DE2739226A1 - Alkene di:halide, prepd. from corresp. satd. hydrocarbon - by oxyhalogenation, used in prepn. of nitrile(s) partic. adiponitrile - Google Patents

Abstract

A 4-5C alkene dihalide is prepd. by continuous oxyhalogenation of the corresp. satd. aliphatic hydrocarbon in the presence of a stabilised cupric halide catalyst. P2, a halogen pref. Br2, and the hydrogen, in the gaseous phase are fed at a regulated temp., into a reactor. The gas flow rate and the reactor conditions of temp. and press. are predetermined according to the hydrocarbon structure, the halogen, the appts. and the catalyst concn. used, so as to favour the formation of the required alkene dihalide. The effluent from the reaction mixt. is selectively condensed to recover the alkene dihalide. Alkene partic. butene dihalides are partic. useful in the prepn. of nitriles such as adiponitrile via dicyanoalkenes which are readily prepd. from the dihaloalkenes.

Description

Process for the production of

Alkenedihalides The invention relates to the preparation of alkenedihalides from corresponding saturated aliphatic hydrocarbons.

It is known that alkenedihalides, especially dihalobutenes, are particularly useful for the production of adiponitrile via dicyanobutene. That Dicyanbutene can from dihalobutene much more easily than from butadiene be prepared, as the intermediate dicyanobutene by direct implementation of the Dihalobutene can be produced with HCN, while butadiene is used as the starting material a conversion with HCN to dicyanobutene is difficult and a complex catalyst makes necessary. Earlier attempts to obtain dichlorobutenes e.g. by oxychlorination of n-butane manufacture resulted in low conversion rates and large amounts of undesirable by-products; a possible, unexplained reason for this is that otherwise suitable catalysts were unstable during implementation and led to greater selection fluctuations. A useful process for the preparation of alkene dihalides, including Dibromobutene, from the saturated aliphatic hydrocarbon, would take the step the conversion of the saturated hydrocarbon into the diene (e.g. n-butane into butadiene) before the production of the dicyanalkene as a precursor in the production of nitriles, e.g., make adiponitrile unnecessary; it would be a major advance over that the previous processes and is therefore the subject of the present invention.

The invention relates to a process for the preparation of an alkene dihalide with 4 to 5 carbons from the corresponding saturated aliphatic hydrocarbon, being the saturated aliphatic hydrocarbon with free oxygen and halogen in the presence of a stabilized Catalyst mixture, the copper (II) -halide contains, is oxyhalogenated. In this process, oxygen, Halogen and hydrocarbon in the gas phase and at controlled speeds and temperatures introduced into a reaction vessel in which feed rate, Pressure and temperature at those necessary to promote the formation of alkene dihalides Values are maintained.

The alkene dihalide is not converted from the oxygen, halogen saturated hydrocarbon and water-containing reaction mixture by selective Won condensation of the outflowing reaction mixture.

The alkane series can be used as a saturated aliphatic hydrocarbon straight or branched chain with 4 to 5 carbon atoms can be used. Of course, it can contain substituents other than carbon and hydrogen be present, provided they practically do not react and the reaction under the do not adversely affect the given conditions. The preferred hydrocarbons are the normal (unbranched) butane and pentane. Most preferred is n-butane, 1,4-dibromobutene-2 and 3,4-dibromobutene-1 being the most preferred alkene dihalide products are.

It has been found to be an effective copper (II) halide catalyst can be stabilized by adding potassium or ammonium halide. The maintenance catalyst stability is essential and no other method has been used to date than using these particular compounds as part of the catalyst mixture found.

Surprisingly, not even the salts of the other alkali metals can stabilize the copper (II) halide in a satisfactory manner. The amount of the stabilizing salt is not critical, but gives satisfactory results however, amounts of 23 to 50% of the total weight of the catalyst mixture were used achieved.

The catalyst mixture is preferably used in the reaction on a practically inert carrier, such as pumice stone, introduced. This one came up with a solution of the catalyst mixture is saturated, the solvent then being filtered off and / or evaporation removed and the carrier in a nitrogen stream at about 150 OC was dried so that a catalyst mixture concentration of about 5 to 10% by weight, based on the pumice stone support, remained.

Among the various halogens for the feed gas and the corresponding Halogen components of the catalyst (and catalyst stabilizer) were found to that bromine gave higher yields and selectivities for the dihalide than the other ilalogens. In addition, due to the greater instability of the dibromobutenes compared to the corresponding compounds with other halogens, in the cyanation step achieved greater selectivities in the production of adiponitrile. Bromine is therefore the preferred halogen.

Depending on the saturated aliphatic hydrocarbon used, the apparatus, the catalyst concentration and the halogen chosen can be a Variety of pressure and temperature conditions can be chosen under which alkene dihalides can be produced with degrees of selectivity that far exceed those previously known lie. The vapor phase reaction is preferably carried out in a single stage reaction vessel with a fluidized or fixed bed at temperatures above 250 OC and below about 300 OC carried out at atmospheric pressure. It has been found that excessive cracking and Charring of the reactants in the products occurs when the reaction occurs is carried out above 300 OC.

To avoid unreacted halogen and over-halogenation, the saturated aliphatic hydrocarbon should be in excess over the halogen be used. In the oxibromination of butane, a molar feed ratio is used from oxygen and bromine to hydrocarbon from about 0.2 to 0.6 and 0.1 to 0.5, respectively a stoichiometric butane Excess, causing excessive bromination and the loss of unreacted bromine can be avoided. It also turned out to be it is advantageous, but not necessary, to dilute the feed gases with nitrogen, to avoid the flammability ranges of the hydrocarbon. So should e.g., molar ratios of oxygen and air to butane of 0.8 to 4.9 and 1.9, respectively to 8.5 can be avoided. Of course, the feed speeds should the various components can be set individually for maximum selectivity for the desired product, taking into account the equipment chosen, the catalyst concentration, pressure, temperature, as well as the starting material chosen particular saturated aliphatic hydrocarbon and halogen.

For the recovery of the alkene dihalide, any effective selective Condensation processes can be used. A three-stage capacitor is preferred, which can be operated at different temperatures.

Examples A 2 x 50 cm Pyrex tube was used as the reaction vessel, to which a feed gas preheater was attached. To maintain the temperature A fluidized sand bath was used for the reaction vessel and preheater. To record The effluent from the reaction vessel became a series of condenser traps intended. These were for a first condensation temperature of 25 OC, a second of 0 OC and a third set from -78 OC. A pumice stone support was used for the catalyst used. The pumice stone was made with copper (II) bromide and potassium bromide in the specified, impregnated as a percentage of the weight of the pumice stone. That Potassium bromide was used to lower the sublimation temperature of the copper (II) bromide and used to increase the catalyst stability. The pumice stone carrier was saturated with an alcoholic solution of the catalyst. The solvent was then removed by evaporation at 80 OC and the impregnated with the catalyst Pumice stone was left in a reaction vessel at 150 OC in a stream of nitrogen for about 2 hours dried so that about 30 g of the solid catalyst on the pumice stone with a Sieve sizes from 40 to 140 were available. The temperature of the reaction vessel was kept at the specified reaction temperature, the catalyst bed with Nitrogen was flowed through. The reaction gases were at 25 ° C in the specified Quantities fed in. Almost all of the water's brominated hydrocarbons were made caught in the first trap at 25 OC. The results are from the following Table.

Table I Gas feed rates at 25 ° C atmosphere - product composition pressure ml / min mol% catalyst tempe- rature- other example assemblage duration dibromobrominated brominated number setting ° C s C4H10 O2 Br2 N2 butene butane Butanone other 1 10% CuBr2 290 1.6 100 50 15 450 60 * 10 30 3% + KBr on pebble 2 10% CuBr2 300 1.5 100 62 16 400 25 40 35 10% KBr on pumice 3 6% CuBr2 300 1.5 100 -O- 45 500 45 40 -O- 15 Tetra-6% NaBr bromine on ethylene Bimestein 4 10% CuBr2 275 1.6 199 75 51HBr 400 40 25 35 3% KBr on pumice stone * trans-1,4-dibromobutene-2 (30%) cis-1,4-dibromobutene-2 (13%) 3,4-dibromobutene-1 (17%)

Claims (9)

Claims: 1. Process for the production of an alkene dihalide with carbon atoms, where n is 4 to 5, d a -d u r c h g e k e n n z e i c h n e t that a saturated aliphatic hydrocarbon with n carbon atoms continuously with free oxygen and halogen in the presence of a stabilized Copper (II) halide catalyst is oxibrominated by adding oxygen, halide and the hydrocarbon in the gas phase at controlled rates and Temperatures in a kept under certain pressure and temperature conditions Initiate reaction vessel, the rates and conditions depending on the n-value and structure, halogen, apparatus and catalyst concentration are chosen so that the formation of an alkene dihalide with n carbon atoms in a reaction medium is promoted, which also includes oxygen, halogen, unreacted hydrocarbons and contains water; and that the outflowing reaction medium for the recovery of the alkene dihalide is selectively condensed. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the catalyst is a mixture that by recording of an allogenide from the group consisting of potassium and ammonium halides became. 3. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the catalyst in a pumice stone carrier in an amount of about 5 to 10% by weight, based on the carrier, is impregnated. 4. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that n means 4, the halogen is bromine, and the selective condensation of the escaping reaction medium takes place at a temperature of at least 25 OC. 5. The method according to claim 4, d a d u r c h g e k e n n -z e i c h n e t that the molar feed ratio of oxygen to butane 0.2 to 0.6 and that molar feed ratio of bromine to butane is 0.1 to 0.5, and the reaction at Atmospheric pressure is carried out at 250 OC to 300 OC. 6. The method according to claim 4, d a d u r c h g e k e n n -z e i c h n e t that the hydrocarbon with about 100 ml / min, the oxygen with about 50 ml / min and the bromine at about 15 ml / min and the temperature the feed gas is about 25 OC. 7. The method according to claim 4, d a d u r c h g e k e n n -z e i c h n e t that the feed gases are also about 450 ml / min Nitrogen at 25 OC included. 8. Process for the preparation of 1,4-dibromobutene-2 and 3,4-dibromobutene-1, d a d u r c h e k e n n n z e i c h -n e t that normal butane with free oxygen and bromine in the presence of a stabilized copper (II) bromide catalyst continuously is oxibrominated by keeping oxygen, bromine and butane in the gas phase under controlled conditions Speeds and temperatures in one under certain pressure and temperature conditions held reaction vessel initiates, with the rates and conditions be selected according to the respective apparatus and the catalyst concentration, so that 1,4- and 3,4-dibromobutene are formed in a reaction medium that also contains oxygen, Contains bromine and butane; and that the outflowing reaction medium to obtain the Dibromobutene is selectively condensed. 9. The method according to claim 8, d a d u r c h g e k e n n -z e i c h n e t that the catalyst by taking up a bromide from the potassium and Ammonium bromide existing group is stabilized, the catalyst in a pumice stone is impregnated in an amount of 5 to 10% by weight, based on the pumice stone, the selective condensation of the effluent reaction medium at a temperature of at least 25 OC, the molar feed ratio is oxygen to butane 0.2 to 0.6 and the molar feed ratio Bromine too Butane is 0.1-0.5 and the reaction at atmospheric pressure at 250.degree. C. to 300 OC is carried out, the butane with about 100 ml / min, the oxygen with about 50 ml / min, the bromine is fed in at about 15 ml / min, the temperature of the feed gases is about 25 OC and the feed gases also contain 450 ml / min nitrogen at 25 ° C.