Towards Process-Resilient Lignin-Derived Activated Carbons for Hydrogen Storage Applications

Activated carbons are promising sorbents that have been heavily investigated for the physisorptive storage of hydrogen. The industrial process for production of activated carbons is finely tuned and requires a reliable and uniform feedstock. While the natural biopolymer lignin, a by-product of several industries, has received increasing interest as a potentially sustainable and inexpensive activated carbon feedstock, the ratio of the three aromatic monomers (S, G, and H) in lignin can be heavily affected by the lignin source and growing conditions. The aromatic ratio is known to influence the thermal behavior of the polymer, which could be problematic for production of consistent activated carbons at scale. With the goal of improving the consistency of activated carbons produced from lignins derived from different feedstocks, here we present a route to limiting the influence of lignin feedstock on activated carbon porosity and performance, resulting in a carbonization process that is resilient to changes in lignin source. Two different types of organosolv lignin (representing high S-unit content and high G-unit content feedstocks) were investigated. Resulting activated carbons exhibited a high surface area (> 1000 m2·g-1) with consistent adsorptive properties and reasonable hydrogen uptake of up to 1.8 wt.% at 1 bar and -196 °C. These findings indicate that low temperature carbonization conditions can be used to produce a consistent carbon material using organosolv lignins from any source, paving the way for more widespread use of lignin in large-scale carbon production

Toward Process-Resilient Lignin-Derived Activated Carbons for Hydrogen Storage Applications

Activated carbons are promising sorbents that have been heavily investigated for the physisorptive storage of hydrogen. The industrial process for production of activated carbons is finely tuned and requires a reliable and uniform feedstock. While the natural biopolymer lignin, a by-product of several industries, has received increasing interest as a potentially sustainable and inexpensive activated carbon feedstock, the ratio of the three aromatic monomers (S, G, and H) in lignin can be heavily affected by the lignin source and growing conditions. The aromatic ratio is known to influence the thermal behavior of the polymer, which could be problematic for production of consistent activated carbons at scale. With the goal of improving the consistency of activated carbons produced from lignins derived from different feedstocks, here we present a route to limiting the influence of lignin feedstock on activated carbon porosity and performance, resulting in a carbonization process that is resilient to changes in lignin source. Two different types of organosolv lignin (representing high S-unit content and high G-unit content feedstocks) were investigated. Resulting activated carbons exhibited a high surface area (> 1000 m2·g-1) with consistent adsorptive properties and reasonable hydrogen uptake of up to 1.8 wt.% at 1 bar and -196 °C. These findings indicate that low temperature carbonization conditions can be used to produce a consistent carbon material using organosolv lignins from any source, paving the way for more widespread use of lignin in large-scale carbon production

How to save the world with Leerdammer cheese:Engineering nanoporous materials for clean water

Water is the single most important substance on Earth, it is vital for all known forms of life. Water scarcity however, means that one in five people on this planet lack access to clean, safe drinking water. Water scarcity is not just caused by an uneven distribution of water resources, but also a severe decrease in water quality. Declining water quality has been recognised by the United Nations as a rapidly emerging issue, one that will have a large impact on both developing and developed countries, including the United Kingdom. The decline in water quality is due to an increase in the number of chemicals, including pharmaceuticals and pesticides, entering the water supply. Research is now focusing on cheaper and more efficient methods to remove these contaminants.One potential solution is to use a class of materials which have a lot in common with Leerdammer cheese. These so-called nanoporous materials are not usually bright yellow, and neither are they really edible. They are however full of thousands of nano-scale sized holes or pores (a nanometre is one millionth of a millimetre), and it is this property which makes them potentially world-saving. Molecules are able to stick to the surface of nanoporous materials, by a process known as adsorption. On passing untreated water through this type of material, undesirable molecules can be stored on the materials surface, and removed from the water supply. One type of nanoporous material is known as activated carbon, and it is already used in water treatment. These materials are one of the oldest known and most efficient water treatment methods. Despite this, current activated carbon materials are unable to completely remove all contaminants from the water supply. Only a limited amount of certain contaminants, such as the pesticide metaldehyde, are removed using current activated carbon materials. Our research focuses on the development of novel activated carbon materials, which will be able to remove these challenging contaminants from the water supply. The performance of nanoporous materials is affected by several factors. We are investigating the optimal pore size and shape for our Leerdammer cheese-like materials. Our research focuses on upgrading a waste product, called lignin, into an activated carbon. Lignin is a component in biomass, and is produced in large quantities by the paper pulping industry. The wide-spread availability and low cost of lignin makes this a promising feedstock for industrial-scale production of novel activated carbons. Uniquely the structure of lignin depends on the type of plant it is extracted from. This leads to the exciting possibility we will be able to tune the activated carbon structure, including the size and shape of its pores, simply by adjusting the feedstock. Further, this could enable us to selectively remove some of the more challenging contaminants from the water supply, by producing this type of tailored activated carbon. Severely declining water quality is fast becoming an urgent problem. Our research is working towards the producing more efficient Leerdammer cheese-like materials to help save the world.<br/

Application of Experimental Design to Hydrogen Storage: Optimisation of Lignin-Derived Carbons

Lignin is a significant by-product of the paper pulping and biofuel industries. Upgrading lignin to a high-value product is essential for the economic viability of biorefineries for bioethanol production and environmentally benign pulping processes. In this work, the feasibility of lignin-derived activated carbons for hydrogen storage was studied using a Design of Experiments methodology, for a time and cost-efficient exploration of the synthesis process. Four factors (carbonisation temperature, activation temperature, carbonisation time, and activation time) were investigated simultaneously. Development of a mathematical model allowed the factors with the greatest impact to be identified using regression analysis for three responses: surface area, average pore size, and hydrogen uptake at 77 K and 1 bar. Maximising the surface area required activation conditions using the highest settings, however, a low carbonisation temperature was also revealed to be integral to prevent detrimental and excessive pore widening. A small pore size, vital for efficient hydrogen uptake, could be achieved by using low carbonisation temperature but also low activation temperatures. An optimum was achieved using the lowest carbonisation conditions (350 °C for 30 min) to retain a smaller pore size, followed by activation under the severest conditions (1000 °C for 60 min) to maximise surface area and hydrogen uptake. These conditions yielded a material with a high surface area of 1400 m2 g−1 and hydrogen uptake of 1.9 wt.% at 77 K and 1 bar

How to save the world with Leerdammer cheese:Engineering nanoporous materials for clean water

Water is the single most important substance on Earth, it is vital for all known forms of life. Water scarcity however, means that one in five people on this planet lack access to clean, safe drinking water. Water scarcity is not just caused by an uneven distribution of water resources, but also a severe decrease in water quality. Declining water quality has been recognised by the United Nations as a rapidly emerging issue, one that will have a large impact on both developing and developed countries, including the United Kingdom. The decline in water quality is due to an increase in the number of chemicals, including pharmaceuticals and pesticides, entering the water supply. Research is now focusing on cheaper and more efficient methods to remove these contaminants.One potential solution is to use a class of materials which have a lot in common with Leerdammer cheese. These so-called nanoporous materials are not usually bright yellow, and neither are they really edible. They are however full of thousands of nano-scale sized holes or pores (a nanometre is one millionth of a millimetre), and it is this property which makes them potentially world-saving. Molecules are able to stick to the surface of nanoporous materials, by a process known as adsorption. On passing untreated water through this type of material, undesirable molecules can be stored on the materials surface, and removed from the water supply. One type of nanoporous material is known as activated carbon, and it is already used in water treatment. These materials are one of the oldest known and most efficient water treatment methods. Despite this, current activated carbon materials are unable to completely remove all contaminants from the water supply. Only a limited amount of certain contaminants, such as the pesticide metaldehyde, are removed using current activated carbon materials. Our research focuses on the development of novel activated carbon materials, which will be able to remove these challenging contaminants from the water supply. The performance of nanoporous materials is affected by several factors. We are investigating the optimal pore size and shape for our Leerdammer cheese-like materials. Our research focuses on upgrading a waste product, called lignin, into an activated carbon. Lignin is a component in biomass, and is produced in large quantities by the paper pulping industry. The wide-spread availability and low cost of lignin makes this a promising feedstock for industrial-scale production of novel activated carbons. Uniquely the structure of lignin depends on the type of plant it is extracted from. This leads to the exciting possibility we will be able to tune the activated carbon structure, including the size and shape of its pores, simply by adjusting the feedstock. Further, this could enable us to selectively remove some of the more challenging contaminants from the water supply, by producing this type of tailored activated carbon. Severely declining water quality is fast becoming an urgent problem. Our research is working towards the producing more efficient Leerdammer cheese-like materials to help save the world.<br/

Influence of Aromatic Structure on the Thermal Behaviour of Lignin

Lignin, a natural biopolymer and abundant by-product, is a particularly promising feedstock for carbon-based materials and a potentially sustainable alternative to phenolic resins, which are typically derived from crude oil. The source and method used to isolate lignin have a large impact on the thermal properties of the polymer, and can affect resultant materials prepared from lignin. Previous investigations into lignin characterisation often utilise a variety of feedstocks and isolation methods, which can make robust comparisons challenging. We present a systematic investigation into the chemical composition of lignins extracted using an identical Organosolv isolation method but from different biomass feedstocks: hemp hurds, eucalyptus chips, flax straw, rice husk and pine. We show how the aromatic structure of lignin can affect the thermal behaviour of the polymer, which correlates to the structure of resulting carbons. Carbons from lignins with a high syringyl unit content display a pronounced foaming behaviour which, on activation, results in a high-surface area material with hierarchical porosity

The effect of precursor structure on porous carbons produced by iron-catalyzed graphitization of biomass

This paper reports a systematic study into the effect of different biomass-derived precursors on the structure and porosity of carbons prepared via catalytic graphitization. Glucose, starch and cellulose are combined with iron nitrate and heated under a nitrogen atmosphere to produce Fe3C nanoparticles, which catalyze the conversion of amorphous carbon to graphitic nanostructures. The choice of organic precursor provides a means of controlling the catalyst particle size, which has a direct effect on the porosity of the material. Cellulose and glucose produce mesoporous carbons, while starch produces a mixture of micro- and mesopores under the same conditions and proceeds via a much slower graphitization step, generating a mixture of graphitic nanostructures and turbostratic carbon. Porous carbons are critical to energy applications such as batteries and electrocatalytic processes. For these applications, a simple and sustainable route to those carbons is essential. Therefore, the ability to control the precise structure of a biomass-derived carbon simply through the choice of precursor will enable the production of a new generation of energy materials

Polynuclear complexes as precursor templates for hierarchical microporous graphitic carbon: An unusual approach

YesA highly porous carbon was synthesized using a coordination complex as an unusual precursor. During controlled pyrolysis, a trinuclear copper complex, [CuII3Cl4(H2L)2]·CH3OH, undergoes phase changes with melt and expulsion of different gases to produce a unique morphology of copper-doped carbon which, upon acid treatment, produces highly porous graphitic carbon with a surface area of 857 m2 g–1 and a gravimetric hydrogen uptake of 1.1 wt % at 0.5 bar pressure at 77 K.EPSRC (EP/R01650X/1 for VPT, and EP/E040071/1 for MT) and the University of Bristo