Waste to fuel: designing a cobalt based catalyst and process for once-through Fischer-Tropsch synthesis operated at high conversion
type: CreativeWork
description: The production of fuels from waste on a small-scale decentralized level may enhance the liquid fuel security of Sub-Saharan Africa. The Fischer-Tropsch process can be used to convert waste into drop-in fuels. However, operating at small scale in remote locations requires a plant design with lower capital requirements, a greater level of simplicity and utility self-sufficiency. A plant design using an air-fed biogas reformer (without an air separation unit) and a single pass Fischer-Tropsch configuration is proposed. A fundamental requirement of this particular design is that it needs to operate at a higher FischerTropsch conversion than typically seen in industry (55 – 65%). High conversion conditions result in a high partial pressure of H2O and low partial pressures of CO and H2 within the Fischer-Tropsch reactor. These conditions have been reported to negatively affect the activity, selectivity and stability of cobalt-based catalysts. To date, no study has investigated the cause of this phenomenon, nor has a catalyst been developed specifically to operate under high conversion conditions. The objective of this study is to investigate the mechanisms behind these phenomena and provide catalyst design improvements that facilitate operation at high conversion conditions. Furthermore, a detailed design of the proposed once-through Fischer-Tropsch biogas-to-fuel plant will be evaluated using data from the catalytic experiments. An investigation into the effect of high conversion on the activity and selectivity of 0.05Pt-22Co/Al2O3 was conducted in a slurry bed reactor at T = 220°C, P = 20 bar, with a feed simulating synthesis gas generated from air-blown reforming (H2:CO:N2= 4:2:6). Space velocity was decreased to increase conversion to between XCO = 40% and XCO = 97%. The rate of CO consumption decreased with increasing conversion. Increasing the CO conversion was found to have negligible effect on CO2 selectivity (an unwanted by-product) up to a CO conversion of 75%, …
abstract: The production of fuels from waste on a small-scale decentralized level may enhance the liquid fuel security of Sub-Saharan Africa. The Fischer-Tropsch process can be used to convert waste into drop-in fuels. However, operating at small scale in remote locations requires a plant design with lower capital requirements, a greater level of simplicity and utility self-sufficiency. A plant design using an air-fed biogas reformer (without an air separation unit) and a single pass Fischer-Tropsch configuration is proposed. A fundamental requirement of this particular design is that it needs to operate at a higher FischerTropsch conversion than typically seen in industry (55 – 65%). High conversion conditions result in a high partial pressure of H2O and low partial pressures of CO and H2 within the Fischer-Tropsch reactor. These conditions have been reported to negatively affect the activity, selectivity and stability of cobalt-based catalysts. To date, no study has investigated the cause of this phenomenon, nor has a catalyst been developed specifically to operate under high conversion conditions. The objective of this study is to investigate the mechanisms behind these phenomena and provide catalyst design improvements that facilitate operation at high conversion conditions. Furthermore, a detailed design of the proposed once-through Fischer-Tropsch biogas-to-fuel plant will be evaluated using data from the catalytic experiments. An investigation into the effect of high conversion on the activity and selectivity of 0.05Pt-22Co/Al2O3 was conducted in a slurry bed reactor at T = 220°C, P = 20 bar, with a feed simulating synthesis gas generated from air-blown reforming (H2:CO:N2= 4:2:6). Space velocity was decreased to increase conversion to between XCO = 40% and XCO = 97%. The rate of CO consumption decreased with increasing conversion. Increasing the CO conversion was found to have negligible effect on CO2 selectivity (an unwanted by-product) up to a CO conversion of 75%, …
author: Tucker, Chelsea Lyn
keywords: Chemical Engineering
date published: 2020
date modified: 2026-07-24T01:33:57Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Chemical Engineering

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/33059