Characterization of polycrystalline TiO 2 bare or porphyrin impregnated powders, used as photocat... more Characterization of polycrystalline TiO 2 bare or porphyrin impregnated powders, used as photocatalysts for the degradation of 4-nitrophenol (4-NP) in aqueous suspension, was performed by time-resolved microwave conductivity (TRMC) measurements and electronic paramagnetic resonance (EPR) and X-ray photoelectron (XPS) spectroscopies. The presence of porphyrin sensitizers, as the metal-free or Cu [5,10,15,20-tetra (4tert-butylphenyl)] porphyrin, impregnated onto the TiO 2 surface improved the photocatalytic activity of the bare TiO 2 . TRMC measurements indicate that the number and lifetime of the photoinduced excess charge carriers increase in the presence of the macrocycles, and EPR and XPS spectroscopies support the mechanistic hypotheses based on the photoreactivity experiments.
A Pt/TiO 2 catalyst has been subjected to reduction in hydrogen at 473, 573 and 773 K and the var... more A Pt/TiO 2 catalyst has been subjected to reduction in hydrogen at 473, 573 and 773 K and the various degrees of metal-support interaction (SMSI) confirmed by means of CO and H 2 chemisorption, FTIR of CO and the hydrogenation of crotonaldehyde. Coadsorption of CO and crotonaldehyde were performed to identify the preferred adsorption site and mode of adsorption of the unsaturated aldehyde. Results which appear to suggest shifts to lower frequencies of bands due to adsorbed carbonyls are not due to electronic effects induced by coadsorption, but rather indicate displacement of CO from the weaker bonding sites which eliminate dipole coupling effects between different carbonyl clusters, and consequently removes intensity transfer phenomena leading to enhancement in intensity at lower frequencies.
The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy s... more The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.
Thermochemical heat storage (TCS) based on redox cycles of metal oxides is a promising concept th... more Thermochemical heat storage (TCS) based on redox cycles of metal oxides is a promising concept that allows enhancing the energy generation dispatchability in concentrated solar power plants (CSP). Nevertheless, several factors that affect to the long term durability of these materials must be evaluated as to guarantee an efficient operation. Among others, the redox reversibility, reaction kinetics and material degradation are crucial factors, as they directly influence in the materials cycle stability. It has been found that sintering processes associated with the high operation temperature may produce a decrease on the oxidation kinetics. However, this study proves that, in the case of manganese oxides, such decrease can be attenuated by addition of small amount of iron, improving the redox performance of these materials.
Redox cycles of manganese oxides (Mn2 O3 /Mn3 O4 ) are a promising alternative for thermochemical... more Redox cycles of manganese oxides (Mn2 O3 /Mn3 O4 ) are a promising alternative for thermochemical heat storage systems coupled to concentrated solar power plants as manganese oxides are abundant and inexpensive materials. Although their cyclability for such a purpose has been proved, sintering processes, related to the high-temperature conditions at which charge-discharge cycles are performed, generally cause a cycle-to-cycle decrease in the oxidation rate of Mn3 O4 . To guarantee proper operation, both reactions should present stable reaction rates. In this study, it has been demonstrated that the incorporation of Fe, which is also an abundant material, into the manganese oxides improves the redox performance of this system by increasing the heat storage density, narrowing the redox thermal hysteresis, and, above all, stabilizing and enhancing the oxidation rate over long-term operation, which counteracts the negative effects caused by sintering, although its presence is not avoided.
Thermochemical energy storage (TCS) based on reduction-oxidation cycles of multivalent metal oxid... more Thermochemical energy storage (TCS) based on reduction-oxidation cycles of multivalent metal oxides is of great interest for concentrating solar facilities, as it can allow enhancing the global plant efficiency and improving the energy generation dispatchability. However, to guarantee the feasibility of the process, selected materials should present long term durability, which requires the evaluation of the redox couple cyclability. In this work we have demonstrated, for the first time, the suitability of the Mn 2 O 3 /Mn 3 O 4 pair for this application during 30 cycles, performed in thermobalance. Nevertheless, an appropriate design of such materials is crucial since it has been found that initial particle size influences the redox behaviour of these oxides. Results showed a 2-fold influence of particle size of the as-prepared materials on the redox reversibility. Firstly, this parameter affects to the thermodynamics and kinetics of the redox reactions. Namely a decrease of the particle size shifted the oxidation temperature to lower values and produced slower reduction and oxidation reactions. Secondly, depending on the particles size, samples followed different sintering mechanisms. This fact influenced dramatically the behaviour of the materials with lower particle size, which suffered from a higher degree of densification that eventually caused a total loss of cyclability. † Electronic supplementary information (ESI) available: XRD patterns; high resolution TEM micrographs; SEM micrographs, rst cooling step interval; DSC curves for M 1 sample. See
The reactivity of CeO2, pure or supported on alumina, in NO adsorption and catalytic activity for... more The reactivity of CeO2, pure or supported on alumina, in NO adsorption and catalytic activity for the CO+NO+O2 reaction (in the absence of metal), has been tested using IR, ESR and temperature-programmed desorption/reactivity techniques. Significant differences are found in alumina-supported ceria in comparison with pure CeO2; its lower activity can be connected to the difficulty of generating on well-dispersed CeO2/Al2O3
Research on photocatalytic materials has been a field in continuous expansion in the recent decad... more Research on photocatalytic materials has been a field in continuous expansion in the recent decades, as it is evidenced by the large number of articles published every year. So far, more than 190 different semiconductors have been assayed as suitable photocatalysts. To this figure, it is necessary to add the combinations with other functional materials or between different semiconductors, as well as their morphological modifications. Summing up the outcome of these different preparation strategies eventually leads to the enormous number of photocatalytic systems that have been reported in the scientific literature. Dealing with such an amount of information requires updated and educated guidance to select the most significant realizations, and it also calls for critical assessments on how the expectations are being fulfilled. This perspective article intends to assess the state of the art of photocatalysis with regard to materials and systems, considering the well-established results, but also the emerging aspects, and the envisaged new directions of this technology in the near future. In the first part, the most relevant achievements in this area, some of them already in the market while others still in development, will be reviewed according to the current understanding. The second part of the article is devoted to the most innovative and promising photocatalysts and related systems described in the open literature.
ABSTRACT Research for the development of more efficient photocatalysts has experienced an almost ... more ABSTRACT Research for the development of more efficient photocatalysts has experienced an almost exponential growth since its popularization in early 1970’s. Despite the advantages of the widely used TiO2, the yield of the conversion of sun power into chemical energy that can be achieved with this material is limited prompting the research and development of a number of structural, morphological and chemical modifications of TiO2 , as well as a number of novel photocatalysts with very different composition. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications provides a systematic account of the current understanding of the relationships between the physicochemical properties of the catalysts and photoactivity. The already long list of photocatalysts phases and their modifications is increasing day by day. By approaching this field from a material sciences angle, an integrated view allows readers to consider the diversity of photocatalysts globally and in connection with other technologies. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications provides a valuable road-map, outlining the common principles lying behind the diversity of materials, but also delimiting the imprecise border between the contrasted results and the most speculative studies. This broad approach makes it ideal for specialist but also for engineers, researchers and students in related fields http://www.springer.com/energy/renewable+and+green+energy/book/978-1-4471-5060-2
ABSTRACT A series of high-performance catalysts based on nickel phosphide particles supported on ... more ABSTRACT A series of high-performance catalysts based on nickel phosphide particles supported on SBA-15 have been synthesized by temperature-programed reduction of a nickel phosphate, previously impregnated in the mesostructured silica support. In these samples the loading of the active phase varied between 10% and 20% in a Ni basis, while nominal Ni/P ratios ranged from 0.5 to 3. The formation of different active phases, Ni2P, Ni12P5 or Ni3P, depending on the P/Ni proportion was verified by X-ray diffraction (XRD). The study of these catalysts by transmission electron microscopy (TEM) and Energy-Dispersive X-ray spectroscopy (EDX) revealed that the majority of the phosphide nanoparticles present a relatively uniform diameter evenly distributed within the SBA-15 channels. All the nickel phosphide catalysts, as well as a reference Ni/SBA-15 catalyst, were tested for the hydrodeoxygenation (HDO) of methyl oleate (C17H33-COO-CH3) in a high pressure continuous flow reactor. This compound was used as a convenient surrogate of triglyceride molecules present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes at 30 bars and temperature in the 250-340 °C range. In all cases lower contact time and reaction temperature decrease the conversion but favor the formation of C18 alkanes, which is the preferred product in terms of carbon atom economy. In addition, this study reveals that activity and selectivity are affected remarkably by the Ni/P ratio. Maximum conversion is achieved for the catalysts prepared with an initial Ni/P ratio of 1, while selectivity to C18 is larger for the catalyst with an initial Ni/P ratio of 2. These catalysts contain predominantly the Ni2P phase, which seem to be the most active for this process, although the presence of Ni12P5 in the case of the catalysts with Ni/P = 2 appears to be also positive. On the basis of the product distribution it can be concluded that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the nickel phosphide catalysts, whereas decarboxylation and cracking are the prevailing processes over the Ni/SBA-15 catalyst. Owing to these high yields of long-chain paraffins, SBA-15-supported nickel phosphide catalysts can be considered as a very promising catalyst for the transformation of vegetable oils into green diesel.
ABSTRACT It is believed that hydrogen will play a relevant role as an energy vector in the near f... more ABSTRACT It is believed that hydrogen will play a relevant role as an energy vector in the near future, but in order to fulfil these expectations the development of economically feasible routes with limited CO2 emissions is required. In this respect, catalysis is crucial in most of the possible processes for hydrogen generation and, accordingly, improvement in the catalyst properties should have a significant impact on the efficiency of the production. In particular, ordered mesoporous materials of different chemical composition (oxides and non-oxides) possess a high potential for improving a variety of catalytic routes for the production of low-carbon hydrogen. The activity of this type of catalyst is frequently enhanced due to a combination of high surface area, low diffusion restrictions, and high dispersion of the supported active phases. In this work, we review the latest advances in the use of these mesostructured catalysts in the most relevant routes for hydrogen generation with reduced greenhouse emissions: steam reforming of biomass derived feedstocks (biogas, ethanol, and glycerol), methane and ammonia decomposition and photocatalytic reduction using sacrificial electron donors.
ABSTRACT Hydrodeoxygenation (HDO) is considered one of the most promising routes to convert the p... more ABSTRACT Hydrodeoxygenation (HDO) is considered one of the most promising routes to convert the pyrolysis bio-oils produced from lignocellulose into biofuels very similar to those derived from petroleum. This work reports results obtained in the catalytic HDO of anisole over non-conventional hydrotreating catalysts based on metallic Ni and Co supported on micro-mesoporous carriers of different acidity. Anisole has been chosen as representative of those compounds, containing a methoxy-phenyl group, which are abundant in lignocellulose pyrolysis bio-oils. The effect of both metal phase and support properties on their performance as HDO catalysts has been studied. With this aim, three supports with different textural and acidic properties have been employed: hierarchical ZSM-5, mesostructured pure silica SBA-15 and mesostructured Al-SBA-15. The reactions have been carried out in a stainless steel high pressure batch reactor at 220 °C and with 50 bar of pure hydrogen.
Characterization of polycrystalline TiO 2 bare or porphyrin impregnated powders, used as photocat... more Characterization of polycrystalline TiO 2 bare or porphyrin impregnated powders, used as photocatalysts for the degradation of 4-nitrophenol (4-NP) in aqueous suspension, was performed by time-resolved microwave conductivity (TRMC) measurements and electronic paramagnetic resonance (EPR) and X-ray photoelectron (XPS) spectroscopies. The presence of porphyrin sensitizers, as the metal-free or Cu [5,10,15,20-tetra (4tert-butylphenyl)] porphyrin, impregnated onto the TiO 2 surface improved the photocatalytic activity of the bare TiO 2 . TRMC measurements indicate that the number and lifetime of the photoinduced excess charge carriers increase in the presence of the macrocycles, and EPR and XPS spectroscopies support the mechanistic hypotheses based on the photoreactivity experiments.
A Pt/TiO 2 catalyst has been subjected to reduction in hydrogen at 473, 573 and 773 K and the var... more A Pt/TiO 2 catalyst has been subjected to reduction in hydrogen at 473, 573 and 773 K and the various degrees of metal-support interaction (SMSI) confirmed by means of CO and H 2 chemisorption, FTIR of CO and the hydrogenation of crotonaldehyde. Coadsorption of CO and crotonaldehyde were performed to identify the preferred adsorption site and mode of adsorption of the unsaturated aldehyde. Results which appear to suggest shifts to lower frequencies of bands due to adsorbed carbonyls are not due to electronic effects induced by coadsorption, but rather indicate displacement of CO from the weaker bonding sites which eliminate dipole coupling effects between different carbonyl clusters, and consequently removes intensity transfer phenomena leading to enhancement in intensity at lower frequencies.
The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy s... more The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.
Thermochemical heat storage (TCS) based on redox cycles of metal oxides is a promising concept th... more Thermochemical heat storage (TCS) based on redox cycles of metal oxides is a promising concept that allows enhancing the energy generation dispatchability in concentrated solar power plants (CSP). Nevertheless, several factors that affect to the long term durability of these materials must be evaluated as to guarantee an efficient operation. Among others, the redox reversibility, reaction kinetics and material degradation are crucial factors, as they directly influence in the materials cycle stability. It has been found that sintering processes associated with the high operation temperature may produce a decrease on the oxidation kinetics. However, this study proves that, in the case of manganese oxides, such decrease can be attenuated by addition of small amount of iron, improving the redox performance of these materials.
Redox cycles of manganese oxides (Mn2 O3 /Mn3 O4 ) are a promising alternative for thermochemical... more Redox cycles of manganese oxides (Mn2 O3 /Mn3 O4 ) are a promising alternative for thermochemical heat storage systems coupled to concentrated solar power plants as manganese oxides are abundant and inexpensive materials. Although their cyclability for such a purpose has been proved, sintering processes, related to the high-temperature conditions at which charge-discharge cycles are performed, generally cause a cycle-to-cycle decrease in the oxidation rate of Mn3 O4 . To guarantee proper operation, both reactions should present stable reaction rates. In this study, it has been demonstrated that the incorporation of Fe, which is also an abundant material, into the manganese oxides improves the redox performance of this system by increasing the heat storage density, narrowing the redox thermal hysteresis, and, above all, stabilizing and enhancing the oxidation rate over long-term operation, which counteracts the negative effects caused by sintering, although its presence is not avoided.
Thermochemical energy storage (TCS) based on reduction-oxidation cycles of multivalent metal oxid... more Thermochemical energy storage (TCS) based on reduction-oxidation cycles of multivalent metal oxides is of great interest for concentrating solar facilities, as it can allow enhancing the global plant efficiency and improving the energy generation dispatchability. However, to guarantee the feasibility of the process, selected materials should present long term durability, which requires the evaluation of the redox couple cyclability. In this work we have demonstrated, for the first time, the suitability of the Mn 2 O 3 /Mn 3 O 4 pair for this application during 30 cycles, performed in thermobalance. Nevertheless, an appropriate design of such materials is crucial since it has been found that initial particle size influences the redox behaviour of these oxides. Results showed a 2-fold influence of particle size of the as-prepared materials on the redox reversibility. Firstly, this parameter affects to the thermodynamics and kinetics of the redox reactions. Namely a decrease of the particle size shifted the oxidation temperature to lower values and produced slower reduction and oxidation reactions. Secondly, depending on the particles size, samples followed different sintering mechanisms. This fact influenced dramatically the behaviour of the materials with lower particle size, which suffered from a higher degree of densification that eventually caused a total loss of cyclability. † Electronic supplementary information (ESI) available: XRD patterns; high resolution TEM micrographs; SEM micrographs, rst cooling step interval; DSC curves for M 1 sample. See
The reactivity of CeO2, pure or supported on alumina, in NO adsorption and catalytic activity for... more The reactivity of CeO2, pure or supported on alumina, in NO adsorption and catalytic activity for the CO+NO+O2 reaction (in the absence of metal), has been tested using IR, ESR and temperature-programmed desorption/reactivity techniques. Significant differences are found in alumina-supported ceria in comparison with pure CeO2; its lower activity can be connected to the difficulty of generating on well-dispersed CeO2/Al2O3
Research on photocatalytic materials has been a field in continuous expansion in the recent decad... more Research on photocatalytic materials has been a field in continuous expansion in the recent decades, as it is evidenced by the large number of articles published every year. So far, more than 190 different semiconductors have been assayed as suitable photocatalysts. To this figure, it is necessary to add the combinations with other functional materials or between different semiconductors, as well as their morphological modifications. Summing up the outcome of these different preparation strategies eventually leads to the enormous number of photocatalytic systems that have been reported in the scientific literature. Dealing with such an amount of information requires updated and educated guidance to select the most significant realizations, and it also calls for critical assessments on how the expectations are being fulfilled. This perspective article intends to assess the state of the art of photocatalysis with regard to materials and systems, considering the well-established results, but also the emerging aspects, and the envisaged new directions of this technology in the near future. In the first part, the most relevant achievements in this area, some of them already in the market while others still in development, will be reviewed according to the current understanding. The second part of the article is devoted to the most innovative and promising photocatalysts and related systems described in the open literature.
ABSTRACT Research for the development of more efficient photocatalysts has experienced an almost ... more ABSTRACT Research for the development of more efficient photocatalysts has experienced an almost exponential growth since its popularization in early 1970’s. Despite the advantages of the widely used TiO2, the yield of the conversion of sun power into chemical energy that can be achieved with this material is limited prompting the research and development of a number of structural, morphological and chemical modifications of TiO2 , as well as a number of novel photocatalysts with very different composition. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications provides a systematic account of the current understanding of the relationships between the physicochemical properties of the catalysts and photoactivity. The already long list of photocatalysts phases and their modifications is increasing day by day. By approaching this field from a material sciences angle, an integrated view allows readers to consider the diversity of photocatalysts globally and in connection with other technologies. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications provides a valuable road-map, outlining the common principles lying behind the diversity of materials, but also delimiting the imprecise border between the contrasted results and the most speculative studies. This broad approach makes it ideal for specialist but also for engineers, researchers and students in related fields http://www.springer.com/energy/renewable+and+green+energy/book/978-1-4471-5060-2
ABSTRACT A series of high-performance catalysts based on nickel phosphide particles supported on ... more ABSTRACT A series of high-performance catalysts based on nickel phosphide particles supported on SBA-15 have been synthesized by temperature-programed reduction of a nickel phosphate, previously impregnated in the mesostructured silica support. In these samples the loading of the active phase varied between 10% and 20% in a Ni basis, while nominal Ni/P ratios ranged from 0.5 to 3. The formation of different active phases, Ni2P, Ni12P5 or Ni3P, depending on the P/Ni proportion was verified by X-ray diffraction (XRD). The study of these catalysts by transmission electron microscopy (TEM) and Energy-Dispersive X-ray spectroscopy (EDX) revealed that the majority of the phosphide nanoparticles present a relatively uniform diameter evenly distributed within the SBA-15 channels. All the nickel phosphide catalysts, as well as a reference Ni/SBA-15 catalyst, were tested for the hydrodeoxygenation (HDO) of methyl oleate (C17H33-COO-CH3) in a high pressure continuous flow reactor. This compound was used as a convenient surrogate of triglyceride molecules present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes at 30 bars and temperature in the 250-340 °C range. In all cases lower contact time and reaction temperature decrease the conversion but favor the formation of C18 alkanes, which is the preferred product in terms of carbon atom economy. In addition, this study reveals that activity and selectivity are affected remarkably by the Ni/P ratio. Maximum conversion is achieved for the catalysts prepared with an initial Ni/P ratio of 1, while selectivity to C18 is larger for the catalyst with an initial Ni/P ratio of 2. These catalysts contain predominantly the Ni2P phase, which seem to be the most active for this process, although the presence of Ni12P5 in the case of the catalysts with Ni/P = 2 appears to be also positive. On the basis of the product distribution it can be concluded that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the nickel phosphide catalysts, whereas decarboxylation and cracking are the prevailing processes over the Ni/SBA-15 catalyst. Owing to these high yields of long-chain paraffins, SBA-15-supported nickel phosphide catalysts can be considered as a very promising catalyst for the transformation of vegetable oils into green diesel.
ABSTRACT It is believed that hydrogen will play a relevant role as an energy vector in the near f... more ABSTRACT It is believed that hydrogen will play a relevant role as an energy vector in the near future, but in order to fulfil these expectations the development of economically feasible routes with limited CO2 emissions is required. In this respect, catalysis is crucial in most of the possible processes for hydrogen generation and, accordingly, improvement in the catalyst properties should have a significant impact on the efficiency of the production. In particular, ordered mesoporous materials of different chemical composition (oxides and non-oxides) possess a high potential for improving a variety of catalytic routes for the production of low-carbon hydrogen. The activity of this type of catalyst is frequently enhanced due to a combination of high surface area, low diffusion restrictions, and high dispersion of the supported active phases. In this work, we review the latest advances in the use of these mesostructured catalysts in the most relevant routes for hydrogen generation with reduced greenhouse emissions: steam reforming of biomass derived feedstocks (biogas, ethanol, and glycerol), methane and ammonia decomposition and photocatalytic reduction using sacrificial electron donors.
ABSTRACT Hydrodeoxygenation (HDO) is considered one of the most promising routes to convert the p... more ABSTRACT Hydrodeoxygenation (HDO) is considered one of the most promising routes to convert the pyrolysis bio-oils produced from lignocellulose into biofuels very similar to those derived from petroleum. This work reports results obtained in the catalytic HDO of anisole over non-conventional hydrotreating catalysts based on metallic Ni and Co supported on micro-mesoporous carriers of different acidity. Anisole has been chosen as representative of those compounds, containing a methoxy-phenyl group, which are abundant in lignocellulose pyrolysis bio-oils. The effect of both metal phase and support properties on their performance as HDO catalysts has been studied. With this aim, three supports with different textural and acidic properties have been employed: hierarchical ZSM-5, mesostructured pure silica SBA-15 and mesostructured Al-SBA-15. The reactions have been carried out in a stainless steel high pressure batch reactor at 220 °C and with 50 bar of pure hydrogen.
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