Petrochemicals are chemicals made from petroleum or natural gas. Primary petrochemicals are divided into three groups, depending on their chemical structure:
Olefins include ethylene, propylene, and butadiene. Ethylene and propylene are important sources of industrial chemicals and plastics products. Butadiene is used in making synthetic rubber. Olefins are produced by cracking.
Aromatic petrochemicals include benzene, toluene, and xylenes. Benzene is used in the manufacture of dyes and synthetic detergents. Toluene is used in making explosives. Manufacturers use xylenes in making plastics and synthetic fibers. Aromatics are produced by reforming.
Synthesis gas (SynGas) is a mixture of carbon monoxide and hydrogen, and is used to make the petrochemicals ammonia and methanol. Ammonia is used in making fertilizers and explosives, where methanol serves as a source for other chemicals.
The primary petrochemicals are not end products, but form building blocks for a wide range of materials. Therefore, each primary petrochemical gives name to a chain of reactions leading to those materials. There are almost 200 petrochemicals that can be described this way. There are more processes than end products, as each product may require multiple steps, so an exhaustive list would not fit within this book. Instead, we will focus on the main chains, properties and uses of the most important compounds and a few key processes for this overview.
Many of these processes are based on polymerization, which means that it is based on processes that first form monomers then let these bind together to form polymers as long chains or a three dimensional network. Compounds whose names start with “poly” are generally polymers, but many other trade names, such as nylon which is a generic name for a family of polyamides, are polymers.
Petrochemicals are often made in clusters of plants in the same area. These plants are often operated by separate companies, and this concept is known as integrated manufacturing. Groups of related materials are often used in adjacent manufacturing plants, to use common infrastructure and minimize transport.
- 1 Aromatics
- 1.1 Xylene and polyester chain
- 1.2 Toluene, benzene, polyurethane and phenolic chain
- 1.3 Benzene and styrenic chain, derivatives
- 1.4 Olefins
- 1.5 Ethylene, derivatives
- 1.6 Propylene, derivatives
- 1.7 Butadiene, butylenes, and pygas, derivatives
- 1.8 Synthesis gas (syngas)
- 1.9 Methanol based products
- 1.10 Ammonia based products
- 2 References
Aromatics, so called because of their distinctive perfumed smell, are a group of hydrocarbons that include benzene, toluene and the xylenes. These are basic chemicals used as starting materials for a wide range of consumer products. Almost all aromatics come from crude oil, although small quantities are made from coal.
Xylene and polyester chain
One of the forms of xylene, paraxylene, is used to make polyesters which have applications in clothing, packaging and plastic bottles. The most widely-used polyester is polyethylene terephthalate (PET), used in lightweight, recyclable soft drink bottles (30% of production), as fibers in clothing (60% of production), as a filling for anoraks and duvets, in car tire cords and conveyor belts. It can also be made into a film that is used in video and audiotapes and X-ray films. Polyester makes up about 18% of world polymer production and is the third most-produced polymer; polyethylene (PE) and polypropylene (PP) are first and second, respectively. Metaxylene is an isomer of mixed xylene. It is used as an intermediate in the manufacture of polyesters for coatings, inks, reinforced plastics and packaging applications.
Unsaturated polyester is used over a broad spread of industries, mainly the construction, boat building, automotive and electrical industries. In most applications, they are reinforced with small glass fibers. Hence, these plastics are commonly referred to as glass reinforced plastics (GRP). Initially a liquid, the resin becomes solid by cross-linking chains. A curative or hardener creates free radicals at unsaturated bonds, which propagate in a chain reaction to adjacent molecules, linking them in the process. Styrene is often used to lower viscosity and evaporates during hardening, where the cross linking releases heat.
Orthoxylene is an isomer of mixed xylene. It is primarily used in plasticizers (primarily in flexible polyvinyl chloride (PVC) material to make it more flexible), medicines and dyes. Alkyd resins are a group of sticky synthetic resins used in protective coatings and paints.
Toluene, benzene, polyurethane and phenolic chain
Tolune diisocyanate (TDI) is an isocyanate used in the production of polyurethanes for flexible foam applications, ranging from furniture, bedding, and carpet underlay to transportation and packaging. TDI is also used in the manufacture of coatings, sealants, adhesives and elastomers. Nylon is a generic designation for a family of synthetic polymers known generically as aliphatic polyamides derived from benzene, first produced in 1935 by DuPont. Nylon can be used to form fibers, filaments, bristles, or sheets to be manufactured into yarn, fabric, and cordage; and it can be formed into molded products. Nylon is tough, elastic and strong, and it has high resistance to wear, heat, and chemicals. It is generally used in the form of fine filaments in such articles as hosiery and sports equipment, e.g., parachutes; but its applications also include engineering plastics for cars, toys, healthcare products, carpets, roller-blade wheels and ship sails.
There are many varieties of nylon that have their own characteristic properties. Nylon plastics are used for making such products as combs, brushes and gears. Nylon yarns, on the other hand, are used for making nylon fabrics. When talking about nylon textile, there are two types that are mostly prevalent in the market: nylon 6-6 (also written as nylon 6,6) and nylon 6.
Phenol is an aromatic alcohol, mainly used as an intermediate in organic synthesis. Essentially, it serves as a raw material for the production of bisphenol A, phenolic resins, alkylphenols and caprolactam. It is a poisonous, acidic compound obtained from coal tar or benzene and used mainly as a disinfectant or antiseptic, carbolic acid; any hydroxyl derivative of benzene. Phenolic resins are manufactured from phenol. They are used in wood products and molding powders applications, and also have a wide range of applications on the electrical, mechanical and decorative markets, in the automotive industry, in building and construction, in thermal insulation products and in foundry industry products.
Epoxy resin is a flexible resin made using phenols and used chiefly in coatings, adhesives, electrical laminants and composites for its excellent adhesion, strength and chemical resistance. Polycarbonates are a particular group of thermoplastics. They are easily worked, molded, and thermoformed; as such, these plastics are very widely used in modern manufacturing. Polycarbonate is becoming more common in housewares, as well as laboratories and in industry. It is often used to create protective features, for example, in banks as well as vandal-proof windows and lighting lenses for many buildings.
Benzene and styrenic chain, derivatives
Polystyrene is solid plastic made from polymerized styrene. It is the second most common plastic and used in a wide variety of everyday pplications, from coffee cups to CD jewel boxes. It is a thermoplastic polymer in a solid “glassy” state at room temperature, but flows if heated above about 100 °C. It becomes solid again when cooled. This allows polystyrene to be extruded, molded and vacuum-formed in molds with fine detail and high finish.
Styrene-acrylonitrile (SAN) is like polystyrene but offers higher thermal resistance and is therefore used mainly in the automotive, electrical and electronics industry, as well as in household applications and building products.
Acrylonitrile-butadiene-styrene (ABS) is a tough, heat-resistant and impactresistant thermoplastic, with the acrylonitrile providing heat resistance and the styrene units offering rigidity. It is widely used for appliance and telephone housings, luggage, sporting helmets, pipe fittings and automotive parts.
Styrene-butadiene rubber (SBR) is a rubber manufactured from styrene. Because of its excellent abrasion resistance, it is widely used in automobile and truck tires, as well as for carpet backing and paper coating. About 50% of a car tire is made from SBR. Other applications are in belting, flooring, wire and cable insulation and footwear.
Olefins are petrochemical derivatives produced by cracking feed stocks from raw materials such as natural gas and crude oil. Lower olefins have short chains with only two, three or four carbon atoms, and the simplest one is ethylene. The higher olefins have chains of up to twenty or more carbon atoms. The main olefin products are ethylene, propylene, butadiene and C4 derivatives. They are used to produce plastics, as chemical intermediates, and, in some cases, as industrial solvents.
Ethanol, also known as ethyl alcohol (common alcohol), is manufactured by synthesis from ethylene. It is an oxygenated hydrocarbon used in a wide variety of high performance solvent applications (toiletries and cosmetics, paints, lacquer thinners, printing inks, dyes, detergents, disinfectants and pharmaceuticals), as a chemical raw material for the production of a range of monomers and solvents, and is essential in pharmaceutical purification. In transportation, ethanol is used as a vehicle fuel by itself, blended with gasoline, or as a gasoline octane enhancer and oxygenate. Ethanolamines are prepared by the reaction of ammonia and ethylene oxide. They include monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA). The three are widely used in industry, principally as absorbents for acidic components of natural gas and of petroleum-refinery gas streams. It is also used to make detergents, metalworking fluids, and as gas sweetening. TEA is used in detergents and cosmetics applications and as a cement additive.
Polyethylene (PE), with a world production around 80 million tons, is the most common plastic (and polymer). It is a polymer of ethylene, especially any of various lightweight thermoplastics that are resistant to chemicals and moisture, and has good insulating properties. Its primary use is in packaging (plastic bags, plastic films, geomembranes, containers including bottles, etc.). Many kinds of polyethylene are known, with most having the chemical formula (C2H4)nH2. It has many different trade varieties, and the most common are:
High-density polyethylene (HDPE) is used predominantly in the manufacture of blow-molded bottles for milk and household cleaners and injection-molded pails, bottle caps, appliance housings and toys. Low-density polyethylene (LDPE) is used in film applications due to its toughness, flexibility and relative transparency. Typically, LDPE is used to manufacture flexible films such as those used for plastic retail bags. LDPE is also used to flexible lids and bottles, in wire and cable applications for its stable electrical properties and processing characteristics.
Linear low-density polyethylene (LLDPE) is used predominantly in film applications due to its toughness, flexibility and relative transparency. LLDPE is the preferred resin for injection molding because of its superior toughness Polyvinyl chloride (PVC). A polymer of vinyl chloride is used to make a diverse range of cost-effective products with various levels of technical performance suited to a wide range of applications. Many of these PVC products are used every day and include everything from medical devices such as medical tubing and blood bags, to footwear, electrical cables, packaging, stationery and toys.
Polypropylenes (PP) are various thermoplastic plastics or fibers that are polymers of propylene. Polypropylene can be made into fibers, where it is a major constituent in fabrics for home furnishings such as upholstery and carpets. Numerous industrial end uses include rope and cordage, disposable non-woven fabrics for diapers and medical applications. As a plastic, polypropylene is molded into bottles for foods and personal care products, appliance housings, dishwasher-proof food containers, toys, automobile battery casings and outdoor furniture.
Polyurethanes are used to make the foam in furniture, mattresses, car seats, building insulation, and coatings for floors, furniture and refrigerators. They are also used in artificial sports tracks, jogging shoes, and in roller blade wheels.
Polyacrylonitrile (PAN) is a semi-crystalline polymer resin. Though it is thermoplastic, it does not melt under normal conditions. It degrades before melting. It is used to produce large variety of products including ultra-filtration membranes, hollow fibers for reverse osmosis, fibers for textiles, and PAN fibers that are the chemical precursor of carbon fiber. Cumene is an aromatic derived from benzene and is used in turn to produce polycarbonates, phenolic resins and essential healthcare products such as aspirin and penicillin. Methyl methacrylate (MMA). The principal application of methyl methacrylate is the production of polymethyl methacrylate (PMMA) acrylic plastics. Also, MMA is used for the production of the co-polymer methyl methacrylate butadiene-styrene (MBS), used as a modifier for PVC. MMA polymers and copolymers are used for waterborne coatings, such latex house paint.
Butadiene, butylenes, and pygas, derivatives
Pygas, or pyrolysis gasoline, is a naphtha-range product with a high aromatic content, used either for gasoline blending or as a feedstock for a BTX extraction unit. Pygas is produced in an ethylene plant that processes butane, naphtha or gasoil.
Polybutadiene is a synthetic rubber that is a polymer formed from the polymerization of the monomer 1,3-butadiene. It has a high resistance to wear and is used especially in the manufacture of tires. It has also been used to coat or encapsulate electronic assemblies offering extremely high electrical resistivity. Polyisobutylene is a synthetic rubber, or elastomer. It is special because it is the only rubber that is gas impermeable; it is the only rubber which can hold air for long periods of time. Polyisobutylene, sometimes called butyl rubber is a vinyl polymer, and is very similar to polyethylene and polypropylene in structure.
Polybutylene (PB-1) is a high molecular weight, linear, isotactic, and semicrystalline polymer. PB-1 replaces materials like metal, rubber and engineering polymers. Because of its specific properties it is mainly used in pressure piping, flexible packaging, water heaters, compounding and hot melt adhesives. Methyl-tert-butyl-ether (MTBE) is used in gasoline to boost the octane rating and to decrease toxic emissions in the exhaust. As an octane enhancer, MTBE delivers high octane numbers at relatively low cost. A direct effect of the use of MTBE is the reduction of both "regulated" emissions (CO, unburned hydrocarbons) and "unregulated" emissions.
Synthesis gas (syngas)
Synthesis gas (syngas) is a mixture of carbon monoxide and hydrogen. It can be created from coal or methane reacting with steam at high temperatures:
Syngas is used for production of methanol or ammonia. It is also used for production of synthetic fuels, both diesel (Fischer–Tropsch process) and gasoline.
Methanol based products
Methanol, a colorless alcohol, is a chemical used in the production of formaldehyde, acetic acid and methyl methacrylate (MMA), and is used as a solvent in many applications. It is also used to produce MTBE and other products, and can be used in fuels.
Melamine resin or melamine formaldehyde (also, incorrectly, melamine) is a hard, thermosetting plastic material made from melamine and formaldehyde by polymerization. This plastic is often used in kitchen utensils or plates and is the main constituent in high pressure laminates and laminate flooring. Urea-formaldehyde is a non-transparent thermosetting resin or plastic, made from urea and formaldehyde. It is used in adhesives, finishes, MDF and molded objects. Its attributes include high tensile strength, heat distortion temperature, low water absorption, mold shrinkage, high surface hardness and elongation at break.
Phenol formaldehyde is a low-cost basic resin. Addition of appropriate fillers can generate high temperature-resistant grades (185 °C/370 °F). Normal phenolics are resistant to 150 °C/300 °F. Applications include moldings, bottle tops, resins, chemically resistant coatings for metals, laminates, water lubricated bearings and foams for thermal insulation. Polyoxymethylene (POM), also known as acetal resin, polytrioxane, polyformaldehyde and paraformaldehyde, is an engineering plastic used to make gears, bushings and other mechanical parts. It is also known in variant trade names such as Delrin, Celcon and Hostaform. It is the most important polyacetal resin; a thermoplastic with good physical and processing properties.
Dimethyl terephthalate (DMT) is an ester of terephthalic acid and methanol and is used in the production of polyesters, including polyethylene terephthalate and polytrimethylene terephthalate. It consists of benzene with methyl ester groups attached. DMT has largely been replaced by pure terephthalic acid (PTA) as the preferred industrial route to polyester production.
Ammonia based products
Ammonia is a pungent, colorless, gaseous alkaline compound of nitrogen and hydrogen (NH3) that is very soluble in water and can easily be condensed to a liquid by cold and pressure. It is manufactured by the direct combination of hydrogen and nitrogen under pressure over a catalyst. The main process is still the Haber-Bosch synthesis invented in 1915, operating at 15–25 MPa and between 300 and 550 °C in four reaction chambers with catalyst. Anhydrous ammonia is mainly used for the manufacture of nitrogenous fertilizers. It is also a building block for the synthesis of many pharmaceuticals, for explosives, and is used in many commercial cleaning products.
Urea CO(NH2)2 is synthesized from ammonia and carbon dioxide. It is named for its presence in human and most land animal urine (except fish and birds). Dissolved in water, it is neither acidic nor alkaline. Urea is widely used in fertilizers as a convenient source of nitrogen. Urea is also an important raw material for the chemical industry in animal feed, plastics and resins.