JPS6261009B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing pyrogallol by dehydrogenating 1,2,3-cyclohexanetriol. Furthermore, the present inventors discovered a method for obtaining pyrogallol by dehydrogenating 1,2,3-cyclohexanetriol in the presence of a platinum group metal catalyst such as palladium in an inert gas stream, and filed an application (Japanese Patent Application No. −
161097). The present inventor continued to make efforts to further increase the yield of pyrogallol, and as a result, discovered a new catalyst system and arrived at the present invention. A feature of the method of the present invention is that palladium and at least one selected from gold, silver, arsenic, and selenium are used as catalysts in the dehydrogenation reaction of 1,2,3-cyclohexanetriol, and a high yield of pyrogallol is achieved. can get. The present invention will be explained in detail below. The catalyst used is palladium with gold, silver, arsenic, or selenium added, and although there are slight differences in the optimum amount depending on the type of element to be added, The ratio is 2 to 200%, more preferably 5 to 50%. The catalyst is preferably used supported on a carrier. As the carrier, it is preferable to use a carrier that is porous and has a large surface area, such as activated carbon, silica, alumina, etc. Among them, activated carbon is particularly suitable. To prepare the catalyst, palladium and at least one suitable compound selected from gold, silver, arsenic and selenium, such as palladium chloride, palladium nitrate, chloroauric acid, silver acetate, arsenic acid,
A solution of selenic acid or the like is prepared separately or mixed, and the solution is impregnated onto a carrier by an appropriate means such as spraying, and then reduced by a known method such as heating in a hydrogen stream. can be done. Alternatively, it is also possible to prepare a catalyst by first preparing a catalyst on which only palladium is supported, and after reduction, further supporting gold, silver, arsenic, or selenium and performing re-reduction. The amount of palladium supported is 1 to 30
It is preferable to set it to about % by weight. In the method of the present invention, by using a catalyst to which an alkali metal compound is added, the activity can be increased and the yield of pyrogallol can be further improved. Alkali metal compounds include sulfates, carbonates, chlorides of sodium, potassium, rubidium, cesium, etc.
Examples include organic acid salts. These alkali metal compounds can be supported on a carrier by conventional methods such as immersion method and evaporation drying method. There is no particular restriction on the order in which they are carried. The amount of alkali metal compound supported is not particularly limited, but
It is usually selected as appropriate within the range of 0.3 to 30% by weight, preferably 1 to 10% by weight based on the total weight of the catalyst. In the dehydrogenation reaction of 1,2,3-cyclohexanetriol according to the method of the present invention, nitrogen, carbon dioxide,
It is preferable to carry out the reaction under the flow of an inert gas that does not participate in the reaction, such as water vapor or methane. The reaction can be carried out in liquid or gas phase. However, from the viewpoint of separation of the catalyst from the reaction product, it is preferable to carry out the reaction in a gas phase. The reaction temperature is suitably 50 to 500°C, preferably about 150 to 350°C. Although the reaction proceeds even under slightly increased pressure, it is more preferable to carry out the reaction under normal pressure or reduced pressure. Pyrogallol obtained by the method of the present invention is
It can be purified and separated from by-products such as catechol by separation means such as distillation and crystallization. Next, the present invention will be explained in more detail with reference to Examples. Example 1 2.5 g of palladium chloride was dissolved in 6 ml of concentrated hydrochloric acid,
To this was added 0.931 g of chloroauric acid, and water was added to make a total volume of 15 ml. In the aqueous solution, 5 g of coconut shell activated carbon was immersed under reduced pressure, left overnight, and then heated to dryness at 70°C. This material was further immersed in a 10% potassium sulfate aqueous solution for one hour, then evaporated to dryness, and then placed in a nitrogen stream.
After heating at 100°C for 1 hour, the mixture was reduced at 400°C in a hydrogen stream to prepare a palladium/gold/activated carbon catalyst containing 2.5% by weight of potassium sulfate. A glass tube was filled with 0.5 ml of this catalyst, and nitrogen gas was passed through the tube at a GHSV of 5000 hr ^-1 while heating the tube to 300°C. A 10 wt % aqueous solution of 1,2,3-cyclohexanetriol was passed through the reactor at a LHSV of 2.7 hr ^-1 to carry out a continuous dehydrogenation reaction at normal pressure. The product was cooled with ice water, separated into gas and liquid, and then analyzed by gas chromatography and high performance liquid chromatography. 1,2,3- at 1 hour after the start of the reaction
The conversion rate of cyclohexanetriol and the selectivity of pyrogallol were 86.8% and 71.4%, respectively. Examples 2 to 4 <Preparation of palladium-silver catalyst> 2.5 g of palladium chloride was dissolved in 6 ml of concentrated hydrochloric acid,
5 g of coconut shell activated carbon was immersed under reduced pressure in a solution made up to 15 ml by adding water, and after being left overnight, it was heated to dryness at 70°C. The mixture was then kept at 150°C in a nitrogen stream for 1 hour, and then the palladium was reduced at 400°C in a hydrogen stream for 3 hours. On the other hand, 0.243 g of silver nitrate was dissolved in 15 ml of water, the above-mentioned palladium-supported catalyst was immersed in this solution, dried, and then 2.5 wt% potassium sulfate was added in the same manner as in Example 1. carried it.
Next, reduction was performed at 400°C for 3 hours in a hydrogen stream,
A palladium-silver-potassium sulfate catalyst was obtained. <Preparation of palladium-arsenic catalyst> Dissolve 2.5 g of palladium chloride in 6 ml of concentrated hydrochloric acid,
Add 0.301g of arsenic acid to this and add water to make up the entire amount.
The mixture was diluted to 15 ml, dried to dryness, supported on potassium sulfate, and reduced in the same manner as in Example 1 to obtain a palladium-arsenic-potassium sulfate catalyst. <Preparation of palladium-selenium catalyst> Selenic acid (40wt% aqueous solution) instead of arsenic acid
A palladium-selenium-potassium sulfate catalyst was prepared in the same manner as the palladium-arsenic catalyst except that 0.819 g was used. Table 1 shows the results obtained by dehydrogenating 1,2,3-cyclohexanetriol using the above catalyst under the same conditions as in Example 1.

[Table] Comparative Example 1 Example 1 except that chloroauric acid was not used
A catalyst was prepared in the same manner as above, and the dehydrogenation reaction of 1,2,3-cyclohexanetriol was carried out under the same conditions as in Example 1 using the obtained palladium-potassium sulfate catalyst. -The conversion rate of cyclohexanetriol was 51.1%, and the selectivity of pyrogallol was 59.2%.

Claims (1)

[Claims] 1. A method for producing pyrogallol by dehydrogenating 1,2,3-cyclohexanetriol in the presence of a catalyst, characterized in that at least one member selected from palladium and gold, silver, arsenic and selenium is used as a catalyst. A method for producing pyrogallol.