JPS6261008B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing pyrogallol by dehydrogenating 1,2,3-cyclohexanetriol. Pyrogallol is an extremely useful compound as an intermediate for organic synthesis of physiologically active substances, etc., but currently it is produced by thermal decomposition of gallic acid extracted from natural products, and its use is limited due to its high price. . The method of producing phenols by dehydrogenation of cyclohexanols is well known; for example, Dokl.Akad.Nank.SSSR, 185 , 145
(1969) described a method for producing catechol by dehydrogenation of 1,2-cyclohexanediol, as described by Dokl.
1 in Akad.Nank.SSSR, 198 , 1354 (1971),
A process for the preparation of pyrogallol by dehydrogenation of 2,3-cyclohexanetriol is described. In both methods, a catalyst in which palladium and potassium carbonate are supported on activated carbon is used, and gas phase dehydrogenation is carried out at a temperature of 300° C. in a hydrogen stream. The present inventors conducted a follow-up experiment on the reaction described in the above literature, and found that almost the same results were obtained in the dehydrogenation reaction of 1,2-cyclohexanediol, but in the dehydrogenation reaction of 1,2,3-cyclohexanetriol. The main product obtained was catechol, and the selectivity for pyrogallol was very small. The present inventors conducted various studies to increase the selectivity of pyrogallol in the dehydrogenation reaction of 1,2,3-cyclohexanetriol, and found that the selectivity of pyrogallol was dramatically improved when the reaction was carried out in an inert gas flow such as nitrogen gas. The present invention has been developed based on the discovery that the That is, the present invention is characterized in that when producing pyrogallol by dehydrogenating 1,2,3-cyclohexanetriol in the presence of a platinum group metal catalyst, the reaction is carried out in an inert gas flow. -In contrast to the dehydrogenation reaction of cyclohexanediol, which is a reaction in which the selectivity hardly changes whether it is carried out in a hydrogen stream or in an inert stream, in the method of the present invention, the selectivity for pyrogallol is Improved several times. The present invention will be explained in detail below. 1,2,3-cyclohexanetriol, which is a raw material in the method of the present invention, is produced by a known method. For example, it is produced by hydrating 1,2-epoxycyclohexan-3-ol obtained by oxidizing cyclohexene. 1, 2, 3-
There are three types of isomers of cyclohexanetriol due to differences in their steric structures, and any of them can be used in the method of the present invention. 1,2,3-cyclohexanetriol is supplied to the reaction system as it is or dissolved in a solvent such as water. Platinum group metals used as catalysts include ruthenium, rhodium, palladium, osmium,
Mention may be made of iridium and platinum, with particular preference given to iridium, rhodium and palladium.
These metals are preferably activated carbon, silica,
It is used supported on a carrier such as alumina. The platinum group metal can be supported on the carrier by a known method such as immersing the carrier in an aqueous solution of a platinum group metal compound, baking it, and then reducing it in a hydrogen stream. The amount of platinum group metal supported is preferably about 1 to 50% by weight. In the method of the present invention,
By using a catalyst in which an alkali metal compound is further added to a platinum group metal, the selectivity of pyrogallol can be further improved. Examples of alkali metal compounds include sulfates, carbonates, nitrates, bromides, chlorides, and organic acids such as sodium, potassium, rubidium, and cesium. These alkali metal compounds can be supported on a carrier by conventional methods such as dipping, evaporation to dryness, adsorption, or spraying. There is no particular restriction on the order. The amount of the alkali metal compound supported is not particularly limited, but is usually appropriately selected within the range of 0.3 to 30% by weight, preferably 1 to 10% by weight based on the total weight of the catalyst. The dehydrogenation reaction of 1,2,3-cyclohexanetriol according to the present invention is carried out at 100 to 500°C, preferably at 150°C while flowing an inert gas that does not participate in the reaction, such as nitrogen, argon, carbon dioxide, water vapor, or methane.
It is carried out at a temperature of ~350°C under normal pressure or reduced pressure. The above reaction can be carried out in a liquid phase or a gas phase, but under normal temperature and pressure conditions it is carried out in a gas phase, and also in order to prevent the elution of the alkali metal compound, which is one of the catalyst components. It is preferable. Furthermore, since the presence of water in the reaction system can extend the life of the catalyst, it is a very preferred embodiment to dissolve the raw material 1,2,3-cyclohexanetriol in water and supply it to the reaction system. be. In the method of the present invention, catechol, 1,2-cyclohexanedione, etc. are produced as by-products along with pyrogallol, but each can be separated and obtained by known separation means such as distillation and crystallization. Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 3, Comparative Example 1 2.5 g of palladium chloride was dissolved in 6 ml of concentrated hydrochloric acid,
5g of coconut husk charcoal manufactured by Daiichi Carbon Co., Ltd. was immersed in a solution diluted with water to make 15ml under reduced pressure, and left overnight.
It was heated to dryness at 70°C. After drying, the mixture was filled into a glass firing tube, heated at 100°C in a nitrogen stream for 1 hour, and then reduced at 400°C in a hydrogen stream to prepare a catalyst.
This catalyst was used in Examples 1 and 2 and Comparative Example 1. Palladium chloride-supported coconut shell charcoal obtained by drying in the same manner as above was immersed in a 10 wt% potassium sulfate aqueous solution for 1 hour, and then evaporated to dryness. After drying, it was reduced in the same manner as above, and 2.5 wt% potassium sulfate A palladium/activated carbon catalyst was prepared containing: This catalyst was used in Example 3. Fill a glass tube with 0.5ml of these catalysts and heat at 300℃.
After heating ^to
1,2,3-cyclohexanetriol (melting point
110-120℃, recrystallized from ethyl acetate) 10wt%
The aqueous solution was circulated at LHSV 2.7 hr ^-1 to carry out dehydrogenation reaction continuously at normal pressure. The product was cooled with ice water, separated into gas and liquid, and then analyzed by gas chromatography. Table 1 shows the conversion rate of 1,2,3-cyclohexanetriol and the selectivity of pyrogallol and catechol one hour after starting the reaction.

[Table] Comparative example 2 Palladium 1.5wt% and potassium carbonate 4wt%
^An activated carbon catalyst containing
The reaction was carried out in the same manner as in Example 1, except that the LHSV of the 1,2,3-cyclohexanetriol aqueous solution was changed to 0.22 hr ^-1 . As a result, 1, 2,
Conversion rate of 3-cyclohexanetriol is 100%
However, the selectivity of pyrogallol was only 4.8%.
The main product was catechol. Reference example Trans-1,2-cyclohexanediol instead of 1,2,3-cyclohexanetriol
A dehydrogenation reaction was carried out in the same manner as in Example 1 except that a 10wt% aqueous solution was used, and trans-
The conversion rate of 1,2-cyclohexanediol is 94.2
%, and the selectivity for catechol was 81.7%. When the same experiment was repeated by changing the circulating gas to hydrogen gas, the conversion rate was 87.1% and the selectivity of catechol was 82.4%, and there was almost no significant difference in the change in selectivity due to the difference in the circulating gas. Nakatsuta. Examples 4 to 6 According to the catalyst preparation method of Example 3, a palladium/activated carbon catalyst was loaded with 2.0 wt% potassium carbonate, 2.0 wt% sodium sulfate, and 4.0 wt% chloride. A catalyst supporting cesium was prepared. A dehydrogenation reaction was carried out under the same conditions as in Example 1 using these catalysts. Table 2 shows the conversion rate of 1,2,3-cyclohexanetriol and the selectivity of pyrogallol.

[Table] Examples 7 to 10 Platinum/activated carbon catalyst (platinum raw material; chloroplatinic acid), rhodium/activated carbon catalyst (rhodium raw material; rhodium trichloride), osmium/activated carbon catalyst were prepared according to the catalyst preparation method of Example 1. (Osmium raw material; Osmium tetrachloride) and a ruthenium/activated carbon catalyst (Ruthenium raw material; Ruthenium trichloride) were prepared. Using these catalysts, 1,2,3-cyclohexanetriol was dehydrogenated under the same conditions as in Example 1. Table 3 shows the conversion rate of 1,2,3-cyclohexanetriol and the selectivity of pyrogallol.

[Table] Examples 11, 12 Using a 5wt% iridium-supported activated carbon catalyst (manufactured by Nippon Engelhard) and a catalyst impregnated with 2wt% potassium carbonate, the reaction temperature was 350°C.
The dehydrogenation reaction of 1,2,3-cyclohexanetriol was carried out under the same conditions as in Example 1, except that the LHSV of the 10 wt% aqueous solution of 1,2,3-cyclohexanetriol was changed to 5.5 hr ^-1 . Summer. Table 4 shows the conversion rate of 1,2,3-cyclohexanetriol and the selectivity of pyrogallol.

【table】

Claims (1)

[Scope of Claims] 1. A method for producing pyrogallol, which comprises dehydrogenating 1,2,3-cyclohexanetriol in an inert gas stream in the presence of a platinum group metal catalyst. 2. In the method described in claim 1,
A method for producing pyrogallol using a catalyst in which an alkali metal compound is further added to a platinum group metal.