1 Sources of Industrial Chemicals 1.1 Introduction It would be difficult to nominate a manufacturing industry sector that did not use, in large or small quantities, purified chemicals as part of the process. The major manufacturing industries listed below are all dependent on industrial chemicals: 
oil refining 
plastics 
metal refining 
food processing 
paint 
pharmaceuticals 
agricultural chemicals (pesticides, herbicides etc) 
fertilisers 
acids (sulfuric, phosphoric) 
chlor‐alkalies The processing which result in a final commercial product are complex, varied and numerous. By way of example, consider plain white acrylic paint as an example. The three main components are water, polyvinyl acetate and titanium dioxide. In the form that they are used in the product, none can be simply “dug out of the ground”, even water. Figure 1.1 summarises the processes that produce the chemicals that go to make up white paint. Crude oil
Water
Black
sand
Ethene
Titanium
Purified
minerals
water
Vinyl
Titanium
acetate
dioxide
Polyvinyl
WHITE
acetate
PAINT
FIGURE 1.1 Processing steps to yield white paint And real paint includes many other minor components as well! 1. Sources of Industrial Chemicals 1.2 Sources There are more ten million chemical substances (elements and compounds) already known, and more are found or made every day. Most of these are laboratory curiosities, and it is really only several thousand that are of any commercial interest. Of these, the majority are organic. Where do the raw materials for all these chemicals come from? Since nothing can be created from nothing, they all come originally from the ground, air and water around us, as seen in Figure 1.1. For inorganic compounds and elements, their sources cover the entire spectrum of sources: ground, air and water. Iron ore which goes to make steel is dug out of the ground, argon gas which power the ICP spectrometer is isolated from the atmosphere and table salt comes from the ocean. For organic chemicals, the great bulk (more than 90%) come from the processed products of fossil fuels: crude oil, coal and natural gas. Inorganic chemicals Inorganic chemicals include: 
elements in their natural forms, especially metals 
concentrated acids and bases 
ionic salts Some of these can be simply extracted in the desired form from the environment, eg gold, platinum, sulfur (in some places), sodium chloride. More commonly, the extracted material is in an impure and chemically different form to that which is required. For example, iron ore dug out of the ground is of little use by itself, and must be turned into one of the many grades of iron or steel, but also needs separating from all the sand and dirt and other minerals. Some of the major sources of inorganic chemicals and their uses are listed in Table 1.1. In a later chapter, we will look at metals, including the refining processes to turn crude ores into metals. TABLE 1.1 Sources of inorganic chemicals Sources IPC Examples of Uses Phosphate rock Fertilisers, detergents Salt Chlorine, alkalies Limestone Lime, calcium carbide Sulfur Sulfuric acid Haematite Iron & steel Bauxite Aluminium Sodium carbonate Sodium hydroxide, cleaning formulations Sand Paint pigment (TiO2), specialised metals, glass 1.2 1. Sources of Industrial Chemicals Organic chemicals As mentioned above, fossil fuels, and particularly crude oil, is the major source of organic chemicals as diverse as plastics, food additives and fragrances. These processed chemicals are known as petrochemicals. At the present moment, about 10% of crude oil is used for chemical manufacture, most of the rest goes as fuel. Crude oil consists mainly of a complex mixture of hydrocarbons – alkanes, alkenes and aromatics – with a small proportion (< 5%) of oxygen, nitrogen and sulfur compounds. The latter are a problem because of their odour, interference with refining catalysts and pollution potential. The crude oil is refined to yield the various fuel fractions, but also a number of key primary petrochemicals, which include: 
ethene 
propene 
benzene 
toluene 
xylene (dimethylbenzene) 
naphthalene These chemicals are then converted into secondary petrochemicals, which are used to produce the wide range of organic compounds used across the industrial, commercial and domestic sectors. Coal and natural gas can also be processed to yield chemicals for uses other than fuel. The two most important coal conversion processes are carbonisation and gasification (see Table 1.2). TABLE 1.2 Coal conversion processes Process Conditions Products Carbonisation Heating in the absence of air at Mainly coke, some gases, and a mixture of aromatic compounds (benzene etc) and tar up to 1000C Gasification Heating in the presence of CO, CO2, CH4, H2 oxygen‐enriched air Chemicals from natural sources, particularly plants, are much less significant, but still important. In many instances in the pharmaceutical, cosmetic and pesticide sectors, compounds isolated from natural sources have been then made synthetically from petrochemicals. In others, the natural sources are the best (i.e. cheapest) way of producing certain substances, eg soap from animal fats. One of the major advantages of plant and animal sources of chemicals is their renewable nature – the ability to grow more of the same species in a relatively short space of time – unlike fossil fuel, new supplies of which cannot be “grown” in less than a few million years. Some of the most important natural sources of chemicals are: 
fats and oils from plants and animals for soap and glycerol and cooking oils 
sugar cane and sugar beet for sucrose 
rice, potatoes and similar crops for starch used in the production of ethanol and ethanoic acid 
timber for cellulose 
pyrethrum daisies for domestic insecticides 
various plants for essential oils used in fragrances and food flavouring (see Case Study) IPC 1.3 1. Sources of Industrial Chemicals CASE STUDY – Essential Oils Essential oils are mixtures of organic compounds extracted from plant sources by various methods, which are described below. They are called essential, not because they are necessary for life, but because they form the “essence” of the plant material. They represent the smell and flavour associated with many familiar plants and foods, eg rose, peppermint, lemon, lavender. They should not be confused with triglycerides oils, such as olive oil, which are very different chemically and physically. They are used in concentrated forms as a source of specific chemicals, but more commonly as the oil mixture in perfumes, other cosmetics such as powders, foods such as cakes, and these days, in aromatherapy products, such as candles. Most essential oils are a complex mixture of dozens of organic compounds – the odour of strawberries has been found to contain more than 300 compounds!! In most cases, there will be a few dominant compounds, eg clove oil is more than 80% eugenol. In most cases, the yield of oil from the plant source is extremely low: always less than < 1%, and more commonly, less than 0.1%. As a consequence, much effort has been put into making synthetic versions of the oils, which can be made more cheaply, but cannot hope to perfectly reproduce the complex mixture, having only the major components. More than 250 different plant sources are used as sources of essential oils, using various parts of the plants – leaves, flowers, seeds, fruit, bark, roots. In most cases, the extracted oil is used directly, but in some cases where one compound dominates the mixture, it may be extracted and processed further. The major extraction methods are: 
cold pressing – physical squeezing of the plant material to release the oily substances; citrus oils are usually produced in this way 
steam distillation – the plant material is suspended in boiling water, and the steam carries over with it volatile substances which would have too high a boiling point to be distilled by themselves; the majority of the spice and herb oils are produced this way 
solvent extraction – the plant material is pulped and mixed with a solvent, such ethanol or hexane, to dissolve the organic substances; the solvent is then removed by evaporation What problems could be encountered with each of these methods in terms of the extracted material? Cold Pressing Steam Distillation Solvent Extraction The compounds found in essentials oil cover the entire range of organic functional groups, from straight chain alkanes to nitrogen‐ and sulfur‐containing aromatics. A major class of compounds, of various functional groups, which are very important in essential oils are called terpenes (see below). IPC 1.4 1. Sourcces of Industrrial Chemicalss Terpeenes Terpeenes are wid
despread in nature, mainly in plantss as constitu
uents of esse
ential oils. M
Many terpen
nes are hydrocarbons, bu
ut oxygen‐co
ontaining com
mpounds such as alkan
nols, alkanalss or alkanonees (terpenoid
ds) are also ffound. Theirr building blo
ock is the h
hydrocarbon isoprene, C
CH2=C(CH3)‐C
CH=CH2. Terp
pene hydrocarbons thereefore have molecular formulas (C5H8)n, they are classified aaccording to
o the number FIGURE 11.2 oprene units (see Table 1
1.3). of iso
Structure of isoprene
TABLEE 1.3 Terpenes Nu
umber of isoprrene units Examplles mono
oterpenes 2 pinene, nerol, citral,, camphor, m
menthol, limo
onene sesqu
uiterpenes 3 nerolido
ol, farnesol diterp
penes 4 phytol, vitamin A1 triterrpenes 6 ne squalen
tetratterpenes 8 caroten
ne TABLEE 1.4 Structures of common mo
onoterpenes camphor ‐ pinene menthol citrone
ellal ‐pinene
limoneene
n up to 95%
% monoterpe
ene hydrocarrbons, usually limonene,, but others as well, e.g.. Citruss oils contain
lemon oil also co
ontains ‐terrpinene and ‐pinene, and orange oil o ‐ and ‐‐sinensal. The importantt ma‐determining componeents of citrus oils are functionalised terpenes an
nd aliphatic compoundss arom
(pred
dominantly ccarbonyl com
mpounds and
d esters), preesent only in relatively lo
ow concentraations. Thus,, severral methods are employyed to conceentrate citru
us oils on an
n industrial scale. s
The monoterpene
m
e hydro
ocarbon con
ntent is decreased by disstillation, liq
quid‐liquid partitioning between b
two
o immiscible
e solveents, or absorrption on a ccarrier such aas silica gel.
When citru
us fruits are juiced, the o
oil is pressed
d out of thee rind. This o
oil is separated from the
e mpounds. Th
he bulk of th
he oil is leftt juice,, and distilleed to recoveer certain flaavour and frragrance com
behin
nd and colleccted. This is food grade limonene. A
After the juicing process, the peels are conveyed
d to a ssteam extractor. This exxtracts more
e of the oil from the pee
el. When thee steam is co
ondensed, aa layer of oil floats on the surfaace of the condensed watter. This is te
echnical grad
de limonene. IPC 1.5 1. Sources of Industrial Chemicals In the past decade, the use of limonene has expanded tremendously. Much of the product goes into making paint solids, used to impart an orange fragrance to products, and used as a secondary cooling fluid. But the largest growth segment has been its use in cleaning products. This has occurred in both industrial uses and in household/institutional products. Limonene can be used either as a straight solvent, or as a water dilutable product. What You Need To Be Able To Do 



IPC define important terminology give examples of sources of organic and inorganic chemicals describe processes for extracting chemicals from natural materials outline the topics of essential oils and terpenes 1.6