DE3224509A1 - Process for the preparation of diacyloxybutenes - Google Patents

Abstract

Process for the preparation of diacyloxybutenes by reacting optionally substituted 1,3-butadiene with carboxylic acids and oxygen on a palladium- or platinum-containing catalyst in a reactor, where, in addition to the starting materials, alkanes or alkenes having one double bond, each of which contains 3 to 5 C atoms, are introduced and the alkanes or alkenes in gaseous form are recovered from the liquid reaction mixture after it has left the reactor and returned into the reactor in liquid form.

Description

Process for the preparation of diacyloxibutenes

The invention relates to a new process for the preparation of diacyloxibutenes (DABE) by reacting butadiene with carboxylic acids and oxygen on a catalyst.

From DE-PS 22 17 452 it is known that 1,4-diacyloxibutenes are obtained, if you add butadiene with oxygen and a carboxylic acid to a solid catalyst unsetzt, the Pd and at least one of the elements antimony, bismuth, tellurium and selenium contains. According to the information in De-OS 24 17 658, this synthesis from butadiene, Carry out oxygen and acetic acid in the gas or liquid phase also on catalysts, which contain platinum and at least one element of the 5th or 6th main group.

In DE-OS 25 42 925 the proposal is made to implement the Starting materials in a reactor with avoidance ...

perform a gas phase. From DE-CS 27 47 634 is known that a butadiene-containing C4 cracking fraction is used instead of butadiene can.

There are several prerequisites for a technical use of this process be fulfilled. For example, the productivity of the catalyst, i.e. that per unit of time and the amount of DABE produced by the catalyst or precious metal unit, a certain amount ert not fall below, aa otherwise the expenses for the relatively expensive Catalyst doesn't pay off. This value must also be long enough Period of time to avoid time-consuming and costly catalyst changes and avoid catalyst regeneration. It is also very important that the Selectivity of the synthesis, i.e. the proportion of DABE in the process product a certain Does not fall below the value. The so far known method of manufacture von DABE do not meet the requirements mentioned or only partially Way.

It has now been found that in the preparation of di acyloxibutenes du-ch reaction of optionally substituted 1,3-butadiene with carboxylic acids and oxygen on a palladium or platinum-containing catalyst, in the the reaction is carried out in a reactor avoiding a gas phase, especially advantageous results are obtained if the reactor is used in addition to the starting materials Initiates alkanes or alkenes with a double bond containing 3 to 5 carbon atoms, the alkanes or from the liquid reaction mixture after leaving the reactor Recover alkenes in gaseous form and put them in liquid form in the reactor returns.

The process according to the invention results in high yields in terms of time and achieves high selectivities which are maintained over particularly long periods of time permit.

Alkanes and alkenes containing 3 to 5 carbon atoms with a double bond are z.D. Alkanes such as n-butane and n-pentane or monounsaturated C4 or C5 hydrocarbons, such as 3-butene-1, butene-2, pentene or isobutene. The linear ones are preferred unsaturated hydrocarbons, of which the butenes are particularly suitable. In the process according to the invention, the alkanes or alkenes mentioned are added expediently dimensioned so that their amount by weight, based on the butadiene, aen ratio 1: oiæ corresponds to 4: 1.

That when these hydrocarbons are added to the butadiene-containing Reaction mixture so advantageous results are achieved is surprising because the mentioned hydrocarbons in contrast to butadiene under the conditions the reaction does not react and the reactor is practically in unchanged form again leaving. Surprisingly, the addition of the hydrocarbons mentioned causes one particularly favorable influence on the catalyst life. With the already known one Acetoxylation of butadiene, in which the butadiene is mixed with other C4 hydrocarbons used as a starting material, this effect was not recognized and not used, so that inadequate space-time yields were obtained with the known process.

Only through the proposal according to the invention, the inert hydrocarbons returned to a separate cycle, the desired beneficial Result can be achieved.

The actual catalytic conversion of the butadiene with the carboxylic acid and oxygen is in a manner known per se, for example at temperatures from 80 to 12000 and pressures from 1 to 100 bar. Instead of 1,3-butadiene you can also other conjugated diolefins, such as isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadienes, such as Piperztlen or 1,3-butadienes substituted by acyloxy groups such as 1-acetoxybutadiene, 1-acetoxy-2-methyl-1,3-butadiene or 1-acetoxy-3-methyl-1,3-butadiene can be used. Examples of carboxylic acids are low molecular weight fatty acids such as formic acid and acetic acid or propionic acid into consideration.

The catalysts containing palladium or platinum are preferred Supported catalysts, in which the active constituents on the support material, such as activated carbon, SiO2 or Al2O3 are applied. The active catalyst mass When in addition to palladium or platinum, other metals, ie Tellurium, copper, Contains antimony, selenium or 3ismuth.

Suitable catalysts of this type are, for example, in DE-PS 22 17 452, DE-OS 24 17 658 and DE-OS 29 43 407 described.

The new method is explained using the figure as follows: Fresh carboxylic acid (2) and the carboxylic acid recovered from the distillation (3) (4) is with part (6) of the liquid mixture leaving the reactor (8), exposed to oxygen (5) in a saturator (1). The resulting liquid phase with a circulation pump (7) into the reactor (8) filled with the catalyst directed. At the same time butadiene (9) and in a column (14) and in Separator (12) recovered inert alkanes or alkenes (17) and (16) in liquid Form pumped into the reactor.

The liquid reaction mixture (11) is after leaving the reactor divided into the already mentioned stream (6) and a secondary stream (13) in the separator (12) is relaxed. The weight ratio between the Stron (6) and the secondary stream (13) is expediently between the limits 1: 1 and 200: 1.

A liquid-gas phase separation takes place in the separator (12). The gas phase consisting essentially of the inert alkanes and alkenes becomes liquefied in a manner known per se and as described in (16) and (1G) in returned to the reactor (8). The liquid phase (15) is from (12) into the column (14) passed, in the residues of the inert alkanes or alkenes via (17) and (10) 1 ' returned to the reactor. So that is the cycle of these inert additives closed. The liquid reaction mixture (13), which is the bottom of the column (14) removes, and which consists essentially of the DAE and the carboxylic acid, will passed into a column (3) in which the carboxylic acid (4) is distilled overhead and the raw DABE wins as bottom product (19). The carboxylic acid distilled off overhead is returned to the saturator (1), closing the carboxylic acid cycle is. The raw DABE undergoes further purification or further processing fed.

The diacyloxibutenes which can be prepared by the process of the invention are valuable intermediates, e.g. for the production of 1,4-butenediol, tetrahydrofuran and 1,4-butanediol. The 3,4-butenediol-diacetate formed in subordinate names (Vinyl glycol diacetate) is used as an intermediate product in the manufacture of vitamins and others biologically active compounds suitable.

Those involved in the acetoxylation of isoprene or 1-acetoxy-2-methyl-1,3-butadiene obtained 2-methyl-1,4-diacetoxy-2-butenes or 1,1,4-triacetoxy-2-methyl-2-butenes are valuable intermediates e.g. for the synthesis of terpene compounds.

Example 1 1.25 l / h of fresh acetic acid are put into the saturator (1) (2), the acetic acid (4) recovered from column (3), 30 Nl / h oxygen (5) and 200 l / h of the liquid reaction discharge (6) are pumped. lit the help of a circulation pump (7) Add the oxygen-containing liquid mixture to the 460 g (600 ml) catalyst filled reactor (8) pressed.

The catalyst is a supported catalyst with SiO2 gel as a support, which contains 3.4 wt.% Pd, 0, u wt. Te and 10.3 wt.% O and a grain size of 1 to 3 mm. The synthesis to 1,4-diacetoxibutene-2 takes place in the reactor (3) at 95 ° C. and 70 bar instead of. Your reactor will be 0.15 l / h Butadiene (9) supplied. Simultaneously 0.45 l / h of n-butene (10) is passed into the reactor. The liquid discharge from the reactor (11) is divided in such a way that approx. 99.5 wt.% goes to the saturator (1) and 0.5 wt.% to the separator (12) are fed to (15).

A liquid phase separates out in separator (12), which is in the Column (14) is passed (15). The gas phase, which consists mainly of n-butene, is liquefied by cooling and fed to stream (10) via (16). In the column (14) residues of n-butene are distilled off, which are also fed into the reactor (17) will be. The bottom product of the column (14), which consists of 1,4-diacetoxibutene-2 and Acetic acid is passed into the column (3) (13), in which the acetic acid Distilled overhead and fed to the saturator (1) (4). Takes off as bottom product one of the column (3) the crude 1,4-diacetoxibutene-2.

The liquid reactor discharge (Stoffstron 11) contains 18 to 20% by weight of trans-1,4-diacetoxibutene-2, 2% by weight of cis-1,4-diacetoxibutene-2 and 2% by weight of 3,4-diacetoxibutene-1 This corresponds to a space-time yield of approx. 460 to 500 g of diacetoxibutenes per 1 catalyst per hour. The content of oligomeric and polymeric substances is less than 0.5% by weight. Even after an operating time of 1500 hours there is no decrease the K2talysatoraktivit = 'and selectivity determined.

Example 2 9 The procedure described in Example 1 is followed, whereby one however, isobutene is used instead of n-butene, a liquid reaction mixture is obtained (Stream 11), in which 19% by weight of trans-1,4-diacetoxibutene-2, 2 Ge cis-1,4-diacetoxibutene-2 and 2 wt. 3,4-diacetoxibutene-1 are included. The content of oligomers and polymers Substances is below 0.5 wt. This corresponds to a space-time yield of approx. 480 g of diacetoxibutenes per 1 catalyst and hour.

The roughness-time yield remains during the entire duration of the experiment almost 300 hours constant.

Sign.

Claims (3)

Method for the preparation of diacyloxibutenes by Reaction of optionally substituted 1,3-butadiene with carboxylic acids and oxygen on a catalyst containing palladium or platinum, in which the reaction in a reactor while avoiding a gas phase, characterized in that that one in the reactor in addition to the starting materials with alkanes or alkenes a double bond containing 3 to 5 carbon atoms, initiates from the liquid Reaction mixture after leaving the reactor, the alkanes or alkenes in gaseous form Recovered form and returned it in liquid form to the reactor. 2. The method according to claim 1, characterized in that dæ3 nan as Alkanes n-butane or n-pentane are used. 3. The method according to claim 1, characterized in nan as alkenes Putene or pentenes are used.