Imperial College London

Prof Jason P. Hallett

Faculty of EngineeringDepartment of Chemical Engineering

Professor of Sustainable Chemical Technology
 
 
 
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Contact

 

+44 (0)20 7594 5388j.hallett Website

 
 
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Location

 

228bBone BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

172 results found

Skoronski E, Fernandes M, Malaret FJ, Hallett JPet al., 2020, Use of phosphonium ionic liquids for highly efficient extraction of phenolic compounds from water, Separation and Purification Technology, Vol: 248, Pages: 1-8, ISSN: 1383-5866

Ionic liquids (ILs) are undergoing development as extractants for phenolic compounds from wastewater due to their outstanding properties. Although many ILs have been considered, the use of phosphonium-based ILs has thus far been neglected, despite advantages in viscosity and low water solubility. This work details the application of phosphonium-based ILs for the liquid–liquid extraction of phenolic compounds from water. The selected target contaminants, phenol and 2,4-dichlorophenol, were extracted using two ILs composed of trihexyltetradecylphosphonium cations with decanoate or bis(2,4,4-trymetylpentyl)phosphinate anions. The effect of volume ratio, time of contact, pH, temperature and (inorganic) salt concentration on the extraction efficiency were examined. Additionally, the ILs used in this study were characterised in terms of water solubility and solvatochromic polarity. These ILs are less soluble in water than the others reported in the literature, and even at a volume ratio (water: ionic liquid) of 135, the IL can extract more than 99% and 89% of 2,4-dichlorophenol and phenol, respectively, in just 10 min, with the best extraction performance at lower temperatures and pH lower than the pKa of these phenolic compounds. Overall, these ILs demonstrate high potential for phenol extraction and can be considered as a powerful alternative for wastewater treatment.

Journal article

Tan S-Y, Hallett J, Geoff K, 2020, Electrodeposition of lead from methanesulfonic acid and methanesulfonate ionic liquid derivatives, Electrochimica Acta, Vol: 353, Pages: 1-11, ISSN: 0013-4686

The influence is reported of electrolyte composition on the electrochemistry of PbII and electrodeposition morphology of Pb in aqueous methanesulfonic acid (MSA) and two methanesulfonate-based ionic liquids: 1-butyl-3-methylimidazolium methanesulfonate and N,N-dimethylbutylammonium methanesulfonate. Cyclic voltammetry and chronoamperometry indicated that the reduction of PbII ions to Pb was a diffusion-controlled process proceeding via a two-electron transfer process at -0.67 V vs. Ag (1 M MSA) and involved 3-D progressive nucleation. Scanning electron microscopy showed a strong influence of deposition potential and electrolyte composition on the morphology of Pb deposits. Experimental data was used to model predictions of the specific electrical energy consumption for cathodic PbII electrodeposition coupled with either anodic oxygen evolution or PbO2 electrodeposition.

Journal article

Green S, Wheelhouse K, Payne A, Hallett J, Miller P, Bull Jet al., 2020, On the use of differential scanning calorimetry for thermal hazard assessment of new chemistry: Avoiding explosive mistakes, Angewandte Chemie International Edition, ISSN: 1433-7851

Differential scanning calorimetry (DSC) is increasingly used as evidence to support a favourable safety profile of novel chemistry, or to highlight the need for caution. DSC enables preliminary assessment of the thermal hazards of a potentially energetic compound. However, unlike other standard characterisation methods, which have well defined formats for reporting data, the current reporting of DSC results for thermal hazard assessment has shown concerning trends. Around half of all results in 2019 did not include experimental details required to replicate the procedure. Furthermore, analysis for thermal hazard assessment is often only conducted in unsealed crucibles, which could lead to misleading results and dangerously incorrect conclusions. We highlight the specific issues with DSC analysis of hazardous compounds currently in the organic chemistry literature and provide simple ‘best practice’ guidelines which will give chemists confidence in reported DSC results and the conclusions drawn from them.

Journal article

Chen M, Malaret F, Firth AEJ, Verdia P, Abouelela AR, Chen Y, Hallett JPet al., 2020, Design of a combined ionosolv-organosolv biomass fractionation process for biofuel production and high value-added lignin valorisation, GREEN CHEMISTRY, Vol: 22, Pages: 5161-5178, ISSN: 1463-9262

Journal article

Gschwend FJ, Hennequin LM, Brandt-Talbot A, Bedoya-Lora F, Kelsall GH, Polizzi K, Fennell PS, Hallett JPet al., 2020, Towards an environmentally and economically sustainable biorefinery: heavy metal contaminated waste wood as a low-cost feedstock in a low-cost ionic liquid process, GREEN CHEMISTRY, Vol: 22, Pages: 5032-5041, ISSN: 1463-9262

Journal article

Firth AEJ, Mac Dowell N, Fennell PS, Hallett JPet al., 2020, Assessing the economic viability of wetland remediation of wastewater, and the potential for parallel biomass valorisation, ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY, Vol: 6, Pages: 2103-2121, ISSN: 2053-1400

Journal article

Clarke CJ, Bui-Le L, Corbett PJ, Hallett JPet al., 2020, Implications for Heavy Metal Extractions from Hyper Saline Brines with [NTf2](-) Ionic Liquids: Performance, Solubility, and Cost, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 59, Pages: 12536-12544, ISSN: 0888-5885

Journal article

Chambon CL, Karia T, Sandwell P, Hallett JPet al., 2020, Techno-economic assessment of biomass gasification-based mini-grids for productive energy applications: The case of rural India, Renewable Energy, Vol: 154, Pages: 432-444, ISSN: 0960-1481

As the costs of solar PV continuously decrease and pollution legislation imposes less burning of agricultural residues, decentralized renewable energy is increasingly affordable for providing electricity to one billion people lacking access to a power grid. This paper presents a techno-economic feasibility case study of biomass gasification in off-grid and grid-connected mini-grids for community-scale energy application in rural Uttar Pradesh, India. Energy demand data was collected through surveys in a village with irrigation and agro-processing loads and off-grid households and used to construct a seasonal load profile based on statistical methods. This was used to simulate single-source and hybrid mini-grids based on solar PV, biomass gasification and diesel generation using HOMER Pro. Hybrid PV-biomass or PV-diesel systems were found to offer the highest reliability for off-grid power at the lowest cost. Single-source PV was cheaper than biomass gasification, though the cost of electricity is highly sensitive to biomass supply and gasifier maintenance. Both renewable options were around half the cost of diesel generation. The findings held across grid-connected systems with weak, moderate and strong reliability of grid supply. This suggests that biomass gasification-based mini-grids are not cost-competitive with PV unless the two generation sources are combined in a hybrid system, though they require operational testing prior to implementation.

Journal article

Clarke CJ, Bui-Le L, Hallett JP, Licence Pet al., 2020, Thermally-Stable Imidazolium Dicationic Ionic Liquids with Pyridine Functional Groups, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 8, Pages: 8762-8772, ISSN: 2168-0485

Journal article

Nakasu PYS, Clarke CJ, Rabelo SC, Costa AC, Brandt-Talbot A, Hallett JPet al., 2020, Interplay of Acid-Base Ratio and Recycling on the Pretreatment Performance of the Protic Ionic Liquid Monoethanolammonium Acetate, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 8, Pages: 7952-7961, ISSN: 2168-0485

Journal article

Baqeel H, Diaz I, Tulus V, Chachuat B, Guillén-Gosálbez G, Hallett Jet al., 2020, Role of life-cycle externalities in the valuation of protic ionic liquids – a case study in biomass pretreatment solvents, Green Chemistry, Vol: 22, Pages: 3132-3140, ISSN: 1463-9262

Ionic liquids have found their way into many applications where they show a high potential to replace traditional chemicals. But there are concerns over their ecological impacts (toxicity and biodegradability) and high cost, which have limited their use so far. The outcome of existing techno-economic and life-cycle assessments comparing ionic liquids with existing solvents has proven hard to interpret due to the many metrics used and trade-offs between them. For the first time, this paper couples the concept of monetization with detailed process simulation and life-cycle assessment to estimate the true cost of ionic liquids. A comparative case study on four solvents used in lignocellulosic biomass pretreatment is conducted: triethylammonium hydrogen sulfate [TEA][HSO4], 1-methylimidazolium hydrogen sulfate [HMIM][HSO4], acetone from fossil sources, and glycerol from renewable sources. The results show that the total monetized cost of production accounting for externalities can be more than double the direct costs estimated using conventional economic assessment methods. The ionic liquid [TEA][HSO4] is found to have the lowest total cost, while the renewable solvent glycerol presents the highest total cost. We expect this methodology to provide a starting point for future research and development in sustainable ionic liquids

Journal article

Gschwend FJV, Hallett JP, Brandt-Talbot A, 2020, Exploring the effect of water content and anion on the pretreatment of poplar with three 1-Ethyl-3-methylimidazolium ionic liquids, Molecules, Vol: 25, Pages: 2318-2318, ISSN: 1420-3049

We report on the pretreatment of poplar wood with three different 1-ethyl-3-methylimidazolium ionic liquids, [EMim][OAc], [EMim][MeSO3], and [EMim][HSO4], at varying water contents from 0–40 wt% at 100 °C. The performance was evaluated by observing the lignin and hemicellulose removal, as well as enzymatic saccharification and lignin yield. The mechanism of pretreatment varied between the ionic liquids studied, with the hydrogen sulfate ionic liquid performing delignification and hemicellulose hydrolysis more effectively than the other solvents across the investigated water content range. The acetate ionic liquid produced superior glucose yield at low water contents, while the hydrogen sulfate ionic liquid performed better at higher water contents and produced a recoverable lignin. The methanesulfonate ionic liquid did not introduce significant fractionation or enhancement of saccharification yield under the conditions used. These findings help distinguish the roles of anion hydrogen bonding, solvent acidity, and water content on ionic liquid pretreatment and can aid with anion and water content selections for different applications.

Journal article

Clarke C, Bui-Le L, Hallett J, 2020, Ion chromatography for monitoring [NTf2]- anion contaminants in pure and saline water, Analytical Methods, Vol: 12, Pages: 2244-2252, ISSN: 1759-9660

Hydrophobic ionic liquid containing bis(trifluoromethanesulfonyl)imide, [NTf2]-, anions partially dissolve in aqueous phases. The potential ecotoxicity of [NTf2]- means wastewater streams must be closely monitored to avoid environmental release. A new anion chromatography method is presented, which improves on existing techniques and methods by significantly decreasing analysis time and improving chromatographic peak properties. Subsequently, the limit of detection was lowered to 5 µM (1.4 ppm) and limit of quantification lowered to 30 μM (8.5 ppm), without the use of expensive concentrator columns or mass spectrometers. The chromatographic method employed a Dionex AS20 column designed for trace analysis of perchlorate in drinking water, which is ideal for highly polarizable [NTf2]- ions to be detected with high accuracy in the presence of high salinity samples, such as seawater. The technique is consequently ideal for environmental monitoring or process design of [NTf2]- ionic liquid-based applications.

Journal article

Bui-Le L, Clarke CJ, Bröhl A, Brogan APS, Arpino JAJ, Polizzi KM, Hallett Jet al., 2020, Revealing the complexity of ionic liquid-protein interactions through a multi-technique investigation, Communications Chemistry, Vol: 3, ISSN: 2399-3669

Ionic liquids offer exciting possibilities for biocatalysis as solvent properties provide rare opportunities for customizable, energy-efficient bioprocessing. Unfortunately, proteins and enzymes are generally unstable in ionic liquids and several attempts have been made to explain why; however, a comprehensive understanding of the ionic liquid–protein interactions remains elusive. Here, we present an analytical framework (circular dichroism (CD), fluorescence, ultraviolet-visible (UV/Vis) and nuclear magnetic resonance (NMR) spectroscopies, and small-angle X-ray scattering (SAXS)) to probe the interactions, structure, and stability of a model protein (green fluorescent protein (GFP)) in a range (acetate, chloride, triflate) of pyrrolidinium and imidazolium salts. We demonstrate that measuring protein stability requires a similar holistic analytical framework, as opposed to single-technique assessments that provide misleading conclusions. We reveal information on site-specific ionic liquid–protein interactions, revealing that triflate (the least interacting anion) induces a contraction in the protein size that reduces the barrier to unfolding. Robust frameworks such as this are critical to advancing non-aqueous biocatalysis and avoiding pitfalls associated with single-technique investigations.

Journal article

Tu W-C, Weigand L, Hummel M, Sixta H, Brandt-Talbot A, Hallett JPet al., 2020, Characterisation of cellulose pulps isolated from Miscanthus using a low-cost acidic ionic liquid, Cellulose, Vol: 27, Pages: 4745-4761, ISSN: 0969-0239

The ionoSolv pretreatment generates a cellulose pulp by extracting hemicellulose and lignin using low-cost ionic liquids. In this study, cellulose pulp was obtained from Miscanthus × giganteus using the protic ionic liquid triethylammonium hydrogen sulfate [N2220][HSO4] with 20% water as a co-solvent and characterised in detail for its material properties as a function of pretreatment severity. We measured the particle size distribution, porosity and crystallinity of the unbleached pulps and the molar weight distribution of the cellulose contained within. We report that the surface area increased and the size of the pulp particles decreased as ionoSolv processing progressed. While the native cellulose I structure was maintained, the average degree of polymerisation of the cellulose was reduced to a DPn of around 300, showing the cellulose polymers are shortened. We correlate the pulp properties with enzymatic saccharification yields, concluding that enzymatic saccharification of the cellulose after ionoSolv pretreatment is mainly enhanced by removing hemicellulose and lignin. We also observed that overtreatment deteriorated saccharification yield and that this coincides with cellulose fibrils becoming coated with pseudolignin redeposited from the ionic liquid solution, as demonstrated by FT-IR spectroscopy. Pseudolignin deposition increases the apparent lignin content, which is likely to increase chemical demand in bleaching, suggesting that both glucose release and material use benefit from a minimum lignin content. Overall, this study demonstrates that cellulose pulps isolated with ionoSolv processing are not only a promising intermediate for high-yield release of purified glucose for biorefining, but also have attractive properties for materials applications that require cellulose I fibrils.

Journal article

Malaret F, Gschwend FJV, Lopes JM, Tu WC, Hallett Jet al., 2020, Eucalyptus Red Grandis pretreatment with protic ionic liquids: effect of severity and influence of sub/super-critical CO2 atmosphere on pretreatment performance, RSC Advances: an international journal to further the chemical sciences, Vol: 10, Pages: 16050-16060, ISSN: 2046-2069

Deconstruction of lignocellulosic biomass with low-cost ionic liquids (ILs) has proven to be a promising technology that could be implemented in a biorefinery to obtain renewable materials, fuels and chemicals. This study investigates the pretreatment efficacy of the ionoSolv pretreatment of Eucalyptus red grandis using the low-cost ionic liquid triethylammonium hydrogen sulfate ([N2220][HSO4]) in the presence of 20 wt% water at 10% solids loading. The temperatures investigated were 120 °C and 150 °C. Also, the influence of performing the pretreatment under sub-critical and supercritical CO2 was investigated. The IL used is very effective in deconstructing eucalyptus, producing cellulose-rich pulps resulting in enzymatic saccharification yields of 86% for some pretreatment conditions. It has been found that under a CO2 atmosphere, the ionoSolv process is pressure independent. The good performance of this IL in the pretreatment of eucalyptus is promising for the development of a large-scale ionoSolv pretreatment processes.

Journal article

Chambon CL, Fitriyanti V, Verdía P, Yang SM, Hérou S, Titirici M-M, Brandt-Talbot A, Fennell PS, Hallett JPet al., 2020, Fractionation by sequential antisolvent precipitation of grass, softwood, and hardwood lignins isolated using low-cost ionic liquids and water, ACS Sustainable Chemistry & Engineering, Vol: 8, Pages: 3751-3761, ISSN: 2168-0485

In this study, fractionation by sequential antisolvent precipitation was applied to ionoSolv lignins for the first time. Pretreatment with the aqueous low-cost protic ionic liquid N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4], 80 wt % in water) was applied to Miscanthus (herbaceous), willow (hardwood), and pine (softwood) to extract lignin. Then, lignin was sequentially precipitated by the addition of water as an antisolvent. Fractionation appeared to be controlled by the molecular weight of lignin polymers. Fractions isolated with minimal water volumes were shown to have high molecular weight, polydispersity, thermal stability, and Tg (178 °C). Later precipitates were more monodisperse and had high phenolic and total hydroxyl content and lower thermal stability and Tg (136 °C). Addition of 1 g of water per gram of dry IL was able to precipitate up to 90 wt % of lignin. Fractional precipitation represents a novel lignin isolation technique that can be performed as part of the lignin recovery procedure enabling a high degree of control of lignin properties. The effect of the fractionation on lignin structural, chemical, and thermal properties was thoroughly examined by two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry and compared to the unfractionated lignin precipitate obtained by addition of an excess of water.

Journal article

Brogan APS, Clarke CJ, Charalambidou A, Loynachan CN, Norman SE, Doutch J, Hallett JPet al., 2020, Expanding the design space of gel materials through ionic liquid mediated mechanical and structural tuneability, MATERIALS HORIZONS, Vol: 7, Pages: 820-826, ISSN: 2051-6347

Journal article

Al Ghatta A, Wilton-Ely JDET, Hallett JP, 2020, Efficient formation of 2,5-diformylfuran (DFF) in ionic liquids at high substrate loadings and low oxygen pressure with separation through sublimation, ACS Sustainable Chemistry & Engineering, Vol: 8, Pages: 2462-2471, ISSN: 2168-0485

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) using oxygen (1 atm) with a TEMPO and CuCl catalyst system is investigated using a range of imidazolium-based ionic liquids (ILs) and various bases at different HMF substrate loadings (10-50%). This represents the first example of HMF to DFF conversion in ionic liquid media under homogeneous catalysis conditions, revealing dramatic differences in performance between the ILs. In the non-coordinating, hydrophobic ionic liquid, [bmim][NTf2], 90% DFF yield is obtained at 5 mol% catalyst loading after 6 hours at 80 °C at a very high 40% HMF loading. Increasing the temperature to 100 °C leads to a lower yield, attributed to loss of volatile TEMPO from the reaction medium. A system using TEMPO and pyridine immobilized within the ionic liquid [bmim][NTf2] results in selective conversion of HMF to high purity DFF. It also allows the DFF formed to be isolated by sublimation in 81% yield before a further cycle is performed. Subsequent catalyst deactivation is probed by X-ray photoelectron spectroscopy (XPS). Synthesis from fructose in a two-step process achieves a 55% isolated DFF yield. This approach overcomes significant drawbacks previously reported for this transformation, such as solvent toxicity, separation and purification problems as well as the need for high oxygen pressures. Further oxidation of HMF with this system leads to a 62% yield of 5-formyl-2-furancarboxylic acid (FFCA). The separation of this compound can be achieved by sublimation of DFF followed by solvent extraction.

Journal article

Green S, Wheelhouse K, Payne A, Hallett J, Miller P, Bull Jet al., 2020, Thermal stability and explosive hazard assessment of diazo compounds and diazo transfer reagents, Organic Process Research and Development, Vol: 24, Pages: 67-84, ISSN: 1083-6160

Despite their wide use in academia as metal-carbene precursors, diazo compounds are often avoided in industry owing to concerns over their instability, exothermic decomposition and potential explosive behaviour. The stability of sulfonyl azides and other diazo-transfer reagents is relatively well understood, but there is little reliable data available for diazo compounds. This work firstly collates available sensitivity and thermal analysis data for diazo-transfer reagents and diazo compounds to act as an accessible reference resource. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC) data for the model donor/acceptor diazo compound ethyl (phenyl)diazoacetate is presented. We also present a rigorous DSC dataset with 43 other diazo compounds, enabling direct comparison to other energetic materials to provide a clear reference work to the academic and industrial chemistry communities. Interestingly, there is a wide range of onset temperatures (Tonset) for this series of compounds which varied between 75 and 160 °C. The thermal stability variation depends on the electronic effect of substituents and the amount of charge delocalisation. A statistical model is demonstrated to predict the thermal stability of differently substituted phenyl diazoacetates. A maximum recommended process temperature (TD24) to avoid decomposition is estimated for selected diazo compounds. Average enthalpy of decomposition (∆HD) for diazo compounds without other energetic functional groups is −102 kJ mol−1. Several diazo transfer reagents are analyzed using the same DSC protocol and found to have higher thermal stability, which is in general agreement with reported values. For sulfonyl azide reagents an average ∆HD of −201 kJ mol−1 is observed. High quality thermal data from ARC experiments shows the initiation of decomposition for ethyl (phenyl)diazoacetate to be 60 °C , compared to 100 °C for t

Journal article

Yao JG, Fennell PS, Hallett JP, 2020, Chapter 4: Ionic liquids, RSC Energy and Environment Series, Pages: 69-105, ISBN: 9781788014700

© The Royal Society of Chemistry 2020. The use of ionic liquids (ILs) is a relatively new and promising technology for CO2 capture and storage (CCS). Ionic liquids, which are essentially organic salts with melting points below 100 °C, are particularly attractive owing to their negligible volatility, chemical and thermal stability, and most importantly, their designability. Their low reaction enthalpy with CO2 allows regeneration under less energy intensive conditions relative to conventional amine solvents, and choosing their anion/cation pairing can allow their properties to be controlled. Although conventional ILs are able to physically absorb CO2, greater capture capacities can be achieved by tethering functional groups which can chemically bind to CO2 on either or both of the cation and anion. In addition to liquid-gas capture, ILs have also demonstrated success when incorporated into gas separation membranes. To date, most studies have been focused at the laboratory scale and under ideal conditions (i.e., capture under high CO2 partial pressures, and regeneration in N2); however, in order to progress with this technology, it is imperative to explore the behaviour of ILs under industrially-relevant environments. In addition, further process simulation and economic studies should be carried out to help scale up the technology.

Book chapter

Green SP, Wheelhouse KM, Payne AD, Hallett JP, Miller PW, Bull JAet al., 2020, On the Use of Differential Scanning Calorimetry for Thermal Hazard Assessment of New Chemistry: Avoiding Explosive Mistakes, Angewandte Chemie, ISSN: 0044-8249

© 2020 Wiley-VCH GmbH Differential scanning calorimetry (DSC) is increasingly used as evidence to support a favourable safety profile of novel chemistry, or to highlight the need for caution. DSC enables preliminary assessment of the thermal hazards of a potentially energetic compound. However, unlike other standard characterisation methods, which have well defined formats for reporting data, the current reporting of DSC results for thermal hazard assessment has shown concerning trends. Around half of all results in 2019 did not include experimental details required to replicate the procedure. Furthermore, analysis for thermal hazard assessment is often only conducted in unsealed crucibles, which could lead to misleading results and dangerously incorrect conclusions. We highlight the specific issues with DSC analysis of hazardous compounds currently in the organic chemistry literature and provide simple “best practice” guidelines which will give chemists confidence in reported DSC results and the conclusions drawn from them.

Journal article

Tu W-C, Hallett JP, 2019, Recent advances in the pretreatment of lignocellulosic biomass, CURRENT OPINION IN GREEN AND SUSTAINABLE CHEMISTRY, Vol: 20, Pages: 11-17, ISSN: 2452-2236

Journal article

Clarke CJ, Hayama S, Hawes A, Hallett JP, Chamberlain TW, Lovelock KRJ, Besley NAet al., 2019, Zinc 1s Valence-to-Core X-ray Emission Spectroscopy of Halozincate Complexes, JOURNAL OF PHYSICAL CHEMISTRY A, Vol: 123, Pages: 9552-9559, ISSN: 1089-5639

Journal article

Dickinson E, Harrison M, Parker M, Dickinson M, Donarski J, Charlton A, Nolan R, Rafat A, Gschwend F, Hallett J, Wakefield M, Wilson Jet al., 2019, From waste to food: optimising the breakdown of oil palm waste to provide substrate for insects farmed as animal feed, PLoS One, Vol: 14, ISSN: 1932-6203

Waste biomass from the palm oil industry is currently burned as a means of disposal and solutions are required to reduce the environmental impact. Whilst some waste biomass can be recycled to provide green energy such as biogas, this investigation aimed to optimise experimental conditions for recycling palm waste into substrate for insects, farmed as a sustainable high-protein animal feed. NMR spectroscopy and LC-HRMS were used to analyse the composition of palm empty fruit bunches (EFB) under experimental conditions optimised to produce nutritious substrate rather than biogas. Statistical pattern recognition techniques were used to investigate differences in composition for various combinations of pre-processing and anaerobic digestion (AD) methods. Pre-processing methods included steaming, pressure cooking, composting, microwaving, and breaking down the EFB using ionic liquids. AD conditions which were modified in combination with pre-processing methods were ratios of EFB:digestate and pH. Results show that the selection of pre-processing method affects the breakdown of the palm waste and subsequently the substrate composition and biogas production. Although large-scale insect feeding trials will be required to determine nutritional content, we found that conditions can be optimised to recycle palm waste for the production of substrate for insect rearing. Pre-processing EFB using ionic liquid before AD at pH6 with a 2:1 digestate:EFB ratio were found to be the best combination of experimental conditions.

Journal article

Al Ghatta A, Wilton-Ely J, Hallett J, 2019, Rapid, high‐yield fructose dehydration to HMF in mixtures of water and the non‐coordinating Ionic Liquid [bmim][OTf], ChemSusChem, Vol: 12, Pages: 4452-4460, ISSN: 1864-5631

The non‐coordinating ionic liquid [bmim][OTf] is an effective and versatile solvent for the high‐yield dehydration of fructose to the platform chemical HMF over short reaction times. In contrast to literature reports, which report low yields for this transformation in ionic liquids (ILs) with non‐coordinating anions, this contribution reveals that the water content is an essential parameter for an efficient reaction in ILs. Achieving the optimum amount of water can increase the yield dramatically by regulating the acidity of the catalyst and partially suppressing the side reaction caused by self‐condensation of HMF. Using acid catalysis in [bmim][OTf] with 3.5% water content, yields above 80% can be achieved at 100 °C in only 10 minutes, even at high (14%) fructose loading. These results suggest that [bmim][OTf] represents a superior medium for solvent extraction of HMF compared to halide‐based ILs, allowing the option of isolation or further valorisation of the HMF formed.

Journal article

Al Ghatta A, Wilton-Ely JDET, Hallett JP, 2019, Strategies for the separation of the furanic compounds HMF, DFF, FFCA and FDCA from Ionic liquids, ACS Sustainable Chemistry & Engineering, Vol: 7, Pages: 16483-16492, ISSN: 2168-0485

The catalytic upgrading of sugar derivatives into valuable building blocks represents an extremely important challenge intrinsic to the attempts to establish a green economy. However, the significance of separation and purification are often relegated to a marginal role or overlooked completely despite this aspect being critical for potential scale up. It is well established that the synthesis of 5-hydroxymethylfurfural (HMF) from sugars in ionic liquid media is a valuable, sustainable and high-yielding chemical pathway, but product separation has always remained an unresolved issue. In this contribution, the separation of HMF and three of its derivatives, 2,5-diformylfuran (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) from ionic liquids is analyzed. Various ionic liquids are screened in order to obtain an optimal separation process. The extraction of HMF is studied from the hydrophobic methyltrioctylammonium ionic liquids with water, obtaining a favorable partition coefficient for the aqueous phase. In contrast, its derivatives, DFF, FFCA and FDCA, can be easily separated by phase separation. DFF retains its sublimation attributes in the ionic liquid and can be readily separated in quantitative yields in high purity. This behavior is observed in ionic liquids but is not achievable in common organic solvents. FDCA and FFCA are separated by water addition and precipitation. It is found that less water is required for the precipitation of these compounds compared to dimethylsulfoxide (DMSO), which is a frequently employed reaction medium for their generation. The energy balance for regeneration of the ionic liquid after water addition is estimated using the enterprise ionic liquids database ILUAM. This study provides a set of solvent design guidelines for the selective synthesis, isolation and purification of these compounds in ionic liquids, aiding future reaction design.

Journal article

Brogan APS, Heldman N, Hallett JP, Belcher AMet al., 2019, Thermally robust solvent-free biofluids of M13 bacteriophage engineered for high compatibility with anhydrous ionic liquids, CHEMICAL COMMUNICATIONS, Vol: 55, Pages: 10752-10755, ISSN: 1359-7345

Journal article

Tan SY, Payne DJ, Hallett JP, Kelsall GHet al., 2019, Developments in electrochemical processes for recycling lead-acid batteries, Current Opinion in Electrochemistry, Vol: 16, Pages: 83-89, ISSN: 2451-9103

The lead-acid battery recycling industry is very well established, but the conventional pyrometallurgical processes are far from environmentally benign. Hence, recent developments of lead-acid battery recycling technologies have focused on low-temperature (electro-)hydrometallurgical processes, the subject of this review, covering modified electrolytes, improved reaction engineering, better reactor design and control of operating conditions.

Journal article

Green SP, Payne AD, Wheelhouse KM, Hallett JP, Miller PW, Bull JAet al., 2019, Diazo transfer reagent 2-azido-4,6-dimethoxy-1,3,5-triazine (ADT) Displays highly exothermic decomposition comparable to tosyl azide, The Journal of Organic Chemistry, Vol: 84, Pages: 5893-5898, ISSN: 0022-3263

2-Azido-4,6-dimethoxy-1,3,5-triazine (ADT) was reported recently as a new “intrinsically safe” diazo-transfer reagent. This assessment was based on differential scanning calorimetry data indicating that ADT exhibits endothermic decomposition. We present DSC data on ADT that show exothermic decomposition with an initiation temperature (Tinit) of 159 °C and an enthalpy of decomposition (ΔHD) of −1135 J g–1 (−207 kJ mol–1). We conclude that ADT is potentially explosive and must be treated with caution, being of comparable exothermic magnitude to tosyl azide (TsN3). A maximum recommended process temperature for ADT is 55 °C.

Journal article

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