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What is propylene?

The propylene or propene is a hydrocarbon at room temperature and atmospheric pressure is in the gaseous state , and the like other alkenes, is colorless. It has an odor similar to oil but less intense. It presents a dipole moment since, although it lacks a strong polar bond, its molecule is asymmetric.

Likewise, propylene is a structural isomer of cyclopropane (they have the same chemical formula C 3 H 6 ). It occurs in nature as a consequence of the processes of vegetation and fermentation . It is produced artificially during the processing of fossil fuels such as oil, natural gas and, to a lesser extent, carbon.

Similarly, ethylene and propylene are products of petroleum refining in a process of splitting large hydrocarbon molecules to generate small hydrocarbons in high demand.

Propylene can also be obtained using different methodologies:

  • By reversibly reacting ethylene and butene, where the double bonds are broken and reformulated to give propylene.
  • Through a process of dehydrogenation (loss of hydrogen) of propane.
  • As part of a program to produce olefins from methanol (MTO), propylene was produced from methanol. This was passed through the zeolite catalyst, which promotes its dehydration and leads to the formation of ethylene and propylene.

3CH 3 OH (methanol) => CH 3 CH = CH 2  (propylene) + 3H 2 O (water)

Chemical structure of propylene

In the chemical structure of propylene, its asymmetry stands out (the right side is different from the left). Its carbon skeleton, excluding the H atoms, can be seen as a boomerang.

However, the other side is occupied by the methyl group (–CH 3 ), whose hybridization is sp 3 and has a tetrahedral geometry. Thus, seen from the front, the boomerang is flat with the H atoms protruding from it at approximately 109.5º.

In the gas phase, the molecule weakly interacts with others by dispersion forces. Likewise, the interactions between the double bonds (π-π) of two propylene molecules are prevented by the methyl group.

This results in a decrease in its intermolecular forces, which is reflected in its physical properties. Only at very low temperatures, propylene can adopt a solid structure, in which the boomerang remain grouped with their weak interactions.

Propylene properties

It is a colorless gas with an aromatic odor. It is transported in the form of liquefied gas and, when it escapes from the containers that contain it, it does so in the form of a gas or liquid. At low concentrations it forms an explosive and flammable mixture with air, the density of propylene being greater than that of air.

42.081 g / mol

Boiling point

53.9ºF at 760mmHg

48 ºC to 760 mmHg

Melting point

301.4 ºF

185 ºC

Flash point

162ºF

Solubility

44.6 ml / 100 ml in water.

1,250 ml / 100 ml in ethanol.

524.5 ml / 100 ml in acetic acid.

Solubility expressed as mass

200 mg / l 25 ºC

Density

0.609 mg / ml at -52.6º F

0.5139 at 20º C

Vapor density

1.46 at 32ºF (relative to air taken as reference).

1.49 (air = 1).

1.91 kg / m 3 at 273.15 ºK

Vapor pressure

1 mmHg at -205.4ºF

760 mmHg at -53.9ºF

8.69 × 10 3 mmHg at 25 ° C (extrapolated value).

1,158 kPa at 25 ºC

15.4 atm at 37 ºC

Autoignition

851ºF

455 ºC

Viscosity

83.4 micropoise at 16.7 ° C.

Heat of combustion

16,692 BTU / lb

10,940 cal / g

Heat of vaporization

104.62 cal / g (at boiling point )

Surface tension

16.7 dynes / cm at 90 ° C

Polymerization

Polymerizes at high temperatures and high pressures in the presence of catalysts.

Freezing point

185.25 ° C.

Odor threshold

10-50 mg / m 3 (detection)

100 mg / m 3 (recognition)

Uses / applications of propylene

Propylene is used in the petrochemical industry as a fuel and an alkylating agent. In the chemical industry it is used as a raw material for the production and synthesis of numerous derivatives.

It is mainly useful in the production of polypropylene, acrylonitrile (ACN), propylene oxide (PO), alcohols, cumene, and acrylic acids.

Polypropylene

Polypropylene is one of the main plastic materials used in electronics and electrical accessories, household items, bottle caps, and suitcases.

The laminated material is used in the packaging of sweets, labels, compact discs, etc., while the fibers are used to make folders and clothes.

Acrylonitrile

Elastomeric polymers and fibers are obtained from acrylonitrile. These fibers are used for the manufacture of different forms of clothing, such as sweaters, socks and sportswear. They are also used in home furnishings, folders, upholstery, cushions and blankets.

Propylene’s OXID

Propylene oxide participates as a component in the synthesis of polyurethane. This is used in the manufacture of flexible foam and rigid foam. Flexible foam is used as a filler in home furniture and in the automotive industry.

On the other hand, rigid foam is mainly used as an insulating material for buildings.

Also, propylene oxide is used in the production of propylene glycol. This compound is used in the manufacture of unsaturated polyester resins and as an antifreeze.

Additionally, propylene oxide is used in the production of propylene glycol ether. This ether has application in the manufacture of paints, clothes, inks, resins and cleaners.

For alcohol synthesis and other uses

Propylene allows the obtaining of some alcohols, among them isopropanol, used as a solvent in cosmetics and personal care products. In addition, it fulfills the function of an antiseptic agent.

  • Isopropanol is involved in the manufacture of paints, resins, inks and adhesive tapes. It is also used in the pharmaceutical industry.
  • Oxo-alcohol-2-ethylhexanol is used in the production of phthalate, plasticizers, adhesive materials, and paints.
  • Butanol is used in the manufacture of paints, coatings, resins, colorants, pharmaceuticals, and polymers.

On the other hand, cumene is produced from the combination of propylene and benzene. Cumene is the main compound in the manufacture of phenol and acetone, used in a variety of products, such as polycarbonates, phenolic resins, epoxy resins, and methyl methacrylate.

Finally, acrylic acid – another propylene derivative – is used in the production of acrylic esters and resins for paints, coatings, and adhesive applications.

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