High Pressure Technologies in Biomass Conversion: Volume 48 (Green Chemistry Series) - Hardcover

Hardcover

ISBN 10: 1782624856 ISBN 13: 9781782624851

Verlag: Royal Society of Chemistry, 2017

Inhaltsangabe

In recent years carbon dioxide has played an increasingly important role in biomass processing. This book presents the state-of-the-art of a range of diverse approaches for the use of carbon dioxide in biomass valorisation. The book explores cutting-edge research and important advances in green high-pressure technologies. It gives an overview of the most relevant and promising applications of high-pressure CO2-based technologies in biomass processing from the perspective of the biorefinery concept. Demonstrating the interdisciplinary aspects of high-pressure technologies from biology, chemistry and biochemical engineering areas, this book brings researchers and industrialists up to date with the latest advances in this field, including novel technologies for energy; biochemicals and materials production; and green chemical engineering processes.

Über diesen Titel

Über die Autorin bzw. den Autor

Rafal Lukasik is Research Associate at Laboratório Nacional de Energia e Geologia, I.P. (LNEG), Unit of Bioenergy, Portugal, where he leads a group focused on the green biorefinery concept. His principal scientific interests are in sustainable chemistry, extraction and separation with CO2, biomass processing with green solvents (carbon dioxide, ionic liquids), biorefinery, process design and optimization.

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In recent years carbon dioxide has played an increasingly important role in biomass processing. This book presents the state-of-the-art of a range of diverse approaches for the use of carbon dioxide in biomass valorisation.

The book explores cutting-edge research and important advances in green high-pressure technologies. It gives an overview of the most relevant and promising applications of high-pressure CO2-based technologies in biomass processing from the perspective of the biorefinery concept.

Demonstrating the interdisciplinary aspects of high-pressure technologies from biology, chemistry and biochemical engineering areas, this book brings researchers and industrialists up to date with the latest advances in this field, including novel technologies for energy; biochemicals and materials production; and green chemical engineering processes.

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High Pressure Technologies In Biomass Conversion

By Rafal M. Lukasik

The Royal Society of Chemistry

Copyright © 2017 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-1-78262-485-1

Contents

Chapter 1 Supercritical Fluids in Natural Product and Biomass Processing – An Introduction Manuel Nunes da Ponte, 
Chapter 2 Introduction to High Pressure CO2 and H2O Technologies in Sustainable Biomass Processing Ydna M. Questell-Santiago and Jeremy S. Luterbacher, 
Chapter 3 Pre-treatment of Biomass Using CO2-based Methods Luiz P. Ramos, Fayer M. De León Mayorga, Marcos H. L. Silveira, Célia M. A. Galvão and Marcos L. Corazza, 
Chapter 4 Enzyme-based Biomass Catalyzed Reactions in Supercritical CO2 Maja Leitgeb, Katja Vasic and Zeljko Knez, 
Chapter 5 Direct Hydrolysis of Biomass Polymers using High-pressure CO2 and CO2–H2O Mixtures Ana Rita C. Morais and Rafal M. Lukasik, 
Chapter 6 Processing of Lignocellulosic Biomass Derived Monomers using High-pressure and CO2–H2O Mixtures Gianluca Gallina, Pierdomenico Biasi, Cristian M. Piqueras and Juan García-Serna, 
Chapter 7 Efficient Transformation of Biomass-derived Compounds into Different Valuable Products: A "Green" Approach Maya Chatterjee, Takayuki Ishizaka and Hajime Kawanami, 
Chapter 8 Anti-solvent Effect of High-pressure CO2 in Natural Polymers Arturo Álvarez-Bautista and Ana Matias, 
Chapter 9 Perspectives of the Development of High-pressure Technologies in Biomass Processing Rafal M. Lukasik, 
Subject Index, 

CHAPTER 1

Supercritical Fluids in Natural Product and Biomass Processing – An Introduction

MANUEL NUNES DA PONTE

1.1 The Early History of Supercritical CO2 Extraction

Thomas Andrews's 1869 Bakerian Lecture "On the Continuity of the Gaseous and Liquid States of Matter" is widely credited to have established the term "critical point" to define the point in phase space where a liquid and its vapour attain the same density and become indistinguishable. In his lecture Andrews described, in detail, his experiments on carbonic acid (carbon dioxide). He stated that "On partially liquefying carbonic acid by pressure alone, and gradually raising at the same time the temperature to 88 °F, the surface of demarcation of the liquid and the gas became fainter, lost its curvature, and at last disappeared." Andrews goes on to establish the critical temperature of carbon dioxide as 30.92 °C, and to describe how, above this temperature there are no signs of phase separation, although the volume becomes extremely sensitive to pressure. He presents, in detail, the volume contractions obtained by small increases of pressure in the temperature region above the critical, up to 48.3 °C. He concludes that the volume exhibits a much greater contraction than it would if the perfect gas law was followed. He further concludes that, at higher pressures, the volume of the fluid takes similar values to those that might be calculated by using the thermal expansion of the liquid from below the critical temperature, that is, it behaves like a liquid.

This work inspired van der Waals to formulate his famous equation of state in his doctoral thesis "On the continuity of the gas- and liquid-state", presented in Leiden in 1873. This thesis had a profound effect in the development of molecular sciences in the late 19th century, ultimately leading to the award of the 1910 Nobel Prize for Physics to van der Waals.

A fluid in the pressure–volume–temperature region above the critical point where high compressibility and thermal expansivity were detected by Andrews is nowadays called a supercritical fluid. The high sensitivity of the density to small changes in pressure (or temperature) is the most distinctive property of supercritical fluids, and it forms the basis for their technological applications developed in the last forty years. It took, however, about a hundred years for Andrews's work on carbon dioxide to be translated into the industrial process known these days as supercritical fluid extraction.

Truly, through the years, processes like the high-pressure polymerization of ethylene, discovered by ICI in the 1930s, and the so-called ROSE (Residuum Oil Supercritical Extraction) process, developed in the petrochemical industry and using a light paraffinic solvent, like pentane, in supercritical conditions, can be counted as using supercritical fluid solvents. The massive work of Francis on mixtures of liquid carbon dioxide with hundreds of compounds, published in 1954 in one single paper, certainly contains much relevant information in conditions that may be deemed "near critical". But it was not until Zosel,working in the 1970s in the Max Planck Institute in Mulheim, Germany, used carbon dioxide to extract caffeine from coffee, and the technique went commercial, with an industrial plant inaugurated in 1978 by Kaffee HAG, that the field was really launched. The first symposium dedicated to the subject was held in Essen, Germany, in the same year, and influential books started to appear at the beginning of the 1980s, by Schneider, Wilke and Stahl and by McHugh and Krukonis. The development of the field was rapid, as it attracted researchers from many different areas. Ten years after the Essen Symposium, in 1988, a totally dedicated journal (The Journal of Supercritical Fluids) appeared, and the first International Symposium on Supercritical Fluids was held in Nice, France, with widespread international participation.

To a large extent most investigators were drawn to the area by the credentials of carbon dioxide as an environmentally safe solvent that could replace volatile organic solvents. This was the case with the first above-mentioned application, decaffeination, and in the second large scale commercial use, the extraction of hops for the beer industry. These days, most large-scale applications remain in natural products. One of the last processes to attain commercial status uses extraction volumes of the size (or bigger) of coffee decaffeination, and it cleans cork in the Spanish plant of the company Diam, described by Lack. The plant has recently undergone a duplication of capacity and the company is building a new plant in France, which might turn this process into the largest one in terms of the overall volume of the installed extractors.

Supercritical CO2 extraction has been thoroughly reviewed and explained in the 1994 book of Brunner. At about the same time, the second edition of the book of McHugh and Krukonis was published and a book edited by King and Bott described in detail extraction processes like caffeine from coffee or hops for the beer industry. With the appearance of these books, it may be said that the field attained full maturity and entered the array of well-known separation operations that can be applied to natural products and biomass.

1.2 The Role of Water in Supercritical CO2 Extraction

Extraction processes use carbon dioxide in essentially two sets of conditions: at high density (higher pressure), where it can dissolve the target solutes, and at low density (lower pressure), where it precipitates the solutes. The high compressibility of carbon dioxide at supercritical conditions allows its solvent power to be rapidly varied with relatively small changes in pressure (and with temperature, but changes in temperature are usually more difficult to implement).

Carbon dioxide is itself a bad solvent. As a small molecule with little polarity (no permanent dipole moment, a small quadrupole), it dissolves mainly non-polar molecules of small molar mass. This is exactly what is required, for instance, in the case of the cleaning of cork, where one contaminant must be removed, but most natural constituents of cork should be left untouched to maintain the properties that make it the undisputed leader of wine bottle closure materials. Low carbon dioxide pressures, of the order of 10 MPa, are therefore used in this process. However, in the extraction of caffeine, high pressures (30 MPa) and high solvent power are sought, due to the low solubility of this target substance in carbon dioxide. In this case, coffee beans are extracted before roasting, so that the aroma constituents, so characteristic of coffee, are not present yet (and therefore are not extracted).

In both cases, the presence of water in the biomass extraction cake is absolutely fundamental for the extraction to proceed. This requirement is "often misunderstood" – a quote from McHugh and Krukonis (ref. 8, p. 294). These authors explain in detail that in all cases of extraction of caffeine from coffee, and not only with carbon dioxide, moisture is essential to "free caffeine from its bound state in the coffee matrix". Caffeine is soluble in dry carbon dioxide, but it will not be available for extraction from the coffee matrix without the presence of water.

As all biomass contains water, these effects are in fact quite general in the extraction of natural products. For instance, Brunner, discusses at length the effect of the content of water in cocoa seed shells on the yields of carbon dioxide extraction of theobromine.

But, as pointed out by McHugh and Krukonis, those effects are often misunderstood and confounded with the role played by entrainers, modifiers or co-solvents, substances that are added to carbon dioxide to increase the solvent power of the supercritical solvent towards bigger or more polar molecules. Ethanol and propane have been the most researched co-solvents, but other small molecules, like methanol or acetone, have also been studied. One required property of these substances is that they must be mutually soluble with carbon dioxide in all proportions, at the pressures and temperatures of extraction, so that their concentration in the solvent may be controlled at the inlet of the extraction vessel and remain constant throughout the process. Typical concentrations used are 5 or 10% in mass.

Quite differently, water is scarcely soluble in supercritical carbon dioxide. Its solubility, in the range of pressures and temperatures commonly used in supercritical CO2 extraction, is of the order of 2 g per kg of carbon dioxide. It cannot therefore much enhance the solvent power of the gas. Dry carbon dioxide circulating in a moist plant matrix will soon become saturated in water. If water is present in large quantities in the biomass in the extractors, it can be dragged as a liquid, and eventually freeze in the decompression area, leading to tube blockages and other operational problems. The water content of the plant material to be subject to extraction must therefore be carefully balanced.

Even in the case where dried raw-materials are used, the water content of circulating carbon dioxide will be approximately constant. Reverchon et al. in their studies of the extraction of dried sage leaves measured a constant concentration of water in the carbon dioxide leaving the extractor of about 20% of the saturation value. They reasoned that, in the dried material, there were no free water molecules to be taken by the solvent, but many remained bound to the solid material. The constant value they measured would result from an adsorption–desorption equilibrium.

In recent times, the scientific interest on carbon dioxide+water mixtures was renewed, due to the considerable efforts currently developed in the study of Carbon Capture and Sequestration (CCS), a global warming mitigation scheme. The main interest is driven by the possibility that highly salted water reservoirs deep in the Earth may act as carbon dioxide sinks, and be useful for sequestration. Curiously, if these methods do live up to expectations and CCS is implemented, the enormous scale of the carbon dioxide that will be made available will certainly contribute to a renewal of the field of supercritical CO2.

1.3 Fractionation of Liquids

Supercritical CO2 fractionation of liquid mixtures has been intensively studied in the first years of the development of the supercritical fluid area. Contrarily to extraction from solids, which has benefited from the visibility given by reasonably large-scale applications (caffeine, hops), the fractionation of liquids still lacks a flag-carrying well-known commercial process to establish itself. In this process, tall and slim counter current columns are used to increase the number of separation stages. It has the advantage that itmay be processed continuously, as in a liquid–liquid separation, all feed materials being liquid.

As carbon dioxide is generally a weak solvent, this type of fractionation may be used for difficult separations in liquid mixtures. It has been proposed for the fractionation of valuable substances in natural products, like vegetable food oils, fish oils, wine and beer. Commercial applications are reported for small-scale productions, as in the case of the purification of omega 3 fatty acids (see, for instance, www.solutex.es). Brunnerdescribes the fundamentals and design techniques in great detail and Brunner and Machado have more recently provided a good example of the application of fatty acid fractionation, while providing a thorough recollection of previous work in supercritical CO2 fractionation.

Very recently, Bejarano et al. have thoroughly reviewed the field. In their paper, they present a comprehensive list of existing facilities throughout the world and describe, in detail, the different types of fractionation columns used so far, as well as the data needed to design and operate them.

1.4 Supercritical H2O

One major event in the supercritical fluid field was the appearance of supercritical water. It developed as a second important focus of detailed study, so much so that the whole field is now supported on two pillars, supercritical CO2 and supercritical H2O, with little activity dedicated to other substances. Water has, however, a high critical temperature (374 °C) and pressure (22 MPa), and working with it involves much harsher conditions than with supercritical CO2. Moreover, the changes induced by temperature increases on liquid water solvent properties are much more drastic than for liquid carbon dioxide. In fact, the three-dimensional hydrogen bond network, characteristic of water at room temperatures (responsible for its high solvent power towards ionic salts) is gradually disturbed by molecular agitation as the temperature rises. It is almost completely disrupted at temperatures well below the critical, where water starts to behave as a highly polar, but, paradoxically, "non-aqueous" solvent. Supercritical water can dissolve hydrocarbons, a positive property, but precipitates ionic salts, which constitutes one of the main problems for its devised applications. This evolution of the solvent power of water with temperature may be summarized by its dielectric constant, which changes from around 80 at room temperature and pressure to about 6 just above the critical conditions.

Another property that also changes drastically with temperature is the ionic product Kw, which increases by several orders of magnitude from room to critical temperature. This means that hydrolysis reactions are highly facilitated in supercritical H2O, as pointed out by Weingartner and Franck. The corrosion of piping and reactor surfaces has therefore represented an important drawback in the development of supercritical H2O applications.

One of the most studied processes has been supercritical H2O oxidation (SCWO), mainly focused on the destruction of organic residues. Water (in supercritical conditions)mixes in all proportions with oxygen, and complete oxidation of carbon into carbon dioxide and hydrogen into water can be very rapidly obtained at the highly reactive conditions of supercritical H2O. Toxic by-products, such as dioxins, of more classical incineration processes are thus avoided. However, when other elements are present in the residues, such as chlorine, sulfur or phosphorus, acids (hydrochloric, sulfuric, phosphoric) or the corresponding salts are formed, this leads to the two most important problems of SCWO: corrosion and plugging by salt deposition.

Marrone has recently reviewed the commercial activity in this area. He thoroughly lists the companies active in the market and the facilities currently in operation, as well as those that, after some period of activity, have been closed. It is very interesting to note the high "mortality" rate of both companies and facilities, mostly because operations were plagued by technical problems and could not attain specifications. But it is also pointed out that new companies are entering the market and that SCWO continues to be an attractive technology.

Supercritical H2O has been used as a medium for many interesting reactions, especially to produce materials. Adschiri et al. reviewed the activity at an industrial scale in Japan and Korea. In the handling of biomass, supercritical and hot subcritical water have been proposed as advantageous media to produce biofuels. These highly reactive "hydrothermal media" promote the depolymerisation of the main biomass constituents, leading to the production of either liquid or gaseous fuels, depending on operational conditions and biomass composition.

1.5 Perspectives

Forty years on from the initial thrust focusing on supercritical CO2 and extraction of natural products, the field has diversified into a wide range of areas of study and many applications, which either have already gone commercial or are waiting to be adopted. A rough measure of this diversity may be given by the 2009 special edition issue of The Journal of Supercritical Fluids, commemorating its 20th anniversary. 32 review papers were published, covering the whole field. They may be loosely divided in the following topics: supercritical H2O – 8; processing of polymers, mostly with carbon dioxide – 6; other materials – 2; separations (extraction, fractionation, chromatography) with supercritical CO2 – 6; colloids, microemulsions and particle formation – 5; reaction in supercritical CO2 – 4; and energy applications – 1.

Although the role of natural products and biomass is no longer the dominant focus of the field, it continues to play an important part in recent developments. The properties of supercritical fluids as green solvents are still an attractive feature, as seen in the recent review of Farrán et al. on green solvents in carbohydrate chemistry.

The combination of carbon dioxide with hydrothermal technologies, as those proposed by Brunner and collaborators for ethanol production or King for multiple separations from plant material, represent technological platforms that can be used in a decentralized manner for sustainable use of biomass. The inspirational view of Arai, Smith and Aidaon sustainability and supercritical H2O processes may, in reality, be extended to the whole field.

(Continues...)

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Details zur Ausgabe

• Verlag: Royal Society of Chemistry
• Erscheinungsdatum: 2017
• Sprache: Englisch
• ISBN 10: 1782624856
• ISBN 13: 9781782624851
• Einband: Tapa dura
• Anzahl der Seiten: 213
• Herausgeber: Łukasik Rafał M
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar