SU679561A1 - Method of obtaining cis-pentadiene-1,3 - Google Patents

Description

one

The invention relates to petrochemical processes for the preparation of diene hydrocarbons, specifically, to a process for the preparation of ziv-pentadiene-1,3.

Cyo-Pentadiene-1,3, which is more reactive than the grano-isomer, is of interest as a monomer for the preparation of piperylene containing rubbers.

During the polymerization of the cyoisomer, less time is required to obtain piperylene-containing rubber, which makes the process more efficient.

At present, a mixture of pentadiene-1,3 isomers is sent for polymerization.

Conversion at the same time sogavl him about 5O%. Return monomers are enriched in less reactive trans-isomer and therefore not suitable for reuse in polymerization, which significantly increases the cost of rubber.

A known method of producing a mixture of grano entadiene-1,3 by dehydrogenating

isopentane when heated in the presence of a catalyst, Pentadienes-1,3 are formed in a mixture with the target product and ivoprene. The ratio is 1: 5 1.

The disadvantage of this method is the formation of a complex mixture of hydrocarbons, in which pentadiene-1,3 is mainly in the form of a trans form.

The closest to the invention to the technical essence and the achieved result is the method of obtaining cyopentadiene-1,3 by isomerization of gran o-41 decadiene-1, 3 at a temperature of up to 255 ° C, in the presence of bryum or chlorotriphenyl methane in a solvent medium — aromatic hydrocarbons , ethers. Over 7 hours, the yield of cis-sepadien-1,3 is 1% 2.

Claims (2)

A significant disadvantage of the method is the low-tech process, with a long reaction time, low yield, the need to use scarce reagents and solvents. 6795 3 The purpose of the invention is to implement a nkö). process technology and increase the yield of the target product per unit of time. . The goal of the dosage method is to obtain the cyo-centade, en-1,3 by isomerization of grano-pentadaena1, 3 at a temperature of 450-800 C and time. And to the reaction of 0, with the subsequent removal of the target product in the return of the no-reacted trans-pentadiene-1.3 to isomerization, the conversion of isomerization is. with a selectivity of 71-98%. The process is carried out in the absence of a .ts catalyst. This process can be carried out in the presence of a diluent or, in the phase, at a pressure of 1-5 atm. The selection of cyopentadiene is carried out by preparative chromatography or rectification, 20 unreacted trans-pentadiene 1.3 is returned to isomerization. The method of producing cyo-pentadiene-1,3 is carried out according to the following technology. trans-Pentadiene, 3 after evaporation 25 is fed to mixing with superheated steam. The resulting mixture enters the isomerization reactor, which is either in a furnace for superheating steam, or made in an adiabatic version. The isomerization product 1g is condensed and separated from the α-hydrocarbons, then, after separation from water, is sent to a column for separation of the C-fraction. From the bottom of the column, hydrocarbons are directed to the next 35 column, where the separation of pentadiene-1,3 isomers takes place. From the top, the columns are taken to enrich the trans isomer, which is directed to the iso. gauging: the cis-pentadiene-1,3 enriched fraction is extracted from the bottom of the column, which, after separation from the high-boiling products, is sent for polymerization. After polymerization, they are recycled, the monomers are sent either to separation columns, or directly to isomerization. A possible direction for the polymerization of pentadienes-1,3 without the separation of isomers. Identification of the obtained cistem-50 Diana-1,3 is carried out using phi:. zico-chemical analysis methods - gas liquid chromatography and ultraviolet spectroscopy. Chromatographic analysis of the isomerization products was carried out 55. On a Tsvet-101 chromatograph with a flame ionization detector and a micro-filled column with a diameter of 1 mm and a length of 61. four . This is 2 m. The stadium phase is n bugiratgragyglycol glycol on a diamolytic brick (fraction O, 088 -OD04 mm). Pressure of carrier gas (nitrogen) 3 yeah. Temperatur® speakers are room. The relative-alumina retention time of cyo-pentadiene1, 3 with respect to isoprene is 1.34. In isomerization products, cis-pentadiene-1,3 was identified chromatographically and the ultraviolet absorption spectrum of this component was obtained. The maximum absorption was 227 nm, which coincides with the literature data. Example 1. Pentadiene-1,3 composition,% 1 tsanonaentadiene-1,3 80; Cytopentadiene -1, 3 after evaporation is passed through the reactor at 520 C and the residence time in the reaction zone is 2.7 s. The reactor is in the form of a coil of steel (1X18H10T) tube with a diameter of 6 mm and a length of 119 cm. Products reactions are analyzed by chromatography. 75 g shntadiene-1,3 is missed. Receive 74.5 g of isomerivate composition,%: C "hydrocarbons 2.8; amylenes 1,1; trans pentadiene-1,3 63.9; cao-pentadiene-1,3 36.1. Conversion of isomerization is 18.1%, selec-; ness 96 1%. From the isomerization products on the distillation column, the efficiency of theoretical theoretical plates was 40 g (94%) of trans-pentadiene-1.3, which was returned for isomerization, and 20.3 g of cis-pentadiene-1, 3 directed at polymerization. Example 2. Analogously to example i, the initial atadiene-1,3 contains 99.9% of the trans-aaomer. Isomerization conditions: BOO ° C temperature, reaction time 0, O01 s. Get pentadienes composition% transontadiene-1, 3 58.1; cyo-centadiene-1,3 41.9. The isomerization selectivity is 71.4%. Example 3. Analogously to example 2. Conditions: temperature, reaction time 0.045 s. The composition of pengadienes after isomerization,%: tranno-pentadiene-1,3 61.9; cyo-pvntadiene-1,3 38.1. Isomerization selectivity is 94.7%. EXAMPLE 4 Analogously to example 2. Conditions; temperature, reagent time OD7 with Composition of pentadienes after isomerization,%; Tranno-and: entadiene-1,3 63,4; cyo-pentadiene-1,3 36.1. Isomerization selectivity is 96.4%. Example 5. Analogously to example 2. Conditions: temperature, reaction time 30 s. The composition of pentadienes after isomerization,% i-interidien-1,3 5 86.3; cyochlene-1,3 1,3,7. Conversion 13.7%, selekgivost 98.4%. Example 6 (for comparison). In a 100 ml round-bottom flask with a stirrer, a thermometer and a condenser, 30 ml of orthoxylene, 10 ml of pentadnene1, 3 composition,% are added: trans-pentadiene-1.3 82; cyo-pentadiene-1,3 18, and 5 g of bromotriphenylmethane. The solution is heated for 45 hours at. The resulting polymers 2g, pentadienes,%: tranno-pentadiene 81; cyo-pentadiene 19%. The output of cyo-pentadvena-1, 3 1. The formula is invented a. The method of obtaining cisnaentadiene-1,3 by isomerization of tranno-pentadiene-1,3 with 679 1 6 increased temperature, which, in order to simplify the process technology and increase the yield of the target product, isomerization is carried out at a temperature of 450-800 ®C and the reaction time of 0.001-30 s, followed by separation of the target product and returning unreacted country-pentadian1, 3 to isomerization. Sources of information, attention during examination 1. Gardeners p. K., Idlis G. S. Isoprene production. Khimi / L., 1973, p. 132. 2. US patent No. 390 3188, cl. 260-680, 1975.