Imperial College London

Professor Tom Welton

Faculty of Natural SciencesDepartment of Chemistry

Professor of Sustainable Chemistry
 
 
 
//

Contact

 

+44 (0)20 7594 5763t.welton Website

 
 
//

Location

 

601AMolecular Sciences Research HubWhite City Campus

//

Summary

 

Publications

Publication Type
Year
to

230 results found

Chan KLA, Shalygin AS, Martyanov ON, Welton T, Kazarian SGet al., 2021, High throughput study of ionic liquids in controlled environments with FTIR spectroscopic imaging, Journal of Molecular Liquids, Vol: 337, ISSN: 0167-7322

In situ characterisation of ionic liquids under a controlled environment has been performed in a high throughput manner using macro ATR-FTIR spectroscopic imaging. 14 different ionic liquids with cations 1-butyl-3-methylimidazolium ([C mim]), 1-butyl-2,3-dimethylimidazolium ([C mmim]) and 1-butyl-3-methylpyrrolidinium ([C C pyrr]) and anions hexafluorophosphate ([PF ]), tetrafluoroborate ([BF ]), bis(trifluoromethylsulfonyl)imide ([NTf ]), perchlorate ([ClO ]), trifluoromethanesulfonate ([CF SO ]), nitrate ([NO ]), methanesulfonate ([CH SO ]) and trifluoroacetate ([TA]) were studied. The ionic liquids were deposited onto the measuring surface of the ATR crystal in the corresponding accessory hosted in the FTIR imaging system. Then these samples were exposed to a controlled environment of toluene and water vapour and spectra acquired simultaneously. Changing the structure of the cation head group from [C mim] to [C mmim] or [C C pyrr] only had a small effect on the toluene absorption while increasing the length of the alkyl chain of the cation (e.g. [C mim]) has shown a significant increase in toluene absorption. The ionic liquids with the anion [NTf ] were found to absorb the highest amount of toluene followed by [CF SO ], then [PF ], [ClO ], [NO ] and [TA], and the lowest amount of toluene was absorbed in ionic liquids with [BF ] or [CH SO ] anions. The amount of water absorbed increases in the order: [C mim][CH SO ] > [C mim][TA] > [C mim][NO ] > [C mim][CF SO ] > [C mim][ClO ] ~ [C mim][BF ] ~ [C mmim][BF ] > [C mim][BF ] > [C mim][PF ] ~ [C mmim][PF ] > [C mim][NTf ] ~ [C mmim][NTf ] ~ [C C pyrr][NTf ]. This work has demonstrated that spectroscopic imaging provides a platform for the simultaneous screening of multiple ionic liquids in situ, when under controlled environments. 4 4 4 1 6 4 2 4 3 3 3 3 3 4 4 4 1 10 2 3 3 6 4 3 4 3 3 4 3 3 4 4 3 4 3 3 4 4 4 4 4 4 10 4 4 6 4 6 4 2 4 2 4 1 2

Journal article

Sillero L, Prado R, Welton T, Labidi Jet al., 2021, Energy and environmental analysis of flavonoids extraction from bark using alternative solvents, Journal of Cleaner Production, Vol: 308, ISSN: 0959-6526

Tree barks are rich in extractive compounds, among which the flavonoids are considered as products of interest. Due to the increase in the demand for these natural products, the development of efficient and sustainable extraction processes is needed. This work aimed to study the selective extraction of flavonoids from Larix decidua bark using an environmentally friendly process. For this purpose, different extraction techniques as well as different solvents were used in order to achieve the highest flavonoid content. The characterisation results revealed improvements in extraction yield not only with the use of intensification processes, but also with the use of ionic liquids as solvents with a proven selectivity for flavonoids. [C C im]Br and [C C im][BF ] considerably improved the total flavonoid content in comparison with the other extraction methods. The antioxidant capacities of all the extracts obtained were very high, confirming their potential for different applications. The [C C im]Br (25 wt%) was selected as the best solvent not only because of its good flavonoid extraction ability, but also because of the good antioxidant properties of the extract, and simultaneous microwave-ultrasound assisted extraction was the most energy saving process. 4 1 4 1 4 4 1

Journal article

Koutsoukos S, Philippi F, Malaret F, Welton Tet al., 2021, A review on machine learning algorithms for the ionic liquid chemical space, CHEMICAL SCIENCE, Vol: 12, Pages: 6820-6843, ISSN: 2041-6520

Journal article

Toda S, Clark R, Welton T, Shigeto Set al., 2021, Observation of the Pockels Effect in Ionic Liquids and Insights into the Length Scale of Potential-Induced Ordering, LANGMUIR, Vol: 37, Pages: 5193-5201, ISSN: 0743-7463

Journal article

Welton T, 2021, Sustainability and international chemistry collaboration, NATIONAL SCIENCE REVIEW, Vol: 8, ISSN: 2095-5138

Journal article

Philippi F, Welton T, 2021, Targeted modifications in ionic liquids from understanding to design, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 6993-7021, ISSN: 1463-9076

Journal article

Bakis E, van den Bruinhorst A, Pison L, Palazzo I, Chang T, Kjellberg M, Weber CC, Gomes MC, Welton Tet al., 2021, Mixing divalent ionic liquids: effects of charge and side-chains, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 4624-4635, ISSN: 1463-9076

Journal article

Lemus J, Santiago R, Hospital-Benito D, Welton T, Hallett JP, Palomar Jet al., 2021, Process Analysis of Ionic Liquid-Based Blends as H2S Absorbents: Search for Thermodynamic/Kinetic Synergies, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 9, Pages: 2080-2088, ISSN: 2168-0485

Journal article

Philippi F, Rauber D, Kuttich B, Kraus T, Kay CWM, Hempelmann R, Hunt PA, Welton Tet al., 2020, Ether functionalisation, ion conformation and the optimisation of macroscopic properties in ionic liquids, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 22, Pages: 23038-23056, ISSN: 1463-9076

Journal article

Philippi F, Pugh D, Rauber D, Welton T, Hunt PAet al., 2020, Conformational design concepts for anions in ionic liquids, Chemical Science, Vol: 11, Pages: 6405-6422, ISSN: 2041-6520

The identification of specific design concepts for the in silico design of ionic liquids (ILs) has been accomplished using theoretical methods. Molecular building blocks, such as interchangeable functional groups, are used to design a priori new ILs which have subsequently been experimentally investigated. The conformational design concepts are developed by separately and systematically changing the central (imide), bridging (sulfonyl) and end (trifluoromethyl) group of the bis(trifluoromethanesulfonyl)imide [N(Tf)2]− anion and examining the resultant potential energy surfaces. It is shown that these design concepts can be used to tune separately the minimum energy geometry, transition state barrier height and relative stability of different conformers. The insights obtained have been used to design two novel anions for ILs, trifluoroacetyl(methylsulfonyl)imide [N(Ms)(TFA)]− and acetyl(trifluoromethanesulfonyl)imide [N(Tf)(Ac)]−. The computationally predicted structures show excellent agreement with experimental structures obtained from X-ray crystallography. [C4C1im][N(Tf)(Ac)] and [C4C1im][N(Ms)(TFA)] ILs have been synthesised and ion diffusion coefficients examined using pulsed field gradient stimulated echo NMR spectroscopy. Significantly increased diffusion was observed for the more flexible [N(Tf)(Ac)]− compared with the more rigid [N(Ms)(TFA)]− analogue. Furthermore, a pronounced impact on the fluidity was observed. The viscosity of the IL with the rigid anion was found to be twice as high as the viscosity of the IL with the flexible anion. The design concepts presented in this work will enable researchers in academia and industry to tailor anions to provide ILs with specific desired properties.

Journal article

Clark R, Nawawi MA, Dobre A, Pugh D, Liu Q, Ivanov AP, White AJP, Edel JB, Kuimova MK, McIntosh AJS, Welton Tet al., 2020, The effect of structural heterogeneity upon the microviscosity of ionic liquids, CHEMICAL SCIENCE, Vol: 11, Pages: 6121-6133, ISSN: 2041-6520

Journal article

Mann SK, Devgan MK, Franks WT, Huband S, Chan CL, Griffith J, Pugh D, Brooks NJ, Welton T, Pham TN, McQueen LL, Lewandowski JR, Brown SPet al., 2020, MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 124, Pages: 4975-4988, ISSN: 1520-6106

Journal article

Sillero L, Prado R, Welton T, Labidi Jet al., 2020, Energetic and environmental analysis of different techniques for biomolecules extractions, Chemical Engineering Transactions, Vol: 81, Pages: 631-636

There is an increase in the demand of natural and environmentally more sustainable products, for that the biorefinery is a very promising tool due to its capacity to develop more sustainable products. Biorefinery processes are being optimized to reduce the global energy consumption and environmental impact by increasing extraction yields. In this work, two intensification techniques, microwave-assisted extraction and ultrasound-assisted extraction, have been tested and their results have been compared with those obtained by the conventional method. The best results were obtained with microwave-assisted extraction. Another studied aspect was the selectivity of the solvent, for which three ionic liquids ([C4C1im][Br], [C4C1im][OAc] and [C4C1im][BF4]) and two deep eutectic solvents (Choline Chloride:Urea (1:2) and Choline Chloride: 1,4-butanediol (1:2)) were tested. The best extraction yield was obtained with Choline Chloride:Urea (1:2). The objective of this work was the evaluation of the impact of the processes in terms of energy consumption and solvents' toxicity, in addition to the determination of the extraction process performance. For this, an analysis of energy consumption was performed, with microwave assisted extraction having the lowest consumption. For the toxicity study different parameters were taken into account, concluding that deep eutectic solvents are a good option. In conclusion, the combination of microwave assisted extraction with deep eutectic solvents can be considered the most efficient extraction method.

Journal article

Clark R, von Domaros M, McIntosh AJS, Luzar A, Kirchner B, Welton Tet al., 2019, Effect of an external electric field on the dynamics and intramolecular structures of ions in an ionic liquid, JOURNAL OF CHEMICAL PHYSICS, Vol: 151, ISSN: 0021-9606

Journal article

Weber CC, Brooks NJ, Castiglione F, Mauri M, Simonutti R, Mele A, Welton Tet al., 2019, On the structural origin of free volume in 1-alkyl-3-methylimidazolium ionic liquid mixtures: a SAXS and 129Xe NMR study., Physical Chemistry Chemical Physics, Vol: 21, Pages: 5999-6010, ISSN: 1463-9076

Ionic liquid (IL) mixtures enable the design of fluids with finely tuned structural and physicochemical properties for myriad applications. In order to rationally develop and design IL mixtures with the desired properties, a thorough understanding of the structural origins of their physicochemical properties and the thermodynamics of mixing needs to be developed. To elucidate the structural origins of the excess molar volume within IL mixtures containing ions with different alkyl chain lengths, 3 IL mixtures containing 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ILs have been explored in a joint small angle X-ray scattering (SAXS) and 129Xe NMR study. The apolar domains of the IL mixtures were shown to possess similar dimensions to the largest alkyl chain of the mixture with the size evolution determined by whether the shorter alkyl chain was able to interact with the apolar domain. 129Xe NMR results illustrated that the origin of excess molar volume in these mixtures was due to fluctuations within these apolar domains arising from alkyl chain mismatch, with the formation of a greater number of smaller voids within the IL structure. These results indicate that free volume effects for these types of mixtures can be predicted from simple considerations of IL structure and that the structural basis for the formation of excess molar volume in these mixtures is substantially different to IL mixtures formed of different types of ions.

Journal article

Gehrke S, Reckien W, Palazzo I, Welton T, Hollóczki Oet al., 2019, On the Carbene-Like Reactions of Imidazolium Acetate Ionic Liquids: Can Theory and Experiments Agree?, European Journal of Organic Chemistry, Vol: 2019, Pages: 504-511, ISSN: 1434-193X

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The N-heterocyclic carbene organocatalytic reactivity of the 1-ethyl-3-methylimidazolium acetate ionic liquid was investigated on the model reaction between this solvent and anisaldehyde. The formation of carbenes by a proton transfer from the cation to the anion was compared to a direct reaction mechanism, in which the proton transfer and the C–C bond formation between catalyst and substrate occurs in a single elementary step. Interestingly, the two reaction mechanisms show a much smaller difference in activation energies than those observed for analogous catalytic systems with neutral bases, showing that the mechanism might switch from one to the other at different temperatures or with different substrates. In this particular case, however, the direct reaction mechanism, avoiding free carbenes in the solution, is apparently more feasible. Based on the detailed analysis of this reaction path, the earlier contradictions between theory and experiments can be resolved, resulting in a consistent mechanistic picture for the related processes. Additionally, we show on the example of a platinum surface that introducing metal probes into the liquid may induce carbene-like reactions, as the formation of a strong coordinative bond between the carbene and a platinum atom at the surface is highly exothermic, shifting the acid-base equilibrium considerably.

Journal article

Welton T, 2018, Editorial Overview: UN Sustainable Development Goals: How can sustainable/green chemistry contribute? There can be more than one approach, Current Opinion in Green and Sustainable Chemistry, Vol: 13, Pages: A7-A9, ISSN: 2452-2236

Journal article

Welton T, 2018, Ionic liquids: a brief history., Biophysical Reviews, Vol: 10, Pages: 691-706, ISSN: 1867-2450

There is no doubt that ionic liquids have become a major subject of study for modern chemistry. We have become used to ever more publications in the field each year, although there is some evidence that this is beginning to plateau at approximately 3500 papers each year. They have been the subject of several major reviews and books, dealing with different applications and aspects of their behaviours. In this article, I will show a little of how interest in ionic liquids grew and developed.

Journal article

Welton T, 2018, Ken Seddon-obituary., Biophys Rev, Vol: 10, ISSN: 1867-2450

Journal article

Vincent S, Prado R, Kuzmina O, Potter K, Bhardwaj J, Wanasekara ND, Harniman RL, Koutsomitopoulou A, Eichhorn SJ, Welton T, Rahatekar SSet al., 2018, Regenerated cellulose and willow lignin blends as potential renewable precursors for carbon fibers, ACS Sustainable Chemistry and Engineering, Vol: 6, Pages: 5903-5910, ISSN: 2168-0485

We report on the extraction of lignin from willow and its use to manufacture cellulose-lignin fibers as potential precursors for the manufacture of carbon fibers. The lignin from willow was extracted using triethylammonium hydrogen sulfate [Et3NH][HSO4]. The lignin extracted by this process was characterized by ATR-IR and elemental analysis, which indicated a high carbon yield. 1-Ethyl-3-methylimidazolium acetate [C2C1im][OAc] was then used as a common solvent to dissolve cellulose and lignin to manufacture lignin-cellulose fiber blends. The Young’s modulus of a 75:25 lignin/cellulose fiber was found to be 3.0 ± 0.5 GPa, which increased to 5.9 ± 0.6 GPa for a 25:75 lignin/cellulose blend. From a characterization of the surface morphology, using scanning electron microscopy (SEM) and atomic force microscopy (AFM), it was observed that higher lignin content in the fiber blend increased the surface roughness. FT-IR analysis confirmed the presence of aromatic groups related to lignin in the obtained fibers from the presence of peaks located at ∼1505 cm–1 and ∼1607 cm–1. The presence of lignin improves the thermal stability of the fiber blends by allowing them to degrade over a wider temperature range. The presence of lignin also improved the carbon yield during carbonization. Therefore, the lignin-cellulose fibers developed in this work can offer an excellent alternative to pure cellulose or lignin filaments.

Journal article

Bastos JC, Carvalho SF, Welton T, Canongia Lopes JN, Rebelo LPN, Shimizu K, Araujo JMM, Pereiro ABet al., 2018, Design of task-specific fluorinated ionic liquids: nanosegregation versus hydrogen-bonding ability in aqueous solutions, Chemical Communications, Vol: 54, Pages: 3524-3527, ISSN: 1359-7345

We demonstrate that fluorinated ionic liquids reduce the impact of the addition of water upon the ionic liquid's H-bond acceptance ability. This is a key factor to obtain functionalized materials to be used e.g. in the dissolution of biomolecules, extraction processes or material engineering.

Journal article

Clark R, Edel J, Kirchner B, Kuimova M, McIntosh A, Nawawi M, von Domaros M, Welton Tet al., 2018, Ion diffusion in ionic liquids in electric fields, 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727

Conference paper

Holbrey J, Welton T, 2018, Obituary: Kenneth R. Seddon: 1950-2018, GREEN CHEMISTRY, Vol: 20, Pages: 776-776, ISSN: 1463-9262

Journal article

Gehrke S, von Domaros M, Clark R, Holloczki O, Brehm M, Welton T, Luzar A, Kirchner Bet al., 2018, Structure and lifetimes in ionic liquids and their mixtures, FARADAY DISCUSSIONS, Vol: 206, Pages: 219-245, ISSN: 1359-6640

Journal article

Florindo C, McIntosh AJS, Welton T, Branco LC, Marrucho IMet al., 2017, A closer look into deep eutectic solvents: exploring intermolecular interactions using solvatochromic probes., Physical Chemistry Chemical Physics, Vol: 20, Pages: 206-213, ISSN: 1463-9076

Deep eutectic solvents (DESs) constitute a new class of ionic solvents that has been developing at a fast pace in recent years. Since these solvents are commonly suggested as green alternatives to organic solvents, it is important to understand their physical properties. In particular, polarity plays an important role in solvation phenomena. In this work, the polarity of different families of DESs was studied through solvatochromic responses of UV-vis absorption probes. Kamlet-Taft α, β, π* and ETN parameters were evaluated using different solvatochromic probes, as 2,6-dichloro-4-(2,4,6-triphenyl-N-pyridino)-phenolate (Reichardt's betaine dye 33), 4-nitroaniline, and N,N-diethyl-4-nitroaniline for several families of DESs based on cholinium chloride, dl-menthol and a quaternary ammonium salt ([N4444]Cl). In addition, a study to understand the difference in polarity properties between DESs and the corresponding ILs, namely ILs based on cholinium cation and carboxylic acids as anions ([Ch][Lev], [Ch][Gly] and [Ch][Mal]), was carried out. The chemical structure of the hydrogen bond acceptor (HBA) in a DES clearly controls the dipolarity/polarizability afforded by the DES. Moreover, Kamlet-Taft parameters do not vary much within the family, but they differ among families based on different HBA, either for DESs containing salts ([Ch]Cl or [N4444]Cl) or neutral compounds (dl-menthol). A substitution of the HBD was also found to play an important role in solvatochromic probe behaviour for all the studied systems.

Journal article

Kuzmina O, Bhardwaj J, Vincent SR, Wanasekara ND, Kalossaka LM, Griffith J, Potthast A, Rahatekar S, Eichhorn SJ, Welton Tet al., 2017, Superbase ionic liquids for effective cellulose processing from dissolution to carbonisation, Green Chemistry, Vol: 19, Pages: 5949-5957, ISSN: 1463-9262

A range of superbase derived ionic liquids (SILs) was synthesised and characterised. Their ability to dissolve cellulose and the characteristics of the produced fibres were correlated to their specific structural and solvent properties. 17 ionic liquids (ILs) (including 9 novel) were analysed and six ILs were selected to produce fibres: 1-ethyl-3-methylimidazolium acetate [C2C1im][OAc], 1-ethyl-3-methylimidazolium diethyl phosphate [C2C1im][DEP] and the SILs 1-ethyl-1,8-diazabicyclo[5.4.0]undec-7-enium diethylphosphate [DBUEt][DEP], 1,8-diazabicyclo[5.4.0]undec-7-enium acetate [DBUH][OAc], 1,5-diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] and 1-ethyl-1,5-diazabicyclo[4.3.0]non-5-enium diethylphsophate [DBNEt][DEP]. The mechanical properties of these fibres were investigated. The obtained fibres were then carbonised to explore possible application as carbon fibre precursors. The fibres obtained using a mixture of 1,5-diazabicyclo[4.3.0]non-5-enium based SILs with acetate and hexanoate anions (9 : 1), [DBNH][OAc][Hex], showed a promising combination of strength, stiffness and strain at failure values for applications in textiles and fibre reinforcement in renewable composites. Using Raman spectroscopy it is demonstrated that these fibres exhibit a relatively high degree of structural order, with fewer defects than the other materials. On the other hand, analogous fibres based on imidazolium cation with acetate and hexanoate anions (9 : 1), [C2C1im][OAc][Hex] showed a decline in the quality of the produced fibres compared to the fibres produced from [C2C1im][OAc], [C2C1im][DEP] or [DBNH][OAc][Hex].

Journal article

Hallett J, Welton T, Brandt-Talbot A, 2017, Treatment, EP3244371 (A1)

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.

Patent

Daud NMAN, Bakis E, Hallett JP, Weber CC, Welton Tet al., 2017, Evidence for the spontaneous formation of N-heterocyclic carbenes in imidazolium based ionic liquids, Chemical Communications, Vol: 53, Pages: 11154-11156, ISSN: 1359-7345

We present a study of the reactions of aldehydes in ionic liquids which gives evidence for the spontaneous formation of N-heterocyclic carbenes in ionic liquids based on 1,3-dialkyl substituted imidazolium cations from the lack of a deuterium isotope effect on the reaction of these ionic liquids with aldehydes.

Journal article

Kuzmina O, Hassan NH, Patel L, Ashworth C, Bakis E, White AJP, Hunt PA, Welton Tet al., 2017, The impact of ionic liquids on the coordination of anions with solvatochromic copper complexes, Dalton Transactions, Vol: 46, Pages: 12185-12200, ISSN: 1477-9234

Solvatochromic transition metal (TM)-complexes with weakly associating counter-anions are often used to evaluate traditional neutral solvent and anion coordination ability. However, when employed in ionic liquids (IL) many of the common assumptions made are no longer reliable. This study investigates the coordinating ability of weakly coordinating IL anions in traditional solvents and within IL solvents employing a range of solvatochromic copper complexes. Complexes of the form [Cu(acac)(tmen)][X] (acac = acetylacetonate, tmen = tetramethylethylenediamine) where [X]− = [ClO4]−, Cl−, [NO3]−, [SCN]−, [OTf]−, [NTf2]− and [PF6]− have been synthesised and characterised both experimentally and computationally. ILs based on these anions and imidazolium and pyrrolidinium cations, some of which are functionalised with hydroxyl and nitrile groups, have been examined. IL-anion coordination has been investigated and compared to typical weakly coordinating anions. We have found there is potential for competition at the Cu-centre and cases of anions traditionally assigned as weakly associating that demonstrate a stronger than expected level of coordinating ability within ILs. [Cu(acac)(tmen)][PF6] is shown to contain the least coordinating anion and is established as the most sensitive probe studied here. Using this probe, the donor numbers (DNs) of ILs have been determined. Relative donor ability is further confirmed based on the UV-Vis of a neutral complex, [Cu(sacsac)2] (sacsac = dithioacetylacetone), and DNs evaluated via23Na NMR spectroscopy. We demonstrate that ILs can span a wide donor range, similar in breadth to conventional solvents.

Journal article

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00152142&limit=30&person=true