Experimental studies of adsorption from solution of the large aromatic molecules 1,2dihydroxybenz... more Experimental studies of adsorption from solution of the large aromatic molecules 1,2dihydroxybenzene (catechol) and phenyl hydroquinone on graphene nanoplatelets show that at low coverage adsorption is followed by a transition which occurs from adsorbed molecules in flat to more vertically oriented states. Catechol adsorption isotherms exhibit 2 plateaus while phenyl hydroquinone shows 3 plateaus indicating 2 and 3 active conformers respectively participating in the adsorption process. Modelling such adsorption isotherms presents a challenge. Here, an exact matrix treatment of the statistical mechanics of a one-dimensional model of adsorption of catechol and dihydroquinone on graphene nanoplatelets is presented. The theoretical adsorption isotherms successfully reproduce all the features of both the catechol and dihydroquinone experimental adsorption isotherms. As suggested by the experimentalists, our theoretical model demonstrates that adsorbed phenyl hydroquinone molecules adopt a flat orientation at low concentrations and an edge orientation at higher coverage before eventually adopting a vertical configuration. Both catechol and phenyl hydroquinone can be described by our interconvertible monomer-dimer-trimer model. The theoretical adsorption isotherms obtained show several plateaus reflecting the types of conformer on the graphene surface.
International Journal of Hydrogen Energy, Mar 1, 2017
The solid polymer electrolyte (SPE) alkaline anion exchange membrane (AAEM) fuel cell exhibits fa... more The solid polymer electrolyte (SPE) alkaline anion exchange membrane (AAEM) fuel cell exhibits facile oxygen reduction reaction (ORR) kinetics and has the ability to utilise nonprecious metal electrocatalysts. However, the AAEM is reported to suffer from increased instability within the alkaline media (degradation) via a number of routes, including nucleophilic elimination when operated at temperatures above 60ï‚°C, somewhat eliminating the kinetic advantage of operating at higher temperatures. Nonetheless, modelling studies have indicated that the membrane hydration could show improved resistance to alkaline instability and subsequent degradation when operated at elevated temperatures. This investigation uses the quartz crystal microbalance (QCM) to examine the thermal stability of a commercial AAEM as a function of humidity. The results show that hydration improves ionomer resistance to degradation, as the ions within the system (namely the OH -nucleophile and cationic headgroups) become less reactive. In-line mass spectrometry data confirms that the ionomer degrades during the elevated temperature excursions used in this study.
Water uptake, sorption mechanics and swelling characteristics of thin-film Nafion and a commercia... more Water uptake, sorption mechanics and swelling characteristics of thin-film Nafion and a commercially available Tokuyama alkaline anion exchange membrane ionomer from the vapour phase is explored using a quartz crystal microbalance (QCM). The water uptake measures the number of water molecules adsorbed by the ionomer per functional group and is determined in-situ using the QCM frequency responses allowing for comparison with nanogram precision. Crystal admittance spectroscopy, along with equivalent circuit fitting, is applied to both thin films for the first time and is used to investigate the ionomer's viscoelastic changes during hydration; to elucidate the mechanisms at play during low, medium and high relative humidities.
International Journal of Hydrogen Energy, Sep 1, 2017
Membrane hydration shown to affect AAEM interaction with CO2 Increasing hydration results in grea... more Membrane hydration shown to affect AAEM interaction with CO2 Increasing hydration results in greater loss of membrane conductivity. Pore opening and pore swelling have different regimes of CO2 interaction. Opening of membrane pore network leads to increasing CO2 uptake.
Journal of Analytical and Applied Pyrolysis, Aug 1, 2019
Coke related catalyst deactivation is still attractive for many researchers as the complexity of ... more Coke related catalyst deactivation is still attractive for many researchers as the complexity of carbon precursor. Y-zeolite is one of the most popular catalyst used in petrochemical industry, which is also progressively degrading by coking. In this piece of work, the effects of volatilization/decomposition temperature and sample-to-catalyst ratio on the coke formed from heavy oil volatilization/decomposition in the presence of Y-zeolite catalyst have been investigated. Temperature plays a significant role in determining the nature of the carbon formed, with higher temperatures favouring a higher graphitic-to-amorphous carbon ratio. Higher sample-to-catalyst ratios lead to higher amounts of coke, but does not affect the graphitic-to-amorphous carbon ratio as the same volatilization/decomposition temperature.
Energy generation and platform chemicals production from biomass are a potential route towards an... more Energy generation and platform chemicals production from biomass are a potential route towards an oil-free economy. Pyrolysis is one of the key technologies for transforming biomass into both fuels and chemicals. However, pyrolysis is a complex and energy-intensive process, and optimizing the operation for reducing its energy requirements is critical for the design of competitive biorefineries. This work presents a model to describe cellulose pyrolysis based on mass, energy and momentum conservation of solid and gaseous species. Lumped and detailed kinetic models are used to investigate how heating conditions impact pyrolysis product distribution. The resulting complex system was solved using gPROMS. Results suggest that pyrolysis mainly occurs in the boundary of the modelled particles. The developed model presents flexibility to use lumped and detailed kinetic models and provided both a general perspective of the pyrolysis process and detailed information on product distribution. Using this model, the results show that an initial high heating rate, followed by a lower heating rate, could reduce energy requirements by 10 % without changing the product distribution. There is also a trade-off between the yield of high added-value products, such as levoglucosan, and the overall energy requirement.
The co-gasification of beech-wood and polyethylene has been investigated in a lab-scale fluidised... more The co-gasification of beech-wood and polyethylene has been investigated in a lab-scale fluidised-bed reactor in the presence of four different types of bed materials (silica sand, olivine, Na-Y zeolite and ZSM-5 zeolite). ZSM-5 zeolite is very effective as a catalytic bed material in fluidized-bed reactor for wood-only gasification and co-gasification in terms of high hydrogen production and CGE. Na-Y zeolite is more effective compared with ZSM-5 zeolite in co-gasification of the beech-wood and polyethylene process. The catalytic activity in co-gasification of beech-wood and polyethylene can be ranked accordingly: Na-Y zeolite > ZSM-5 zeolite > olivine. In general, higher amounts of steam injected in the fluidized-bed reactor and more polyethylene would lead to higher hydrogen production in the cogasification process.
Biomass pyrolysis is a promising technology for fuel and chemical production from an abundant ren... more Biomass pyrolysis is a promising technology for fuel and chemical production from an abundant renewable source. It takes place usually in two stages; non-catalytic pyrolysis with further catalytic upgrading of the formed pyrolysis oil. The direct catalytic pyrolysis of biomass reduces the pyrolysis temperature, increase the yield to target products and improves their quality. However, in such one-stage process the contact between biomass and solid catalyst particles is poor leading to an excessively high degree of pure thermal pyrolysis reactions. The aim of this study was to enhance the catalyst-biomass contact via co-pressing of biomass and catalyst particles as a pre-treatment method. Catalytic pyrolysis of biomass components with HY and USY zeolites was studied using thermogravimetric analysis (TGA), as well as experiments in a pyrolysis reactor. The liquid and coke yields were characterized using gas chromatography, and TGA respectively. The TGA results showed that the degradation of the co-pressed cellulose occurred at lower temperatures compared to the pure thermal degradation, as well as catalytic degradation of non-pretreated cellulose. All biomass components produced better results using the co-pressing method, where the liquid yields increased while coke/char yields decreased. Bio-oil from catalytic pyrolysis of cellulose with HY catalyst mainly produced heavier fractions, while in the presence of USY catalyst medium fraction was mainly produced within the gasoline range. For hemicellulose catalytic pyrolysis, the catalysts had similar effects in enhancing the lighter fraction, but specifically, HY showed higher selectivity to middle fraction while USY has produced higher percentage of lighter fraction. Using with both catalysts, co-pressing had the best effect of eliminating the heavier fraction and improving the gasoline range fraction. Spent catalyst from co-pressed sample had lower concentrations of coke/char components due to the shorter residence times of volatiles, which suppresses the occurrence of secondary reactions leading to coke/char formations.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Plastic plays an important role in our daily lives due to its versatility, light weight and low p... more Plastic plays an important role in our daily lives due to its versatility, light weight and low production cost. Plastics became essential in many sectors such as construction, medical, engineering applications, automotive, aerospace, etc. In addition, economic growth and development also increased our demand and dependency on plastics which leads to its accumulation in landfills imposing risk on human health, animals and cause environmental pollution problems such as ground water contamination, sanitary related issues, etc. Hence, a sustainable and an efficient plastic waste treatment is essential to avoid such issues. Pyrolysis is a thermo-chemical plastic waste treatment technique which can solve such pollution problems, as well as, recover valuable energy and products such as oil and gas. Pyrolysis of plastic solid waste (PSW) has gained importance due to having better advantages towards environmental pollution and reduction of carbon footprint of plastic products by minimizing the emissions of carbon monoxide and carbon dioxide compared to combustion and gasification. This paper presents the existing techniques of pyrolysis, the parameters which affect the products yield and selectivity and identify major research gaps in this technology. The influence of different catalysts on the process as well as review and comparative assessment of pyrolysis with other thermal and catalytic plastic treatment methods, is also presented.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In response to the growing trend of greenhouse gas emissions from the production and use of conve... more In response to the growing trend of greenhouse gas emissions from the production and use of conventional fuels, COx free hydrogen generation is introduced as an alternative and efficient energy carrier. Due to hydrogen's storage challenges, is more efficient to be produced on-site by other chemical compounds for fuel cell applications. This work outlines the production of hydrogen (H2) from ammonia (NH3) and hydrous hydrazine (N2H4.H2O) catalytic decomposition. Both of these substances are giving nitrogen (N2) as a by-product, which is not toxic. Moreover, heterogeneous catalysts that were studied through the years are presented. Lastly, a reactoristic view of the ammonia decomposition is provided with different reactors such as catalytic membrane reactors (CMRs), fixed-bed reactors (FBRs) and micro-reactors (MRs) for the evaluation of their performance.
Thermo-chemical conversion of carbonaceous wastes such as tyres, plastics, biomass and crude glyc... more Thermo-chemical conversion of carbonaceous wastes such as tyres, plastics, biomass and crude glycerol is a promising technology compared to traditional waste treatment options (e.g. incineration and landfill). The process promotes the sustainable management of carbonaceous wastes and realizes the potential value of these wastes. Carbon nanotubes (CNTs) are one of the most extensively investigated and high-value materials due to their featured electrical, mechanical and physical properties. Producing CNTs from waste materials could solve the issues of waste management and simultaneously bring down the cost of CNT production. This review focuses on the four most abundant waste carbonaceous materials (waste tyres, plastics, biomass and crude glycerol) which have great potential to be alternative feedstocks for CNT production. The review considers the background of these four major types of waste to highlight the incentives in using thermo-chemical conversion to deal with these waste materials. Catalyst development for thermo-chemical conversion is discussed to summarize the most common catalysts and provide guidance for future novel catalyst improvement. Current research studies regarding CNT and hydrogen production from waste materials have been reviewed which show that the topic is highly attractive for researchers. The applications of CNTs have also been grouped based on different properties, aiming to guide the future research to explore the potential applications of CNTs synthesized from wastes. This review provides an overview of the recent developments in this research area and stimulates research to promote the deployment of the technology.
Plastics are abundant and have a high energy content making their use in energy applications attr... more Plastics are abundant and have a high energy content making their use in energy applications attractive. This article presents a review on plastic waste (PW) management by pyrolysis and gasification, which are two routes of thermochemical conversion (TCC) techniques. The conversion of PW and the application of its converted products are important steps towards reducing reliance on fossil fuel, enhancing closed-loop recycling of materials and circular economy. The review presented herein also focuses on product distribution and yields with emphasis on the energy content and potential integration to energy systems and grids. It is found that pyro-oils have properties similar to conventional fuels such as diesel and can partially substitute fossil fuels. In fact, the energy content of PW pyro-oils obtained by various researchers range from 41.10-46.16 MJ kg-1 , which are close to the heating values of conventional fuels, thus are potential candidates for fuel applications. Typical treatment post conversion is also conducted to maintain the quality of the oil produced and the removal of sulphur content to conform with market standards. On the other hand, syngas produced during gasification possesses a lesser potential for fuel applications as its energy content may reach values as low as 20 MJ kg-1 in
The effect of pre-degradation treatment in catalytic pyrolysis of polymer was assessed using ther... more The effect of pre-degradation treatment in catalytic pyrolysis of polymer was assessed using thermogravimetric analysis (TGA) and pyrolysis reactor experiments of different polymers on various catalysts. Intimate contact between the polymer and catalyst was achieved using physical, mechanical and thermal treatments. The results from the TGA analysis show that pre-degradation treatment has greatly improved the performance of the catalyst attaining maximum degradation at lower temperature. Pre-degradation treatment had increased the liquid yield and lowered the coke yield at various extents depending on the catalyst structure and acidity. The ZSM-5 catalyst with high Si/Al ratio showed maximum amount of (C5-C9) and ZSM-5 with lower Si/Al ratio has maximum percentage of (C14-C20). Based on the performance of the pre-degradation treatment methods, normal mixing produced the maximum amount of lighter fractions and therefore predegradation treatment can serve to enhance the gasoline fraction while the diesel fraction can be optimised using the co-pressing method, where polymer and catalyst particles were thoroughly mixed and co-pressed together into mixed particles. Coke characterisation showed coke formed by linear low density polyethylene contained more volatile coke components while polypropylene coke had higher percentage of hard coke. ZSM-5 had lower retention of coke components with volatile coke precursors. The volatility of the coke increases while coke concentration and decreases as the catalyst amount decreases. Pre-degradation treatment facilitated the formation of soft coke components that are easy to remove in inert atmosphere.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Coke formation from heavy oil cracking and the associated change in the porous structure of fluid... more Coke formation from heavy oil cracking and the associated change in the porous structure of fluid catalytic cracking (FCC) catalysts has been studied using a comprehensive range of techniques, including 2D and 3D imaging and carbon/coke characterization techniques. The carbon/coke formed from heavy oil devolatilization has been investigated with a range of oilto-FCC catalyst ratios (1:3, 1:2, 1:1, 2:1 and 3:1) to simulate the ageing of FCC catalysts in an operating oil refinery. Carbon/coke was formed on all used FCC catalyst samples and was found to generally increase in quantity with the increasing oil-to-FCC catalyst ratios. Coke formation has been correlated with the observed porosity change of the FCC catalyst. Higher quantities of carbon/coke formed on the FCC catalyst due to higher oil-to-FCC catalyst ratios (simulated increase in time on-stream) leads to a decrease of total pore volume and surface area. X-Ray computed tomography (X-Ray CT) studies allowed 3-dimensional imaging of used catalyst particles and showed that the zeolite component of the FCC catalyst remains evenly distributed throughout the FCC particle from the centre to the exterior for pristine and used FCC catalyst particles. This technique showed that while the interior porous structure of the FCC catalyst particle is not affected by the coking, the exterior porous structure is substantially modified for all used FCC catalyst samples. This process of pore collapse and/or clogging at the surface of the particles is likely to have a significant effect on the deactivation of FCC catalysts that is commonly observed. The deeper insight into this process gained through this study is important for understanding how FCC catalysts change with time-onstream and eventually deactivate and may allow for future catalysts to be developed that are more resistant to deactivation.
Experimental studies of adsorption from solution of the large aromatic molecules 1,2dihydroxybenz... more Experimental studies of adsorption from solution of the large aromatic molecules 1,2dihydroxybenzene (catechol) and phenyl hydroquinone on graphene nanoplatelets show that at low coverage adsorption is followed by a transition which occurs from adsorbed molecules in flat to more vertically oriented states. Catechol adsorption isotherms exhibit 2 plateaus while phenyl hydroquinone shows 3 plateaus indicating 2 and 3 active conformers respectively participating in the adsorption process. Modelling such adsorption isotherms presents a challenge. Here, an exact matrix treatment of the statistical mechanics of a one-dimensional model of adsorption of catechol and dihydroquinone on graphene nanoplatelets is presented. The theoretical adsorption isotherms successfully reproduce all the features of both the catechol and dihydroquinone experimental adsorption isotherms. As suggested by the experimentalists, our theoretical model demonstrates that adsorbed phenyl hydroquinone molecules adopt a flat orientation at low concentrations and an edge orientation at higher coverage before eventually adopting a vertical configuration. Both catechol and phenyl hydroquinone can be described by our interconvertible monomer-dimer-trimer model. The theoretical adsorption isotherms obtained show several plateaus reflecting the types of conformer on the graphene surface.
International Journal of Hydrogen Energy, Mar 1, 2017
The solid polymer electrolyte (SPE) alkaline anion exchange membrane (AAEM) fuel cell exhibits fa... more The solid polymer electrolyte (SPE) alkaline anion exchange membrane (AAEM) fuel cell exhibits facile oxygen reduction reaction (ORR) kinetics and has the ability to utilise nonprecious metal electrocatalysts. However, the AAEM is reported to suffer from increased instability within the alkaline media (degradation) via a number of routes, including nucleophilic elimination when operated at temperatures above 60ï‚°C, somewhat eliminating the kinetic advantage of operating at higher temperatures. Nonetheless, modelling studies have indicated that the membrane hydration could show improved resistance to alkaline instability and subsequent degradation when operated at elevated temperatures. This investigation uses the quartz crystal microbalance (QCM) to examine the thermal stability of a commercial AAEM as a function of humidity. The results show that hydration improves ionomer resistance to degradation, as the ions within the system (namely the OH -nucleophile and cationic headgroups) become less reactive. In-line mass spectrometry data confirms that the ionomer degrades during the elevated temperature excursions used in this study.
Water uptake, sorption mechanics and swelling characteristics of thin-film Nafion and a commercia... more Water uptake, sorption mechanics and swelling characteristics of thin-film Nafion and a commercially available Tokuyama alkaline anion exchange membrane ionomer from the vapour phase is explored using a quartz crystal microbalance (QCM). The water uptake measures the number of water molecules adsorbed by the ionomer per functional group and is determined in-situ using the QCM frequency responses allowing for comparison with nanogram precision. Crystal admittance spectroscopy, along with equivalent circuit fitting, is applied to both thin films for the first time and is used to investigate the ionomer's viscoelastic changes during hydration; to elucidate the mechanisms at play during low, medium and high relative humidities.
International Journal of Hydrogen Energy, Sep 1, 2017
Membrane hydration shown to affect AAEM interaction with CO2 Increasing hydration results in grea... more Membrane hydration shown to affect AAEM interaction with CO2 Increasing hydration results in greater loss of membrane conductivity. Pore opening and pore swelling have different regimes of CO2 interaction. Opening of membrane pore network leads to increasing CO2 uptake.
Journal of Analytical and Applied Pyrolysis, Aug 1, 2019
Coke related catalyst deactivation is still attractive for many researchers as the complexity of ... more Coke related catalyst deactivation is still attractive for many researchers as the complexity of carbon precursor. Y-zeolite is one of the most popular catalyst used in petrochemical industry, which is also progressively degrading by coking. In this piece of work, the effects of volatilization/decomposition temperature and sample-to-catalyst ratio on the coke formed from heavy oil volatilization/decomposition in the presence of Y-zeolite catalyst have been investigated. Temperature plays a significant role in determining the nature of the carbon formed, with higher temperatures favouring a higher graphitic-to-amorphous carbon ratio. Higher sample-to-catalyst ratios lead to higher amounts of coke, but does not affect the graphitic-to-amorphous carbon ratio as the same volatilization/decomposition temperature.
Energy generation and platform chemicals production from biomass are a potential route towards an... more Energy generation and platform chemicals production from biomass are a potential route towards an oil-free economy. Pyrolysis is one of the key technologies for transforming biomass into both fuels and chemicals. However, pyrolysis is a complex and energy-intensive process, and optimizing the operation for reducing its energy requirements is critical for the design of competitive biorefineries. This work presents a model to describe cellulose pyrolysis based on mass, energy and momentum conservation of solid and gaseous species. Lumped and detailed kinetic models are used to investigate how heating conditions impact pyrolysis product distribution. The resulting complex system was solved using gPROMS. Results suggest that pyrolysis mainly occurs in the boundary of the modelled particles. The developed model presents flexibility to use lumped and detailed kinetic models and provided both a general perspective of the pyrolysis process and detailed information on product distribution. Using this model, the results show that an initial high heating rate, followed by a lower heating rate, could reduce energy requirements by 10 % without changing the product distribution. There is also a trade-off between the yield of high added-value products, such as levoglucosan, and the overall energy requirement.
The co-gasification of beech-wood and polyethylene has been investigated in a lab-scale fluidised... more The co-gasification of beech-wood and polyethylene has been investigated in a lab-scale fluidised-bed reactor in the presence of four different types of bed materials (silica sand, olivine, Na-Y zeolite and ZSM-5 zeolite). ZSM-5 zeolite is very effective as a catalytic bed material in fluidized-bed reactor for wood-only gasification and co-gasification in terms of high hydrogen production and CGE. Na-Y zeolite is more effective compared with ZSM-5 zeolite in co-gasification of the beech-wood and polyethylene process. The catalytic activity in co-gasification of beech-wood and polyethylene can be ranked accordingly: Na-Y zeolite > ZSM-5 zeolite > olivine. In general, higher amounts of steam injected in the fluidized-bed reactor and more polyethylene would lead to higher hydrogen production in the cogasification process.
Biomass pyrolysis is a promising technology for fuel and chemical production from an abundant ren... more Biomass pyrolysis is a promising technology for fuel and chemical production from an abundant renewable source. It takes place usually in two stages; non-catalytic pyrolysis with further catalytic upgrading of the formed pyrolysis oil. The direct catalytic pyrolysis of biomass reduces the pyrolysis temperature, increase the yield to target products and improves their quality. However, in such one-stage process the contact between biomass and solid catalyst particles is poor leading to an excessively high degree of pure thermal pyrolysis reactions. The aim of this study was to enhance the catalyst-biomass contact via co-pressing of biomass and catalyst particles as a pre-treatment method. Catalytic pyrolysis of biomass components with HY and USY zeolites was studied using thermogravimetric analysis (TGA), as well as experiments in a pyrolysis reactor. The liquid and coke yields were characterized using gas chromatography, and TGA respectively. The TGA results showed that the degradation of the co-pressed cellulose occurred at lower temperatures compared to the pure thermal degradation, as well as catalytic degradation of non-pretreated cellulose. All biomass components produced better results using the co-pressing method, where the liquid yields increased while coke/char yields decreased. Bio-oil from catalytic pyrolysis of cellulose with HY catalyst mainly produced heavier fractions, while in the presence of USY catalyst medium fraction was mainly produced within the gasoline range. For hemicellulose catalytic pyrolysis, the catalysts had similar effects in enhancing the lighter fraction, but specifically, HY showed higher selectivity to middle fraction while USY has produced higher percentage of lighter fraction. Using with both catalysts, co-pressing had the best effect of eliminating the heavier fraction and improving the gasoline range fraction. Spent catalyst from co-pressed sample had lower concentrations of coke/char components due to the shorter residence times of volatiles, which suppresses the occurrence of secondary reactions leading to coke/char formations.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Plastic plays an important role in our daily lives due to its versatility, light weight and low p... more Plastic plays an important role in our daily lives due to its versatility, light weight and low production cost. Plastics became essential in many sectors such as construction, medical, engineering applications, automotive, aerospace, etc. In addition, economic growth and development also increased our demand and dependency on plastics which leads to its accumulation in landfills imposing risk on human health, animals and cause environmental pollution problems such as ground water contamination, sanitary related issues, etc. Hence, a sustainable and an efficient plastic waste treatment is essential to avoid such issues. Pyrolysis is a thermo-chemical plastic waste treatment technique which can solve such pollution problems, as well as, recover valuable energy and products such as oil and gas. Pyrolysis of plastic solid waste (PSW) has gained importance due to having better advantages towards environmental pollution and reduction of carbon footprint of plastic products by minimizing the emissions of carbon monoxide and carbon dioxide compared to combustion and gasification. This paper presents the existing techniques of pyrolysis, the parameters which affect the products yield and selectivity and identify major research gaps in this technology. The influence of different catalysts on the process as well as review and comparative assessment of pyrolysis with other thermal and catalytic plastic treatment methods, is also presented.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In response to the growing trend of greenhouse gas emissions from the production and use of conve... more In response to the growing trend of greenhouse gas emissions from the production and use of conventional fuels, COx free hydrogen generation is introduced as an alternative and efficient energy carrier. Due to hydrogen's storage challenges, is more efficient to be produced on-site by other chemical compounds for fuel cell applications. This work outlines the production of hydrogen (H2) from ammonia (NH3) and hydrous hydrazine (N2H4.H2O) catalytic decomposition. Both of these substances are giving nitrogen (N2) as a by-product, which is not toxic. Moreover, heterogeneous catalysts that were studied through the years are presented. Lastly, a reactoristic view of the ammonia decomposition is provided with different reactors such as catalytic membrane reactors (CMRs), fixed-bed reactors (FBRs) and micro-reactors (MRs) for the evaluation of their performance.
Thermo-chemical conversion of carbonaceous wastes such as tyres, plastics, biomass and crude glyc... more Thermo-chemical conversion of carbonaceous wastes such as tyres, plastics, biomass and crude glycerol is a promising technology compared to traditional waste treatment options (e.g. incineration and landfill). The process promotes the sustainable management of carbonaceous wastes and realizes the potential value of these wastes. Carbon nanotubes (CNTs) are one of the most extensively investigated and high-value materials due to their featured electrical, mechanical and physical properties. Producing CNTs from waste materials could solve the issues of waste management and simultaneously bring down the cost of CNT production. This review focuses on the four most abundant waste carbonaceous materials (waste tyres, plastics, biomass and crude glycerol) which have great potential to be alternative feedstocks for CNT production. The review considers the background of these four major types of waste to highlight the incentives in using thermo-chemical conversion to deal with these waste materials. Catalyst development for thermo-chemical conversion is discussed to summarize the most common catalysts and provide guidance for future novel catalyst improvement. Current research studies regarding CNT and hydrogen production from waste materials have been reviewed which show that the topic is highly attractive for researchers. The applications of CNTs have also been grouped based on different properties, aiming to guide the future research to explore the potential applications of CNTs synthesized from wastes. This review provides an overview of the recent developments in this research area and stimulates research to promote the deployment of the technology.
Plastics are abundant and have a high energy content making their use in energy applications attr... more Plastics are abundant and have a high energy content making their use in energy applications attractive. This article presents a review on plastic waste (PW) management by pyrolysis and gasification, which are two routes of thermochemical conversion (TCC) techniques. The conversion of PW and the application of its converted products are important steps towards reducing reliance on fossil fuel, enhancing closed-loop recycling of materials and circular economy. The review presented herein also focuses on product distribution and yields with emphasis on the energy content and potential integration to energy systems and grids. It is found that pyro-oils have properties similar to conventional fuels such as diesel and can partially substitute fossil fuels. In fact, the energy content of PW pyro-oils obtained by various researchers range from 41.10-46.16 MJ kg-1 , which are close to the heating values of conventional fuels, thus are potential candidates for fuel applications. Typical treatment post conversion is also conducted to maintain the quality of the oil produced and the removal of sulphur content to conform with market standards. On the other hand, syngas produced during gasification possesses a lesser potential for fuel applications as its energy content may reach values as low as 20 MJ kg-1 in
The effect of pre-degradation treatment in catalytic pyrolysis of polymer was assessed using ther... more The effect of pre-degradation treatment in catalytic pyrolysis of polymer was assessed using thermogravimetric analysis (TGA) and pyrolysis reactor experiments of different polymers on various catalysts. Intimate contact between the polymer and catalyst was achieved using physical, mechanical and thermal treatments. The results from the TGA analysis show that pre-degradation treatment has greatly improved the performance of the catalyst attaining maximum degradation at lower temperature. Pre-degradation treatment had increased the liquid yield and lowered the coke yield at various extents depending on the catalyst structure and acidity. The ZSM-5 catalyst with high Si/Al ratio showed maximum amount of (C5-C9) and ZSM-5 with lower Si/Al ratio has maximum percentage of (C14-C20). Based on the performance of the pre-degradation treatment methods, normal mixing produced the maximum amount of lighter fractions and therefore predegradation treatment can serve to enhance the gasoline fraction while the diesel fraction can be optimised using the co-pressing method, where polymer and catalyst particles were thoroughly mixed and co-pressed together into mixed particles. Coke characterisation showed coke formed by linear low density polyethylene contained more volatile coke components while polypropylene coke had higher percentage of hard coke. ZSM-5 had lower retention of coke components with volatile coke precursors. The volatility of the coke increases while coke concentration and decreases as the catalyst amount decreases. Pre-degradation treatment facilitated the formation of soft coke components that are easy to remove in inert atmosphere.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Coke formation from heavy oil cracking and the associated change in the porous structure of fluid... more Coke formation from heavy oil cracking and the associated change in the porous structure of fluid catalytic cracking (FCC) catalysts has been studied using a comprehensive range of techniques, including 2D and 3D imaging and carbon/coke characterization techniques. The carbon/coke formed from heavy oil devolatilization has been investigated with a range of oilto-FCC catalyst ratios (1:3, 1:2, 1:1, 2:1 and 3:1) to simulate the ageing of FCC catalysts in an operating oil refinery. Carbon/coke was formed on all used FCC catalyst samples and was found to generally increase in quantity with the increasing oil-to-FCC catalyst ratios. Coke formation has been correlated with the observed porosity change of the FCC catalyst. Higher quantities of carbon/coke formed on the FCC catalyst due to higher oil-to-FCC catalyst ratios (simulated increase in time on-stream) leads to a decrease of total pore volume and surface area. X-Ray computed tomography (X-Ray CT) studies allowed 3-dimensional imaging of used catalyst particles and showed that the zeolite component of the FCC catalyst remains evenly distributed throughout the FCC particle from the centre to the exterior for pristine and used FCC catalyst particles. This technique showed that while the interior porous structure of the FCC catalyst particle is not affected by the coking, the exterior porous structure is substantially modified for all used FCC catalyst samples. This process of pore collapse and/or clogging at the surface of the particles is likely to have a significant effect on the deactivation of FCC catalysts that is commonly observed. The deeper insight into this process gained through this study is important for understanding how FCC catalysts change with time-onstream and eventually deactivate and may allow for future catalysts to be developed that are more resistant to deactivation.
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