Heterogeneous catalysts for the direct carbonylation of nitro aromatic compounds to isocyanates

Abstract

A process for preparing an aromatic isocyanate by direct carbonylation of a nitro aromatic compound by reacting the nitro aromatic compound with carbon monoxide in the presence of a catalyst, characterized in that the catalyst contains a multi metallic material comprising one or more binary intermetallic phases of the general formula A.sub.xB.sub.y wherein: A is one or more element selected from Ni, Ru, Rh, Pd, Ir, Pt and Ag, B is one or more element selected from Sn, Sb, Pb, Zn, Ga, In, Ge and As, x is in the range 0.1-10, y in is in the range 0.1-10.

Claims

1. A process for preparing an aromatic isocyanate by direct carbonylation of a nitro aromatic compound, the process comprising reacting the nitro aromatic compound with carbon monoxide in the presence of a catalyst, wherein the catalyst contains a multi metallic material comprising one or more binary intermetallic phases of formula A.sub.xB.sub.y, where: A is at least one element selected from the group consisting of Ni, Ru, Rh, Pd, Ir, Pt and Ag, B is at least one element selected from the group consisting of Sn, Sb, Pb, Zn, Ga, In, Ge and As, x is in the range of 0.1 to 10, and y is in the range of 0.1 to 10.

2. The process according to claim 1, wherein A is at least one element selected from the group consisting of Ni, Rh, Pd, Ir and Pt, and B is at least one element selected from the group consisting of Sn, Sb, Pb, Ga and In.

3. The process according to claim 2, wherein A is Rh, and B is at least one element selected from the group consisting of Pb, Sn and Sb.

4. The process according to claim 1, wherein the multi metallic material comprises at least one component C, which contains or consists of A or B not being part of the intermetallic phase A.sub.xB.sub.y.

5. The process according to claim 1, wherein the multi metallic material comprises at least one component C, which contains or consists of one or more elements selected from the group consisting of O, N, C, H, Mg, Ca, Mn, Fe, Co, Ni, Zn, and Ga.

6. The process according to claim 1, wherein the multi metallic material is deposited on a carrier material.

7. The process according to claim 1, wherein the nitroaromatic compound is selected from the group consisting of nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene, trinitrotoluene, nitronaphthalene, nitroanthracene, nitrodiphenyl, and bis(nitrophenyl)methane.

8. The process according to claim 1, which is carried out discontinuously.

9. The process according to claim 1, which is carried out continuously.

Description

EXAMPLES

(1) FIG. 1 shows the catalytic results for example catalysts H, I, J according to Table 2.

(2) FIG. 2 shows the PXRD pattern of sample J α: Reflexes of RhPb.sub.2. β: Reflex of graphite.

(3) FIG. 3 shows the catalytic results for example catalysts K to O, according to Table 3.

(4) For X-Ray powder diffraction (XRPD) data were collected on a Bruker AXS D8 Advance. Cu Kα radiation was used in the data collection. The beam was narrowed using a collimator for line focus (Soller Slit, 2.5°) and a motorized divergence slit. Generator settings of 40 kV and 40 mA were used. Samples were gently ground in a mortar with a pestle and then packed in a round mount. The data collection from the round mount covered a 2θ range from 5° to 70° using a step scan with a step size of 0.02° and a count time of 0.2 s per step. DIFFRAC.EVA Software was used for all steps of the data analysis. The phases present in each sample were identified by search and match of the data available from International Centre for Diffraction Data (ICDD, Version 2015).

(5) Batch Reactor Testing:

(6) Screening in batch reactor was carried out in a series of single experiments, using batch autoclaves made from hastelloy C276. The general experimental procedure for each screening experiment was as follows:

(7) In a first step a reaction mixture was prepared by dissolving nitrobenzene in chlorobenzene. The concentration of nitrobenzene in the reaction mixture was set to be between 1 wt % and 5 wt %. The respective amount of catalyst was placed into the empty reactor and heated to 160° C. and 10.sup.−1 bar for at least 12 h. In a second step the reaction mixture was charged into the reactor without lowering the temperature or opening the reactor using a specialized charging device. After charging the reaction mixture, the autoclave was heated or cooled to the desired temperature. In a final step the autoclave was pressurized with CO gas and nitrogen gas to the desired total pressure. The reaction mixture was stirred with 1000 rpm for the respective time.

(8) The respective product spectrum was analyzed via a GC-MS unit (GC-MS from Agilent Technologies) equipped with FID, MS and TCD detectors. The total conversion of the reaction was calculated as the difference in starting and end concentration of the nitroaromatic compound divided by the starting concentration of the nitroaromatic compound. The concentration of the respective products in the reaction mixture was identified by GC analytic by using the respective response factors. The yield was determined by dividing the respective product concentration (in mmol/kg) by the starting concentration of the nitroaromatic compound (in mmol/kg) and multiplying the resulting value by the mol(s) of starting nitroaromatic compound needed to generate a mol of the respective product.

(9) The difference between the combined yields of all products and the total calculated conversion is represented by the term “polymer”. “Polymer” comprises the products formed which could not be analyzed by the applied GC-method.

Comparative Examples A to C

(10) Synthesis of Oxides According to DE 1 810 828

(11) Synthesis of Pb.sub.0.3Mn.sub.0.7O.sub.z

(12) For the preparation of the samples with a Mn:Pb ratio of 0.7:0.3, 0.1752 mol Mn as Mn(NO.sub.3).sub.2x6H.sub.2O and 0.075 mol Pb as Pb(NO.sub.3).sub.2 were dissolved in 1 L of DI water under stirring. After the nitrates were dissolved, DI water was added up to 2.5 L. 1.04 mol activated carbon was added to the solution. The pH was adjusted to 10 by adding 8 wt % of a NaOH solution. The product precipitated, and the suspension was stirred for 30 minutes for aging.

(13) The liquid was separated from the solids by decantation. DI water was added to the solids and stirred for 15 minutes. The procedure was repeated until the pH value was identical to the used DI water. The solids were separated by filtration and dried at 100° C. overnight.

(14) Synthesis of Fe.sub.xMn.sub.yO.sub.z

(15) For the preparation of the MnFe samples with a Mn:Fe ratio of 0.8:0.2, the above described recipe was applied except the sources for Mn and Fe were not nitrates but chlorides (0.2 mol Mn as MnCl.sub.2x4H.sub.2O and 0.05 mol Fe as FeCl.sub.3x6H.sub.2O).

(16) 1:1 physical mixtures of oxides with 5 wt % Rh or Pd impregnated on activated carbon were prepared according to GB1315813 A and catalytically tested. Table 2 shows the results of the reduction of nitrobenzene and insertion of CO into nitrosobenzene for the mixtures of (A) 5 wt % Pd on C and Pb.sub.0.3Mn.sub.0.7O.sub.x, (B) 5 wt % Rh on C and Pb.sub.0.3Mn.sub.0.7O.sub.x and (C) 5 wt % Rh on C and Fe.sub.0.2Mn.sub.0.8O.sub.x. Reaction conditions were p=100 barg, T=190° C. and 6 h reaction time. The physical mixture of (A) 5 wt. % Pd@C and Pb.sub.xMn.sub.yO.sub.z yielded no phenyl isocyanate at all, but the formation of nitrosobenzene, azo- and azoxybenzene was observed. However, the other two tested systems, (B) 5 wt % Rh@C and Pb.sub.xMn.sub.yO.sub.z and (C) 5 wt % Rh@C and Fe.sub.xMn.sub.yO.sub.z, yielded the formation of Phenyl isocyanate, azo- and azoxybenzene as well as “polymer”.

Comparative Examples D to G

(17) The preparation of the comparative examples D to G was done by preparing single metal solutions as described in step (i) and impregnating the solutions on an activated carbon support as described in step (ii). The impregnation technique that was followed was incipient wetness impregnation. A drying Step (iia) at 80° C. was performed after the impregnation. The amount of metal deposited on the support was 5 wt % of the support mass. The respective metal containing components and solvents can be taken from Table 1.

(18) TABLE-US-00001 TABLE 1 Metal Metal containing component Solvent Rh Rh(NO.sub.3).sub.3 H.sub.2O Pb Pb(NO.sub.3).sub.3 H.sub.2O Sb Sb(CH.sub.3COO).sub.3 Tataric acid (4M) Sn SnC.sub.2O.sub.4 Nitric acid (35%) Pd Pd(NO.sub.3).sub.2 Nitric acid (35%) In In(NO.sub.3).sub.3 H.sub.2O Ni Ni(NO.sub.3).sub.2 H.sub.2O Ga Ga(NO.sub.3).sub.3 H.sub.2O

Catalytic Results of Example A to G

(19) Comparative examples A to G were catalytically tested. Table 2 shows the yields of the reduction of nitrobenzene (step 1) and the insertion of CO into nitrosobenzene to form phenyl isocyanate (step 2). For the mixtures of (A) 5 wt % Pd@C and Pb.sub.0.3Mn.sub.0.7O.sub.x, (B) 5 wt % Rh@C and Pb.sub.0.3Mn.sub.0.7O.sub.x and (C) 5 wt % Rh@C and Fe.sub.0.2Mn.sub.0.8O.sub.x the reaction conditions were p=100 barg, T=190° C. and 6 h reaction time. The physical mixture of (A) 5 wt. % Pd@C and Pb.sub.xMn.sub.yO.sub.z yielded no phenyl isocyanate at all, but the formation of nitrosobenzene, azo- and azoxybenzene was observed. However, the other two tested systems, (B) 5 wt % Rh@C and Pb.sub.xMn.sub.yO.sub.z and (C) 5 wt % Rh@C and Fe.sub.xMn.sub.yO.sub.z, yielded the formation of Phenyl isocyanate, azo- and azoxybenzene as well as “polymer”.

(20) For the single metal catalysts D to G, the reaction conditions were p=100 barg, T=160° C. and 4 h reaction time. No single metal catalysts yield any phenylisocyanate.

(21) TABLE-US-00002 TABLE 2 Results of the comparative examples. PI AZO AZY NSB DCD POL No. Composition [%] [%] [%] [%] [%] [%] A Pd@C + Pb.sub.0.3Mn.sub.0.7O.sub.x 0 1.79 20.16 1.50 0 0 B Rh@C + Pb.sub.0.3Mn.sub.0.7O.sub.x 0.34 5.92 0.42 0 0 9.88 C Rh@C + Fe.sub.0.2Mn.sub.0.8O.sub.x 3.69 0.92 0.31 0 0 4.58 D 5 wt % Rh@C 0 0 0 0 0 0 E 5 wt % Pb@C 0 0 0.12 0 0 0.3 F 5 wt % Sb@C 0 0 0 0 0 0 G 5 wt % Sn@C 0 0 0 0 0 0 PI = Phenylisocyanate; AZO = Azobenzene; AZY = Azoxybenzene; NSB = Nitrosobenzene; DCD = Diphenylcarbodiamide; POL = Polymer

(22) The results of comparative examples B and C indicate that both steps of the reaction occurred in a one pot synthesis by combining the functionalities of two catalysts, the oxide responsible for step 1 of the reaction and the base metal responsible for step 2 of the reaction.

(23) H to O

(24) The preparation of the patent examples H to J was done by preparing two separate single metal solutions as described step (i). After that a mixture was prepared from these solutions. The concentration of the single solutions and the respective volume used to prepare the mixture is shown in Table 3. The mixture was impregnated on an activated carbon support as described in step (ii). The impregnation technique that was followed was incipient wetness impregnation and a drying Step (iia) was performed at 80° C. after each impregnation step.

(25) The amount of metal A deposited on the support was aimed to be 5 wt % of the supports mass. The amount of metal B was calculated according to the sum formula. After the drying step the composite materials of patent examples H to J received a combined reductive & thermal treatment for 5 h at 500° C. (steps iii & iv) using a muffle furnace and N.sub.2 atmosphere. The respective support masses, concentrations and volumes can be taken from Table 3. The metal containing components and solvents can be taken from Table 1.

(26) The preparation of the patent examples K to O was done by preparing single metal solutions as described in step (i) and impregnating the solutions consecutively on an oxidic support as described in step (ii). The impregnation technique that was followed was incipient wetness impregnation. For the examples K, L and M the single metal solution containing metal A was impregnated first. For the examples N and O the single metal solution containing metal B was impregnated first. In case of example N and O multiple impregnations for every solution were needed (see Table 3 for details). A drying Step (iia) was performed at 80° C. after each impregnation step. The amount of metal A deposited on the support was aimed to be 5 wt % of the support mass. The amount of metal B was calculated according to the sum formula. After the final drying step, the composite material was suspended in polyethylene glycol (polyol) and received a reductive treatment as described in step (iii). The reduction was done for 20 minutes at 200° C. using a 1000 W microwave oven and N.sub.2 atmosphere. The reduced composite material was separated from the polyol and received a thermal treatment as described in step (iv) for 5 h at 500° C. using a muffle furnace and N.sub.2 atmosphere.

(27) The respective support masses, concentrations and volumes can be taken from Table 3. The metal containing components and solvents can be taken from Table 1.

(28) TABLE-US-00003 TABLE 3 No. Composition A.sub.xB.sub.y 1 2 3 4 5 6 7 8 9 H Rh.sub.2Sn C 2.5 1.16 1.07 1 1 6.32 1 a I RhSb C 2.5 1.16 1.11 1 1 1.29 1 a J RhPb.sub.2 C 2.5 1.16 1.32 1 1 3.04 1 a K RhPb Al.sub.2O.sub.3*.sup.) 3 1.15 1.41 1 1 1.62 1 b L RhPb.sub.2 Al.sub.2O.sub.3*.sup.) 3 1.15 1.59 1 1 3.65 1 b M RhPb.sub.2 Al.sub.2O.sub.3**.sup.) 3 1.15 1.59 1 1 3.65 1 b N RhPb.sub.2 Mn.sub.2O.sub.3 33.5 1.148 17.75 3 1.5 27.17 5 b O RhSb TiO.sub.2***.sup.) 2.5 1.16 1.11 2 1 1.30 2 b 1: Support material. *.sup.)specific surface area: 100 m.sup.2 **.sup.)specific surface area: 5 m.sup.2 ***.sup.)Rutile 2: Amount of support material [g]. 3: Concentration of solution containing metal A [mol/L]. 4: Total volume of solution containing metal A used for impregnation [ml]. 5: Number of impregnation steps for solution containing metal A. 6: Concentration of solution containing metal B [mol/L]. 7: Total volume of solution containing metal B used for impregnation [ml]. 8: Number of impregnation steps for solution containing metal B. 9: Heating Method. a Muffle Furnace 500° C.; 5 h; N.sub.2 atmosphere. b Microwave oven (1000 W) 200° C.; 20 minutes; N.sub.2 atmosphere

Catalytic Results of Examples H to O

(29) Table 4 and FIG. 1 show the results of the reduction of nitrobenzene and insertion of CO in nitrosobenzene. Reaction conditions were p=100 barg, T=160° C. and 4 h reaction time.

(30) TABLE-US-00004 TABLE 4 Results of examples H to O PI AZO AZY NSB DCD POL No. Composition [%] [%] [%] [%] [%] [%] H Rh.sub.2Sn@C 2.45 0.40 0 0 0 0.95 I RhSb@C 14.27 0.89 1.87 0 0.30 18.43 J RhPb.sub.2@C 26.57 3.21 5.08 0 2.55 20.29 K RhPb@Al.sub.2O.sub.3 3.60 1.98 0.34 0 0 4.68 L RhPb.sub.2@Al.sub.2O.sub.3 4.50 2.60 1.69 0 0 6.09 M RhPb.sub.2@Al.sub.2O.sub.3 2.46 0.14 0.35 0 0 2.24 N RhPb.sub.2@Mn.sub.2O.sub.3 4.07 1.75 0.39 0 0 4.22 O RhSb@TiO.sub.2 2.26 0 0 0 0 1.18

(31) The results show that—contrary to the single metal catalysts—the multi metallic catalysts yielded phenyl isocyanate as a product.

(32) FIG. 2 shows the PXRD pattern of sample J, proving that the multimetallic catalyst consists of the intermetallic compound RhPb.sub.2 (α) on an amorphous carbon support. However, some traces of graphite (β) coming from the carbon support have been identified, too. In addition, the reflexes of graphite appeared as a consequence of the thermal treatment step.

(33) Testing in a Continuous Reactor:

(34) Screening in a continuous reactor was carried out in a series of experiments, using a trickle bed reactor system. The general experimental procedure for each screening experiment was as follows:

(35) In a first step a reaction mixture was prepared by dissolving nitrobenzene or dinitrotoluene in chlorobenzene. The concentration of the respective nitroaromatic compound in the reaction mixture was set to be between 1 wt % and 3 wt %.

(36) The reactor used were a tube reactor with a length of 40 cm an inner diameter of 0.4 cm. Inside the reactor 1 ml of the respective catalyst sieved to a fraction size of 125-160 μm was loaded. SiO.sub.2 was used as pre- and post-bed inert material.

(37) The reactor was heated to 160° C. in N.sub.2 atmosphere for at least 12 h to remove residual water. After that the reactor temperature was set to the desired value.

(38) In a following step the reaction mixture was mixed with CO or a mixture of CO & N.sub.2 and fed to the reactor. The Liquid flow (LHSV) was set to be between 1 h.sup.−1 and 4 h.sup.−1. While the Gas flow (GHSV) was set to be between 500 & 3500 h.sup.−1.

(39) The obtained product mixture was collected over time and analyzed by GC.

(40) All experimental details are summarized in Table 6.

(41) The respective product spectrum was analyzed via a GC-MS unit (GC-MS from Agilent Technologies) equipped with FID, MS and TCD detectors. The total conversion of each reaction was calculated as difference of the reactor inlet (feed) concentration of the nitro aromatic compound and the concentration of the nitroaromatic compound in the product mixture divided by the starting concentration of the nitroaromatic compound. The concentration of the respective products in the product mixture was identified by GC analytic by using the respective response factors. The yield was determined by dividing the respective product concentration (in mmol/kg) by the concentration of the nitroaromatic compound (in mmol/kg) and multiplying the resulting value by the mol(s) of starting nitroaromatic compound needed to generate a mol of the respective product.

(42) The difference between the combined yields of all products and the total calculated conversion of the nitroaromatic compounds is represented by the term “polymer”. “Polymer” comprises the products formed which could not be analyzed by the applied GC-method.

(43) The preparation of the patent examples H to BI was done by preparing separate single metal solutions as described step (i). After that a mixture was prepared from these solutions. The concentration of the single solutions and the respective volume used to prepare the mixture is shown in Table 5. The mixture was impregnated on various supports as described in step (ii). The impregnation technique that was followed was incipient wetness impregnation and a drying Step (iia) was performed at 80° C. after each impregnation step.

(44) In some examples the support was prepared from mixture of two oxides. In this case the oxides have been mixed physically using a hand mill. The obtained oxidic mixture was calcined at 500° C. prior to the impregnation.

(45) The amount of metal A deposited on the support was aimed to be between 1 and 5 wt % of the supports mass. The amount of metal B was calculated according to the sum formula. After the drying step the composite materials of patent examples H to BI received a reductive & thermal treatment for 5 h at 500° C. (steps iii & iv) using a muffle furnace and N.sub.2 atmosphere. The respective support masses, concentrations and volumes can be taken from Table 5. The metal containing components and solvents can be taken from Table 1.

(46) TABLE-US-00005 TABLE 5 Composition No. A.sub.xB.sub.y 1 2 3 4 5 6 7 8 9 H Rh2Sn C 2.5 0 1.16 1.07 1 1 6.32 1 I RhSb C 2.5 0 1.16 1.11 1 1 1.29 1 J RhPb.sub.2 C 2.5 0 1.16 1.32 1 1 3.04 1 O RhSb TiO.sub.2**) 2.5 0 1.16 1.11 2 1 1.30 2 P Rh.sub.2Sn TiO.sub.2**) 2.5 0 1.16 1.07 2 1 6.32 2 Q RhGa TiO.sub.2**) 8 0 1.15 3.38 2 2 1.94 2 R RhIn TiO.sub.2**) 8 0 1.15 3.38 3 1 3.89 3 S Pd.sub.5Sb.sub.2 TiO.sub.2**) 5 0 3.63 0.65 1 1 0.94 1 T Pd.sub.8Sb.sub.3 TiO.sub.2**) 5 0 3.63 0.65 1 1 0.88 1 U PdPb.sub.2 TiO.sub.2**) 5 0 3.41 0.69 1 1.5 3.13 2 V RhSb TiO.sub.2**) 21.2 0 1.16 1.78 1 1 2.05 1 W RhSb TiO.sub.2**) + 5% ZnO 3.8 0.2 1 0.39 1 1 0.33 1 X RhSb TiO.sub.2**) + 10% ZnO 10.5 1.17 1 1.14 1 1 1.14 1 Y RhSb TiO.sub.2**) + 20% ZnO 3.2 0.8 1 0.39 1 1 0.33 1 Z RhSb TiO.sub.2**) + 30% ZnO 2.8 1.2 1 0.39 1 1 0.33 1 AA RhSb TiO.sub.2**) + 40% ZnO 2.4 1.6 1 0.39 1 1 0.33 1 AB RhSb TiO.sub.2**) + 50% ZnO 1.75 1.75 1 0.34 1 1 0.29 1 AD RhSb TiO.sub.2**) + 67% ZnO 0.85 1.65 1 0.24 1 1 0.21 1 AE RhSb ZnO 0 10 1 0.97 1 1 0.97 1 AF RhSb TiO.sub.2*) + 10% CaO 3.51 0.39 1.13 0.33 1 1 0.38 1 AG RhSb TiO.sub.2**) + 10% CaO 6.08 0.68 1.13 0.58 1 1 0.65 1 AH RhSb TiO.sub.2*) + 10% MgO 3.89 0.43 1.13 0.37 1 1 0.42 1 AI RhSb TiO.sub.2**) + 10% MgO 5.04 0.56 1.13 0.48 1 1 0.54 1 AJ RhSb TiO.sub.2*) + 10% V.sub.2O.sub.5 5.54 0.62 1.13 0.53 1 1 0.6 1 AK RhSb Mn.sub.2O.sub.3 0 12.2 1.13 1.05 1 1 1.19 1 AL RhSb Mn.sub.2O.sub.3 + 10% CaO 5.49 0.61 1.13 0.52 1 1 0.59 1 AM RhSb Mn.sub.2O.sub.3 + 45% Fe.sub.2O.sub.3 7.55 6.17 1.13 1.19 1 1 1.35 1 AN RhSb Mn.sub.2O.sub.3 + 35% Fe.sub.2O.sub.3 8.99 4.84 1.13 1.19 1 1 1.34 1 AO RhSb Mn.sub.2O.sub.3 + 25% Fe.sub.2O.sub.3 10.4 3.48 1.13 1.19 1 1 1.35 1 AP RhSb Mn.sub.2O.sub.3 + 10% MgO 5.03 0.56 1.13 0.48 1 1 0.54 1 AQ RhSb Mn.sub.2O.sub.3 + 30% PbO 12.3 5.28 1.13 1.51 1 1 1.71 1 AR RhSb Mn.sub.2O.sub.3 + 10% ZnO 6.44 0.72 1.13 0.61 1 1 0.69 1 AS RhSb MoO.sub.3 7.54 0 1.13 0.65 2 1 0.73 2 AT RhSb MoO.sub.3 + 10% CaO 5.49 0.61 1.13 0.52 1 1 0.59 1 AU RhSb MoO.sub.3 + 10% MgO 6.80 0.76 1.13 0.65 1 1 0.73 1 AV RhSb MoO.sub.3 + 10% ZnO 7.25 0.81 1.13 0.69 1 1 0.78 1 AW RhSb C 3.52 0 1.16 0.29 1 1 0.34 1 AX RhSb Elorit 2 0 1.15 0.89 1 1 1.03 1 AY RhSb Bi.sub.2O.sub.3 18.2 0 1.13 1.56 2 1 1.77 2 AZ RhSb CaO 10.0 0 1 0.97 1 1 0.97 1 BA RhSb Co.sub.2O.sub.3 14.6 0 1.13 1.26 2 1 1.42 2 BB RhSb Cr.sub.2O.sub.3 8.58 0 1.13 0.74 1 1 0.83 1 BC RhSb Fe.sub.2O.sub.3 7.17 0 1.13 0.62 1 1 0.69 1 BD RhSb Fe.sub.3O.sub.4 7.39 0 1.13 0.63 1 1 0.71 1 BE RhSb V.sub.2O.sub.5 5.7 0 1.13 0.49 2 1 0.55 2 BF RhSb WO.sub.3 12.6 0 1.13 1.09 1 1 1.23 1 BG RhSb ZrO.sub.2 1 0 1.13 0.09 1 1 0.1 1 BH RhSb ZrO.sub.2 1 0 1.13 0.09 1 1 0.1 1 BI RhSb ZrWO.sub.x 5.79 0 1.13 0.5 1 1 0.56 1 1: Support material. *)specific surface area: >5 m.sup.2 **)Rutile 2: Amount of support material I [g]. 3: Amount of support material II [g]. 4: Concentration of solution containing metal A [mol/L]. 5: Total volume of solution containing metal A used for impregnation [ml]. 6: Number of impregnation steps for solution containing metal A. 7: Concentration of solution containing metal B [mol/L]. 8: Total volume of solution containing metal B used for impregnation [ml]. 9: Number of impregnation steps for solution containing metal B.

(47) TABLE-US-00006 TABLE 6 Overview about experimental parameters. # 1a 2a 3a 4a 5a 6a 7a 8a a NB 1 160 100 100 0 4 2000 b NB 1 120 100 100 0 4 2000 c NB 1 80 100 100 0 4 2000 d 2,4-DNT 1 60 100 100 0 4 2000 e 2,4-DNT 1 80 100 100 0 4 2000 f 2,4-DNT 1 100 100 100 0 4 2000 g 2,4-DNT 1 120 100 100 0 4 2000 h 2,4-DNT 1 80 100 100 0 1 2000 i 2,4-DNT 1 80 100 100 0 4 500 i 2,4-DNT 1 80 100 100 0 1 500 k 2,4-DNT 1 120 100 100 0 1 2000 l 2,4-DNT 1 120 100 100 0 4 500 m 2,4-DNT 1 120 100 100 0 1 500 n 2,4-DNT 1 130 100 100 0 4 2000 o 2,4-DNT 1 140 100 100 0 4 2000 p 2,4-DNT 1 120 100 100 0 1 2750 q 2,4-DNT 1 120 100 100 0 1 3500 r 2,4-DNT 1 140 100 100 0 3 2000 s 2,4-DNT 1 140 100 100 0 2 2000 t 2,4-DNT 1 140 100 100 0 1 2000 v 2,4 DNT & 3 140 50 100 0 1 2000 2,6 DNT 1a: Feed stock NB Nitrobenzene 2,4-DNT 2,4-Dinitrotoluene 2,4-DNT & 2,6-DNT Mixture of 20 wt % 2,6-DNT & 80 wt % 2,4-DNT 2a: Feed concentration [wt %] 3a: Temperature [° C.] 4a: Total Pressure [bar] 5a: Concentration of CO [vol %] 6a: Concentration of N2 [vol %] 7a: LHSV (Liquid hourly space velocity) [h.sup.−1] 8a: GHSV (Gas hourly space velocity) [h.sup.−1]

(48) TABLE-US-00007 TABLE 7 Results of catalytic tests in trickle bed set up with nitro benzene: PI AZO AZY NSB DCD POL No. # [%] [%] [%] [%] [%] [%] I a 32.01 1.71 0.00 0 1.09 65.20 J a 1.67 1.69 18.78 0 0.03 58.53 O a 49.07 2.31 0.00 0 4.10 44.53 H b 7.54 0.30 0.48 0 0.01 10.43 O b 72.20 2.32 1.73 0 1.02 18.96 H c 0.79 0.03 0.09 0 0 2.77 O c 9.93 0.73 0.51 0 0 5.31 PI = Phenyl isocyanate; AZO = Azobenzene; AZY = Azoxybenzene; NSB = Nitrosobenzene; DCD = Diphenylcarbodiamide; POL = Polymer. X = Total conversion.

(49) The results show, that isocyantes can be produced from nitro aromatic compounds in a continuous process.

(50) TABLE-US-00008 TABLE 8 Results of catalytic tests in trickle bed set up with DNT Feed stock: TDI TNI AZOC AZYC NSC AC POL No # [%] [%] [%] [%] [%] [%] [%] O d 0.05 11.43 2.01 2.75 0.06 1.01 1.43 O e 0.15 16.65 1.57 2.74 0.15 0.97 1.25 O f 0.89 33.85 1.54 3.60 0.39 1.08 3.10 O g 3.31 55.68 0.99 2.59 0.69 1.05 1.15 O h 0.48 25.22 1.03 1.55 0.19 1.01 1.62 O i 0.00 4.88 0.83 0.32 0.20 0.81 2.79 O j 0.04 6.17 0.81 0.43 0.18 0.84 6.82 O k 35.57 48.82 0.27 0.98 0.41 0.16 10.67 O l 2.73 48.11 0.80 2.03 0.76 1.02 1.23 O m 4.28 48.85 0.76 1.95 0.68 0.93 1.23 O n 5.02 56.79 0.70 2.12 0.78 0.89 8.99 O o 12.90 71.06 0.48 2.09 0.98 0.74 1.20 O p 14.16 70.82 0.40 1.58 0.54 0.68 3.60 O q 14.55 72.89 0.42 1.66 0.55 0.76 1.45 O r 0.00 2.29 0.65 0.36 0.32 0.74 3.51 O s 19.26 69.01 0.28 1.35 0.72 0.69 3.99 O t 47.52 36.47 0.19 0.71 0.36 0.20 14.68 P d 0.04 5.87 0.95 1.28 0.00 1.73 1.26 P e 0.04 5.03 1.40 1.14 0.31 1.44 2.17 P f 0.11 8.75 1.81 1.53 0.89 1.53 5.71 P g 0.12 7.44 1.50 0.66 1.34 1.48 5.15 P h 0.00 1.09 1.40 0.31 0.48 1.43 4.02 P i 0.00 0.14 0.77 0.00 0.14 0.80 1.59 P j 0.00 0.31 0.94 0.09 0.21 1.01 5.70 P k 0.40 9.74 1.48 1.55 1.75 2.54 17.54 P l 0.00 2.35 1.06 0.21 1.00 1.12 4.34 P m 0.08 4.41 1.21 0.44 1.27 1.34 5.76 P n 0.08 4.54 1.21 0.49 1.53 1.31 18.32 P o 0.15 7.65 1.54 0.75 2.13 1.60 7.80 P p 0.15 4.70 2.81 0.77 1.24 3.69 11.38 P q 0.14 4.29 3.02 0.83 1.08 4.01 12.78 P r 0.00 0.04 0.60 0.00 0.00 0.76 2.17 P s 0.16 5.42 1.87 0.66 1.69 2.32 8.43 P t 0.27 7.66 2.41 1.14 1.29 3.24 18.15 TDI = 2,4-Toluenediisocyanate; TNI = Toluenenitroisocyanates, AZOC = Azo compounds; AZYC = Azoxy compounds; NSC = Nitroso compounds; AC = Amine compounds; POL = Polymer.

(51) The results show, that nitroaromatic compounds containing multiple nitrogroups can be converted into isocyanates directly. Since the number of structural isomers is increasing with the number of nitro groups the yields are presented as group yields.

(52) As stated above, the intermediates like nitroso compounds or partially carbonylated nitro aromatic compounds like Toluenenitroisocyanates (TNI) may be obtained as a result of an incomplete reaction, but is still considered as a successful outcome in terms of this invention.

(53) TABLE-US-00009 TABLE 9 Results of catalytic tests in trickle bed set up with DNT Feed stock: TDI = 2.4 + 2.6-Toluenediisocyanate; TNI = (isomers of Toluenenitroisocyanate, Byproducts = Azo compounds, Azoxy compounds, Nitroso compounds, Amine compounds, Polymer. No # TDI TNI Byproducts Q v 0.00 0.08 7.02 R v 0.06 2.04 17.47 S v 0.00 1.57 11.66 T v 0.00 2.24 5.15 U v 0.00 0.12 5.17 V v 7.00 41.03 20.4 W v 8.48 42.88 44.37 X v 33.81 59.80 5.81 Y v 16.91 39.11 40.35 Z v 19.11 42.01 35.71 AA v 23.51 40.92 32.51 AB v 11.34 58.96 23.51 AD v 19.80 47.35 29.94 AE v 1.68 29.90 43.88 AF v 12.38 61.52 16.15 AG v 18.12 71.15 5.18 AH v 10.09 60.85 13.53 AI v 23.67 64.83 10.08 AJ v 5.73 44.05 28.61 AK t 4.11 45.56 23.93 AL v 18.21 73.10 3.70 AM v 2.34 46.49 9.53 AN v 2.05 43.53 8.41 AO v 2.05 44.31 8.37 AP v 1.77 37.36 17.05 AQ v 0.00 0.21 15.97 AR v 13.60 57.68 17.72 AS v 0.02 2.03 3.84 AT v 0.00 3.36 9.63 AU v 1.65 38.77 8.90 AV v 0.33 16.63 11.89 AW v 5.56 32.18 51.16 AX v 0.19 12.07 12.19 AY v 0.00 0.17 13.84 AZ v 0.00 15.81 25.41 BA v 1.98 34.08 17.09 BB v 0.00 0.24 12.38 BC v 1.72 35.88 15.64 BD v 1.27 31.77 13.40 BE v 0.00 1.91 6.57 BF v 3.30 46.46 14.42 BG v 0.50 16.21 30.92 BH v 0.01 3.07 22.84 BI v 0.00 0.00 8.61