Process for removal sulfur compounds from sulfuric acid

Abstract

The disclosure provides a process for removing one or more sulfur compounds from sulfuric acid, said process is remarkable in that it comprises the following steps: a) providing a first stream (101) comprising sulfuric acid, wherein said first stream comprises one or more sulfur compounds other than sulfuric acid; b) providing a second stream (102) comprising a diatomic halogen molecule and water; c) contacting the second stream (102) with the first stream (101) under operating conditions; wherein the second stream (102) reacts with the one or more sulfur compounds of the first stream to produce sulfuric acid, providing an effluent of sulfuric acid (103).

Description

[0001] PROCESS FOR REMOVAL SULFUR COMPOUNDS FROM SULFURIC ACID

[0002] TECHNICAL FIELD

[0003] The present disclosure pertains to a process purification of sulfuric acid.

[0004] TECHNICAL BACKGROUND

[0005] Sulfuric acid is an important industrial chemical that is used in the manufacturing processes of many goods over a wide range of applications, such as in the manufacture of fertilizers, pigments, dyes, drugs, explosives, detergents, and inorganic salts and acids, as well as in petroleum refining and metallurgical processes.

[0006] There are many industrial processes wherein aqueous sulfuric acid solution is obtained as a main or side product and wherein the solution is further concentrated by using distillation to generate a stream of sulfuric acid. However, sulfur compounds, like dispersed sulfur, sulfur oxygenates such as sulfur dioxide, hydrogen sulfide, disulfur dibromide, and / or carbonyl sulfide, are dissolved into the sulfuric acid, so that it is not feasible to remove them easily, for example by mere filtration, and subsequently produced a high-quality sulfuric acid effluent.

[0007] Although some methods exist for producing concentrated sulfuric acid, such as those described in WO2010136649 or in EP1639252, the resulting effluent still contains a certain amount of those sulfur compounds and is thus referred to as a low-quality sulfuric acid feedstock.

[0008] There is therefore a need for a process that removes at least partially the one or more sulfured contaminants from a sulfuric acid.

[0009] SUMMARY

[0010] According to a first aspect, the disclosure provides a process for removing one or more sulfur compounds from sulfuric acid, said process is remarkable in that it comprises the following steps: a) providing a first stream comprising sulfuric acid, wherein said first stream comprises one or more sulfur compounds other than sulfuric acid; b) providing a second stream comprising water and a halogen component comprising one or more diatomic molecules; c) contacting the second stream with the first stream under operating conditions, wherein the second stream reacts with the one or more sulfur compounds of the first stream to produce additional sulfuric acid, and d) recovering an effluent comprising sulfuric acid.

[0011] Surprisingly, it was found that using a stream comprising water and a halogen component comprising one or more diatomic molecules can remove one or more sulfur compounds other than sulfuric acid from a stream sulfuric acid. Thus, after treatment of a first stream comprising sulfuric acid, wherein said first stream comprises one or more sulfur compounds other than sulfuric acid with water and a halogen component, less sulfur compounds can be found in the recovered effluent of sulfuric acid by comparison with the amount of sulfur compounds present at the beginning, namely in the first stream. In consequence, the ratio of sulfuric acid to the one or more sulfur compounds in the recovered effluent is increased by comparison to the ratio in the first stream. The present process is based on the reaction of diatomic halogen molecules that are used as oxidants and water with one or more sulfur compounds to produce further sulfuric acid.

[0012] For example, in addition to sulfuric acid, hydrogen halide is produced at step (c), so the effluent recovered at step (d) comprises hydrogen halide.

[0013] In an embodiment, the process comprises the additional step (e) of separating said hydrogen halide from the sulfuric acid to recover a stream of hydrogen halide. For example, step (e) is performed by distillation.

[0014] By performing this additional step (e), it is, therefore, possible to remove the hydrogen halide that was produced during the step (c) of removal of one or more sulfur compounds. The resulting effluent of sulfuric acid has thus been significantly purified and is therefore clean for downstream implementations.

[0015] Advantageously, the process further comprises the additional step (f) of electrolyzing the stream of hydrogen halide recovered at step (e) to recover a hydrogen stream and halogencontaining stream comprising a halogen component comprising one or more diatomic molecules. With preference, said halogen-containing stream is recycled in step (b).

[0016] Advantageously, the diatomic halogen molecule in the second stream is dibromine (Br2) and / or dichlorine (Ch); with preference, dibromine.

[0017] Advantageously, the one or more sulfur compounds are selected from S, SO2, H2S, S2Br2, COS and any mixtures thereof. More particularly, the one or more sulfur compounds are or comprises S and / or SO2.

[0018] Advantageously, said first stream further comprises water. Advantageously, the amount of sulfuric acid in the first stream is at most 98 wt.% based on the total weight of said first stream; with preference, ranging between 25 wt.% and 80 wt.%, or ranging between 25 wt.% and 60 wt.%, or ranging between 30 wt.% and 60 wt.%.

[0019] Advantageously, the amount of the one or more sulfur compounds in the first stream is ranging between 0.1 wt.% and 25 wt.% of the total weight of said first stream, or between 1 wt.% and 20 wt.%, or between 5 wt.% and 15 wt.%.

[0020] Advantageously, the second stream provided at step (b) comprised at most 16 wt.% of water based on the total weight of said second stream; preferably at most 15 wt.%, more preferably at most 14 wt.%, even more preferably, at most 13 wt.%.

[0021] Advantageously, the operating conditions used in step (c) comprise a temperature of at most 200°C, preferably of at most 190°C, and more preferably of at most 180°C. For example, the operating conditions used in step (c) comprise a temperature ranging between 20°C and 200°C; preferably, between 50°C and 200°C, more preferably, between 100°C and 200°C, or between 150°C and 200°C, even more preferably, between 155°C and 195°C, most preferably, between 160°C and 190°C, and even most preferably, between 165°C and 185°C, or between 165°C and 180°C.

[0022] Advantageously, the operating conditions used in step (c) comprise a partial pressure of the halogen component in the second stream of at most 2.0 MPa, preferably of at most 1 .5 MPa, more preferably of at most 1.0 MPa. For example, the operating conditions used in step (c) comprise a partial pressure of the halogen component in the second stream ranging between 0.1 MPa and 2.0 MPa; preferably, between 0.2 MPa and 2.0 MPa, and more preferably, between 0.2 MPa and 1.0 MPa.

[0023] Advantageously, the operating conditions used in step (c) comprises a temperature ranging between 150°C and 200°C, or between 155°C and 195°C, or between 160°C and 190°C, or between 165°C and 185°C; and a partial pressure of the halogen component in the second stream ranging between 0.1 MPa and 2.0 MPa; preferably, between 0.2 MPa and 2.0 MPa, and more preferably, between 0.2 MPa and 1.0 MPa.

[0024] Advantageously, the operating conditions used in step (c) comprise a residence time of at least 1 second; or of at least 10 seconds. For example, the operating conditions used in step (c) comprise a residence time ranging between 10 seconds and 12 hours, or between 10 seconds and 8 hours. In another aspect, the disclosure relates to a use of a stream comprising water and a halogen component comprising one or more diatomic molecules for removing at least a part of one or more sulfur compounds other than sulfuric acid contained in a first stream of sulfuric acid.

[0025] DESCRIPTION OF THE FIGURES

[0026] Figure 1 illustrates an embodiment of an installation according to the disclosure.

[0027] Figure 2 illustrates a further embodiment of an installation according to the disclosure.

[0028] Figure 3 illustrates a preferred embodiment wherein the reaction chamber is a distillation column.

[0029] DETAILED DESCRIPTION

[0030] For the purpose of the disclosure, the following definitions are given.

[0031] The terms "comprising", "comprises" and "comprised of' as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising", "comprises" and "comprised of" also include the term “consisting of”.

[0032] The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g., 1 to 5 includes 1 , 2, 3, 4, 5 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the recited endpoint values themselves (e.g., from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0033] The reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. The particular features, structures, characteristics or embodiments may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the disclosure and form different embodiments, as would be understood by those in the art. The term “alkali metal” refers to an element classified as an element from the group 1 of the periodic table of elements, excluding hydrogen. According to this definition, the alkali metals are Li, Na, K, Rb, Cs and Fr.

[0034] The term “alkaline earth metal” refers to an element classified as an element from the group 2 of the periodic table of elements. According to this definition, the alkaline earth metals are Be, Mg, Ca, Sr, Ba and Ra.

[0035] The term “transition metal” refers to an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell (IIIPAC definition). According to this definition, the transition metals are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ac, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, and Cn. The metals Ga, In, Sn, TI, Pb and Bi are considered as “post-transition” metal.

[0036] Unless otherwise defined, all terms used in disclosing the disclosure, including technical and scientific terms, have the meaning as commonly understood by one skilled in the art to which this disclosure belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present disclosure.

[0037] The particular features, structures, characteristics or embodiments may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments.

[0038] The disclosure provides a process for removing one or more sulfur compounds from sulfuric acid, said process is remarkable in that it comprises the following steps: a) providing a first stream (101 , 301) comprising sulfuric acid, wherein said first stream (101 , 301) comprises one or more sulfur compounds other than sulfuric acid; b) providing a second stream (102, 302) comprising water and a halogen component comprising one or more diatomic molecules; c) contacting the second stream (102, 302) with the first stream (101 , 301) under operating conditions; wherein the second stream (102, 302) reacts with the one or more sulfur compounds other than sulfuric acid of the first stream (101 , 301) to produce additional sulfuric acid; and d) recovering an effluent (103, 303) comprising sulfuric acid.

[0039] With regard to step (a) of providing a first stream (101 , 301) comprising sulfuric acid

[0040] The first stream can be an aqueous solution of sulfuric acid. The amount of sulfuric acid into said first stream can be at most 98 wt.% based on the total weight of said first stream; or at most 96 wt.%, or at most 95 wt.%, or at most 90 wt.%, or at most 85 wt.%, or at most 80 wt.%, or at most 75 wt.%, or at most 70 wt.%, or at most 65 wt.%, or at most 60 wt.%.

[0041] The amount of sulfuric acid into said first stream can be at least 15 wt.% based on the total weight of said first stream; or at least 18 wt.%, or at least 20 wt.%, or at least 22 wt.%, or at least 25 wt.%, or at least 28 wt.%, or at least 30 wt.%.

[0042] For example, the amount of sulfuric acid into said first stream ranges from 15 to 98 wt.% based on the total weight of said first stream; with preference, between 25 wt.% and 80 wt.%, or ranging between 25 wt.% and 60 wt.%, or ranging between 30 wt.% and 60 wt.%.

[0043] The first stream comprises one or more sulfur compounds other than sulfuric acid. The one or more sulfur compounds other than sulfuric acid in of the first stream of sulfuric acid can be dissolved in said sulfuric acid so it is difficult to remove them by filtration. Such one or more sulfur compounds can be selected from S, SO2, H2S, S2Br2, COS, and any mixtures thereof. Preferably, the one or more sulfur compounds are selected from S, SO2, H2S, S2Br2, and any mixtures thereof, more preferably, selected from S, SO2, H2S, and any mixtures thereof, most preferably, the one or more sulfur compounds are or comprise S and / or SO2.

[0044] These one or more sulfur compounds other than sulfuric acid are considered as sulfured contaminants in sulfuric acid, and their presence is significant to what is called a technical stream of sulfuric acid, which is a low-quality stream of H2SO4. In particular, sulfur is a multivalent non-metal, tasteless, and odorless. In its native form, sulfur is a yellow crystalline solid. It occurs in nature as a pure element and can be mined through the use of wells drilled into sulfur deposits. Recovered elemental sulfur is a nondiscretionary byproduct from petroleum refining, natural gas processing, and coking plants obtained after processing emissions. S2Br2 is a yellow-brown liquid that fumes in the air. It is prepared by a direct combination of the elements and purified by vacuum distillation. Sulfur dioxide, SO2, is a colorless gas or liquid with a strong, choking odor. It is produced from the burning of fossil fuels (coal and oil) and the smelting of mineral ores (aluminum, copper, zinc, lead, and iron) that contain sulfur. Some other sources of sulfur dioxide include petroleum refineries, cement manufacturing, paper pulp manufacturing, and metal smelting and processing facilities. Hydrogen sulfide is colorless gas having a strong odour of rotten eggs. Hydrogen sulfide occurs naturally in crude petroleum, natural gas, volcanic gases, and hot springs. It can also result from the bacterial breakdown of organic matter. Hydrogen sulfide can also result from industrial activities, such as food processing, coke ovens, kraft paper mills, tanneries, and petroleum refineries. The content of the one or more sulfur compounds in the first stream comprising sulfuric acid other than sulfuric acid, i.e., of the one or more sulfured contaminants, can be ranging between 0.1 wt.% and 25 wt.% of the total weight of said first stream, or between 0.5 wt.% and 22 wt.%, or between 1 wt.% and 20 wt.%, or between 2 wt.% and 18 wt.%, or between 5 wt.% and 15 wt.%.

[0045] With regard to step (b) of providing a second stream (102, 302) comprising water and a halogen component comprising one or more diatomic molecules

[0046] The one or more diatomic halogen molecules can dibromine (Br2) and / or dichlorine (Ch); advantageously, dibromine.

[0047] Advantageously, the second stream provided at step (b) comprised at most 20 wt.% of water based on the total weight of said second stream; or at most 18 wt.%; or at most 16 wt.%, preferably at most 15 wt.%, more preferably at most 14 wt.%, even more preferably, at most 13 wt.%.

[0048] With regard to step (c) of contacting the second stream (102, 302) with the first stream (101 , 301) under operating conditions

[0049] When the sulfur compound other than sulfuric acid is sulfur, there is a two-step reaction, involving the formation of 826^:

[0050] 2S + Br2S2Br2

[0051] S2Br2+ 5Br2+ 8H2O 2H2SO4+ 12HBr

[0052] When the sulfur compound is sulfur dioxide, a one-step reaction is achieved:

[0053] SO2+ Br2+ 2H2O H2SO4 + 2HBr

[0054] When the sulfur compound is hydrogen sulfide, the following reaction is written in the following way:

[0055] H2S + 4H2O + 4Br2-^H2SO4+ 8HBr

[0056] Advantageously, the operating conditions used in step (c) comprise a temperature of at most 200°C, preferably of at most 190°C, more preferably of at most 180°C. For example, the operating conditions used in step (c) comprises a temperature ranging between 20°C and 200°C; with preference, a temperature ranging between 50°C and 200°C, more preferably, between 100°C and 200°C, or between 105°C and 190°C, or between 110°C and 180°C, or between 115°C and 180°C. In particular, the temperature of about 110°C favors the decomposition of the intermediate S2Br2.

[0057] Advantageously, the operating conditions used in step (c) comprise a partial pressure of the halogen component of at most 2.0 MPa, preferably of at most 1 .5 MPa, more preferably of at most 1.0 MPa. For example, the operating conditions used in step (c) comprise a partial pressure into bromine ranging between 0.1 MPa and 2.0 MPa; or between 0.2 MPa and 2.0 MPa, or between 0.2 MPa and 1 .0 MPa.

[0058] For example, the operating conditions used in step (c) comprises a temperature ranging between 150°C and 200°C, or between 155°C and 195°C, or between 160°C and 190°C, or between 165°C and 185°C; and a partial pressure of the halogen component in the second stream ranging between 0.1 MPa and 2.0 MPa; preferably, between 0.2 MPa and 2.0 MPa, and more preferably, between 0.2 MPa and 1.0 MPa. The pressure is required to keep the second stream liquid.

[0059] Advantageously, the operating conditions used in step (c) comprise a residence time of at least 1 second; or of at least 10 seconds. For example, the operating conditions used in step (c) comprise a residence time ranging between 1 second and 12 hours, or between 10 seconds and 12 hours, or between 10 seconds and 8 hours.

[0060] When the second stream reacts with the one or more sulfur compounds other than sulfuric acid of the first stream comprising sulfuric acid, there is production of further sulfuric acid. An effluent of sulfuric acid is therefore recovered. The amount of sulfuric acid in said effluent of sulfuric acid is higher than the amount of sulfuric acid in the first stream of sulfuric acid provided in step (a).

[0061] For example, when the amount of sulfuric acid within said first stream is 98 wt.% based on the total weight of said first stream, the amount of sulfuric acid in said effluent of sulfuric acid can be 98.5 wt.% or more based on that total weight of said effluent, more preferably 98.7 wt.% or more.

[0062] In addition to further sulfuric acid, hydrogen halide can be produced at step (c). With preference, the process comprises the additional step (e) of separating said hydrogen halide from the sulfuric acid, for example by distillation.

[0063] By performing this additional step (e), it is therefore possible to remove the hydrogen halide that was produced during the removal of the one or more sulfur compounds. The resulting effluent of sulfuric acid has thus been significantly purified and is therefore clean for downstream implementations.

[0064] According to the disclosure, the hydrogen halide that is removed from the effluent of sulfuric acid recovered in step (d) can be further processed by electrolysis to produce a stream of hydrogen and an halogen-containing stream comprising a diatomic halogen molecule, for example dibromine (Br2). Said stream of diatomic halogen molecule can be further used in step (b) so as to make the second stream comprising water and a halogen component comprising one or more diatomic molecules.

[0065] The disclosure also relates to an installation for the removal of one or more sulfur compounds other than sulfuric acid from a first stream comprising sulfuric acid according to the process as explained above and as shown in Fig. 1 , wherein the installation comprises a reaction chamber 1 provided with a first inlet for feeding the first stream 101 into a reaction chamber 1 , a second inlet for feeding the second stream 102 into the reaction chamber 1 and a first outlet for evacuating an effluent 103 of sulfuric acid. The installation is preferably resistant to corrosion. Suitable materials are glass-lined, glass, quartz, special resistance alloys, such as A59 ( / .e., nickel-chromium-molybdenum alloy), or metals, such as Ta.

[0066] For example, the installation further comprises a second outlet for evacuating a stream 104 of hydrogen halide.

[0067] In a further embodiment, the installation further comprises an electrolytical cell 2 for electrolysis of the stream 104 of hydrogen halide. The electrolytical cell 2 may be any electrolytical cell suitable for electrolysis of halogen halides. The stream 104 of hydrogen halide is fed into the electrolytical cell 2 and a process of electrolysis takes place wherein hydrogen and the corresponding diatomic halogen molecule are formed. The hydrogen is collected via stream 201. The diatomic halogen molecule is collected via stream 202. In a preferred embodiment, the recovered diatomic halogen molecule is introduced in the reaction flow as a reactant, as shown in Fig. 2.

[0068] In another preferred embodiment, as shown in Fig. 3, the reaction chamber 1 is a distillation column 3, as known to a skilled person, comprising a first inlet for feeding the first stream 301 and a second inlet for feeding the second stream 302. The distillate (e.g., the hydrogen halide) represents the stream 304 of hydrogen halide while the bottom is collected as the effluent 303 of sulfuric acid.

[0069] Example

[0070] The following non-limiting example illustrates the disclosure: A 10g sample of 98.5 wt.% sulfuric acid based on the total weight of the sample was placed in a round-bottom glass vessel suited for operations at elevated pressures of up to 1 MPa. The vessel was equipped with a magnetic stirrer and a back-pressure controller ensuring safe operation with no overpressure. A sulfur sample of 0.2g of finely grinded powder was transferred into the liquid and left under vigorous stirring for 2h. After the procedure was finished, the vessel was flashed with nitrogen and closed. Stirring was turned on and 4g of bromine and after 0.5g of water were gradually introduced into the vessel using syringe pumps. The vessel was heated up to 100°C and left stirred for about 24h. After, the vessel was cooled down to 25°C and flushed with nitrogen through a NaOH scrubber to remove any vapors of bromine or hydrogen bromide present. Following the flushing, liquid was isolated and transferred into a rotary evaporator, which was heated up to 200°C at 0.1 bar for 12h.

[0071] Collected product is a dense colorless liquid with no visible distributed solids with a total mass of 10.67g.

[0072] Sample was analyzed on Dionex ICS 3000 ion chromatograph equipped with an eluent generator, a suppressor and a conductivity detector. Satisfactory analyte separation was achieved on a Dionex lonPacAS11-HC, 4x250 mm analytical column used in combination with a corresponding precolumn (Dionex lonPac AG11-HC, 4x50 mm). KOH solution was used as mobile phase in isocratic mode with concentration of 15 mM. The injection volume was 10 pL, the flow rate 1 mL min-1and the column temperature 35 °C.

[0073] Calibration curve was used to determine the amount of sulfuric acid in the sample. The reaction samples were diluted 100,000 times volumetrically with the same 18.2 MQ cm deionized water and the amount was calculated accordingly, which indicated an amount of sulfuric acid in the sample product of -98.2 wt.%.

Claims

CLAIMS1 . A process for removing one or more sulfur compounds from sulfuric acid, said process is characterized in that it comprises the following steps: a) providing a first stream (101 , 301) comprising sulfuric acid, wherein said first stream comprises one or more sulfur compounds other than sulfuric acid; b) providing a second stream (102, 302) comprising water and a halogen component comprising one or more diatomic molecules; c) contacting the second stream (102, 302) with the first stream (101 , 301) under operating conditions, wherein the second stream (102, 302) reacts with the one or more sulfur compounds of the first stream (101 , 301) to produce additional sulfuric acid, and d) recovering an effluent (103, 303) comprising sulfuric acid.

2. Process according to claim 1 , characterized in that the halogen component in the second stream (102, 302) is dibromine and / or dichlorine.

3. Process according to claim 1 or 2, characterized in that the halogen component in the second stream (102, 302) is dibromine.

4. Process according to any one of claims 1 to 3 characterized in that the one or more sulfur compounds are selected from S, SO2, H2S, S2Br2, COS, and any mixtures thereof.

5. Process according to any one of claims 1 to 4, characterized in that said first stream further comprises water.

6. Process according to any one of claims 1 to 5, characterized in that the amount of sulfuric acid within said first stream is at most 98 wt.% based on the total weight of said first stream.

7. Process according to claim 6, characterized in that the amount of sulfuric acid within said first stream based on the total weight of said first stream is ranging between 25 wt.% and 60 wt.%.

8. Process according to any one of claims 1 to7, characterized in that the amount of the one or more sulfur compounds in the first stream is ranging between 0.1 wt.% and 25 wt.% of the total weight of said first stream.

9. Process according to any one of claims 1 to 8, characterized in that the second stream (102, 302) provided at step (b) comprises at most 16 wt.% of water based on the total weight of said second stream.

10. Process according to any one of claims 1 to 9, characterized in that the operating conditions used in step (c) comprise a temperature of at most 200°C.

11. Process according to any one of claims 1 to 10, characterized in that the operating conditions used in step (c) comprise a temperature ranging between 20°C and 200°C.

12. Process according to claim 11 , characterized in that the operating conditions used in step (c) comprise a temperature ranging between 100°C and 200°C.

13. Process according to any one of claims 1 to 12, characterized in that the operating conditions used in step (c) comprise a partial pressure into bromine of at most 2.0 MPa.

14. Process according to any one of claims 1 to 13, characterized in that the operating conditions used in step (c) comprise a partial pressure into bromine ranging between 0.1 MPa and 2.0 MPa.

15. Process according to claim 14, characterized in that the operating conditions used in step (c) comprise a partial pressure into bromine ranging between 0.2 MPa and 1.0 MPa.

16. Process according to any one of claims 1 to 15, characterized in that in addition of sulfuric acid, hydrogen halide is produced at step (c) and wherein the effluent of sulfuric acid (103, 303) also comprises hydrogen halide.

17. Process according to any one of claims 1 to 16, characterized in that the process comprises an additional step (e) of separating said hydrogen halide from the sulfuric acid to recover a stream (104; 304) of hydrogen halide.

18. Process according to claim 17, characterized in that the additional step (e) is performed by distillation.

19. Process according to any one of claims 1 to 18, characterized in that the process comprises an additional step (f) of electrolyzing the stream (104; 304) of hydrogen halide recovered at step (e) to recover a hydrogen stream (201) and a halogen-containing stream (202) comprising a halogen component comprising one or more diatomic molecules.

20. Process according to claim 19, characterized in that said halogen-containing stream (202) is recycled in step (b).

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