METHOD FOR CLEANING SULFUROUS CORROSIVE PROCESS GASES

Abstract

The invention relates to a method for cleaning corrosive process gases that contain sulfur compounds. According to the method, a gas stream that contains corrosive gases is conducted, in a sorption phase, over an inorganic sorbent material which absorbs at least one of the sorbable sulfurous components on the sorbent material, and the sulfurous compound-depleted gas stream is removed.

Claims

1.-14. (canceled)

15. A process for purifying corrosive process gases containing sulfur compounds, wherein a gas stream comprising corrosive gases is in a sorption phase passed over an inorganic sorption material which takes up at least one of the sorbable sulfur-containing components on the sorption material to discharge the gas stream depleted of sulfur compounds.

16. The process as claimed in claim 15, wherein the sulfur compounds comprise one or more compounds selected from the group consisting of SO.sub.x, H.sub.2S, CS.sub.2, SOCl.sub.2, S2Cl.sub.2, SCl.sub.2, COS and mercaptans.

17. The process as claimed in claim 15, wherein the sulfur compounds are present as trace gas in a concentration of not more than 10 ppm.

18. The process as claimed in claim 15, wherein the sorption material comprises as the active component at least one oxide or mixed oxide of cerium and/or zirconium and/or titanium.

19. The process as claimed in claim 15, wherein the sorption material is supported on a support material chemically resistant to hydrogen chloride, wherein the support material and any active component of the sorption material are different.

20. The process as claimed in claim 15, wherein the corrosive process gas comprises at least hydrogen chloride or hydrogen chloride and chlorine as the corrosive component.

21. The process as claimed in claim 20, wherein gas stream depleted of sulfur compounds is sent to a downstream catalytic process.

22. The process as claimed in claim 20, wherein the gas purification of the corrosive process gas is performed in a reaction zone arranged in a reactor which is separate from a downstream further reactor and whose temperature and/or pressure may be controlled independently of the further reactor.

23. The process as claimed in claim 20, wherein gas purification of the corrosive process gas is performed in a reaction zone arranged in a reactor having a plurality of reaction zones, wherein the reaction zone for gas purification is separate from at least one further downstream reaction zone for the gas phase reaction and the temperature and/or the pressure in the reaction zone for gas purification may be controlled independently of the downstream reaction zone.

24. The process as claimed in claim 15, wherein the sorption medium comprises a supported cerium oxide catalyst which is obtained when a cerium compound is applied to the support by means of dry impregnation and the impregnated support is subsequently dried and calcinated at elevated temperature.

25. The process as claimed in claim 15, wherein the purification of the corrosive process gas is effected at a temperature of not more than 420° C.

26. The process as claimed in claim 15, wherein the purification of the corrosive process gas is effected at a pressure of at least 1013 hPa.

27. The process as claimed in claim 15, wherein the gas stream depleted of sulfur compounds has a residual content of sulfur compounds of not more than 0.05 ppm.

28. A method comprising utilizing a sorption material comprising as an active component at least one oxide or mixed oxide of cerium and/or zirconium, and removing sulfur compounds from corrosive process gas containing sulfur compounds.

Description

EXAMPLES

Example 1

[0041] To produce a sorption medium for sulfur compounds a ZrO.sub.2-support material (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 mortaring) was employed: [0042] specific surface area of 55 m.sup.2/g (nitrogen adsorption, BET evaluation) [0043] bimodal pore radius distribution, wherein 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) [0044] pore volume of 0.27 cm.sup.3/g (mercury porosimetry) [0045] bulk density of 1280 kg/m.sup.3 (measured in a DN100 measuring cylinder of 350 mm in height)

[0046] This ZrO.sub.2 support material (SZ 31163) was crushed with a mortar and classified into screen fractions. 1 g of the 100-250 μm 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 μm) 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 amount of cerium supported corresponds to a proportion of 7% by weight based on the calcined catalyst, calculating the catalyst components as CeO.sub.2 and ZrO.sub.2.

Example 2

[0047] 0.5 g of the sorption medium prepared in example 1 was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 20° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 1 L/h of oxygen, 2 L/h of nitrogen and 5 ppm of SO.sub.2 for 336 h. The sulfur content on the sorption medium was then determined by elemental analysis. The result is shown in table 1.

Example 3

[0048] 0.5 g of the sorption medium prepared in example 1 was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 260° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 1 L/h of oxygen, 2 L/h of nitrogen and 5 ppm of SO.sub.2 for 336 h. The quartz reaction tube was heated by an electrically heated oven. The sulfur content on the sorption medium was then determined by elemental analysis. The result is shown in table 1.

Example 4

[0049] 0.5 g of the sorption medium prepared in example 1 was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 300° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 1 L/h of oxygen, 2 L/h of nitrogen and 5 ppm of SO.sub.2 for 336 h. The quartz reaction tube was heated by an electrically heated oven. The S content on the sorption medium was then determined by elemental analysis. The result is shown in table 1.

Example 5

[0050] 0.5 g of the sorption medium prepared in example 1 was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 340° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 1 L/h of oxygen, 2 L/h of nitrogen and 5 ppm of SO.sub.2 for 336 h. The quartz reaction tube was heated by an electrically heated oven. The S content on the sorption medium was then determined by elemental analysis. The result is shown in table 1.

Example 6

[0051] 0.5 g of the sorption medium prepared in example 1 was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 380° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 1 L/h of oxygen, 2 L/h of nitrogen and 5 ppm of SO.sub.2 for 336 h. The quartz reaction tube was heated by an electrically heated oven. The S content on the sorption medium was then determined by elemental analysis. The result is shown in table 1.

Example 7

[0052] 0.5 g of the sorption medium prepared in example 1 was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 420° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 1 L/h of oxygen, 2 L/h of nitrogen and 5 ppm of SO.sub.2 for 336 h. The quartz reaction tube was heated by an electrically heated oven. The S content on the sorption medium was then determined by elemental analysis. The result is shown in table 1.

Example 8

[0053] A commercially available CeO.sub.2-doped ZrO.sub.2 support material (manufacturer: Saint-Gobain NorPro; type: SZ 61191, 3 mm diameter spheres) of tetragonal structure and having the following specifications was employed: [0054] 18% CeO.sub.2, remainder ZrO.sub.2 [0055] specific surface area of 110 m.sup.2/g (nitrogen adsorption, BET evaluation) [0056] bimodal pore radius distribution, wherein a pore class 1 (transport pores) has a median of 150 nm and a pore class 2 (fine pores) has a median of 4 nm (mercury porosimetry) [0057] pore volume of 0.25 cm.sup.3/g (mercury porosimetry) [0058] bulk density of 1400 kg/m.sup.3 (measured in a DN100 measuring cylinder of 350 mm in height)

[0059] The ZrO.sub.2 catalyst support was tested and analyzed in the same way as the sorption medium in examples 2-7. The result is shown in table 1.

Example 9

[0060] A commercially available ZrO.sub.2 support material (manufacturer: Saint-Gobain NorPro; type: SZ 31152, 3 mm diameter spheres) of tetragonal structure and having the following specifications was employed: [0061] specific surface area of 140 m.sup.2/g (nitrogen adsorption, BET evaluation) [0062] bimodal pore radius distribution, wherein a pore class 1 (transport pores) has a median of 150 nm and a pore class 2 (fine pores) has a median of 3 nm (mercury porosimetry) [0063] pore volume of 0.30 cm.sup.3/g (mercury porosimetry) [0064] bulk density of 1100 kg/m.sup.3 (measured in a DN100 measuring cylinder of 350 mm in height)

[0065] The ZrO.sub.2 catalyst support was tested and analyzed in the same way as the sorption medium in examples 2-7. The result is shown in table 1.

Example 10

[0066] A ZrO.sub.2 microparticle support material (manufacturer: Saint-Gobain NorPro, 0.781 mm diameter microparticles) of monoclinic structure and having the following specifications was employed: [0067] specific surface area of 102 m.sup.2/g (nitrogen adsorption, BET evaluation) [0068] bimodal pore radius distribution, wherein 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) [0069] pore volume of 0.65 cm.sup.3/g (mercury porosimetry) [0070] bulk density of 722 kg/m.sup.3 (measured in a DN100 measuring cylinder of 250 mm in height) [0071] The ZrO.sub.2 catalyst support was tested and analyzed in the same way as the sorption medium in examples 2-7.

[0072] The essential indices and results from the abovementioned examples are summarized in table 1 below.

TABLE-US-00001 TABLE 1 Ex. BET Sulfur [ppm] # Material [m.sup.2/g] unpoisoned RT 260° C. 300° C. 340° C. 380° C. 420° C. 2-7 CeO.sub.2/ZrO.sub.2 — 26 230 470 400 4400 5500 8900  8 CeO.sub.2/ZrO.sub.2 110 88 470 420 700 89? 3900 6300  9 ZrO.sub.2 140 120 260 88 1000 25500 200 14 10 ZrO.sub.2 102 22 140 19 200 940 600 5

Example 11/12

[0073] Commercially available ZrO2 support materials (manufacturer: Saint-Gobain NorPro) of tetragonal structure having the following specifications were employed:

[0074] Type: SZ 61152, 3 mm diameter spheres (example 11): [0075] Specific surface of 133 m.sup.2/g [0076] Median pore diameter: 775 Å [0077] Total pore volume of 0.30 cm.sup.3/g [0078] Bulk density of 1240 kg/m.sup.3 type: SZ 31163, 3 mm diameter spheres (example 12): [0079] Specific surface area of 57.2 m.sup.2/g [0080] Median pore diameter: 171 Å [0081] Total pore volume of 0.29 cm.sup.3/g [0082] Bulk density of 1281.3 kg/m.sup.3

[0083] 1 g of each sorption medium was initially charged in a fixed bed in a quartz reaction tube (internal diameter 8 mm) and at a temperature of 20° C. subjected to a gas mixture flow of 2 L/h of hydrogen chloride, 2.75 L/h of nitrogen and 100 ppm SO2, H.sub.2S or COS for 168 h. The sulfur content on the sorption medium was then determined by elemental analysis. The result is shown in table 2.

TABLE-US-00002 TABLE 2 Sulfur [ppm] After SO.sub.2 After H.sub.2S After COS Example BET [m.sup.2g.sup.−1] unpoisoned adsorption adsorption adsorption 11 133 99 180 120 100 12 57.2 24 31 28 52

CONCLUSIONS

[0084] The sorption properties of the materials vary markedly at different temperatures.

[0085] In the case of the pure ZrO.sub.2 materials the sorption capacity is almost always below the sorption capacity of CeO.sub.2-containing materials. In the case of the pure ZrO.sub.2 materials the sorption capacity follows a linear trend with BET surface area. The higher the BET surface area, the higher in most cases the sorption capacity. In addition, the sorption capacity of pure ZrO.sub.2 materials increases linearly with temperature from 260° C. to 340° C., beyond which the sorption capacity of the pure ZrO.sub.2 materials falls again. At the highest measured temperature (420° C.) the sorption capacity is vanishingly small and the sulfur concentration is actually below the concentration of the starting materials.

[0086] It was also shown that a different performance (adsorbed amount of sulfur (ppm)) is obtained depending on the ZrO.sub.2 material used and the sulfur species. It can therefore be concluded that while ZrO.sub.2 materials are generally suitable for the adsorption of sulfur species the material must be selected according to the sulfur contamination.

[0087] The CeO.sub.2/ZrO.sub.2 materials exhibit the same trend with increasing temperature as the pure ZrO.sub.2 materials. However, the sorption capacity for the CeO.sub.2/ZrO.sub.2 materials is much higher than for the pure ZrO.sub.2 materials. In addition, the sorption capacity of the CeO.sub.2/ZrO.sub.2 materials increases continuously up to a temperature of 420° C., in contrast to the pure ZrO.sub.2 materials.