JPS62739B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a new catalyst for the selective hydrogenation of phenol to cyclohexanone and a method for making the same. In the hydrogenation of phenols using palladium catalysts, the activity of the catalyst, and especially the hydrogenation rate, decreases with continued use of the catalyst due to the presence of impurities in the hydrogenation reaction mixture that poison the catalyst. U.S. Pat. Nos. 3,692,845 and 3,187,050 disclose a method for purifying organic compounds such as phenol to be hydrogenated, but impurities introduced with the phenol and hydrogen gas and impurities generated during the hydrogenation process are Because of the accumulation over time, the poisoning of metal catalysts could not be completely eliminated on a large scale. In order to avoid the uneconomical process of disposing of the poisoned catalyst, and also to avoid the continuous use of the poisoned catalyst at the expense of a low hydrogenation rate, it is necessary to increase the hydrogenation rate and thereby increase the poisoned catalyst. It would be desirable to eliminate the disadvantages of continuous use of poisoned palladium catalysts. The hydrogenation of phenol to cyclohexanone is carried out using a ``carbon coated with palladium to increase its activity'', i.e., a substance that increases the catalytic activity is incorporated onto the surface of the catalyst before it is added to the hydrogenation reaction mixture. This is facilitated by the use of a catalyst. For example, U.S. Pat. No. 3,076,810 hydrogenates phenol to produce cyclohexanone using a sodium-promoted catalyst, i.e., a palladium catalyst modified by surface loading with sodium before addition to the reaction mixture. ing. A limited amount of alkaline reactant is also disclosed as an additive added to help accelerate the reaction when using the sodium-enhanced catalyst disclosed in that patent. However, such catalyst systems are not completely satisfactory, and research continues to develop improved methods and/or catalysts. Surprisingly, the present invention provides a significantly improved catalyst in the hydrogenation of phenol to cyclohexanone, and furthermore, the present invention is applicable to current plants. Additionally, the present invention provides a process that produces fewer by-products and can be operated at lower temperatures than current plants without any sacrifice in production rate. It is clear that reactions at relatively low temperatures are highly desirable for safety reasons. According to the present invention, we present a palladium catalyst for the hydrogenation of phenol to cyclohexanone,
Preferably, based on the weight of the catalyst, the
To provide a palladium catalyst whose activity is promoted with 1000 ppm of sodium, and which is characterized in that the surface of carbon particles having a diameter of 3 to 300 microns and a surface area of 100 to 2000 m ² /g is coated with palladium. be able to. In the presence of this palladium catalyst, the group consisting of alkali metal hydroxides, carbonates, phenates, bicarbonates and nitrates A small amount of locally sourced promoter selected from
Cyclohexanone can be produced by hydrogenating the phenol by contacting hydrogen with phenol containing ~300 ppm, preferably 11-150 ppm. U.S. Pat. No. 3,076,810 states that the formation of cyclohexanol is promoted when phenol contains a high concentration of an alkali-reactive compound, that is, 10 ppm or more, but the improved palladium-coated carbon of the present invention It has been discovered that the use of a catalyst not only increases the reaction rate but also reduces the production of cyclohexanol by incorporating 10-300 ppm of alkali metal into the phenol.
Although the reason for this surprising finding is not clear, unexpected elements of the invention include the three-way interaction between the in situ promoter, the novel catalyst of the invention, and the careful control of reaction temperature described above. (interaction) is believed to be included. The palladium catalyst of the present invention contains palladium as the catalytically active metal in elemental or compound form, and preferably 30 to 75% of the total palladium is present as elemental palladium, ie, zero-valent palladium. Palladium has a diameter of 3 to 300 microns and a surface area of 100 to 300 microns.
It is adsorbed onto the surface of a carrier consisting of 2000 m ² /g of carbon particles, preferably coating the surface thereof. Preferably, the catalyst has about 95 to 98 weight percent particles ranging from 4 to 150 microns in diameter. The amount of palladium incorporated into a particular carrier can vary widely, but preferably the catalyst contains about 0.1 to 50 weight percent palladium, more preferably about 0.2 to 10 weight percent palladium. Good and easily prepared catalysts are those containing 1 to 5 weight percent palladium on the charcoal surface. Additionally, the palladium catalysts of the present invention can contain catalytically active metals in addition to palladium. The catalytically active metal added in this way is selected from the group consisting of elements of the platinum series. Examples of platinum series elements are selected from the group consisting of ruthenium, rhodium, osmium, iridium, platinum and mixtures thereof. Preferred promoters for use in the hydrogenation of phenol to cyclohexanone utilizing the catalysts of the present invention are selected from the group consisting of sodium hydroxide, sodium carbonate, sodium carbonate, and mixtures thereof. Particularly preferred promoters are sodium hydroxide and sodium carbonate, with sodium carbonate being particularly preferred. A particular promoter may be added to the hydrogenation reaction mixture as a phenolic slurry containing up to about 25% by weight, preferably about 1 to 10% by weight of the promoter. Alternatively, the promoter can be added to the hydrogenation reaction mixture as an aqueous solution. The phenol used as a raw material for producing cyclohexanone using the catalyst of the present invention can be obtained by conventional methods, such as oxidation of cumene to form cumene hydroperoxide and decomposition of that hydroperoxide. However, phenols treated by the method of the present invention generally contain less than about 100 ppm of sulfur impurities and preferably contain less than about 100 ppm of sulfur impurities, including divalent sulfur.
10 ppm or less, sulfur impurities including tetravalent sulfur are about 20 ppm, and sulfur impurities including hexavalent sulfur are about 80 ppm, preferably about 40 ppm or less. Phenol contains iron (calculated as elemental iron) of 2 ppm or less, more preferably 1 ppm or less; and acetol, i.e. hydroxy-2-propanone, contains 100 ppm or less, more preferably 50 ppm.
It is as follows. Phenols hydrogenated according to the invention may also contain various impurities. These impurities are, for example, halogen compounds and harmful nitrogen compounds, ie nitrogen-containing compounds that inhibit the hydrogenation of phenol to cyclohexanone using a palladium catalyst. Typical harmful nitrogen compounds are aromatic amines, ammonia salts, polyamines, and tertiary and primary amines. Preferably, the halogen content in the phenol is 10 ppm or less, and the nitrogen content as a harmful nitrogen compound is 50 ppm or less. In the method of hydrogenating phenol to cyclohexanone using the catalyst of the present invention, a continuous method or a batch method is employed, and equipment commonly used in this method is used. The selected promoter is introduced into the hydrogenation reaction mixture before or during hydrogenation. Therefore, the temperature conditions during the addition of the promoter into the hydrogenation mixture are not critical and can be varied over a wide range. For example, the temperature at which the promoter is added to the hydrogenation reaction mixture can range from about 25°C to about 185°C, and the pressure can range from about atmospheric pressure to 300 psig. Improved hydrogenation rates are observed upon addition of the promoter of the present invention to the hydrogenation reaction mixture, but after addition of the selected promoter to the hydrogenation reaction mixture, the reaction mixture is heated to a temperature of about 135°C.
Even better results are obtained when maintained at 185°C and pressure 80-200 psig for 15-30 minutes. A selected on-site promoter is added to the hydrogenation reaction mixture and the reaction product is removed from the hydrogenation reaction vessel either continuously or in batches. Upon removal of the hydrogenated product from the reaction vessel, the palladium catalyst is recovered from the product stream and returned to the vessel for further phenol hydrogenation. Recovery of catalyst from the product stream is accomplished by conventional solids separation methods, such as centrifugation, vacuum mouth vortexing, and the like. The vessels used during hydrogenation may be conventional, and typical hydrogenation equipment may be used, such as the equipment described in US Pat. No. 3,076,810. The invention will now be described in further detail, in which percentages are by weight unless otherwise specified. The improved catalysts achieved by the process of the present invention and the improved hydrogenation rates utilized therewith contribute to the industry's use of vast amounts of palladium catalysts each year in the hydrogenation of phenols to cyclohexanone. This is extremely important when considering this. Furthermore, the on-site promoter used in the catalytic hydrogenation reaction of the present invention promotes the hydrogenation of phenol to cyclohexanone and improves the hydrogenation of cyclohexanol produced by overhydrogenation of the desired cyclohexanone product. It was unexpectedly discovered that the amount could be reduced. Therefore, the recovery of cyclohexanone by distillation from the hydrogenated product stream may result in the removal of undesired products, i.e.
It is not very complicated since the amount of cyclohexanol is small. Example 1 (Catalyst Preparation Method) This example illustrates one embodiment of an effective method for making the catalyst of the present invention. However, the method of this example is relatively expensive compared to the method of Example 2. Approximately 150 parts of a commercially available 5% palladium coated carbon catalyst was used as the starting material. A slurry is prepared by dissolving a commercially available palladium catalyst in an aqueous solution of sodium hydroxide.
It was evaporated to dryness according to the method of No. 3076810. The catalyst formed preferably contains 2500 to 10000 ppm sodium. Approximately 150 parts of sodium-promoted palladium-coated carbon catalyst are thoroughly mixed with 1850 parts of cyclohexanone and the mixture is passed at a rate of 2000 parts per hour through a continuous centrifuge operating at 3800 revolutions per minute. I let it happen. According to this method, the catalyst consisting of fine particles was removed from the centrifuge together with cyclohexanone. The size distribution of the catalyst collected in the centrifuge is 98-99% 4
microns and substantially all particles were within the range of 4 to 150 microns; palladium content was 0.6
-1.2% and sodium content was 0.25-0.40%. This catalyst is suitable for use in the process of the invention. On the other hand, although fine catalyst particles are recovered from cyclohexanone in a conventional manner, these fine catalyst particles are unsuitable for use in the process of the present invention. Example 2 (Production method of catalyst) 30% is 10 microns or less, 67% is 10 to 100 microns
% and a particle size distribution of 3% greater than 100 microns.
part was thoroughly mixed with 1850 parts of cyclohexanone and the mixture was then passed through a continuous centrifuge at 3800 revolutions per minute. By this method, charcoal particles composed of fine particles were passed through a centrifuge together with cyclohexanone. The charcoal particles collected in the centrifuge, after drying, consisted of about 100 parts of particles with a diameter of 10-100 microns and a surface area of about 1000 m ² /gram. To 100 parts of the charcoal formed were added 1000 parts of an aqueous solution of palladium chloride containing 5 parts of palladium and 3 parts of hydrochloric acid. This solution was gradually neutralized with sodium carbonate solution until pH=1.5. The mixture was stirred and vortexed.
The solid was dried at 100° C. for 8 hours and then impregnated with 80 parts of a solution containing 5 parts of sodium carbonate. 100~120℃
After drying at , the solid was charged into a cylindrical reactor flushed with hydrogen at 140°C. This catalyst was suitable for use in the present invention. Reference example 1 A: Soluble iron 1ppm or less, sulfur 2ppm or less, halogen 5ppm or less, nitrogen as a harmful nitrogen compound
A palladium-coated carbon catalyst made of about 1000 parts of phenol containing up to 40 ppm and 0.23 parts of sodium carbonate, activated with sodium and having a sodium content of 0.32%, and the catalyst has a diameter of about 4 to 150 microns and a surface area of 500 to 1500 m ² / gr carbon particles coated with about 0.93% palladium. This mixture is heated to 160°C in the presence of nitrogen in a reaction vessel, and then hydrogen is introduced through a diffuser located near the bottom of the vessel.
160 at a speed sufficient to maintain a pressure of 80 psig.
Stirred at a temperature of °C. Periodically, the reaction mixture was sampled and analyzed. The results obtained are shown in Table-1.

[Table] 0.1% or less of cyclohexyl in the reaction mixture
The presence of cyclohexanone was confirmed. At the end of the experiment, the catalyst was recovered and found to contain 0.93 percent palladium (60-75 percent total calculated as elemental palladium) and 0.76 percent sodium. B: Repeated method A. However, sodium carbonate was not added to the phenol. The results are shown in Table-2.

【table】

In addition, approximately 0.47% cyclohexyl-cyclohexanone was found to be in the reaction mixture at the end of the experiment. By comparing A and B, it can be seen that in the prior art, in-situ addition of more than 10 ppm of alkali metal promoter based on phenol results in a loss of selectivity, whereas the catalyst of the present invention has 100 ppm of sodium.
It can be seen that the selectivity is improved even when 230 ppm of sodium carbonate, equivalent to 230 ppm, is added to the phenol.
An unexpected feature of the present invention is the unique catalyst-promoter interaction of the present invention coupled with the relatively low reaction temperature. Reference Example 2 The procedure of Reference Example 1 A was repeated except that 100 ppm of sodium in the form of sodium hydroxide was added to the reaction mixture instead of sodium carbonate. The results obtained were similar to those obtained in Reference Example 1A. Reference Example 3 The procedure of Reference Example 1 A was repeated except that 100 ppm of sodium in the form of sodium carbonate was added to the reaction mixture instead of sodium carbonate. The results obtained were similar to those obtained in Reference Example 1A. Reference Example 4 This reference example proves the possibility of continuous operation of the hydrogenation method using the palladium catalyst of the present invention. The phenol used was the same as that used in Reference Example 1. In the first of a set of five stirred hydrogenation reaction vessels, 45,694 parts of phenol, 1.3 to 2.0 parts of sodium carbonate, and a sodium content of 0.25 to 2.0 parts per hour were added.
The surface of carbon particles having a diameter of about 5 to 150 microns and a surface area of about 1000 m ² /gr is a palladium-coated carbon catalyst with increased activity of 0.40%.
1200 parts per hour of a catalyst characterized in that it is coated with % palladium. Approximately 67% of the palladium on the surface of this catalyst exists as elemental palladium. Each hydrogenation reaction vessel is connected so that the reaction mixture flows through the five reaction vessels in about 3.1 hours.
The first container was set to be filled with hydrogen.
Pressure is between 80 and 200 psig. The temperature of each container is 179°C for the first container, 168°C for the second container, 166°C for the third container, 164°C for the fourth container, and 164°C for the fifth container.
It was 162℃. A major reason for safety is that the temperature of each container is at most 10° C. or higher than the atmospheric pressure boiling point of the reaction mixture present in the container. Approximately 24,570 parts per hour of distillate, primarily cyclohexanone, were separated from the first, second, and third vessels; this distillate was rectified to substantially pure cyclohexanone. The reaction mixture emerging from the fifth vessel is fed to a continuous centrifuge where the catalyst is separated from the crude cyclohexanone and the catalyst is recycled into the process. The crude cyclohexanone was rectified to recover substantially pure cyclohexanone which could be combined with the recovered cyclohexanone as described above. The recovery rate of cyclohexanone in this continuous operation, which was carried out for 7 days, was 42,856 parts per hour. Additionally, 684 parts of cyclohexanol, 1481 parts of phenol, and 211 parts of high-boiling byproducts were each recovered per hour. This process required only 3 parts per hour of make-up catalyst. Similar results were obtained by substituting sodium carbonate with an equivalent amount of sodium as sodium hydroxide or sodium carbonate. Reference example 5 In order to improve safety, the reaction temperature of each reaction vessel is
Container at 173℃, second container at 166℃, third container at 162℃
The method of Reference Example 4 was repeated except that the fourth container was heated to 159°C and the fifth container was heated to 156°C. With respect to operational safety, it is important that the temperature of each reaction vessel be maintained at or below the atmospheric boiling point of the reaction mixture within the reaction vessel. sodium carbonate 1
Palladium-coated carbon catalyst activated with sodium at 2 parts per hour and a sodium content of about 0.35% and about 0.9% of the surface of carbon particles having a diameter of about 3 to 32 microns and a surface area of about 1000 m ² /gr.
of palladium-coated catalyst per hour.
Phenol was fed into the first vessel at a rate of 45,550 parts per hour along with 1200 parts. A commercially available sodium-activated palladium-coated carbon catalyst containing about 1% sodium and about 5% palladium was added to the circulating catalyst as make-up catalyst at a rate of about 2.5 parts per hour. This make-up catalyst contains about 16.5 volume percent fines less than 3 microns in diameter, however, the majority of these fines were removed from the crude cyclohexanone process which was collected in a centrifuge. One example of make-up catalyst had the following size:

Table: In this example, the average production of cyclohexanone during the one month test period was 98 percent of the theoretical amount based on the phenol fed to the process. Cyclohexanone was produced at a low rate of about 610 parts per hour. At the end of this test, the circulating catalyst contained approximately 0.45% sodium and approximately 0.9% palladium.
It contained %. The circulating catalyst had the following sizes:

【table】

[Table] The make-up catalyst shows a fairly normal size range distribution, but that of the circulating catalyst is skewed towards larger particles and shows a skewed distribution.
We show that this combination of larger size-biased catalysts and field-available promoters promotes the selective hydrogenation of phenols to cyclohexanone; i.e., cyclohexanol and other byproducts. It can be considered that there is a tendency to lower the production and increase the production amount of cyclohexanone.

Claims (1)

[Claims] 1. Diameter 3 to 300 microns, surface area 100 to 2000
m ² /gram of carbon particles are coated with 0.2 to 10 weight percent palladium, based on the weight of the desired catalyst, and then activated with sodium in an amount of at least 1000 ppm, based on the total weight of the catalyst. A method for producing a catalyst for selective hydrogenation to cyclohexanone. 2 (a) Contains 0.2 to 10 weight percent palladium based on the total weight of the target catalyst, has a surface area of 100 to 2000 m ² /gram, and substantially all particles have a diameter of 300 microns or less, with a small portion of less than 3 microns. (b) Substantially the entire amount of the palladium catalyst supported on carbon particles having a diameter of less than 3 microns is supported on carbon particles having a diameter of 3 to 300 microns. A catalyst for the selective hydrogenation of phenol to cyclohexanone, comprising separating the palladium catalyst from the phenol to obtain a catalyst supported on relatively large carbon particles having excellent selectivity for the hydrogenation of phenol to cyclohexanone. How to manufacture.