Chemical Properties
3-Methylpentane, C6H14, is a colorless, flammable liquid
with specific gravity 0.664. It occurs in petroleum and
natural gas, and may be released to the environment in
evaporative losses, wastewater, spills, and combustion
exhaust.
Physical properties
Clear, colorless, flammable liquid with an odor similar to hexane, heptane, and similar aliphatic
hydrocarbons. An odor threshold concentration of 8.9 ppm
v was reported by Nagata and Takeuchi
(1990).
Uses
3-Methylpentane is used as a solvent in the preparation of vegetable oils, glues, coatings, and paints. It is also used in gasoline, rubber solvent, and petroleum ether.
Uses
3-Methylpentane is a component of three typical commercial
hexanes, obtained from the fractionation of
natural gas liquids, a refinery operation involving hydrogenation,
and a stream meeting polymerization.
Other than for fuel, it is used in extraction of oil from
seeds and as a solvent and reaction medium in the manufacture
of polyolefins, synthetic rubbers, and some
pharmaceuticals.
Synthesis
(1) preparing a raw material, said raw material comprising light naphtha;
(2) carrying out a catalytic hydrogenation reaction on the light naphtha until it is complete, to obtain an intermediate product A, the content of benzene in the intermediate product A being 0.01%, and the content of sulfur being 0.4 ppm; the process parameters of the catalytic hydrogenation reaction being: a temperature of 140 C., the volume ratio of hydrogen to oil being 120:1, the reaction pressure being 0.2MPa
The catalyst used was loaded nickel skeleton.
(3) Intermediate product A was mixed with water and added to a first azeotropic distillation column for azeotropic distillation, and an azeotrope of water and 2,3-dimethylbutane was obtained from the top of the first azeotropic distillation column, and intermediate product B was obtained from the bottom of the column.
(4) Intermediate product B was mixed with water and added to a second azeotropic distillation column for azeotropic distillation, and an azeotrope of water and 2 -methylpentane azeotrope, separating water and 2-methylpentane after condensation; the bottom of the tower is discharged into the third azeotropic distillation column for azeotropic distillation, obtaining the azeotrope of water and 3-methylpentane from the top of the tower, separating water after condensation to obtain 3-methylpentane, wherein the 3-methylpentane contains n-hexane with a volume fraction of less than 8%; and obtaining n-hexane from the bottom of the tower. The above 3-methylpentane was adsorbed using 5A molecular sieve at atmospheric pressure and 110 C. The adsorption bed air velocity was 0.33 h-1, the regeneration pressure was -90 kPag, and the adsorption capacity of the adsorbent was 10 kg/m3, and the purity of 3-methylpentane was obtained to 99.9% after adsorption and separation, and the 5A molecular sieve was regenerated using the high-temperature water vapor displacement method to obtain desorption products, and the desorption products were incorporated into n-hexane. The product was incorporated into n-hexane.
Source
Schauer et al. (1999) reported 3-methylpentane in a diesel-powered medium-duty truck
exhaust at an emission rate of 670 μg/km.
California Phase II reformulated gasoline contained 3-methylpentane at a concentration of 22.7
g/kg. Gas-phase tailpipe emission rates from gasoline-powered automobiles with and without
catalytic converters were 3.76 and 512 mg/km, respectively (Schauer et al., 2002).
Environmental Fate
Photolytic. The following rate constants were reported for the reaction of 3-methylpentane and
OH radicals in the atmosphere: 4.30 x 10
-9 cm
3/moleculesec at 300 K (Darnall et al., 1976); 6.8 x
10
-12 cm
3/moleculesec at 305 K (Darnall et al., 1978); 5.7 x 10
-12 cm
3/moleculesec (Altshuller,
1991).
Chemical/Physical. Complete combustion in air produces carbon dioxide and water vapor. 3-
Methylpentane will not hydrolyze because it does not contain a hydrolyzable functional group.
Purification Methods
Purify it by azeotropic distillation with MeOH, as for 2-methylpentane. Purify it for ultraviolet spectroscopy by passing it through columns of silica gel or alumina activated by heating for 8hours at 210o under a stream of nitrogen. Alternatively treat it with conc (or fuming) H2SO4, then wash it with water, aqueous 5% NaOH, water again, then dry (CaCl2, then sodium), and distil it through a long, glass helices-packed, column. [Beilstein 1 IV 363.]
Toxics Screening Level
The initial threshold screening level (ITSL) for 3-methylpentane is 3,500 μg/m3 based on an 8 hr. averaging time.
