PROCESS FOR THE PRODUCTION OF HYDROGEN-ENRICHED SYNTHESIS GAS

Abstract

The invention relates to a process for the production of hydrogen-enriched synthesis gas by a catalytic water-gas shift reaction, comprising the steps: introducing a gaseous flow (1) comprising at least one organic sulphide, optionally in its oxide form, in a first reactor (2) comprising a catalyst X.sub.1, collecting a sulfur-containing gaseous flow (3) from the first reactor, introducing the raw synthesis gas (4) in a second reactor (6), introducing the sulfur-containing gaseous flow (3) in the second reactor where the catalytic water-gas shift reaction takes place and comprising a sulfur-resistant shift catalyst X.sub.2, collecting an outlet flow (7) comprising hydrogen-enriched synthesis gas from the second reactor.

The invention also relates to the use of said at least one organic sulphide, optionally in its oxide form, in a process for the production of hydrogen-enriched synthesis gas by a catalytic water-gas shift reaction.

Claims

1. A process for the production of hydrogen-enriched synthesis gas by a catalytic water-gas shift reaction operated on a raw synthesis gas, the process comprising: introducing a gaseous flow (1) comprising at least one compound of formula (I) ##STR00006## wherein: R is selected from a linear or branched alkyl radical containing from 1 to 4 carbon atoms, and a linear or branched alkenyl radical containing from 2 to 4 carbon atoms, n is 0, 1 or 2, x is 0, 1, 2, 3 or 4, R′ is selected from a linear or branched alkyl radical containing from 1 to 4 carbon atoms, a linear or branched alkenyl radical containing from 2 to 4 carbon atoms and, only when n=x=0, a hydrogen atom, into a first reactor comprising a catalyst X.sub.1, the catalyst X.sub.1 comprising at least one metal selected from groups VI B and VIII of the periodic table, collecting the gaseous flow from the first reactor, introducing a raw synthesis gas into a second reactor containing a sulfur-resistant shift catalyst X.sub.2, introducing the gaseous flow from the first reactor into the second reactor where the catalytic water-gas shift reaction takes place, the gaseous flow being introduced into the second reactor either directly through flow and/or after mixture through flow with the raw synthesis gas, and collecting an outlet flow from the second reactor, the outlet flow comprising hydrogen-enriched synthesis gas.

2. The process according to claim 1, wherein the compound of formula (I) is selected from dimethyl disulfide and dimethyl sulfoxide.

3. The process according to claim 1, wherein the catalytic water-gas shift reaction is carried out with an inlet gas temperature of at least 230° C.

4. The process according to claim 1, wherein the first reactor is operated at a temperature ranging from 100 to 600° C.

5. The process according to claim 1, wherein the first reactor is operated at a pressure ranging from 0 to 60 bar.

6. The process according to claim 1, wherein the compound of formula (I) is continuously injected into the first reactor at a flow rate of 1 NI/h to 10 Nm.sup.3/h.

7. The process according to claim 1, wherein a hydrogen flow is introduced into the first reactor, the hydrogen flow coming from an exogenous source or being collected from the outlet flow of the second reactor.

8. The process according to claim 1, wherein the catalyst X.sub.1 comprises molybdenum, tungsten, nickel and cobalt.

9. The process according to claim 1, wherein the catalyst X.sub.2 is a cobalt and molybdenum-based catalyst.

10. The process according to claim 1, wherein the catalyst X.sub.2 comprises an alkali metal.

11. The process according to claim 1, wherein the catalytic water-gas shift reaction is carried out at a pressure of at least 10 bar.

12. The process according to claim 1, wherein the raw synthesis gas comprises water and carbon monoxide in a molar ratio of water to carbon monoxide of at least 1:2.

13. The process according to claim 1, wherein the residence time in the second reactor ranges from 20 to 60 seconds.

14. The process according to claim 1, wherein the compound of formula (I) is dimethyl sulfoxide.

15. The process according to claim 1, wherein the compound of formula (I) is dimethyl disulfide.

16. The process according to claim 1, wherein the gaseous flow contains no added hydrogen sulfide.

17. The process according to claim 1, wherein a start-up phase of the first reactor is performed before implementation of the process.

18. The process according to claim 5, wherein the first reactor is operated at a pressure ranging from 10 to 40 bar.

19. The process according to claim 12, wherein the raw synthesis gas comprises water and carbon monoxide in a molar ratio of water to carbon monoxide of at least 1:4.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0045] FIG. 1 represents one embodiment of an installation for the process according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0046] The invention relates to a process for the production of hydrogen-enriched synthesis gas by a catalytic water-gas shift reaction operated on a raw synthesis gas, comprising the following steps: [0047] introducing a gaseous flow 1 comprising at least one compound of formula (I):

##STR00003## [0048] in which R is selected from a linear or branched alkyl radical containing from 1 to 4 carbon atoms, and a linear or branched alkenyl radical containing from 2 to 4 carbon atoms, n is equal to 0, 1 or 2, x is an integer selected from 0, 1, 2, 3 or 4, R′ is selected from a linear or branched alkyl radical containing from 1 to 4 carbon atoms, a linear or branched alkenyl radical containing from 2 to 4 carbon atoms and, only when n=x=0, a hydrogen atom, in a first reactor 2 comprising a catalyst X.sub.1, said catalyst X.sub.1 comprising at least one metal selected from groups VI B and VIII of the periodic table, [0049] collecting a sulfur-containing gaseous flow 3 from the first reactor 2, [0050] introducing the raw synthesis gas 4 in a second reactor 6, [0051] introducing the sulfur-containing gaseous flow 3 in the second reactor 6 where the catalytic water-gas shift reaction takes place and comprising a sulfur-resistant shift catalyst X.sub.2, the sulfur-containing gaseous flow 3 being introduced in the second reactor either directly through flow 3.1 and/or after mixture through flow 3.2 with the raw synthesis gas 4, [0052] collecting an outlet flow 7 from the second reactor 6, said outlet flow 7 comprising hydrogen-enriched synthesis gas.

[0053] Within the meaning of the present invention, by “alkyl” radical, it is to be understood a saturated hydrocarbon chain comprising carbon atoms and hydrogen atoms, preferably consisting in only carbon atoms and hydrogen atoms.

[0054] Within the meaning of the present invention, by “alkenyl” radical, it is to be understood an unsaturated hydrocarbon chain comprising at least one carbon-carbon double bond and comprising carbon atoms and hydrogen atoms, preferably consisting in only carbon atoms and hydrogen atoms.

[0055] In an embodiment of the invention, the first reactor 2 is a catalytic reactor, preferably a fixed bed catalytic reactor. The gaseous flow 1 may be heated before entering the first reactor 2 at a temperature ranging from 100 to 600° C., preferably ranging from 100 to 400° C.

[0056] The first reactor 2 comprises a catalyst X.sub.1 comprising at least one metal selected from groups VI B and VIII of the periodic table, preferably molybdenum, tungsten, nickel and cobalt. A combination of at least two of these transition metals is preferably used, such as cobalt and molybdenum, or nickel and molybdenum, or nickel and tungsten, more preferably cobalt and molybdenum.

[0057] Catalyst X.sub.1 may be supported on a porous material such as alumina, silica or silica-alumina.

[0058] As an example of suitable catalyst X.sub.1 according to the invention, mention may be made of a catalyst containing cobalt and molybdenum supported on alumina.

[0059] In a preferred embodiment of the invention, the first reactor 2 comprising catalyst X.sub.1 may be filled with an inert material to allow an efficient distribution of the gaseous flow into the first reactor 2. Suitable inert materials may be silicon carbide. Advantageously, catalyst X.sub.1 and the inert material are placed in successive layers into the first reactor 2.

[0060] The gaseous flow 1 introduced in the first reactor 2 comprises at least one compound of formula (I):

##STR00004##

[0061] in which: [0062] R is selected from a linear or branched alkyl radical containing from 1 to 4 carbon atoms, and a linear or branched alkenyl radical containing from 2 to 4 carbon atoms, [0063] n is equal to 0, 1 or 2, [0064] x is an integer selected from 0, 1, 2, 3 or 4, [0065] R′ is selected from a linear or branched alkyl radical containing from 1 to 4 carbon atoms, a linear or branched alkenyl radical containing from 2 to 4 carbon atoms and, only when n=x=0, a hydrogen atom.

[0066] According to one embodiment, the compound of formula (I) that may be used in the process of the present invention is an organic sulphide, optionally in its oxide form (when n is different from zero), obtained according to any process known per se, or else commercially available, optionally containing a reduced amount of, or no, impurities that may be responsible for undesired smells, or optionally containing one or more odor-masking agents (see e.g. WO2011012815A1).

[0067] Among preferred R and R′ radicals, mention may be made of methyl, propyl, allyl and 1-propenyl radicals. According to an embodiment of the invention, in the above formula (I), x represents 1, 2, 3 or 4, preferably x represents 1 or 2, more preferably x represents 1.

[0068] According to a preferred embodiment, the compound of formula (I) for use in the process of the present invention is a compound of formula (Ia):

R—S—S.sub.x—R′  (Ia)

[0069] which corresponds to formula (I) wherein n is equal to 0, and R, R′ and x are as defined above.

[0070] Preferably, the compound of formula (Ia) is dimethyl disulphide (“DMDS”).

[0071] According to a preferred embodiment of the invention, the compound of formula (I) for use in the process of the present invention is a compound of formula (Ib):

##STR00005##

[0072] which corresponds to formula (I) wherein n is equal to 1, and R, R′ and x are as defined above.

[0073] Preferably, the compound of formula (Ib) is dimethyl sulfoxide (“DMSO”).

[0074] It should be understood that mixtures of two or more compounds of formula (I) may be used in the process of the present invention. Especially mixtures of di- and/or polysulphides may be used, for example mixtures of disulphides, such as disulphide oils (“DSO”).

[0075] In an embodiment of the invention, the gaseous flow 1 is continuously injected into the first reactor 2.

[0076] The concentration of compound(s) of formula (I), preferably of dimethyl disulphide, into the gaseous flow 1 may range from 100 to 500,000 ppmv, preferably from 100 to 200,000 ppmv, more preferably from 100 to 100,000 ppmv. The flow rate of compound(s) of formula (I), preferably of dimethyl disulphide, may range from 1 NI/h to 10 Nm.sup.3/h.

[0077] In an embodiment of the invention, the gaseous flow 1 also comprises hydrogen. Hydrogen may come from an exogenous source or may be collected from the outlet flow 7 of the second reactor 6. By “exogenous source” is meant a source external to the process. The concentration of hydrogen into the gaseous flow 1 may range from 100 to 106 ppmv, preferably from 10,000 to 999,900 ppmv, more preferably from 200,000 to 999,900 ppmv. The flow rate of hydrogen into the gaseous flow 1 may range from 0.1 Nm.sup.3/h to 10,000 Nm.sup.3/h.

[0078] According to an embodiment, hydrogen is recovered, for example by purification, from the outlet flow 7 before being introduced into the gaseous flow 1.

[0079] The first reactor 2 may be used at a temperature ranging from 100 to 600° C., preferably from 150 to 400° C., more preferably from 200 to 350° C. The first reactor 2 may be used at a pressure ranging from 0 to 60 bar (6 MPa), preferably from 10 to 40 bar (4 MPa).

[0080] A sulfur-containing gaseous flow 3 is collected at the outlet of the first reactor 2 and introduced in the second reactor 6 where the water-gas shift reaction takes place. The sulfur-containing gas flow 3 is introduced in the second reactor 6 either directly and/or in a mixture with the raw synthesis gas 4. A valve may be present in the line containing the sulfur-containing gaseous flow 3 in order to direct the flow through lines 3.1 or 3.2 (see for example FIG. 1). With reference to FIG. 1, if the valve 5 is programmed to direct the flow through line 3.1, then the sulfur-containing gaseous flow 3 is introduced directly into the second reactor 6 (independently of the introduction of the raw synthesis gas 4). If the valve 5 is programmed to direct the flow through line 3.2, then the sulfur-containing gaseous flow 3 is mixed with the raw synthesis gas 4 before entering the second reactor 6; in this embodiment, a mixture of sulfur-containing gaseous flow 3 and raw synthesis gas 4 is introduced into the second reactor 6. It is also possible to provide a process wherein the valve 5 directs the flow 3 simultaneously through lines 3.1 and 3.2.

[0081] The raw synthesis gas 4 is typically obtained after a gasification step of a raw material such as coke, coal, biomass, naphtha, liquefied petroleum gas, heavy fuel oil. The production of synthesis gas is well known in the state of the art. The raw synthesis gas 4 may also be obtained from a Steam Methane Reformer.

[0082] According to the present invention, the raw synthesis gas 4 comprises carbon monoxide, and optionally other gases, such as hydrogen, carbon dioxide, nitrogen and water, hydrocarbons (e.g. methane), rare gases (e.g. argon), nitrogen derivatives (e.g. ammonia, hydrocyanic acid), etc.

[0083] According to an embodiment of the invention, the raw synthesis 4 comprises carbon monoxide and hydrogen, and optionally other gases such as carbon dioxide, nitrogen and water, hydrocarbons (e.g. methane), rare gases (e.g. argon), nitrogen derivatives (e.g. ammonia, hydrocyanic acid), etc.

[0084] According to another embodiment of the invention, the raw synthesis gas comprises carbon monoxide, carbon dioxide, hydrogen, nitrogen and water.

[0085] The raw synthesis gas 4 may also comprise sulfur-containing components. In this case, the raw synthesis gas 4 may comprise carbon monoxide, carbon dioxide, hydrogen, nitrogen and water as main components and sulfur-containing components in lower concentrations. The sulfur-containing components may be hydrogen sulphide, carbonyl sulphide. Typical (endogenous) sulfur content in the raw synthesis gas 4 ranges from about 20 to about 50,000 ppmv. Typical (endogenous) sulfur content in the raw synthesis gas 4 may depend on the raw material initially used for the production of the raw synthesis gas 4.

[0086] The water-gas shift reaction is carried out in the second reactor 6 comprising a catalyst X.sub.2.

[0087] The water-gas shift reaction consists in the conversion of carbon monoxide and water contained in the raw synthesis gas 4 to carbon dioxide and hydrogen according to equation (1):

H.sub.2O.sub.(g)+CO.sub.(g)⇄CO.sub.2(g)+H.sub.2(g)  (1)

[0088] wherein (g) indicates gaseous form.

[0089] This water-gas shift reaction allows to obtain a hydrogen-enriched synthesis gas.

[0090] By “hydrogen-enriched synthesis gas” according to the present invention, it is to be understood that the synthesis gas at the outlet of the process of the invention comprises more hydrogen than the synthesis gas at the inlet of the process of the invention. In other words, the proportion of hydrogen in the gas at the outlet of the process (stream 7) is higher than the proportion of hydrogen in the gas at the outlet of the process (stream 4).

[0091] According to an embodiment of the invention, water may be added to the raw synthesis gas 4. Introduction of additional (exogenous) water allows to shift the equilibrium to the formation of carbon dioxide and hydrogen. Additional (exogenous) water may be introduced either directly to the second reactor 6 or in a mixture with the raw synthesis gas 4.

[0092] The efficiency of water-gas shift reaction and thus of the hydrogen enrichment of the synthesis gas may be measured directly by hydrogen purity analysis, for instance with a gas chromatograph. It could also be indirectly measured by determining the CO conversion into CO.sub.2 meaning that the water-gas shift reaction has occurred. The CO conversion into CO.sub.2 is known by measuring the CO conversion and the CO.sub.2 yield.

[0093] In an embodiment of the invention, the molar ratio of water to carbon monoxide in the gas entering the water-gas shift reaction is of at least 1, preferably at least 1.2, more preferably at least 1.4, advantageously at least 1.5. The molar ratio of water to carbon monoxide may range from 1 to 3, preferably from 1.2 to 2.5, more preferably from 1.5 to 2.

[0094] In an embodiment of the invention, the second reactor 6 is a catalytic reactor, preferably a fixed bed catalytic reactor.

[0095] The catalyst X.sub.2 suitable for use in the water-gas shift reaction is a sulfur-resistant shift catalyst. By “sulfur-resistant shift catalyst” is meant a compound capable of catalyzing the water-gas shift reaction in the presence of sulfur-containing components.

[0096] Catalysts suitable for use in the water-gas shift reaction may comprise at least one transition metal other than iron and copper, preferably selected from the group consisting of molybdenum, cobalt and nickel. A combination of at least two of these transition metals is preferably used, such as cobalt and molybdenum, or nickel and molybdenum, more preferably cobalt and molybdenum.

[0097] The catalysts according to the invention may be either supported or unsupported, preferably supported. Suitable catalyst supports may be alumina.

[0098] In a preferred embodiment, the catalyst X.sub.2 also comprises an alkali metal selected from the group consisting of sodium, potassium and caesium, preferably potassium and caesium, or salts thereof. An example of a particularly active catalyst is the combination of caesium carbonate, caesium acetate, potassium carbonate or potassium acetate, together with cobalt and molybdenum.

[0099] As an example of suitable catalysts X.sub.2 according to the invention, mention may be made of sulfur-resistant shift catalysts such as those disclosed by Park et al. in “A Study on the Sulfur-Resistant Catalysts for Water Gas Shift Reaction—IV. Modification of CoMo/γ-Al.sub.2O.sub.3Catalyst with Iron Group Metals”, Bull. Korean Chem. Soc. (2000), Vol. 21, No. 12, 1239-1244.

[0100] In an embodiment of the invention, the gas entering the water-gas shift reaction is pre-heated to a temperature of at least 230° C. In a preferred embodiment, this temperature ranges from 240 to 320° C., preferably from 250 to 310° C.

[0101] In an embodiment of the invention, the inlet gas temperature in the second reactor 6 is at least 230° C. and preferably at most 400° C. Preferably, this temperature ranges from 240° C. to 320° C., preferably from 250° C. to 310° C.

[0102] In an embodiment of the invention, the pressure for the water-gas shift reaction is of at least 10 bars (1 MPa), preferably ranges from 10 to 30 bars (1 MPa to 3 MPa), more preferably from 15 to 25 bars (1.5 MPa to 2.5 MPa).

[0103] In an embodiment of the invention, the residence time in the second reactor 6 ranges from 20 to 60 seconds, preferably from 30 to 50 seconds, allowing the determination of the amount of catalyst X.sub.2 in reactor 6. The residence time is defined by the following formula:

[00001]$\mathrm{residence}\mathrm{time}=\frac{V_{\mathrm{cat}}}{D_{\mathrm{gas}}}\times \frac{P_{reac}}{P_{\mathrm{atm}}}$

[0104] wherein V.sub.cat represents the volume of catalyst X.sub.2 in the reactor 6 expressed in m.sup.3, D.sub.gas represents the inlet gas flow rate of flow 3 and flow 4 expressed in Nm.sup.3/s, P.sub.reac and P.sub.atm respectively represent the pressure in the reactor and the atmospheric pressure expressed in Pa.

[0105] In an embodiment of the invention, the CO conversion rate of the water-gas shift reaction is of at least 50%, preferably at least 60%, more preferably at least 65%. The CO conversion rate is calculated as follows:

[00002]$\mathrm{CO}\mathrm{Conversion}\left(\%\right)=\frac{\left(Q.Math.{\mathrm{CO}}_{\mathrm{entry}}-Q.Math.{\mathrm{CO}}_{\mathrm{exit}}\right)}{Q.Math.{\mathrm{CO}}_{\mathrm{entry}}}\times 100$

[0106] wherein Q.CO.sub.entry represents the molar flow of CO at the inlet of the reactor 6 expressed in mol/h and Q.CO.sub.exit represents the molar flow of CO at the outlet of the reactor 6 expressed in mol/h.

[0107] In an embodiment of the invention, the CO.sub.2 yield of the water-gas shift reaction is of at least 50%, preferably at least 60%, more preferably at least 65%.

[0108] The CO.sub.2 yield rate is calculated as follows:

[00003]${\mathrm{CO}}_2\mathrm{yield}\left(\%\right)=\frac{\left(Q.Math.{\mathrm{CO}}_{2_{\mathrm{exit}}}\right)}{\left(Q.Math.{\mathrm{CO}}_{\mathrm{entry}}\right)}\times 100$

[0109] wherein Q.CO.sub.entry represents the molar flow of CO at the inlet of reactor 6 expressed in mol/h and Q.CO.sub.2,exit represents the molar flow of CO.sub.2 at the outlet of the reactor 6 expressed in mol/h.

[0110] In a preferred embodiment of the invention, the second reactor 6 comprising catalyst X.sub.2 may be filled with an inert material to allow an efficient distribution of the gas into the second reactor before starting up the reactor for the water-gas shift reaction step. Suitable inert materials may be silicon carbide or alumina.

[0111] Advantageously, catalyst X.sub.2 and the inert material are placed in successive layers into the reactor.

[0112] In an embodiment of the invention, the residence time in the first reactor 2 ranges from 50 to 1000 seconds, preferably from 100 to 500 seconds, allowing the determination of the amount of catalyst X.sub.1 in the reactor 2.

[0113] The residence time is defined by the following formula:

[00004]$\mathrm{residence}\mathrm{time}=\frac{V_{\mathrm{cat}}}{D_{\mathrm{gas}}}\times \frac{P_{reac}}{P_{\mathrm{atm}}}$

[0114] wherein V.sub.cat represents the volume of catalyst X.sub.1 in the first reactor 2 expressed in m.sup.3, D.sub.gas represents the inlet gas flow rate of flow 1 expressed in Nm.sup.3/s, P.sub.reac and P.sub.atm respectively represent the pressure in the reactor 2 and the atmospheric pressure expressed in Pa.

[0115] In a preferred embodiment of the invention, a start-up phase of the first reactor 2 is performed before the implementation of the process of the invention. First, a gaseous flow comprising at least one compound of formula (I) and hydrogen is injected in the first reactor 2. The flow rate of the compound(s) of formula (I) in the gaseous flow 1 may range from 1 NI/h to 10 Nm.sup.3/h. The flow rate of hydrogen may range from 0.1 to 10,000 Nm.sup.3/h. During this start-up phase, the temperature is increased from ambient temperature to 400° C., preferably from 20° C. to 350° C. The duration of the start-up phase may range from 1 to 64 hours, preferably from 30 to 40 hours.

[0116] During all this start-up phase, the sulfur-containing gaseous flow 3 at the outlet of the first reactor 2 may be directed to a flare and/or to the second reactor 6 by using pipes and tubing that can either send the sulfur-containing gaseous flow 3 to the flare and/or to the second reactor 6.

[0117] In a preferred embodiment of the invention, a preparation step of catalyst X.sub.2 in the second reactor 6 is performed before the implementation of the process of the invention. The preparation step of catalyst X.sub.2 may include a drying step and/or a pre-activation step, preferably a drying step and a pre-activation step.

[0118] During the drying step, catalyst X.sub.2 may be dried under an inert gas flow, preferably a nitrogen gas flow. The inert gas flow rate may range from 0.1 to 10,000 Nm.sup.3/h. During the drying step, the temperature may increase from 20° C. to 200° C. The drying time may range from 1 to 10 hours, preferably 6 hours. The drying step is preferentially performed from ambient pressure to the preferred operated pressure between 15 to 25 bars.

[0119] During the pre-activation step, catalyst X.sub.2 may be sulphided. The reactor 6 may be treated under a hydrogen stream at a flow rate of 0.1 to 10,000 Nm.sup.3/h and at a pressure of, at least 10 bars, the preferred operated pressure between 15 to 25 bars. Then, hydrogen sulphide or the sulfur-containing gaseous flow 3 at the outlet of the first reactor 2 may be injected upflow at a flow rate of 1 NI/h to 10 Nm.sup.3/h into the hydrogen stream. The temperature of the reactor 6 may then be increased from 150° C. to 350° C. by any means known to the person skilled in the art. The time of pre-activation step may range from 1 to 64 hours. The hydrogen stream is preferably maintained during all the pre-activation step.

[0120] Another object of the invention relates to the use of at least one compound of formula (I), preferably dimethyl disulphide, in a process for the production of hydrogen-enriched synthesis gas by a catalytic water-gas shift reaction operated on a raw synthesis gas.

EXAMPLES

Example 1 (Comparative)

[0121] A water-gas shift reaction is carried out in a catalytic reactor 6′ of a pilot plant according to the following procedure.

[0122] 1) Preparation of Catalytic Reactor 6′

[0123] Catalytic reactor 6′ of 150 cm.sup.3 is filled at ambient pressure and ambient temperature with three layers of solids separated by metal grids, as follows: [0124] a first layer of 60 cm.sup.3 of silicon carbide of Carborundum type having a particle size of 1.680 mm: this inert material allows a satisfactory gas distribution, [0125] a second layer of 40 cm.sup.3 of a CoMo-based sulfur-resistant shift catalyst, [0126] a third layer of 50 cm.sup.3 of silicon carbide of Carborundum type having a particle size of 1.680 mm.

[0127] Catalytic reactor 6′ is then positioned into a furnace that can withstand a wide temperature ranging from 100 to 350° C. Catalytic reactor 6′ is connected at the inlet tubing to a gas feed and at the outlet tubing to an analyzer.

[0128] For the example, the CoMo-based sulfur-resistant shift catalyst is first dried by a nitrogen flow rate of 20 NI/h at ambient pressure. The drying temperature is set to 150° C. with a temperature ramp of +25° C./h.

[0129] The drying time is set to 1 hour.

[0130] A second step consists in sulfiding the CoMo-based sulfur-resistant shift catalyst to make it pre-active.

[0131] During this step, the reactor is treated under a hydrogen flow rate of 20 NI/h at a pressure of 35 bars. Then hydrogen sulphide is injected upflow at a flow rate of 0.5 NI/h into the hydrogen feed. The catalyst is then subjected to a temperature ramp of +20° C./h. The first plateau is set to 150° C. for 2 hours then the temperature is increased up to 230° C. with a temperature ramp of +25° C./h. A second plateau of 4 hours is maintained to 230° C. and then the temperature is increased again up to 350° C. with a temperature ramp of +25° C./h. A final plateau of 16 hours is performed at 350° C. The temperature was then dropped to 230° C. still under a hydrogen stream with a flow rate of 20 NI/h: the catalyst is thus pre-activated.

[0132] 2) Water-Gas Shift Reaction Step

[0133] The study of the conversion of carbon monoxide to carbon dioxide in the pre-activated CoMo-based sulfur-resistant shift catalyst is then carried out at 20 bars (2 MPa). Catalytic reactor 6′ is treated upflow with a synthesis gas mixture comprising hydrogen at a flow rate of 8.5 NI/h, carbon monoxide at 17 NI/h, water at 0.33 cm.sup.3/min and nitrogen at 26 NI/h at a pressure of 20 bars (2 MPa). The molar ratio H.sub.2O/CO is of 1.44 and the residence time is of 38 seconds. Hydrogen sulphide is injected upflow in the gas mixture at a flow rate of 0.5 NI/h. The inlet temperature of the gas entering the catalytic reactor 6′ is maintained to 310° C.

[0134] The CO and CO.sub.2 concentrations of the gas flow are measured by an infra-red spectroscopic analyzer connected at the outlet of catalytic reactor A in order to determine the CO conversion and the CO.sub.2 yield. A CO conversion rate of 92% and a CO.sub.2 yield of 95% are obtained, such a rate reflecting good performance of the water-gas shift reaction.

Example 2 (According to the Invention)

[0135] A water-gas shift reaction is carried out in a catalytic reactor 6 connected upstream to a catalytic reactor 2 according to the following procedure.

[0136] 1) Preparation of the Catalytic Reactors [0137] Catalytic reactor 6

[0138] With reference to FIG. 1, catalytic reactor 6 of 150 cm.sup.3 is filled at ambient pressure and ambient temperature with three layers of solids separated by metal grids, as follows: [0139] a first layer of 60 cm.sup.3 of silicon carbide of Carborundum type having a particle size of 1.680 mm: this inert material allows a satisfactory gas distribution, [0140] a second layer of 40 cm.sup.3 of a CoMo-based sulfur-resistant shift catalyst, [0141] a third layer of 50 cm.sup.3 of silicon carbide of Carborundum type having a particle size of 1.680 mm.

[0142] Catalytic reactor 6 is then positioned into a furnace that can handle a wide temperature ranging from 100 to 350° C. Catalytic reactor 6 is connected at the inlet tubing to a gas feed and at the outlet tubing to an analyzer.

[0143] For the example, the CoMo-based sulfur-resistant shift catalyst is first dried by a nitrogen flow rate of 20 NI/h at ambient pressure. The drying temperature is set to 150° C. with a temperature ramp of +25° C./h. The drying time is set to 1 hour.

[0144] A second step consists in sulfiding the CoMo-based sulfur-resistant shift catalyst to pre-activate it. During this step, the reactor is treated under a hydrogen flow rate of 20 NI/h at a pressure of 35 bars. Then hydrogen sulphide is injected upflow at a flow rate of 0.5 NI/h into the hydrogen feed. The catalyst is then subjected to a temperature ramp of 20° C./h. The first plateau is set to 150° C. for 2 hours then the temperature is increased up to 230° C. with a temperature ramp of +25° C./h. A second plateau of 4 hours is maintained to 230° C. and then the temperature is increased again up to 350° C. with a temperature ramp of +25° C./h. A final plateau of 16 hours is performed at 350° C. The temperature was then dropped to 230° C. still under a hydrogen stream with a flow rate of 20 NI/h: the catalyst is thus pre-activated.

[0145] Catalytic Reactor 2

[0146] Catalytic reactor 2 of volume equal to 150 cm.sup.3 is filled at ambient pressure and ambient temperature with three layers of solids separated by metal grids, as follows: [0147] a first layer of 60 cm.sup.3 of silicon carbide of Carborundum type having a particle size of 1.680 mm: this inert material allows a satisfactory gas distribution, [0148] a second layer of 40 cm.sup.3 of a Al.sub.2O.sub.3 supported CoMo-based catalyst containing 15 wt % Mo and 3 wt % Co, [0149] a third layer of 50 cm.sup.3 of silicon carbide of Carborundum type having a particle size of 1.680 mm.

[0150] The start-up phase of catalytic reactor 2 consists in placing this reactor filled as explained previously in a furnace and then treating it under a hydrogen flow rate of 20 NI/h at a pressure of 25 bars (2.5 MPa). Dimethyl disulphide (DMDS) is injected in the liquid state upflow at 1 cm.sup.3/h in the hydrogen stream 1. The Al.sub.2O.sub.3 supported CoMo-based catalyst is subjected to a temperature ramp of +20° C./h. The first plateau is set to 150° C. for 2 hours then temperature is increased up to 230° C. with a temperature ramp of +25° C./h. A second plateau of 4 hours is maintained to 230° C. and then temperature is increased again up to 350° C. with a temperature ramp of +25° C./h. A final plateau of 16 hours is performed at 350° C. The temperature is then lowered to 310° C. by still maintaining a flow rate of 1 cm.sup.3/h of DMDS and the pressure at 25 bars (2.5 MPa). The rate of hydrogen is decreased to 8.5 NI/h. The reactor 2 start-up phase is thus ended.

[0151] During all this start-up phase, the sulfur-containing gaseous mixture 3 from the catalytic reactor 2 is directed to a flare and/or to the second reactor 6 by using pipes and tubing that can either send the gaseous mixture to the flare and/or to the reactor 6.

[0152] 2) Water-Gas Shift Reaction Step

[0153] The study of the conversion of carbon monoxide to carbon dioxide in the pre-activated sulphur-resistant shift catalyst is then carried out at 20 bars (2 MPa). Catalytic reactor 6 is treated upflow with a gaseous mixture 4 comprising carbon monoxide at 17 NI/h, water at 0.33 cm.sup.3/min and nitrogen at 26 NI/h at a pressure of 20 bars. Except during the start-up phase of catalytic reactor 2, the sulfur-containing gaseous mixture 3 exiting reactor 2 is then injected into the gaseous mixture 4, the resulting gaseous mixture 5 being introduced in catalytic reactor 6. The inlet temperature of the gas entering the catalytic reactor 6′ is maintained to 310° C. The molar ratio H.sub.2O/CO is of 1.4 and the residence time is of 38 seconds.

[0154] The CO and CO.sub.2 concentrations of the gaseous flow are measured by an infra-red spectroscopic analyzer connected at the outlet line 7 of catalytic reactor 6 in order to determine the CO conversion and the CO.sub.2 yield.

[0155] A CO conversion rate of 92% and a CO.sub.2 yield of 95% are obtained reflecting good performance of the water-gas shift reaction, equivalent to that obtained with H.sub.2S as the activating agent in example 1. Therefore, DMDS is as efficient as H.sub.2S in a process for the catalytic water-gas shift reaction.

[0156] The process using at least one compound responding to formula (I) as defined in the present invention instead of gaseous hydrogen sulphide is therefore as efficient, safer and easier to implement.