CATALYST AND METHOD FOR PRODUCING CHLORINE BY MEANS OF GAS PHASE OXIDATION

Abstract

The invention relates to known catalysts which contain cerium or other catalytically active components for producing chlorine by means of a catalytic gas phase oxidation of hydrogen chloride with oxygen. A catalyst material is described for producing chlorine by means of a catalytic gas phase oxidation of hydrogen chloride with oxygen, wherein the catalyst comprises at least oxide compounds of the cerium as active components and zirconium dioxide microparticles as the carrier components, and the catalyst is characterized by a particularly high yield, measured in kg.sub.Cl2/kg.sub.KA T.Math.h, based on the mass of the catalyst.

Claims

1.-17. (canceled)

18. A catalyst material composed of a porous catalyst support and a catalytic coating for a process for thermocatalytic production of chlorine from hydrogen chloride and oxygen-containing gas, wherein the catalyst material at least comprises: at least one oxide compound of cerium as the catalytic coating and spherical zirconium dioxide microparticles as the support component.

19. The catalyst material as claimed in claim 18, wherein the catalyst has a bulk density of at least 700 kg/m.sup.3 measured in a DN100 graduated cylinder having a fill height of 250 mm.

20. The catalyst material as claimed in claim 18, wherein the catalyst support consists of zirconium dioxide to an extent of at least 90% by weight.

21. The catalyst material as claimed in claim 18, wherein the catalyst support consists of spherical particles, wherein the principal dimension of the particles is on average from 0.1 mm to not more than 1.0 mm.

22. The catalyst material as claimed in claim 21, wherein the average particle size of the catalyst support is from 0.1 mm to not more than 1.0 mm, and the D.sub.90 and D.sub.10 values of the particle size distribution deviate from the D.sub.50 value by not more than 10%, in particular measured by laser diffraction.

23. The catalyst material as claimed in claim 18, wherein the catalyst material is subjected to a high temperature calcination in the presence of oxygen-containing gases, wherein the calcination temperature is in the range 300? C. to 1100? C.

24. The catalyst material as claimed in claim 23, wherein the high-temperature calcination is effected over a period of 30 min to 24 h.

25. The catalyst material as claimed in claim 18, wherein the porous catalyst support in the uncoated state has a bimodal pore diameter distribution, wherein the median diameter of a pore class 1 of relatively large pores is from 30 to 200 nm and the median diameter of a pore class 2 of relatively small pores is from 2 to 25 nm, wherein the pore diameters are in particular measured by mercury porosimetry.

26. The catalyst material as claimed in claim 18, wherein the catalyst support in the uncoated state has a surface area of 30 to 250 m.sup.2/g, measured by the method of nitrogen adsorption with evaluation according to BET.

27. The catalyst material as claimed in claim 18, wherein the zirconium dioxide support component is present in the monoclinic crystal form to an extent of at least 90% by weight.

28. The catalyst material as claimed in claim 18, wherein the content of cerium in the catalyst material is 1% to 30% by weight.

29. The catalyst material as claimed in claim 18, wherein the oxide compound of cerium is selected from Ce(III) oxide (Ce.sub.2O.sub.3) and cerium(IV) oxide (CeO.sub.2).

30. The catalyst material as claimed in claim 18, wherein the catalyst material is obtained by applying a cerium compound to the support by means of dry impregnation and the impregnated support is subsequently dried and calcinated at relatively high temperature.

31. The use of the catalyst material as claimed in claim 18 as a catalyst in the thermocatalytic production of chlorine from hydrogen chloride and an oxygen-containing gas.

32. A process for thermocatalytic production of chlorine from hydrogen chloride and oxygen-containing gas, wherein a catalyst material as claimed in claim 18 is used as catalyst.

33. The process as claimed in claim 32, wherein the cerium-containing catalyst material is combined with a ruthenium catalyst or a catalyst containing ruthenium compounds on a separate support, wherein the ruthenium catalyst is employed as a low-temperature complement, and the cerium-containing catalyst material is employed as a high-temperature complement.

34. The process as claimed in claim 33, wherein the two different catalyst types are arranged in different reaction zones.

Description

EXAMPLES

[0064] The essential parameters and results from the examples which follow are summarized in a table after the final example.

Example 1 (Inventive)

[0065] A ZrO.sub.2 microparticle catalyst support (manufacturer: Saint-Gobain NorPro, 0.781 mm diameter microparticles) of monoclinic structure and having the following specifications was employed: [0066] Specific surface area of 102 m.sup.2/g (nitrogen adsorption, evaluation according to BET) [0067] Bimodal pore radius distribution where a pore class 1 (transport pores) has a median of 110 nm and a pore class 2 (fine pores) has a median of 8 nm (mercury porosimetry) [0068] Pore volume of 0.65 cm.sup.3/g (mercury porosimetry) [0069] Bulk density of 722 kg/m.sup.3 (measured in a DN100 graduated cylinder of 250 mm in height)

[0070] 20.6 g of cerium(III) nitrate hexahydrate were made up to 25 ml with deionized water. 0.288 ml of the thus produced cerium(III) nitrate solution was initially charged into a snap-lid bottle having been diluted with an amount of deionized water sufficient to fill the total pore volume and 1 g of the ZrO.sub.2 catalyst support was stirred in until the initially charged solution was fully absorbed (dry impregnation methodology). The impregnated ZrO.sub.2 catalyst support was then dried at 120? C. for 5 h and then calcinated in a muffle furnace in air. To this end, the temperature in the muffle furnace was increased linearly from 20? C. to 500? C. over 160 min and held at 500? C. for 5 h. The muffle furnace was then cooled linearly from 500? C. to 20? C. over 160 min. The supported amount of cerium corresponds to a proportion of 7% by weight based on the calcinated catalyst, wherein the catalyst components are calculated as CeO.sub.2 and ZrO.sub.2.

[0071] 0.25 g of the thus prepared catalyst was diluted with 0.5 g of Spheriglass (quartz glass, 500-800 ?m) and initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) before a gas mixture of 1 L/h (standard conditions, STP) of hydrogen chloride, 4 L/h (STP) of oxygen and 5 L/h of nitrogen (STP) were passed therethrough at 430? C. The quartz reaction tube was heated by an electrically heated oven. After 2 h, the product gas stream was passed into a 30% by weight potassium iodide solution for 30 min. The iodine formed was then back-titrated with 0.1 N thiosulfate standard solution to determine the amount of chlorine introduced. A chlorine formation rate of 2.25 kg.sub.Cl2/kg.sub.CAT.Math.h (based on the catalyst mass) was measured.

Example 2 (Inventive)

[0072] 1 g of a catalyst according to example 1 was produced, wherein the supported amount of cerium was adjusted to a proportion of 9% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 1. A chlorine formation rate of 2.35 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 3 (Inventive)

[0073] 1 g of a catalyst according to example 1 was produced, wherein the supported amount of cerium was adjusted to a proportion of 14% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 1. A chlorine formation rate of 2.64 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 4 (Inventive)

[0074] 1 g of a catalyst according to example 1 was produced, wherein the supported amount of cerium was adjusted to a proportion of 17% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 1. A chlorine formation rate of 2.72 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 5 (Inventive)

[0075] 1 g of a catalyst according to example 1 was produced, wherein the supported amount of cerium was adjusted to a proportion of 20% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 1. A chlorine formation rate of 2.62 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 6 (Inventive)

[0076] 1 g of a catalyst according to example 1 was produced, wherein the supported amount of cerium was adjusted to a proportion of 30% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 1. A chlorine formation rate of 2.36 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

[0077] Given sufficient Ce loadings (ex. 3-5) the catalysts based on undoped ZrO.sub.2 as support material exhibit the best yields (2.6-2.7 kg.sub.Cl2/kg.sub.CAT.Math.h). Up to a loading of 14% by weight the yield based on catalyst mass of these particularly preferred CeO.sub.2/ZrO.sub.2 catalysts (active component/support) increases with cerium content. At a loading of 14-20% by weight the yield based on catalyst mass remains approximately constant; the ZrO.sub.2 catalyst support is saturated with active component. From a loading of 30% by weight the yield based on catalyst mass decreases; the high proportion of active component appears to fill the small pores, thus reducing the available surface area.

Example 7 (Comparative Example)

[0078] ZrO.sub.2 microparticle catalyst support according to example 1 was tested in the same way as the catalyst in example 1. A chlorine formation rate of 0.00 kg.sub.Cl2/kg.sub.CAT.Math.h was measured. ZrO.sub.2 supports without the CeO.sub.2 active component are thus suitable only as a support and not as an active component.

Example 8 (Inventive)

[0079] A ZrO.sub.2 catalyst support (manufacturer: Saint-Gobain NorPro; type: 0.372 mm diameter microparticles) of monoclinic structure and having the following specifications was employed: [0080] Specific surface area of 93 m.sup.2/g (nitrogen adsorption, evaluation according to BET) [0081] Pore volume of 0.42 cm.sup.3/g (mercury porosimetry) [0082] Bulk density of 1000 kg/m.sup.3 (measured in a DN100 graduated cylinder of 250 mm in height)

[0083] This ZrO.sub.2 microparticle catalyst support was pretreated according to example 1 and then used to produce 1 g of a catalyst according to example 1, wherein the supported amount of cerium was adjusted to a proportion of 5% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 1. A chlorine formation rate of 1.55 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 9 (Inventive)

[0084] 1 g of a catalyst according to example 10 was produced, wherein the supported amount of cerium was adjusted to a proportion of 7% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 10. A chlorine formation rate of 1.97 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 10 (Inventive)

[0085] 1 g of a catalyst according to example 10 was produced, wherein the supported amount of cerium was adjusted to a proportion of 9% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 10. A chlorine formation rate of 2.18 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

Example 11 (Inventive)

[0086] 1 g of a catalyst according to example 10 was produced, wherein the supported amount of cerium was adjusted to a proportion of 15% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 10. A chlorine formation rate of 2.14 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

[0087] Given sufficient Ce loadings (ex. 9-11) the catalysts based on undoped ZrO.sub.2 as support material exhibit the best yields (2.0-2.2 kg.sub.Cl2/kg.sub.CAT.Math.h). Up to a loading of 7-9% by weight the yield based on catalyst mass of these particularly preferred CeO.sub.2/ZrO.sub.2 catalysts (active component/support) increases with cerium content. At a loading of 15% by weight the yield based on catalyst mass remains approximately constant; the ZrO.sub.2 catalyst support is saturated with active component.

Example 12 (Comparative Example)

[0088] ZrO.sub.2 microparticle catalyst support according to example 8 was tested in the same way as the catalyst in example 8. A chlorine formation rate of 0.00 kg.sub.Cl2/kg.sub.CAT.Math.h was measured. ZrO.sub.2 supports without the CeO.sub.2 active component are thus suitable only as a support and not as an active component.

Example 13 (Comparative Example)

[0089] A ZrO.sub.2 catalyst support (manufacturer: Saint-Gobain NorPro; type: SZ 31163; extrudates of 3-4 mm in diameter and 4-6 mm in length) of monoclinic structure and having the following specifications (before pestling) was employed: [0090] Specific surface area of 55 m.sup.2/g (nitrogen adsorption, evaluation according to BET) [0091] Bimodal pore radius distribution where a pore class 1 (transport pores) has a median of 60 nm and a pore class 2 (fine pores) has a median of 16 nm (mercury porosimetry) [0092] Pore volume of 0.27 cm.sup.3/g (mercury porosimetry) [0093] Bulk density of 1280 kg/m.sup.3 (measured in a DN100 graduated cylinder of 350 mm in height)

[0094] This ZrO.sub.2 catalyst support (SZ 31163) was crushed with a mortar and classified into screen fractions. 1 g of the 100-250 ?m screen fraction was dried at 160? C. and 10 kPa for 2 h. 50 g of cerium(III) nitrate hexahydrate were dissolved in 42 g of deionized water. 0.19 ml of the thus produced cerium(III) nitrate solution was initially charged in a snap-lid bottle having been diluted with an amount of deionized water sufficient to fill the total pore volume and 1 g of the dried screen fraction (100-250 ?m) of the ZrO.sub.2 catalyst support was stirred in until the initially charged solution was fully absorbed (dry impregnation methodology). The impregnated ZrO.sub.2 catalyst support was then dried at 80? C. and 10 kPa for 5 h and then calcinated in a muffle furnace in air. To this end, the temperature in the muffle furnace was increased linearly from 30? C. to 900? C. over 5 h and held at 900? C. for 5 h. The muffle furnace was then cooled linearly from 900? C. to 30? C. over 5 h. The supported amount of cerium corresponds to a proportion of 7% by weight based on the calcinated catalyst, wherein the catalyst components are calculated as CeO.sub.2 and ZrO.sub.2.

[0095] 0.25 g of the thus prepared catalyst was diluted with 1 g of Spheriglass (quartz glass, 500-800 ?m) and initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) before a gas mixture of 1 L/h (standard conditions, STP) of hydrogen chloride, 4 L/h (STP) of oxygen and 5 L/h of nitrogen (STP) were passed therethrough at 430? C. The quartz reaction tube was heated by an electrically heated oven. After 2 h, the product gas stream was passed into a 30% by weight potassium iodide solution for 30 min. The iodine formed was then hack-titrated with 0.1 N thiosulfate standard solution to determine the amount of chlorine introduced. A chlorine formation rate of 1.17 kg.sub.Cl2/kg.sub.CAT.Math.h (based on the catalyst mass) was measured.

Example 14 (Comparative Example)

[0096] 1 g of a catalyst according to example 13 was produced, wherein the supported amount of cerium was adjusted to a proportion of 15% by weight based on the calcinated catalyst. The catalyst was tested in accordance with example 13. A chlorine formation rate of 1.28 kg.sub.Cl2/kg.sub.CAT.Math.h was measured.

[0097] The essential parameters and results from the recited examples are summarized in the table below.

TABLE-US-00001 Ex. Support Ce STY # kg/m.sup.3 % by weight g/gh 1 ZrO.sub.2 7 2.25 2 ZrO.sub.2 9 2.35 3 ZrO.sub.2 14 2.64 4 ZrO.sub.2 17 2.72 5 ZrO.sub.2 20 2.62 6 ZrO.sub.2 30 2.36 7 (comp.) ZrO.sub.2 0 0.00 8 ZrO.sub.2 5 1.55 9 ZrO.sub.2 7 1.97 10 ZrO.sub.2 9 2.18 11 ZrO.sub.2 15 2.14 12 (comp.) ZrO.sub.2 0 0.00 13 (comp.) ZrO.sub.2 7 1.17 14 (comp.) ZrO.sub.2 15 1.28

CONCLUSIONS

[0098] ZrO.sub.2 supports without the CeO.sub.2 active component have zero activity (examples 7 and 12) and are thus suitable only as a support and not as an active component.

[0099] Given sufficient Ce loadings (ex. 3-5/9-10) the catalysts based on undoped microparticle ZrO.sub.2 as support material exhibit the best yields (2.1-2.7 kg.sub.Cl2/kg.sub.CAT.Math.h). Up to a loading of 7-14% by weight the yield based on catalyst mass of these two particularly preferred CeO.sub.2/ZrO.sub.2 microparticle catalysts (active component/support) increases with cerium content. From a loading of 14-20% by weight the yield based on catalyst mass remains approximately constant; the ZrO.sub.2 microparticle catalyst support is saturated with active component. From a loading of 30% by weight the yield based on catalyst mass decreases; the high proportion of active component appears to fill the small pores, thus reducing the available surface area.

[0100] At a comparable loading of 7% by weight the best CeO.sub.2/ZrO.sub.2 microparticle catalyst (2.25 kg.sub.Cl2/kg.sub.CAT.Math.h, ex. 1) exhibits a yield based on the catalyst mass that is 1.9 times higher than the best noninventive alternative catalyst (CeO.sub.2/ZrO.sub.2: 1.17 kg.sub.Cl2/kg.sub.CAT.Math.h, ex. 13). The active component cerium is thus markedly better utilized in the case of these novel CeO.sub.2/ZrO.sub.2 microparticle catalysts than in the case of other commonly used supports.

[0101] The best CeO.sub.2/ZrO.sub.2 microparticle catalyst (2.72 kg.sub.Cl2/kg.sub.CAT.Math.h, ex. 4) exhibits a yield based on the catalyst mass that is 2.1 times higher than the best noninventive alternative catalyst (CeO.sub.2/ZrO.sub.2: 1.28 kg.sub.Cl2/kg.sub.CAT.Math.h, ex. 14).