SU440818A1 - METHOD OF OBTAINING ISOPRENE - Google Patents

Description

one

A known method of producing isoprene by condensation of methylal with isobutnylene in the vapor phase at 150-450 ° C in the presence of a solid acidic catalyst is oxides of metals of the I B and II groups of the periodic system on alumina, silica gel, and solid phosphoric acid.

This method is characterized by a short catalyst life, as a result of which the conversion and selectivity are significantly reduced already after about 15-30 minutes.

To increase the selectivity of the process in the implementation of the proposed method of producing isoprene, boron trifluoride or boron trifluoride with additions of salts of metals of group II or group IV deposited on anhydrous inorganic oxide is used as catalyst.

As the starting olefins, isobutylene or butylene-2 or their mixture can be used, preferably a mixture of olefinic hydrocarbons with paraffinic hydrocarbons containing at least 5 wt. % isobutylene and O-20 wt.% butylene-2.

As paraffinic hydrocarbons, oil refining products with so-called bales can be used. from minus 10 to plus 40 ° С.

The reaction of methylal with isobutene in the vapor phase is carried out by passing two reagents over the catalytic layer at elevated

temperature (150-450 ° C), preferably 250-350 ° C, and the flow rate of the liquid per hour (AFL) for the reaction mixture is about 0.1-25.0, preferably 1.0-10.0. The resulting mixture contains a large amount of

isoprene and a smaller amount of 4-methoxy-2-methyl-butene-1. Isoprene is easily removed from

this mixture by distillation.

The molar ratio of isobutylene and megilal in the initial current is about 2-20, preferably about 6-10. It is important that there is an excess of isobutylene with respect to methylal, but a much smaller excess is required than by a known method.

Mixtures containing two or more of the following compounds can be used as a feedstock: isobutylene, n-butylene-1, n-butane, trans-butylene-2, cac-butylene-2, isopentane, isopentene, etc.

In this case, methylal selectively reacts with isobutylene or butylene-2, while the residual olefins and paraffins present only play the role of a non-reactive diluent,

not interfering with the reaction.

The preferred catalyst for this process is boron trifluoride supported on alumina and containing at least 2% boron trifluoride by weight of the carrier. This catalyst is obtained in accordance with a technique in which almost anhydrous v or alumina is modified by contacting it with 2-100 wt.% Boron trichlorinated fluoride, based on the weight of alumina. It is recommended to use 9- and y-oxide of aluminum, but you can also use other mostly anhydrous inorganic oxides, such as silica and zirconia, as well as titanium oxide, chromium, zinc, and magnesium. calcium or various combinations of silica and alumina, since these oxides form heat-resistant compounds with boron fluoride fluoride.

An important advantage of this catalyst containing boron trifluoride is that this catalyst is easily re-activated on site by a simple introduction. H nebs. the number of gaseous trifluoride boron in the reaction zone. This is achieved by intermittently or continuously displacing small amounts of boron trifluoride with the reaction stream or separately introducing it into an inert gas such as nitrogen.

The activity of the catalyst and the degree of its reactivation are easily determined by measuring the amount of 4-methoxy-2-methyl-butene-1 produced. The ratio of isoprene and the specified product at the beginning of the reaction is rather high: 18: 1. If the catalyst is not activated again, this ratio gradually decreases, reaching about 10 hours after the consensus. If at this time or earlier, pass a small amount of boron trifluoride through the reaction zone. then the ratio of isoprene and 4-methoxy-2-methylbutene-1 again reaches the initial level. Moreover, the conversion of methylal, expressed as a percentage, which falls within this period from about 99 to 85%, is restored to its original level using this technique. This re-activation treatment is carried out several times until the catalyst reacts to the presence of boron trifluoride. At the same time, the catalyst can then be regenerated by heating it with a high temperature layer sufficient to burn out the required amount of carbon deposits, after which it is necessary to reactivate with additional boron trifluoride to restore its weight content relative to the amount of alumina.

4-methoxy-2-methylbutene-1, i.e., the precursor of isoprene, which is produced in large quantities with isoprene, is easily converted into isoprene in a known manner, and then separated and recycled with starting materials common exit.

According to the invention, boron trifluoride may be used as a catalyst with the addition of a cocatalyst containing copper phosphate or lead or magnesium sulphate.

or barium, the amount of 4-methoxy-2-methylbutene-1 formed is significantly less than when using three-fluorine boron alone, i.e. the selectivity for isoprene during the initial stages of the reaction is 95% when using a cocatalyst, and using one basic catalyst selectivity is only about 80%.

The ratio of catalytic boron trifluoride to cocatalyst should be in the range of 1-25 wt.% Cocatalyst to the total weight of the catalytic mixture, preferably 2-8 wt.%.

The method is illustrated with irimers. In the study of these examples, a comparison of the results obtained in example 1, in which the known catalyst was used, with the results obtained by the method of example 4, with

using the catalyst according to the invention, shows the advantage of the latter over the first in terms of the period of validity of the catalyst and selectivity for obtaining the desired isoprene. From app. 5,

b l 10 it can be seen that adding to the catalyst described in example 4, magnesium sulfate, copper phosphate or lead phosphate further contributes to the overall yield, while the introduction of a small amount of trifluoride

boron to the reaction stream (Example 7) serves to maintain the lifetime of the catalyst and its selectivity during the reaction. Comparative examples 2, 3 and 11 are introduced to confirm the fact that none

alumina, no boron trifluoride, or alumina with only metal salts added to it do not provide the catalytic activity achieved with my invention, since the catalytic activity drops rapidly. When using only boron trifluoride, the catalyst has no activity at all. Nimer 8 describes various reaction conditions and ratios, and Example 9 shows the use of a mixture of silica and alumina as a carrier for boron trifluoride instead of alumina.

Example I. In a vertical tube made of pyrex glass, equipped with electric heating and containing 4 ml of silica gel catalyst, methylal is fed through a hydraulic pump and the flow of isobutylene is adjusted using a dosing device. The reaction is carried out at a ratio of isobutyl to methyl of 15: 1 at 300 ° C. Isobutylene is injected at a rate of 25 ml / hour, and methylal is introduced at a rate of 1.5 ml / hour over a layer of 4 ml of silica gel catalyst (liquid volumetric flow rate 6.6; MHSV 80).

The results are presented in table. one.

Example 2. In accordance with the procedure described in Example 1, isobutyl and methylal were passed over 4.0 ml of alumina at 24 cm / h and respectively

1.5 ml / hour, i.e., the molar ratio of isobes. Table 1 of tylene to methylal is about 1 °, and the hourly volume velocity of the liquid is 6.6. The results are presented in table. 2. Table 2 15 Example 3. According to the procedure described in Example 1, 24 ml / h of isobutylene and 2.8 ml of methylal are passed over a catalyst containing alumina impregnated with 10 wt.% Magnesium sulfate (liquid hourly space velocity 9.0 ). The results are presented in table. 3. Table 3 Example 4. According to the procedure described in Example 1, isobutylene was added at a rate of 24 ml / hour and methylal at a rate of 1.5 ml / hour at 300 ° C over 4 ml of alumina containing 6% by weight of trifluoride. boron (liquid hourly space velocity 6.6; the molar ratio of isobutylene to methylal is 15). The results are presented in table. 4. Table 4 Example 5. The procedure described in Example 4 is repeated, except that the catalyst is trifluorine 20 25 30 35 40

Table 5, boron on alumina, contains, in addition, 5 wt.% Magnesium sulphate. After 10 hours, the conversion is 99%, and the selectivity to isoprene and to 4-methoxy-2-methyl-butene-1 is 80% and respectively, 6%. Example 6 The procedure described in nimer 5 is repeated except that instead of magnesium sulphate, 10% by weight of copper phosphate is used. After 10 hours, the conversion is 95%, and the selectivity to isoprene and to 4-methoxy-2-methyl-1-butene is 75 and 9%, respectively. Example 7. The procedure described in Example 3 was repeated except that the starting methylal contained I weight and about 7.3 boron trifluoride. After 15 hours, the conversion is 99%, and the selectivity to isoprene and to 4-methoxy-2-methyl-1-butene is 60 and 25%, respectively. Example 8. The procedure described in Example 7 is repeated except that the loading of reagents is 5.8 ml / hour for isobutylene, and 1.5 ml / hour for methylal (the liquid hourly space velocity is 1.8 molar ratio of isobutylene to methylal 2). After 10 hours, the conversion is 95%, and the selectivity to isoprene and to 4-methoxy2-methylbutene-1 is 75 and 15%, respectively. After 12 hours, the conversion is 85%, and the selectivity to isoprep and to 4-methoxy-2-methyl-1-butene is 1 50 and 35%, respectively. Example 9. In accordance with the procedure described in Example 4, isobutylene was injected at a rate of 24.0 ml / hour and methylal 2.8 ml / hour at 300 ° C over a silica compound with alumina containing 5% boron trifluoride. (liquid hourly space velocity 6.6). The results are presented in table. 5. Example 10. The procedure described in Example 5 is repeated except that instead of magnesium sulphate, 20% lead sulphate is used. After 10 hours, the conversion is 99%, and the selectivity to isoprene and to 4-methoxy-2-methyl butene-1 is a total of 83%. Example 11. In accordance with the procedure described in Example 4, boron trifluoride is used without alumina or another solid catalyst by conducting the reaction in a closed system at a temperature of 150 ° C under a pressure of 180 psig. inch (12.66 kg / cm). During the reaction,

black viscous material resembling a polymer.

When carrying out the reaction at 0 ° C, the main product is 1,3-dimethox-3-methyl butene.

Pr, Immer 12. In accordance with the procedure described in Example 1, a mixture of € 4-Szolefins and a paraffin-containing product of oil refining, containing 12% isobutene, was introduced at a rate of 24 ml / hour and methylal at a rate of 1.5 ml / hour at 300 ° C over 4.0 ml of alumina containing 6% boron trifluoride (liquid hourly space velocity 6.6; molar matching of isobutylene to methylal 2).

After 10 hours, the conversion of methylalal is 70%, and the selectivity to isoprene and to 4-methoxy-2-methylbutene-1 is 65 and 7% respectively. The remaining components of the mixture, except isobutylene, are extracted almost unchanged. Example 13. The procedure described in Example 12 is repeated, except that instead of the stream € 4-Sat-products of oil refining, a stream of hydrocarbons containing 50% isobutylene and 50% isobutane is used (liquid hourly space velocity 6.6; mol The ratio of isobutylene to methylal is 8).

After 10 hours, the conversion of methylal is 95%, and the selectivity to isoprene and to 4-methoxy-2-methylbutene-1 is 73 and 13%, respectively. Isobutane is recovered without change. Example 14. According to the method described in example 4, butene-2 is passed through instead of isobutylene. Methyl with a speed of 1.5 ml / hour and butene-2 (liquid) with a speed of 24 ml / hour is passed over 4 ml of alumina containing 6% boron trifluoride (liquid hourly velocity 6.6; molar ratio of butene-2 to methylal 15) at 300 ° C. After 8 hours, co-epic is 50%, and the selectivity to isoprene and to 4-methoxy-2-methyl-butene-1 is totally 60%.

Example 15. Following the procedure described in Example 4, but used as a carrier.

for boron trifluoride, instead of alumina, a silicon dioxide-magnesium oxide compound, or a silica-alumina compound, respectively, gives the following results after 5–8 hours: selectivity for methylal on Si -A1 99%, on Si -Mg98%; isoprene selectivity on Si - A1 74%, on Si - Mg 71%; selectivity to 4-megoxy-2-methylbutene-1 on Si-A1 8%, on Si - 10 Mg 11%.

Subject invention

Claims (5)

1. A method of producing isoprene by reacting methylal with isobutylene or butene tylene-2 or their mixture in the vapor phase in the presence of a solid catalyst, characterized in that, in order to increase the selectivity of the process, boron trifluoride or trifluoride boron fluoride is used as a catalyst metals and groups or IV, deposited on anhydrous inorganic oxide. 2. The method according to claim 1, characterized in that the quality of the raw material is mainly taken 5 A mixture of C4-Cj olefinic hydrocarbons with paraffinic hydrocarbons containing at least 5% isobutylene and O-20 wt.% Butylene-2. 3. The method according to claim 1, characterized in that 0 as the catalyst is preferably use boron trifluoride on alumina, containing at least 2% boron trifluoride by weight of alumina. 4. A method according to claim 1, characterized in that 5 that an additional amount of boron trifluoride is introduced into the reaction mixture after the start of the reaction. 5. A method according to claim 1, characterized in that a catalyst is used containing an additive of magnesium or barium sulfate, or lead, or copper phosphate in an amount of -25%, preferably 2-8%, of the total weight of the catalyst. Priority points: 11.11.71 on PP. 12, 3, 4, 5; 04/17/72 under item 2.