{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/286588"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/286588","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Studies of Carbon Dioxide Methanation and Related Phenomena in Porous Catalysts","abstract":"This Dissertation investigates the kinetics of CO2 methanation over nickel and cobalt catalysts. Methanation was studied for both Ni/γ-Al2O3 and Co/ZrO2 catalysts, which were synthesised using an incipient wetness impregnation technique and subsequently characterised using analyses based on gas adsorption, XRD, TPR and thermogravimetry. Separately a CO hydrogenation reaction, the Fischer-Tropsch process, was modelled numerically to examine the influence of mass transfer in practical, commercial pellets of catalyst. The kinetics of methanation was investigated for Ni/γ-Al2O3 over a wide range of reactant partial pressures using a gradientless, spinning-basket reactor operated in batch mode and in a laboratory-scale, continuous fixed-bed reactor. Langmuir-Hinshelwood kinetic models were developed to represent the observed kinetics in each reactor: these models were then compared. For the batch reactor, a rate expression based the dissociation of a chemisorbed CO intermediate being the rate-limiting step was found to be consistent with the experimental results. However, results from the fixed-bed suggested that the hydrogenation of an adsorbed C atom determined the rate of reaction. These differences in the kinetics on Ni/γ-Al2O3 between the fixed-bed and batch reactors suggest that a Langmuir approach using a single, rate-determining step may not be representative across all conversions. The rate over the Co/ZrO2 catalyst was characterised in the fixed-bed reactor over a range of reactant partial pressures at temperatures between 433 K and 503 K. The rate was observed to be dependent on hydrogen partial pressure and temperature, with the rate increasing with both. Previous research has reported a wide range of values of the apparent activation energy, with a study suggesting it was sensitive to pressure. Accordingly, the apparent activation energy was investigated for pressure sensitivity over a range of pressures between 5 and 15 barg: it was found to be constant. The values determined (~88-91±8 kJ/mol) were notably consistent with those reported for CO hydrogenation on cobalt. Kinetic schemes based on Langmuir-Hinshelwood and power law equations were evaluated, with the results best described by a reaction scheme based on the carbide pathway, with a rate-determining step of CH hydrogenation. A reaction-diffusion model of the Fischer-Tropsch process in a 2-D hollow cylinder was developed and analysed across a range of Thiele moduli and the extents of error in both effectiveness factor and selectivity were quantified relative to one-dimensional sphere and slab analogues. The errors between 2-D and 1-D analogues were found to be most significant between Thiele moduli of ~0.25 and ~3. Hollow cylinder effectiveness factors were bounded by those of sphere and slab above and below Thiele moduli of ~0.75 and ~1.15 respectively for the conditions examined, with the effectiveness factors exceeding those of both sphere and slab models between these moduli. A comparison of the hollow cylindrical pellets against spheres of equivalent volume demonstrated that hollow cylinders provided improved fixed-bed performance, with improved effectiveness factors and selectivities due to the lowered diffusion lengths of the hollow cylindrical geometry.","abstract_html":"This Dissertation investigates the kinetics of CO2 methanation over nickel and cobalt catalysts. Methanation was studied for both Ni/γ-Al2O3 and Co/ZrO2 catalysts, which were synthesised using an incipient wetness impregnation technique and subsequently characterised using analyses based on gas adsorption, XRD, TPR and thermogravimetry. Separately a CO hydrogenation reaction, the Fischer-Tropsch process, was modelled numerically to examine the influence of mass transfer in practical, commercial pellets of catalyst. The kinetics of methanation was investigated for Ni/γ-Al2O3 over a wide range of reactant partial pressures using a gradientless, spinning-basket reactor operated in batch mode and in a laboratory-scale, continuous fixed-bed reactor. Langmuir-Hinshelwood kinetic models were developed to represent the observed kinetics in each reactor: these models were then compared. For the batch reactor, a rate expression based the dissociation of a chemisorbed CO intermediate being the rate-limiting step was found to be consistent with the experimental results. However, results from the fixed-bed suggested that the hydrogenation of an adsorbed C atom determined the rate of reaction. These differences in the kinetics on Ni/γ-Al2O3 between the fixed-bed and batch reactors suggest that a Langmuir approach using a single, rate-determining step may not be representative across all conversions. The rate over the Co/ZrO2 catalyst was characterised in the fixed-bed reactor over a range of reactant partial pressures at temperatures between 433 K and 503 K. The rate was observed to be dependent on hydrogen partial pressure and temperature, with the rate increasing with both. Previous research has reported a wide range of values of the apparent activation energy, with a study suggesting it was sensitive to pressure. Accordingly, the apparent activation energy was investigated for pressure sensitivity over a range of pressures between 5 and 15 barg: it was found to be constant. The values determined (~88-91±8 kJ/mol) were notably consistent with those reported for CO hydrogenation on cobalt. Kinetic schemes based on Langmuir-Hinshelwood and power law equations were evaluated, with the results best described by a reaction scheme based on the carbide pathway, with a rate-determining step of CH hydrogenation. A reaction-diffusion model of the Fischer-Tropsch process in a 2-D hollow cylinder was developed and analysed across a range of Thiele moduli and the extents of error in both effectiveness factor and selectivity were quantified relative to one-dimensional sphere and slab analogues. The errors between 2-D and 1-D analogues were found to be most significant between Thiele moduli of ~0.25 and ~3. Hollow cylinder effectiveness factors were bounded by those of sphere and slab above and below Thiele moduli of ~0.75 and ~1.15 respectively for the conditions examined, with the effectiveness factors exceeding those of both sphere and slab models between these moduli. A comparison of the hollow cylindrical pellets against spheres of equivalent volume demonstrated that hollow cylinders provided improved fixed-bed performance, with improved effectiveness factors and selectivities due to the lowered diffusion lengths of the hollow cylindrical geometry.","abstract_has_math":false,"creators":["Hubble, Ross"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Dennis, John"],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-01-26","date_published":"2019-01-26","updated_at":"2026-07-22T22:24:06Z","subjects":["methanation","nickel","catalysis","Fischer-Tropsch","carbon dioxide"],"languages":["en"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/9dc9e2b0-0691-4f01-a312-143738b3969a/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.33900","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Dennis, John"]},{"key":"dc:creator","label":"Author","values":["Hubble, Ross"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2019-01-26"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/286588"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["methanation","nickel","catalysis","Fischer-Tropsch","carbon dioxide"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/9dc9e2b0-0691-4f01-a312-143738b3969a/download","https://www.rioxx.net/licenses/all-rights-reserved/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["10.17863/CAM.33900"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/337262b6-f140-4e2b-949b-0821140adffd/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This Dissertation investigates the kinetics of CO2 methanation over nickel and cobalt catalysts. Methanation was studied for both Ni/γ-Al2O3 and Co/ZrO2 catalysts, which were synthesised using an incipient wetness impregnation technique and subsequently characterised using analyses based on gas adsorption, XRD, TPR and thermogravimetry. Separately a CO hydrogenation reaction, the Fischer-Tropsch process, was modelled numerically to examine the influence of mass transfer in practical, commercial pellets of catalyst. The kinetics of methanation was investigated for Ni/γ-Al2O3 over a wide range of reactant partial pressures using a gradientless, spinning-basket reactor operated in batch mode and in a laboratory-scale, continuous fixed-bed reactor. Langmuir-Hinshelwood kinetic models were developed to represent the observed kinetics in each reactor: these models were then compared. For the batch reactor, a rate expression based the dissociation of a chemisorbed CO intermediate being the rate-limiting step was found to be consistent with the experimental results. However, results from the fixed-bed suggested that the hydrogenation of an adsorbed C atom determined the rate of reaction. These differences in the kinetics on Ni/γ-Al2O3 between the fixed-bed and batch reactors suggest that a Langmuir approach using a single, rate-determining step may not be representative across all conversions. The rate over the Co/ZrO2 catalyst was characterised in the fixed-bed reactor over a range of reactant partial pressures at temperatures between 433 K and 503 K. The rate was observed to be dependent on hydrogen partial pressure and temperature, with the rate increasing with both. Previous research has reported a wide range of values of the apparent activation energy, with a study suggesting it was sensitive to pressure. Accordingly, the apparent activation energy was investigated for pressure sensitivity over a range of pressures between 5 and 15 barg: it was found to be constant. The values determined (~88-91±8 kJ/mol) were notably consistent with those reported for CO hydrogenation on cobalt. Kinetic schemes based on Langmuir-Hinshelwood and power law equations were evaluated, with the results best described by a reaction scheme based on the carbide pathway, with a rate-determining step of CH hydrogenation. A reaction-diffusion model of the Fischer-Tropsch process in a 2-D hollow cylinder was developed and analysed across a range of Thiele moduli and the extents of error in both effectiveness factor and selectivity were quantified relative to one-dimensional sphere and slab analogues. The errors between 2-D and 1-D analogues were found to be most significant between Thiele moduli of ~0.25 and ~3. Hollow cylinder effectiveness factors were bounded by those of sphere and slab above and below Thiele moduli of ~0.75 and ~1.15 respectively for the conditions examined, with the effectiveness factors exceeding those of both sphere and slab models between these moduli. A comparison of the hollow cylindrical pellets against spheres of equivalent volume demonstrated that hollow cylinders provided improved fixed-bed performance, with improved effectiveness factors and selectivities due to the lowered diffusion lengths of the hollow cylindrical geometry."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["c7a753b203dafb8d78660d621e4d86e7","87eda9de84448d1f82354d60eee3eb5f"]},{"key":"dc:title","label":"Title","values":["Studies of Carbon Dioxide Methanation and Related Phenomena in Porous Catalysts"]}]}],"canonical_facts":{"dc:contributor.advisor":["Dennis, John"],"dc:creator":["Hubble, Ross"],"dc:date.issued":["2019-01-26"],"dc:description.abstract":["This Dissertation investigates the kinetics of CO2 methanation over nickel and cobalt catalysts. Methanation was studied for both Ni/γ-Al2O3 and Co/ZrO2 catalysts, which were synthesised using an incipient wetness impregnation technique and subsequently characterised using analyses based on gas adsorption, XRD, TPR and thermogravimetry. Separately a CO hydrogenation reaction, the Fischer-Tropsch process, was modelled numerically to examine the influence of mass transfer in practical, commercial pellets of catalyst. The kinetics of methanation was investigated for Ni/γ-Al2O3 over a wide range of reactant partial pressures using a gradientless, spinning-basket reactor operated in batch mode and in a laboratory-scale, continuous fixed-bed reactor. Langmuir-Hinshelwood kinetic models were developed to represent the observed kinetics in each reactor: these models were then compared. For the batch reactor, a rate expression based the dissociation of a chemisorbed CO intermediate being the rate-limiting step was found to be consistent with the experimental results. However, results from the fixed-bed suggested that the hydrogenation of an adsorbed C atom determined the rate of reaction. These differences in the kinetics on Ni/γ-Al2O3 between the fixed-bed and batch reactors suggest that a Langmuir approach using a single, rate-determining step may not be representative across all conversions. The rate over the Co/ZrO2 catalyst was characterised in the fixed-bed reactor over a range of reactant partial pressures at temperatures between 433 K and 503 K. The rate was observed to be dependent on hydrogen partial pressure and temperature, with the rate increasing with both. Previous research has reported a wide range of values of the apparent activation energy, with a study suggesting it was sensitive to pressure. Accordingly, the apparent activation energy was investigated for pressure sensitivity over a range of pressures between 5 and 15 barg: it was found to be constant. The values determined (~88-91±8 kJ/mol) were notably consistent with those reported for CO hydrogenation on cobalt. Kinetic schemes based on Langmuir-Hinshelwood and power law equations were evaluated, with the results best described by a reaction scheme based on the carbide pathway, with a rate-determining step of CH hydrogenation. A reaction-diffusion model of the Fischer-Tropsch process in a 2-D hollow cylinder was developed and analysed across a range of Thiele moduli and the extents of error in both effectiveness factor and selectivity were quantified relative to one-dimensional sphere and slab analogues. The errors between 2-D and 1-D analogues were found to be most significant between Thiele moduli of ~0.25 and ~3. Hollow cylinder effectiveness factors were bounded by those of sphere and slab above and below Thiele moduli of ~0.75 and ~1.15 respectively for the conditions examined, with the effectiveness factors exceeding those of both sphere and slab models between these moduli. A comparison of the hollow cylindrical pellets against spheres of equivalent volume demonstrated that hollow cylinders provided improved fixed-bed performance, with improved effectiveness factors and selectivities due to the lowered diffusion lengths of the hollow cylindrical geometry."],"dc:format.checksum.md5":["c7a753b203dafb8d78660d621e4d86e7","87eda9de84448d1f82354d60eee3eb5f"],"dc:identifier.doi":["10.17863/CAM.33900"],"dc:identifier.uri":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/337262b6-f140-4e2b-949b-0821140adffd/download"],"dc:language":["en"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/286588"],"dc:rights":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/9dc9e2b0-0691-4f01-a312-143738b3969a/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"dc:subject":["methanation","nickel","catalysis","Fischer-Tropsch","carbon dioxide"],"dc:title":["Studies of Carbon Dioxide Methanation and Related Phenomena in Porous Catalysts"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:06Z"}