This book summarises recent achievements in the use of ionic liquids in biomass processing as an alternative to conventional processes, particularly in the context of green chemistry. It features real-world case studies where high value-added products have been obtained using ionic liquid processing, demonstrating the practical applications of these technologies. The book concludes by assessing the development of further biorefineries with ionic liquids.
The book is an important reference for researchers and practising chemists, bringing readers up-to-date with current research in this field.
This book summarises recent achievements in the use of ionic liquids in biomass processing as an alternative to conventional processes, particularly in the context of green chemistry. It features real-world case studies where high value-added products have been obtained using ionic liquid processing, demonstrating the practical applications of these technologies. The book concludes by assessing the development of further biorefineries with ionic liquids.
The book is an important reference for researchers and practising chemists, bringing readers up-to-date with current research in this field.
Ionic Liquids in the Biorefinery Concept: Challenges and Perspectives
315
Ionic Liquids in the Biorefinery Concept: Challenges and Perspectives
315Hardcover
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Overview
This book summarises recent achievements in the use of ionic liquids in biomass processing as an alternative to conventional processes, particularly in the context of green chemistry. It features real-world case studies where high value-added products have been obtained using ionic liquid processing, demonstrating the practical applications of these technologies. The book concludes by assessing the development of further biorefineries with ionic liquids.
The book is an important reference for researchers and practising chemists, bringing readers up-to-date with current research in this field.
Product Details
| ISBN-13: | 9781849739764 |
|---|---|
| Publisher: | RSC |
| Publication date: | 10/02/2015 |
| Series: | Green Chemistry Series , #36 |
| Pages: | 315 |
| Product dimensions: | 6.15(w) x 9.20(h) x (d) |
About the Author
Read an Excerpt
Ionic Liquids in the Biorefinery Concept
Challenges and Perspectives
By Rafal Bogel-Lukasik
The Royal Society of Chemistry
Copyright © 2016 The Royal Society of ChemistryAll rights reserved.
ISBN: 978-1-84973-976-4
CHAPTER 1
The Biorefinery and Green Chemistry
JYRI-PEKKA MIKKOLA, EVANGELOS SKLAVOUNOS, ALISTAIR W. T. KING, AND PASI VIRTANEN
1.1 Introduction
1.1.1 Definitions
A biorefinery is a facility where different low-value renewable biomass materials are the feedstock to the processes where they are transformed, in multiple steps including fractionations, separations and conversions, to several higher-value bio-based products. Examples of these products can include fibres, food, feed, fine chemicals, transportation fuels and heat. A biorefinery can be formed by a single unit or can combine several facilities targeted for a single purpose that further process products as well as by-products or wastes of combined facilities. In biorefining one can find similarities to oil refining, with the exception that in oil refining the raw material comes from fossil resources. According to the International Energy Agency 'Biorefineries will contribute significantly to the sustainable and efficient use of biomass resources, by providing a variety of products to different markets and sectors. They also have the potential to reduce conflicts and competition over land and feedstock, but it is necessary to measure and compare the benefits of biorefineries with other possible solutions to define the most sustainable option.' Although it is possible to produce the same products in a biorefinery as in an oil refinery, this is not the target, which instead is to produce products which can replace the products from oil refining.
In the development of biorefinery processes, as well as any industrial processes, it is crucial for the future of the Earth that the new processes follow the principals of sustainable development and green chemistry. It is good to remind what these terms really mean.
The term 'sustainable development' was famously used by the Brundtland Commission in its report to the United Nations. In the report the term 'sustainable development' was defined as, 'development that meets the needs of the present without compromising the ability of future generations to meet their own needs.' In other words, it can be said that we have every right to utilize resources that the Earth provides to us for our needs as long as we make sure that future generations have the same possibility. The United Nations Millennium Declaration identified principles and treaties on sustainable development, including economic development, social development and environmental protection.
'Green Chemistry' is a term which is often applied when chemistry and chemical processes are defined as environmentally benign. Paul Anastas and John Werner developed and introduced widely accepted 12 principles of Green Chemistry. The following list briefly presents the principles which, if followed, would make chemical processes or products greener.
(1) Prevention: it is better to prevent waste than to treat or clean up waste after it has been created.
(2) Atom economy: synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
(3) Less hazardous chemical syntheses: where ever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
(4) Designing safer chemicals: chemical products should be designed to affect their desired function while minimizing their toxicity.
(5) Safer solvents and auxiliaries: the use of auxiliary substances should be made unnecessary wherever possible and harmless when used.
(6) Design for energy efficiency: energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
(7) Use of renewable feedstock: a raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
(8) Reduce derivatives: unnecessary derivatization should be minimized or avoided if possible, because such steps require additional reagent and can generate waste.
(9) Catalysis: catalytic reagents are superior to stoichiometric reagents.
(10) Design for degradation: chemical products should be designed so that at the end of their function they break down into harmless degradation products and do not remain in the environment.
(11) Real-time analysis for pollution prevention: analytical methodologies need to further develop to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
(12) Inherently safer chemistry for accident prevention: substances and the form of a substance used in chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions and fires.
Based on these Green Chemistry principles, Paul Anastas and Julie Zimmermann have also developed 12 principles of Green Engineering which should be kept in mind when developing new processes. The principles are briefly listed here, but more detailed information can be found from their publication.
(1) Inherent rather than circumstantial.
(2) Prevention instead of treatment.
(3) Design for separation.
(4) Maximize efficiency.
(5) Output-pulled versus input-pushed.
(6) Converse complexity.
(7) Durability rather than immortality.
(8) Meet need, minimize excess.
(9) Minimize material diversity.
(10) Integrate material and energy flows.
(11) Design for commercial 'afterlife'.
(12) Renewable rather than depleting.
1.1.2 Value of Major Biorefinery Products
1.1.2.1 Fibre Versus Chemicals
A major question concerning the definition of a 'biorefinery' comes when you consider existing fibre-lines and pulping technology. Is the modern kraft or sulfite mill to be considered as a biorefinery? If so, modern kraft mills can already be considered as 'green biorefineries'.
• The more modern mills use relatively harmless chemicals.
• Most of the materials are recycled so the net consumption of sulfur or caustic is very low.
• Importantly, the process is aqueous-based.
• With current totally chlorine free (TCF) bleaching stages, the production of chlorinated compounds in waste waters can be eliminated.
• Release of sulfides can also be minimized.
However, developing a green-field site with the most modern technology is a billion euro investment. The main product from kraft pulping is fibrous pulp. Bleached European softwood kraft pulp has a current value of ~0.8 &8364; per kg. The price has been known to fluctuate within an approximate range of ±0.5 &8364; per kg. Softwood kraft, in particular pine and spruce, are most valued due to the long fibre length. Dissolving pulp, produced through the sulfite pulping process or pre-hydrolysis kraft pulping, is even more valuable but is typically used for chemical production, e.g. cellulose acetate, carboxymethyl cellulose (CMC) and other esters or ethers. Therefore, this nicely fits the definition of a biorefinery. The fibrous properties of kraft pulp are the basis of its value, with high-quality graphical papers being the largest market for this pulp.
However, over the last 10 years demand for graphical papers has decreased, in particular in North America and Europe (i.e. the 'saturated' markets) and this lowers the value of pulp. This is due to competition mainly from China and Brazil and the use of graphical paper in general has decreased. This makes the use of fibrous biomass for production of energy and chemicals more attractive, despite the lower cost structure. In addition, unstable oil prices, global warming and eventually international commitment by governments to increase biofuels share in the transportation sector (EU 10% by 2020) has resulted in strong demand for bioethanol from biomass.
This is also reflected in the growing market price of bioethanol over the last 10 years, i.e. from about 0.3 &8364; per kg to about 0.6 &8364; per kg.6 This is uncertain to continue in the long term, as crude oil prices are currently low (at the time of writing), which will decrease bioethanol demand, and will also decrease demand from applications other than biofuels, i.e. as platform chemical for synthesis of green chemicals (diethyl ether, ethylene). Ethanol is a high volume bioproduct; however, its market value is considered low-to-average versus specialty chemicals from biomass, importantly in comparison to chemical pulp.
1.1.2.2 Bulk Chemicals
The production of bulk chemicals (>1000 tonnes per year) from biomass remains rather limited as the majority of organic chemicals and polymers are still derived from fossil-based feedstocks, predominantly oil and gas. Hence, most of the bulk chemicals originating from biomass do not show any dramatic increase in market value. However, a steady increase in demand is reported for lactic acid at 10% annual growth rate. Lactic acid can be cconverted e.g. to polylactic acid (PLA). PLA is mainly used in production of sustainable biopolymers for use in the packaging industry (thin films) but is also found in applications elsewhere. According to reports, European demand for PLA is currently 25 000 tonnes per year and could reach 650 000 tonnes per year in 2025. Furans derived from biomass, such as furfural derived from pentoses and 5-hydroxymethylfurfural (HMF) derived from hexoses, are one major platform feedstock of interest. Furfural has already been produced on an industrial scale for almost 100 years. The first industrial process for its production was by the Quaker Oat company where it was discovered that furfural could be obtained by sulfuric acid-catalysed dehydration of their oat hull stockpiles. A multitude of applications ensued. Nowadays, China produces the majority of the capacity, much of it from grass-based waste material. Most of these producers are dedicated towards furfural production as the main product. There are many estimates on the production of furfural, but they typically range between 300 000 and 800 000 tonnes per year and several smaller producers produce furfural as a secondary product. For example, Lenzing AG produces furfural on a 5000 tonnes per year scale during their pulping of beech wood. The main product for this process is their cellulosic pulp destined for textile production and only about 1% of the dry mass of the wood is converted to furfural. The market price of furfural ranges from roughly between 0.5 and 1.5 &8364; per kg and, not surprisingly, the prices are lowest in China. Hydroxymethyl furfural (HMF) by contrast, is not yet produced industrially due to the difficulty in accessing hexoses, difficulties in isolation as well as the instability of it at the process conditions. Most hexoses are bound up in softwood, which is much more recalcitrant than the abundant pentoses in grass species. Advanced techniques and enabling technologies, such as ionic liquids, are now required to allow us to access and selectively convert these saccharides whereby applications of both furans are likely to be wide ranging. Sequential catalytic dehydration, hydrolysis, hydrogenation and hydrogenolysis steps can be applied to convert them into a wide range of commodity chemicals, into potential biofuels and solvents.
One example of biofuel production is the Sylvan process (Figure 1.1). This process involves the hydrogenation of furfural to 2-methylfuran, dimerization or trimerization of 2-methylfuran and hydrogenation/hydrogenolysis to the fully saturated alkane.
This product can be used as a high-quality paraffinic diesel, but the cost is rather high and so it will likely only find immediate access for high-end engines. In general, the cost of furfural is still too high compared to crude oil to have utility as a fuel precursor. Thus, large process improvements need to be made to access fuel markets. Solvents, however, can have a high price. It has been suggested that 2-methyltetrahydrofuran (2-MTHF), accessible from hydrogenation of furfural, has potential to replace THF in certain applications and is a potential biofuel itself. ITLγITL-Valerolactone (GVL) is also now being studied intensively as a media for the conversion of polymeric pentoses and hexoses into oligomers and monomers. Thus, the media can be derived from the biomass feedstock. GVL can itself be also be converted into liquid transportation fuels (Figure 1.2).
This media unfortunately cannot access bulk hexoses bound up in softwood at lower temperatures. Increased temperatures do allow for almost complete solubilization of hexoses but lower temperature treatments do allow for fractionation of birch sawdust, resulting in high-purity cellulosic pulps.
1.1.2.3 Specialty Chemicals
Specialty chemicals from biomass are sold at relatively high prices (>10 &8364; per kg) due to their limited production (<1000 tonnes per year), 'green credentials', unique quality and properties. Demand for specialty chemicals by the industry (pharmaceutical, cosmetics, food sector) is growing stronger and so is their market value. Specialty chemicals fit well to specific, so-called 'niche', markets.
An example is Borregaard's vanillin produced by oxidation of sulfite lignin. The company has established a profitable business from vanillin as it is the exclusive producer and supplier of wood vanillin to the food industry. Vanillin derived from petrochemical sources is sold at much lower market prices.
1.1.3 Obtaining Pure Bio-Fractions
One of the major challenges in industrial biorefining is related to the need of fractionation and purification of the heterogeneous biomass streams to be processed; in fact, a majority of industrially and techno-economically feasible routes to chemicals, fuels and bio(composite) materials depend on the availability of pure, non-contaminated raw material fractions, whether those are carbohydrates, their polymers, fats and oils, various fragrances, nutraceuticals, extractives from lignocellulose or lignin. Further, the existence of various ash-elements (inorganic minerals) further complicates the task.
Throughout the years many processes were developed to facilitate the fractionation/separation targets: among others, the early acidic sulfite pulping, the alkaline sulfate pulping, mechanical pulping, various organosolv processes. More recently, ionic liquid or deep eutectic facilitated processes for biomass pre-treatments, fractionations, cellulose as well as hemicellulose separations and manipulations have all shown their potential in providing fractionated biomass components for further use. Indeed, if performing a simple SciFinder® search for the key words 'ionic liquid & biorefinery', this search string gives the very first paper as being published in 2008 with already 10 papers by the year 2014. From the early technologies based on (expensive) alkyl-imidazolium systems, the field has seen the rise of new concepts based on switchable ILs, strong organic bases and acid gases, the application of distillable ILs, as well as the use of bio-based, low-cost ILs, mixtures of 'cooperative' ionic liquids and deep eutectic solvents (DES), also in conjunction to radiofrequency and microwave heating or acoustic cavitation. The systems are not easily understood but the hydrogen bond basicity of the ionic liquid–water mixtures apparently relates to cellulose dissolution, lignin depolymerization and even to sugar yields obtained.
In addition, liquid CO2 (sub- or super-critical), gas-expanded liquids or simply water under relatively harsh conditions (often near-critical) offer other alternative processing possibilities. Nevertheless, it is estimated that around 60–80% of the processing costs are still related to the separation steps.
(Continues...)
Excerpted from Ionic Liquids in the Biorefinery Concept by Rafal Bogel-Lukasik. Copyright © 2016 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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Table of Contents
The Biorefinery and Green Chemistry;The Dissolution of Biomass in Ionic LiquidsTowards Pre-Treatment Approach;
Ionic Liquid Pre-Treatment of Lignocellulosic Bionass for Biofuels and Chemicals;
Biomass Hydrolysis in Ionic Liquids;
Relevance of Ionic Liquids and Biomass Feedstocks for Biomolecule Extraction;
Toxicity and Bio-Acceptability in the Context of Biological Processes in Ionic Liquid Media;
Synthesis of HMF in Ionic Liquids: Biomass-Derived Products;
Ionic Liquids as Efficient Tools for the Purification of Biomolecules and Bioproducts from Natural Sources;
Ionic Liquds in the Biorefinery: How Green and Sustainable Are They?;
Ionic Liquid-Based Processes in the
Biorefinery: A SWOT Analysis.