Agnieszka Brandt | Imperial College London (original) (raw)
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The following two experiments were performed in duplicates in order to compare 1H-NMR spectroscop... more The following two experiments were performed in duplicates in order to compare 1H-NMR spectroscopy and HPLC for the quantitative analysis of HMF synthesised in this system. Rigorously dry environments were employed to ensure that both techniques were analysing under the same conditions. All reagents were purchased from Sigma-Aldrich whereas [C4C1im]Cl was synthesised and purified as described previously [52]. 1-butyl-3-methylimidazolium chloride ([C4C1im]Cl), cellulose (Sigmacell, 20 μm) and chromium(III) chloride hexahydrate (CrCl3·6H2O) are hygroscopic; therefore their handling and storage was carried out in a glovebox (N2 atmosphere). The glovebox water content was controlled in the presence of molecular sieves and the moisture and oxygen content was kept below 5 ppm. All handling was performed under air-free conditions, using standard Schlenk line techniques. The neat ionic liquid was dried under vacuum before use (24 h, 35 °C, 1.6 mbar). According to the conditions in Table S1,...
Green Chemistry
Softwood is an abundantly available feedstock for the bio-based industry, however, achieving cost... more Softwood is an abundantly available feedstock for the bio-based industry, however, achieving cost-effective sugar release is particularly challenging due to its guaiacyl-only lignin. Here, we report the highly effective pretreatment...
Faraday Discuss.
A wide variety of experimental and computational methods are used to probe sulfur atomic charges ... more A wide variety of experimental and computational methods are used to probe sulfur atomic charges in ionic liquids.
PLOS ONE
A number of ionic liquids have been shown to be excellent solvents for lignocellulosic biomass pr... more A number of ionic liquids have been shown to be excellent solvents for lignocellulosic biomass processing, and some of these are particularly effective in the production of the versatile chemical building block 5-hydroxymethylfurfural (HMF). In this study, the production of HMF from the simple sugar glucose in ionic liquid media is discussed. Several aspects of the selective catalytic formation of HMF from glucose have been elucidated using metal halide salts in two distinct ionic liquids, 1-butyl-3-methylimidazolium chloride and 1-butyl-3methylimidazolium hydrogen sulfate as well as mixtures of these, revealing key features for accelerating the desired reaction and suppressing byproduct formation. The choice of ionic liquid anion is revealed to be of particular importance, with low HMF yields in the case of hydrogen sulfate-based salts, which are reported to be effective for HMF production from fructose. The most successful system investigated in this study led to almost quantitative conversion of glucose to HMF (90% in only 30 minutes using 7 mol% catalyst loading at 120˚C) in a system which is selective for the desired product, has low energy intensity and is environmentally benign.
Green Chem., 2017
Cost-effective fractionation (pretreatment) of lignocellulosic biomass is necessary to enable its... more Cost-effective fractionation (pretreatment) of lignocellulosic biomass is necessary to enable its large-scale use as a source of liquid fuels, bio-based materials and bio-derived chemicals.
Inorganics, 2016
Cellulose is the single largest component of lignocellulosic biomass and is an attractive feedsto... more Cellulose is the single largest component of lignocellulosic biomass and is an attractive feedstock for a wide variety of renewable platform chemicals and biofuels, providing an alternative to petrochemicals and petrofuels. This potential is currently limited by the existing methods of transforming this poorly soluble polymer into useful chemical building blocks, such as 5-hydroxymethylfurfural (HMF). Ionic liquids have been used successfully to separate cellulose from the other components of lignocellulosic biomass and so the use of the same medium for the challenging transformation of cellulose into HMF would be highly attractive for the development of the biorefinery concept. In this report, ionic liquids based on 1-butyl-3-methylimidazolium cations [C 4 C 1 im] + with Lewis basic (X = Cl −) and Brønsted acidic (X = HSO 4 −) anions were used to investigate the direct catalytic transformation of cellulose to HMF. Variables probed included the composition of the ionic liquid medium, the metal catalyst, and the reaction conditions (temperature, substrate concentration). Lowering the cellulose loading and optimising the temperature achieved a 58% HMF yield after only one hour at 150 • C using a 7 mol % loading of the CrCl 3 catalyst. This compares favourably with current literature procedures requiring much longer reactions times or approaches that are difficult to scale such as microwave irradiation.
Journal of Visualized Experiments, 2016
Systematic and Applied Microbiology, 2009
Green Chemistry, 2014
The application of the protic ionic liquid 1-butylimidazolium hydrogen sulfate in the deconstruct... more The application of the protic ionic liquid 1-butylimidazolium hydrogen sulfate in the deconstruction (aka pretreatment) and fractionation of lignocellulosic biomass has been investigated. A cellulose rich pulp and a lignin fraction were produced. The pulp was subjected to enzymatic saccharification which allowed recovery of up to 90% of the glucan as fermentable glucose. The influence of the solution acidity on the deconstruction of Miscanthus giganteus was examined by varying the 1-butylimidazole to sulfuric acid ratio. Increased acidity led to shorter preteatment times and resulted in reduced hemicellulose content in the pulp. Addition of water to the ionic liquid resulted in enhanced saccharification yields. The ability to tune acidity through the use of protic ionic liquids offers a significant advantage in flexibility over dialkylimidazolium analogues.
Applied Microbiology and Biotechnology, 2010
Green Chem., 2016
The influence of substrate functionality and the cation–anion association in ionic liquid has bee... more The influence of substrate functionality and the cation–anion association in ionic liquid has been determined for the cleavage of the β-O-4 ether linkage prevalent in the lignin superstructure.
2499, Aug 14, 2012
ABSTRACT Ground lignocellulosic biomass (Miscanthus giganteus, pine (Pinus sylvestris) and willow... more ABSTRACT Ground lignocellulosic biomass (Miscanthus giganteus, pine (Pinus sylvestris) and willow (Salix viminalis)) was pretreated with ionic liquid–water mixtures of 1-butyl-3-methylimidazolium methyl sulfate and 1-butyl-3-methylimidazoliumhydrogen sulfate. A solid fraction enriched in cellulose was recovered, which was subjected to enzymatic hydrolysis. Up to 90% of the glucose and 25% of the hemicellulose contained in the original biomass were released by the combined ionic liquid pretreatment and the enzymatic hydrolysis. After the pretreatment, the ionic liquid liquor contained the majority of the lignin and the hemicellulose. The lignin portion was partially precipitated from the liquor upon dilution with water. The amount of hemicellulose monomers in the ionic liquid liquor and their conversion into furfurals was also examined. The performance of ionic liquid–water mixtures containing 1,3-dialkylimidazolium ionic liquids with acetate, methanesulfonate, trifluoromethanesulfonate and chloride anions was investigated. The applicability of the ionic liquid 1-butylimidazoliumhydrogensulfate for lignocellulose pretreatment was also examined. It was found that ionic liquid liquors containing methyl sulfate, hydrogen sulfate and methanesulfonate anions were most effective in terms of lignin/cellulose fractionation and enhancement of cellulose digestibility.
Green Chem., 2014
The cost of ionic liquids (ILs) is one of the main impediments to IL utilization in the cellulosi... more The cost of ionic liquids (ILs) is one of the main impediments to IL utilization in the cellulosic biorefinery, especially in the pretreatment step. In this study, a number of ionic liquids were synthesized with the goal of optimizing solvent cost and stability whilst demonstrating promising processing potential. To achieve this, inexpensive feedstocks such as sulfuric acid and simple amines were combined into a range of protic ionic liquids containing the hydrogen sulfate [HSO 4 ] − anion. The performance of these ionic liquids was compared to a benchmark system containing the IL 1-ethyl-3-methylimidazolium acetate [C 2 C 1 im][OAc].
Tetrahedron, 2010
Carbanions of 3-substituted-3-chloropropyl phenyl sulfones add to carbonyl groups of aldehydes to... more Carbanions of 3-substituted-3-chloropropyl phenyl sulfones add to carbonyl groups of aldehydes to produce aldol type adducts that undergo 1,5-intramolecular substitution giving 2,3,5-trisubstituted tetrahydrofurans. The effect of substituents in the 3-position of these sulfones on the relative rates of 1,3-intramolecular substitution of the corresponding γ-chlorocarbanions and their intramolecular addition are disclosed.
Physical Chemistry Chemical Physics, 2013
A range of methods for the computational prediction of experimentally derived α and β Kamlet-Taft... more A range of methods for the computational prediction of experimentally derived α and β Kamlet-Taft parameters, indicators of hydrogen bond (H-bond) acidity and basicity for ionic liquids (ILs) have been explored. Most usefully, a good correlation has been established between several simple and easily computed quantities which allow for a "quick bench-top" evaluation. More accurate, but also more sophisticated methods employing TD-DFT calculations involving the Kamlet-Taft dyes have been examined and evaluated. Importantly, these techniques open up the opportunity for pre-screening and a priori prediction of properties for ILs not yet synthesised. A key fundamental insight into IL H-bonds has been the determination of an estimate for the energy associated with replacing both neutral molecules in a H-bond with ionic molecules, thus forming the "doubly ionic" H-bond found in ILs.
The following two experiments were performed in duplicates in order to compare 1H-NMR spectroscop... more The following two experiments were performed in duplicates in order to compare 1H-NMR spectroscopy and HPLC for the quantitative analysis of HMF synthesised in this system. Rigorously dry environments were employed to ensure that both techniques were analysing under the same conditions. All reagents were purchased from Sigma-Aldrich whereas [C4C1im]Cl was synthesised and purified as described previously [52]. 1-butyl-3-methylimidazolium chloride ([C4C1im]Cl), cellulose (Sigmacell, 20 μm) and chromium(III) chloride hexahydrate (CrCl3·6H2O) are hygroscopic; therefore their handling and storage was carried out in a glovebox (N2 atmosphere). The glovebox water content was controlled in the presence of molecular sieves and the moisture and oxygen content was kept below 5 ppm. All handling was performed under air-free conditions, using standard Schlenk line techniques. The neat ionic liquid was dried under vacuum before use (24 h, 35 °C, 1.6 mbar). According to the conditions in Table S1,...
Green Chemistry
Softwood is an abundantly available feedstock for the bio-based industry, however, achieving cost... more Softwood is an abundantly available feedstock for the bio-based industry, however, achieving cost-effective sugar release is particularly challenging due to its guaiacyl-only lignin. Here, we report the highly effective pretreatment...
Faraday Discuss.
A wide variety of experimental and computational methods are used to probe sulfur atomic charges ... more A wide variety of experimental and computational methods are used to probe sulfur atomic charges in ionic liquids.
PLOS ONE
A number of ionic liquids have been shown to be excellent solvents for lignocellulosic biomass pr... more A number of ionic liquids have been shown to be excellent solvents for lignocellulosic biomass processing, and some of these are particularly effective in the production of the versatile chemical building block 5-hydroxymethylfurfural (HMF). In this study, the production of HMF from the simple sugar glucose in ionic liquid media is discussed. Several aspects of the selective catalytic formation of HMF from glucose have been elucidated using metal halide salts in two distinct ionic liquids, 1-butyl-3-methylimidazolium chloride and 1-butyl-3methylimidazolium hydrogen sulfate as well as mixtures of these, revealing key features for accelerating the desired reaction and suppressing byproduct formation. The choice of ionic liquid anion is revealed to be of particular importance, with low HMF yields in the case of hydrogen sulfate-based salts, which are reported to be effective for HMF production from fructose. The most successful system investigated in this study led to almost quantitative conversion of glucose to HMF (90% in only 30 minutes using 7 mol% catalyst loading at 120˚C) in a system which is selective for the desired product, has low energy intensity and is environmentally benign.
Green Chem., 2017
Cost-effective fractionation (pretreatment) of lignocellulosic biomass is necessary to enable its... more Cost-effective fractionation (pretreatment) of lignocellulosic biomass is necessary to enable its large-scale use as a source of liquid fuels, bio-based materials and bio-derived chemicals.
Inorganics, 2016
Cellulose is the single largest component of lignocellulosic biomass and is an attractive feedsto... more Cellulose is the single largest component of lignocellulosic biomass and is an attractive feedstock for a wide variety of renewable platform chemicals and biofuels, providing an alternative to petrochemicals and petrofuels. This potential is currently limited by the existing methods of transforming this poorly soluble polymer into useful chemical building blocks, such as 5-hydroxymethylfurfural (HMF). Ionic liquids have been used successfully to separate cellulose from the other components of lignocellulosic biomass and so the use of the same medium for the challenging transformation of cellulose into HMF would be highly attractive for the development of the biorefinery concept. In this report, ionic liquids based on 1-butyl-3-methylimidazolium cations [C 4 C 1 im] + with Lewis basic (X = Cl −) and Brønsted acidic (X = HSO 4 −) anions were used to investigate the direct catalytic transformation of cellulose to HMF. Variables probed included the composition of the ionic liquid medium, the metal catalyst, and the reaction conditions (temperature, substrate concentration). Lowering the cellulose loading and optimising the temperature achieved a 58% HMF yield after only one hour at 150 • C using a 7 mol % loading of the CrCl 3 catalyst. This compares favourably with current literature procedures requiring much longer reactions times or approaches that are difficult to scale such as microwave irradiation.
Journal of Visualized Experiments, 2016
Systematic and Applied Microbiology, 2009
Green Chemistry, 2014
The application of the protic ionic liquid 1-butylimidazolium hydrogen sulfate in the deconstruct... more The application of the protic ionic liquid 1-butylimidazolium hydrogen sulfate in the deconstruction (aka pretreatment) and fractionation of lignocellulosic biomass has been investigated. A cellulose rich pulp and a lignin fraction were produced. The pulp was subjected to enzymatic saccharification which allowed recovery of up to 90% of the glucan as fermentable glucose. The influence of the solution acidity on the deconstruction of Miscanthus giganteus was examined by varying the 1-butylimidazole to sulfuric acid ratio. Increased acidity led to shorter preteatment times and resulted in reduced hemicellulose content in the pulp. Addition of water to the ionic liquid resulted in enhanced saccharification yields. The ability to tune acidity through the use of protic ionic liquids offers a significant advantage in flexibility over dialkylimidazolium analogues.
Applied Microbiology and Biotechnology, 2010
Green Chem., 2016
The influence of substrate functionality and the cation–anion association in ionic liquid has bee... more The influence of substrate functionality and the cation–anion association in ionic liquid has been determined for the cleavage of the β-O-4 ether linkage prevalent in the lignin superstructure.
2499, Aug 14, 2012
ABSTRACT Ground lignocellulosic biomass (Miscanthus giganteus, pine (Pinus sylvestris) and willow... more ABSTRACT Ground lignocellulosic biomass (Miscanthus giganteus, pine (Pinus sylvestris) and willow (Salix viminalis)) was pretreated with ionic liquid–water mixtures of 1-butyl-3-methylimidazolium methyl sulfate and 1-butyl-3-methylimidazoliumhydrogen sulfate. A solid fraction enriched in cellulose was recovered, which was subjected to enzymatic hydrolysis. Up to 90% of the glucose and 25% of the hemicellulose contained in the original biomass were released by the combined ionic liquid pretreatment and the enzymatic hydrolysis. After the pretreatment, the ionic liquid liquor contained the majority of the lignin and the hemicellulose. The lignin portion was partially precipitated from the liquor upon dilution with water. The amount of hemicellulose monomers in the ionic liquid liquor and their conversion into furfurals was also examined. The performance of ionic liquid–water mixtures containing 1,3-dialkylimidazolium ionic liquids with acetate, methanesulfonate, trifluoromethanesulfonate and chloride anions was investigated. The applicability of the ionic liquid 1-butylimidazoliumhydrogensulfate for lignocellulose pretreatment was also examined. It was found that ionic liquid liquors containing methyl sulfate, hydrogen sulfate and methanesulfonate anions were most effective in terms of lignin/cellulose fractionation and enhancement of cellulose digestibility.
Green Chem., 2014
The cost of ionic liquids (ILs) is one of the main impediments to IL utilization in the cellulosi... more The cost of ionic liquids (ILs) is one of the main impediments to IL utilization in the cellulosic biorefinery, especially in the pretreatment step. In this study, a number of ionic liquids were synthesized with the goal of optimizing solvent cost and stability whilst demonstrating promising processing potential. To achieve this, inexpensive feedstocks such as sulfuric acid and simple amines were combined into a range of protic ionic liquids containing the hydrogen sulfate [HSO 4 ] − anion. The performance of these ionic liquids was compared to a benchmark system containing the IL 1-ethyl-3-methylimidazolium acetate [C 2 C 1 im][OAc].
Tetrahedron, 2010
Carbanions of 3-substituted-3-chloropropyl phenyl sulfones add to carbonyl groups of aldehydes to... more Carbanions of 3-substituted-3-chloropropyl phenyl sulfones add to carbonyl groups of aldehydes to produce aldol type adducts that undergo 1,5-intramolecular substitution giving 2,3,5-trisubstituted tetrahydrofurans. The effect of substituents in the 3-position of these sulfones on the relative rates of 1,3-intramolecular substitution of the corresponding γ-chlorocarbanions and their intramolecular addition are disclosed.
Physical Chemistry Chemical Physics, 2013
A range of methods for the computational prediction of experimentally derived α and β Kamlet-Taft... more A range of methods for the computational prediction of experimentally derived α and β Kamlet-Taft parameters, indicators of hydrogen bond (H-bond) acidity and basicity for ionic liquids (ILs) have been explored. Most usefully, a good correlation has been established between several simple and easily computed quantities which allow for a "quick bench-top" evaluation. More accurate, but also more sophisticated methods employing TD-DFT calculations involving the Kamlet-Taft dyes have been examined and evaluated. Importantly, these techniques open up the opportunity for pre-screening and a priori prediction of properties for ILs not yet synthesised. A key fundamental insight into IL H-bonds has been the determination of an estimate for the energy associated with replacing both neutral molecules in a H-bond with ionic molecules, thus forming the "doubly ionic" H-bond found in ILs.