Method for regenerating a toxified catalyst containing ruthenium or ruthenium compounds

Abstract

A process for regenerating a catalyst containing ruthenium or ruthenium compounds, which includes, optionally at elevated temperature, subjecting the catalyst to a hydrogen halide treatment, particularly a gas stream comprising hydrogen chloride, under non-oxidative conditions and, optionally at reduced temperature, to at least a two-stage oxidative post-treatment. The catalyst may have been poisoned by sulfur compounds. After the removal of sulfur, the catalyst is subjected to an oxidative post-treatment.

Claims

1. A process for regenerating a catalyst comprising ruthenium or ruthenium compounds, which has been poisoned by sulfur in the form of sulfur compounds, comprising subjecting the catalyst, optionally at elevated temperature, to treatment with a hydrogen halide, under non-oxidative conditions and additionally, optionally at reduced temperature, to an at least two-stage oxidative post-treatment, wherein in a first process step the catalyst is partially oxidized by treatment with a gas stream comprising steam having a steam content of 0.1 to 100% by volume, and in a second process step the catalyst is further oxidized, by treatment with a gas stream comprising oxygen, the oxygen concentration of which is increased continuously or sequentially.

2. The process as claimed in claim 1, wherein the non-oxidative regeneration is carried out at a temperature up to 600° C.

3. The process as claimed in claim 1, wherein the regeneration is carried out at a pressure of up to 20 bar.

4. The process as claimed in claim 1, wherein the non-oxidative regeneration is carried out at a hydrogen halide content of 0.1 to 100% by volume.

5. The process as claimed in claim 1, wherein the oxidative post-treatment is carried out at a temperature up to 600° C.

6. The process as claimed in claim 1, wherein the oxidative post-treatment is carried out at a pressure of up to 20 bar.

7. The process as claimed in claim 1, wherein the first process step of the oxidative post-treatment is carried out at a steam content of 20 to 80 100% by volume.

8. The process as claimed in claim 1, wherein the second process step of the oxidative post-treatment is carried out at an oxygen content in the range of 0.1 to 100% by volume.

9. The process as claimed in claim 1, wherein the catalyst comprising ruthenium or ruthenium compounds is a catalyst based on ruthenium halides.

10. The process as claimed in claim 1, wherein the non-oxidative regeneration of the first stage is carried out over a time period of 0.5 hours to 100 hours.

11. The process as claimed in claim 1, wherein the oxidative post-treatment steps are each carried out independently of one another over a time period of 0.1 hours to 100 hours.

12. The process as claimed in claim 1, wherein the regeneration and the oxidative post-treatment are carried out in the same reaction space, in which the catalyst is used for carrying out the reaction which is catalyzed by the catalyst.

13. The process as claimed in claim 12, wherein the regeneration gas stream and the oxidative post-treatment streams are passed over the catalyst in countercurrent to the direction of flow of the reaction components of the catalyzed reaction in the reaction space.

14. The process as claimed in claim 1, wherein the catalyst is a catalyst for the gas phase oxidation of hydrogen chloride with oxygen.

15. The process as claimed in claim 1, wherein after the regeneration, the gas phase oxidation of hydrogen chloride with oxygen is restarted with a maximum HCl to oxygen ratio of 1:1.

16. The process as claimed in claim 1, wherein prior to the regeneration, the gas phase oxidation of hydrogen chloride with oxygen was operated again at a maximum HCl to oxygen ratio of at least 1:1.

17. The process as claimed in claim 1, wherein the regeneration and the oxidative post-treatment are carried out at intervals, wherein between the time intervals the sulfur content and/or the activity of the catalyst is determined.

18. The process as claimed in claim 1, wherein the sulfur compounds are one or more compounds selected from the series: H.sub.2SO.sub.4, H.sub.2SO.sub.3, SO.sub.3, COS, H.sub.2S, salts of H.sub.2SO.sub.4 and H.sub.2SO.sub.3.

19. The process for the catalyzed gas phase oxidation of hydrogen chloride with oxygen using a catalyst based on ruthenium or ruthenium compounds, wherein the catalyst is subjected to a regeneration process as claimed in claim 1 from a predefined value for loss of its catalytic activity.

Description

EXAMPLES

(1) Section 1: Preparation of the Catalysts

(2) To be able to illustrate the invention, pelleted supported ruthenium catalysts were prepared supported on SnO.sub.2 or TiO.sub.2.

Example 1a

(3) 200 g of SnO.sub.2 pellets (spherical, diameter approximately 1.9 mm, Alfa Aesar) were impregnated with a solution of 9.99 g of ruthenium chloride n-hydrate in 33.96 ml of H.sub.2O and then mixed thoroughly for 1 h. The moist solid was then dried at 60° C. in a muffle furnace (air) for 4 h and calcined therein at 250° C. for 16 h.

Example 1b

(4) 100 g of TiO.sub.2 pellets (cylindrical, diameter approximately 2 mm, length 2 to 10 mm, Saint-Gobain) were impregnated with a solution of ruthenium chloride n-hydrate in H.sub.2O such that the theoretical Ru content was 3% by weight. The moist pellets thus obtained were dried overnight at 60° C. and in the dry state introduced under nitrogen flushing into a solution of NaOH and 25% hydrazine hydrate solution in water and left to stand for 1 h. Excess water was then evaporated off. The moist pellets were dried at 60° C. for 2 h and then washed with 4×300 g of water. The moist pellets thus obtained were dried at 120° C. in the muffle furnace (air) for 20 min and calcined therein at 350° C. for 3 h.

(5) Section 2: Poisoning of the Catalysts with Sulfur Componds

(6) In order to be able to illustrate the invention, a portion of the prepared catalyst pellets were specifically poisoned with sulfur in the form of the sulfur compound SO.sub.2. The designation of the catalysts after poisoning and the most important features of the poisoning runs can also be seen in Table 2.

Example 2a

(7) 0.5 g of the catalyst pellets prepared according to example 1a were initially charged in a quartz reaction tube (diameter 10 mm) and perfused at 320° C. with a gas mixture 1 (consisting of 2 L/h hydrogen chloride, 1 L/h oxygen, 2 L/h nitrogen and 40 ppm SO.sub.2) for 24 hours.

Example 2b

(8) 0.5 g of the catalyst pellets prepared according to example 1b were initially charged in a quartz reaction tube (diameter 10 mm) and perfused at 320° C. with a gas mixture 1 (consisting of 2 L/h hydrogen chloride, 1 L/h oxygen, 2 L/h nitrogen and 40 ppm SO.sub.2) for 24 hours.

Example 2c

(9) 19.5 g of a supported ruthenium catalyst 1c (TiO.sub.2 support) were initially charged in a nickel reaction tube (diameter 16 mm) and perfused for more than 20 000 h at variable temperatures with a gas mixture (consisting of 1 mol/h HCl, 2 mol/h O.sub.2, 2 mol/h N.sub.2) and over this period loaded with an unknown composition and amount of sulfur components.

(10) TABLE-US-00001 TABLE 1 Designation of the catalysts poisoned with sulfur and the most important features of the poisoning course. Designation of the catalyst pellets Poisoning conditions after prior to Duration SO.sub.2 poisoning poisoning Component [h] [ppm] 2a 1a SO.sub.2 24 40 2b 1b SO.sub.2 24 40 2c 1c SO.sub.2 24 40

Example 3: Use of Regeneration Conditions of WO 2009 118 095 A3 (Regeneration Method 1) on Supported Ruthenium Catalysts (SnO.SUB.2 .Support and TiO.SUB.2 .Support)—Comparative Example

(11) 0.5 g of the non-poisoned catalyst pellets with the designation 1a and in each case 0.5 g of the catalyst pellets poisoned according to example 2 with the designation 2a, 2b and 2c were initially charged in a quartz reaction tube (diameter 10 mm) and, after heating in nitrogen (non-poisoned), were firstly subjected to an activity assay and for this purpose a gas mixture 2 (consisting of 2 L/h HCl, 8 h O.sub.2 and 10 L/h N.sub.2) were passed through at 320° C. for 18 hours. These samples were then subjected to a single regeneration. Gas mixture 4 (consisting of 2 L/h HCl and 8 L/h N.sub.2) was passed over these batches at 380° C. for 16 h. Subsequently, the temperature was lowered under regeneration conditions to 320° C. and gas mixture 3 (consisting of 2 L/h HCl, 8 L/h 02 and 10 L/h N.sub.2) was passed over the batches (1aR1, 2aR, 2bR1, 2cR1) for 4 h and the activity determined.

Example 4: Use of Regeneration Conditions of WO 2010 076 296 A1 (Regeneration Method 2) on Supported Ruthenium Catalysts (SnO.SUB.2 .Support and TiO.SUB.2 .Support)—Comparative Example

(12) 0.5 g of the non-poisoned catalyst pellets with the designation 1a and in each case 0.5 g of the catalyst pellets poisoned according to example 2 with the designation 2a, 2b and 2c were initially charged in a quartz reaction tube (diameter 10 mm) and, after heating in nitrogen (non-poisoned), were firstly subjected to an activity assay and for this purpose a gas mixture 5 (consisting of 2 L/h HCl, 1 L/h O.sub.2) were passed through at 320° C. for 18 hours. These samples were then subjected to a single regeneration. Gas mixture 6 (consisting of 1.54 L/h HCl and 1.54 L/h N.sub.2) was passed over these batches at 400° C. for 12 h. Subsequently, gas mixture 7 (consisting of 3.08 L/h synthetic air: 21% O.sub.2, 79% N.sub.2) was passed over these batches and the latter also calcined at 400° C. for 0.5 h. Subsequently, the temperature in gas mixture 7 was lowered to 320° C. and gas mixture 5 (consisting of 2 L/h HCl, 1l Uh 02) was passed over the batches (1aR2, 2aR2, 2bR2, 2cR2) for 24 h and the activity determined.

Example 5: Use of the Novel Regeneration Conditions (Regeneration Method 3) on Supported Ruthenium Catalysts (SnO.SUB.2 .Support and TiO.SUB.2 .Support)

(13) 0.5 g of the non-poisoned catalyst pellets with the designation 1a and in each case 0.5 g of the catalyst pellets poisoned according to example 2 with the designation 2a, 2b, 2c were initially charged in a quartz reaction tube (diameter 10 mm) and, after heating in nitrogen (non-poisoned), were firstly subjected to an activity assay and for this purpose a gas mixture 8 (consisting of 2 L/h HCl, 1 L/h O.sub.2 and 2 L/h N.sub.2) were passed through at 320° C. for 18 hours. These samples were then subjected to a single regeneration. Gas mixture 9 (consisting of 2 L/h HCl and 6.67 L/h N.sub.2) was passed over these batches at 380° C. for 16 h. Subsequently, the temperature was lowered to 260° C. under regeneration conditions and gas mixture 10 (consisting of steam) was passed through for 4 h. Subsequently, the following consecutive oxidative treatment is carried out at 260° C.: for 0.5 h gas mixture 11 (consisting of 0.33 L/h O.sub.2 and 2 L/h N.sub.2), for 0.5 h gas mixture 12 (consisting of 0.66 L/h O.sub.2 and 2 L/h N.sub.2), for 1 h gas mixture 13 (consisting of 1.33 L/h O.sub.2 and 2 L/h N.sub.2), and for 2 h gas mixture 14 (consisting of 2 L/h O.sub.2 and 2 L/h N.sub.2). Subsequently, the temperature in gas mixture 8 was increased to 320° C. and gas mixture 8 (consisting of 2 L/h HCl, 1 L/h O.sub.2 and 2 L/h N.sub.2) was passed over the batches (1aR3, 2aR3, 2bR3, 2cR3) for 24 h and the activity determined.

Example 6: Use of the Novel Regeneration Conditions (Regeneration Method 3) on Supported Ruthenium Catalysts (SnO.SUB.2 .Support and TiO.SUB.2 .Support)

(14) 0.5 g of catalyst pellets poisoned according to example 2 with the designation 2a and 2b were initially charged in a quartz reaction tube (diameter 10 mm) and subjected to a single regeneration. Gas mixture 9 (consisting of 2 L/h HCl and 6.67 L/h N.sub.2) was passed over these batches at 380° C. for 16 h. Subsequently, the temperature was lowered to 260° C. under regeneration conditions and gas mixture 10 (consisting of steam) was passed through for 4 h. Subsequently, the following consecutive oxidative treatment was carried out at 260° C.: for 0.5 h gas mixture 11 (consisting of 0.33 L/h O.sub.2 and 2 L/h N.sub.2), for 0.5 h gas mixture 12 (consisting of 0.66 L/h O.sub.2 and 2 L/h N.sub.2), for 1 h gas mixture 13 (consisting of 1.33 L/h O.sub.2 and 2 L/h N.sub.2), and for 2 h gas mixture 14 (consisting of 2 L/h O.sub.2 and 2 L/h N.sub.2). Subsequently, the temperature in gas mixture 8 was increased to 320° C. and gas mixture 8 (consisting of 2 L/h HCl, 1 L/h O.sub.2 and 2 L/h N.sub.2) was passed over the batches (1aR3, 2aR3, 2bR3) for 24 h and the activity determined.

Example 7: Use of Regeneration Conditions Based on WO 2009 118 095 A3 (Regeneration Method 3) on Supported Ruthenium Catalysts (SnO.SUB.2 .Support and TiO.SUB.2 .Support)—Comparative Example

(15) 0.5 g of catalyst pellets poisoned according to example 2 with the designation 2a and 2b were initially charged in a quartz reaction tube (diameter 10 mm) and subjected to a single regeneration. Gas mixture 9 (consisting of 2 L/h HCl and 6.67 L/h N.sub.2) was passed over these batches at 380° C. for 16 h. Subsequently, the temperature in gas mixture 8 was lowered to 320° C. and gas mixture 8 (consisting of 2 h HCl, 1 L/h O.sub.2 and 2 L/h N.sub.2) was passed over the batches (2aR4, 2bR4) for 24 h and the activity determined (see Table 2).

(16) TABLE-US-00002 TABLE 2 Relative Relative S content S content activity activity prior to after prior to after HCl O.sub.2 N.sub.2 regeneration regeneration Regeneration Batch regeneration* regeneration [L/h] [L/h] [L/h] [ppm] [ppm] method 1aR1 1 1.07.sup.# 2 8 10 — — 1 2aR1 1 1.04.sup.# 2 8 10 — — 1 2bR1 1 1.16.sup.# 2 8 10 — — 1 2cR1 1 1.57.sup.# 2 8 10 — — 1 1aR2 0.48 0.81.sup.# 2 1 0 — — 2 2aR2 0.44 0.96.sup.# 2 1 0 — — 2 2bR2 0.62 0.89.sup.# 2 1 0 — — 2 2cR2 0.66 0.90.sup.# 2 1 0 — — 2 1aR3 0.39 1.15.sup.# 2 1 2 — — 3 2aR3 0.46 1.12.sup.# 2 1 2 — — 3 2bR3 0.61 0.89.sup.# 2 1 2 — — 3 2cR3 0.67 1.11.sup.# 2 1 2 — — 3 2aR4 — 0.99.sup.+ 2 1 2 6600 5300 3 2bR4 — 0.89.sup.+ 2 1 2 820 530 3 2aR5 — 0.39.sup.+ 2 1 2 6600 6000 1 2bR5 — 0.39.sup.+ 2 1 2 820 600 1 *Based on sample 1aR1 for all 1a samples, based on sample 2aR1 for all 2a samples, based on sample 2bR1 for all 2b samples, based on sample 2cR1 for all 2c samples. .sup.#Based on the activity of the corresponding sample prior to regeneration .sup.+Based on the activity of the corresponding sample prior to poisoning

CONCLUSIONS

Example 3

(17) Regeneration method 1 at a low HCl:O.sub.2 ratio (1:4) in the freshly prepared and poisoned SnO.sub.2-supported catalyst (2aR1) results in a slight increase in the activity (+4%) in relation to the poisoned catalyst. In the freshly prepared and poisoned TiO.sub.2-supported catalyst (2aR1), regeneration method 1 results in a greater increase in the activity (+16%) in relation to the poisoned catalyst. In the case of the poisoned TiO.sub.2-supported catalyst (2cR1) operated for a long time in the HCl oxidation, regeneration method 1 results in a sharp increase in the activity (+57%) in relation to the poisoned catalyst. Also in the case of the freshly prepared and non-poisoned SnO.sub.2-supported catalyst (1aR1) the activity increases slightly (+7%) in relation to the starting activity according to regeneration method 1.

(18) Therefore, regeneration method 1 has proven to be a suitable method to regenerate supported ruthenium catalysts, which operate at a low HCl:O.sub.2 ratio (1:4) and have been restarted.

Example 4

(19) In the case of the experiments with regeneration method 2, it should be noted that the starting activities are much lower owing to the higher HCl to O.sub.2 ratio (2:1) compared to the low HCl:O.sub.2 ratio (1:4) in regeneration method 1. This behavior of supported ruthenium catalysts at a higher HCl to O.sub.2 ratio is known.

(20) In all supported ruthenium catalysts investigated, regeneration method 2 leads to a reduction in activity (−4 to −19%) in relation to the poisoned catalyst and the starting activity in the non-poisoned catalyst. Therefore, regeneration method 2 has proven not to be a suitable method to regenerate supported ruthenium catalysts.

Example 5

(21) Also in the case of the experiments with regeneration method 3, it should be noted that the starting activities are much lower owing to the higher HCl to O.sub.2 ratio (2:1) compared to the low HCl to O.sub.2 ratio (1:4) in regeneration method 1.

(22) However, in the freshly prepared and poisoned SnO.sub.2-supported catalyst (2aR1), regeneration method 3 results in a greater increase in the activity (+12%) in relation to the poisoned catalyst. In the freshly prepared and poisoned TiO.sub.2-supported catalyst (2aR1), regeneration method 3 results in a reduction in the activity (−11%) in relation to the poisoned catalyst. However, in the case of the poisoned TiO.sub.2-supported catalyst (2cR1) operated for a long time in the HCl oxidation, regeneration method 3 results in a sharp increase in activity (+11%) in relation to the poisoned catalyst. Also in the case of the freshly prepared and non-poisoned SnO.sub.2-supported catalyst (1aR1) the activity increases sharply (+15%) in relation to the starting activity according to regeneration method 3.

(23) Therefore, regeneration method 3 has proven to be a suitable method to regenerate supported ruthenium catalysts, which operate at a high HCl:O.sub.2 ratio (2:1) and have been restarted.

Example 6 and 7

(24) In these two examples, regeneration method 1 and regeneration method 3 were compared at a high HCl to O.sub.2 ratio (2:1) in relation to sulfur removal and activity after regeneration.

(25) Firstly, it appears that the SnO.sub.2-supported catalyst has absorbed far more sulfur by poisoning (6600 ppm) than the TiO.sub.2-supported catalyst (820 ppm). After regeneration method 1, the sulfur fraction has been reduced in the SnO.sub.2-supported catalyst by 600 ppm and in the TiO.sub.2-supported catalyst by 220 ppm. After regeneration method 3, the sulfur fraction has been reduced in the SnO.sub.2-supported catalyst by 1300 ppm and in the TiO.sub.2-supported catalyst by 290 ppm. Therefore, both regeneration methods are suitable to remove sulfur from supported ruthenium catalysts but regeneration method 3 removes a greater proportion of sulfur from the catalysts.

(26) In the SnO.sub.2-supported catalyst, regeneration method 3 results in an activity of 99% based on the starting activity in the non-poisoned catalyst. In the TiO.sub.2-supported catalyst, regeneration method 3 results in an activity of 89% based on the starting activity in the non-poisoned catalyst. On the other hand, in the SnO.sub.2-supported catalyst, regeneration method 1 results in an activity of only 39% based on the starting activity in the non-poisoned catalyst. In the TiO.sub.2-supported catalyst, regeneration method 1 also results in an activity of only 39% based on the starting activity in the non-poisoned catalyst.

(27) Thus, it has been shown that regeneration method 1 is suitable for removing sulfur from supported ruthenium catalysts and to regenerate the catalysts at a low HCl to O.sub.2 ratio, but this is no longer the case at a high HCl to O.sub.2 ratio.

(28) On the other hand, it has been shown that regeneration method 3 is suitable for removing sulfur from supported ruthenium catalysts and to regenerate the catalysts both at a low and also at a high HCl to O.sub.2 ratio.