Glycerol

The Renewable Platform Chemical

Mario Pagliaro

• Publisher: Elsevier
• Year: 2017
• Print ISBN:
  9780128122051
• eBook ISBN:
  9780128123331
• Topic: Biological Sciences
• Subtopic: Biotechnology
• Index: Biological Sciences

Glycerol: The Renewable Platform Chemical provides a valuable overview of the glycerol market, including industrial applications and sustainable production of glycerol. Replacing previous works on the subject, this useful resource describes glycerol, also known as glycerine, and its chemical derivatives, especially the new bioglycerol-derived products. The monograph also discusses how the industrial use of glycerol as raw material for producing commodity chemicals depends on broader scope and lower cost of the catalytic process used to convert glycerol of varying purity grades into valued monomers. New chapters on glycerol polymers, the use of glycerol as antifreeze, and its sustainable production offer relevant information for researchers and professionals from academics and industry alike. The book features new processes, such as low cost and biocompatible glycerol polymers as a major alternative to the conventional polymers, with the first practical applications now emerging in the biomedical and patient care markets. The book offers both a source of inspiration for new projects and a reliable source of information on how glycerol is replacing petrochemicals in many real world applications. - Features completely unique information and insight from leading expert Mario Pagliaro, including recent developments in the field, gathered from over a decade of intense R&D activities - Includes new chapters on the glycerol market, glycerol polymers, the use of glycerol in the cement and construction industries, its use an antifreeze, and its sustainable production - Contains reliable, accessible information appropriate for research chemists and chemical engineers in the chemical, oleochemicals, biodiesel, biotechnology and cement industries as well as in academia

Chapter 1

Properties, Applications, History, and Market

Abstract

Glycerol is an eminent oleochemical with unique chemical and physical properties, which originate a wealth of applications. The said properties are the consequence of a unique molecular structure with a three carbon skeleton with each carbon bearing a hydroxyl group. This chapter reviews the applications, history, and unique market of this chemical, whose supply is independent of demand as there is as much glycerol as biodiesel and fatty acids are manufactured every year across the world. New trends are identified and a looking ahead perspective is offered which takes into account the most recent developments in glycerol utilization.

Keywords

Glycerin; glycerol; glycerol market; oleochemicals; glycerol applications; glycerol derivatives

1.1 An Eminent Oleochemical

Glycerol (1,2,3-propanetriol) is an eminent oleochemical with unique chemical and physical properties, which originate a wealth of applications. Oleochemicals are chemicals derived from natural oils and fats of both vegetable or animal origin [1].

In the last two decades, both the oleochemical and biodiesel industries have grown steadily due to global demand of greener alternatives to petrochemicals and oil-derived fuels. The oleochemical capacity doubled in 10 years to current 12 million tonnes for acids and over 4.5 million tonnes for alcohols [2].

Glycerol provides the molecular skeleton of all lipids (triglycerides) in which it constitutes on average about 10% by weight of fatty matter from which it is liberated (Scheme 1.1) upon base-catalyzed hydrolysis (manufacture of soap and fatty acids) or transesterification reaction with methanol used to make biodiesel (Fatty Acid Methyl Ester, FAME) fuel.

Scheme 1.1 Both lipid hydrolysis and transesterification reactions yield 10 wt% glycerol as main coproduct.

Generally catalyzed by strong base the transesterification of oil and methanol affording FAME is an equilibrium reaction carried out with methanol in stoichiometric excess (Scheme 1.2).

Scheme 1.2 Transesterification of a triglyceride with methanol.

Since 2004 a large and rapidly increasing surplus of glycerol obtained as a byproduct in the manufacture of biodiesel fuel literally flooded the chemical market. In a concomitant and related trend, the oleochemical industry started to increase its capacity at unprecedented rate.

On June 2012 FELDA Global Ventures Holdings, a Malaysian palm oil and rubber company, raised up $3.1 billion from the world’s second largest initial public offering in that year (after Facebook) [3]. Since then, however, the price of crude palm oil (CPO) has plummeted from >$1000/tonne to >$500/tonne in early 2016 urging oleochemical companies to maximize the value extracted from the vegetable oil, including the main coproduct of fatty alcohol and fatty acids production.

For comparison the ratio between the 2015 turnover (€600 million) of a leading European oleochemical company and the number of employees (900), [4] translates into €600,000 value generation per employee, namely about half of the value typical of large petrochemical companies mentioned in the Introduction.

Maximizing the value of the products portfolio means to vertically integrate the product value chain downstream.

This is, e.g., what Malaysia’s KLK oleochemical producer has done. In 2010 the company bought a plant on the river Rhine in Germany (KLK Emmerich) where it manufactures a range of fatty acids, hydrogenated fatty acids, and glycerol. The initiative was successful and in 2015 the company purchased another plant in Dusseldorf where it produces oleochemicals from both vegetable-based as well as tallow-based lipids, close to key customers and vegetable oil suppliers. In this way the company was only partly affected by low CPO prices, and started to benefit from larger margins due to downstream products of considerable higher value (up to be 50% more lucrative per unit revenue) [5].

1.2 Properties and Main Applications

First isolated and called “the sweet principle of fats” by Scheele in Sweden in 1783 via distillation of the sweet supernatant liquid obtained by heating olive oil with calx lead (PbO) and water [6], glycerol was given its name by Chevreul who read his precise findings at France Académie des Sciences on November 2, 1813 [7]. Another French chemist, Pelouze, derived the empirical formula in 1836 [8].

Glycerol is a colorless, odorless, viscous liquid with a sweet taste, whose name originates from the Greek word for “sweet,” glykys. In its pure anhydrous condition and under normal atmospheric pressure glycerol has a specific gravity of 1.261 g/cm³, a melting point of 18.2°C and a boiling point of 290°C (Table 1.1).

Table 1.1

Selected Physicochemical Properties of Glycerol at 20°C

Chemical formula	C3H5(OH)3
Molecular mass	92.09382 g/mol
Density	1.261 g/cm³
Viscosity	1.5 Pa.s
Melting point	18.2°C
Boiling point	290°C
Food energy	4.32 kcal/g
Flash Point	160°C (closed cup)
Surface tension.	64.00 mN/m

Reproduced from CRC Handbook of Chemistry and Physics, 87th edn, Boca Raton (FL), 2006.

The three hydrophilic alcoholic hydroxyl groups are responsible for its complete miscibility with water and its highly hygroscopic nature. This, along with remarkable chemical and physical stability, compatibility with many other chemical materials, nontoxic, nonirritating and environmentally benign nature, explains why the authors of the first 20th century treaty published in 1945, [9] could describe some 1500 different commercial end uses of “glycerin,” as the latter term and “glycerine” are widely used in the literature to refer to glycerol.

A highly branched network of molecules connected by hydrogen bonds exists in all phases and at all temperatures. Molecular dynamics simulation suggests that on average 95% of molecules in the liquid are hydrogen bond connected, [10] leading to unusually high viscosity and boiling point. In detail, glycerol is a highly flexible molecule, forming both intra- and intermolecular hydrogen bonds. Out of 126 possible conformers, calculations indicate that in the lowest energy the hydroxyl groups form a cyclic structure with three internal hydrogen bonds [11]; whereas in the aqueous phase glycerol is stabilized by a combination of intramolecular hydrogen bonds and intermolecular solvation of hydroxyls.

Recently researchers in Iran carried out molecular dynamics to investigate the structural (radial distribution function and pair potential of mean force), dynamical (mean square displacement and transport properties), and thermodynamic properties (density, thermal expansion, and solubility parameter) of glycerol for 293.15–333.15 K at standard pressure [12]. For all temperatures, the simulated densities and viscosities are in a reasonable agreement with the experimental values within 0.4%, the lowest ever reported. The viscosity decreases logarithmically with increasing temperature. The simulated values for viscosity fitted well with the Arrhenius equation (R²=0.9981).

As temperature increases, the intermolecular interactions between the glycerol molecules weaken and therefore the viscosity decreases. An Arrhenius-type equation for viscosity, with calculated activation energy of 51.52 kJ/mol in good agreement with the experimental values of 55.76 kJ/mol and 58.33 kJ/mol, shows that the movement of glycerol molecules is a temperature-activated process in which a significant energy barrier that must be overcome before the fluid flows.

As mentioned previously, the unique properties of glycerol are exploited in a broad portfolio of direct uses.

• Pharmaceutical preparations

• Personal care products

• Humectant in tobacco (sprayed on all tobacco leaves prior to shredding)

• Cement multipurpose aid

• Animal feed conditioner

• Solvent (blended with propylene glycol) in liquid used in e-cigarettes

• Glycerin soaps

• Food and nutraceutical/diet low glycemic index ingredient

• Heat transfer fluid and antifreeze.

Refined glycerol is widely used in food, personal, and oral care products where it serves as an emollient, humectant, solvent, and lubricant in an ample variety of products. Glycerol has a very low glycemic index (3; common sugar has 65) and this makes it suitable as part of a diabetic diet as it does not raise blood sugar levels, though it has no particular advantage as a sweetener since it is 0.6 times as sweet as sugarcane and still 4.32 calories/g (in the United States, the Food and Drug Administration requires glycerol to be included in the Total Carbohydrates listed on the Nutrition Facts label).

Remarkably glycerol has unique human metabolism for which there is significant glycerol uptake in muscle tissue but no uptake by adipose tissue [13]. Finally like sorbitol and other polyols glycerol it is not metabolized by bacteria in the mouth that cause plaque and dental cavities. Having become cheaper than sorbitol, glycerol is replacing the former polyol in most toothpastes and mouthwashes.

As ingredient in skin care products, shaving cream...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• About the Author
• Preface
• Acknowledgments
• Introduction
• Chapter 1. Properties, Applications, History, and Market
• Chapter 2. C3-Monomers
• Chapter 3. Esters, Ethers, Polyglycerols, and Polyesters
• Chapter 4. Antifreeze and Multipurpose Cement Aid
• Chapter 5. Glycerol: A Key Platform Chemical of the Forthcoming Bioeconomy
• Index