CZ298923B6 - Catalyst for hydrogenation of 4-nitrosodiphenylamine with hydrogen to 4-aminodiphenylamine - Google Patents

Abstract

In the present invention, there is disclosed a catalyst for hydrogenation of 4-nitrosodiphenylamine sodium salt solution containing 1 to 5 percent by weight of palladium on activated charcoal and further 0.5 to 6 percent by weight of iron as counted on the content of palladium. When the catalyst palladium content amounts from 2 to 5 percent by weight, it preferably contains 2 to 4 percent by weight of iron related to the palladium content. There is also disclosed a process for preparing such a catalyst, wherein the process comprises treating a water suspension of activated charcoal and dissolved salts of Pd and Fe with alkali metal carbonates or hydrogen carbonates to thereby precipitating Pd and Fe oxides on the activated charcoal. Subsequently, a reduction, preferably with formaldehyde or hydrazine provides a catalyst for hydrogenation of 4-nitrosodiphenylamine sodium salt solution

Description

The catalyst for the hydrogenation of the 4-nitrosodiphenylamine sodium salt contains 1 to 5 wt. % palladium on activated carbon and further 0.5 to 6 wt. iron, calculated on contained palladium. Preferably, the palladium content of the catalyst is 2 to 5 wt. contains 2 to 4 wt. iron on contained palladium. The process for preparing the catalyst consists in treating the aqueous suspension of activated carbon with the dissolved salts of Pd and Fe with alkali metal carbonates or bicarbonates, thereby precipitating the oxides of Pd and Fe into activated carbon. Subsequent reduction, preferably with formaldehyde or hydrazine, provides a catalyst for the hydrogenation of a solution of the sodium salt of 4-nitrosodiphenylamine.

Catalyst for the hydrogenation of 4-nitrosodiphenylamine with hydrogen to 4-aminodiphenylamine

Technical field

The present invention relates to the composition and preparation of a palladium-on-carbon catalyst for the catalytic reduction of 4-nitrosodiphenylamine (NODFA) by hydrogen to 4-aminodiphenylamine (ADFA).

BACKGROUND OF THE INVENTION

4-Nitrosodiphenylamine is hydrogenated as the sodium salt in aqueous methanolic solution in the presence of toluene (CS AO 184 062).

A suitable carrier for palladium in this case is activated carbon, which is well resistant to the alkaline environment. The catalyst is usually prepared by precipitation of PdO from salts to activated carbon and subsequent reduction of Pd to metal on a wet road (CS AO 179 618).

In the hydrogenation of NODFA, the catalyst is deactivated, in part probably by dissolving Pd. When testing catalysts in the laboratory, the depth of catalyst deactivation is reflected in the measured effective activity. However, individual catalysts may also differ in actual activity.

Hydrogenation of the sodium salt of 4-nitrosodiphenylamine is a specific reaction and we have not experimentally found a relationship between the catalyst activity measured by the standard nitrobenzene hydrogenation method and the NODFA hydrogenation activity. For this specific reaction, we have not found information in the literature on catalyst activity. In a review by P. Albers et al. (Journal of Molecular Catalysis A: Chemical 173 (2001) p. 275) mentions the deactivation of the Pd catalyst in the hydrogenation of nitro compounds to amines caused by the dissolution of Pd in an amine solution. To minimize this phenomenon, it is recommended to work with a lower catalyst concentration or a lower Pd concentration on activated carbon, e.g. 3% instead of 5% Pd. The positive effect of iron admixture on Pt or Pd on activity was observed in the hydrogenation of nitrobenzene (Catalysis of Organic Reactions, Marcel Dekker, New York, 1984, p. 335) and 2,4-dinitrotoluene (Catal. Lett. 10 (1991) p. 215). Article by R. Bachir et al. (Applied Catalysis A: General 164 (1997) p. 313) deals with the effect of Fe on the activity and selectivity of Pd on alumina in isoprene hydrogenation.

SUMMARY OF THE INVENTION

It has now been found that a very active and stable palladium catalyst (Pd) on activated carbon for the hydrogenation of a 4-nitrosodiphenylamine sodium salt solution is obtained by enriching it with 0.5 to 6 wt. iron (Fe) calculated on contained Pd. The catalyst is prepared by a conventional procedure by precipitation of oxides from solutions of palladium salts and iron salts with an alkali carbonate or bicarbonate followed by reduction of PdO to Pd with a solution of formaldehyde or hydrazine. However, other reducing agents may also be used.

With an optimum iron content of 2 to 4 wt. calculated on the contained Pd, the activity of the catalyst for hydrogenation of the sodium salt of 4-nitrosodiphenylamine is significantly increased. Interestingly, the activity in the standard nitrobenzene hydrogenation assay is the same for both the iron-containing catalyst and the iron-free palladium catalyst. We cannot tell how much iron actually increases

The activity of palladium and the extent to which it reduces the extent of catalyst deactivation. When Pd is applied to iron-doped activated carbon, the extent of dissolution of Pd into solution is reduced.

Examples

Example 1

Preparation of catalyst without Fe (comparative)

A solution of 5 g of sodium carbonate in 180 ml of distilled water is prepared. 20 g of activated carbon, calculated on dry weight, are metered into the solution. The coal slurry was well mixed and 10.31 ml of a 60 g / l PdCl ₂ solution was added with stirring. The solution is added dropwise evenly over 30 min. After introduction of the PdCl ₂ solution, the suspension is heated to 95 ° C for 60 minutes. At this temperature, 6 ml of formaldehyde are added uniformly over 5 minutes. Then the temperature is raised to

98 ° C and held for 40 minutes. Then the suspension is cooled to 80 ° C and the catalyst is filtered off by sintering. The filter cake is washed 5 times with 30 ml each of 0.2 wt. Na ₂ CO ₃ . Finally, the catalyst is washed twice with 30 ml of distilled water.

Example 2

Preparation of a catalyst containing 2 wt. Fe

A solution of 5 g of sodium carbonate in 180 ml of distilled water is prepared. 20 g of activated carbon, calculated on dry weight, are metered into the solution. In 10.31 ml _PdCl2 solution (concentration 60 g / 1) was dissolved 0.0599 g of FeCl ₃ .6H ₂ O. The slurry of coal is well mixed with stirring with a solution weighing přidá25 PdCl ₂ + FeCl ₃ .6H ₂ O The solution is added dropwise evenly over 30 min. After the solution was introduced, the suspension was heated to 95 ° C for 60 minutes. At this temperature, 6 ml of formaldehyde are added uniformly over 5 minutes. The temperature was then raised to 98 ° C and maintained at that temperature for 40 minutes. Then the suspension is cooled to 80 ° C and the catalyst is filtered off by sintering. Wash the filter cake 5 times with 30 ml each of 0.2% Na ₂ CO ₃ . Finally, the catalyst is washed twice with 30 ml of distilled water.

Example 3

Preparation of a catalyst containing 3 wt. Fe

A solution of 5 g of sodium carbonate in 180 ml of distilled water is prepared. 20 g of activated carbon, calculated on dry weight, are metered into the solution. In 10.31 ml _PdCl2 solution (concentration 60 g / 1) was dissolved 0.0899 g of FeCl ₃ .6H ₂ O. The slurry of coal is well mixed with stirring, a solution of PdCl ₂ + O ₂ solution FeCl3.6H is added dropwise evenly over 30 min. After the solution was introduced, the suspension was heated to 95 ° C for 60 minutes. At this temperature, 9.4 ml of hydrazine hydrate are added uniformly over 5 minutes. The temperature was then raised to 98 ° C and maintained at that temperature for 40 minutes. Then the suspension is cooled to 80 ° C and the catalyst is filtered off by sintering. Wash the filter cake 5 times with 30 ml each of 0.2% Na ₂ CO ₃ . Finally, the catalyst is washed twice with 30 ml of distilled water.

Example 4

Description of NODFA activity hydrogenation assay

120 ml (133.2 g) of 4-nitrosodiphenylamine sodium (NODFA) solution, 40 ml of toluene and weighed catalyst were metered into the autoclave. The autoclave was sealed and purged with hydrogen. The hydrogen was then adjusted to a pressure of 20 bar and the heating of the autoclave was switched on. After reaching a temperature of 75 ° C, the pressure was raised to 7 MPa and the autoclave stirring was switched on. This moment is considered to be the start of hydrogenation, t = 0. Electric heating and equipped with reaction heat set the temperature of the mixture

-2GB 298923 B6 increases rapidly and reaches a maximum value of about 100 ° C within a short time. The pressure in the autoclave was maintained at 5 to 7 MPa.

After 30 min. the hydrogenation is stopped by stirring, the autoclave is depressurized to 1.5 MPa and cooled with water for 15 min. After this time, the autoclave was depressurized, the reaction mixture was aspirated and filtered through filter paper (blue tape) into a separator. After filtration, the aqueous phase is separated from the mixture and analyzed spectrophotometrically to determine the conversion of 4-nitrosodiphenylamine (NODFA) to 4-aminodiphenylamine (ADFA).

Table 1

Comparison of individual catalysts by NODFA activity hydrogenation assay

Catalyst designation Fe content (%) conversion Example 1 0 69.8 Example 2 2,0 90.9 Example 3 3.0 86.2

Industrial use

The invention is useful in the chemical industry for the production of 4-aminodiphenylamine.

PATENT CLAIMS

Claims (4)

1. Catalyst for the hydrogenation of a solution of sodium salt of 4-nitrosodiphenylamine based on 1 to 5 wt. % palladium on activated carbon, characterized in that the catalyst contains 0.5 to 6 wt. iron, calculated on contained palladium. Catalyst according to claim 1, characterized in that at a palladium content of catalyst 2 30 to 5 wt. contains 2 to 4 wt. iron, calculated on contained palladium. A process for preparing a catalyst according to claim 1 or 2, characterized in that the aqueous suspension of activated carbon with the dissolved salts of Pd and Fe is treated with alkali metal carbonates or bicarbonates and precipitated with oxides Pd and Fe into activated carbon and subsequently reduced 35 a catalyst for the hydrogenation of a 4-nitrosodiphenylamine sodium salt solution. 4. A process according to claim 3, wherein the reduction of the Pd and Fe oxides is carried out with formaldehyde. A process for the preparation of a catalyst according to claim 3, characterized in that the reduction of oxides is carried out Pd and Fe are carried out with hydrazine. End of document