition of methane. The influence of the operating and reduction temperatures and feed composition on the methane conversion, hydrogen production and coking rate has been studied. The effects of the regeneration cycles with oxygen on activity and carbon formation are also investigated. It has been shown that H 2 inhibits both the carbon filament formation and the encapsulation of metallic particles by coke. An increase in the reaction temperature increases both the deactivation rate and the growth rate of filaments. However, at high reduction temperatures, there is a decrease in the number of filaments formed due to sintering of the Ni particles. A kinetic model has been developed for the prediction of H 2 production and of carbon, taking into account both stages of carbon formation, nucleation and filament growth.
The effect of the Ni/Zn molar ratio on the activity, selectivity, and coke formation of NiO·ZnO·A... more The effect of the Ni/Zn molar ratio on the activity, selectivity, and coke formation of NiO·ZnO·Al2O3 catalysts (modified with Fe3+ or Cr3+) during acetylene hydrogenation has been studied. Coke formation is decreased significantly in the presence of ZnO, and a similar effect is also found when the catalysts are doped with Cr3+ instead of with Fe3+. An optimum Ni/Zn ratio
with benzaldehyde and concentrated aqueous hydrochloric acid forms a 5 ring benzylidene acetal-6-... more with benzaldehyde and concentrated aqueous hydrochloric acid forms a 5 ring benzylidene acetal-6-ring lactone 6 (Fig. 1).
International Journal of Chemical Reactor Engineering
This work is an advance on the development of structured catalytic reactors. Here, we present the... more This work is an advance on the development of structured catalytic reactors. Here, we present the results of the effect of the main operational variables (reaction temperature, % H2 and % C2H6) on the kinetics of carbonaceous nanomaterials (CNMs) formation by catalytic decomposition of ethane over stainless steel foams. Some of the main drawback problems that occur during the operation of chemical structured reactors are related to the preparation of long term stable coatings. The washcoating is the most used technique to deposit the catalytic layer over the substrate. The application of this procedure is quite complex in the case of geometries such as foams or cloths. In the case of the deposition of layers of carbonaceous nanomaterials, an alternative route, avoiding the washcoating, is their direct growth by catalytic decomposition of light hydrocarbons over the surface of the metallic substrate. In the case of structured steel foams, the substrate already contains the catalytic ...
In this work, we present the results of production of carbonaceous nanomaterials by decomposition... more In this work, we present the results of production of carbonaceous nanomaterials by decomposition of methane on a catalyst of Ni supported on a Biomorphic Carbon. The catalyst was prepared by thermal decomposition in a reductive atmosphere of vine shoots previously impregnated with the Ni precursor. In order to optimize the reaction productivity and selectivity, the effect of the main operational conditions (reaction temperature and feed composition) has been studied in a thermobalance. The main textural properties, BET area of 63 m 2 /g and 56% of microporosity, of the catalyst synthesized indicates that these materials are suitable for gas-phase reactions even in harsh conditions. Thus, the catalyst has proved to be active in the synthesis of carbon nanofibers and graphene related materials at elevated temperatures. The productivity, type, and quality of the carbonaceous nanomaterials obtained are deeply dependent on the operating conditions during the reaction. As an important fact, is has been obtained that the reaction temperature strongly affects the type of the nanomaterial produced. Thus, it is produced CNFs of bamboo type at temperatures until 850 • C. Above this critical temperature, it is mainly obtained nanolayers of graphitic nature. The characterization results indicate that the highest quality graphenic materials were obtained operating at 950 • C with 14.3% of CH 4 and 14.3% of H 2. The kinetic model used to analyze the experimental data is based on the more relevant stages of the mechanism of reaction.
The Chemical Engineering Journal and the Biochemical Engineering Journal, 1995
In the deactivation of commercial catalysts by coke formation, complete deactivation of the catal... more In the deactivation of commercial catalysts by coke formation, complete deactivation of the catalyst is seldom observed and frequently a certain lower activity level is maintained. In the present work, several kinetic models that predict partial catalyst deactivation have been analysed. The presence of active sites with different strengths on the catalyst surface and reversible coke formation have been considered as possible causes of the residual activity of the catalyst. In order to check these kinetic models, they have been applied to the isopropylbenzene cracking reaction over silica-alumina catalyst. From the results obtained, the model which gave the best fit to the experimental data was that of reversible coke deposition.
... E. Romeo 1 , AJ Marchi 2 , A. Borgna 2 and A. Monzón 1 , E-mail The Corresponding Author. ...... more ... E. Romeo 1 , AJ Marchi 2 , A. Borgna 2 and A. Monzón 1 , E-mail The Corresponding Author. ... Total flow rate 700 ml/min Feed composition study of H2 influence: from 30/15/55 to 75/15/10 (HJC2HJN2) study of C2H2 influence: from 45/5/50 to 45/20/35 W/F a O 2560 mg cat s/m ...
Some of the problems that occur during the operation of chemical reactors based of structured cat... more Some of the problems that occur during the operation of chemical reactors based of structured catalytic substrates, as monoliths, foams, membranes, cloths, fibres and other systems, are related to the preparation of long term stable coatings. Frequently, the deposition of the catalytic layer is carried out by washcoating, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths. In the case of the deposition of layers of carbonaceous materials (CNMs), an alternative route, avoiding the washcoating, it is their direct growth by catalytic decomposition light hydrocarbons (also called CCVD), over the surface of the metallic substrate. In this case, if the metallic substrate is of stainless steel, it already contains the catalytic active phases like Fe and Ni. In order to optimize the process of CNMs growth over structured metallic substrates, we are studying the effect of the main operational variables of the ethane decomposition reaction on stainless steel foams. In this contribution we present a study of the influence of the temperature of the activation (oxidation and reduction) stage on the type and morphology of the carbonaceous materials formed. The results obtained allow us to determine the optimal operating conditions to maximize the amount and the selectivity of the process to obtain a given type of CNM.
... 3. JC Rodriguez, E. Romeo, A. Monzdn, A. Borgna and AJ Marchi, XV Iberoamer. Symp. Catal., Co... more ... 3. JC Rodriguez, E. Romeo, A. Monzdn, A. Borgna and AJ Marchi, XV Iberoamer. Symp. Catal., Cordoba, Argentina, (1996) 909. 4. LS Lobo, DL Trimm and JL Figuereido, 5 th Int. Cong. on Catal., Palm Beach, 1972, JW Hightower (Ed.), North-Holland, Amsterdam, 2 (1973) 1125 ...
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