Structure, adsorption properties and surface reactivity of Cu-ZnO/ZrO2 catalysts (ZrO2 loading, 4... more Structure, adsorption properties and surface reactivity of Cu-ZnO/ZrO2 catalysts (ZrO2 loading, 43 wt%; Zn/Cu (at/at), 0.0–2.8) have been probed by BET, XRD, TPR, N2O-titration, FTIR and TPD measurements of H2, CO and CO2. Characterization data indicate that ZnO promotes the dispersion and reactivity of metal copper to oxygen, while both ZnO and ZrO2 support markedly enhance the surface CO2 adsorption. A synergism of metal Cu hydrogenation and oxide basic sites discloses the primary role of the metal/oxide interface on the functionality of Cu-ZnO/ZrO2 catalysts in the CO2 to CH3OH hydrogenation reaction. The extent of the oxide/metal interface, probed both by Cuδ+/Cu0 and oxide-to-metal surface area (OSA/MSA) ratios, provides a normalization of the Cu site specific activity (TOF) in a wide range (3–60%) of metal dispersion proving the dual-site nature and, then, the formal structure-insensitive character of the title reaction.
Multifunctional CuZnZr-zeolite catalysts were investigated for the direct synthesis of dimethyl e... more Multifunctional CuZnZr-zeolite catalysts were investigated for the direct synthesis of dimethyl ether (DME) from carbon dioxide (CO 2) hydrogenation. Physical mixtures prepared by pre-pelletized CuZnZr methanol catalysts and home-made MFI-type zeolites as well as hybrid systems prepared by coprecipi-tation of metal-oxide precursors in solutions containing the zeolites were tested in a plug-flow reactor at 240 • C, pressure of 3.0–5.0 MPa and space velocity comprised between 2500 and 10,000 NL/kg cat /h. Preliminary experiments in methanol (MeOH) synthesis reaction from CO 2 –H 2 mixtures allowed to indi-viduate a suitable CuZnZr composition ensuring good activity in CO 2 conversion, high MeOH selectivity and limited CO formation. Parallel tests in MeOH-to-DME reaction were also carried out to investigate the functionality of the zeolites prepared. The results disclosed that an optimal Si/Al ratio is necessary to obtain dehydration catalysts characterized by suitable acidity and good...
a b s t r a c t NiCu/Ce 0.9 Gd 0.1 O 2−ı (CGO) catalysts were prepared by different techniques wi... more a b s t r a c t NiCu/Ce 0.9 Gd 0.1 O 2−ı (CGO) catalysts were prepared by different techniques with the aim to develop a bifunctional catalyst, characterized both by catalytic and anodic properties for integrated biogas SOFC process. Catalytic measurements have been performed in CO 2 reforming of CH 4 , using a fixed bed reac-tor at a reaction temperature ranging from 650 to 800 • C. Results revealed that NiCu/CGO system is a promising catalyst for the conversion of biogas mixtures at temperature suitable to be used in low temperature solid oxide fuel cell (LT-SOFC). Characterization data clearly demonstrated that NiCu alloy forms by reduction of NiCuO x mixed oxide patches, while catalytic testing showed carbon-free operation at 800 • C (GHSV = 6600 h −1) when "CO 2 -rich" biogas mixtures are used. By a thermodynamic evaluation of the different reaction kinetics, the poor efficiency of the catalyst in promoting the carbon gasification by CO 2 reaction has been assessed. C...
A series of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts for the one-step CO2-to-DME hydrogenatio... more A series of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts for the one-step CO2-to-DME hydrogenation reaction was prepared via coprecipitation of methanol catalyst precursors by means of different precipitating agents (i.e., sodium bicarbonate, ammonium carbonate, oxalic acid and urea) in a slurry containing dispersed zeolite particles. The samples were characterized by XRF, XRD, N2 adsorption/desorption isotherms, SEM, N2O-titration, TPR and NH3/CO2 TPD techniques, while the catalytic testing was carried out in a fixed-bed reactor operating at 3.0 MPa, in the TR range 473–513 K and space velocity of 10,000 h−1 (CO2/H2/N2, 3/9/1). The experiments revealed that the preparation methodology significantly affects catalyst properties and hence catalyst activity. The multifunctional catalyst prepared via ammonium carbonate precipitation resulted to be the most active in CO2 conversion, also accomplishing high DME selectivity, with a maximum space-time yield of 0.225 kgDME/kgcat/h. Catalyst ...
The effects of the most largely employed preparation methods (i.e., coprecipitation with sodium b... more The effects of the most largely employed preparation methods (i.e., coprecipitation with sodium bicarbonate, complexation with citric acid, gel-oxalate coprecipitation) on the structure and catalytic behaviour of Cu-Zn-Zr systems for methanol synthesis from hydrogenation of carbon dioxide have been studied. The characterization data of the dried, calcined and reduced catalysts showed that the physico-chemical properties can be controlled by varying composition and preparation method. The catalyst obtained by the gel-coprecipitation procedure showed the highest catalytic activity in the TR range 453-513 K, 3.0 MPa and 10,000 h−1, due to a superior functionality in the CO2 and H2 activation. An adequate balance between metal and oxide surface sites, in correspondence of a well defined particle size, was proposed to be crucial to design active and selective catalysts for such reaction. The good performance of the gel-oxalate coprecipitated catalyst was confirmed by an endurance test (≈...
Ni and Co supported on SiO2 and Al2O3 silica cloth thin layer catalysts have been investigated in... more Ni and Co supported on SiO2 and Al2O3 silica cloth thin layer catalysts have been investigated in the catalytic decomposition of natural gas (CDNG) reaction. The influence of carrier nature and reaction temperature was evaluated with the aim to individuate the key factors affecting coke formation. Both Ni and Co silica supported catalysts, due to the low metal support interaction (MSI), promotes the formation of carbon filament with particles at tip. On the contrary, in case alumina was used as support, metals strongly interact with surface thus depressing both the metal sintering and the detachment of particles from catalyst surface. In such cases, carbon grows on metal particle with a “base mechanism” while particles remain well anchored on the catalyst surface. This allowed to realize a cyclic dual-step process based on methane decomposition and catalyst oxygen regeneration without deactivation of catalyst. Technological considerations have led to conclude that the implement of a...
Studies in Surface Science and Catalysis - STUD SURF SCI CATAL, 2007
Several iron-based catalysts supported on different oxide carriers (CeO2, MnO, ZnO) were synthesi... more Several iron-based catalysts supported on different oxide carriers (CeO2, MnO, ZnO) were synthesized by the combustion route and probed in the Fischer-Tropsch synthesis reaction in the range 250-300°C and at 10-20 bar total pressure, using a PF-reactor and various COx reaction mixtures (H2/CO=2 or H2/CO2=3 or (CO+CO2)/H2=2). The prepared catalysts feature a catalytic performance superior to that of commercial FT catalysts and suitable for industrial application as a very high activity (100-60 of COx conversion), selectivity (low methane and high long-chain product selectivity; ASF parameter close to 0.9) and long lifetime (500 h).
The hydrogen production through the decomposition of methane into hydrogen and carbon on Ni suppo... more The hydrogen production through the decomposition of methane into hydrogen and carbon on Ni supported catalysts followed by catalyst regeneration in oxidative atmosphere was evaluated. Typical temperature programmed catalytic reaction (TPCR) results revealed that the nature of the carrier slightly affects the onset temperature of CH4 decomposition, while catalytic performance and regeneration capacity in O2 or CO2 streams depend on
The heterogeneous catalytic etherification of glycerol with tert-butyl alcohol was investigated i... more The heterogeneous catalytic etherification of glycerol with tert-butyl alcohol was investigated in presence of lab-made silica supported acid catalysts. As reference, two commercial acid ion-exchange resins were also used. Experiments were carried out in batch mode at TR ranging from 303 to 363K. An increase in reaction temperature favors the formation of di-substituted ethers. The etherification reaction proceeds according to
The effects of the preparation method (deposition–precipitation, incipient-wetness, combustion) o... more The effects of the preparation method (deposition–precipitation, incipient-wetness, combustion) on the structure and redox properties of 1% Au/CeO2 catalyst have been probed by TPR, XRD, and TEM techniques. The catalytic pattern in total (COX) and selective (SCOX) CO oxidation has been assessed by temperature programmed reaction tests in the range 273–473K. Controlling residual chlorine, the synthesis route determines the strength
Structure, adsorption properties and surface reactivity of Cu-ZnO/ZrO2 catalysts (ZrO2 loading, 4... more Structure, adsorption properties and surface reactivity of Cu-ZnO/ZrO2 catalysts (ZrO2 loading, 43 wt%; Zn/Cu (at/at), 0.0–2.8) have been probed by BET, XRD, TPR, N2O-titration, FTIR and TPD measurements of H2, CO and CO2. Characterization data indicate that ZnO promotes the dispersion and reactivity of metal copper to oxygen, while both ZnO and ZrO2 support markedly enhance the surface CO2 adsorption. A synergism of metal Cu hydrogenation and oxide basic sites discloses the primary role of the metal/oxide interface on the functionality of Cu-ZnO/ZrO2 catalysts in the CO2 to CH3OH hydrogenation reaction. The extent of the oxide/metal interface, probed both by Cuδ+/Cu0 and oxide-to-metal surface area (OSA/MSA) ratios, provides a normalization of the Cu site specific activity (TOF) in a wide range (3–60%) of metal dispersion proving the dual-site nature and, then, the formal structure-insensitive character of the title reaction.
Multifunctional CuZnZr-zeolite catalysts were investigated for the direct synthesis of dimethyl e... more Multifunctional CuZnZr-zeolite catalysts were investigated for the direct synthesis of dimethyl ether (DME) from carbon dioxide (CO 2) hydrogenation. Physical mixtures prepared by pre-pelletized CuZnZr methanol catalysts and home-made MFI-type zeolites as well as hybrid systems prepared by coprecipi-tation of metal-oxide precursors in solutions containing the zeolites were tested in a plug-flow reactor at 240 • C, pressure of 3.0–5.0 MPa and space velocity comprised between 2500 and 10,000 NL/kg cat /h. Preliminary experiments in methanol (MeOH) synthesis reaction from CO 2 –H 2 mixtures allowed to indi-viduate a suitable CuZnZr composition ensuring good activity in CO 2 conversion, high MeOH selectivity and limited CO formation. Parallel tests in MeOH-to-DME reaction were also carried out to investigate the functionality of the zeolites prepared. The results disclosed that an optimal Si/Al ratio is necessary to obtain dehydration catalysts characterized by suitable acidity and good...
a b s t r a c t NiCu/Ce 0.9 Gd 0.1 O 2−ı (CGO) catalysts were prepared by different techniques wi... more a b s t r a c t NiCu/Ce 0.9 Gd 0.1 O 2−ı (CGO) catalysts were prepared by different techniques with the aim to develop a bifunctional catalyst, characterized both by catalytic and anodic properties for integrated biogas SOFC process. Catalytic measurements have been performed in CO 2 reforming of CH 4 , using a fixed bed reac-tor at a reaction temperature ranging from 650 to 800 • C. Results revealed that NiCu/CGO system is a promising catalyst for the conversion of biogas mixtures at temperature suitable to be used in low temperature solid oxide fuel cell (LT-SOFC). Characterization data clearly demonstrated that NiCu alloy forms by reduction of NiCuO x mixed oxide patches, while catalytic testing showed carbon-free operation at 800 • C (GHSV = 6600 h −1) when "CO 2 -rich" biogas mixtures are used. By a thermodynamic evaluation of the different reaction kinetics, the poor efficiency of the catalyst in promoting the carbon gasification by CO 2 reaction has been assessed. C...
A series of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts for the one-step CO2-to-DME hydrogenatio... more A series of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts for the one-step CO2-to-DME hydrogenation reaction was prepared via coprecipitation of methanol catalyst precursors by means of different precipitating agents (i.e., sodium bicarbonate, ammonium carbonate, oxalic acid and urea) in a slurry containing dispersed zeolite particles. The samples were characterized by XRF, XRD, N2 adsorption/desorption isotherms, SEM, N2O-titration, TPR and NH3/CO2 TPD techniques, while the catalytic testing was carried out in a fixed-bed reactor operating at 3.0 MPa, in the TR range 473–513 K and space velocity of 10,000 h−1 (CO2/H2/N2, 3/9/1). The experiments revealed that the preparation methodology significantly affects catalyst properties and hence catalyst activity. The multifunctional catalyst prepared via ammonium carbonate precipitation resulted to be the most active in CO2 conversion, also accomplishing high DME selectivity, with a maximum space-time yield of 0.225 kgDME/kgcat/h. Catalyst ...
The effects of the most largely employed preparation methods (i.e., coprecipitation with sodium b... more The effects of the most largely employed preparation methods (i.e., coprecipitation with sodium bicarbonate, complexation with citric acid, gel-oxalate coprecipitation) on the structure and catalytic behaviour of Cu-Zn-Zr systems for methanol synthesis from hydrogenation of carbon dioxide have been studied. The characterization data of the dried, calcined and reduced catalysts showed that the physico-chemical properties can be controlled by varying composition and preparation method. The catalyst obtained by the gel-coprecipitation procedure showed the highest catalytic activity in the TR range 453-513 K, 3.0 MPa and 10,000 h−1, due to a superior functionality in the CO2 and H2 activation. An adequate balance between metal and oxide surface sites, in correspondence of a well defined particle size, was proposed to be crucial to design active and selective catalysts for such reaction. The good performance of the gel-oxalate coprecipitated catalyst was confirmed by an endurance test (≈...
Ni and Co supported on SiO2 and Al2O3 silica cloth thin layer catalysts have been investigated in... more Ni and Co supported on SiO2 and Al2O3 silica cloth thin layer catalysts have been investigated in the catalytic decomposition of natural gas (CDNG) reaction. The influence of carrier nature and reaction temperature was evaluated with the aim to individuate the key factors affecting coke formation. Both Ni and Co silica supported catalysts, due to the low metal support interaction (MSI), promotes the formation of carbon filament with particles at tip. On the contrary, in case alumina was used as support, metals strongly interact with surface thus depressing both the metal sintering and the detachment of particles from catalyst surface. In such cases, carbon grows on metal particle with a “base mechanism” while particles remain well anchored on the catalyst surface. This allowed to realize a cyclic dual-step process based on methane decomposition and catalyst oxygen regeneration without deactivation of catalyst. Technological considerations have led to conclude that the implement of a...
Studies in Surface Science and Catalysis - STUD SURF SCI CATAL, 2007
Several iron-based catalysts supported on different oxide carriers (CeO2, MnO, ZnO) were synthesi... more Several iron-based catalysts supported on different oxide carriers (CeO2, MnO, ZnO) were synthesized by the combustion route and probed in the Fischer-Tropsch synthesis reaction in the range 250-300°C and at 10-20 bar total pressure, using a PF-reactor and various COx reaction mixtures (H2/CO=2 or H2/CO2=3 or (CO+CO2)/H2=2). The prepared catalysts feature a catalytic performance superior to that of commercial FT catalysts and suitable for industrial application as a very high activity (100-60 of COx conversion), selectivity (low methane and high long-chain product selectivity; ASF parameter close to 0.9) and long lifetime (500 h).
The hydrogen production through the decomposition of methane into hydrogen and carbon on Ni suppo... more The hydrogen production through the decomposition of methane into hydrogen and carbon on Ni supported catalysts followed by catalyst regeneration in oxidative atmosphere was evaluated. Typical temperature programmed catalytic reaction (TPCR) results revealed that the nature of the carrier slightly affects the onset temperature of CH4 decomposition, while catalytic performance and regeneration capacity in O2 or CO2 streams depend on
The heterogeneous catalytic etherification of glycerol with tert-butyl alcohol was investigated i... more The heterogeneous catalytic etherification of glycerol with tert-butyl alcohol was investigated in presence of lab-made silica supported acid catalysts. As reference, two commercial acid ion-exchange resins were also used. Experiments were carried out in batch mode at TR ranging from 303 to 363K. An increase in reaction temperature favors the formation of di-substituted ethers. The etherification reaction proceeds according to
The effects of the preparation method (deposition–precipitation, incipient-wetness, combustion) o... more The effects of the preparation method (deposition–precipitation, incipient-wetness, combustion) on the structure and redox properties of 1% Au/CeO2 catalyst have been probed by TPR, XRD, and TEM techniques. The catalytic pattern in total (COX) and selective (SCOX) CO oxidation has been assessed by temperature programmed reaction tests in the range 273–473K. Controlling residual chlorine, the synthesis route determines the strength
Uploads
Papers by Giuseppe Bonura