JPS6032498B2 - Method for regenerating esterification catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a palladium-based catalyst with an activated carbon support used in producing an unsaturated glycol gester by reacting a conjugated diene, a carboxylic acid, and molecular oxygen. It is.

Specifically, the present invention relates to a method for regenerating a catalyst for producing unsaturated glycol gester in which palladium and a specific metal are supported on activated carbon. It is known that a palladium-based catalyst is effective in producing an unsaturated glycol gester by reacting a conjugated diene, a carboxylic acid, and molecular oxygen.

The present inventors have discovered that a catalyst in which at least one selected from palladium, bismuth/selenium, antimony, and tellurium is supported on an activated carbon carrier is extremely excellent as a catalyst for producing unsaturated glycol gesters. However, even with such a catalyst, it is inevitable that its catalytic activity will gradually decrease after long-term use. There are various reasons for this decrease in catalyst activity, including the formation of carbon-containing deposits on the catalyst, which is generally accepted for this type of reaction and catalyst. Although the details are not necessarily clear, solid solutions and/or alloys are formed from palladium, which is a component in the catalyst, and at least one additive selected from bismuth, selenium, antimony, and tellurium. It is assumed that one of the reasons is that the catalyst changes due to the action of molecular oxygen under the esterification reaction conditions due to long-term use, resulting in a decrease in catalyst performance.

However, the regeneration treatment of noble metal catalysts whose activity has decreased is generally performed by oxidizing the deactivated catalyst with molecular oxygen at a temperature of 400°C to 600 qo to remove deposits on the catalyst and at the same time convert the precious metal into its corresponding oxide. Then, a method is used in which the produced oxide is re-reduced to a metallic state by an appropriate method.

However, such a general regeneration treatment method is not suitable as a regeneration method for a specific catalyst for producing unsaturated glycol gester.

That is, since the catalyst treated by the method of the present invention uses activated carbon as a catalyst carrier, treatment with molecular oxygen at high temperatures is undesirable because the carrier itself becomes actively combusted; If the treatment temperature is lowered to avoid this, the sufficient combustion effect of the catalyst deposits will not be achieved. Therefore, general regeneration methods for precious metal catalysts cannot be applied to such catalysts as they are. As a result of intensive research into a method for regenerating palladium-based catalysts on activated carbon carriers used in esterification reactions, the inventors of the present invention regenerated catalysts with reduced activity into catalysts with stable activity by contacting them with acetic acid and molecular oxygen. The present invention has been achieved by discovering the phenomenon of white water.

The object of the present invention is to provide an industrially useful method for regenerating a catalyst for producing unsaturated glycol gester,
The purpose of this is to support at least one member selected from palladium, bismuth, selenium, antimony and tellurium on activated carbon for producing unsaturated glycol gester from conjugated diene, carboxylic acid and molecular oxygen according to the present invention. This can be achieved very easily by contacting the prepared catalyst with acetic acid and molecular oxygen.

Next, the present invention will be explained in more detail.

The reaction for producing an unsaturated glycol gester from a conjugated diene, a carboxylic acid, and molecular oxygen is shown by the following general formula.

(In the formula, R and 6 represent a hydrogen atom or a lower alkyl group, and R7 represents a lower alkyl group.

) When butadiene and acetic acid are used as starting materials, 1,4-diacetoxybutene-2 is mainly produced. The catalyst to be regenerated by the method of the present invention is a catalyst that has been used in the above reaction and has lost its activity, and has palladium and at least one of bismuth, selenium, antimony, and tellurium supported on activated carbon.

Such catalysts can be prepared using common methods for preparing supported metal catalysts, such as palladium compounds such as palladium chloride and palladium acetate, as well as antimony compounds, bismuth compounds, selenium compounds and tellurium compounds. At least one substance is dissolved in a suitable solvent, activated carbon is added to the solution, the solvent is distilled off, the above components are attached to the activated carbon, and then the above components are dissolved in a stream of hydrogen or an organic compound with reducing power such as methanol. It is prepared by reduction or reduction with a well-known reducing agent such as hydrazine or formalin.

In some cases, the activated carbon may be treated with nitric acid in advance, or the catalyst may be repeatedly subjected to the above reduction treatment and oxidation treatment with molecular oxygen after supporting the active ingredient.
Performing a final reduction treatment is a preferred operation because it improves the activity of the catalyst. The palladium concentration on the carrier of the catalyst obtained in this way is generally 0.1 to 20% by weight, and the ratio of the added metals is usually 0.01 to 10 g atom per 1 g atom of palladium. That's about it. To regenerate the catalyst according to the method of the present invention, the catalyst whose activity has decreased is brought into contact with acetic acid and molecular oxygen at a temperature of room temperature to 200°C, preferably room temperature to 150°C, for at least 1 hour at normal pressure to 10°C. This is done by

Acetic acid may be used in gaseous or liquid form, and molecular oxygen may be used after being diluted with an inert gas such as nitrogen or argon. The catalyst can be brought into contact with acetic acid and molecular oxygen by mixing gaseous acetic acid and oxygen gas and flowing the mixture through the catalyst layer, or by immersing the catalyst in liquid acetic acid and supplying oxygen gas. Alternatively, a method of blowing oxygen gas can be adopted. As detailed above, according to the method of the present invention, a deactivated esterification catalyst can be regenerated by a simple operation of contacting it with acetic acid and molecular oxygen, and therefore has high industrial utility value.

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 4-6 mesh crushed charcoal 9.5k9 water 5.5
Add k9 and 6 wt% nitric acid aqueous solution 7.13k9,
It was maintained at 90-94 qo for 3 hours.

After cooling, nitric acid was removed by filtration in an oven, and palladium nitrate and tellurium were dissolved in nitric acid to obtain a palladium concentration of 16 t/ml, and an aqueous solution of 15.2 k9 with a tellurium concentration of 5.2 was added to 30 q0 for 3 hours. After holding, it was allowed to cool for 5 hours. The solids are then taken out of the oven and heated to a maximum of 13 mHg under a pressure of 24 mHg.
It was dried at 9x0 for 8 hours. The obtained catalyst (hereinafter referred to as catalyst)
It is called 1. ) contained 2.72% by weight of palladium and 0.49% by weight of tellurium (both values calculated on a single basis). 500 cc of the above catalyst-1 was packed into a stainless steel activation container with an inner diameter of 2.8 arcs (effective cross-sectional area of 5.4), and 65 cc of nitrogen containing 8% by volume of methanol gas was charged.
The temperature was raised at a rate of 50°C per hour while flowing at a flow rate of 0N〆'hr, and when it reached 400qC, it was maintained for 4 hours and then allowed to cool to room temperature in a nitrogen stream. Next, the flow gas was changed to nitrogen containing 2% by volume of oxygen gas, and the flow rate was 65%.
After being maintained for 1 hour at 300 pm while flowing at 0 N〆'hr, it was allowed to cool to room temperature in a nitrogen stream. Then,
The temperature was raised at a rate of 50 oo per hour while flowing nitrogen containing 8% by volume of methanol gas at a rate of 650 N/hr, held at 400 oo for 1 hour, cooled to room temperature in a nitrogen stream, and then 1 at 300 pm while flowing nitrogen containing 2% by volume of oxygen gas at 65 pm/hr.
After holding for a period of time, the mixture was cooled in a nitrogen stream to obtain catalyst-2. 25 cc of Catalyst-2 was placed in a heat-resistant glass activation container with an effective cross-sectional area of 5.0 mm, and hydrogen gas was heated to 3.2 mm. State evening/hr
The temperature was raised at a rate of 50°C per hour while circulating at a rate of
When the temperature reached 40,000, 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 the flow rate was 32.5 N/hr.
After being maintained at ~315q0 for 15 hours, it was cooled to room temperature in a nitrogen stream. Next, hydrogen gas 32.5N/hr
The temperature was increased at a rate of 5,000° 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 treatment. The obtained catalyst (
Hereinafter, it will be referred to as catalyst-3. ) contains 3.0% by weight of palladium and 0.55% by weight of tellurium (both values converted to single unit)
was contained. Catalyst 3 10cc (approximately 4) was packed into a stainless steel reaction tube with an inner diameter of 12 mm and an effective cross-sectional area of 0.848 mm, reaction pressure 60k9/carp, reaction temperature 100q0
In, 1,3-butadiene 0.122 hole'h
r, glacial acetic acid 2.8 holes/hr and oxygen (used diluted to 6% by volume with nitrogen) 0.257 mole'hr
The reaction was carried out continuously by distributing the mixture at a rate of .

The amount of diacetoxybutenes produced per hour of reaction time for catalyst 1 after reaction initiation 1 was 6.11 m
mole, but after i30 field time elapsed, it was 1.84m.
mole/evening - decreased to Cat/hr.

Next, the supply of only 1,3-butadiene was stopped to perform a four-time catalyst regeneration process, and then the supply of 1,3-butadiene was restarted, and the reaction was carried out in the same manner as above. As a result, reaction time 1 of catalyst 1 stuck after 9 hours of restarting the reaction.
The amount of diacetoxybutenes produced per hour is 3.12
It recovered to mmole. The amount of diacetoxybutenes produced 43 hours after restarting the reaction was 2.53 mole'-C.
At this point, the 1,3-butadiene reactor was stopped again and the catalyst was regenerated for 16 hours. After the regeneration was completed, the supply of 1,3-butadiene was started, and the amount of diacetoxybutenes produced after 6 periods was determined to be 2.95 mmole/night-Cat・h.
It was r. Comparative Example 1 Catalyst components were supported on activated carbon in accordance with the method of Example 1 to obtain a catalyst containing 2.81% by weight of palladium and 0.52% by weight of tellurium (both values calculated as a single substance).

The process was the same as that of Example 1 to obtain catalyst-2, except that 50 cc of the above catalyst was charged into a heat-resistant glass activation container with an effective cross-sectional area of 5.0 mm, and the gas flow rate was changed to 1/10. Similar treatment was performed.

25 cc of the above-treated catalyst was subjected to the same treatment as that used to obtain catalyst-3 in Example 1, resulting in 3.24% by weight of palladium and 0.62% by weight of tellurium (all values calculated as a single substance). A catalyst containing the following was obtained. Using the above catalyst, 1,3-ptadiene was reacted with acetic acid and oxygen under the same conditions as in Example 1.

The amount of diacetoxybutenes produced 3 hours after the start of the reaction was 5.77 mmole/cat·hr, 105
After insect time, the mole/evening-Cat·hr was 1.81.

At this point, the supply of 1,3-butadiene and glacial acetic acid was stopped, and the reaction solution was extracted from the catalyst layer.
However, at 100 qo, nitrogen gas containing 6% by volume of oxygen was continuously supplied at a rate of 96 N/hr for 90 hours.
Thereafter, the reaction was restarted under the same conditions as in Example 1, but the amount of diacetoxybutenes produced after 4 periods of restarting the reaction was 1.
52 mmole/day-Cat·h, and the activity of the catalyst had not recovered. Example 2 In Comparative Example 1, the supply of 1,3-butadiene was stopped 121 hours after restarting the reaction, the catalyst was regenerated with acetic acid and oxygen for 4 hours, and 1,3-butadiene was supplied again to restart the reaction. However, the amount of diacetoxybutenes produced after 3 feeding hours was 2.14 kite moles/evening cat.
・He recovered in hr.

Comparative Example 2 After restarting the reaction in Example 2, the supply of nitrogen containing 1,3-butadiene and 6% by volume of oxygen was stopped, and glacial acetic acid was added to the catalyst layer. Shoes ole/hr and nitrogen 4.3 mole/hr 60k
9/1, and was circulated at 100°C for 4 hours.

Claims (1)

[Claims] 1. When regenerating a catalyst in which activated carbon supports at least one member selected from palladium, bismuth, selenium, antimony, and tellurium for producing unsaturated glycol diester from conjugated diene, carboxylic acid, and molecular oxygen, A method for regenerating an esterification catalyst, comprising contacting the catalyst with acetic acid and molecular oxygen.