Showing papers by "Jason P. Hallett published in 2018"

Carbon capture and storage (CCS): the way forward

Abstract: Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

Green and Sustainable Solvents in Chemical Processes

Abstract: Sustainable solvents are a topic of growing interest in both the research community and the chemical industry due to a growing awareness of the impact of solvents on pollution, energy usage, and contributions to air quality and climate change. Solvent losses represent a major portion of organic pollution, and solvent removal represents a large proportion of process energy consumption. To counter these issues, a range of greener or more sustainable solvents have been proposed and developed over the past three decades. Much of the focus has been on the environmental credentials of the solvent itself, although how a substance is deployed is as important to sustainability as what it is made from. In this Review, we consider several aspects of the most prominent sustainable organic solvents in use today, ionic liquids, deep eutectic solvents, supercritical fluids, switchable solvents, liquid polymers, and renewable solvents. We examine not only the performance of each class of solvent within the context of the...

Non-aqueous homogenous biocatalytic conversion of polysaccharides in ionic liquids using chemically modified glucosidase

Abstract: The increasing requirement to produce platform chemicals and fuels from renewable sources means advances in biocatalysis are rapidly becoming a necessity. Biomass is widely used in nature as a source of energy and as chemical building blocks. However, recalcitrance towards traditional chemical processes and solvents provides a significant barrier to widespread utility. Here, by optimizing enzyme solubility in ionic liquids, we have discovered solvent-induced substrate promiscuity of glucosidase, demonstrating an unprecedented example of homogeneous enzyme bioprocessing of cellulose. Specifically, chemical modification of glucosidase for solubilization in ionic liquids can increase thermal stability to up to 137 °C, allowing for enzymatic activity 30 times greater than is possible in aqueous media. These results establish that through a synergistic combination of chemical biology (enzyme modification) and reaction engineering (solvent choice), the biocatalytic capability of enzymes can be intensified: a key step towards the full-scale deployment of industrial biocatalysis.

Pretreatment of South African sugarcane bagasse using a low-cost protic ionic liquid: a comparison of whole, depithed, fibrous and pith bagasse fractions.

Abstract: Sugarcane bagasse is an abundant and geographically widespread agro-industrial residue with high carbohydrate content, making it a strong candidate feedstock for the bio-based economy. This study examines the use of the low-cost protic ionic liquid triethylammonium hydrogen sulfate ([TEA][HSO4]) to fractionate a range of South African sugarcane bagasse preparations into a cellulose-rich pulp and lignin. The study seeks to optimize pretreatment conditions and examine the necessity of applying a depithing step on bagasse prior to pretreatment. Pretreatment of five bagasse preparations, namely whole, industrially depithed, laboratory depithed (short and long fiber) and pith bagasse with [TEA][HSO4]:[H2O] (4:1 w/w) solutions produced highly digestible cellulose-rich pulps, as assessed by residual lignin analysis and enzymatic hydrolysis. Pretreatment under the optimized condition of 120 °C for 4 h produced a pretreated cellulose pulp with up to 90% of the lignin removed and enabled the release of up to 69% glucose contained in the bagasse via enzymatic hydrolysis. Glucose yields from whole and depithed bagasse preparations were very similar. Significant differences in lignin recovery were obtained for laboratory depithed bagasse compared with whole and industrially depithed bagasse. The silica-rich ash components of bagasse were seen to partition mainly with the pulp, from where they could be easily recovered in the post-hydrolysis solids. The five bagasse preparations were compared but did not show substantial differences in composition or cellulose digestibility after pretreatment. Evidence was presented that a depithing step appears to be unnecessary prior to ionoSolv fractionation, potentially affording significant cost and energy savings. Instead, lignin re-deposition onto the pulp surface (and, in turn, particle size and shape) appeared to be major factors affecting the conditioning of bagasse with the applied IL. We show that pith bagasse, a common by-product of paper making, can be successfully conditioned for high glucose release while allowing recovery of lignin and silica-rich ash. The glucose yields obtained for bagasse using [TEA][HSO4]-water mixtures were ~ 75% as high as for conventional aprotic ionic liquids such as [Emim][OAc]; this result is highly promising for commercialization of ionoSolv processing given [TEA][HSO4] is 40 times less expensive, thermally stable and recyclable.

Challenges and opportunities for the utilisation of ionic liquids as solvents for CO2 capture

Abstract: Ionic liquids have been extensively investigated as promising materials for several gas separation processes, including CO2 capture. They have the potential to outperform traditional solvents, in terms of their capacity, selectivity, regenerability and stability. In fact, hundreds of ionic liquids have been investigated as potential sorbents for CO2 capture. However, most studies focus on enhancing equilibrium capacity, and neglect to consider other properties, such as transport properties, and hence ignore the effect that the overall set of properties have on process performance, and therefore on cost. In this study, we propose a new methodology for their evaluation using a range of monetised and non-monetised process performance indices. Our results demonstrate that whilst most research effort is focused on improving CO2 solubility, viscosity, a transport property, and heat capacity, a thermochemical property, might preclude the use of ionic liquids, even those which are highly CO2-philic, and therefore increased effort on addressing the challenges associated with heat capacity and viscosity is an urgent necessity. This work highlights a range of potential challenges that ionic liquids will face before they can be applied at process scale, and identifies some key research opportunities.

Lead acid battery recycling for the twenty-first century

Abstract: There is a growing need to develop novel processes to recover lead from end-of-life lead-acid batteries, due to increasing energy costs of pyrometallurgical lead recovery, the resulting CO2 emissions and the catastrophic health implications of lead exposure from lead-to-air emissions. To address these issues, we are developing an iono-metallurgical process, aiming to displace the pyrometallurgical process that has dominated lead production for millennia. The proposed process involves the dissolution of Pb salts into the deep eutectic solvent (DES) Ethaline 200, a liquid formed when a 1 : 2 molar ratio of choline chloride and ethylene glycol are mixed together. Once dissolved, the Pb can be recovered through electrodeposition and the liquid can then be recycled for further Pb recycling. Firstly, DESs are being used to dissolve the lead compounds (PbCO3, PbO, PbO2 and PbSO4) involved and their solubilities measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The resulting Pb2+ species are then reduced and electrodeposited as elemental lead at the cathode of an electrochemical cell; cyclic voltammetry and chronoamperometry are being used to determine the electrodeposition behaviour and mechanism. The electrodeposited films were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We discuss the implications and opportunities of such processes.

Use of ionic liquids to minimize sodium induced internal diesel injector deposits (IDIDs)

Abstract: Trace amounts of dissolved sodium has been identified as one possible cause leading to the formation of internal diesel injector deposits (IDIDs) which prove problematic by reducing fuel efficiency in high pressure diesel injectors. We demonstrate the successful extraction of ppm levels of Na+ from a model diesel fuel. A range of ionic liquids (ILs) with a variety of cations and anions were examined for their effectiveness at different loadings of IL relative to the model diesel fuel. Results provide several clear trends with some exceptional capabilities of the ILs in the extractions. ILs are commonly referred to as ‘designer solvents’, due to the great degree of fine-tuning of physical and chemical properties afforded by modification of the constituent cation and anion. The tunable properties of the ILs ions allow the ‘design’ to meet the requirements for a particular target and here provide several potential candidates for the extraction of the ppm levels of sodium from diesel fuel. We report for the first time that ILs can extract up to 99.1% of Na+ from a model diesel fuel at a Na+ concentration of just 3 mg kg−1 in the fuel; factors affecting the extent of extraction were investigated via correlation with experimental solvent descriptors. 23Na NMR was used in the determination of donor number (DN), and Kamlet–Taft parameters were gathered for each IL providing information of possible hydrogen-bond acidity/basicity (α/β) and dipolarity/polarizability solvent strength (π*). In addition, the non-random two liquid model (NRTL) was applied to correlate the experimental extraction results and determine τ parameters for each of the ILs. We determined that the extraction is controlled strongly by the Lewis basicity of the IL which is directly related to the ability of the anion of the IL to complex Na+ and thereby remove it from the fuel. DN, τ parameters and β, in addition to interfacial tension and viscosity values, provide further information on the extraction mechanisms and predict performance, enabling chemical design of ILs that are ideal for fuel purification.

Use of ionic liquids to remove harmful M2+ contaminants from hydrocarbon streams

Abstract: Zinc contaminants have been identified as suspects leading to nozzle deposit formation and copper contaminants quickly reduce the oxidation stability of diesel fuel. Ionic liquids (ILs) are commonly referred to as ‘designer solvents’ due to the great degree of fine-tuning of physical and chemical properties afforded by modification of the constituent cation and anion. The tunable properties of the IL ions allows the ‘design’ to meet the requirements for a particular application, making ILs an ideal potential candidate for the extraction of trace (ppb to ppm) amounts of zinc and copper heavy metals from diesel fuel. We report for the first time that ILs can extract up to 99.3% of zinc at a zinc concentration of just 2 mg kg−1 and copper can be extracted up to 99.7% at copper concentration of just 1 mg kg−1 from a model diesel fuel. Factors affecting the extent of extraction were investigated via correlation with experimental descriptors. 23Na NMR was used in the determination of donor number (DN) and Kamlet–Taft parameters were gathered for each IL providing information of possible hydrogen-bond acidity/basicity (α/β), and dipolarity/polarizability effects (π*). In addition, the non-random two liquid (NRTL) model was applied to determine τ parameters for each of the ILs. We determined that the extraction is controlled strongly by the hydrogen bond basicity of the IL which is directly related to the ability of the anion of the IL to complex Zn2+ and Cu2+ thus removing it from the fuel. DN, τ parameters and β, in addition to density and viscosity values, provide further information on the extraction mechanisms and predict performance, informing chemical design of ILs that are ideal for fuel purification.

Treatment of lignocellulosic biomass with ionic liquid

Abstract: The present disclosure relates to an improved method for treating a lignocellulose biomass in order to dissolve the lignin therein, while the cellulose does not dissolve. The cellulose pulp obtained can be used to produce glucose. In addition the lignin can be isolated for subsequent use in the renewable chemical industry.