Propylene is a colorless, fl ammable gas that follows ethylene as the second simplest alkene
hydrocarbon. It has an odor similar to garlic and has wide use in the chemical industry as an
intermediate in the synthesis of other derivatives such as polypropylene, propylene oxide, isopropyl
alcohol, acetone, and acrylonitrile. The production of propylene is similar to ethylene
and is obtained through steam cracking of hydrocarbon feedstocks. Steam cracking is a process
used to break molecules into smaller molecules by injecting the catalysts with steam.
Propylene is a colorless gas. Slight odor. The
Odor Threshold is 23 ppm.
Propylene is obtained from refining of gasolineand thermal or catalytic cracking ofhydrocarbons. It is used to produce polypropylene(plastic) and in the manufacture ofacetone, isopropanol, cumene, and propyleneoxide.
Polypropylene is closer to HDPE in its properties. Polypropylene is more heat resistant than polyethylene, and its higher melting point makes it preferable for items subjected to heat such as dishwashers. It is also used extensively for containers of dairy projects. Familiar plastic containers holding yogurt, butter, margarine, and spreads are generally made of polypropylene. Another advantageous property of polypropylene is that it is resistant to many solvents, acids, and bases. This makes it an ideal for several common applications: the casing of car batteries, truck bed liners, outdoor carpet and welcome mats, tops for plastic bottles, storage tanks, car trim and paneling, and toys. Polypropylene is also used extensively in fiber form in textile applications. One third of polypropylenes production in the United States is used as fiber and the worldwide use of fiber polypropylene was approximately 2.5 million tons in 2005. Major uses of fiber polyethylene are carpeting, upholstery, paper and packaging, construction fabric liners, diapers, and rope. Propene is used as a starting material for numerous other compounds. Chief among these are isopropyl alcohol, acrylonitrile, and propylene oxide. Isopropyl alcohol results from the hydration of propylene during cracking and is the primary chemical derived from propylene. Isopropyl alcohol is used as a solvent, antifreeze, and as rubbing alcohol, but its major use is for the production of acetone. Acrylonitrile is used primarily as a monomer in the production of acrylic fibers. Polymerized acrylonitrile fibers are produced under the trade names such as Orlon (DuPont) and Acrilan (Monsanto). Acrylonitrile is also a reactant in the synthesis of dyes, pharmaceuticals, synthetic rubber, and resins. Acrylonitrile production occurs primarily through ammoxidation of propylene: CH3- CH = CH2 + NH3 + 1.5O2→CH2 = CH - CN + 3 H2O.
Accelerated production and use of polypropylene began in the late 1950s when the discovery
of Ziegler-Natta catalysts made large-scale polymerization of propylene economically
feasible. The polymerization of propylene leads to several different structures that vary in their
properties based on their tacticity. Tacticity, derived from the Greek word tactos meaning
ordered, refers to how groups are arranged in a polymer. The general structure of the polypropylene
molecule can be pictured as polyethylene in which a methyl (CH3) group has replaced
a hydrogen atom in each monomer. Three general structures for polypropylene are termed
isotactic, syndiotactic, and atactic.
The different forms of polyethylene, such as low-density polyethylene (LDPE) and highdensity polyethylene (HDPE), dictate its physical properties. In the polymerization process, the isostatic structure forms helical coils that allow tight packing, resulting in a highly ordered crystalline structure and producing a hard, strong, stiff plastic with a high-melting-point. Conversely, the random atactic configuration prevents a tight structure resulting in an amorphous, soft substance. Polypropylene production accelerated around 1960 with the advent of Ziegler-Natta catalyst to control the polymerization process. In the last 20 years, a new group of catalysts called metallocene catalysts have resulted in signifi cant advances in the propylene industry. Metallocene catalysts consist of a transition metal, such as titanium or zirconium, sandwiched between carbon rings.
Metallocene catalysts have allowed greater control and advances in polymerization. The
polymerization of isostatic propylene up to about 1995 resulted in a structure with approximately
5% atactic polypropylene. Metallocene catalysts made it possible to produce 100% isostatic or syndiotactic polypropylenes. The catalysts have also allowed chemists to control
the chain length of polypropylene tacticities in polymers to produce various polypropylenes
with a range of physical and chemical characteristics. For example, rubbery elastomer polypropylene
results by producing atactic polyethylene chains with regions of isostatic polypropylene
interspersed along the chain. The isotactic regions are areas along the chain where
greater attraction and packing between molecules takes place, resulting in cross-linking of
the chains. This is similar to the vulcanization process in rubber. Th us a soft flexible polypropylene
is produced. Polypropylene is also co-polymerized with polyethylene to expand
its applications.
In polymerized form as polypropylene for plastics and carpet fibers. Chemical intermediate in the manufacture of acetone, isopropylbenzene, isopropanol, isopropyl halides, propylene oxide, acrylonitrile, cumene.
propylene: A colourlessgaseous hydrocarbon, CH3CH:CH2;m.p. –185.25°C; b.p. –47.4°C. It is analkene obtained from petroleum bycracking alkanes. Its main use is inthe manufacture of polypropene.
A
gaseous alkene. Propene is not normally
present in the gaseous crude-oil fraction
but can be obtained from heavier fractions
by catalytic cracking. This is the principal
industrial source. Propene is the organic
starting material for the production of
propan-2-ol, required for the manufacture
of propanone (acetone), and the starting
material for the production of polypropene
(polypropylene).
ChEBI: An alkene that is propane with a double bond at position 1.
PROPYLENE is a colorless gas with a faint petroleum like odor. PROPYLENE is shipped as a liquefied gas under its own vapor pressure. For transportation PROPYLENE may be stenched. Contact with the liquid can cause frostbite. PROPYLENE is easily ignited. The vapors are heavier than air. Any leak can either be liquid or vapor. PROPYLENE can asphyxiate by the displacement of air. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. PROPYLENE is used to make other chemicals. Can cause explosion.
During an experiment to produce lactic acid by oxidizing PROPYLENE with nitrogen peroxide, a violent explosion occurred. These mixtures (olefins and nitrogen peroxide) form extremely unstable nitrosates or nitrosites (Comp. Rend. 116:756 1893). Contact of very cold liquid PROPYLENE with water may result in vigorous or violent boiling of the product and extremely rapid vaporization due to the large temperature differences involved. If the water is hot, there is the possibility that a liquid "superheat" explosion may occur. Pressures may build to dangerous levels if liquid PROPYLENE contacts water in a closed container.
Asphyxiant. Highly flammable, danger-
ous fire risk, explosive limits in air 2–11%.
Upper respiratory tract irritant. Questionable
carcinogen.
Moderate concentration in air causes dizziness, drowsiness, and unconsciousness. Contact with liquefied PROPYLENE will cause ``freezing burn.''
Propylene is an asphyxiate and at high concentrationsa mild anesthetic. Exposure tohigh concentrations can cause narcosis andunconsciousness. Contact with the liquefiedgas can cause burns.
Behavior in Fire: Containers may explode. Vapor is heavier than air and may travel considerable distance to a source of ignition and flash back.
Flammability and Explosibility
Extremely flammable
A simple asphpant.
No irritant effects from hgh concentrations
in gaseous form. When compressed to liquid
form, can cause skin burns from freezing
effects of rapid evaporation on tissue.
Questionable carcinogen. Flammable gas
and very dangerous fire hazard when
exposed to heat, flame, or oxidlzers.
Explosive in the form of vapor when
exposed to heat or flame. Under unusual
conditions, i.e., 955 atm pressure and 327'℃, it has been known to explode. Explodes on
contact with trifluoromethyl hypofluorite.
Explosive polymerization is initiated by
lithium nitrate + sulfur dioxide. Reacts with
oxides of nitrogen to form an explosive
product. Dangerous; can react vigorously
with oxidizing materials. To fight fire, stop
flow of gas. Used in production of
fabricated polymers, fibers, and solvents, in
production of plastic products and resins.
For effects of simple asphyxiants, see
ARGON.
Propylene is used in production of
fabricated polymers, fibers, polypropylene resins; solvents,
isopropyl alcohol, propylene dimer, and trimer as gasoline
components and detergent raw materials; propylene oxide;
cumene, synthetic glycerol; isoprene, and oxo-alcohols.
Exposure of rats and mice to
200, 1000, or 5000 ppm propene 7 h/day, 5 days/week for
18–24 months did not reveal any carcinogenic effects in
either species. In another study with exposures of 5,000
and 10,000 ppm, rats exhibited non-neoplastic lesions in the
nasal cavity. These consisted of hyperplasia in female rats
exposed to the high concentrations, and squamous metaplasia
in female rats exposed to both concentrations and in
male rats exposed to the low concentration. Inflammatory
changes occurred also in male rats of both exposure
groups.
Propene degrades in the atmosphere by reaction with photochemically
produced hydroxyl radicals with a half-life of
14.6 h. It also reacts in air with ozone and nitrate radicals with
half-lives of 1 and 4 days, respectively. In soil, volatilization is
expected to be the primary fate due to propene’s high vapor
pressure. Volatilization also occurs from water, while remaining
propene is readily degraded by microorganisms. This
results in propene being unlikely to bioaccumulate or bioconcentrate
in soil or aquatic organisms.
UN1077 Propylene, Hazard Class: 2.1; Labels:
2.1-Flammable gas. UN1075 Petroleum gases, liquefied or
Liquefied petroleum gas, Hazard Class: 2.1; Labels: 2.1-
Flammable gas. Cylinders must be transported in a secure
upright position, in a well-ventilated truck. Protect cylinder
and labels from physical damage. The owner of the com-
pressed gas cylinder is the only entity allowed by federal
law (49CFR) to transport and refill them. It is a violation
of transportation regulations to refill compressed gas cylin-
ders without the express written permission of the owner.
Purify it by freeze-pump-thaw cycles and trap-to-trap distillation. [Beilstein 1 IV 725.]
Propene is classified as a simple asphyxiant, and its toxicity is
associated with the central nervous system effects associated
with oxygen deprivation.
Propylene forms explosive mixture with
air. Violent reaction with oxidizers (chlorates, nitrates, per-
oxides, permanganates, perchlorates, chlorine, bromine,
fluorine, etc.); contact may cause fires or explosions. Keep
away from alkaline materials, strong bases, strong acids,
oxoacids, epoxides, and many other compounds. Able to
form unstable peroxides; can polymerize, especially in
heat, direct sunlight, oxidizers and other chemicals.
Return refillable compressed
gas cylinders to supplier. Use a licensed professional waste
disposal service to dispose of this material, perhaps using
controlled incineration. All federal, state, and local environ-
mental regulations must be observed.
