Isobutylene (CH 3 ) 2 C = CH 2 is an unsaturated hydrocarbon , isomeric to butylene .
| Isobutylene | |
|---|---|
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| Are common | |
| Chem. formula | C 4 H 8 |
| Physical properties | |
| Molar mass | 56.11 g / mol |
| Density | 0.5879 g / cm³ |
| Thermal properties | |
| T. bale. | -6.9 ° C |
| Cr. pace. | 144.73 ° C |
| Cr. pressure | 39.48 atm |
| Classification | |
| Reg. CAS number | 115-11-7 |
| PubChem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| RTECS | |
| Chebi | |
| UN number | |
| ChemSpider | |
Being in nature
Contained in oil cracking gases.
Getting
Isobutylene in industry is obtained by isolating from the butane-butene fraction the production of gasoline or ethylene by catalytic or thermal cracking or pyrolysis of liquid petroleum products or petroleum gases [1] . The yield of the C 4 fraction in these three processes is 3-10, 1-2, and 0.4-5 wt.%, Respectively. Isobutylene from C 4 fractions is isolated by extraction with 65% sulfuric acid (method of A. M. Butlerov ) at temperatures close to room temperature. Extraction proceeds almost quantitatively. The result of the process is tert-butyl sulfuric acid.
(CH 3 ) 2 C = CH 2 + H 2 SO 4 = (CH 3 ) 3 COSO 3 H
which is again converted to isobutylene.
Another way is to isolate it from butylsulfuric acid by hydrolysis with hot steam, resulting in the formation of tert-butyl alcohol .
(CH 3 ) 3 COSO 3 H + H 2 O = (CH 3 ) 3 COH + H 2 SO 4
The latter is dehydrated with 30% sulfuric acid to obtain isobutylene. However, the use of this method is limited by the high cost of the sulfuric acid recovery process.
A more effective method is that the reaction liquid obtained by extraction of isobutylene with 65% acid is diluted with water to an acid concentration of 45%. When this solution is heated under low pressure, pure isobutylene is released, which is washed with alkali, freed from alcohol by cooling, washed with water and liquefied under pressure.
Union Carbide has developed a process for the isolation of isobutene from a butane-butylene fraction by adsorption on zeolites . Butylene is also isolated in this process, which isomerized to isobutylene.
Another method for producing isobutylene is the catalytic dehydrogenation of isobutane .
Application
It is used to obtain isooctane , methacrolein , synthetic resins. By reaction with alcohols , tert-butyl ethers ( MTBE , ETBE , etc.) can be obtained, which are used as additives to motor fuel.
The addition of formaldehyde to isobutylene followed by dehydration is one of the industrial methods for the synthesis of isoprene used in the production of synthetic rubbers :
Notes
- ↑ N.A. Plate, E.V. Slivinsky. Basic chemistry and technology of monomers. - Moscow: “Science”, MAIK “Science / Interperiodica”, 2002. - 696 p. - ISBN 5-02-006396-7 .