Combined nitro compound hydrogenation and catalyst regeneration process; process for catalyst activation; catalysts obtained by these processes and their use in nitro compound hydrogenation; reaction system

Abstract

The present invention relates in a first aspect to a process for regenerating an at least partially spent hydrogenation catalyst comprising:(a) providing a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2(1) in the range of from 0.001 to 3 g per liter of liquid aqueous mixture; and (b) maintaining a concentration CH2(2) of hydrogen (H2) in the range of from 0.001 to 3 g per liter of liquid aqueous mixture in the liquid aqueous mixture, thereby obtaining an at least partially regenerated hydrogenation catalyst. In a second aspect, the invention relates to a method for activating a fresh hydrogenation catalyst, comprising (A) providing a liquid aqueous mixture comprising a fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group; and (B) applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A); thereby obtaining an activated hydrogenation catalyst. The invention is directed in a third aspect to a combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst. In a fourth aspect, the invention is related to an at least partially regenerated hydrogenation catalyst as well as in a fifth aspect to an activated hydrogenation catalyst. A sixth aspect of the invention is directed to the use of the at least partially regenerated and / or activated hydrogenation catalyst as a hydrogenation catalyst. A seventh aspect of the invention is related to a reaction system for combined hydrogenation of a compound having at least one nitro group and regeneration of an at least partially spent hydrogenation catalyst.

Description

[0001] Process for regenerating an at least partially spent hydrogenation catalyst

[0002] The present invention relates in a first aspect to a process for regenerating an at least partially spent hydrogenation catalyst comprising: (a) providing a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2 in the range of from 0.001 to 3 g per liter of liquid aqueous mixture; and (b) maintaining a concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture in the range of from 0.001 to 3 g per liter of liquid aqueous mixture, thereby obtaining an at least partially regenerated hydrogenation catalyst.

[0003] In a second aspect, the invention relates to a method for activating a fresh hydrogenation catalyst, comprising (A) providing a liquid aqueous mixture comprising a fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group; and (B) applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A); thereby obtaining an activated hydrogenation catalyst. The invention is directed in a third aspect to a combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst. In a fourth aspect, the invention is related to an at least partially regenerated hydrogenation catalyst as well as in a fifth aspect to an activated hydrogenation catalyst. A sixth aspect of the invention is directed to the use of the at least partially regenerated and / or activated hydrogenation catalyst as a hydrogenation catalyst. A seventh aspect of the invention is related to a reaction system for combined hydrogenation of a compound having at least one nitro group and regeneration of an at least partially spent hydrogenation catalyst.

[0004] State of the art

[0005] The hydrogenation of aromatic nitro compounds to their amino analogs is of great importance for the production of fine chemicals and pharmaceuticals. A range of highly active and yet selective catalysts exits, wherein one common drawback is the deactivation of the catalyst during the hydrogenation reaction. Several attempts, aside from simply adding fresh catalyst over the course of the reaction are known, to compensate this drawback.

[0006] EP 2 686 294 B1 discloses a catalyzed process for hydrogenation of a nitroaromatic compound in liquid phase, which is focused on a submixing of the nitroaromatic compounds in the liquid phase as fast as possible so that local over-concentrations which favor catalyst deactivation are to be avoided. EP 2 838 875 B1 discloses a process for regeneration of a hydrogenation catalyst, wherein the hydrogenation catalyst is heated and contacted with oxygen. EP 2 598 241 B1 also describes a process for regenerating the activity of a used hydrogenation catalyst, in which a regeneration comprises at periodic intervals at least a first burn-off stage in the presence of oxygen, a washing stage with water, a second burn-off stage in the presence of oxygen and a second washing stage with water.

[0007] However, these regeneration processes are laborious and always require a separation of the hydrogenation catalyst and the hydrogenation solution and also require at least a contacting with oxygen. Thus, there is a need for simpler regeneration processes, which also allow avoidance of the use of oxygen.

[0008] In a first aspect, the present invention relates to a process for regenerating an at least partially spent hydrogenation catalyst comprising:

[0009] (a) providing a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2(1 ) in the range of from 0.001 to 3 g per liter of liquid aqueous mixture;

[0010] (b) maintaining a concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture in the range of from 0.001 to 3 g per liter of liquid aqueous mixture, thereby obtaining an at least partially regenerated hydrogenation catalyst.

[0011] It could be seen that the inventive regeneration process after its conduction enabled the catalyst to carry out the hydrogenation of compound comprising at least one nitro group in an efficient manner for a significantly longer time span compared to a process without regeneration. Furthermore, it could be seen that the catalyst’s consumption was improved since per gram catalyst a higher amount of compound comprising at least one nitro group could be converted into its amino analogue compared to a process without regeneration. The liquid aqueous mixture provided according to (a) can be the same as used for hydrogenation of a compound comprising at least one nitro group, wherein only the content of the compound comprising at least one nitro group is kept below 5000 weight-ppm, for example, by not introducing further compound comprising at least one nitro group into the liquid aqueous mixture after the remaining compound comprising at least one nitro group has been consumed in hydrogenation. Consequently, no laborious steps such as emptying a reaction zone, no application of oxygen and no extensive washing step(s) are required for the inventive regeneration process.

[0012] In some embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the precise value of CH2(1 ) is not equal to the precise value ofCH2(2) but both precise values are in the same range of from 0.001 to 3 g per liter of liquid aqueous mixture. In some embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the precise value of CH2(1 ) is equal to the precise value ofCH2(2) and both precise values are in the same range of from 0.001 to 3 g per liter of liquid aqueous mixture.

[0013] The liquid aqueous mixture having a concentration CH2(1 ) of H2 is preferably provided within a reaction zone and also the maintaining of the concentration CH2(2) is preferably at least done within said reaction zone, wherein the “reaction zone” comprises a “regeneration zone” and / or a “hydrogenation zone”, wherein, if “regeneration zone” and “hydrogenation zone” are present, these two are preferably spacely separated from each other, more preferably the regeneration zone is a regeneration reactor and the hydrogenation zone is a hydrogenation reactor, preferably as described in more detail below.

[0014] The compound having at least one nitro group, which is present in the liquid aqueous mixture provided in (a) in less than 5000 weight-ppm is preferably an aromatic compound having at least one nitro group, more preferably an aromatic compound having one or two nitro groups, more preferably selected from the group consisting of 2,3-dinitrotoluene (2,3-DNT), 2,4-dinitro- toluene (2,4-DNT), 2,5-dinitroluene (2,5-DNT), 2,6-dinitrotoluene (2,6-DNT), 3,4-dinitrotoluene (3,4-DNT), 3,5-dinitrotoluene (3,5-DNT), 2-amino-3-nitrotoluene (2,3-ANT), 3-amino-2-nitrotolu- ene (3,2-ANT), 2-amino-4-nitrotoluene (2,4-ANT), 4-amino-2-nitrotoluene (4,2-ANT), 4-amino-3- nitrotoluene (4,3-ANT), 3-amino-4-nitrotoluene (3,4-ANT), 2-amino-5-nitrotoluene (2,5-ANT), 5- amino-2-nitrotoluene (5,2-ANT), 3-amino-5-nitrotoluene (3,5-ANT), 2-amino-6-nitrotoluene (2,6- ANT), and mixtures of two or more thereof. More preferably, the liquid aqueous mixture comprises less than 2000 weight-ppm of a compound comprising at least one nitro group and at least one amino group and less than 50 weight-ppm of a compound comprising at least one nitro group and comprising no amino group.

[0015] Spent versus regenerated hydrogenation catalyst

[0016] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially spent hydrogenation catalyst (she) of (a) has an overall surface area of <1200 m2 / g, more preferably <800 m2 / g, more preferably <500 m2 / g, more preferably <250 m2 / g, more preferably <200 m2 / g, more preferably <120 m2 / g, more preferably <60 m2 / g, more preferably <40 m2 / g determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131.

[0017] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially regenerated hydrogenation catalyst (rhe) has an overall surface area <1200 m2 / g m2 / g, more preferably <800 m2 / g m2 / g, more preferably <500 m2 / g m2 / g, more preferably <250 m2 / g, more preferably <200 m2 / g, more preferably <120 m2 / g, more preferably <60 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131.

[0018] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially spent hydrogenation catalyst (she) of (a) has a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of <95, preferably <96, more preferably <97, more preferably < 98 %, based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, the at least partially regenerated hydrogenation catalyst (rhe) obtained in (b) has a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant or intermediate) of in the range of from 98 to 100 %, based on 100 % being the maximum normalized H2 consumption.

[0019] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially spent hydrogenation catalyst (she) of (a) comprises in the range of from 0 to less than 25 weight-% of carbon and in the range of from 0 to less than 6 weight-% of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially spent hydrogenation catalyst being 100 weight-%; and / or, preferably and, the at least partially regenerated hydrogenation catalyst (rhe) of (b) comprises in the range of from 0 to less than 25 weight-%, preferably in the range of from 0 to less than 10 weight-%, more preferably in the range of from 0 to less than 5 weight-%, of carbon and in the range of from 0 to less than 6 weight-%, preferably in the range of from 0 to less than 3 weight-%, more preferably in the range of from 0 to less than 1 weight-%, of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially spent hydrogenation catalyst being 100 weight-%. It is noted that the content of carbon and / or nitrogen is only related to the at least partially spent or the at least partially regenerated hydrogenation catalyst, not to any support material, which might be comprises in a catalytic material.

[0020] Catalyst taken from the hydrogenation zone and / or regeneration zone is preferably washed, more preferably by mixing with solvent, more preferably with a high excess of solvent, for example, at a volume based ratio catalyst: solvent of > 1 :10, wherein the solvent is preferably selected from the group consisting of ethanol, isopropanol, acetone, aniline and mixtures of two or more thereof. The mixture is then preferably filtered and washed, preferably under an ambient atmosphere, with solvent, again preferably with a high excess of solvent, more preferably with a volume based ratio catalyst: solvent of> 1 :10, wherein the solvent is preferably selected from the group consisting of ethanol, isopropanol, acetone, aniline and mixtures of two or more thereof. Subsequently, the catalyst is dried under ambient atmosphere, preferably at a temperature in the range of from 20 to 25 °C and / or in a drying oven at 50°C and / or in a vacuum drying oven at 120°C. The resulting washed and dried catalyst is then submitted for further analysis (e.g. EA, BET, Hg porosimetry and XRD).

[0021] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially spent hydrogenation catalyst (she) of (a) has a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably of <1.4ml / g, more preferably <1.0 ml / g, more preferably <0.8 ml / g, more preferably <0.6 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter of <800 nm, preferably <250 nm, more preferably <150 nm, more preferably <100 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0022] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially regenerated hydrogenation catalyst (rhe) of (b) has a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1 .8 ml / g, more preferably of <1.4ml / g, more preferably <1.0 ml / g, more preferably <0.8 ml / g, more preferably <0.6 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter of <800 nm, preferably <250 nm, more preferably <150 nm, more preferably <100 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0023] Liquid mixture provided in (a)

[0024] The liquid aqueous mixture provided in (a) comprises preferably less than 2500 weight-ppm, preferably less than 2100 weight-ppm, of a compound comprising at least one nitro group.

[0025] The compound having at least one nitro group, which is present in the liquid aqueous mixture provided in (a) in less than 5000 weight-ppm is, as indicated above, preferably an aromatic compound having at least one nitro group, more preferably an aromatic compound having one or two nitro groups, more preferably selected from the group consisting of 2,3-dinitrotoluene (2,3-DNT), 2,4-dinitrotoluene (2,4-DNT), 2,5-dinitroluene (2,5-DNT), 2,6-dinitrotoluene (2,6- DNT), 3,4-dinitrotoluene (3,4-DNT), 3,5-dinitrotoluene (3,5-DNT), 2-amino-3-nitrotoluene (2,3- ANT), 3-amino-2-nitrotoluene (3,2-ANT), 2-amino-4-nitrotoluene (2,4-ANT), 4-amino-2-nitrotolu- ene (4,2-ANT), 4-amino-3-nitrotoluene (4,3-ANT), 3-amino-4-nitrotoluene (3,4-ANT), 2-amino-5- nitrotoluene (2,5-ANT), 5-amino-2-nitrotoluene (5,2-ANT), 3-amino-5-nitrotoluene (3,5-ANT), 2- amino-6-nitrotoluene (2,6-ANT) and mixtures of two or more thereof. More preferably, the liquid aqueous mixture comprises less than 2000 weight-ppm of a compound comprising at least one nitro group and at least one amino group and less than 100 weight-ppm, preferably less than 30 weight-ppm, of a compound comprising at least one nitro group and comprising no amino group. More preferably, the liquid aqueous mixture comprises less than 2000 weight-ppm of ANT and less than 100 weight-ppm, preferably less than 30 weight-ppm, of DNT, wherein preferably, less than 1 weight-ppm of any further compound having at least one nitro group are present in the liquid mixture.

[0026] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the liquid aqueous mixture provided in (a) comprises in the range of from 20 to 90 weight-%, preferably in the range of from 30 to 85 weight-%, more preferably in the range of from 40 to 80 weight-%, more preferably in the range of from 50 to 70 weight-% of a compound comprising at least one amino group, which does not comprise a nitro group, based on the total weight of the liquid aqueous mixture being 100 weight-%.

[0027] The compound having at least one nitro group and the compound having at least one amino group, which does not comprise a nitro group, are preferably reactant and product of a hydrogenation reaction, preferably of the same hydrogenation reaction. As indicated above, the compound having at least one nitro group is preferably selected from the group consisting of 2,3-di- nitrotoluene (2,3-DNT), 2,4-dinitrotoluene (2,4-DNT), 2,5-dinitroluene (2,5-DNT), 2,6-dinitrotolu- ene (2,6-DNT), 3,4-dinitrotoluene (3,4-DNT), 3,5-dinitrotoluene (3,5-DNT), 2-amino-3-nitrotolu- ene (2,3-ANT), 3-amino-2-nitrotoluene (3,2-ANT), 2-amino-4-nitrotoluene (2,4-ANT), 4-amino-2- nitrotoluene (4,2-ANT), 4-amino-3-nitrotoluene (4,3-ANT), 3-amino-4-nitrotoluene (3,4-ANT), 2- amino-5-nitrotoluene (2,5-ANT), 5-amino-2-nitrotoluene (5,2-ANT), 3-amino-5-nitrotoluene (3,5- ANT), 2-amino-6-nitrotoluene (2,6-ANT) and mixtures of two or more thereof. As initial reactant of a hydrogenation reaction, preferably, a compound comprising at least one nitro group, which does not comprise an amino group, is used more preferably selected from the group consisting of 2,3-dinitrotoluene (2,3-DNT), 2,4-dinitrotoluene (2,4-DNT), 2,5-dinitroluene (2,5-DNT), 2,6- dinitrotoluene (2,6-DNT), 3,4-dinitrotoluene (3,4-DNT), 3,5-dinitrotoluene (3,5-DNT). The compound having at least one amino group, which is the final product of a hydrogenation reaction, is also a compound having no nitro group. More preferably the hydrogenation reaction is the hydrogenation of a compound having two nitro groups, wherein said two nitro groups are converted each into an amino group, thereby obtaining a compound having two amino groups, which does not have a nitro group, preferably the compound having two amino groups and no nitro groups is selected from the group consisting of 2,3-diaminotoluene (2,3-TDA), 2,4-dia- minotoluene (2,4-TDA), 2,5-diaminoluene (2,5-TDA), 2,6-diaminotoluene (2,6-TDA), 3,4-dia- minotoluene (3,4-TDA), 3,5-diaminotoluene (3,5-TDA), and mixtures of two or more thereof. Intermediate compounds in this preferred hydrogenation reaction are compounds still having one nitro group but already having one amino group, such as 2-amino-3-nitrotoluene (2,3-ANT), 3- amino-2-nitrotoluene (3,2-ANT), 2-amino-4-nitrotoluene (2,4-ANT), 4-amino-2-nitrotoluene (4,2- ANT), 4-amino-3-nitrotoluene (4,3-ANT), 3-amino-4-nitrotoluene (3,4-ANT), 2-amino-5-nitrotolu- ene (2,5-ANT), 5-amino-2-nitrotoluene (5,2-ANT), 3-amino-5-nitrotoluene (3,5-ANT), 2-amino-6- nitrotoluene (2,6-ANT) and mixtures of two or more thereof.

[0028] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, in the range of from 95 to 100 weight-%, preferably in the range of from 98 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.5 to 100 weight-%, of the liquid aqueous mixture provided in (a) consist of hydrogen, the at least partially spent hydrogenation catalyst, water and compound comprising at least one amino group, based on the total weight of the liquid aqueous mixture being 100 weight-%.

[0029] In some preferred embodiments, the liquid aqueous mixture provided in (a) additionally comprises one or more C1 to C6 mono alcohol, preferably a C1 to C6 mono alcohol from the group consisting of C1 to C5 mono alcohols, more preferably selected from the group consisting of methanol, ethanol, propanol, including n-propanol and iso-propanol, and mixtures of two or three thereof, more preferably at least iso-propanol. In these preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, in the range of from 95 to 100 weight-%, preferably in the range of from 98 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.5 to 100 weight-%, of the liquid aqueous mixture provided in (a) consist of hydrogen, the at least partially spent hydrogenation catalyst, water, compound comprising at least one amino group and one or more C1 to C6 mono alcohol, based on the total weight of the liquid aqueous mixture being 100 weight-%. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the liquid aqueous mixture comprising H2 with CH2(1 ) is provided in (a) within a reaction zone; wherein a hydrogen containing gas is applied onto the liquid aqueous mixture in said reaction zone at a pressure p in the range of from 0.1 to 200 bar, preferably in the range of from 0.1 to 100 bar, more preferably in the range of from 0.1 to 50 bar, more preferably in the range of from 15 to 40 bar, more preferably in the range of from 20 to 30 bar. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the liquid aqueous mixture comprising H2 with CH2(1 ) is provided in (a) with a temperature T in a reaction zone in the range of from 50 to 200 °C, preferably in the range of from 60 to 180 °C, more preferably in the range of from 70 to 150 °C.

[0030] Maintaining H2 concentration CH2(2) in (b) In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the liquid aqueous mixture comprising H2 with CH2(1 ) is provided in (a) within a reaction zone; and in (b), maintaining the H2 concentration CH2(2) is done by applying hydrogen containing gas onto the liquid aqueous mixture in said reaction zone at a pressure p in the range of from 0.1 to 200 bar, preferably in the range of from 0.1 to 100 bar, more preferably in the range of from 0.1 to 50 bar, more preferably in the range of from 15 to 40 bar, more preferably in the range of from 20 to 30 bar.

[0031] As indicated above, the “reaction zone” comprises a “regeneration zone” and / or a “hydrogenation zone”, wherein, if “regeneration zone” and “hydrogenation zone” are present, these two are in some embodiments spacely separated from each other, preferably the regeneration zone is a regeneration reactor and the hydrogenation zone is a hydrogenation reactor, preferably as described in more detail below. The difference between a hydrogenation zone and a regeneration zone is mainly the concentration of the compound having at least one nitro group: In a regeneration zone, the compound having at least one nitro group is present in the liquid aqueous mixture in less than 5000 weight-ppm whereas in a hydrogenation zone, said compound is present in the respective liquid aqueous mixture in an amount exceeding 5000 weight-ppm, provided that enough H2 is present, i.e. the liquid aqueous mixture is saturated with H2. Thus, the regeneration zone can also be the hydrogenation reactor if, even if enough H2 is present, the compound having at least one nitro group is present in the liquid aqueous mixture in less than 5000 weight-ppm. Furthermore, regeneration happens in said mixture regardless of its location as long as the compound having at least one nitro group is present in the liquid aqueous mixture in less than 5000 weight-ppm and enough H2 is present. Thus, the regeneration may also take place in plant components fluidically connected to the reaction zone downstream therefrom. For example, the regeneration may also occur within a subsequent zone downstream from the reaction zone, such as a separation zone (such as a settler), used for separating heterogeneous hydrogenation catalyst from the liquid aqueous mixture.

[0032] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the hydrogen containing gas comprises at least 90 volume-%, more preferably in the range of from 90 to 100 volume-%, of hydrogen, based on the total volume of the hydrogen containing gas being 100 volume-%.

[0033] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the hydrogen containing gas comprises at least less than 0.1 volume-% of carbon monoxide, more preferably less than 0.1 volume-% of carbon monoxide and less than 0.1 volume-% of oxygen, based on the total volume of the hydrogen containing gas being 100 volume-%. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, maintaining the H2 concentration CH2(2) in (b) is done at a temperature T in a reaction zone in the range of from 50 to 200 °C, preferably in the range of from 60 to 180 °C, more preferably in the range of from 70 to 150 °C.

[0034] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) in the reaction zone is maintained with simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm.

[0035] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, maintaining the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) and simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm in the reaction zone is done for at least 10 seconds, preferably at least 20 seconds, more preferably at least 30 seconds.

[0036] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, maintaining the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) and simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm in the reaction zone is done for at least 1 minute, preferably for at least 5 minutes, more preferably for at least 10 minutes, more preferably for at least 15 minutes, more preferably for at least 20 minutes, more preferably for at least 25 minutes, more preferably for at least 30 minutes; and / or is done for at the outmost 170 hours, preferably for at the outmost 160 hours, more preferably for at the outmost 150 hours, more preferably for at the outmost 120 hours, more preferably for at the outmost 110 hours, more preferably for at the outmost 100 hours, more preferably for at the outmost 90 hours, more preferably for at the outmost 80 hours.

[0037] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, maintaining the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) and simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm in the reaction zone is done for a period of time of in the range of from 1 minute to 170 hours, preferably in the range of from 1 minutes to 160 hours, more preferably in the range of from 1 minutes to 150 hours, more preferably in the range of from 1 minutes to 140 hours, more preferably in the range of from 1 minutes to 130 hours, more preferably in the range of from 1 minutes to 120 hours, more preferably in the range of from 1 minute to 110 hours, more preferably in the range of from 1 minute to 100 hours, more preferably in the range of from 1 minute to 100 hours, more preferably in the range of from 1 minute to 90 hours, more preferably in the range of from 1 minute to 80 hours.

[0038] Thus, the at least partially spent hydrogenation catalyst is kept for the above-identified minimum and / or maximum period of time, preferably for a period of time as indicated above, in a hydrogen containing environment in the reaction zone, wherein the concentration of the compound comprising at least one nitro group is < 5000 weight-ppm.

[0039] CH2(1), CH2(2)

[0040] In some preferred embodiments, CH2(1 ) and CH2(2) are both in the range of from 0.001 to 3 g per liter of liquid aqueous mixture, especially if the temperature in the reaction zone is in the range of from 50 to 200 °C and / or, preferably and, if the pressure of hydrogen containing gas is in the range of from 0.1 to 200 bar. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, preferably in the range of from 95 to 100 weight- %, preferably in the range of from 98 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.5 to 100 weight-%, of the liquid aqueous mixture provided in (a) consist of hydrogen, the at least partially spent hydrogenation catalyst, water and compound comprising at least one amino group, based on the total weight of the liquid aqueous mixture being 100 weight-%. In these embodiments, wherein the temperature in the reaction zone is in the range of from 50 to 200 °C, preferably the pressure of hydrogen containing gas in a) and b) is in the range of from 0.1 to 200 bar and CH2(1 ) and CH2(2) are both in the range of from 0.001 to 1 g per liter of liquid aqueous mixture, more preferably the pressure of hydrogen containing gas in a) and b) is in the range of from 0.1 to 100 bar and CH2(1 ) and CH2(2) are both in the range of from 0.001 to 0.5 g per liter of liquid aqueous mixture, more preferably the pressure of hydrogen containing gas in a) and b) is in the range of from 0.1 to 50 bar and CH2(1 ) and CH2(2) are both in the range of from 0.001 to 0.25 g per liter of liquid aqueous mixture.

[0041] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, in the range of from 95 to 100 weight-%, preferably in the range of from 98 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.5 to 100 weight-%, of the liquid aqueous mixture provided in (a) consist of hydrogen, the at least partially spent hydrogenation catalyst, water, compound comprising at least one amino group and one or more C1 to C6 mono alcohol, based on the total weight of the liquid aqueous mixture being 100 weight-%. In these embodiments, wherein the temperature in the reaction zone is in the range of from 50 to 200 °C, preferably the pressure of hydrogen containing gas in a) and b) is in the range of from 0.1 to 200 bar and CH2(1 ) and CH2(2) are both in the range of from 0.001 to 3 g per liter of liquid aqueous mixture, more preferably the pressure of hydrogen containing gas in a) and b) is in the range of from 0.1 to 100 bar and CH2(1 ) and CH2(2) are both in the range of from 0.001 to 1.5 g per liter of liquid aqueous mixture, more preferably the pressure of hydrogen containing gas in a) and b) is in the range of from 0.1 to 50 bar and CH2(1 ) and CH2(2) are both in the range of from 0.001 to 0.75 g per liter of liquid aqueous mixture.

[0042] Compound having at least one nitro group & compound having at least one amino group and no nitro group

[0043] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the compound having at least one nitro group is a reactant of a hydrogenation reaction and comprises preferably at least a compound selected from the group consisting of 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2-amino-4-nitrotoluene, 2-amino-6-nitrotoluene and mixtures of two or more thereof and / or the compound having at least one amino group, which does not comprise a nitro group, is a product of a hydrogenation reaction and comprises preferably at least a compound selected from the group consisting of 2,4-diaminotoluene, 2,6- diaminotoluene and a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene.

[0044] Catalyst material

[0045] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the hydrogenation catalyst comprises at least one first metal of the I., II., V., VI. and / or VIII. subgroup of the periodic table of elements, more preferably at least one metal of the I. and / or VIII. subgroup of the periodic table of the elements, more preferably at least one metal selected from the group consisting of nickel, platinum and palladium, optionally in combination with at least one second metal of the I., II., IV., V., VI. and / or VIII. subgroup of the periodic table of the elements, wherein the second metal is different from the first metal.

[0046] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the hydrogenation catalyst comprises nickel, preferably nickel having an oxidation state 0, +1, +2, +3 and / or +4, wherein the hydrogenation catalyst more preferably comprises in the range of from 0.1 to 99% by weight, preferably in the range of from 1 to 90% by weight, more preferably in the range of from 25 to 85% by weight, more preferably in the range of from 60 and 80 % by weight, of Ni(0) and / or one or more nickel containing compounds, wherein the nickel has an oxidation state 0, +1 , +2, +3 and / or +4, based on the total weight of the hydrogenation catalyst being 100 weight-%. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the second metal of the I., II., IV., V., VI. and / or VIII. subgroup of the Periodic Table is selected from the group consisting of palladium, platinum, rhodium, iron, cobalt, zinc, chromium, vanadium, copper, silver, zirconium, titanium, hafnium, and mixtures of two or more thereof.

[0047] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the second metal of the I., II., IV., V., VI. and / or VIII. subgroup of the Periodic Table is selected from the group consisting of palladium, platinum, rhodium, iron, cobalt, zinc, chromium, vanadium, copper, silver, zirconium, titanium, hafnium, nickel, rhenium, ruthenium, and mixtures of two or more thereof.

[0048] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the hydrogenation catalyst comprises a support which is preferably selected from the group consisting of activated carbon, carbon black, graphite, oxidic carrier component and mixtures of two or more thereof, wherein the oxidic carrier component is preferably selected from the group consisting of silicon dioxide, silicon carbide, kieselguhr, aluminum oxide, magnesium oxide, titanium dioxide, zirconium dioxide, hafnium dioxide and mixtures of two or more thereof, more preferably the oxidic carrier compound is selected from the group consisting of zirconium dioxide, silicon dioxide, hafnium dioxide and mixtures of two or more thereof, more preferably the oxidic carrier component comprises, more preferably is, zirconium dioxide and / or silicon dioxide.

[0049] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the at least partially spent hydrogenation catalyst (she) comprises at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 80-100 : 0-20, determined by XRD; and / or, preferably and, the at least partially regenerated hydrogenation catalyst (rhe) comprises at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD.

[0050] The support used is preferably mesoporous and has an average pore diameter in the range of from 35 to 50 nm and a specific BET surface area in the range of from 50 to 250 m2 / g. The surface of the support is determined by the BET method by N2 adsorption, in particular according to DIN 66131. The average pore diameter, and the average pore volume are determined by Hg porosimetry, in particular according to DIN 66133. The catalytic material, which comprises the hydrogenation catalyst and optionally the support, can be present in any conceivable form. It is preferred that the catalytic material is in the form of a molding.

[0051] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the liquid aqueous mixture provided in (a) comprises the hydrogenation catalyst in suspended form and / or in slurry form.

[0052] Addition of fresh catalyst & activation

[0053] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, (a) comprises

[0054] (a.1) providing a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2(1 ) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture;

[0055] (a.2) adding fresh hydrogenation catalyst to the mixture provided in (a.1), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, wherein the liquid aqueous mixture comprises dissolved hydrogen (H2) at a concentration CH2(1 ).

[0056] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, (b) is

[0057] (b’) maintaining a concentration CH2(2) of hydrogen (H2) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture in the liquid aqueous mixture provided in (a.2); thereby obtaining a mixture comprising at least partially regenerated hydrogenation catalyst and activated fresh catalyst.

[0058] Fresh hydrogenation catalyst

[0059] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the fresh hydrogenation catalyst has an overall surface area in the range of from 1 to 1200 m2 / g, more preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the fresh hydrogenation catalyst comprises a first metal and optionally a second metal as described above, wherein preferably, the fresh hydrogenation catalyst has the same first metal and optionally the same second metal as the spent / regenerated hydrogenation catalyst.

[0060] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the fresh hydrogenation catalyst (fhc) comprises at least a part of the first metal in oxidation state 0 and a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 100 : 0, more preferably in the range of from 80 : 20, more preferably in the range of from 55-70 : 30-45, determined by XRD.

[0061] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the fresh hydrogenation catalyst (fhc) comprises less than 5 weight-% of carbon and / or, preferably and, less than 0.1 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the fresh hydrogenation catalyst being 100 weight-%. It is noted that the content of carbon and / or nitrogen is only related to the fresh hydrogenation catalyst, not to any support, which might be comprises in a catalytic material.

[0062] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the fresh hydrogenation catalyst (fhc) has a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 mol / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter in the range of from 0.1-1000 nm, preferably in the range of from 10 to 500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0063] Activated hydrogenation catalyst

[0064] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the activated hydrogenation catalyst (ahc) has a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of > 98 % based on 100 % being the maximum normalized H2 consumption. In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the activated hydrogenation catalyst (ahc) has an overall surface area in the range of froml to 1200 m2 / g, more preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131.

[0065] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the activated hydrogenation catalyst (ahc) comprises at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD.

[0066] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the activated hydrogenation catalyst (ahc) comprises less than 5 weight-% of carbon and / or, preferably and, less than 2 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the activated hydrogenation catalyst being 100 weight-%. It is noted that the content of carbon and / or nitrogen is only related to the activated hydrogenation catalyst, not to any support material, which might be comprises in a catalytic material.

[0067] In some preferred embodiments of the process for regenerating an at least partially spent hydrogenation catalyst, the activated hydrogenation catalyst (ahc) has a pore volume in the range of fromO.1 to 2.0 ml / g; more preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter in the range of from 0.1-1000 nm, more preferably in the range of from 10-500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0068] An overview of the characteristics of the catalyst’s states is shown in Table A below:

[0069] Table A

[0070] Overview of the characteristics of the catalyst’s states

[0071] Table A - continuation support material.

[0072] 2ndaspect - Activation of fresh catalyst

[0073] In a second aspect, the invention relates to a method for activating a fresh hydrogenation catalyst, comprising

[0074] (A) providing a liquid aqueous mixture comprising a fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group;

[0075] (B) applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A); thereby obtaining an activated hydrogenation catalyst.

[0076] All details, embodiments and preferred embodiments disclosed above in the section related to the first aspect of the invention apply also to the second aspect of the invention.

[0077] In some preferred embodiments of the method for activating a fresh hydrogenation catalyst, applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A) in step (B) is done for at least 10 seconds, preferably at least 20 seconds, more preferably at least 30 seconds. In some preferred embodiments of the method for activating a fresh hydrogenation catalyst, applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A) in step (B) is done for at least 1 minute, preferably for at least 5 minutes, more preferably for at least 10 minutes, more preferably for at least 15 minutes, more preferably for at least 20 minutes, more preferably for at least 25 minutes, more preferably for at least 30 minutes; and / or is done for at the outmost 170 hours, preferably for at the outmost 160 hours, more preferably for at the outmost 150 hours, more preferably for at the outmost 120 hours, more preferably for at the outmost 110 hours, more preferably for at the outmost 100 hours, more preferably for at the outmost 90 hours, more preferably for at the outmost 80 hours.

[0078] In some preferred embodiments of the method for activating a fresh hydrogenation catalyst, (A) comprises

[0079] (A.1) providing a liquid aqueous mixture comprising spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group;

[0080] (A.2) adding fresh hydrogenation catalyst to the mixture provided in (A.1), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group; or

[0081] (A.1’) providing a fresh hydrogenation catalyst, optionally in aqueous suspension;

[0082] (A.2’) adding a liquid aqueous mixture comprising spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group to the fresh hydrogenation catalyst provided in (A.T), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group.

[0083] In some preferred embodiments of the method for activating a fresh hydrogenation catalyst, (B) is

[0084] (B’) applying a hydrogen containing gas onto the liquid aqueous mixture of (A.2) or (A.2’); thereby obtaining a mixture comprising at least partially regenerated hydrogenation catalyst and activated fresh catalyst.

[0085] Regarding duration of (B’), the same applies as described herein above with respect to step (B).

[0086] 3rdaspect - Combined process with hydrogenation and regeneration

[0087] A third aspect of the invention is directed to a combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, wherein the hydrogenation comprises

[0088] (I) applying under hydrogenation conditions into a liquid aqueous mixture, which is present in a hydrogenation zone and which comprises a suspended hydrogenation catalyst and a compound having at least one nitro group (hydrogenation reactant), a hydrogen containing gas, thereby obtaining a liquid aqueous mixture comprising an at least partially spent suspended hydrogenation catalyst and a compound having at least one amino group (hydrogenation product);

[0089] (II) removing at least a part of the liquid aqueous mixture obtained in (I) from the hydrogenation zone; wherein the regeneration comprises

[0090] (i) passing the at least part of the liquid aqueous mixture removed in (II) into a regeneration zone;

[0091] (ii) establishing in the liquid aqueous mixture in the regeneration zone a hydrogen (H2) concentration CH2(2) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture, thereby obtaining a liquid aqueous mixture comprising an at least partially regenerated hydrogenation catalyst in suspended form and the compound having at least one amino group.

[0092] Preferably, the liquid aqueous mixture, which is present in a hydrogenation zone according to (I) has an overall volume V(l). Preferably, the at least part thereof removed according to (II) has a volume V(l I), with V(l I) < V(l). Preferably, V(l I) is in the range of from 0.001 x V(l) to 0.9 x V(l), more preferably, V(l I) is in the range of from 0.005 x V(l) to 0.8 x V(l) , more preferably, V(l I) is in the range of from 0.005 x V(l) to 0.7 x V(l).

[0093] “Regeneration zone” and “hydrogenation zone” are preferably spacely separated from each other, more preferably the regeneration zone is a regeneration reactor and the hydrogenation zone is a hydrogenation reactor, preferably as described in more detail below. The at least part of the liquid aqueous mixture removed in (II), which is passed into a regeneration zone in (i), comprises the compound comprising at least one nitro group in < 5000 weight-ppm, so that also the liquid aqueous mixture in the regeneration zone, in which the concentration CH2(2) is established, comprises the compound comprising at least one nitro group in < 5000 weight-ppm. All details, embodiments and preferred embodiments disclosed above in the section related to the first aspect of the invention as well as in the section related to the second aspect of the invention apply also to the third aspect of the invention.

[0094] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, (i) comprises (1.1) passing the at least part of the liquid aqueous mixture removed in (II) into a regeneration zone;

[0095] (1.2) adding fresh hydrogenation catalyst to the liquid mixture in the regeneration zone, thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst;

[0096] (ii) establishing in the liquid aqueous mixture in the regeneration zone a hydrogen (H2) concentration CH2(2) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture, thereby obtaining a liquid aqueous mixture comprising an at least partially regenerated hydrogenation catalyst and activated hydrogenation catalyst in suspended form and the compound having at least one amino group.

[0097] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst,

[0098] (1.1) comprises

[0099] (1.1.1) passing at least part of the liquid aqueous mixture removed in (II) into a regeneration zone; and / or

[0100] (1.1.2) passing at least part of the liquid aqueous mixture removed in (II) into a separation zone, separating the at least partially spent hydrogenation catalyst from the part of the liquid aqueous mixture; and passing the separated at least partially spent hydrogenation catalyst, optionally as liquid aqueous mixture, into a regeneration zone.

[0101] The at least part of the liquid aqueous mixture removed in (II) comprises the at least partially spent hydrogenation catalyst in a concentration c(ll). In step (i.1.2), a concentration takes place in that, if a liquid mixture is obtained, which is then passed into the regeneration zone, said liquid aqueous mixture comprises the at least partially spent hydrogenation catalyst in a concentration c(i.1.2), with c(i.1.2) > c(l I). Preferably, c(i.1.2) is in the range of from 1.0 x c(ll) to 40 x c(l I), more preferably in the range of from 1.01 x c(l I) to 20 x c(ll), more preferably in the range of from 1.01 x c(ll) to 10 x c(ll).

[0102] Also regarding (i.1) and (i.2) as well as (i.1.1) and (i.1.2), the same applies as described above with respect to the compound comprising at least one nitro group being present in the respective liquid aqueous mixture in < 5000 weight-ppm.

[0103] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, (II) and (i), (ii) are conducted continuously or batchwise. In some embodiments, the regeneration is started “on demand”. For example, the temperature of the liquid aqueous mixture in the hydrogenation zone or the temperature of a feed to the hydrogenation zone Ti is determined and the temperature of at least one stream removed from the hydrogenation zone T2 is determined. Further, the value A(T) = T2 - T1 is determined; and if A (T) > 0, then (II) and (i), (ii) are conducted, preferably until A (T) < 0, or, if A (T) < 0, then (II) and (i), (ii) are not conducted. Alternatively or additionally, the concentration of the nitro components can also be monitored and regeneration is triggered or started if a target concentration is exceeded.

[0104] In some preferred embodiments, the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst further comprises

[0105] (iii) removing the liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated catalyst in suspended form and the compound having at least one amino group obtained in (ii) from the regeneration zone;

[0106] (iv) optionally separating the compound having at least one amino group from the liquid aqueous mixture removed in (iii), thereby obtaining a liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated hydrogenation catalyst in suspended form, which is depleted in compound having at least one amino group compared to the liquid aqueous mixture removed in (iii).

[0107] Preferably, the liquid aqueous mixture removed in (iii) comprises the compound having at least one amino group in a concentration c(1) and the liquid aqueous mixture obtained in (iv), which is depleted in compound having at least one amino group compared to the liquid aqueous mixture removed in (iii) comprises said compound having at least one amino group in a concentration c(2), with c(2) < c(1), wherein preferably, c(2) is in the range of from 0.0001 x c(1) to 0.99 x c(1), more preferably in the range of from 0.001 x c(1) to 0.9 x c(1), more preferably in the range of from 0.01 x c(1) to 0.8 x c(1).

[0108] In some preferred embodiments, the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst further comprises

[0109] (v) feeding the liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated catalyst in suspended form and the compound having at least one amino group removed in (iii) or the liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated catalyst in suspended form obtained in (iv) into the hydrogenation zone of (I). In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, the hydrogenation zone is a reactor, preferably a reactor selected from the group consisting of (multi)tubular reactor, stirred tank reactor and loop reactor, wherein the hydrogenation vessel is preferably a loop reactor and / or the regeneration zone is preferably a reactor, more preferably a reactor selected from the group consisting of (multi)tubular reactor, stirred tank reactor and loop reactor, wherein the hydrogenation vessel is preferably a loop reactor.

[0110] Reaction zone

[0111] In some embodiments of the hydrogenation process, the reaction vessel is a reactor selected from the group consisting of (multi)tubular reactor, stirred tank reactor and loop reactor, wherein the reaction vessel is preferably a loop reactor.

[0112] The product, i.e. the compound having at least one amino group, is discharged from the system continuously or discontinuously, preferably continuously, at any desired point, but preferably at a point in the lower region of the reactor at its base or in particular from the external loop flow via a catalyst separation unit or without one. This separation unit can be a gravity separator, for example a settler, a suitable filter, for example a cross-flow filter, or a centrifuge. The catalyst can be separated from the product and then the catalyst can be fed back into the reactor system or discharged from the reactor system. The product is preferably discharged with retention of the catalyst. The product can then be purified by conventional and known methods, for example by distillation or extraction.

[0113] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, applying the hydrogen containing gas in (I) is done at a pressure in the range of 0.1 to 200 bar, preferably in the range of from 0.01 to 100 bar, more preferably in the range of from 0.01 to 50 bar, more preferably in the range of from 15 to 40 bar, more preferably in the range of from 20 to 30 bar.

[0114] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, the hydrogen containing gas applied in (I) comprises at least 90 volume-%, preferably in the range of from 90 to 100 volume-%, of hydrogen, based on the total volume of the hydrogen containing gas being 100 volume-%. In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, the hydrogen containing gas applied in (I) comprises at least less than 0.1 volume-% of carbon monoxide, preferably less than 0.1 volume-% of carbon monoxide and less than 0.1 volume-% of oxygen, based on the total volume of the hydrogen containing gas being 100 volume-%.

[0115] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, applying hydrogen containing gas in (I) is done at a temperature in the range of from 50 to 200 °C, preferably in the range of from 60 to 180 °C, more preferably in the range of from 70 to 150 °C.

[0116] In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, the hydrogenation is carried out continuously or discontinuously (batch wise), preferably continuously. In some preferred embodiments of the combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, the regeneration is carried out continuously or discontinuously (batch wise).

[0117] 4thaspect - Activated hydrogenation catalyst

[0118] A fourth aspect of the invention relates to an activated hydrogenation catalyst, obtained or obtainable from the process of the first aspect or of the second aspect.

[0119] The fourth aspect of the invention is also directed to an activated hydrogenation catalyst (ahc) having a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of > 98 % based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, having an overall surface area in the range of from 1 to 1200 m2 / g, preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131 ; and / or, preferably and, comprising at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95- 100 : 0-5, determined by XRD; and / or, preferably and, comprising less than 5 weight-% of carbon and / or, preferably and, less than 2 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the activated hydrogenation catalyst being 100 weight-%; and / or, preferably and, having a pore volume in the range of from

[0120] 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 ml / g, determined by Hg po- rosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, having a pore diameter 0.1 to 1000 nm, preferably in the range of from 10 to 500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0121] It is noted that the content of carbon and / or nitrogen is only related to the activated hydrogenation catalyst, not to any support material, which might be comprises in a catalytic material.

[0122] All details, embodiments and preferred embodiments disclosed above in the section related to the first aspect of the invention, the section related to the third aspect of the invention, apply also to the fourth aspect of the invention.

[0123] 5thaspect - At least partially regenerated hydrogenation catalyst

[0124] A fifth aspect of the invention relates to an at least partially regenerated catalyst, obtained or obtainable from the process of the first aspect of the invention or of the third aspect of the invention.

[0125] The fifth aspect of the invention also relates to an at least partially regenerated hydrogenation catalyst (rhe), having a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of in the range of from 98 to 100 %, based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, having an overall surface area in the range of from <1200 m2 / g, preferably < 800 m2 / g, more preferably < 500 m2 / g, more preferably< 250 m2 / g, more preferably < 200 m2 / g, more prefera- bly< 120 m2 / g, more preferably <60 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131 ; and / or, preferably and, comprising at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95- 100 : 0-5, determined by XRD; and / or, preferably and, comprising < 25 weight-%, preferably < 10 weight-%, more preferably < 5 weight-% of carbon and < 6 weight-%, preferably < 3 weight-%, more preferably < 1 weight-%, of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially regenerated hydrogenation catalyst being 100 weight-%; and / or, preferably and, having a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, preferably <1.4 ml / g, more preferably <1.0 ml / g, more preferably <0.8 ml / g, more preferably <0.6 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, having a pore diameter < 800 nm, preferably < 250 nm, more preferably < 150 nm, more preferably < 100 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133. It is noted that the content of carbon and / or nitrogen is only related to the partially regenerated hydrogenation catalyst, not to any support material, which might be comprises in a catalytic material.

[0126] All details, embodiments and preferred embodiments disclosed above in the section related to the first aspect of the invention, the section related to the second aspect of the invention, and the section related to the third aspect of the invention apply also to the fifth aspect of the invention.

[0127] 6thaspect - Use of the regenerated and / or activated hydrogenation catalyst

[0128] A sixth aspect of the invention is directed to the use of the at least partially regenerated and / or activated hydrogenation catalyst of the fourth or fifth aspect as a hydrogenation catalyst, preferably for the hydrogenation of a compound having at least one nitro group. The sixth aspect of the invention also relates to a method for preparing a compound having at least one amino group comprising

[0129] (I) providing the at least partially regenerated and / or activated hydrogenation catalyst of any one of embodiments 55 to 56 and providing a compound having at least one nitro group;

[0130] (II) reacting the compound having at least one nitro group in the presence of the at least partially regenerated and / or activated hydrogenation catalyst provided in (I) under hydrogenation conditions with hydrogen; thereby obtaining a compound having at least one amino group.

[0131] All details, embodiments and preferred embodiments disclosed above in the section related to the first aspect of the invention, the section related to the second aspect of the invention, the section related to the third aspect of the invention, the section related to the fourth aspect of the invention and the section related to the fifth aspect of the invention apply also to the sixth aspect of the invention.

[0132] 7thaspect - Reaction system with hydrogenation vessel (reactor) and regeneration vessel

[0133] In a seventh aspect, the invention relates to a reaction system for combined hydrogenation of a compound having at least one nitro group and regeneration of an at least partially spent hydrogenation catalyst comprising:

[0134] (a) a hydrogenation vessel having

[0135] (a.1) means for feeding gaseous and liguid materials into the hydrogenation vessel;

[0136] (a.2) means for intermixing in the hydrogenation vessel,

[0137] (a.3) an outlet for removing a liguid agueous mixture from the hydrogenation vessel;

[0138] (a.4) at least one inlet for reintroduction of a liguid agueous mixture;

[0139] (a.5) circuit lines outside of the hydrogenation vessel in fluid connection to the outlet (a.3) and inlet (a.4), which enable withdrawal of a liguid agueous mixture from the hydrogenation vessel via outlet (a.3) and reintroduction of the liguid agueous mixture into the hydrogenation vessel via the inlet (a.4);

[0140] (a.6) optionally means for introducing fresh catalyst;

[0141] (b) a regeneration vessel comprising

[0142] (b.1) at least one inlet (b.1.1) for feeding a liguid agueous mixture into the regeneration vessel,

[0143] (b.2) at least one outlet (b.1.2) for removing a liguid agueous mixture from the regeneration vessel;

[0144] (b.3) means for intermixing in the regeneration vessel;

[0145] (b.4) means for feeding hydrogen gas into the regeneration vessel;

[0146] (b.5) optionally means for introducing fresh catalyst; and

[0147] (c.a) lines in fluid connection with at least one further outlet (a.7) of the hydrogenation vessel of (a) and the at least one inlet (b.1.1) of the regeneration vessel of (b) and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.8) of the of the hydrogenation vessel of (a); or

[0148] (c.b) lines in fluid connection with at least one outlet (a.5. out) of the circuit lines (a.5) and the at least one inlet (b.1.1) of the regeneration vessel (b) and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.5. in) of the of the circuit lines (a.5); wherein all lines are built and arranged to allow transfer of a liquid aqueous mixture from an outlet to the respective inlet.

[0149] All details, embodiments and preferred embodiments disclosed above in the section related to the first aspect of the invention, the section related to the second aspect of the invention, the section related to the third aspect of the invention, the section related to the fourth aspect of the invention, the section related to the fifth aspect of the invention, and the section related to the sixth aspect of the invention apply also to the seventh aspect of the invention.

[0150] In some preferred embodiments, the reaction system comprises

[0151] (x) a separation vessel for separating a suspended catalyst from a liquid aqueous mixture, preferably located between hydrogenation vessel and regeneration vessel, the separation vessel comprising;

[0152] (x.1) at least one inlet (x.1.1) for feeding a liquid aqueous mixture into the separation vessel, (x.2) at least one outlet (x.1.2) for removing a liquid aqueous mixture from the regeneration vessel and at least one outlet (x.1 .3) for removing separated catalyst from the separation vessel; wherein (c.a.) comprises

[0153] (c.a’) lines in fluid connection with at least one further outlet (a.7) of the hydrogenation vessel of (a) and the at least one inlet (x.1.1) of the separation vessel (x), lines in fluid communication of the at least one outlet (x.1 .3) of the separation vessel (x) and the at least one inlet (b.1.1) of the regeneration vessel of (b), and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.8) of the of the hydrogenation vessel of (a); wherein all lines are built and arranged to allow transfer of a liquid aqueous mixture from an outlet to the respective inlet. The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0154] 1 . A process for regenerating an at least partially spent hydrogenation catalyst comprising:

[0155] (a) providing a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2(1 ) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture;

[0156] (b) maintaining a concentration CH2(2) of hydrogen (H2) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture in the liquid aqueous mixture, thereby obtaining an at least partially regenerated hydrogenation catalyst.

[0157] 2. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 1 , wherein the at least partially spent hydrogenation catalyst (she) of (a) has an overall surface area of <1200 m2 / g, preferably <800 m2 / g, more preferably <500 m2 / g, more preferably <250 m2 / g, more preferably <200 m2 / g, more preferably <120 m2 / g, more preferably <60 m2 / g, more preferably <40 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131.

[0158] 3. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 1 or 2, wherein the at least partially regenerated hydrogenation catalyst (rhe) has an overall surface area <1200 m2 / g m2 / g, more preferably <800 m2 / g m2 / g, more preferably <500 m2 / g m2 / g, more preferably <250 m2 / g, more preferably <200 m2 / g, more preferably <120 m2 / g, more preferably <60 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131.

[0159] 4. The process of any one of embodiments 1 to 3, wherein the at least partially spent hydrogenation catalyst (she) of (a) has a normalized H2 consumption when used under hydro- genation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of<95, preferably <96, more preferably <97, more preferably

[0160] < 98 %, based on 100 % being the maximum normalized H2 consumption.

[0161] 5. The process of any one of embodiments 1 to 4, wherein the at least partially regenerated hydrogenation catalyst (rhe) obtained in (b) has a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant or intermediate) of in the range of from 98 to 100 %, based on 100 % being the maximum normalized H2 consumption.

[0162] 6. The process of any one of embodiments 1 to 5, wherein the at least partially spent hydrogenation catalyst (she) of (a) comprises in the range of from 0 to less than 25 weight-% of carbon and in the range of from 0 to less than 6 weight-% of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially spent hydrogenation catalyst being 100 weight-%; and / or, preferably and, the at least partially regenerated hydrogenation catalyst (rhe) of (b) comprises in the range of from 0 to less than 25 weight-%, preferably in the range of from 0 to less than 10 weight-%, more preferably in the range of from 0 to less than 5 weight-%, of carbon and in the range of from 0 to less than 6 weight-%, preferably in the range of from 0 to less than 3 weight-%, more preferably in the range of from 0 to less than 1 weight-%, of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially spent hydrogenation catalyst being 100 weight-%.

[0163] 7. The process of any one of embodiments 1 to 6, wherein the at least partially spent hydrogenation catalyst (she) of (a) has a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably of <1.4ml / g, more preferably <1.0 ml / g, more preferably <0.8 ml / g, more preferably <0.6 ml / g, determined byHg po- rosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter of <800 nm, preferably <250 nm, more preferably <150 nm, more preferably <100 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0164] 8. The process of any one of embodiments 1 to 7, wherein the at least partially regenerated hydrogenation catalyst (rhe) of (b) has a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably of <1.4ml / g, more preferably <1.0 ml / g, more preferably <0.8 ml / g, more preferably <0.6 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter of <800 nm, preferably <250 nm, more preferably <150 nm, more preferably <100 nm, determined by Hg porosimetry, wherein Hg porosim- etry is determined in particular according to DIN 66133.

[0165] 9. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 8, wherein the liquid aqueous mixture provided in (a) comprises in the range of from 20 to 90 weight-%, preferably in the range of from 30 to 85 weight-%, more preferably in the range of from 40 to 80 weight-%, more preferably in the range of from 50 to 70 weight-% of a compound comprising at least one amino group, which does not comprise a nitro group, based on the total weight of the liquid aqueous mixture being 100 weight-%.

[0166] 10. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 9, wherein in the range of from 95 to 100 weight-%, preferably in the range of from 98 to 100 weight-%, more preferably in the range of from 99 to 100 weight- %, more preferably in the range of from 99.5 to 100 weight-%, of the liquid aqueous mixture provided in (a) consist of hydrogen, the at least partially spent hydrogenation catalyst, water and compound comprising at least one amino group, based on the total weight of the liquid aqueous mixture being 100 weight-%; and / or, wherein the liquid aqueous mixture provided in (a) additionally comprises one or more C1 to C6 mono alcohol, preferably a C1 to C6 mono alcohol from the group consisting of C1 to C5 mono alcohols, more preferably selected from the group consisting of methanol, ethanol, propanol, including n-pro- panol and iso-propanol, and mixtures of two or three thereof, more preferably at least isopropanol.

[0167] 11 . The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 10, wherein in (a), the liquid aqueous mixture comprising H2 with CH2(1 ) is provided within a reaction zone; and wherein in (b), maintaining the H2 concentration CH2(2) is done by applying hydrogen containing gas onto the liquid aqueous mixture in said reaction zone at a pressure p in the range of 0.1 to 100 bar, preferably in the range of from 0.1 to 50 bar, more preferably in the range of from 15 to 40 bar, more preferably in the range of from 20 to 30 bar.

[0168] 12. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 11 , wherein the hydrogen containing gas comprises at least 90 volume-%, preferably in the range of from 90 to 100 volume-%, of hydrogen, based on the total volume of the hydrogen containing gas being 100 volume-%. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 12, wherein the hydrogen containing gas comprises at least less than 0.1 volume-% of carbon monoxide, preferably less than 0.1 volume-% of carbon monoxide and less than 0.1 volume-% of oxygen, based on the total volume of the hydrogen containing gas being 100 volume-%. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 13, wherein maintaining the H2 concentration CH2(2) in (b) is done at a temperature T in a reaction zone in the range of from 50 to 200 °C, preferably in the range of from 60 to 180 °C, more preferably in the range of from 70 to 150 °C. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 11 to 14, wherein the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) in the reaction zone is maintained with simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 15, wherein maintaining the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) and simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm in the reaction zone is done for at least 1 minute, preferably for at least 5 minutes, more preferably for at least 10 minutes, more preferably for at least 15 minutes, more preferably for at least 20 minutes, more preferably for at least 25 minutes, more preferably for at least 30 minutes; and / or is done for at the outmost 170 hours, preferably for at the outmost 160 hours, more preferably for at the outmost 150 hours, more preferably for at the outmost 120 hours, more preferably for at the outmost 110 hours, more preferably for at the outmost 100 hours, more preferably for at the outmost 90 hours, more preferably for at the outmost 80 hours. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 15 or 16, wherein maintaining the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (b) and simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-weight-ppm in the reaction zone is done for a period of time of in the range of from 1 minute to 170 hours, preferably in the range of from 1 minutes to 160 hours, more preferably in the range of from 1 minutes to 150 hours, more preferably in the range of from 1 minutes to 140 hours, more preferably in the range of from 1 minutes to 130 hours, more preferably in the range of from 1 minutes to 120 hours, more preferably in the range of from 1 minute to 110 hours, more preferably in the range of from 1 minute to 100 hours, more preferably in the range of from 1 minute to 100 hours, more preferably in the range of from 1 minute to 90 hours, more preferably in the range of from 1 minute to 80 hours.

[0169] 18. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 17, wherein the compound having at least one nitro group is a reactant of a hydrogenation reaction and comprises preferably at least a compound selected from the group consisting of 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2-amino-4-nitrotoluene, 2-amino-6-nitrotoluene and mixtures of two or more thereof and / or the compound having at least one amino group, which does not comprise a nitro group, is a product of a hydrogenation reaction and comprises preferably at least a compound selected from the group consisting of 2,4-diaminotoluene, 2,6-diaminotoluene and a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene.

[0170] 19. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 18, wherein the hydrogenation catalyst comprises at least one first metal of the I., II., V., VI. and / or VIII. subgroup of the periodic table of elements, preferably at least one metal of the I. and / or VIII. subgroup of the periodic table of the elements, more preferably at least one metal selected from the group consisting of nickel, platinum and palladium, optionally in combination with at least one second metal of the I., II., IV., V., VI. and / or VIII. subgroup of the periodic table of the elements, wherein the second metal is different from the first metal.

[0171] 20. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 19, wherein the hydrogenation catalyst comprises nickel, preferably nickel having an oxidation state 0, +1 , +2, +3 and / or +4, wherein the hydrogenation catalyst more preferably comprises in the range of from 0.1 to 99% by weight, preferably in the range of from 1 to 90% by weight, more preferably in the range of from 25 to 85% by weight, more preferably in the range of from 60 and 80 % by weight, of Ni(0) and / or one or more nickel containing compounds, wherein the nickel has an oxidation state 0, +1 , +2, +3 and / or +4, based on the total weight of the hydrogenation catalyst being 100 weight-%.

[0172] 21. The process for regenerating an at least partially spent hydrogenation catalyst of embodiment 19 or 20, wherein the second metal of the I., II., IV., V., VI. and / or VIII. subgroup of the Periodic Table is selected from the group consisting of palladium, platinum, rhodium, iron, cobalt, zinc, chromium, vanadium, copper, silver, zirconium, titanium, hafnium, and mixtures of two or more thereof. 22. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 1 to 21 , wherein the hydrogenation catalyst comprises a support which is preferably selected from the group consisting of activated carbon, carbon black, graphite, oxidic carrier component and mixtures of two or more thereof, wherein the oxidic carrier component is preferably selected from the group consisting of silicon dioxide, silicon carbide, kieselguhr, aluminum oxide, magnesium oxide, titanium dioxide, zirconium dioxide, hafnium dioxide and mixtures of two or more thereof, more preferably the oxidic carrier compound is selected from the group consisting of zirconium dioxide, silicon dioxide, hafnium dioxide and mixtures of two or more thereof, more preferably the oxidic carrier component comprises, more preferably is, zirconium dioxide and / or silicon dioxide.

[0173] 23. The process for regenerating an at least partially spent hydrogenation catalyst of any one of embodiments 19 to 22, wherein the at least partially spent hydrogenation catalyst (she) comprises at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 80-100 : 0-20, determined by XRD; and / or, preferably and, wherein the at least partially regenerated hydrogenation catalyst (rhe) comprises at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95- 100 : 0-5, determined by XRD.

[0174] 24. The process for regenerating an at least partially spent hydrogenation catalyst (she) of any one of embodiments 1 to 23, wherein the liquid aqueous mixture provided in (a) comprises the hydrogenation catalyst in suspended form and / or in slurry form.

[0175] 25. The process of any one of embodiments 1 to 24, wherein (a) comprises

[0176] (a.1) providing a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2(1);

[0177] (a.2) adding fresh hydrogenation catalyst to the mixture provided in (a.1), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, wherein the liquid aqueous mixture comprises dissolved hydrogen (H2) at a concentration CH2(1 ). The process of embodiment 25, wherein (b) is

[0178] (b’) maintaining a concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture provided in (a.2); thereby obtaining a mixture comprising at least partially regenerated hydrogenation catalyst and activated fresh catalyst. The process of any one of embodiments 26 to 28, wherein the fresh hydrogenation catalyst has an overall surface area in the range of from 1 to 1200 m2 / g, preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131. The process of any one of embodiments 25 to 27, wherein the fresh hydrogenation catalyst comprises a first metal and optionally a second metal as described in embodiments 19 to 22, wherein preferably, the fresh hydrogenation catalyst has the same first metal and optionally the same second metal as the spent / regenerated hydrogenation catalyst. The process of any one of embodiments 25 to 28, wherein the fresh hydrogenation catalyst (fhc) comprises at least a part of the first metal in oxidation state 0 and a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 100 : 0, more preferably in the range of from 80 : 20, more preferably in the range of from 55-70 : 30-45, determined by XRD. The process of any one of embodiments 25 to 29, wherein the fresh hydrogenation catalyst (fhc) comprises less than 5 weight-% of carbon and / or, preferably and, less than

[0179] 0.1 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the fresh hydrogenation catalyst being 100 weight-%. The process of any one of embodiments 25 to 30, wherein the fresh hydrogenation catalyst (fhc) has a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 mol / g, determined by Hg porosimetry, wherein Hg porosim- etry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter in the range of from 0.1-1000 nm, preferably in the range of from 10 to 500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0180] 32. The process of any one of embodiments 25 to 31 , wherein the activated hydrogenation catalyst (ahc) has a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of > 98 % based on 100 % being the maximum normalized H2 consumption.

[0181] 33. The process of any one of embodiments 25 to 32, wherein the activated hydrogenation catalyst (ahc) has an overall surface area in the range of froml to 1200 m2 / g, preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131.

[0182] 34. The process of any one of embodiments 25 to 33, wherein the activated hydrogenation catalyst (ahc) comprises at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD.

[0183] 35. The process of any one of embodiments 25 to 34, wherein the activated hydrogenation catalyst (ahc) comprises less than 5 weight-% of carbon and / or, preferably and, less than 2 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the activated hydrogenation catalyst being 100 weight-%.

[0184] 36. The process of any one of embodiments 25 to 35, wherein the activated hydrogenation catalyst (ahc) has a pore volume in the range of fromO.1 to 2.0 ml / g; preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, a pore diameter in the range of from 0.1-1000 nm, more preferably in the range of from IQ- 500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133. A method for activating a fresh hydrogenation catalyst, comprising

[0185] (A) providing a liquid aqueous mixture comprising a fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group;

[0186] (B) applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A); thereby obtaining an activated hydrogenation catalyst. The method of embodiment 37, wherein (A) comprises

[0187] (A.1) providing a liquid aqueous mixture comprising spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group;

[0188] (A.2) adding fresh hydrogenation catalyst to the mixture provided in (A.1), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group; or

[0189] (A.T) providing a fresh hydrogenation catalyst, optionally in aqueous suspension;

[0190] (A.2’) adding a liquid aqueous mixture comprising spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group to the fresh hydrogenation catalyst provided in (A.T), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group. The process of embodiment 37 or 38, wherein (B) is

[0191] (B’) applying a hydrogen containing gas onto the liquid aqueous mixture of (A.2) or (A.2’); thereby obtaining a mixture comprising at least partially regenerated hydrogenation catalyst and activated fresh catalyst. A combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, wherein the hydrogenation comprises

[0192] (I) applying under hydrogenation conditions into a liquid aqueous mixture, which is present in a hydrogenation zone and which comprises a suspended hydrogenation catalyst and a compound having at least one nitro group (hydrogenation reactant), a hydrogen containing gas, thereby obtaining a liquid aqueous mixture comprising an at least partially spent suspended hydrogenation catalyst and a compound having at least one amino group (hydrogenation product); (II) removing at least a part of the liquid aqueous mixture obtained in (I) from the hydrogenation zone; wherein the regeneration comprises

[0193] (iii) passing the at least part of the liquid aqueous mixture removed in (II) into a regeneration zone;

[0194] (iv) establishing in the liquid aqueous mixture in the regeneration zone a hydrogen (H2) concentration CH2(2), thereby obtaining a liquid aqueous mixture comprising an at least partially regenerated hydrogenation catalyst in suspended form and the compound having at least one amino group. The combined process of embodiment 40, wherein (i) comprises

[0195] (1.1) passing the at least part of the liquid aqueous mixture removed in (II) into a regeneration zone;

[0196] (1.2) adding fresh hydrogenation catalyst to the liquid mixture in the regeneration zone, thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst;

[0197] (ii) establishing in the liquid aqueous mixture in the regeneration zone a hydrogen (H2) concentration CH2(2), thereby obtaining a liquid aqueous mixture comprising an at least partially regenerated hydrogenation catalyst and activated hydrogenation catalyst in suspended form and the compound having at least one amino group. The combined process of embodiment 41 , wherein (i.1) comprises

[0198] (1.1.1)passing at least part of the liquid aqueous mixture removed in (II) into a regeneration zone; and / or

[0199] (1.1.2)passing at least part of the liquid aqueous mixture removed in (II) into a separation zone, separating the at least partially spent hydrogenation catalyst from the part of the liquid aqueous mixture; and passing the separated at least partially spent hydrogenation catalyst, optionally as liquid aqueous mixture, into a regeneration zone. The combined process of any one of embodiments 40 to 42, wherein (II) and (i), (ii) are conducted continuously or batchwise. The combined process of any one of embodiments 40 to 43, further comprising

[0200] (iii) removing the liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated catalyst in suspended form and the compound having at least one amino group obtained in (ii) from the regeneration zone; (iv) optionally separating the compound having at least one amino group from the liquid aqueous mixture removed in (iii), thereby obtaining a liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated hydrogenation catalyst in suspended form, which is depleted in compound having at least one amino group compared to the liquid aqueous mixture removed in (iii). The combined process of any one of embodiments 40 to 44, further comprising

[0201] (v) feeding the liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated catalyst in suspended form and the compound having at least one amino group removed in (iii) or the liquid aqueous mixture comprising the at least partially regenerated hydrogenation catalyst and optionally the activated catalyst in suspended form obtained in (iv) into the hydrogenation zone of (I). The combined process of any one of embodiments 40 to 45, wherein the hydrogenation zone is a reactor, preferably a reactor selected from the group consisting of (multi)tubular reactor, stirred tank reactor and loop reactor, wherein the hydrogenation vessel is preferably a loop reactor and / or the regeneration zone is preferably a reactor, more preferably a reactor selected from the group consisting of (multi)tubular reactor, stirred tank reactor and loop reactor, wherein the hydrogenation vessel is preferably a loop reactor. The combined process of any one of embodiments 40 to 46, wherein applying the hydrogen containing gas in (I) is done at a pressure in the range of from 0.1 to 200 bar, preferably in the range of from 0.1 to 100 bar, more preferably in the range of from 0.1 to 50 bar, more preferably in the range of from 15 to 40 bar, more preferably in the range of from 20 to 30 bar. The combined process of any one of embodiments 40 to 47, wherein the hydrogen containing gas applied in (I) comprises at least 90 volume-%, preferably in the range of from 90 to 100 volume-%, of hydrogen, based on the total volume of the hydrogen containing gas being 100 volume-%. The combined process of any one of embodiments 40 to 48, wherein the hydrogen containing gas applied in (I) comprises at least less than 0.1 volume-% of carbon monoxide, preferably less than 0.1 volume-% of carbon monoxide and less than 0.1 volume-% of oxygen, based on the total volume of the hydrogen containing gas being 100 volume-%. 50. The combined process of any one of embodiments 40 to 49, wherein applying hydrogen containing gas in (I) is done at a temperature in the range of from 50 to 200 °C, preferably in the range of from 60 to 180 °C, more preferably in the range of from 70 to 150 °C.

[0202] 51 . The combined process of any one of embodiments 40 to 50, wherein the hydrogenation is carried out continuously or discontinuously (batch wise), preferably continuously.

[0203] 52. The combined process of any one of embodiments 40 to 51 , wherein the regeneration is carried out continuously or discontinuously (batch wise).

[0204] 53. An at least partially regenerated hydrogenation catalyst, obtained or obtainable from the process of any one of embodiments 1 to 39 or 40 to 52.

[0205] 54. An activated hydrogenation catalyst, obtained or obtainable from the process of any one of embodiments 37 to 39.

[0206] 55. An activated hydrogenation catalyst (ahc) having a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of > 98 % based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, having an overall surface area in the range of from 1 to 1200 m2 / g, preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131 ; and / or, preferably and, comprising at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD; and / or, preferably and, comprising less than 5 weight-% of carbon and / or, preferably and, less than 2 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the activated hydrogenation catalyst being 100 weight-%; and / or, preferably and, having a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, having a pore diameter 0.1 to 1000 nm, preferably in the range of from 10 to 500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133. An at least partially regenerated hydrogenation catalyst (rhe), having a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of in the range of from 98 to 100 %, based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, having an overall surface area in the range of from <1200 m2 / g, preferably < 800 m2 / g, more preferably < 500 m2 / g, more preferably< 250 m2 / g, more preferably < 200 m2 / g, more preferably< 120 m2 / g, more preferably <60 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131 ; and / or, preferably and, comprising at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD; and / or, preferably and, comprising < 25 weight-%, preferably < 10 weight-%, more preferably < 5 weight-% of carbon and < 6 weight-%, preferably < 3 weight-%, more preferably < 1 weight-%, of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially regenerated hydrogenation catalyst being 100 weight-%; and / or, preferably and, having a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, preferably <1.4 ml / g, more preferably <1.0 ml / g, more preferably

[0207] <0.8 ml / g, more preferably <0.6 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, having a pore diameter < 800 nm, preferably < 250 nm, more preferably < 150 nm, more preferably < 100 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

[0208] 57. Use of the at least partially regenerated and / or activated hydrogenation catalyst of any one of embodiments 55 to 56 as a hydrogenation catalyst, preferably for the hydrogenation of a compound having at least one nitro group.

[0209] 58. A method for preparing a compound having at least one amino group comprising

[0210] (I) providing the at least partially regenerated and / or activated hydrogenation catalyst of any one of embodiments 55 to 56 and providing a compound having at least one nitro group;

[0211] (II) reacting the compound having at least one nitro group in the presence of the at least partially regenerated and / or activated hydrogenation catalyst provided in (I) under hydrogenation conditions with hydrogen; thereby obtaining a compound having at least one amino group.

[0212] 59. A reaction system for combined hydrogenation of a compound having at least one nitro group and regeneration of an at least partially spent hydrogenation catalyst comprising:

[0213] (a) a hydrogenation vessel having

[0214] (a.1) means for feeding gaseous and liquid materials into the hydrogenation vessel;

[0215] (a.2) means for intermixing in the hydrogenation vessel,

[0216] (a.3) an outlet for removing a liquid aqueous mixture from the hydrogenation vessel; (a.4) at least one inlet for reintroduction of a liquid aqueous mixture;

[0217] (a.5) circuit lines outside of the hydrogenation vessel in fluid connection to the outlet (a.3) and inlet (a.4), which enable withdrawal of a liquid aqueous mixture from the hydrogenation vessel via outlet (a.3) and reintroduction of the liquid aqueous mixture into the hydrogenation vessel via the inlet (a.4);

[0218] (a.6) optionally means for introducing fresh catalyst;

[0219] (b) a regeneration vessel comprising

[0220] (b.1) at least one inlet (b.1.1) for feeding a liquid aqueous mixture into the regeneration vessel,

[0221] (b.2) at least one outlet (b.1.2) for removing a liquid aqueous mixture from the regeneration vessel;

[0222] (b.3) means for intermixing in the regeneration vessel;

[0223] (b.4) means for feeding hydrogen gas into the regeneration vessel; (b.5) optionally means for introducing fresh catalyst; and

[0224] (c.a) lines in fluid connection with at least one further outlet (a.7) of the hydrogenation vessel of (a) and the at least one inlet (b.1.1) of the regeneration vessel of (b) and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.8) of the of the hydrogenation vessel of (a); or

[0225] (c.b) lines in fluid connection with at least one outlet (a.5. out) of the circuit lines (a.5) and the at least one inlet (b.1.1) of the regeneration vessel (b) and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.5. in) of the of the circuit lines (a.5); wherein all lines are built and arranged to allow transfer of a liquid aqueous mixture from an outlet to the respective inlet.

[0226] 60. The reaction system of embodiment 59, comprising

[0227] (x) a separation vessel for separating a suspended catalyst from a liquid aqueous mixture, preferably located between hydrogenation vessel and regeneration vessel, the separation vessel comprising;

[0228] (x.1) at least one inlet (x.1.1) for feeding a liquid aqueous mixture into the separation vessel,

[0229] (x.2) at least one outlet (x.1.2) for removing a liquid aqueous mixture from the regeneration vessel and at least one outlet (x.1.3) for removing separated catalyst from the separation vessel; wherein (c.a.) comprises

[0230] (c.a’) lines in fluid connection with at least one further outlet (a.7) of the hydrogenation vessel of (a) and the at least one inlet (x.1.1) of the separation vessel (x), lines in fluid communication of the at least one outlet (x.1.3) of the separation vessel (x) and the at least one inlet (b.1.1) of the regeneration vessel of (b), and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.8) of the of the hydrogenation vessel of (a); wherein all lines are built and arranged to allow transfer of a liquid aqueous mixture from an outlet to the respective inlet.

[0231] The present invention is further illustrated by the following reference examples, comparative examples, and examples. Examples

[0232] Chemicals

[0233] The supported catalyst was prepared as described in Example 2 of WO 2021 / 219796 A1.

[0234] General set-up 1 : laboratory circuit test rig used for hydrogenation

[0235] The laboratory circuit test rig used for hydrogenation consisted of a two-syringe feed pump, a high-pressure H2 dosage pipe, a pipe coil (reaction zone), a stirred tank (mixing zone if in-line or regeneration vessel if in by-pass), a gas-liquid separator, a (cross flow) filtration unit, and a circulation pump. Liquid hydrogenation product (and water) was filtrated portion wise by (cross flow) filtration and sampled by an online-GC. Performance indicators have been time on stream (TOS), GC-derived yields of TDA and heavy boilers, converted DNT per gram of catalyst, and catalyst consumption (Ni ll / R). The test rig was isothermally operated.

[0236] Reference (comparative) Example 1 : hydrogenation without regeneration (laboratory plant)

[0237] In a typical laboratory hydrogenation as described in the general set-up 1 above, the test rig was filled with water (0.6 I) and catalyst (7 g). Then, water and catalyst were recirculated with 100 kg / h in the test rig and the operation conditions were applied by setting the temperature to 125-130°C and the pressure to 25 bar by pressurizing with H2, so that a concentration of H2 in the range of from 0.001 to 3 g / liter, especially in the range of from 0.04 to 0.15 g / liter, of liquid aqueous mixture was established. These conditions applied for 1 h have activated the fresh catalyst. Subsequently, 90°C preheated DNT (approx. 0.5-1 ml / min), corresponding to a weight hourly space velocity (WHSV) of 7-10 g(DNT) / g(cat.) / h, was dosed into the system by a continuously operating two-syringe pump. The DNT was immediately converted in the initial section of the reaction pipe coil and formed the hydrogenation bath comprising catalyst, water, and TDA. The hydrogenation bath was further transferred into the stirred tank (V = 0.2 I, rotation rate = 1000 rpm), which acted as additional mixing zone. Then, the hydrogenation bath was transferred via the gas-liquid separation vessel (separation of 10% off-gas), via the cross flow filter (separation of product TDA and water equivalent to the DNT feed) and via the circulation pump back into the reaction pipe coil, wherein this sequence was repeated over and over again. The catalyst was operated for 75 h TOS without regeneration and converted 7 kg of DNT (1 kg converted DNT per g of catalyst) before severe deactivation in form of drastic TDA yield loss has occurred.

[0238] Example 1 : hydrogenation with regeneration (batch wise; lab. plant)

[0239] The laboratory circuit test rig for the hydrogenation as described in the general set-up 1 above was started and operated as described in Reference Example 1 , but only one syringe of the two-syringe feed pump was applied for the dosage of DNT. Thus, every 5 h the applied syringe was refilled with fresh DNT for 5 min. During this time, DNT was not fed into the test rig.

[0240] A hydrogenation of DNT was carried out in a laboratory plant as described in Reference Example 1 without regeneration (Comparative Example 1) and with regeneration carried out continuously for the complete catalyst batch (Example 1), using a weight hourly space velocity (WHSV) in the range of from 7 to 10 g / g / h for a certain time (time on stream, TOS).

[0241] Regeneration of the complete catalyst batch in Example 1 was carried out batch wise at a temperature of 125°C and a H2 pressure of 25 bar by continuously stopping the DNT feed for 5 minutes every 5 hours. The results are graphically shown in Fig. 1 for Comparative Example 1 and for Example 1. A comparison especially with regard to TOS, DNT conversion per g(cat.) and catalyst consumption (Ni ll / R) is also shown below in Table 1.

[0242] It could be seen from Comparative Example 1 that without regeneration, the catalyst could only be used for a time on stream of 75 hours. After that, the catalyst becomes deactivated and the conversion into the desired product TDA decreases, while the generation of side products such as high boilers (meaning poly and / or oligomers of TDA) and intermediate products (ANT, not shown) increases significantly.

[0243] Example 1 showed on the contrary that a, preferably continuous, regeneration treatment of the complete catalyst batch in the test rig with hydrogen in presence of the hydrogenation bath consisting of TDA and water and absence of new portions of catalyst poison (DNT), enabled the catalyst to carry out the hydrogenation of DNT in an efficient manner for a threefold longer time span (210 hours) compared to Comparative Example 1. Furthermore, it could be seen that the catalyst’s consumption is reduced (i.e. improved) since per gram catalyst the 1 .6 fold amount of DNT is converted into TDA in Example 1 compared to Comparative Example 1 , i.e. the catalyst consumption could be reduced from 1.5 to 0.9 kg(cat.) / t(TDA).

[0244] Example 2: hydrogenation with regeneration (continuous semibatch wise; laboratory plant)

[0245] A continuous semi-batch regeneration was conducted in the laboratory circuit test rig as described in the general set-up 1 above, using the conditions etc. as described in Reference Example 1. The stirred tank was used as regeneration vessel in that a portion (V = 100 ml) of the hydrogenation bath comprising the catalyst (m(cat.) = 2.3 g), TDA and water was kept in the stirred tank, where the spent catalyst was regenerated for 30 min also under 25 bar H2 and without temperature change (125°C) with < 100 weight-ppm DNT and < 2000 weight-ppm ANT in the hydrogenation bath. Then, another portion of hydrogenation bath comprising the catalyst, TDA and water from the reaction pipe coil was passed through the stirred tank (for 30 seconds) and the content therein was thereby replaced with a new portion of hydrogenation bath comprising spent catalyst, TDA and water. After said 30 seconds, the stirred tank containing hydrogenation bath comprising spent catalyst, TDA and water was again operated in by-pass. The now confined spent catalyst (with TDA and water) in the stirred tank then remained under regeneration conditions for 30 minutes, while the regenerated catalyst has been applied in the hydrogenation reaction together with the remaining catalyst in the test rig. The steps of exchanging the hydrogenation bath in the regeneration vessel (stirred tank), execution of the regeneration, discharge and the parallel hydrogenation are repeated again and again.

[0246] Regeneration of the portions of catalyst (m(cat.) = 2.3 gram) in Example 2 was carried out semibatch batch wise for 30 minutes in the regeneration vessel (stirred tank) at a temperature of 125°C under stirring. The results are graphically shown for Comparative Example 1 and Example 2 in Fig. 1 . A comparison especially with regard to the converted amounts of DNT and catalyst consumption (Ni ll / R) is also shown below in Table 1. Example 2 showed that a, preferably continuous, regeneration treatment of a portion of catalyst batch in the separated regeneration vessel with hydrogen in presence of the hydrogenation bath consisting of TDA and water, enabled the catalyst to carry out the hydrogenation of DNT in an efficient manner for a fivefold longer time span (420 hours) compared to Comparative Example 1. Furthermore, it could be seen that the catalyst’s consumption is drastically reduced (i.e. improved) since per gram catalyst the 2.4 fold amount of DNT is converted into TDA in Example 2 compared to Comparative Example 1 , i.e. the catalyst consumption could be reduced from 1.5 to 0.6 kg(cat.) / t(TDA).

[0247] Furthermore, for Example 2, the consumption of H2 in the regeneration vessel (stirred tank) was determined over time. For this purpose, the regeneration vessel was repressurized to 25 bar and locked without further re-pressurization of H2. Then, the pressure decline in the regeneration vessel was monitored. By applying the ideal gas law the H2 consumption was determined. Based thereon, it was found that H2 was consumed for 30 minutes. Thereafter, catalyst regeneration was completed and no further F^was consumed.

[0248] Table 1

[0249] Hydrogenation with or without catalyst regeneration converted DNT in kg per g of catalyst catalyst consumption in kg of catalyst per ton of TDA produced

[0250] General set-up 2: miniplant with recycle flow used for hydrogenation

[0251] The miniplant with recycle flow used for the hydrogenation consisted of a jet loop reactor with internal draft tube (reaction zone). Pre-heated nitroaromatic feed and H2 were dosed into the headspace of the reactor in close proximity to the recycle nozzle, which has been directed into the draft tube. Product stream was recycled from the reactor bottom outlet through a circulation pump and a (cross flow) filtration unit, where portions of the product stream were withdrawn and sampled by an online-GC. Remaining product stream was recirculated via nozzle into the draft tube. Performance indicators have been time on stream (TOS), GC-derived yields of TDA, ANT and heavy boilers, DNT conversion per g(cat.), and catalyst consumption (Ni ll / R).

[0252] Reference (comparative) Example 2: hydrogenation without regeneration (miniplant) In a typical miniplant hydrogenation without regeneration, the miniplant as described in general set-up 2 above, was filled with water (5 I) and catalyst (141 g). Then, for fresh catalyst activation, the catalyst in water has been recirculated at 135°C and 25 bar (H2) for 3 h with 500 kg / h in the miniplant. A concentration of hydrogen (H2) in the liquid aqueous mixture in the range of from 0.001 to 3 g / liter, especially in the range of from 0.04 to 0.15 g / liter, of liquid aqueous mixture was established. Subsequently, 90°C preheated DNT (1 kg / h), corresponding to a weight hourly space velocity (WHSV) of 7 g(DNT) / g(cat.) / h, was dosed into the system. The DNT was immediately converted in the initial section of the draft tube and formed the hydrogenation bath comprising catalyst, water, and TDA. The hydrogenation bath was further transferred through the circulation pump, via the cross flow filter (separation of product TDA and water equivalent to the DNT feed) and through the nozzle back into the draft tube, wherein this sequence was repeated over and over again. Typically, the catalyst could be operated for 24-48 h TOS before severe deactivation in form of drastic TDA yield loss has occurred.

[0253] Example 3: hydrogenation with regeneration (batch wise, miniplant)

[0254] The miniplant as described in general set-up 2 above, with recycle flow used for the hydrogenation with regeneration was operated identically as described in Reference Example 2. However, every time a decline of the TDA yield of at least 1 % was observed (and exceptionally, after 70 hours TOS) the complete catalyst batch was regenerated by stopping the DNT feed. Then, the accumulated intermediates (ANT) were converted within 10-30 min and the resulting hydrogenation bath comprising catalyst, TDA and water was kept under 25 bar H2 at 90°C for 3 to 72 hours without circulation. Subsequently, the hydrogenation bath was re-heated to 135°C, recycled and the DNT feed was re-started. This sequence was repeated over and over again. After 315 hours TOS the hydrogenation was stopped without reaching the catalyst’s end of lifetime.

[0255] The results are graphically shown in Fig. 2 for Comparative Example 2 and for Example 3. A comparison especially with regard to TOS, DNT conversion per g(cat.) and catalyst consumption (Ni U / R) is also shown below in Table 2.

[0256] It could be seen from Comparative Example 1 that without regeneration, the catalyst could only be used for a time on stream of up to 45 hours. After that, the catalyst becomes deactivated and the conversion into the desired product TDA decreases, while the generation of side products such as high boilers (HB) and intermediate products (ANT, not shown) increases significantly. Example 3 showed on the contrary that a, preferably repeatedly applied, regeneration treatment of the complete catalyst batch in the miniplant with hydrogen in presence of the hydrogenation bath consisting of TDA and water and temporary stop of DNT feed, enabled the catalyst to carry out the hydrogenation of DNT in an efficient manner for a sevenfold longer time span (315 hours) compared to Comparative Example 2. Furthermore, it could be seen that the catalyst’s consumption is reduced (i.e. improved) since per gram catalyst the threefold amount of DNT is converted into TDA in Example 3 compared to Comparative Example 2, i.e. the catalyst consumption could be reduced from 5.8 to 0.6 kg(cat.) / t(TDA).

[0257] Example 4: hydrogenation with regeneration at high TDA yield

[0258] (batch wise, miniplant)

[0259] A hydrogenation of DNT was carried out in a miniplant as described in general set-up 2 above, with repeatedly applied regeneration treatment of the complete catalyst batch as described in Example 3. In Example 4, however, the catalyst has been regenerated prior to the decline of the TDA yield (TDA yield of 99 %) for 3-15 hours every 2-5 days according to the regeneration treatment described in Example 3. Thereby, it was possible to maintain a TDA yield of at least 99% for a time on stream of at least 430 hours. After 430 hours time on stream the hydrogenation was stopped without reaching the catalyst’s end of lifetime

[0260] The results are graphically shown in Fig. 2 for Comparative Example 2 and for Examples 3 and 4. A comparison especially with regard to TOS, DNT conversion per g(cat.) and catalyst consumption (Ni U / R) is also shown below in Table 2.

[0261] Example 4 showed that a, preferably repeatedly applied, regeneration treatment of the complete catalyst batch in the miniplant with hydrogen, while maintaining a high TDA yield of 99%, and temporary stop of the DNT feed, enabled the catalyst to carry out the hydrogenation of DNT in an efficient manner for a tenfold longer time span (430 hours) compared to Comparative Example 2. Furthermore, it could be seen that the catalyst’s consumption is reduced (i.e. improved) since per gram catalyst the fourfold amount of DNT is converted into TDA in Example 4 compared to Comparative Example 2, i.e. the catalyst consumption could be reduced from 5.8 to 0.5 kg(cat.) / t(TDA).

[0262] Table 2

[0263] Hydrogenation with or without catalyst regeneration converted DNT in kg per g of catalyst catalyst consumption in kg of catalyst per ton of TDA produced

[0264] Example 5: hydrogenation with regeneration at high TDA yield and fresh catalyst dosage (batch wise, miniplant)

[0265] A hydrogenation of DNT was carried out in a miniplant as described in general set-up 2 above, with regeneration of the complete catalyst batch for 300 hours time on stream as described in Example 4. Then, fresh catalyst portions (5 g) were dosed into the hydrogenation bath either with or without additional regeneration of the complete catalyst batch as described in Example 3 until the intermediate product (ANT) has increased to 0.1 to 0.2 %. Then, the sequence of fresh catalyst dosage with or without regeneration was repeated and the DNT feed was stepwise increased to maintain a WHSV of 7 g(DNT) / g(cat.) / h. Thereby, it was possible to regain catalyst activity expressed as increase of the TDA yield to 99.7-99.8 %. After 680 hours time on stream the hydrogenation was stopped without reaching the catalyst’s end of lifetime.

[0266] The results are graphically shown in Fig. 3 and reported with regard to TOS, TDA yield before and after catalyst dosage and lifetime extension expressed by TOS until ANT breakthrough in Table 3.

[0267] Example 5 showed that a, preferably repeatedly, dosage of small portions of fresh catalyst either with or without catalyst regeneration can maintain a TDA yield of 99.7-99.8%. Moreover, the application of the additional regeneration, enabled the complete catalyst batch to carry out the hydrogenation of DNT in an efficient manner with a significantly increased time span of 75 hours time on stream compared to 45 hours time on stream without additional regeneration until a noticeable ANT breakthrough was observed.

[0268] Table 3

[0269] Hydrogenation and continuous catalyst dosage with or without catalyst regeneration

[0270] Peak TDA yield measured shortly after regeneration. increase of ANT until 0.1 -0.3 %.

[0271] Example 6: Fresh catalyst activation in a liquid mixture comprising TDA and water

[0272] An activation of a fresh catalyst comprising Ni and NiO (Ni to NiO ratio of 63% : 37%) was carried out in a 300 ml batch autoclave equipped with a bladed disc stirrer and baffle. The autoclave was charged with 5 g of fresh powdered catalyst and 20 ml of TDA and 180 ml of water. After leak test, the content of the autoclave was annealed to 90°C. Then, the gas phase was exchanged for H2 and the autoclave was pressurized with H2 to 25 bar. A concentration of hydrogen (H2) in the liquid aqueous mixture in the range of from 0.001 to 3 g / liter, especially in the range of from 0.04 to 0.15 g / liter, of liquid aqueous mixture was established. Immediately after reaching 25 bar, the stirrer was turned on (1300 rpm), which represented the start of the activation experiment (t = 0 min). Subsequently, the pressure decline, respectively, H2 consumption was recorded for 60 min, wherein it was found that the H2 consumption did not start immediately but was delayed for 4.2 min. After catalyst activation, diffraction peaks of NiO, determined by XRD, were absent. The results are graphically shown in Fig. 4 and summarized in Tab. 4.

[0273] Example 7: Fresh catalyst activation in a liquid mixture comprising TDA, water and additionally DNT The experiment was conducted as described in Example 6. However, the autoclave was filled with 180 ml of water, 20 ml of TDA and 100 weight-ppm DNT. H2 consumption, respectively, catalyst activation was delayed even further. Nevertheless, after catalyst activation, diffraction peaks of NiO, determined by XRD, were absent. The results are graphically shown in Fig. 4 and summarized in Tab. 4.

[0274] Table 4

[0275] Fresh catalyst activation

[0276] Integrated H2 consumption rate over the course of the catalyst activation (60 min)

[0277] Short description of the Figures

[0278] Fig. 1 shows the TDA and heavy boiler (HB) yield of Comparative Example 1 , Example 1 , and Example 2 versus time on stream ((Y(TDA), (Y(HB)). The percentage amount of TDA (Y(TDA)) is shown on the left ordinate, the percentage amount of HB (Y(HB)) is shown on the right ordinate, and the time on stream is shown on the abscissa.

[0279] Fig. 2 shows the TDA and heavy boiler (HB) yield of Comparative Example 2, Example 3, and Example 4 versus time on stream ((Y(TDA), (Y(HB)). The percentage amount of TDA (Y(TDA)) is shown on the left ordinate, the percentage amount of HB (Y(HB)) is shown on the right ordinate, and the time on stream is shown on the abscissa.

[0280] Fig. 3 shows the yields of TDA, ANT of Example 5 and therein the executed catalyst (batch) regenerations (Y(TDA), Y(ANT)). The percentage amount of TDA (Y(TDA)) is shown on the left ordinate, the percentage amount of ANT (Y(ANT)) is shown on the right ordinate, and the time on stream is shown on the abscissa.

[0281] Fig. 4 shows the integrated H2 consumption rate of Examples 6 and 7 over the course of the catalyst activation. The integrated H2 consumption rate in mmol per hour is shown on the ordinate, the time after H2 pressurization and start of stirring is shown on the abscissa.

[0282] Cited Literature

[0283] EP 2 686 294 B1

[0284] EP 2 598 241 B1

[0285] EP 2 838 875 B1

Claims

Claims1 . A combined process for hydrogenating a compound having at least one nitro group and for regenerating an at least partially spent hydrogenation catalyst, wherein the hydrogenation comprises(I) applying under hydrogenation conditions into a liquid aqueous mixture, which is present in a hydrogenation zone and which comprises a suspended hydrogenation catalyst and a compound having at least one nitro group (hydrogenation reactant), a hydrogen containing gas, thereby obtaining a liquid aqueous mixture comprising an at least partially spent suspended hydrogenation catalyst and a compound having at least one amino group (hydrogenation product);(II) removing at least a part of the liquid aqueous mixture obtained in (I) from the hydrogenation zone, which comprises at least partially spent suspended hydrogenation catalyst, compound having at least one amino group (hydrogenation product), and a compound comprising at least one nitro group in < 5000 weight-ppm; wherein the regeneration comprises(i) passing the at least part of the liquid aqueous mixture removed in (II) into a regeneration zone;(ii) establishing in the liquid aqueous mixture in the regeneration zone a hydrogen (H2) concentration CH2(2) in the range of from 0.001 to 3 g / liter of liquid aqueous mixture for at least 1 minute, thereby obtaining a liquid aqueous mixture comprising an at least partially regenerated hydrogenation catalyst in suspended form and the compound having at least one amino group.

2. The process of claim 1 , wherein the at least part of the liquid aqueous mixture removed in (II) and passed into the regeneration zone in (i) comprises less than 2500 weight-ppm, preferably less than 2100 weight-ppm, of a compound comprising at least one nitro group.

3. The process of claim 1 or 2, wherein the at least part of the liquid aqueous mixture removed in (II) and passed into the regeneration zone in (i) comprises in the range of from 20 to 90 weight-%, preferably in the range of from 30 to 85 weight-%, more preferably in the range of from 40 to 80 weight-%, more preferably in the range of from 50 to 70 weight- % of a compound comprising at least one amino group, which does not comprise a nitro group, based on the total weight of the liquid aqueous mixture being 100 weight-%.

4. The process of any one of claims 1 to 3, wherein in the range of from 95 to 100 weight-%, preferably in the range of from 98 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.5 to 100 weight-%, of the atleast part of the liquid aqueous mixture removed in (II) and passed into the regeneration zone in (i) consist of hydrogen, the at least partially spent hydrogenation catalyst, water and compound comprising at least one amino group, based on the total weight of the liquid aqueous mixture being 100 weight-%.

5. The process of any one of claims 1 to 4, wherein the at least part of the liquid aqueous mixture removed in (II) and passed into the regeneration zone in (i) additionally comprises one or more C1 to C6 mono alcohol.

6. The of any one of claims 1 to 5, wherein the at least part of the liquid aqueous mixture removed in (II) and passed into the regeneration zone in (i) comprises dissolved hydrogen (H2) at a concentration CH2(1 ) in the range of from 0.001 to 3 g per liter of liquid aqueous mixture; and wherein in (ii), establishing the H2 concentration CH2(2) is done by applying hydrogen containing gas onto the liquid aqueous mixture in said reaction zone at a pressure p in the range of from 0.1 to 200 bar, preferably in the range of from 0.1 to 100 bar, more preferably in the range of from 0.1 to 50 bar, more preferably in the range of from 15 to 40 bar, more preferably in the range of from 20 to 30 bar.

7. The process of any one of claims 1 to 6, wherein establishing the H2 concentration CH2(2) in (ii) is done at a temperature T in a reaction zone in the range of from 50 to 200 °C, preferably in the range of from 60 to 180 °C, more preferably in the range of from 70 to 150 °C.

8. The process of any claim 6 or 7, wherein the concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture according to (ii) in the reaction zone is established with simultaneously maintaining the concentration of the compound comprising at least one nitro group < 5000 weight-ppm.

9. The process of claims 1 to 8, wherein the compound having at least one nitro group is a reactant of a hydrogenation reaction and comprises preferably at least a compound selected from the group consisting of 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2-amino-4-nitro- toluene, 2-amino-6-nitrotoluene and mixtures of two or more thereof and the compound having at least one amino group, which does not comprise a nitro group, is a product of a hydrogenation reaction and comprises preferably at least a compound selected from the group consisting of 2,4-diaminotoluene, 2,6-diaminotoluene and a mixture of 2,4-dia- minotoluene and 2,6-diaminotoluene.

10. The process of claims 1 to 9, wherein the hydrogenation catalyst comprises at least one first metal selected from the group consisting of nickel, platinum and palladium, optionally in combination with at least one second metal selected from the group consisting of palladium, platinum, rhodium, iron, cobalt, zinc, chromium, vanadium, copper, silver, zirconium, titanium, hafnium, nickel, rhenium, ruthenium, and mixtures of two or more thereof, wherein the second metal is different from the first metal.

11. The process of claims 1 to 10, wherein the hydrogenation catalyst comprises a support which is preferably selected from the group consisting of activated carbon, carbon black, graphite, oxidic carrier component and mixtures of two or more thereof, wherein the oxidic carrier component is preferably selected from the group consisting of silicon dioxide, silicon carbide, kieselguhr, aluminum oxide, magnesium oxide, titanium dioxide, zirconium dioxide, hafnium dioxide and mixtures of two or more thereof, more preferably the oxidic carrier compound is selected from the group consisting of zirconium dioxide, silicon dioxide, hafnium dioxide and mixtures of two or more thereof, more preferably the oxidic carrier component comprises, more preferably is, zirconium dioxide and / or silicon dioxide.

12. The process of any one of claims 1 to 11, wherein (i) comprises(1.1) passing the at least part of the liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, the liquid aqueous mixture comprising dissolved hydrogen (H2) at a concentration CH2(1 ) removed in (II) into the regeneration zone;(1.2) adding fresh hydrogenation catalyst to the at least part of the liquid aqueous mixture provided in (i.1), thereby obtaining a liquid aqueous mixture comprising an at least partially spent hydrogenation catalyst and fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group, wherein the liquid aqueous mixture comprises dissolved hydrogen (H2) at a concentration CH2(1 ).

13. The process of claim 12, wherein (ii) is(ii’) establishing a concentration CH2(2) of hydrogen (H2) in the liquid aqueous mixture provided in (i.2); thereby obtaining a mixture comprising at least partially regenerated hydrogenation catalyst and activated fresh catalyst.

14. A method for activating a fresh hydrogenation catalyst, comprising(A) providing a liquid aqueous mixture comprising a fresh hydrogenation catalyst and having < 5000 weight-ppm of a compound comprising at least one nitro group;(B) applying a hydrogen containing gas onto the liquid aqueous mixture provided in (A) for at least 1 minute; thereby obtaining an activated hydrogenation catalyst.

15. An at least partially regenerated hydrogenation catalyst, obtained or obtainable from the process of any one of claims 1 to 13 having a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of > 98 % based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, having an overall surface area in the range of from 1 to 1200 m2 / g, preferably in the range of from 10 to 800 m2 / g, more preferably in the range of from 20 to 500 m2 / g, more preferably in the range of from 30 to 250 m2 / g, more preferably in the range of from 40 to 200 m2 / g, more preferably in the range of from 50 to 150 m2 / g, more preferably in the range of from 80 to 120 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131 ; and / or, preferably and, comprising at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD; and / or, preferably and, comprising less than 5 weight-% of carbon and / or, preferably and, less than 2 weight-% of nitrogen, determined by elemental analysis, based on the total weight of the activated hydrogenation catalyst being 100 weight-%; and / or, preferably and, having a pore volume in the range of from0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, more preferably in the range of from 0.4 to 1.4 ml / g, more preferably in the range of from 0.8 to 1.0 ml / g, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133; and / or, preferably and, having a pore diameter 0.1 to 1000 nm, preferably in the range of from 10 to 500 nm, more preferably in the range of from 20 to 250 nm, more preferably in the range of from 30 to 150 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

16. An activated hydrogenation catalyst, obtained or obtainable from the process of any one of claims 12 to 13 or 14 ; having a normalized H2 consumption when used under hydrogenation conditions for hydrogenation of a compound having at least one nitro group (hydrogenation reactant) of in the range of from 98 to 100 %, based on 100 % being the maximum normalized H2 consumption; and / or, preferably and, having an overall surface area in the range of from <1200 m2 / g, preferably < 800 m2 / g, more preferably < 500 m2 / g, more preferably< 250 m2 / g, more preferably < 200 m2 / g, more preferably< 120 m2 / g, more preferably <60 m2 / g, determined by the BET method via nitrogen physisorption at 77 K according to the method disclosed in DIN 66131 ; and / or, preferably and, comprising at least a part of the first metal in oxidation state 0 and optionally a further part of the of the first metal in an oxidation state > 0 in the form of an oxide of the first metal, wherein the ratio of first metal in oxidation state 0 to metal oxide of first metal is in the range of from 95-100 : 0-5, determined by XRD; and / or, preferably and, comprising < 25 weight-%, preferably < 10 weight-%, more preferably < 5 weight-% of carbon and < 6 weight-%, preferably < 3 weight-%, more preferably < 1 weight-%, of nitrogen, each determined based on elemental analysis, based on the total weight of the at least partially regenerated hydrogenation catalyst being 100 weight-%; and / or, preferably and, having a pore volume in the range of from 0.1 to 2.0 ml / g, preferably in the range of from 0.2 to 1.8 ml / g, preferably <1.4 ml / g, more preferably <1.0 ml / g, more preferably<0.8 ml / g, more preferably <0.6 ml / g, determined by Hg porosimetry, wherein Hg porosim- etry is determined in particular according to DIN 66133; and / or, preferably and, having a pore diameter < 800 nm, preferably < 250 nm, more preferably < 150 nm, more preferably < 100 nm, determined by Hg porosimetry, wherein Hg porosimetry is determined in particular according to DIN 66133.

17. Use of the at least partially regenerated and / or activated hydrogenation catalyst of claim 15 or 16 as a hydrogenation catalyst, preferably for the hydrogenation of a compound having at least one nitro group.

18. A reaction system for combined hydrogenation of a compound having at least one nitro group and regeneration of an at least partially spent hydrogenation catalyst comprising: (a) a hydrogenation vessel having(a.1) means for feeding gaseous and liquid materials into the hydrogenation vessel;(a.2) means for intermixing in the hydrogenation vessel,(a.3) an outlet for removing a liquid aqueous mixture from the hydrogenation vessel;(a.4) at least one inlet for reintroduction of a liquid aqueous mixture;(a.5) circuit lines outside of the hydrogenation vessel in fluid connection to the outlet (a.3) and inlet (a.4), which enable withdrawal of a liquid aqueous mixture from the hydrogenation vessel via outlet (a.3) and reintroduction of the liquid aqueous mixture into the hydrogenation vessel via the inlet (a.4);(a.6) optionally means for introducing fresh catalyst;(b) a regeneration vessel comprising(b.1) at least one inlet (b.1.1) for feeding a liquid aqueous mixture into the regeneration vessel,(b.2) at least one outlet (b.1 .2) for removing a liquid aqueous mixture from the regeneration vessel;(b.3) means for intermixing in the regeneration vessel;(b.4) means for feeding hydrogen gas into the regeneration vessel;(b.5) optionally means for introducing fresh catalyst; and(c.a) lines in fluid connection with at least one further outlet (a.7) of the hydrogenation vessel of (a) and the at least one inlet (b.1.1) of the regeneration vessel of (b) and lines in fluid communication of the at least one outlet (b.1 .2) of the regeneration vessel (b) and at least one further inlet (a.8) of the of the hydrogenation vessel of (a); or(c.b) lines in fluid connection with at least one outlet (a.

5. out) of the circuit lines (a.5) and the at least one inlet (b.1.1) of the regeneration vessel (b) and lines in fluid communication of the at least one outlet (b.1.2) of the regeneration vessel (b) and at least one further inlet (a.

5. in) of the of the circuit lines (a.5); wherein all lines are built and arranged to allow transfer of a liquid aqueous mixture from an outlet to the respective inlet.

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