Process for capturing sulphur impurities using specific retaining materials

Abstract

A process for capturing sulphur impurities present in gas feeds containing H.sub.2 and/or CO: a. desulphurization with a retaining material containing an active phase, b. optionally, rendering the sulphurized retaining material inert, c. oxidative regeneration of the retaining material, d. optionally, rendering the regenerated retaining material inert, and e. desulphurization with the retaining material that has been regenerated and rendered inert, and regenerating the retaining material.

Claims

1. A process for capturing sulphur impurities, present in gas feeds containing H.sub.2 and/or CO, consisting of: a. desulfurization by bringing the feed to be treated into contact, at a temperature of between 20 and 450 C., with a retaining material containing an active phase consisting of: ZnMoO.sub.4 b. optionally, rendering the sulfurized retaining material inert, c. oxidative regeneration of said retaining material, d. optionally, rendering the regenerated retaining material inert, and e. desulfurization by bringing the feed to be treated into contact, at a temperature of between 20 and 450 C., with said retaining material that has been regenerated and rendered inert, said retaining material having been regenerated at a temperature of between 20 and 600 C.

2. The process according to claim 1, wherein the retaining material is regenerated at a temperature of 300 C.-400 C.

3. The process according to claim 1, wherein the oxidative regeneration is performed at a temperature of 300-480 C.

4. The process according to claim 1, wherein the desulfurization of the feed to be treated by bringing said feed into contact with the retaining material is performed at a temperature of between 50 and 450 C.

5. The process according to claim 1, wherein the desulfurization of the feed to be treated by bringing said feed into contact with the retaining material is performed at a pressure of between 1 and 250 bar.

6. The process according to claim 1, wherein the desulfurization of the feed to be treated by bringing said feed into contact with the retaining material is performed at an hourly volume rate (HVR) of between 100 and 20 000 h.sup.1.

7. The process according to claim 1, wherein rendering the retaining material inert is performed by bringing the retaining material into contact with an inert gas, at a pressure of between 0.1 and 10 bar.

8. The process according to claim 1, wherein the oxidative regeneration consists of bringing the retaining material to be regenerated into contact with a gas containing oxygen (O.sub.2) with a content of between 0.5 and 20% by volume of O.sub.2.

9. The process according to claim 1, wherein the oxidative regeneration is performed at a pressure of between 0.1 and 10 bar.

10. The process according to claim 1, wherein the oxidative regeneration is performed at an hourly volume rate (HVR) of between 100 and 20 000 h.sup.1.

11. The process according to claim 1, wherein the active phase represents between 30 and 100% by weight, in relation to the total weight of the retaining material.

12. The process according to claim 1, wherein the retaining material comprises, apart from the active phase, at least one mineral filler that is an alumina, an alumina precursor, silica, a silica-alumina, a bentonite clay, a kaolinite clay, a montmorillonite clay, a smectite clay, zirconium oxide or titanium oxide.

13. The process according to claim 12, wherein the mineral filler is an alpha-alumina, a bentonite clay, a kaolinite clay, a montmorillonite clay, a smectite clay or a mixture thereof.

14. The process according to claim 12, wherein the mineral filler is present in the retaining material with a content of between 0.1 and 70% by weight in relation to the total solid weight of the retaining material.

15. The process according to claim 1, wherein the retaining material is present in the form of granules, compacts, extrudates, balls or monoliths.

Description

EXAMPLE

(1) Three retaining materials were prepared: a first, M1, for comparison, containing an active phase comprising a simple oxide ZnO; a second, M2, according to the invention, containing an active phase comprising a mixture of simple oxides ZnOMo03; a third, M3, according to the invention, containing an active phase comprising a mixed oxide ZnMoO4.

Preparation of the First Retaining Material M1 (for Comparison)

(2) A zinc oxide was prepared by thermal decomposition of a commercially obtained zinc carbonate (ZnCO.sub.3).sub.2.(Zn(OH).sub.2).sub.3 (Aldrich, purity>58% Zn).

(3) To this end the precursor (ZnCO.sub.3).sub.2.(Zn(OH).sub.2).sub.3 was placed in a porcelain boat and then heated in an muffle furnace under air. The temperature gradient was 4 C./minute, up to a level of 500 C. for 2 hours.

(4) This is how the first retaining material M1 (comparative) was obtained.

Preparation of the Second Retaining Material M2, according to the Invention

(5) A zinc oxide was prepared in the same manner as the retaining material M1.

(6) A commercially available molybdenum oxide (Sigma-Aldrich, purity99.5%) was also used for the preparation of the second retaining material.

(7) The two simple oxides mentioned above were physically mixed (ground) in order to obtain an equimolar mixture of simple oxides ZnOMoO.sub.3 (ratio of Zn:Mo=1).

(8) This is how the second retaining material M2 (according to the invention) was obtained.

Preparation of the Third Retaining Material M3

(9) A zinc oxide was prepared in the same manner as the retaining material M1, and a commercially available molybdenum oxide (Sigma-Aldrich, purity 99.5%) as used for the preparation of the retaining material M2 was selected.

(10) Three grinding cycles were performed followed by calcination under air at 500 C. for 8 hours of the equimolar mixture of the ZnOMoO.sub.3 oxides in order to obtain a mixed oxide ZnMoO.sub.4.

(11) All the solids of the example (ZnO, ZnOMoO.sub.3 and ZnMoO.sub.4) were characterised by X-ray diffraction, and the determination of the crystalline phases was performed by comparison of the experimental diffractograms with the files in the X-ray diffraction diagram databases of the ICDD (International Centre for Diffraction Data). In the case of the solids of the example, the files numbers that were able to be used for these characterisations were, for example, as follows: 01-070-8070 (ZnO), 04-012-8070 (MoO.sub.3) and 01-070-5387 (ZnMoO.sub.4).

(12) Each solid was assessed on a thermogravimetry test bed (sulphurisation and regeneration steps). The sulphurisation was performed using a gas consisting of 0.9% by volume of H.sub.2S in H.sub.2, at a temperature of 350 C., following a rise in temperature of 10 C./minute, under inert gas (HE), and a pressure of 1 bar.

(13) For each solid, the regeneration is performed using a gas consisting of 5% by volume of 0.sub.2 in nitrogen, at temperatures of between 450 and 650 C., and a pressure of 1 bar. The regeneration was carried out for 1 hour.

(14) Following a first regeneration, each retaining material is assessed a second time according to the sulphurisation procedure described in step 1.

(15) For each solid, a quantification of the content of sulphur by elementary analysis (combustion of the solid at 900 C. and chromatographic analysis of the SO.sub.2 formed) following each of the three steps (first sulphurisation, regeneration, second sulphurisation) was performed.

(16) Table 1 shows the measured values for the three retaining materials in the example, after each step, and as a function of the regeneration temperature.

(17) TABLE-US-00001 TABLE 1 Change in sulphur content following the various steps of the example. Sulphur content Sulphur Sulphur content (% by weight) content (% (% by weight) after the first by weight) after the second desulphurisation Regeneration after the desulphurisation Retaining performed at temperature first performed at material 350 C. ( C.) regeneration 350 C. M1 31.1 480 31.1 625 0.2 30.8 M2 14.3 480 0.1 14.2 M3 15.3 450 0.04 14.9

(18) These results show that under the conditions of the example, the regeneration of the M1 retaining material is only possible at a temperature of greater than or equal to 625 C.

(19) The regeneration of M2, for its part, was possible at a temperature of 480 C.

(20) Finally, it was possible to regenerate M3 from 450 C. upwards.

(21) The analyses performed on M1, M2 and M3 after the second sulphurisation show that the solids, once they have been regenerated, can again be used in a desulphurisation process.