Lignin and Lignans as Renewable Raw Materials

Chemistry, Technology and Applications

Francisco G. Calvo-Flores, José A. Dobado, Joaquín Isac-García, Francisco J. Martín-Martínez

• Publisher: Wiley
• Year: 2015
• Print ISBN:
  9781118597866
• Edition: 1
• eBook ISBN:
  9781118683514
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

Lignin and Lignans as Renewable Raw Materials: Chemistry, Technology and Applications

As naturally occurring and abundant sources of non-fossil carbon, lignin and lignans offer exciting possibilities as a source of commercially valuable products, moving away from petrochemical-based feedstocks in favour of renewable raw materials. Lignin can be used directly in fields such as agriculture, livestock, soil rehabilitation, bioremediation and the polymer industry, or it can be chemically modified for the fabrication of specialty and high-value chemicals such as resins, adhesives, fuels and greases.

Lignin and Lignans as Renewable Raw Materials presents a multidisciplinary overview of the state-of-the-art and future prospects of lignin and lignans. The book discusses the origin, structure, function and applications of both types of compounds, describing the main resources and values of these products as carbon raw materials.

Topics covered include:

• Structure and physicochemical properties
• Lignin detection methods
• Biosynthesis of lignin
• Isolation methods
• Characterization and modification of lignins
• Applications of modified and unmodified lignins
• Lignans: structure, chemical and biological properties
• Future perspectives

This book is a comprehensive resource for researchers, scientists and engineers in academia and industry working on new possibilities for the application of renewable raw materials.

For more information on the Wiley Series in Renewable Resources, visit www.wiley.com/go/rrs

Part I

Introduction

Chapter 1
Background and Overview

1.1 Introduction

Surviving on a small planet with limited resources to support our increasing global population is probably the greatest challenge humanity has faced so far. A large part of the problem is that our economy is driven by many technologies that are not sustainable at all. This necessity of developing sustainable technologies capable of addressing such challenges, together with the increasing concern over environmental protection and questions about future availability of petrochemical feedstock have spurred research and development toward new degradable materials from renewable resources, which are more environmentally friendly and sustainable than the currently used petroleum-based materials. Within this context, lignin, which appears as one of the polymeric components in plants, arises as a promising candidate for some of the desirable applications due to its rich chemical structure and its versatility.

For more than 100 years, scientists and engineers have made efforts to effectively remove lignin from wood when extracting cellulose in the pulping process.¹

In 1819, the term “lignin,” from the Latin word lignum meaning “wood” [1], was used for the first time by the Swiss botanist A. P. Candolle (1778–1841). Later, in 1839, A. Payen first described this “encrusting material” in wood. It took, however, about 20 years to accept the term “lignin” to refer to a material as it is currently understood [2].

An understanding of its chemical composition began in 1875, when Bente [3] demonstrated that the noncellulosic constituent of wood, namely lignin, was aromatic in nature. It was further characterized by Benedikt and Bamberger [4] in 1890, who described the methoxy group as typical of lignin chemical structure. Later in 1960, Brauns [5] stated: ‘the lignin building stone has a phenyl propane structure that may be regarded as proven, but how the stones are linked together in proto-lignin is still a mystery’. In addition, in 1920, Klason [6] postulated that lignin was an oxidation product of coniferyl alcohol, which was demonstrated in 1968 by Freudenberg [7].

Beyond this historical perspective on early years of lignin research, the rising interest on lignin today has made this natural polymer to go from a waste-side product to a promising source for chemicals, polymers, and many other applications. Lignin is the second most abundant natural polymer together with cellulose, and hemicellulose [8], which are the major sources of nonfossil carbon that make a special contribution to the carbon cycle [9]. Lignin is by far the most abundant substance composed of aromatic moieties in nature (see Table 1.1), and the largest contributor to soil organic matter.

Table 1.1 The most common plant phenolic compounds listed according to the count (content) of carbon atoms^a

Composition	Count of carbons	Types of phenolic substances
	6	Simple phenols, benzoquinones
	7	Phenolic acids/aldehydes
	8	Acetophenones, benzofurans
	9	Phenylpropanoids, benzopyranes (coumarins)
	10	Naphthoquinones
	11	Ageratochromenes (prekocens)
	12	Dibenzofurans, dibenzoquinones, biphenyls
	13	Dibenzopyranes, benzophenones, xanthones
	14	Stilbenes, anthraquinones, phenanthrenes
	15	Flavonoids, isoflavones, chalcones, aurones
	16	Norlignans (diphenylbutadienes)
	17	Norlignans (conioids)
	18	Lignans, neolignans
	30	Biflavonoids
	n	Condensed tannins (flavolans)
	n	Lignins
	n	Catecholmelanines

^a Adapted from refs [10–12].

Furthermore, lignin is an important component of secondary cell walls in plant cells, and it helps to maintain the integrity of the cellulose/hemicelluloses/pectin matrix that provides rigidity to the plant. Also, it provides internal transport of nutrients and water, and protects against attack by microorganisms. Apart from this key role in plants, lignin is also obtained from paper industry and other methods. Actually, the many different sources and types of lignin makes it more accurate to refer generically to “lignins” when referring to this multifaceted material. Its diversity also implies that interest in lignin arises from fields of knowledge ...

Table of contents

• Cover
• Wiley Series in Renewable Resources
• Title Page
• Copyright
• Table of Contents
• Dedication
• Series Preface
• Preface
• List of Acronyms
• List of Symbols
• Part I: Introduction
• Part II: What is Lignin?
• Part III: Sources and Characterization of Lignin
• Part IV: Lignins Applications
• Part V: Lignans
• Part VI: Outcome and Challenges
• Glossary
• Index
• End User License Agreement