Selective Oxidation Reactions: A Chemical Looping Approach
type: CreativeWork
description: The production of chemicals is a key contributor to industrial energy demand and greenhouse gas emissions. Chemical looping (CL) offers a novel route to improve energy efficiency and environmental performance, hence investigated in this Dissertation for two selective oxidation reactions: (i) the epoxidation of ethylene to ethylene oxide, and (ii) the oxidative dehydrogenation (ODH) of ethane to ethylene. CL approach depends on the redox cycling of a solid oxygen carrier, typically a metal oxide, which donates oxygen at typical reaction conditions, eliminating the need of a gaseous feed of molecular oxygen. The oxygen carrier is then regenerated by exposure to air to be ready for reuse in the principal reaction. By eliminating the cofeeding of gaseous oxygen and flammable reactants, the CL approach can render reactions safer, and, potentially, more selective and intensive. In the reactions of interest, a catalyst was supported on the oxygen carrier: a critical requirement is to synthesise carriers such that inter al. donation of oxygen to the catalyst occurs at the optimum temperature for the catalyst. For CL-epoxidation, Ag catalyst was supported on SrFeO3 as an oxygen carrier. The influence of oxygen carrier composition was investigated by generating carriers containing different ratios of the perovskite phases SrFeO3 and Sr3Fe2O7. Maximum yield of ethylene oxide was obtained for the sample with 1:1 SrFeO3: Sr3Fe2O7 ratio, leading to an increase in the yield of ethylene oxide around 4 times, compared to only SrFeO3. Despite the improved yield of ethylene oxide, the catalytic activities of the investigated catalysts were still too low to enable CL to be feasible for the commercial production of ethylene oxide. It was found that multiple factors might be hindering the activity of CL-epoxidation catalysts, including: (i) the depletion of the oxygen reservoir of the carrier, (ii) the contamination of the surface of the oxygen carrier with carbon-based species, such as …
abstract: The production of chemicals is a key contributor to industrial energy demand and greenhouse gas emissions. Chemical looping (CL) offers a novel route to improve energy efficiency and environmental performance, hence investigated in this Dissertation for two selective oxidation reactions: (i) the epoxidation of ethylene to ethylene oxide, and (ii) the oxidative dehydrogenation (ODH) of ethane to ethylene. CL approach depends on the redox cycling of a solid oxygen carrier, typically a metal oxide, which donates oxygen at typical reaction conditions, eliminating the need of a gaseous feed of molecular oxygen. The oxygen carrier is then regenerated by exposure to air to be ready for reuse in the principal reaction. By eliminating the cofeeding of gaseous oxygen and flammable reactants, the CL approach can render reactions safer, and, potentially, more selective and intensive. In the reactions of interest, a catalyst was supported on the oxygen carrier: a critical requirement is to synthesise carriers such that inter al. donation of oxygen to the catalyst occurs at the optimum temperature for the catalyst. For CL-epoxidation, Ag catalyst was supported on SrFeO3 as an oxygen carrier. The influence of oxygen carrier composition was investigated by generating carriers containing different ratios of the perovskite phases SrFeO3 and Sr3Fe2O7. Maximum yield of ethylene oxide was obtained for the sample with 1:1 SrFeO3: Sr3Fe2O7 ratio, leading to an increase in the yield of ethylene oxide around 4 times, compared to only SrFeO3. Despite the improved yield of ethylene oxide, the catalytic activities of the investigated catalysts were still too low to enable CL to be feasible for the commercial production of ethylene oxide. It was found that multiple factors might be hindering the activity of CL-epoxidation catalysts, including: (i) the depletion of the oxygen reservoir of the carrier, (ii) the contamination of the surface of the oxygen carrier with carbon-based species, such as …
author: Gabra, Samuel
language: eng
keywords: Selective Oxidation, Value-added Chemicals, Chemical Looping
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2022-01-30
date modified: 2026-07-22T22:24:00Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.86675