SU551316A1 - Method for producing 1,3,5-hexatriene - Google Patents

Description

(54) METHOD OF OBTAINING 13.5-HEXATRIEN

The starting material for the preparation of 1,3,5-rekca t ten is 2-metal-5,6-diggred- (2H) -pyran, obtained from tetrahydrofurylcar & 1 nol, or by reaction with peperylene with formaldehyde.

The decisive factors for the selective conduct of the process are temperature and speed. filing 2 - methyl - 5,6 - dihydro - (2H) - pyran. The process at a temperature of 350-370 ° С, a bulk feed rate of 2 - luteh - 5.6 - dihydro - (2H) pyran0, 65 .- 0.85 parts and a ratio of 2 - methyl 5, 6 - dihadro - (2H) - pyran to water 1: 2.5 - 1-3.9 (by weight).

Pressure does not significantly affect the course of the reaction, but carrying out the reaction under reduced pressure prevents the catalyst from coking and the formation of tar.

Example 1; Intez 1,3,5-hexatriene is carried out in a flow system consisting of a tubular quartz reactor filled with glass beads in the upper part (the upper part serves as an evaporator and a superheater), in the lower part there is a silica gel (the lower part is the reaction zone) with a length of 450 mm and a diameter of 22 mm placed in an electric furnace, metered pumps and reaction products receiving system.

A mixture of 2 - methyl - 5.6 - dihydro - (2H) - pyran and water with phosphoric acid (0.006%) dissolved in it enters the evaporator-superheater. Couples brought to the temperature of experience, are in contact with a layer of catalyst with a volume of 25 cm. Next, the contact gas enters the refrigerator and the receiver, which is cooled with a mixture of ice and salt. Water-jet pump supports in the system a vacuum of 450 mm Hg.

The organic part of the catalyst is separated from the water and by a single evaporation from it separating the 1dt fraction to 100 ° C, which is dried over calcium sulfate. After adding a small amount of hydr051inone (1-3%), it is subjected to vacuum distillation at 130 mm Hg.

Conditions for the synthesis of 1,8,5-hexatriene: temperature 260 ° C, the volumetric rate is filed 2 - methyl - 5.6 dihydro - (2H) -pyrana 0.75 hour, the ratio of 2 methyl - 5.6 - dihydro - (2H) - pyran to water 1: 3 (by weight), pressure 450 mm Hg

According to this method, from 98.0 g of 2 - methyl - 5.6 dihydro - (2H) - pyran get 28.0 g of 1,3,5-hexatriene (the yield on the transformed pyrap is 76.0%) and 52.8 g of unconverted 2 - Me.til - 5.6 - dihydro (2H) - pyran (conversion 46.1%).

Constants: bp 34 ° C / 130mmHg; 1.5080; df 0.7910; MRQ: calculated 28.51, found 29.77.

Dispersing,%: C, 89.94; H 10.06

Paydeno%: C 90.31; H 10.20

Example 2. Experimental conditions: temperature 365 ° С, flow velocity and 2 - methyl - 5.6 dihydro - (2P) - pyran - 0.8 hour, ratio 2 methyl - 5.6 - dihydro - (2H) - pyran to water 1: 3 (by weight), pressure 350 mm Hg. Glass beads with a diameter of 1-3 mm are used as an inert contact.

According to this method, of 98.0 g of 2 - methyl - 5.6 - dihydro - (2P) - pyran get 27.2 g of 1,3,5-hexatriene (the yield on transformed pyran is 72.2%) and 51.1 g unconverted) 2 - methyl - 5.6 - dihydro (2P) - pyrana (conversion 47.85%).

Table 1 gives a description of the products of thermal catalytic decomposition of 2 - methyl 5,6 dihydro (2H) - pyrans.

Thermocatalytic cleavage of 2 - methyl - 5.6 - dihydro - (2H) - pyran under these conditions gives the table. 1 compounds that are identified and identified by conventional methods.

In tab. Figure 2 shows the results of the thermocatalytic cleavage of 2 - methyl - 5.6 - (2H) - pyran (2-M-5,6-LH) on silica gel.

From the data of Table 2 it can be seen that the highest yield of the target product is given by the conditions: temperature 360 ° C, flow rate 2 - methyl - 5.6 dihydro - (2H) - pyran - 0.75 hour, ratio of pyran to water 1: 3 by weight). The experiments, the results of which are given in table. 2, conducted at a pressure of 450 mm Hg. with minor fluctuations related to the conditions of the experiment, except for experiment 8, which was carried out at a pressure of 700 mm Hg, and experiment 9, which was carried out at a pressure of 40 mm Hg.

According to the proposed method, it is possible to obtain 1,3,5-hexatriene on the basis of available petrochemical products - piperylene, which is a waste of industrial production of isoprene rubber, and formaldehyde, produced on an industrial scale, with a high yield (more than 70%). In addition, the process is simplified and cheapened, raw materials are expanded.

Table 1.

Claims (1)

Invention Formula The method of obtaining 1,3,5-hexatriene, characterized in that, in order to increase the yield of the target product and simplify the process, thermal catalytic splitting of 2 - methyl - 5.6 digadro - (2H) - pyran is carried out in an aqueous acid medium .PH 6.7 - 5 on inert contacts at a temperature of 25 300-400 ° С, space velocity podzt raw material 0.4 1 hour, pressure 40-700 mm Hg, ratio 2 -methyl- 5,6-dihydro- (2H) -pyran to water 1: 1.51: 5 by weight.