JPH088995B2 - Method for producing neutral palladium catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to palladium particles on a carrier such as alumina, silica and activated carbon, which is used when various organic chemical reactions, especially hydrogenation reactions of organic compounds are carried out. The present invention relates to a method for producing a neutral palladium catalyst which is loaded with.

(Prior Art and Problems Thereof) Palladium-supported catalysts have been widely used as catalysts for various organic reactions such as hydrogenation reactions of organic compounds. These conventional palladium-supported catalysts are manufactured by immersing a carrier such as alumina, silica and activated carbon in an aqueous solution of chloropalladic acid and reducing the impregnated palladium compound. However, in this method, since the chloropalladic acid is strongly acidic and the carrier is porous and has a high adsorptive capacity, even after sufficient reduction and sufficient washing with water, strongly acidic substances such as hydrochloric acid are adsorbed.

Therefore, the palladium-supported catalyst produced by the method exhibits acidity, and the pH when the catalyst is suspended in water or the like is 6.5.
The pH becomes further below, and the pH is further lowered when operations such as heating and pressurization are performed.

Further, when this method is used, there is a drawback in that a stainless steel container is corroded and rendered unusable, and chlorine, which often adversely affects the synthesis of organic compounds, remains.

When the above palladium-supported catalyst is used in the process of synthesizing a complex valuable compound having a wide variety of functional groups (for example, pharmaceuticals and agricultural chemicals), some functional groups are decomposed due to the presence of chlorine in an acidic atmosphere due to a decrease in pH or the presence of chlorine. Or may be converted into another functional group, resulting in a decrease in yield.

In order to solve the drawbacks, it has been attempted to protect the functional group with a predetermined protecting group to improve the yield, but the number of steps is significantly increased, and thus the yield is improved as a whole as a whole. In addition, there is a new drawback that economic efficiency is lowered due to increase in reagents used and time consumed.

(Object of the Invention) The present invention has been made to solve the above-mentioned drawbacks, and the pH when suspended in water is in the neutral range of about 6.
The aim is to provide a palladium catalyst in the range of 5 to 7.5.

(Means for Solving the Problems) The present invention is to dip a carrier in a solution containing a diacodiaminopalladium salt to impregnate the diacodiaminopalladium salt on the carrier, and to impregnate the diacodiaminopalladium salt. Is a method for producing a neutral palladium catalyst.

 Hereinafter, the present invention will be described in detail.

The present invention, in supporting palladium on a carrier, by using a weakly acidic diacodiaminopalladium salt instead of chloropalladic acid, which is strongly acidic, in the manufacturing process of the palladium-supported catalyst, the carrier or manufactured. The main feature of the palladium-supported catalyst is to prevent the acidic substance from being present in the catalyst obtained by avoiding contact with an acidic atmosphere, and in some cases, avoiding contact between the chlorine-containing compound and the carrier. In addition, chlorine that tends to adversely affect the synthesis reaction does not remain in the obtained catalyst.

The diacodiaminopalladium salt used in the present invention includes [Pd (H ₂ O) ₂ (NH ₃ ) ₂ ] SO ₄ and [Pd (H ₂ O) ₂ (NH ₃ ).
₂ ] (clO ₄ ) ₂ , [Pd (H ₂ O) ₂ (NH ₃ ) ₂ ] (NO ₃ ) ₂
There is. The salt is a complex in which neutral H ₂ O and weakly acidic NH ₃ ^— are coordinated around palladium and NO ₃ ions and the like coexist, and the salt is weakly acidic as a whole, and the diacodiaminopalladium salt is present. Does not contain chlorine unless used with chloride. Therefore, when nitrate is used, it is weak acidic NH ₄ NO ₃ that may be adsorbed to the catalyst obtained after reduction, and the obtained catalyst exhibits weak acidity and does not exhibit strong acidity.

Although such an effect can be obtained by using dinitrodiaminopalladium instead of the diacodiaminopalladium salt of the present invention, the acocomplex of the present invention has a very large solubility in water, and the liquid amount during the operation is considerably large. It becomes possible to decrease or increase the amount of palladium supported with the same liquid amount.

Further, as a carrier to be used, a weakly acidic compound and a weakly basic carrier can be prepared by appropriately selecting a carrier whose suspension has a weakly basic pH of 8 to 11 when suspended in water. The combination of the above makes it possible to obtain a neutral catalyst.

The step of the method of the present invention using the diacodiaminopalladium salt, that is, a solution of the diacodiaminopalladium salt is supported on a carrier, the salt is impregnated into the carrier, and the salt is reduced to bring palladium onto the carrier. As the method of supporting, the conventional method can be used without any limitation. For example, a carrier such as alumina, silica, and activated carbon can be used as the carrier, an aqueous solution can be used as the solution, and reduction in a hydrogen stream can be used as the reduction method.

Hereinafter, examples of the method of the present invention will be described, but the examples do not limit the present invention.

(Example 1) 4 g of dichlorodiaminopalladium [Pdcl ₂ (NH ₃ ) ₂ ] and 3.2 g of silver nitrate were simultaneously dissolved in 160 ml of water, the precipitate of silver chloride formed was filtered, and 38 g of powdered activated carbon A was suspended in the filtrate. Made cloudy. The suspension was refluxed under stirring at 100 ° C. for 2 hours to completely adsorb the palladium compound on the activated carbon.

After cooling to room temperature, hydrogen gas was blown in at a rate of 1 / min for 1 hour to reduce the palladium compound. After the reduction was completed, it was filtered off and dried in vacuum at 50 ° C. to obtain about 40 g of 5% palladium / activated carbon catalyst A.

It should be noted that 4 g of dinitrodiaminopalladium was used in place of 4 g of diacodiaminopalladium, and 800 ml of water was required to dissolve this in water.

(Example 2) 5% palladium / activated carbon catalysts B and C were respectively prepared in the same manner as in Example 1 by using activated carbons B and C whose pH when suspended in water was different from that of activated carbon A of Example 1. Obtained.

Comparative Example 5% palladium / activated carbon catalyst D was obtained in the same manner as in Examples 1 and 2 by adding 38 g of activated carbon A used in Example 1 to 800 ml of an aqueous solution of chloropalladic acid having a palladium concentration of 2.5 g /.

The table below shows the pH of each of the activated carbons A to C and the catalysts A to D when suspended in water, and the hydrogen pressure treatment (H ₂ 4 kg / cm ² , 3 h) in an autoclave. Each pH is shown.

The measurement of the pH was carried out by suspending 1 g of each sample in 10 ml of water. The catalyst A using activated carbon A whose pH is weakly basic shows a substantially neutral pH even after the hydrogen pressure treatment, whereas the catalysts B and C using activated carbons B and C whose pH is neutral or weakly acidic.
It can be seen that shows acidity.

It is also seen that even when the weakly basic activated carbon A is used, the catalyst D prepared by using the aqueous chloropalladic acid solution exhibits strong acidity. Further, when the suspension of the catalyst A after the hydrogen pressure treatment was filtered and an aqueous silver nitrate solution was added dropwise to the filtrate, it was confirmed that cloudiness due to silver chloride did not occur and that chlorine ion did not exist.

(Effect of the Invention) The present invention is different from conventional chloropalladic acid in producing a palladium catalyst by supporting a palladium compound on a carrier, does not contain a strongly acidic substance, and has a very high solubility. Diaminopalladium salt is used. Therefore, the obtained palladium catalyst does not contain a strongly acidic substance such as hydrochloric acid, and even if the palladium catalyst is used for various reactions of an organic compound that is susceptible to a decomposition reaction due to a decrease in pH, the decomposition of the organic compound does not occur. The desired organic reaction can be carried out without occurring.

Moreover, since the solubility of the diacodiaminopalladium salt in water is very large as described above, it is possible to significantly reduce the amount of liquid used, and to downsize the device and increase the amount of palladium supported in the same liquid amount. The benefits can be realized.

Further, when a chlorine ion-free diacodiaminopalladium nitrate, for example, is used as the diacodiaminopalladium salt, it is possible to avoid the presence of chloride ions, which often adversely affect the organic reaction, in the resulting catalyst, and to obtain the desired organic compound. It becomes possible to carry out a chemical reaction.

Claims (4)

[Claims] 1. Neutral palladium comprising dipping a carrier in a solution containing a diacodiaminopalladium salt to impregnate the diacodiaminopalladium salt on the carrier and reducing the impregnated diacodiaminopalladium salt. Method for producing catalyst. 2. The production method according to claim 1, wherein the diacodiaminopalladium salt is a nitrate. 3. The method according to claim 1 or 2, wherein the carrier is an inorganic compound selected from alumina, silica and activated carbon. 4. The production method according to any one of claims 1 to 3, wherein a carrier having a pH of 8 to 11 when suspended in water is used.