JPH0316934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for hydrogen reduction of aromatic hydroperoxides to produce the corresponding aromatic alcohols.

Known methods for producing aromatic alcohols from aromatic hydroperoxides include reduction with an aqueous solution of sulfites and hydrogen reduction in the presence of a hydrogenation catalyst.
In this issue, a method for producing α-cumyl alcohol by hydrogen reduction of cumene hydroperoxide using a catalyst supported on a carrier such as Raney nickel or palladium is presented. Methods for producing aromatic alcohols from group hydroperoxides are known.

This hydrogen reduction reaction of aromatic hydroperoxides is accompanied by a large amount of heat, so in order to prevent side reactions and promote the dissolution of hydrogen so that the reaction proceeds smoothly, we use water such as saturated hydrocarbons or aromatic hydrocarbons with saturated side chains. A solvent that is immiscible with is used.

However, this method of using a solvent has the disadvantage that the activity of the catalyst quickly decreases. Therefore, industrially, the amount of palladium-containing catalyst used is small, the catalyst activity does not decrease for a long time, and the catalyst can be used repeatedly. There is a need for the development of a method that can do this.

The method to meet this demand has so far been to reduce the tertiary aromatic hydroperoxide with hydrogen in the presence of a palladium catalyst with a palladium surface area of 10 to 200 m ² /g Pd, and to elute the palladium metal supported on the carrier. A method for preventing catalyst deterioration has been proposed (Japanese Patent Application Laid-open No. 167238/1983). but,
In this method, the palladium surface area is 200
It is essential that it is less than m ² /g・Pd,
If a palladium catalyst with a surface area greater than this value is used, the palladium elution rate will be significantly high and the activity will decline significantly over time.

The present inventors have conducted intensive research to overcome the above-mentioned drawbacks of the method for producing aromatic alcohols from aromatic hydroperoxides by hydrogen reduction in the presence of a palladium catalyst. As a result, the palladium surface area is 200 m ² /g. It was discovered that by using a palladium catalyst of Pd or higher and using a fixed bed solid-liquid contact reaction, surprisingly little elution of palladium was observed, and the desired aromatic alcohol could be obtained more efficiently. Based on this knowledge, we have completed the present invention.

That is, in the present invention, when reducing aromatic hydroperoxide with hydrogen, palladium has a surface area of 200
The present invention provides a method for producing an aromatic alcohol, characterized in that the reaction is carried out using a palladium-containing catalyst of m ² /g·Pd or more as a fixed bed. The purpose of the method of the present invention is to provide a method for industrially and efficiently producing aromatic alcohols useful as intermediates and solvents for various organic chemicals.

The present invention will be explained in more detail below.

Specific examples of aromatic hydroperoxides to which the method of the present invention is applied include α-phenylethyl hydroperoxide, cumene hydroperoxide, cymene hydroperoxide, diisopropylbenzene monohydroperoxide, diisopropylbenzene dihydroperoxide, etc. Aromatic hydroperoxides of 8 or more are preferred. The aromatic hydroperoxide may be dissolved in a suitable solvent, and this solvent is not particularly limited as long as it dissolves the aromatic hydroperoxide.
The aromatic hydroperoxide may also be a mixture with other substances, such as a mixture of unreacted cumene and tertiary hydroperoxide, which is usually obtained when cumene is oxidized to produce the corresponding hydroperoxide.

In the method of the present invention, the concentration of aromatic hydroperoxide in the solvent or mixture is appropriately determined depending on the type of aromatic hydroperoxide and the reaction conditions of the hydrogen reduction reaction, but is generally about 1 to 90% by weight. Defined by range.

The palladium-containing catalyst used in the present invention includes, in addition to palladium itself, activated carbon, alumina,
Carborundum, titania, silica alumina,
Any material may be used as long as it has palladium supported on a carrier such as silica and has the strength and particle size generally required for a fixed bed catalyst. Such a palladium-containing catalyst must have a palladium surface area of 200 m ² /g·Pd. This allows the catalyst to have extremely high activity and a long life. Furthermore, it is possible to sufficiently deal with increases in load due to changes in operating conditions. Furthermore, palladium elution is reduced even during long-term continuous operation. That is, efficient reduction with good conversion rate and selectivity is possible. In addition, the surface area of palladium (hereinafter referred to as
(abbreviated as MSA) was measured by carbon monoxide adsorption method.

When the MSA is less than 200 m ² /g·Pd, it becomes impossible to respond to load fluctuations due to fluctuations in operating conditions, and the conversion rate decreases. In addition, the amount of palladium eluted increases and the activity decreases over time. On the other hand, the upper limit of MSA is not particularly limited, but is preferably within a range of 350 m ² /g·Pd.

Such a palladium-containing catalyst with an MSA of 200 m ² /g・Pd or more is, for example, a catalyst with an average particle size of 0.5 mm.
A carrier having a diameter of 20 mm to 20 mm and carrying about 0.1 to 2% by weight of palladium can be mentioned.
The palladium-containing catalyst may also contain other noble metal compounds such as platinum, rhodium, ruthenium, etc. as co-catalysts. Note that the surface area of palladium can be adjusted according to a conventional method.

As a reactor for forming the fixed bed of the palladium-containing catalyst, a known fixed bed reactor such as a multi-tubular reactor or a single-tubular reactor can be used.

In the present invention, the optimum range of reaction conditions for hydrogen reduction is determined depending on the type of aromatic hydroperoxide, but the reaction temperature is as follows:
0 to 120°C is preferred. If the temperature is below 0°C, the progress of the reaction will be slow and a cooling means other than industrial water will be required.If the temperature exceeds 120°C, the self-decomposition reaction of aromatic hydroperoxides will be likely to be accelerated, resulting in an increase in by-products. I will invite you. For other reaction conditions, the reaction temperature ranges from 0 to 50Kg/
cm ² G, the amount of reaction liquid is 0.1 to 20 hr ^-1 in liquid standard hourly space velocity (LHSV) relative to the catalyst, or the amount of hydrogen gas supplied is about 1 to 10 times the stoichiometric amount of aromatic hydroperoxide. is preferred.

Thus, the present invention has a palladium surface area of 200
A fixed bed reactor packed with a palladium-containing catalyst of m ² /g·Pd or more is used, whereby the corresponding aromatic alcohol can be obtained almost quantitatively by the hydrogen reduction reaction of the aromatic hydroperoxide, Furthermore, the catalyst exhibits an excellent effect in that it does not lose its activity even during long-term reactions. In addition, palladium elution, loss and deterioration due to catalyst wear, which had disadvantages in the conventional suspension method, were not observed over a long period of time, and catalyst separation and recovery such as static separation and filtration were not required. There is no gender,
Aromatic alcohol can be produced stably and continuously for a long period of time.

Next, the present invention will be explained in more detail based on examples. In the compositional analysis in the examples, aromatic hydroperoxides were analyzed by iodometry, and other aromatic alcohols were analyzed by liquid chromatography.

Example 1 The reactor was equipped with a liquid flow inlet and a gas outlet with an inner diameter of 4 mm at the top, a gas inlet with an inner diameter of 4 mm at the bottom, and a metal sintered plate for gas dispersion at the bottom of the cylinder. A stainless steel cylindrical reactor with an inner diameter of 25 mm and a length of 600 mm, with a liquid outlet formed just above the reactor, and equipped with a thermometer and a pressure gauge was used. The reaction cylinder portion of this reactor is equipped with a jacket to allow cooling water to pass therethrough.
In addition, a 100-mesh stainless steel wire mesh was installed at the liquid outlet to prevent the catalyst from flowing out.

The reactor was filled with 180 ml of 2 mm diameter alumina spheres carrying 0.5% by weight of palladium and having a palladium surface area (MSA) of 295 m ² /g·Pd.
Nitrogen gas was introduced into the reactor through the gas inlet, and cumene was introduced through the liquid inlet into the reactor, and the pressure was adjusted to 3Kg/cm ²
After keeping the temperature constant at G, the nitrogen gas was changed to hydrogen gas, and the cumene was changed to cumene hydroperoxide (25.5% by weight cumene solution). At steady state, the feed molar ratio of H ₂ /cumene hydroperoxide is 2.5, and cumene hydroperoxide (hereinafter
Cumene solution (abbreviated as CHP) is
It was continuously supplied at a rate of LHSV2.0hr ^-1 .

The amount of cooling water in the jacket was adjusted so that the reaction temperature was 65°C or less at the hot spot (hereinafter abbreviated as THS) to stabilize the reaction. 5 hours after the start of the reaction, a sample was collected from the liquid outlet at THS 63℃ and analyzed. As a result, almost no CHP was detected, and dimethylphenyl carbinol (hereinafter abbreviated as DMPC) was produced almost quantitatively. .
CHP conversion rate 99.8 mol%, DMPC selectivity 100 mol%
It was hot.

Example 2 A gas inlet is provided at the top, a liquid-gas mixed phase outlet is provided at the bottom, a gas-liquid dispersion plate is provided at the top of the cylinder, and a 100-mesh stainless steel wire mesh is installed at the bottom to support the catalyst. A cylindrical reactor similar to that in Example 1 was used except for the attachment. In this reactor, an activated carbon molded product (1 mmφ, 1 mm) supporting 0.5% by weight of palladium was prepared using palladium MSA307.
200 ml of catalyst having m ² /g·Pd was charged.

A CHP-cumene solution with a CHP concentration of 8.0% by weight was added to this reactor at a rate of 500ml/hr (LHSV2.5hr ^-1 ).
Also hydrogen at 12.6Nl/hr (H ₂ /CHP molar ratio, 2.5)
was fed continuously at a rate of Reaction pressure is 3Kg/cm ²
G and continued operation without passing cooling water through the jacket.

5 hours after the start of the reaction, the THS was 74°C, and a sample was taken from the liquid outlet and analyzed, and the CHP conversion rate was 99.6.
A result of 99.7 mol% of DMPC selectivity was obtained. After 24 hours of continued operation under the same conditions,
CHP conversion rate 99.9 mol%, DMPC selectivity 99.9 mol%, CHP conversion rate 99.9 mol% even after 720 hours,
The DMPC selectivity was 99.9 mol%, and no decrease in activity was observed.

Analysis of the amount of palladium supported on the catalyst after 720 hours of operation revealed that it was 0.47% by weight, almost the same as the initial state.

Example 3 The catalyst was made by supporting 0.5 wt% palladium on alumina with a diameter of 2.0 mm, and the MSA of palladium was 296 m ² /
The reaction was carried out in the same manner as in Example 2 using the same reactor as in Example 2, except that the reactor was changed to one containing g.Pd.
Operation was carried out for 720 hours at THS temperature range of 65-78℃, CHP conversion rate 99.5-99.9 mol%, DMPC selectivity
A result of 99.6 to 99.9 mol% was obtained, and no decrease in activity was observed during this period.

Further, as in Example 2, the amount of palladium supported on the catalyst after use was analyzed, and it was found to be 0.46% by weight, which was almost the same as that in the initial state.

Comparative Example The reaction was carried out in exactly the same manner as in Example 2, except that 2.0 mm diameter alumina supported with 0.5 wt% palladium and MSA of 114 m ² /g・Pd was used as a catalyst, and the THS was 50. The temperature ranged from ~60℃.

After continuous operation for 720 hours after the start of the reaction, samples were periodically taken from the liquid outlet and analyzed.
CHP conversion rate 88.5-92.0 mol%, DMPC selectivity 99.6
~99.8 mol%, indicating a low CHP conversion rate. Further, when the amount of palladium supported on the catalyst after use was analyzed, a weight loss of 0.41% by weight was observed, which was 9%.

Claims (1)

[Claims] 1. A method for producing an aromatic alcohol, which comprises using a palladium-containing catalyst having a palladium surface area of 200 m ² /g·Pd or more as a fixed bed in hydrogen reduction of an aromatic hydroperoxide.