DE10216108A1 - Supported hydrogenating catalyst for hydrogenation of nitroaromatics to aminoaromatics, e.g. nitrobenzene to aniline, contains mixture of secondary precious metal and non-precious metal(s) - Google Patents

Abstract

Improving the selectivity and activity of the catalytic hydrogenation of nitroaromatics to aminoaromatics i.e. reducing the formation of by-products and increasing the yield of the desired product by selection and production of a hydrogenating catalyst. Supported hydrogenating catalyst in powder form contains, as catalytically active components, a mixture of primary precious metal, secondary precious metal and non-precious metal(s). Either platinum can be used as the primary precious metal with palladium (Pd), ruthenium (Ru), or rhodium (Rh) as the secondary precious metal, and vanadium (V), iron (Fe), manganese (Mn), cerium (Ce) and/or chromium (Cr) as the non-precious metal, or Pd can be used as the primary precious metal with Ru and Rh as the secondary precious metal and V, Fe, Mn, Ce and/or Cr as the non-precious metal or Pd can be used as the primary precious metal with Pt as the secondary precious metal and Ce and/or Cr as the non-precious metal. Independent claims are also included for: (1) process (P1) for the production of a hydrogenating catalyst; and (2) process (P2) for the production of aniline or toluenediamine.

Description

The invention relates to a powdered supported Hydrogenation catalyst, a process for its preparation and its use in the catalytic hydrogenation of Nitroaromatics.

The hydrogenation of aromatic nitro compounds to amines represents one of the main ways in industrial Chemistry for the production of amines. Aromatic amines are now central building blocks in the production of fine, Special and even large chemicals. Especially in Large chemicals are aniline and diaminotoluenes (TDA). Through the catalytic hydrogenation of Nitrobenzene to aniline was the old Bechamps reduction be replaced, making an important contribution to sustainable development could be achieved. TDA is as an intermediate in the manufacture of To look at polyurethane foams in one Phosgenation reaction to toluenediisocyanate (TDI) implemented which, together with polyalcohols Polyurethane foams are processed.

For the production of aromatic amines by hydrogenation of the are corresponding aromatic nitro compounds different processes and catalysts known. In addition to the gas phase hydrogenation of nitrobenzene to aniline There are a number of other procedures, all in the Work liquid phase. In addition to worn Non-precious metal catalysts and Raney catalysts There are also supported catalysts containing noble metals Use.

It is a range of catalytic catalysts Hydrogenation of nitro aromatics, especially of Dinitrotoluenes, known in the suspension phase.

US 2,823,235 describes palladium, platinum and palladium Platinum catalysts on soot that are doped with iron.

Very similar catalysts are described in US 3,127,356 described, which contain carbon black as a carrier.

In US 4,256,671 not only Pd and Pt but also Ni, Ru and Rh described as a precious metal component for catalysts that in the catalytic hydrogenation of dinitrotoluenes Diaminotoluenes are used.

US 6,096,924 describes as a catalytically active component Rh, Ru, Ir, Pt, Pd, Ni, Co. These metals are on powdered carriers applied. As a doping metal V is used.

DE 199 11 865 A1 describes Ir as noble metal and V as Doping metal a similar system.

While the mentioned publications Pd-, Ir- or Pd-Pt- Describe catalysts, US Pat. No. 4,212,824 describes a Pt Described catalyst on soot that is doped with Fe. Fe and V are by far the most common for doping base metals used.

It is also known that in supported Palladium catalysts the addition of a few mole percent Platinum (for example 15 mol%) a positive has a synergetic effect on the activity. This will be in pole. Chem. Stosow. 1981, 25 (I), 53-68 or in Chin. Chem. Lett. 1996, 7 (7), 663-664.

The first document shows that platinum in Relation to palladium only in a smaller molar amount may be present. The optimum is around 20 mol% Pt, based on Pd. If a larger amount of Pt is used, a lower activity is found.

The object of the present invention is by selection and producing a hydrogenation catalyst selectivity and activity of catalytic hydrogenation of To improve nitro aromatics to amino aromatics, d. H. the By-product formation decrease and yield to increase the desired product.

The invention relates to a powdered carrier Hydrogenation catalyst, which acts as a catalytically active component a mixture of a main noble metal component, one Precious metal secondary component and one or more Contains base metal components, either Pt as Main noble metal component and Pd, Ru, Rh as Precious metal secondary component and V, Fe, Mn, Ce and / or Cr as Base metal component or Pd as Main precious metal component and Ru, Rh as Precious metal secondary component and V, Fe, Mn, Ce and / or Cr as Base metal component or Pd as Main noble metal component and Pt as Precious metal secondary component and Ce and / or Cr as Base metal component can be used.

In the hydrogenation catalyst according to the invention, 100 g dry hydrogenation catalyst 10 to 50 mmol of Main noble metal component may be included. The share of Noble metal secondary component can 1 to 60 mol%, based on the main noble metal component, preferably between 8 and 12 mol%, based on the main noble metal component and 1-700 mol%, 100-600 mol% are preferred Base metal component, based on the Main precious metal component.

The by-product formation is determined by the ratio The main and secondary precious metal components are only minor influenced, the activity of the catalyst, however, strong.

Pt as the doping metals for the combination Main noble metal component and Pd, Ru, Rh as Precious metal secondary component V, Fe, Mn, Ce and / or Cr as Base metal component particularly well suited.

The doping metals for the combination are Pd Main precious metal component and Ru, Rh as Precious metal secondary component V, Fe, Mn, Ce and / or Cr as Base metal component particularly well suited.

The doping metal for the combination is Pd as Main noble metal component and Pt as Precious metal secondary component Ce and / or Cr as Base metal component particularly well suited.

While the precious metal secondary component for the high Activity of the catalyst is responsible Base metal component decisive for the selectivity responsible.

In the hydrogenation catalyst according to the invention can in 100 g dry hydrogenation catalyst 15 to 20 mmol of Main precious metal component, 8 to 12 mol% of Precious metal secondary component, based on the Main noble metal component, and 1 to 600 mol% cerium, based on the main noble metal component.

Powdered carriers are used as carriers, whereby physically activated these powdered carriers Activated carbon, chemically activated activated carbon, carbon black, Aluminum oxides or silicon oxides, preferably physically activated activated carbons, chemically activated activated carbons or can be soot.

Another object of the invention is a method for Preparation of the hydrogenation catalyst according to the invention, which is characterized in that to a suspension a powdery carrier material in water an aqueous Solution that the precious metal main that Precious metal secondary component and the base metal component contains in dissolved form, added by using a Base the precious metal main component, the precious metal secondary component and the base metal component on the powder Carrier material noticed and if necessary with a Reducing agents such as formaldehyde, hydrazine, Hydrogen, sodium borohydride, formic acid or Sodium formate, is reduced.

The reduction can take place at a temperature of 0 to 100 ° C be performed.

The order of putting the backing material together, Water, metal salt solutions and reducing agents can also can be varied. If necessary, the reduction can be done with Hydrogen take place on the dried catalyst. The Use of a reducing agent is optional, i. H. the Catalyst according to the invention can also after the precipitation Precious metal main, precious metal secondary and Base metal component on the carrier without adding a Reducing agent by filtration of the Reaction mixture are separated.

The catalyst of the invention can be used for the hydrogenation of Nitro aromatics are used. The invention Catalyst can be used in particular for the hydrogenation of Nitrobenzene to aniline and for the hydrogenation of Dinitrotoluenes are used to diamino toluenes.

The catalytic hydrogenation of the nitro compound can be carried out in Liquid phase as continuous or discontinuous Process operated at pressures between 1 and 100 bar and Temperatures between 0 and 250 ° C in the presence of the catalyst according to the invention are carried out.

The catalytic hydrogenation of the nitro compound in Liquid phase can be continuous or discontinuous Process operated at pressures between 1 and 100 bar and Temperatures between 0 ° C and 200 ° C in the presence of the catalyst according to the invention are carried out.

The catalytic hydrogenation of nitrobenzene or Dinitrotoluenes in the presence of the invention The catalyst can be discontinuous or continuous operated stirred reactor or in the continuously operated Circulation reactor in the presence of a solvent such as Example methanol or toluene. The solvent can also be a mixture of aniline and water in the case of Hydrogenation of nitrobenzene or a mixture of Dinitrotoluenes and water in the case of the hydrogenation of Be dinitrotoluenes.

The hydrogenation of dinitrotoluenes to diaminotoluenes can at temperatures between 70 and 200 ° C, preferably 90 and 150 ° C, and pressures between 1 and 100 bar, preferably 10 to 40 bar. Will the hydrogenation operated continuously, so the amount of implemented Dinitrotoluenes are replaced by subsequent dosing and the product Water mixture can be removed from the reactor.

When using the catalyst according to the invention a synergetic effect is observed, d. H. that by adding the precious metal secondary component the activity of Catalyst compared to the corresponding catalyst, that does not contain a second precious metal, increases sharply.

This was according to the state of the art Pol. Chem. Stosow. 1981, 25 (1), 53-68 or Chin. Chem. Lett. 1996, 7 (7), 663-664 not to be expected because describes that in the case of Pd at higher Pt Share of activity decreases.

It is therefore surprising that Pd as Precious metal secondary component at Pt as Precious metal main component a similar synergistic Effect shows.

For the other metal combinations there is in the Literature no evidence at all that this is special show high activity in nitro group hydrogenation should. On the contrary, one should have expected that the use of Rh or Ru as a precious metal secondary component has a negative effect as it is known (see on Example P.N. Rylander, Catalytic Hydrogenation in Organic Syntheses, Academic Press, 1979, New York, page 175 ff), that Rh and Ru are very well suited to aromatic rings hydrogenate and thus poor selectivity (i.e. undesirable side reactions) would have been expected. Surprisingly, this is not observed.

Examples

Catalysts and Comparative catalysts made and in terms of their catalytic properties in the hydrogenation of Nitro aromatics compared.

Comparative Example 1 Pd-containing trimetallic Soot catalyst

Production of a trimetal catalyst Pd-Pt-Fe / SB (1.6% Pd + 0.2% Pt + 4.0% Fe) with the Precious metal main component Pd, the precious metal secondary component Pt and the base metal component according to the prior art Technology. The Shawinigan Black product is used as a carbon black carrier from Chevron (in the catalyst as SB = Shawinigan Black abbreviated) used. The Pd-Pt-Fe / SB (1.6% Pd, 0.2% Pt, 4.0% Fe) catalyst is as in US 3,127,356, example VII manufactured described.

example 1 Trimetallic catalyst on soot

22.06 g Shawinigan Black carbon black (commercial product of Chevron, in the catalyst as SB = Shawinigan Black are abbreviated) in 2000 ml of deionized water suspended and the suspension with sodium carbonate solution adjusted to a pH of 10. Add to this suspension a solution of 2 g of tetrachloropalladium (II) acid (20%), 0.2 g hexachloroplatinic (IV) acid (25%) and 6.98 g Cerium (III) chloride heptahydrate in 200 ml deionized water. After heating to 80 ° C, the pH with Sodium carbonate solution adjusted to 6.4, stirred and filtered. 100 g dry catalyst contain 1.6% Pd, 0.2% Pt and 10.5% Ce. The catalyst is treated with Pd-Pt Ce / SB (1.6, 0.2, 10.5) abbreviated.

Comparative Example 2 Bimetallic catalyst on soot

The catalyst Pd-Pt / SB (1.6% Pd, 0.2% Pt) is as in Example 1 is prepared, but instead of the information given there 24.69 g Shawinigan Black and none Cerium salt used. Contain 100 g dry catalyst 1.6% Pd and 0.2% Pt.

Comparative Example 3 Pd-containing trimetal catalyst on activated carbon

98.21 g of activated carbon are dissolved in 500 ml of deionized water suspended and the suspension with sodium carbonate solution adjusted to a pH of 10. Add to this suspension 8 g of tetrachloropalladium (II) acid (20% strength), 0.8 g Hexachloroplatinic acid (25%) and 30.39 g Iron (III) nitrate nonahydrate, dissolved in 200 ml deionized Water. After heating to 80 ° C, the pH with Sodium carbonate solution adjusted to 6.4, stirred, with Reduced formaldehyde and filtered. 100 g drier Catalyst contain 1.6% Pd, 0.2% Pt and 4.2% Fe. The The catalyst is abbreviated to Pd-Pt-Fe / AK (1.6, 0.2, 4.2).

Example 2 Pd-containing trimetal catalysts on activated carbon

Activated carbon is suspended in 500 ml of deionized water and the suspension to pH with sodium carbonate solution set from 10. 8 g are added to this suspension Tetrachloropalladium (II) acid (20%), a solution of Precious metal secondary components and a salt of Base metal component, dissolved in 200 ml deionized Water. After heating to 80 ° C, the pH with Sodium carbonate solution adjusted to 6.4, stirred, with Reduced formaldehyde and filtered. The quantities are listed in Table 1.

Example 3 Pt-containing trimetal catalysts on activated carbon

Activated carbon is suspended in 500 ml of deionized water and the suspension is adjusted to a pH of 10 with sodium carbonate solution. 11.6 g of hexachloroplatinic acid (25%), a solution of the noble metal secondary components and a salt of the non-noble metal component, each dissolved in 200 ml of deionized water, are added to this suspension. After heating to 80 ° C., the pH is adjusted to 6.4 with sodium carbonate solution, stirred, reduced with formaldehyde and filtered. The quantities are listed in Table 2.

The catalysts according to the examples are in the discontinuous hydrogenation of dinitrotoluene Toluene diamine used and the activity and selectivity of the catalysts determined.

The reaction is carried out in a 0.5 liter Hastelloyautoclave carried out. First, the autoclave with 40 g of 2.4 Dinitrotoluene, 101 g 2,4-diaminotoluene, 59 g water and 1.2 g Catalyst (based on dry matter) charged. The Gas space is first closed with the autoclave Flushed with nitrogen, then with hydrogen and finally a pressure of 10 bar of hydrogen was given up.

After heating to 120 ° C, the reaction is complete Switch on the agitator started. The end point of the Reaction is the result of the rapid decline Hydrogen uptake can be precisely determined to zero.

During the reaction the hydrogen uptake recorded. After the reaction and cooling the reaction mixture taken up in methanol, filtered and examined by gas chromatography. This allows the Yield of TDA, sales of DNT and the amount By-product formation can be determined.

The following can be obtained as by-products: toluidine, Diaminobenzenes (referred to as low boilers) and tars. The term tars includes all compounds designated that have a longer retention time than that Main product have TDA.

The activity is calculated from the hydrogen uptake during the reaction time, based on the catalyst mass, and is given in ml H ₂ / (min g catalyst). The results are summarized in Table 3, Table 4 and Table 5.

Claims (10)

1. Powdered supported hydrogenation catalyst, which as catalytically active components a mixture of one Main precious metal component, one Precious metal secondary component and one or more Contains base metal components, either Pt as the main precious metal component and Pd, Ru, Rh as Precious metal secondary component and V, Fe, Mn, Ce and / or Cr as base metal component or Pd as Main precious metal component and Ru, Rh as Precious metal secondary component and V, Fe, Mn, Ce and / or Cr as base metal component or Pd as Main noble metal component and Pt as Precious metal secondary component and Ce and / or Cr as Base metal component can be used. 2. Powdered supported hydrogenation catalyst after Claim 1, characterized in that as powdered carrier physically activated Activated carbon, chemically activated activated carbon, carbon black, Aluminum oxides or silicon oxides can be used. 3. Hydrogenation catalyst according to claim 1, characterized characterized in that in 100 g of dry Hydrogenation catalyst 10-50 mmol of Noble metal main component, 1-60 mol% of Precious metal secondary component, based on the Main noble metal component, and 1-700 mol% of Base metal component, based on the Precious metal main component are included. 4. Hydrogenation catalyst according to claim 1, characterized characterized in that in 100 g of dry hydrogenation catalyst 15-20 mmol of the main noble metal component, 8-12 mol% of Precious metal secondary component, based on the Main noble metal component, and 1-600 mol% cerium, based on the main noble metal component. 5. Process for the preparation of a hydrogenation catalyst according to claims 1-4, characterized in that to a suspension of a powdered carrier material in water an aqueous solution that the Main precious metal component, the Precious metal secondary component and Contains non-precious metal component in dissolved form, added by using a base Precious metal main, the precious metal secondary component and Base metal component on the powdery Carrier material noticed and if necessary with a Reducing agent is reduced. 6. Use of the catalyst according to claims 1-4 for Hydrogenation of nitro aromatics to amino aromatics. 7. Use of the catalyst according to claims 1-4 for Hydrogenation of nitrobenzene to aniline. 8. Use of the catalyst according to claims 1-4 for Hydrogenation of dinitrotoluenes to toluenediamines. 9. Process for the preparation of aniline, thereby characterized in that the catalytic hydrogenation of the Corresponding nitro compound in the liquid phase as operated continuously or discontinuously Process at pressures between 1 and 100 bar and Temperatures between 0 ° C and 200 ° C in the presence of the Catalyst according to claims 1-4 is carried out. 10. A process for the preparation of toluenediamines, thereby characterized in that the catalytic hydrogenation of the Corresponding nitro compound in the liquid phase as operated continuously or discontinuously Process at pressures between 1 and 100 bar and Temperatures between 0 ° C and 200 ° C in the presence of the Catalyst according to claims 1-4 is carried out.