PROPYLENE

Description

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.

Chemical Properties

colourless gas

Chemical Properties

Propylene is a colorless gas. Slight odor. The Odor Threshold is 23 ppm.

Uses

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.

Uses

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.

Uses

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.

Uses

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.

Definition

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.

Definition

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).

Definition

ChEBI: An alkene that is propane with a double bond at position 1.

General Description

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.

Air & Water Reactions

Highly flammable.

Reactivity Profile

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.

Hazard

Asphyxiant. Highly flammable, danger- ous fire risk, explosive limits in air 2–11%. Upper respiratory tract irritant. Questionable carcinogen.

Health Hazard

Moderate concentration in air causes dizziness, drowsiness, and unconsciousness. Contact with liquefied PROPYLENE will cause ``freezing burn.''

Health Hazard

Propylene is an asphyxiate and at high concentrationsa mild anesthetic. Exposure tohigh concentrations can cause narcosis andunconsciousness. Contact with the liquefiedgas can cause burns.

Fire Hazard

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

Safety Profile

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.

Potential Exposure

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.

Carcinogenicity

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.

Environmental Fate

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.

Shipping

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.

Purification Methods

Purify it by freeze-pump-thaw cycles and trap-to-trap distillation. [Beilstein 1 IV 725.]

Toxicity evaluation

Propene is classified as a simple asphyxiant, and its toxicity is associated with the central nervous system effects associated with oxygen deprivation.

Incompatibilities

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.

Waste Disposal

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.

Raw materials

Preparation Products