CATALYST SYSTEM FOR PRODUCING AROMATIC AMINES

Abstract

The invention relates to a catalyst system suitable for hydrogenating aromatic nitro compounds (I) to form the corresponding aromatic amines (II), the catalyst system containing, as essential constituents: a component A selected from the group consisting of silicon carbide, corundum (alpha-Al.sub.2O.sub.3) and slightly porous to non-porous zirconium oxide (ZrO.sub.2); and a component B, containing B1—a carrier substance selected from the group consisting of silicon dioxide, gamma-, delta- or theta-aluminum oxide Al.sub.2O.sub.3, titanium dioxide, zirconium dioxide and graphite, B2—a metal or a plurality of metals selected from the group consisting of copper, nickel, palladium, platinum and cobalt, and optionally B3—an additional metal selected from the group consisting of at least one metal selected from main group I, main group II, main group IV and sub-groups II, V, VI and VIII of the periodic table of the elements, the proportion of component A being in the range of 5 to 60 wt %, in relation to the total weight of the catalyst system, and the aromatic nitro compounds (I) being those of the general formula R—(NO.sub.2).sub.n, (I), and the aromatic amines (II) being those of the general formula R—(NH.sub.2).sub.n, (II), and the moieties R and indices n in formulas (I) and (II) having the following meaning: R is a substituted or unsubstituted aromatic C.sub.6-C.sub.10 moiety and n is an integer from 1 to 5.

Claims

1.-14. (canceled)

15. A catalyst system suitable for the hydrogenation of aromatic nitro compounds (I) to the corresponding aromatic amines (II), comprising as essential constituents a component A selected from the group consisting of silicon carbide, corundum (alpha-Al.sub.2O.sub.3) and low-porosity to non-porous zirconium oxide (ZrO.sub.2) and a component B comprising B1 a support material selected from the group consisting of silica, gamma-, delta- or theta-alumina Al.sub.2O.sub.3, titanium dioxide, zirconium dioxide, and graphite and B2 one or more metals selected from the group consisting of copper, nickel, palladium, platinum, and cobalt, and optionally B3 a further metal selected from the group consisting of at least one metal selected from main group I, main group II, main group IV, and subgroups II, V, VI, and VIII of the periodic table of the elements, wherein the proportion of component A is within a range from 5% to 60% by weight based on the total weight of the catalyst system and where the aromatic nitro compounds (I) are those of the general formula R—(NO.sub.2).sub.n (I), the aromatic amines (II) are those of the general formula R—(NH.sub.2).sub.n (II), and the radicals R and indices n in formulas (I) and (II) are defined as follows: R is a substituted or unsubstituted aromatic C.sub.6 to C.sub.10 radical and n is an integer from 1 to 5.

16. The catalyst system according to claim 15, wherein component A is a constituent of component B1.

17. The catalyst system according to claim 15, wherein component A comprises silicon carbide.

18. The catalyst system according to claim 15, wherein component A comprises exclusively silicon carbide.

19. The catalyst system according to claim 15, wherein component B2 comprises copper.

20. The catalyst system according to claim 15, wherein component B2 comprises exclusively copper.

21. The catalyst system according to claim 15, wherein component A comprises exclusively silicon carbide and component B2 comprises exclusively copper.

22. The catalyst system according to claim 15, wherein component A is a constituent of component B1, component A comprises exclusively silicon carbide, and component B2 comprises exclusively copper.

23. A process for producing a catalyst system as defined in claim 15, by i) producing a support material B1 comprising a component selected from the group consisting of silica, gamma-, delta- or theta-alumina Al.sub.2O.sub.3, titanium dioxide, zirconium dioxide, and graphite and contacting this support material with one or more metals B2 selected from the group consisting of copper, nickel, palladium, platinum, and cobalt, and optionally with B3 selected from the group consisting of at least one metal selected from main group I, main group II, main group IV, and subgroups II, V, VI, and VIII of the periodic table of the elements and combining this with a component A selected from the group consisting of silicon carbide, corundum (alpha-Al.sub.2O.sub.3) and low-porosity to non-porous zirconium oxide (ZrO.sub.2) or ii) producing a support material B1 comprising iia) a component selected from the group consisting of silica, gamma-, delta- or theta-alumina Al.sub.2O.sub.3, titanium dioxide, zirconium dioxide, and graphite and component A selected from the group consisting of silicon carbide, corundum (alpha-Al.sub.2O.sub.3) and low-porosity to non-porous zirconium oxide (ZrO.sub.2) and contacting this support material with one or more metals B2 selected from the group consisting of copper, nickel, palladium, platinum, and cobalt, and optionally with B3 selected from the group consisting of at least one metal selected from main group I, main group II, main group IV and subgroups II, V, VI, and VIII of the periodic table of the elements.

24. The catalyst system obtainable by the process according to claim 23.

25. A method comprising utilizing the catalyst system as defined in claim 15 for producing aromatic amines (II) through hydrogenation of aromatic nitro compounds (I).

26. A process for producing aromatic amines (II) through catalytic hydrogenation of the corresponding aromatic nitro compound (II), wherein a catalyst system as defined in claim 15 is used.

27. The process according to claim 26, wherein the process is executed in the fluidized bed.

28. The process according to claim 26, wherein the aromatic amine compound (II) is aniline and the corresponding aromatic nitro compound (I) is nitrobenzene.

Description

EXAMPLES

[0086] Silicon carbide is also referred to as SiC. Silica is also referred to as SiO.sub.2.

[0087] The parameters were determined as follows:

[0088] Particle size distribution measured by laser diffraction on a Malvern Mastersizer in accordance with ISO 13320.

[0089] Average particle diameter (d.sub.50 value) calculated from the particle size distribution (see above).

[0090] BET surface area in accordance with DIN 66131.

[0091] Pore volume (porosity) in accordance with DIN 66133.

[0092] k Value

[0093] The heat transfer in the form of the k value was measured for the catalyst system of the invention and for comparative catalysts as follows: One liter of catalyst is fluidized with nitrogen in a fluidized-bed reactor. A heating probe having a known surface area A is used to heat the fluidized catalyst to a defined temperature difference ΔT relative to the heating probe. The k value of the catalyst sample can then be determined via the electrical heating power P required.

[00001]$k=\frac{P}{A.Math.\Delta T}$

[0094] Abrasion

[0095] The Montecatini abrasion test simulates in a fluidized bed the mechanical load on a fluidized material, in this case the catalyst system of the invention. The abrasion apparatus consists of a nozzle plate having a nozzle diameter of 0.5 mm and with a gas- and solids-tight connection to a glass column element (diameter 30 mm). Connected to the upper part of the glass column element in a likewise gas- and solids-tight manner is a conically widening steel tube. The systems are connected to a 10 bar nitrogen supply. A pressure reducer is used to adjust the supply pressure to 6 barg for operation. The system is operated without overpressure under ambient conditions.

[0096] 60.0 g of the bulk material under investigation, in this case the catalyst system of the invention, was introduced into the apparatus. The gas volume flow for the fluidization was set to 350 l/h. The high gas velocities at the nozzle result in abrasion or breakage of the particles through particle-particle and particle-wall contacts. The discharged solids pass through a pipe bend into a filter paper sleeve. The discharged material is weighed after one hour and after a further five hours in order to determine the fines content (after 1 hour) and the abrasion (after 5 hours).

[0097] Expansion

[0098] A glass fluidized-bed apparatus (QVC standard tube 500 mm in length and 50 mm in diameter) is connected to a nitrogen supply (10 bar). The apparatus was filled with 200 g of particles and gas was passed into the product by opening a ball valve in the feed line. After thorough mixing of the particles (20-30 s), the ball valve was quickly closed. Once all gas bubbles have exited the particle layer, resulting in a bubble-free fluidized bed, the bed height is immediately noted. This corresponds to the height of an expanded fluidized bed without bubbles. The bed height thereafter continues to slowly sink due to further loss of gas until an end point is reached. This corresponds to the settled bed height, which is likewise noted. The expansion is defined as the ratio of the expanded bed height to the settled bed height.

Example 1

Production of Support Material B1 from SiC and SiO.SUB.2

[0099] A support material consisting of silicon carbide and silica was sprayed to a solid pulverulent product by spray-drying a 13.5% by weight aqueous suspension of 80% by weight of SiO.sub.2 (Hydrogel D11-20, BASF, milled to 10 μm) and 20% by weight of SiC (powder SC53232, Saint Gobain NorPro) with addition of 0.5% by weight of NaOH in a spray tower at a nozzle pressure of 1.8 bar. After sieving to remove the fines fraction, a mixed support having a BET specific surface area of 297 m.sup.2/g, an Hg pore volume of 1.16 ml/g, and a d.sub.50 value of 52 μm was obtained.

Example 2

Production of a Copper-Containing Catalyst System

[0100] 150 g of the pulverulent catalyst support 2016750030 (Saint Gobain NorPro, pore volume 0.69 ml/g) consisting of silicon carbide and silica in a mass ratio of 30:70 was placed in a rotary evaporator. 50 g of an ammoniacal solution of Cu (15% by weight CuO, density d=1.244 g/l) is added to the support at 120° C. and 480 mbar. A further 240.3 g of the Cu solution is added in six further impregnation steps. After each impregnation step, the material is dried for 1 h at 120° C. and 480 mbar and in the final two impregnation steps it was dried for 2 h at 120° C. and 300 mbar. The product was forced through a 250 μm sieve in order to break up agglomerates that had formed. The catalyst was then finally heated to 390° C. in a muffle furnace at 1 K/min and calcined at 390° C. for 2 h. The catalyst system had a CuO content of 22.2% by weight and comprised particles with an average particle diameter (d.sub.50 value) of 114 μm.

Example 3

Production of a Copper-Containing Catalyst System

[0101] 3.5 kg of the pulverulent catalyst support 2016750030 (Saint Gobain NorPro, pore volume 0.69 ml/g) consisting of silicon carbide and silica in a mass ratio of 30:70 was placed in a tumble dryer and heated to 80° C. An ammoniacal solution of Cu (14% by weight CuO, density d=1.205 g/l) was sprayed on in 6 portions of 1.14 kg each (total 6.87 kg), with the material dried in the rotary tumble dryer at 80° C. for 45 min between individual impregnation steps. The spray nozzles were rinsed clean with 100 ml of 25% NH.sub.3 solution. After all the impregnation solution had been added, the catalyst was dried at 80° C. for 5 h until the resulting pressure was <100 mbar. The catalyst was then finally heated to 550° C. in a muffle furnace at 1 K/min and calcined at 550° C. for 2 h. Data for the catalyst are shown in the table.

Example 4

Production of a Catalyst without SiC (Comparative)

[0102] A pulverulent SiO.sub.2 support (BV0308, BASF) was impregnated with ammoniacal Cu solution, dried, and finally calcined in analogous manner to example 2. The catalyst had a CuO content of 21.2% by weight and comprised particles with an average particle diameter (d.sub.50 value) of 112 μm.

Example 5

Production of a Further Catalyst without SiC (Comparative)

[0103] A pulverulent SiO.sub.2 support (BV0308, BASF) was impregnated with ammoniacal Cu solution, dried, and finally calcined in analogous manner to example 3. Data for the catalyst are shown in the table.

Example 6

Aniline Production

[0104] The behavior of the Cu-containing catalyst system comprising an SiC—SiO.sub.2 support produced in example 3 and also the behavior of a noninventive catalyst from example 5 were examined in continuous operation as follows: Preheated nitrobenzene was pumped by means of a two-phase nozzle into a 5 l fluidized-bed reactor, where it was fluidized at the nozzle opening with part of the hydrogen flow. The reaction was carried out at a temperature of 290° C., a pressure of 5 bar (6 bar absolute) with 2 Nm.sup.3/h hydrogen and 8 Nm.sup.3/h nitrogen and 1.2 kg of nitrobenzene/hour.

[0105] Using 2.2 kg of the catalyst system from example 3, a conversion of 100% and an aniline selectivity of 99.7% were achieved. The catalyst could be completely regenerated through intermediate regeneration with an air/nitrogen mixture at 220-290° C. and showed conversion of 100% and an aniline selectivity of 99.7% in the 2nd to 6th cycles too. The experiment was then ended, although the catalyst remained active. No coating with copper was observed in the deinstalled catalyst.

[0106] The results are compiled in the table below.

TABLE-US-00001 TABLE Aniline production Catalyst Comparative system of the catalyst invention from system from Parameter example 3 example 5 Support 30% SiC 100% 70% SiO.sub.2 SiO.sub.2 Composition % by 56/24/20 79/0/21 SiO.sub.2/SiC/CuO weight d50 μm 118 112 Pore volume ml/g 0.92 1.18 BET surface area m.sup.2/g 166 179 Abrasion % by 2.3 8.6 weight Density kg/l 2.37 2.18 Bulk density kg/l 0.70 0.56 Expansion % 4.3 4.5 k value W/m.sup.2K 478 406 Conversion of % 100 100 nitrobenzene Selectivity for % 99.7 99.7 aniline

[0107] The parameters listed in the table were determined as described above.

[0108] It was surprisingly found that an SiC-containing SiO.sub.2 support can still be readily doped with Cu in the region of 20% by weight, even though the modification of the support means that less pore volume is available for impregnation. This was surprisingly not accompanied by an adverse effect on the conversion behavior and selectivity of the catalyst system of the invention. The catalyst system of the invention based on SiC-containing SiO.sub.2 powder surprisingly achieved a disproportionately high BET surface area. The heat transfer behavior of the catalyst system of the invention (k value) is far superior to that of the comparative catalyst.