JPS638930B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for producing diacetoxybutene by acetoxylating butadiene in the presence of palladium and tellurium. It is known that a catalyst in which palladium and tellurium are supported on activated carbon is used to produce diacetoxybutene by reacting butadiene with acetic acid and molecular oxygen (Japanese Patent Publication No. 52-12171,
52-29726 etc.) As a result of a detailed study of the acetoxylation reaction of butadiene, the present inventors found that, together with diacetoxybutene, a small amount of furan and acrolein, which are oxidation products of butadiene, were produced as by-products. The present invention was achieved by discovering that furan and acrolein accumulate in a reaction solution that is recycled, and that when the concentration of furan and acrolein in the solution exceeds a certain level, the catalytic activity decreases extremely quickly. It is something. The present invention will be explained in detail below. The catalyst used in the method of the present invention is one in which palladium and tellurium are supported on activated carbon.For the preparation, reduction and activation methods of the catalyst, see Japanese Patent Publications No. 52-29726, No. 52-29727, No. 52-
12685, 52-12686, Japanese Patent Application Publication No. 52-24180, Patent Application
53-54263 (Tokuko Shou 62-743), 53-77126 (Tokuko Sho 62-743)
61-20344). The amount of palladium supported is usually 0.1 to 20% by weight based on activated carbon.
0.01 to 10 gram atoms, preferably 0.05 to 5 gram atoms of tellurium are supported per gram atom of palladium. In the method of the present invention, the above catalyst is packed into a reactor and the reaction is carried out in a fixed bed. The butadiene used in this reaction does not necessarily have to be pure, and may contain an inert gas such as nitrogen or argon, or a saturated hydrocarbon such as methane, ethane or butane. Furthermore, the C ₄ fraction produced as a by-product during ethylene production can be used as is as a raw material for butadiene. Acetic acid, which is another raw material for the reaction, is not particularly limited and is sufficient in terms of quality as long as it satisfies JIS standards. However, when considering the selectivity of the reaction, the water content must be 20% (by weight) or less. It is desirable that the formic acid contained in acetic acid is 1.0% as much as possible from the viewpoint of the material of the reactor.
(weight)% or less. As a source of acetic acid, not only fresh acetic acid but also acetic acid recovered from the reaction system can be used. The amount of acetic acid used is within the range of stoichiometric or more and 60 mol or less per 1 mol of butadiene. Molecular oxygen may be pure or diluted with an inert gas such as nitrogen or argon, or a saturated hydrocarbon having 1 to 3 carbon atoms such as carbon dioxide, methane, or ethane, and air is conveniently used. . In any case, it is preferred that substantially no explosive mixture is formed in the reactor, and the oxygen concentration in the oxygen-containing gas usually ranges from 0.1 to 100% by volume, preferably from 1 to 100% by volume.
Selected within a range of 10% by volume. When carrying out this reaction, acetic acid acts both as a reaction raw material and as a reaction solvent, so there is no need to use a particular solvent, but a solvent that is inert to the acetoxylation reaction, such as a saturated hydrocarbon compound, Saturated aliphatic carboxylic acid esters, saturated aliphatic ethers, etc. may also be used. When a solvent is used, it is preferable that the amount of acetic acid used is within the above-mentioned application amount range, and in such a proportion that the sum of acetic acid and solvent is 70 parts by weight or less per 1 part by weight of butadiene. Butadiene, acetic acid, and optionally the solvent are introduced in a liquid state into the reactor, and the reaction is carried out at an SV of 0.1 to 100 hr ^-1 , preferably 0.5 to 20 hr ^-1 . The reaction temperature is selected in the range of 20 to 160°C, preferably 40 to 120°C, and the reaction pressure is selected in the range of normal pressure to 200Kg/cm ² , preferably 30 to 100Kg/cm ² . In addition, gases containing molecular oxygen
SV is appropriately selected within the range of 1 to 1500 hr ^-1 , preferably 5 to 500 hr ^-1 under the reaction conditions. In the method of the present invention, the acetoxylation reaction is reduced to 1/2 (F _i + A _i + F _p + A _p )≦1100...[] However, F _i : Concentration of furan in the liquid at the inlet of the catalyst layer (ppm) A _i : Catalyst Concentration of acrolein in the liquid at the inlet of the bed (ppm) F _p ; Concentration of furan in the liquid at the outlet of the catalyst bed (ppm) A _p ; Concentration of acrolein in the liquid at the outlet of the catalyst bed (ppm) be. Ideally, the lower limit of the formula [] is 0, but in this reaction, the by-products of furan and acrolein are unavoidable under almost any conditions, so it is difficult to keep the lower limit of the formula [] lower than 50. Have difficulty. The above acetoxylation reaction is usually carried out using excess acetic acid and without achieving a very high conversion rate of butadiene. Therefore, when carried out industrially, unreacted butadiene is recovered by simple distillation. Then, after distilling off low-boiling substances, acetic acid is distilled and recovered, and these butadiene and acetic acid are recycled to the reaction system and reused. At this time, furan and acrolein, which are by-produced during the acetoxylation reaction, are partially entrained in butadiene and partially remain contained in acetic acid and circulate through the reaction system, resulting in the concentration of furan and acrolein in the liquid at the inlet and outlet of the catalyst layer. gradually increases. Therefore, in order to carry out the reaction under conditions that satisfy the above formula [] according to the method of the present invention, the recovered butadiene is purified or substantially only butadiene is distilled out during distillation.
It is necessary to separate furan and acrolein from acetic acid and diacetoxybutene by distillation together with other low-boiling substances, thereby discharging the amount of furan and acrolein equivalent to by-products in one pass out of the system. In this reaction, as in normal chemical reactions, the higher the reaction temperature, the higher the reaction rate, but since the amount of by-products of furan and acrolein also increases, it is preferable to carry out the reaction at as low a temperature as possible. Furthermore, if the SV is too low, the amount of by-products of furan and acrolein will increase, so it is desirable not to make it too low. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 9.5 kg of crushed coconut charcoal of 4 to 6 meshes and 5.5 kg of water
Kg and 7.13 Kg of 60 wt% nitric acid aqueous solution, 90 ~
It was held at 94°C for 3 hours. After cooling, nitric acid was removed by filtration, and 15.2 kg of an aqueous solution with a palladium concentration of 16 g/tellurium concentration and a tellurium concentration of 5.2 g/1 obtained by dissolving palladium nitrate and tellurium in nitric acid was added, and the mixture was heated to 30°C for 30 minutes.
After holding for an hour, the mixture was allowed to cool for 5 hours. The solid was then removed and dried at a maximum temperature of 139° C. for 8 hours under a pressure of 240 mm Hg. The resulting unreduced catalyst is palladium
It contained 2.72% by weight and 0.49% by weight of tellurium (all values calculated as a single substance). The above unreduced catalyst 500c.c. has an inner diameter of 2.8cm (effective cross-sectional area
5.4 cm ² ) stainless steel reduction container (layer height
98cm), at 50°C per hour while flowing nitrogen containing 8% methanol gas by volume at a flow rate of 650N/hr.
The temperature was increased at a rate of 400°C, which was held for 4 hours, and then allowed to cool to room temperature in a nitrogen stream. Next, the flowing gas was changed to nitrogen containing 2% by volume of oxygen gas, and after being kept at 300° C. for 15 hours while flowing at a flow rate of 650 N/hr, it was allowed to cool to room temperature in a nitrogen stream. Next, the temperature was increased to 400°C at a rate of 50°C per hour while flowing nitrogen containing 8% by volume of methanol gas at a rate of 650N/hr.
After holding for 15 hours, it was cooled to room temperature in a nitrogen stream, and then nitrogen containing 2% by volume of oxygen gas was added.
The mixture was maintained at 300° C. for 1 hour while flowing at 650 N/hr, and then cooled in a nitrogen stream to obtain a reduced catalyst. 25 c.c. of the above reduced catalyst was charged into a heat-resistant glass activation container with an effective cross-sectional area of 5.0 cm ² , and hydrogen gas was added at 32.5N.
The temperature was raised at a rate of 50° C./hour while flowing at a rate of 400° C./hr, and when it reached 400° C., it was held for 4 hours and cooled to room temperature in a nitrogen stream. Next, the circulating gas was changed to nitrogen containing 2% by volume of oxygen gas, and while flowing at a flow rate of 32.5 N/hr, the
After being maintained at ℃ for 15 hours, it was cooled to room temperature in a nitrogen stream. Subsequently, the hydrogen gas was switched to 32.5 N/hr, the temperature was raised at a rate of 50°C per hour, and when it reached 400°C, it was held for 4 hours, and then allowed to cool to room temperature in a nitrogen stream to complete the activation process. The resulting catalyst contained 3.03% palladium and 0.55% tellurium by weight.
% by weight (all values are calculated as a single unit). A stainless steel reaction tube with an inner diameter of 12 mm and an effective cross-sectional area ^of 0.848 cm ² was filled with 10 cc.
−Butadiene 0.122 mole/hr, glacial acetic acid 2.5 mole/hr
hr and oxygen (used diluted to 6% by volume with nitrogen) at a rate of 0.257 mole/hr to carry out the reaction continuously. When 740 hours have passed since the reaction started, the amount of diacetoxybutene produced (total amount of 1,4-unit and 1,3-unit) per 1g of catalyst per hour is
It was 3.29 mmol/hr·g-cat. Next, when the glacial acetic acid was changed to glacial acetic acid with a furan content of 1100 ppm and the reaction was continued for an additional 550 hours, the amount of diacetoxybutene produced was 3.07 mmol/
It decreased to hr/g-cat. Furthermore, the concentrations of furan and acrolein in the liquid at the outlet of the catalyst layer at this time were 1000 ppm and 100 ppm, respectively.
Table 2 shows the rate of decrease in catalyst activity per 1000 hours. Example 2 A reaction was started in the same manner as in Example 1 using a catalyst prepared in the same manner as in Example 1. After 1700 hours, the amount of diacetoxybutene produced was 2.98
It was mmol/hr・g-cat. Then, glacial acetic acid was added to the acrolein content of 890ppm.
When the reaction was continued for an additional 650 hours by switching to glacial acetic acid, the amount of diacetoxybutene produced was 2.82 m
It decreased to mol/hr·g-cat. At this time, the concentrations of furan and acrolein in the liquid at the catalyst bed outlet were 100 ppm and 890 ppm, respectively.
Table 2 shows the rate of decrease in catalyst activity per 1000 hours. Example 3 Using a catalyst prepared in the same manner as in Example 1,
The reaction was started in the same manner as in Example 1. The amount of diacetoxybutene produced after 750 hours was 2.98m
mol/hr・g-cat, and the amount of diacetoxybutene produced after 1150 hours is 2.76 mmol/hr・g.
-It was cat. During this period, the concentrations of furan and acrolein in the liquid at the outlet of the catalyst bed are respectively
They were 80ppm and 90ppm. Table 2 shows the rate of decrease in catalyst activity per 1000 hours. Comparative Examples 1 and 2 Using a catalyst prepared in the same manner as in Example 1, a reaction was started under the same reaction conditions as in Example 1. A summary of the reaction is shown in Table-1. That is, in Comparative Example 1, the reaction time was changed from 550 hours to 1100 hours.
The reaction was carried out using acetic acid containing 4600 ppm of furan over a period of time, and in Comparative Example 2, the reaction was carried out using acetic acid containing 3690 ppm of furan and 880 ppm of acrolein for a reaction time of 2400 to 2700 hours.

[Table] Table 2 shows the rate of decrease in catalyst activity per 1000 hours.

[Table] Example 4 In Comparative Example 2, when 2700 hours had elapsed, the concentration of furan and acrolein in the liquid at the inlet of the catalyst layer was reduced to 0, and the reaction was continued for an additional 150 hours.
The concentrations of furan and acrolein in the liquid at the outlet of the catalyst bed are 90 ppm and 110 ppm, respectively.
The amount of diacetoxybutene produced is 1.32 mmol/hr・
It recovered to g-cat.

Claims (1)

[Claims] 1. Butadiene, acetic acid, and molecular oxygen are passed through a catalyst bed filled with a catalyst in which palladium and tellurium are supported on activated carbon to acetoxylate the butadiene, and unreacted butadiene and In the method for producing diacetoxybutene, which involves circulating acetic acid into the reaction zone, the acetoxylation reaction can be carried out using the formula () by discharging the furan and acrolein in the recycled butadiene and acetic acid to the outside of the reaction system. 1/2 (Fi + Ai + Fo + Ao) ≦ 1100 ... () (In the formula, Fi and Ai respectively represent the concentration of furan and acrolein in the liquid at the inlet of the catalyst layer (ppm),
(Fo and Ao represent the concentration (ppm) of furan and acrolein in the liquid at the outlet of the catalyst layer, respectively).