Article
Chemistry, Physical
Tshepo Molefe, Dean Barrett, Beatriz Diaz, Roy Forbes, Neil J. Coville
Summary: This study reports on the synthesis and application of osmium nanoparticles supported on and/or encapsulated in hollow carbon spheres for Fischer-Tropsch Synthesis (FTS). It is demonstrated that the interaction between osmium and cobalt has a significant effect on the catalyst activity when loaded together. Proximity of osmium and cobalt leads to higher FTS activity and C5+ production through the primary spillover effect. This study reveals the effect of osmium on FTS catalysts for the first time.
JOURNAL OF CATALYSIS
(2023)
Article
Chemistry, Physical
Jose G. Moya-Cancino, Ari-Pekka Honkanen, Ad M. J. van der Eerden, Ramon Oord, Matteo Monai, Iris ten Have, Christoph J. Sahle, Florian Meirer, Bert M. Weckhuysen, Frank M. F. de Groot, Simo Huotari
Summary: The study presents in situ experiments to investigate the formation of cobalt carbides during Fischer-Tropsch synthesis on a Co/TiO2 catalyst under relevant pressure and temperature conditions. X-ray Raman scattering (XRS) spectroscopy and X-ray diffraction (XRD) were used in combination to perform the experiments. The results indicate a change in the oxidation state of cobalt nanoparticles, leading to the formation of cobalt carbide (Co2C) during the FTS reaction.
Article
Chemistry, Applied
Prasad Gonugunta, A. Iulian Dugulan, G. Leendert Bezemer, Ekkes Bruck
Summary: Operando spectroscopic techniques were used to investigate the impact of oxygenates deposition on the deactivation of cobalt on titania Fischer-Tropsch catalysts under high pressure. It was found that catalysts prepared via impregnation had more and heavier carboxylates, likely due to higher olefin content in the products, leading to increased formation of oxygenates. Gas chromatography/infrared spectroscopy data indicated that the surface carboxylate species were not involved in catalyst deactivation, serving as spectator species on the titania support.
Review
Chemistry, Multidisciplinary
Yanping Chen, Jiatong Wei, Melis S. Duyar, Vitaly V. Ordomsky, Andrei Y. Khodakov, Jian Liu
Summary: This review summarizes the recent advances in the preparation of carbon-based catalysts for Fischer-Tropsch synthesis, highlighting the importance of support and metal properties, activity, product selectivity, and their interactions. Current challenges and future trends in the commercial utilization of carbon-based catalysts for FTS are also discussed.
CHEMICAL SOCIETY REVIEWS
(2021)
Article
Chemistry, Physical
Mikhail Shipilin, David Degerman, Patrick Lomker, Christopher M. Goodwin, Gabriel L. S. Rodrigues, Michael Wagsta, Joergen Gladh, Hsin-Yi Wang, Andreas Stierle, Christoph Schlueter, Lars G. M. Pettersson, Anders Nilsson, Peter Amann
Summary: In this study, the effect of pressure, temperature, time, and gas feed composition on the growth dynamics of iron-carbon phases was investigated. The details of iron surface carburization and product formation under realistic conditions were revealed using a combination of experimental and theoretical approaches. This research provides important insights into the relationship between the catalyst's surface and the reaction.
Article
Chemistry, Physical
Mikhail Shipilin, David Degerman, Patrick Loemker, Christopher M. Goodwin, Gabriel L. S. Rodrigues, Michael Wagstaffe, Jorgen Gladh, Hsin-Yi Wang, Andreas Stierle, Christoph Schlueter, Lars G. M. Pettersson, Anders Nilsson, Peter Amann
Summary: This study investigates the detailed mechanism of carbide formation on iron-based catalysts and the effect of reaction conditions on the catalyst surface state through experiments and theoretical calculations.
Article
Green & Sustainable Science & Technology
Higor A. Garona, Fabio M. Cavalcanti, Thiago F. de Abreu, Martin Schmal, Rita M. B. Alves
Summary: This study used Machine Learning models to predict optimal reaction conditions for Fischer-Tropsch Synthesis, showing the efficacy of neural networks in predicting key variables. In comparison to recent studies, this research included more variables in the model such as catalyst support, active phase, and promoters. The Fe-based catalyst showed the highest light olefins selectivity and yield at optimal conditions, despite emitting the most carbon dioxide.
JOURNAL OF CLEANER PRODUCTION
(2021)
Article
Chemistry, Physical
Erling Rytter, Anders Runningen, Edd Blekkan, Magne Hillestad
Summary: The paper presents the development of a mechanism and rate expression for Fischer-Tropsch synthesis over cobalt-based catalysts. The mechanism involves a two-step hydrogen assisted activation of CO and incorporates the influence of water partial pressure on the reaction rate. The resulting kinetic model is tested on various cobalt catalysts and accurately describes the observed CO conversions and selectivities.
MOLECULAR CATALYSIS
(2022)
Article
Nanoscience & Nanotechnology
Joakim Tafjord, Erling Rytter, Anders Holmen, Rune Myrstad, Ingeborg-Helene Svenum, Bjorn E. Christensen, Jia Yang
Summary: This study describes a method to synthesize transition-metal nanoparticles anchored on carbon supports using low-molar-mass sodium alginate, followed by a pyrolysis step. The resulting catalysts exhibit high metal loadings and activity, with pyrolyzed Fe-alginate showing particularly high Fischer-Tropsch synthesis activity.
ACS APPLIED NANO MATERIALS
(2021)
Article
Chemistry, Physical
Weizhen Li, Xuebing Zhang, Tao Wang, Xiaoyu Zhang, Linlin Wei, Quan Lin, Yijun Lv, Zhuowu Men
Summary: The performance of precipitated iron Fischer-Tropsch synthesis catalysts is significantly influenced by chlorine modification. The higher the chlorine content in the catalyst, the greater the deactivation.
Article
Chemistry, Physical
Luke M. van Koppen, A. Iulian Dugulan, G. Leendert Bezemer, Emiel J. M. Hensen
Summary: This study explored the role of manganese as a structural promoter on silica-supported cobalt nanoparticles under high CO conversion conditions. It was found that adding manganese oxide enhanced the dispersion of cobalt but resulted in cobalt silicate formation. Without manganese, the cobalt particles sintered and transformed into cobalt carbide.
JOURNAL OF CATALYSIS
(2023)
Article
Chemistry, Applied
Lilia Sineva, Ekaterina O. Gorokhova, Kirill O. Gryaznov, Ilya S. Ermolaev, Vladimir Z. Mordkovich
Summary: The use of zeolite-containing Co catalysts in liquid hydrocarbon transformations during Fischer-Tropsch synthesis demonstrated a decrease in the average molecular weight of the products without increasing methane selectivity. The introduction of zeolites cleared the catalyst pore system of heavier hydrocarbons, suggesting a potential role in controlling product composition over hybrid catalysts.
Article
Engineering, Chemical
Pengfei Lu, Jie Liang, Kangzhou Wang, Bo Liu, Thachapan Atchimarungsri, Yuan Wang, Xingjun Zhang, Jumei Tian, Yongjun Jiang, Zhihao Liu, Prasert Reubroycharoen, Tiansheng Zhao, Jianli Zhang, Xinhua Gao
Summary: Researchers reported a multifunctional catalyst for the hydrogenation of carbon dioxide to higher hydrocarbon. The optimized catalyst exhibited excellent selectivity and conversion, resulting in a significant production of higher hydrocarbon.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Chemistry, Multidisciplinary
Meng Cui, Qingli Qian, Jingjing Zhang, Ying Wang, Bernard Baffour Asare Bediako, Huizhen Liu, Buxing Han
Summary: The study presents the production of liquid fuel from CO2 hydrogenation by coupling homogeneous RuCl3 and heterogeneous Ru-0 catalysts at the lowest reported temperature (180 degrees C) and achieving the highest C5+ selectivity to date (71.1%). The synergy of homogeneous and heterogeneous catalysis is identified as the key factor for the outstanding performance.
Article
Energy & Fuels
Wenli Lu, Jungang Wang, Zhongyi Ma, Congbiao Chen, Yan Liu, Bo Hou, Debao Li, Baojun Wang
Summary: The role of carbon deposits during Fischer-Tropsch synthesis (FTS) on cobalt catalysts is still debated. This study investigates the effects of pre-deposited composite and single carbon on cobalt catalysts in FTS. Different types of carbon deposits (atomic carbon, polymeric carbon, graphitic carbon) are identified and characterized using TPH, Raman, and XPS. Results show that the presence of pre-deposited carbon significantly affects the catalytic activity, methane selectivity, and stability of the Co-based catalysts in FTS.
Article
Chemistry, Multidisciplinary
Pumza Mente, Victor Mashindi, Alice Magubane, Tumelo N. Phaahlamohlaka, Prakash M. Gangatharan, Roy P. Forbes, Neil J. Coville
Summary: A vapour phase flow system was used to study the hydrogenation of cinnamaldehyde using cobalt catalysts supported inside and outside hollow carbon spheres (HCSs). The results showed that the Co@HCS catalyst exhibited better conversion and product selectivity compared to the Co/HCS catalyst. Catalyst particle size and reaction temperature were found to affect the efficiency of the reaction.
CANADIAN JOURNAL OF CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Victor Mashindi, Pumza Mente, Tumelo N. Phaahlamohlaka, Nobuhle Mpofu, Ofentse A. Makgae, Beatriz D. Moreno, Dean H. Barrett, Roy P. Forbes, Pieter B. Levecque, Kenneth I. Ozoemena, Neil J. Coville
Summary: This study investigates the application of hollow carbon spheres as catalyst supports in oxygen reduction reactions. The new catalysts show high activity and excellent durability.
FRONTIERS IN CHEMISTRY
(2022)
Article
Engineering, Chemical
Chike George Okoye-Chine, Roy Forbes, Joshua Gorimbo, Mahluli Moyo, Xinying Liu, Diane Hildebrandt
Summary: The reduction pathway of Co catalysts supported on untreated SiO2 and two pretreated SiO2 support materials was investigated. The study revealed that ethylene glycol pretreated SiO2 supported Co catalyst showed smaller metal crystallites and highly dispersed Co, but had a low degree of reduction of CoO due to the strong Co-SiO2 interaction. In contrast, the annealing pretreated SiO2 supported Co catalyst exhibited better catalytic activity during FTS.
CHEMICAL ENGINEERING COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Ofentse A. Makgae, Arthur N. Moya, Tumelo N. Phaahlamohlaka, Chen Huang, Neil J. Coville, Angus Kirkland, Emanuela Liberti
Summary: In this study, the surface terminations of Co3O4 nanoparticles supported on hollow carbon spheres were directly observed using exit wavefunction reconstruction from aberration-corrected transmission electron microscopy. The surface {100}, {110}, and {111} facets of spinel Co3O4 were found to exhibit characteristic active sites for CO adsorption, with the {100} and {110} terminations being more suitable than {111}. However, the presence of oxygen on the {111} surface termination also indicates its essential role in CO adsorption.
Article
Chemistry, Physical
Ofentse A. Makgae, Tumelo N. Phaahlamohlaka, Benzhen Yao, Manfred E. Schuster, Thomas J. A. Slater, Peter P. Edwards, Neil J. Coville, Emanuela Liberti, Angus Kirkland
Summary: In this study, the effect of CO reduction to CO on the reducibility of Co3O4 nanoparticles supported on hollow carbon spheres was investigated using high-resolution aberration-corrected analytical electron microscopy. It was found that carbon encapsulation of twinned fcc Co particles occurred during the syngas treatment, while H2-treated particles mainly consisted of CoO. Additionally, the reducibility of Co3O4 nanoparticles was improved in syngas compared to H2 at 350°C. The study also explored the impact of high temperature on the reducibility of Co3O4 nanoparticles.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Materials Science, Multidisciplinary
Ludwe L. Sikeyi, Laercia R. Bila, Themba D. Ntuli, Cyril T. Selepe, Nobanathi W. Maxakato, Neil J. Coville, Manoko S. Maubane-Nkadimeng
Summary: This study presents the synthesis of Pt supported on titania oxide nanoparticles decorated on sulfur doped onion-like carbon nanoparticles (S-OLCNs) and their application as electrocatalysts for ammonia oxidation reactions. The incorporation of TiO2 nanoparticles into Pt/S-OLCN was found to significantly enhance the activity of Pt for the ammonia oxidation reaction by facilitating the electron transfer process. Pt/TiO2/S-OLCN also exhibited better long term stability and faster charge transfer resistance compared to other catalysts tested.
DIAMOND AND RELATED MATERIALS
(2023)
Article
Electrochemistry
B. Shaku, T. P. Mofokeng, N. J. Coville, K. I. Ozoemena, M. S. Maubane-Nkadimeng
Summary: This study presents the conversion of marula nutshell waste into nitrogen-doped activated carbon (N-ACs) for supercapacitor electrode material. The N-ACs demonstrated high surface area and porosity, resulting in excellent electrochemical performance in KOH and KNO3 electrolytes. The material achieved remarkable energy and power densities in 2.5 M KNO3 electrolyte, making it a promising energy storage material for supercapacitors.
ELECTROCHIMICA ACTA
(2023)
Article
Chemistry, Multidisciplinary
Ryan O'Connor, Joyce B. Matsoso, Victor Mashindi, Pumza Mente, Lebohang Macheli, Beatriz D. Moreno, Bryan P. Doyle, Neil J. Coville, Dean H. Barrett
Summary: In this study, the influence of counter anion on the structural properties of hollow carbon spheres (HCS) support was investigated. It was found that the thickness of the HCS shell depended on the type of nickel precursor salt used. The choice of precursor salt also affected the textural properties of the HCS nanosupports and influenced the growth of nickel nanoparticles.
Article
Materials Science, Multidisciplinary
Melisha Jivanji, Roy Peter Forbes, Humphrey Sithebe, Johan Ewald Westraadt
Summary: This study investigates the effect of ZrB2 additions on the microstructure, thermal stability, and thermo-mechanical wear resistance of polycrystalline diamond. The ZrB2-PCD material binder phase consisted of cobalt-boride phases. The ZrB2-PCD tools showed excellent thermo-mechanical wear resistance, but lowered abrasion wear resistance was observed during low-temperature wet-VTL testing.
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
(2023)
Review
Optics
Orlette Mkhari, Themba D. Ntuli, Neil J. Coville, Edward N. Nxumalo, Manoko S. Maubane-Nkadimeng
Summary: Carbon dot/support nanocomposites exhibit improved properties and hold great potential for applications in fields such as photocatalysis, electrochemistry, optics, and nanomedicine.
JOURNAL OF LUMINESCENCE
(2023)
Article
Chemistry, Physical
Djalila Guettaia, Hanane Zazoua, Mohammed Reda Ramdani, Khaldoun Bachari, Neil J. Coville, Amel Boudjemaa
Summary: This paper reports on the photodegradation of ibuprofen (IBP) using SiO2@xTiO(2) synthesized via a hydrothermal method. The catalysts were prepared by adding TiO2 to a Stober synthesized silica at different weight loadings. The SiO2@xTiO(2) showed excellent photodegradation efficiency and the degradation rate of IBP increased with the formation of H2O2.
REACTION KINETICS MECHANISMS AND CATALYSIS
(2023)
Article
Chemistry, Multidisciplinary
Themba D. Ntuli, Ludwe L. Sikeyi, Faria Dziike, Neil J. Coville, Edward N. Nxumalo, Manoko S. Maubane-Nkadimeng
Summary: Waste cooking oil was converted into onion-like nanocarbons (OLNCs) through flame pyrolysis and then combined with TiO2 to form TiO2/OLNC nanocomposites using hydrothermal treatment. The mass ratio of TiO2 to OLNCs was varied, while the mass of TiO2 was kept constant. The nanocomposites exhibited enhanced photocatalytic activity and degradation efficiency for methyl orange due to the high adsorption efficiency of OLNCs and the hindrance of electron-hole recombination.
APPLIED SCIENCES-BASEL
(2023)
Review
Chemistry, Physical
Lerato L. Mokoloko, Roy P. Forbes, Neil J. Coville
Summary: Since their discovery in 2004, carbon dots (CDs) have been widely used in various applications due to their fluorescent properties. However, the potential uses of CDs as catalysts and supports in catalytic reactions are still relatively unexplored. Studies have shown the advantages of using CDs in catalysis, but there are challenges associated with their stability and aggregation due to their small size.
Article
Chemistry, Multidisciplinary
Lerato L. Mokoloko, Joyce B. Matsoso, Nikolas Antonatos, Vlastimil Mazanek, Beatriz D. Moreno, Roy P. Forbes, Dean H. Barrett, Zdenek Sofer, Neil J. Coville
Summary: This study presents the application of N-doped carbon nanosheets for room temperature chemoresistive detection of methanol and ethanol. The nanosheets were made by heat treatment of N-doped carbon dots and showed good sensitivity and low detection limits for both alcohols. The composite nature and large basal area of the nanosheets facilitated easy adsorption of the analyte molecules.
Article
Chemistry, Multidisciplinary
Thomas H. Mongwe, Themba D. Ntuli, Ludwe L. Sikeyi, Neil J. Coville, Messai A. Mamo, Jose P. M. Serbena, Manoko S. Maubane-Nkadimeng
Summary: This study reports on the synthesis of carbon nano-onions and nitrogen-doped carbon nano-onions, and their application in gas sensing materials. The results showed that the composite based on pristine CNOs exhibited higher sensitivity to acetone, while the sensor based on N-CNOs had a lower limit of detection.
SOUTH AFRICAN JOURNAL OF CHEMISTRY-SUID-AFRIKAANSE TYDSKRIF VIR CHEMIE
(2022)
