List of Titles

An easy two-step microwave assisted synthesis of SnO2/CNT hybrids

- Motshekga, Sarah C, Pillai, Sreejarani K, Ray, Suprakas Sinha, Jalama, Kalala, Krause, Rui.W.M

Authors: Motshekga, Sarah C , Pillai, Sreejarani K , Ray, Suprakas Sinha , Jalama, Kalala , Krause, Rui.W.M
Date: 2011
Subjects: X-ray diffraction , Electron microscopy , Nanotechnology , Ceramic engineering , Microwave synthesis , Nanoparticles , Carbon nanotubes
Type: Article
Identifier: uj:6239 , ISBN 9781118059920 , http://hdl.handle.net/10210/8180
Description: Tin oxide (SnO2) - decorated carbon nanotube (CNT) heterostructures were synthesized by microwave assisted wet impregnation method. CNTs of three different aspect ratios were compared. The hybrid samples were characterized by powder X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy, BET surface area analysis and DC conductivity measurement. The results showed that the microwave assisted synthesis is a very efficient method in producing CNTs that are heavily decorated by SnO2 nanoparticles in a very short time (total reaction time of 10 min.), irrespective of their length and diameter. The hybrids showed 100 times increase in electrical conductivity when compared to the unmodified CNTs.
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Assessment of carbon capture and sequestration : an investigation on algae growth rate under controlled environmental conditions

- Chauke, Jeffrey, Ndleve, Lunghile, Griffiths, Craig, Hausberger, Brendon, Jalama, Kalala

Authors: Chauke, Jeffrey , Ndleve, Lunghile , Griffiths, Craig , Hausberger, Brendon , Jalama, Kalala
Date: 2016
Subjects: Carbon Capture , Algae , Sequestration
Language: English
Type: Conference proceedings
Identifier: http://hdl.handle.net/10210/214209 , uj:21251 , Citation: Chauke, J. et al. 2016. Assessment of carbon capture and sequestration : an investigation on algae growth rate under controlled environmental conditions.
Description: Abstract: Current challenges on CO2 emissions and climate change require cost-effective techniques for carbon capture and sequestration. The aim of this study was to investigate algae growth under controlled environmental conditions for CO2 sequestration. An algae strain from a local lake was used in this study and inoculation tests were performed at 22, 32 and 38oC. The highest algae growth was observed around 22oC.
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Biodiesel production from waste vegetable oils over MgO/Al2O3 catalyst

- Sithole, Thembi, Jalama, Kalala, Meijboom, Reinout

Authors: Sithole, Thembi , Jalama, Kalala , Meijboom, Reinout
Date: 2014
Subjects: Waste vegetable oils , Biodiesel fuels industry , Vegetable oils as fuel , Vegetable oils - Industrial applications
Type: Article
Identifier: uj:5029 , ISSN 1662-7482 , http://hdl.handle.net/10210/13549
Description: MgO/Al2O3 catalysts with 10 and 20 wt.% MgO loadings have been prepared by incipient wetness impregnation method. A low-surface area alumina with small pore sizes was used as catalyst support to stabilise most of the MgO particles on the external surface area of the support. The prepared catalysts were subsequently tested in the conversion of a waste vegetable oil to biodiesel. The waste vegetable oil conversion was found to increase with the increase in reaction temperature, reaction time and MgO loading in the catalyst.
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Biodiesel production over ZnO/TiO₂ catalyst : effect of co-solvent, temperature and reaction time

- Mahangani, Ndanganeni, Vunain, Ephraim, Meijboom, Reinout, Jalama, Kalala

Authors: Mahangani, Ndanganeni , Vunain, Ephraim , Meijboom, Reinout , Jalama, Kalala
Date: 2015-07-01
Subjects: Biodiesel , Hexane , Waste vegetable oils
Type: Article
Identifier: uj:5127 , ISBN 9789881404701 , http://hdl.handle.net/10210/14090
Description: The aim of this work was to produce biodiesel from waste vegetable oil over ZnO/TiO2 catalysts as well as investigating the effect of co-solvent (hexane), reaction temperature and time on waste vegetable oil conversion to biodiesel. Production of biodiesel from virgin oil is still a downfall in commercial processes due to high cost. Thus, the process of producing biodiesel from waste vegetable oil over a TiO2-supported ZnO catalyst was studied in the absence and the presence of hexane as co-solvent respectively. The conversion of waste vegetable oil was found to increase with temperature and reaction time. The highest conversion that has been achieved was 99.1% at a temperature of 200 Â°C after 15 min of reaction for the reaction using hexane as co-solvent. The use of hexane as co-solvent was found to increase the oil conversion at lower reaction temperature and no effect was observed at higher temperatures.
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Carbon dioxide hydrogenation over nickel-, ruthenium- and copperbased catalysts: review of kinetics and mechanism

- Jalama, Kalala

Authors: Jalama, Kalala
Date: 2017
Subjects: CO2 hydrogenation , Nickel , Ruthenium
Language: English
Type: Article
Identifier: http://hdl.handle.net/10210/246276 , uj:25526 , Citation: Jalama, K. 2017. Carbon dioxide hydrogenation over nickel-, ruthenium- and copperbased catalysts: review of kinetics and mechanism.
Description: Abstract: This study critically reviews the mechanism of CO2 hydrogenation over Ni, Ru and Cu, and the effect of catalyst properties and operating conditions on reaction kinetics. Most studies have reported the presence of CO and formate species on Ni-, Ru- and Cu-based catalysts, where subsequent conversion of these species depends on the type of catalyst and the physicochemical properties of the catalyst support. Methane is the major product that forms during CO2 hydrogenation over Ni and Ru catalysts, while methanol and CO are mainly produced on Cu catalysts. A different approach for catalyst formulations and/or process development is required where long chain hydrocarbons are desired.
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Catalyst deactivation rate during hydrogenation of CO2 to longer chained hydrocarbons over 6 wt.% potassium-promoted Co/Al2O3 catalyst

- Khangale, Phathutshedzo R., Meijboom, Reinout, Jalama, Kalala

Authors: Khangale, Phathutshedzo R. , Meijboom, Reinout , Jalama, Kalala
Date: 2020
Subjects: Co/Al2O3 catalyst , Potassium , CO2 hydrogenation
Language: English
Type: Article
Identifier: http://hdl.handle.net/10210/470033 , uj:42209 , Citation: Khangale, P.R., Meijboom, R. & Jalama, K. 2020. Catalyst deactivation rate during hydrogenation of CO2 to longer chained hydrocarbons over 6 wt.% potassium-promoted Co/Al2O3 catalyst.
Description: Abstract: Please refer to full text to view abstract.
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CO2 hydrogenation to liquid hydrocarbons via modified Fi scher Tropsch over alumina supported cobalt catalyst s : effect of operating temperature, pressure and potassium loading

- Khangale, Phathutshedzo R., Meijboom, Reinout, Jalama, Kalala

Authors: Khangale, Phathutshedzo R. , Meijboom, Reinout , Jalama, Kalala
Date: 2020
Subjects: CO2 hydrogenation; , Potassium , Temperature
Language: English
Type: Article
Identifier: http://hdl.handle.net/10210/435807 , uj:37781 , Citation: Khangale, P.R., Meijboom, R. & Jalama, K. 2020. CO2 hydrogenation to liquid hydrocarbons via modified Fi scher Tropsch over alumina supported cobalt catalyst s : effect of operating temperature, pressure and potassium loading.
Description: Abstract: The effect of promoting 15%Co/Al2O3 catalyst with potassium on CO2 hydrogenation to longer-chain hydrocarbons was investigated. The catalysts used in this study were synthesized using an incipient wetness impregnation of the support with nitrate solutions. All catalysts were supported on γ-alumina and promoted with potassium (0 – 8%). The synthesized catalysts were characterized by XRD, BET, XPS, TPR and CO2-TPD analyses. The catalysts were evaluated for CO2 hydrogenation using a fixed-bed tube reactor. The CO2 conversion was found to increase with both the reaction temperature and pressure. The TPR data revealed that potassium limited the reduction of the catalyst, decreased the selectivity to methane and increased the selectivity to C2+ hydrocarbons. The maximum C2+ yield of 10.2%, with CO2 conversion of 42.3%, was obtained when 6 wt.% of potassium was added to the catalyst. It is believed that during the CO2 hydrogenation process over the catalysts that were promoted with potassium, CO2 is first converted to CO via reverse–water–gas–shift reaction, followed by subsequent hydrogenation of CO to hydrocarbons.
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Economics of carbon sequestration using algae

- Ndleve, Lunghile, Hausberger, Brendon, Jalama, Kalala

Authors: Ndleve, Lunghile , Hausberger, Brendon , Jalama, Kalala
Date: 2016
Subjects: Algae , Carbon , Economics
Language: English
Type: Conference proceedings
Identifier: http://hdl.handle.net/10210/214360 , uj:21271 , Citation: Ndleve, L., Hausberger, B & Jalama, K. 2016. Economics of carbon sequestration using algae.
Description: Abstract: This research examines the various carbon sequestration options and the impact of these on the economic viability of various carbon capture solutions when measured against algal based options. The base case of a coal fed Fischer - Tropsch facility is used to quantify the impact of these options.
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Effect of operating temperature, pressure and potassium loading on the performance of silica-supported cobalt catalyst in CO2 hydrogenation to hydrocarbon fuel

- Iloy, Rama Achtar, Jalama, Kalala

Authors: Iloy, Rama Achtar , Jalama, Kalala
Date: 2019
Subjects: CO2 hydrogenation , Cobalt , Potassium
Language: English
Type: Article
Identifier: http://hdl.handle.net/10210/405441 , uj:34046 , Citation: Lloy, R.A., Kalala, J. 2019 : Effect of operating temperature, pressure and potassium loading on the performance of silica-supported cobalt catalyst in CO2 hydrogenation to hydrocarbon fuel.
Description: Abstract :
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Effect of space velocity on alumina supported cobalt catalyst performance for fischer-tropsch reaction

- Khangale, Rodney P., Meijboom, Reinout, Jalama, Kalala

Authors: Khangale, Rodney P. , Meijboom, Reinout , Jalama, Kalala
Date: 2016
Subjects: Co/Al2O3 catalyst , Fischer-Tropsch , Space velocity
Language: English
Type: Conference proceedings
Identifier: http://hdl.handle.net/10210/214368 , uj:21272 , Citation: Khangale, R.P., Meijboom, R & Jalama, K. 2016. Effect of space velocity on alumina supported cobalt catalyst performance for fischer-tropsch reaction.
Description: Abstract: Co/ɣ-Al2O3 catalyst was prepared by incipient wetness impregnation of the ɣ-Al2O3 support using an aqueous solution of cobalt nitrate. The catalyst was characterized by XRD, BET and TPR. It was evaluated in a fixed-bed reactor to determine the effect of space velocity on the CO conversion, CO conversion rate, CH4 selectivity and C5+ selectivity during Fischer-Tropsch reaction. CO conversion decreased while the CO conversion rate linearly increased with increasing the space velocity. The CH4 selectivity was not significantly affected by the space velocity as it fluctuated between 5 and 6%.
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Effect of Total Pressure on CO Conversion and CH4 Selectivity during Fischer-Tropsch Reaction over Gold-promoted Cobalt Catalyst

- Baloyi, Jason, Nkosi, E.N., Khangale, Rodney P., Jalama, Kalala

Authors: Baloyi, Jason , Nkosi, E.N. , Khangale, Rodney P. , Jalama, Kalala
Date: 2016
Subjects: Au/Co catalyst , Fischer-Tropsch , Total pressure
Language: English
Type: Conference proceedings
Identifier: http://hdl.handle.net/10210/214376 , uj:21273 , Citation: Baloyi, J. et al. 2016. Effect of space velocity on alumina supported cobalt catalyst performance for fischer-tropsch reaction.
Description: Abstract: Au-promoted cobalt catalyst was prepared by two-step precipitation-deposition of cobalt and gold on a gamma alumina support. The prepared catalyst was characterized by XRD and BET, and used in a laboratory fixed-bed reactor to evaluate the effect of Fischer-Tropsch (FT) reaction total pressure on carbon monoxide conversion and methane selectivity. Carbon monoxide conversion was found to increase with an increase in system pressure and passed through a maximum at a pressure around 5 bar. The methane selectivity was very low and unexpectedly increased at high operating pressure.
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Energy requirement estimates for two step ethanolysis of waste vegetable oils for biodiesel production

- Ligeris, Nikolas, Jalama, Kalala

Authors: Ligeris, Nikolas , Jalama, Kalala
Date: 2014
Subjects: Waste vegetable oils , Biodiesel , Ethanol
Type: Article
Identifier: uj:5052 , http://hdl.handle.net/10210/13591
Description: ChemCad 6.4 simulation package was used to model a two-step biodiesel production process from waste vegetable oils (WVO) and ethanol using homogeneous acid and alkali catalysts respectively. The developed process flowsheet consisted of pre-esterification and transesterification of WVO, ethanol and glycerol recovery, and biodiesel refining. The energy required for each processing unit as well as the energy required for the whole process have been estimated. Ethanol recovery accounted for the highest portion of the energy required for the entire process estimated as 2.75 MJ per kg of biodiesel produced.
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Fischer-Tropsch synthesis over Co/Tio2 catalyst : effect of catalyst activation by CO compared to H2

- Jalama, Kalala

Authors: Jalama, Kalala
Date: 2016
Subjects: Catalyst activation , CO , H2 , Fischer-tropsch
Language: English
Type: Article
Identifier: http://hdl.handle.net/10210/93835 , uj:20397 , Citation: Jalama, K. 2016. Fischer-Tropsch synthesis over Co/Tio2 catalyst : effect of catalyst activation by CO compared to H2.
Description: Abstract: Co/TiO2 catalyst activation for Fischer-Tropsch (FT) reaction by CO in comparison to H2 has been performed. The catalyst, prepared by incipient wetness impregnation, has been characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses after separate reduction using CO and H2 respectively. Temperature programmed reduction (TPR) analyses were also conducted to study the reduction behaviour of the catalyst in presence of H2 and CO respectively. CO improved catalyst reduction and produced a more stable and active catalyst with higher selectivity and yield for C5+ hydrocarbons at extended time-on-stream.
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Fischer-Tropsch Synthesis over Fe/Al2O3 catalyst with low Fe loading : effect of reaction temperature

- Muala, Guida, Iloy, R.A., Jalama, Kalala

Authors: Muala, Guida , Iloy, R.A. , Jalama, Kalala
Date: 2017
Subjects: Fe/Al2O3 catalyst , Fischer-Tropsch , Reaction temperature
Language: English
Type: Conference proceedings
Identifier: http://hdl.handle.net/10210/240308 , uj:24721 , Citation: Muala, G., Iloy, R.A. & Jalama, K. 2017. Fischer-Tropsch Synthesis over Fe/Al2O3 catalyst with low Fe loading : effect of reaction temperature.
Description: Abstract: The aim of this study was to investigate the effect of the operating temperature on the performance of a Fe/Al2O3 catalyst with low Fe loading during Fischer-Tropsch reaction. The catalyst was prepared by incipient wetness impregnation method and evaluated at 250 – 300 oC. The experimental results show that both selectivity and catalyst activity are strongly affected by the operating temperature. Increasing the temperature leads to increased catalytic activity and shifts the selectivity of products towards lighter hydrocarbons. While a clear dependence of the olefin-to-paraffin ratio (O/P) for C4 and C5 hydrocarbons on the operating temperature was not obtained, the O/P for C2 and C3 hydrocarbons was found to decrease with an increasing temperature.
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Fischer-Tropsch Synthesis over Unpromoted Co/ɣ-Al2O3 Catalyst: Effect of Activation with CO Compared to H2 on Catalyst Performance

- Khangale, Phathutshedzo R., Meijboom, Reinout, Jalama, Kalala

Authors: Khangale, Phathutshedzo R. , Meijboom, Reinout , Jalama, Kalala
Date: 2019
Subjects: Co/Al2O3 catalyst , Fischer-Tropsch , Activation with CO.
Language: English
Type: Article
Identifier: http://hdl.handle.net/10210/290088 , uj:31486 , Citation: Khangale, P.R., Meijboom, R. & Jalama, K. 2019. Fischer-Tropsch Synthesis over Unpromoted Co/ɣ-Al2O3 Catalyst: Effect of Activation with CO Compared to H2 on Catalyst Performance.
Description: Abstract: The effect of activating Co/Al2O3 catalyst by diluted CO or H2 on catalyst performance for FischerTropsch reaction was investigated. The catalyst was prepared by incipient wetness impregnation of the support and characterized using BET N2 physisorption, SEM, and XRD analyses. The reduction behavior of the catalyst in presence of CO and H2 individually was evaluated using TPR analyses. The data reveal that CO activates Co/Al2O3 catalyst at a lower temperature than H2 and produces a catalyst with higher rate for liquid product formation. It also leads to higher methane selectivity probably due to some cobalt carbide formation.
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