Method for preparing mercaptans by sulfidation hydrogenolysis of thioethers

Abstract

The present invention relates to a process for the hydrogenolysis of dialkyl sulfides with hydrogen sulfide (H2S) in the presence of a specific catalyst based on ZrO2 and / or TiO2, and the corresponding use of such a catalyst. The invention also relates to a process for the preparation of mercaptans, in particular methyl mercaptan, from at least one alcohol and hydrogen sulfide, which comprises the hydrogenolysis reaction.

Description

[0001] The present invention relates to a process for preparing mercaptans, in particular methyl mercaptan, from dialkyl sulfides and hydrogen sulfide in the presence of specific catalysts based on titanium dioxide and / or zirconium dioxide (also known as the sulfhydrolyse process or reaction), and to the corresponding use of such catalysts.

[0002] The invention also relates to a process for the preparation of mercaptans and dialkyl sulfides from at least one alcohol and hydrogen sulfide, comprising the hydrogenosulfide process as defined above.

[0003] Mercaptans are of great industrial interest and are currently widely used in the chemical industry, particularly as starting materials for the synthesis of more complex organic molecules. For example, methyl mercaptan (CH 3 Methyl mercaptan (SH) is used as a raw material in the synthesis of methionine, an essential amino acid for animal feed. Methyl mercaptan is also used in the synthesis of dialkyl disulfides, in particular dimethyl disulfide (DMDS), a sulfiding additive for petroleum fraction hydroprocessing catalysts, and other applications.

[0004] The industrial synthesis of mercaptans, in particular methyl mercaptan, is generally carried out according to known methods from alcohols and hydrogen sulfide at high temperatures in the presence of a catalyst according to the following equation (1):

[0005] Main reaction

[0006] ROH+H 2 S→RSH+H 2 O (1).

[0007] However, this reaction produces byproducts such as thioethers (symmetric in the following case), according to the following equation (2):

[0008] ROH+RSH→RSR+H 2 O (2).

[0009] In addition, when the main reaction is carried out in the presence of multiple alcohols, asymmetric sulfide can also be obtained according to the following equations (3) and (4) (taking two alcohols as an example):

[0010] ROH+R'OH+2H 2 S→RSH+R'SH+2H 2 O (3)

[0011] ROH+R'SH→RSR'+H 2 O (4).

[0012] Symmetrical or asymmetrical sulfides are obtained industrially in large quantities and are mainly sent for destruction. This represents a loss of efficiency in the mercaptan production process and additional costs associated with their destruction.

[0013] Therefore, thioethers are sometimes further valorized to the corresponding thiols by the following reaction (5), also known as sulfidation hydrogenolysis:

[0014] Hydrosulfide decomposition reaction

[0015] RSR'+H 2 S→RSH+R'SH (5).

[0016] In the case of methyl mercaptan, the sulfidation hydrogenolysis reaction is written according to the following equation (6):

[0017] CH 3 SCH 3 +H 2 S→2CH 3 SH (6).

[0018] As described in patent applications WO 2017 / 210070 and WO 2018 / 035316, the sulfide hydrogenation reaction is usually carried out using an alumina-based (Al 2 O 3 ) or NiMo (nickel / molybdenum) or CoMo (cobalt / molybdenum) type catalysts are used for catalysis.

[0019] However, such methods need to be improved to be more economical and more suitable for industrial scale.

[0020] Therefore, there is a need for an improved process for the hydrosulfidation of sulfides to mercaptans, in particular the hydrosulfidation of dimethyl sulfide to methyl mercaptan.

[0021] There is also a need for a process for improving the valorization of sulfides, particularly dimethyl sulfide, which is a by-product during the production of mercaptans produced from alcohols and hydrogen sulfide.

[0022] An object of the present invention is to provide a catalyst for the sulfidation hydrogenolysis of thioethers to mercaptans which is easy to use, economical and has a satisfactory conversion rate.

[0023] Another object of the present invention is to provide a process for the sulfidation and hydrogenolysis of thioethers to form mercaptans, which process can be easily integrated into an apparatus for the industrial production of mercaptans, in particular from alcohols and H 2 S in equipment for producing mercaptans.

[0024] An object of the present invention is to provide a process for preparing mercaptans, wherein the thioether by-product (e.g. 2 S) is recovered or economically added value during the reaction between them, which is easy to use and industrially feasible.

[0025] The inventors surprisingly found that the use of titanium dioxide (formula TiO 2) and / or zirconium oxide (also known as zirconium dioxide, formula ZrO 2 ) allows obtaining good conversions of thioethers, in particular at least 36%, preferably at least 50%, or even at least 70%. In addition, methane as a by-product of sulfide hydrogenolysis is produced with very low selectivity (e.g., less than 2%).

[0026] The catalysts according to the invention are known as inert catalytic supports (ie supports without catalytic activity). They are therefore simple, economical and less hazardous compositions, which allow obtaining a more efficient and environmentally friendly process for hydrogenolysis of sulphide.

[0027] In particular, the sulfide hydrogenolysis process according to the invention can be integrated into a plant for the industrial production of mercaptans, which are composed in particular of at least one alcohol and H 2 S production. The sulfide hydrogenolysis process according to the invention now allows the productivity of mercaptans to be increased in a simple and economical manner by valorizing the by-product sulfides during the main reaction and converting them also into mercaptans.

[0028] Furthermore, surprisingly, the present inventors have also found that mercaptans derived from sulfidation hydrogenolysis and unreacted H 2 S can be directly reintroduced (in particular without separation and / or purification steps) into the main reactor, and this will not affect the reaction between alcohol and H. 2 The main reactions between S have an impact.

[0029] The mercaptans produced by both reactions (main reaction and hydrogenolysis reaction) can now be separated and / or purified and / or recovered at a single location, for example at the outlet of the main reactor.

[0030] This integration of the hydrogenosulfide lysis process into the main mercaptan production chain can be achieved by having a single H for both the main reaction and the hydrogenosulfide lysis reaction. 2 S feed (e.g. at the inlet of the sulfide hydrogenolysis reactor).

[0031] Thus, according to the invention, a simple and efficient thioether valorization process fully integrated into the industrial production chain of mercaptans is obtained. The plant is particularly easy to implement: it can be easily connected to a main plant and requires only minimal modifications thereto.

[0032] The present invention therefore relates to a sulfide hydrogenolysis process, wherein a sulfide, preferably a dialkyl sulfide, is reacted in the presence of ZrO 2 and / or TiO 2 In the presence of hydrogen sulfide (H 2 S) to obtain at least one thiol, preferably one thiol.

[0033] The present invention also relates to a method for preparing mercaptan, comprising the following steps:

[0034] - is composed of at least one alcohol and H 2 S to prepare mercaptans and dialkyl sulfides, and

[0035] - the dialkyl sulfide produced by the sulfide hydrogenolysis method according to the present invention is reacted with H 2 S to obtain the thiol.

[0036] definition

[0037] the term" catalyst ” refers especially to a substance or combination of chemicals that accelerates a chemical reaction and remains unchanged at the end of that reaction.

[0038] According to the present invention, the catalyst used during the sulfide hydrogenolysis reaction comprises titanium dioxide (TiO 2 ) and / or zirconium oxide (ZrO 2 ), preferably titanium dioxide. Such catalysts may also be referred to as catalysts based on titanium dioxide and / or zirconium oxide.

[0039] Titanium dioxide and / or zirconium oxide are used as catalysts in the sulfide hydrogenolysis reaction. It is understood that TiO 2 and / or ZrO 2 The active component of the catalyst (ie the compound having catalytic activity). In particular, the catalyst according to the invention does not contain any other compound having catalytic activity towards the hydrogen sulfide decomposition reaction.

[0040] Preferably, the catalyst according to the invention consists essentially of or even consists of titanium dioxide and / or zirconium oxide and optionally of stabilizers and / or binders. Stabilizers and binders are those commonly used in the catalyst field.

[0041] the term" Accelerator ” (also known as “ Dopant ”) is a chemical substance or combination of chemical substances that can change and significantly increase the catalytic activity of a catalyst. For example, the term “ Accelerator " refers to a chemical substance or a combination of chemical substances that allows to improve the conversion and / or selectivity of the catalyzed reaction relative to the catalyst alone. Preferably, the catalyst according to the invention does not contain any promoter.

[0042] Common definitions of conversion, selectivity, and yield are as follows:

[0043] Conversion rate = (the number of moles of reagent in the initial state - the number of moles of reagent remaining after the reaction) / (the number of moles of reagent in the initial state;

[0044] Selectivity = number of moles of reagent converted to desired product / (number of moles of reagent in initial state - number of moles of reagent remaining after reaction);

[0045] Yield = conversion × selectivity.

[0046] In particular, the sulfide hydrogenolysis catalyst according to the invention allows obtaining sulfide conversions ranging from 30% to 90%, preferably from 50% to 80%, even more preferably from 50% to 75%.

[0047] The selectivity of the hydrogenosulfide reaction towards mercaptans is in particular greater than or equal to 98%.

[0048] Thioethers and mercaptans

[0049] The term "thioether" refers to any organic compound containing a -CSC- functional group.

[0050] Preferably, the term "thioether" refers to dialkyl sulfide.

[0051] The term "dialkyl sulfide" refers in particular to compounds of the following general formula (I):

[0052] RSR' (I)

[0053] wherein R and R' are identical or different and are independently a saturated, linear, branched or cyclic, optionally substituted hydrocarbon group.

[0054] Preferably, R and R' are identical or different and are independently linear or branched alkyl; more preferably, linear or branched, preferably linear alkyl, containing 1-18 carbon atoms, preferably 1-12 carbon atoms.

[0055] R and R' are the same or different and can be independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl, and isomers thereof. Preferably, R and R' are the same or different and can be independently selected from methyl, ethyl, octyl and dodecyl.

[0056] Preferably, R and R' are identical (which corresponds to a symmetrical dialkyl sulfide).

[0057] Symmetrical dialkyl sulfides have, in particular, the following general formula (II):

[0058] RSR (II)

[0059] wherein R is as defined above.

[0060] In particular, the dialkyl sulfide according to the invention is selected from dimethyl sulfide, diethyl sulfide, dioctyl sulfide, didodecyl sulfide and methyl ethyl sulfide. The dialkyl sulfide according to the invention may be selected from dimethyl sulfide, diethyl sulfide, dioctyl sulfide and didodecyl sulfide. Most particularly preferably, the dialkyl sulfide is dimethyl sulfide.

[0061] Mercaptans according to the invention are those which correspond to the sulfidic hydrogenolysis of thioethers as defined above. Preferably, the term "mercaptan" refers to alkyl mercaptans.

[0062] In particular, the term "alkylthiol" refers to compounds of the following general formula (III) and / or (IV):

[0063] R-SH (III) and / or R'SH (IV),

[0064] wherein R and R' are as defined above.

[0065] Particularly preferably, the mercaptan obtained according to the invention is methyl mercaptan.

[0066] Method for sulfide hydrogenolysis to mercaptan

[0067] The present invention therefore relates to a process for preparing at least one mercaptan by sulfidation hydrogenolysis. In particular, the present invention relates to a process for preparing at least one mercaptan, wherein a dialkyl sulfide is reacted with hydrogen sulfide (H 2 S) in ZrO as catalyst 2 and / or TiO 2 There is a reaction.

[0068] Preferably, the catalyst does not contain any alkali metal oxides, in particular oxides of lithium, sodium, potassium, rubidium and cesium.

[0069] Preferably, the catalyst does not contain a promoter.

[0070] In particular, the catalyst does not contain aluminum oxide (Al 2 O 3 ).

[0071] In particular, the catalyst does not contain phosphorus.

[0072] Preferably, the catalyst is TiO 2 Particularly preferably, the catalyst comprises only TiO 2 As the active ingredient, it is particularly in the form of anatase crystals.

[0073] When the catalyst contains TiO 2 and / or ZrO 2When the catalyst is used, it may contain 30% to 50%, preferably 35% to 45%, for example about 40% by weight of TiO 2 , and / or 50 wt % to 70 wt %, preferably 55 wt % to 65 wt %, for example about 60 wt % of ZrO relative to the total weight of the catalyst 2 .

[0074] The catalyst according to the invention may have a molecular weight greater than 40 m 2 .g -1 Preferably, for ZrO-based 2 The catalyst has a specific area of ​​at least 50m 2 .g -1 Preferably, for TiO-based 2 The catalyst has a specific area of ​​at least 80m 2 .g -1 .

[0075] The catalyst may be in any type of form, such as spheres, cylinders, rings or stars, in the form of granules or any other three-dimensional form, or may be in the form of a powder, which may be pressed, extruded or pelletized.

[0076] The hydrogen sulfide lyzing agent may be gaseous, liquid or solid, preferably gaseous or liquid.

[0077] The reaction temperature of the hydrogen sulfide decomposition may be between 100°C and 500°C, preferably between 200°C and 400°C, more preferably between 200°C and 380°C and more preferably between 250°C and 380°C.

[0078] The sulfide hydrogenolysis reaction can be carried out at a pressure between 50 mbar and 100 bar, preferably between atmospheric pressure (about 1 bar) and 50 bar, and advantageously between 5 bar and 20 bar.

[0079] H 2 The S / sulfide molar ratio may be between 0.1 / 1 and 50 / 1, preferably between 2 / 1 and 20 / 1. Preferably, the ratio is between 2 / 1 and 15 / 1, more preferably between 2 / 1 and 10 / 1, such as 4 / 1.

[0080] Advantageously, the reagent (thioether and H 2 S) can comply with a specific contact time with the catalyst in the reactor where the hydrogen sulfide decomposition occurs. This parameter is expressed by the time-space velocity equation:

[0081] (HSV) = (total flow of sulfide + incoming H 2 S) / (volume of catalyst in reactor).

[0082] HSV can be included in 100-1200h -1 between.

[0083] The sulfide hydrogenolysis reaction can be carried out in any type of reactor, for example a fixed bed tubular reactor, a multitubular reactor, a reactor with microchannels, a catalytic wall or a fluidized bed, preferably a fixed bed tubular reactor.

[0084] In particular, the sulphide hydrogenolysis process according to the invention is carried out in a reactor comprising only one catalytic zone, said zone being in particular continuous.

[0085] The amount of each reagent supplied to the reactor may vary depending on the reaction conditions (eg, temperature, hourly space velocity, etc.) and is determined according to general knowledge. Hydrogen sulfide may be present in excess.

[0086] Method for producing mercaptans

[0087] The present invention relates to a method comprising at least one alcohol and H 2 S process for preparing mercaptans and dialkyl sulfides, wherein the one or more dialkyl sulfides produced are then reacted with H according to the sulfidation hydrogenolysis process as defined above 2 S to obtain the one or more thiols.

[0088] Therefore, the present invention relates to a method for preparing mercaptan, comprising the following steps:

[0089] - is composed of at least one alcohol and H 2 S to prepare mercaptans and dialkyl sulfides, and

[0090] - according to the sulfidation hydrogenolysis method defined above, the dialkyl sulfide produced is reacted with H 2 S to obtain the thiol.

[0091] Alcohol and H 2 The reaction between H and S to form mercaptans (and thioethers as by-products) is a known reaction, for example described in patents US2820062A, US7645906B2 and US2820831A. For example, the reaction can be carried out at a temperature between 200°C and 450°C and / or a pressure range from negative pressure to 100 bar. Typically, a catalyst is present, such as aluminum oxide promoted by an alkali metal and / or alkaline earth metal. H 2 S may be present in excess.

[0092] Among these reagents, at least one alcohol, preferably one or two alcohols, may be used. Preferably, only one alcohol is used. The alcohol may be selected from (C 1 -C 18 ) or even (C 1 -C 12) alcohol, and mixtures thereof. In particular, the alcohol may be selected from methanol, ethanol, octanol, dodecanol and mixtures thereof. Preferably, the alcohol used is methanol.

[0093] Hereinafter, it is to be understood that when two streams are introduced into a reactor, they may each be introduced into the reactor separately, or may be combined before they are introduced into the reactor.

[0094] In particular, the method according to the invention comprises the following steps:

[0095] A) will include H 2 S and a stream comprising at least one alcohol are introduced into a first reactor;

[0096] B) reacting the two streams to obtain a mixture comprising at least one mercaptan, at least one dialkyl sulfide and optionally H 2 The outlet stream of S;

[0097] C) separating the outlet stream obtained in step B) into:

[0098] - a stream comprising mercaptans,

[0099] - a stream comprising dialkyl sulfides, and

[0100] -Optionally contains H 2 S material flow;

[0101] D) mixing the stream comprising dialkyl sulfide with H 2 S streams are introduced into the second reactor together;

[0102] E) reacting the two streams according to the sulfidation hydrogenolysis process as defined above to obtain a stream comprising said mercaptans and optionally H 2 The outlet stream of S;

[0103] F) optionally removing the H obtained in step C) 2 The S stream is recycled into step A).

[0104] The mercaptans can be recovered at the end of step C) and / or after separation from the outlet stream of step E), preferably at the end of step C).

[0105] The outlet stream obtained from step B) may comprise at least one mercaptan, at least one dialkyl sulfide, optionally water, unconverted alcohol and H 2 S. The outlet stream obtained from step E) may comprise the mercaptans, H 2 S and optionally methane and unconverted dialkyl sulfide.

[0106] The outlet stream from the second reactor of step E) can be recycled, preferably completely, to the first reactor of step A). ​​Thus, the outlet stream comprising mercaptans and optionally H 2 The outlet stream from the sulfide hydrogenolysis process comprising H S is introduced directly into the main reactor (or first reactor), in particular without a prior separation and / or purification step. In particular, the outlet stream from the second reactor of step E) may correspond completely or partially, preferably completely, to the outlet stream from step A) comprising H 2 A stream of S (optionally with recycled H obtained from step C) 2 S). In this case, the outlet stream obtained from step E) comprises H 2 S.

[0107] Surprisingly, the introduction of mercaptans into the main reactor had a significant effect on the 2 There is no influence on the main reaction between S. In addition, H obtained from step E) can be 2 S is thus completely recycled to step A). ​​This recycling has the particular advantage that only one H 2 Advantages of S inlet, for example at the inlet of a hydrogenosulfide decomposition reactor.

[0108] Integration of the sulfide hydrogenolysis process according to the invention into an industrial production plant for mercaptans thus makes it possible to completely reprocess the sulfide by-products into products of interest and to advantageously recycle the H 2 S. The mercaptans produced will be the result of the main reaction and the sulfide hydrogenolysis reaction, thereby increasing the productivity.

[0109] The separation step C) can be carried out according to conventional methods by distillation, for example under reduced pressure. For example, the distillation can be carried out at a pressure between 0.1 bar and 10 bar, in particular between 1 bar and 10 bar. Step C) allows in particular the outlet stream obtained from step B) to be separated into:

[0110] - a stream comprising mercaptans,

[0111] - a stream comprising dialkyl sulfides,

[0112] -Optionally contains H 2 S material flow,

[0113] - optionally a stream comprising methane,

[0114] - optional water,

[0115] - optionally unconverted alcohol.

[0116] According to a specific embodiment, the preparation method comprises the following steps:

[0117] a) will contain thiols and H 2 S and a stream comprising at least one alcohol, preferably one alcohol, are introduced into a first reactor;

[0118] b) reacting the two streams to obtain a mixture comprising mercaptans, dialkyl sulfides and optionally H 2 The outlet stream of S;

[0119] c) separating the outlet stream obtained from step b) into:

[0120] - a stream comprising mercaptans;

[0121] - a stream comprising dialkyl sulfides; and

[0122] -Optionally contains H 2 S material flow;

[0123] d) mixing a stream comprising dialkyl sulfide with H 2 S streams are introduced into the second reactor together;

[0124] e) reacting the two streams according to the sulfide hydrogenolysis process defined above to obtain a stream comprising mercaptans and H 2 The outlet stream of S;

[0125] f) introducing the outlet stream obtained from step e), preferably directly into the reactor of step a);

[0126] g) optionally recovering a stream comprising mercaptans obtained from step c); and

[0127] h) optionally removing the H obtained in step c) 2 The S stream is recycled into step a).

[0128] The outlet stream from step f) may correspond completely or partly, preferably completely, to the mercaptans and H 2 The inlet flow of S.

[0129] According to another specific embodiment, the preparation method comprises the following steps:

[0130] a') will contain H 2 S and a stream comprising at least one alcohol, preferably one alcohol, are introduced into a first reactor;

[0131] b') reacting the two streams to obtain a mixture comprising mercaptans, dialkyl sulfides and optionally H 2 The outlet stream of S;

[0132] c') separating the outlet stream obtained from step b') into:

[0133] - a stream comprising mercaptans;

[0134] - a stream comprising dialkyl sulfides; and

[0135] -Optionally contains H 2 S material flow;

[0136] d') optionally recovering the mercaptan-containing stream obtained from step c');

[0137] e') optionally removing the H obtained in step c') 2 The S stream is recycled into step a');

[0138] f') mixing the dialkyl sulfide-containing stream with H 2 S streams are introduced into the second reactor together;

[0139] g') reacting the two streams according to the sulfide hydrogenolysis process defined above to obtain a stream comprising mercaptans and H 2 The outlet stream of S;

[0140] h') separating the outlet stream obtained in step g') into:

[0141] - a stream comprising mercaptans;

[0142] -Contains H 2 S material flow;

[0143] i') combining the mercaptan-comprising stream obtained from step h') with the outlet stream from step b') before and / or during step c');

[0144] j') optionally treating the H obtained in step h') 2 The S stream is recycled into step f').

[0145] This embodiment provides, inter alia, that the H 2 Independence of the S feed to the sulfide hydrogenolysis reactor.

[0146] The present invention also relates to ZrO 2 and / or TiO 2 Use as a catalyst in a reaction in which a thioether is reacted with hydrogen sulfide to obtain a mercaptan. In particular, the catalyst and the reaction are as defined for the sulfide hydrogenolysis process as described above. The thioether and mercaptan are also as defined above. BRIEF DESCRIPTION OF THE DRAWINGS

[0147] Figure 1 A methyl mercaptan production plant incorporating a sulphide hydrogenolysis process according to the invention is schematically shown. The production equipment may be pre-existing and may correspond to the elements enclosed by the dashed line.

[0148] The secondary reactor (1) (where the hydrogen sulfide decomposition occurs) includes an H2 S inlet and a dimethyl sulfide (DMS) inlet. At the outlet, stream A contains H 2 S and methyl mercaptan.

[0149] Stream A is fed directly to the main reactor (2) which also includes a methanol inlet. The outlet stream B from reactor (2) contains methyl mercaptan, dimethyl sulfide and H 2 S.

[0150] Stream B is then separated by distillation (3) into three different streams:

[0151] - a stream comprising methyl mercaptan (MeSH);

[0152] - a stream comprising dimethyl sulfide (DMS); and

[0153] -Contains H 2 A stream of S is then recycled to reactor (2) (not shown).

[0154] The DMS stream is then recycled into the reactor (1).

[0155] Figure 2 Another embodiment of a methyl mercaptan production plant incorporating the hydrogenolysis process according to the invention is schematically shown. The production equipment may be pre-existing and may correspond to the elements enclosed by the dashed line.

[0156] The secondary reactor (1A) (where the hydrogen sulfide decomposition occurs) includes H 2 S inlet and dimethyl sulfide (DMS) inlet. At the outlet, stream A contains H 2 S and methyl mercaptan.

[0157] Stream A undergoes a distillative separation step in (1B), which produces H which is recycled to reactor (1A). 2 S stream and a stream BC comprising methyl mercaptan which is combined at (3) with the outlet stream of reactor (2), wherein the main reaction occurs between methanol and H 2 Between S.

[0158] The distillation separation step (3) produces two different streams:

[0159] - a stream comprising methyl mercaptan (MeSH);

[0160] - a stream comprising dimethyl sulfide (DMS).

[0161] The DMS stream is then recycled to the reactor (1A).

[0162] Figure 3The selectivity (in percent) for thioethers is presented as a function of the mass percentage of mercaptans in the feed entering the main synthesis reactor for mercaptans at three different reaction temperatures. Example

[0163] Example 1 :Method for the sulfidation and hydrogenolysis of dimethyl sulfide (DMS) to methyl mercaptan (MeSH)

[0164] Prior to testing, the catalyst was dried using a first step consisting of nitrogen at 250 °C and subsequently H 2 The activation was carried out in situ by curing for 1 hour.

[0165] The performance of the catalyst was evaluated in a fixed bed reactor containing only one catalytic zone (with a catalyst volume of 30 mL) for the production of MeSH from DMS at a temperature of 300°C to 350°C and a pressure of 9 bar absolute with a feed gas composition of DMS / H 2 S = 1 / 4 (v / v) and 800h -1 The reagents are preheated to a temperature >100°C and flash evaporated during their introduction into the bottom of the reactor.

[0166] The products were analyzed online by gas chromatography.

[0167] The DMS conversion and the conversion of MeSH and CH 4 The selectivity results are described in Table 1 below:

[0168] .

[0169] It is noted that the catalyst according to the invention allows a significant increase in the conversion of dimethyl sulfide while maintaining a very good selectivity. In particular, using the catalyst according to the invention, the conversion can be greater than 70%, relative to a maximum of 35% for conventional catalysts of alumina for sulfide hydrogenolysis.

[0170] It was observed that only negligible amounts of methane were formed.

[0171] Example 2 :Production of mercaptans

[0172] The effect of the sulfide hydrogenolysis reaction on the main mercaptan synthesis reaction was evaluated.

[0173] For this purpose, as the feed to reactor 1 (which consists of alcohol and H 2 The sulfide content produced by the main synthesis reaction of mercaptans was monitored as a function of the change in the mercaptan content in S (production of mercaptans).

[0174] The main reaction conditions are as follows:

[0175] Pressure = 3.5 bar

[0176] H 2 S / ethanol ratio (molar) = 2.4

[0177] GHSV=580h -1

[0178] Figure 3 The selectivity results for thioethers at three incoming mercaptan contents at three different temperatures using an alumina-based catalyst are described.

[0179] like Figure 3 As shown, the selectivity of the co-produced sulfide during the main mercaptan synthesis reaction (reactor 1) is independent of the incoming mercaptan content obtained from the sulfidation hydrogenolysis reaction. It is thus demonstrated that the presence of mercaptans has no influence on the main synthesis reaction.

Claims

1. A sulfide hydrogenolysis process, wherein a dialkyl sulfide is reacted with hydrogen sulfide (H2S) in the presence of ZrO2 and / or TiO2 as a catalyst to obtain at least one mercaptan; wherein the catalyst does not contain Al2O3 and phosphorus.

2. The process according to claim 1, wherein the catalyst does not contain alkali metal oxides.

3. The process according to claim 1 or 2, which is carried out in a reactor comprising only one catalytic zone.

4. The method according to any one of claims 1 to 2, wherein the hydrogen sulfide decomposition reaction temperature is 100°C-500°C.

5. The process according to any one of claims 1 to 2, wherein the H2S / dialkyl sulfide molar ratio is from 0.1 / 1 to 50 / 1.

6. The method according to any one of claims 1 to 2, wherein the dialkyl sulfide is selected from the group consisting of dimethyl sulfide, diethyl sulfide, dioctyl sulfide, didodecyl sulfide and methyl ethyl sulfide.

7. The process according to any one of claims 1 to 2, wherein the catalyst does not contain any other compounds which are catalytically active towards the hydrogen sulfide decomposition reaction.

8. A method for preparing mercaptan, comprising the following steps: - preparation of mercaptans and dialkyl sulfides from at least one alcohol and H2S, and - reacting the one or more dialkyl sulfides produced with H2S according to the sulfidation hydrogenolysis process as defined in any one of claims 1 to 7 to obtain the mercaptan.

9. The method according to claim 8, comprising the steps of: A) introducing a stream comprising H2S and a stream comprising at least one alcohol into a first reactor; B) reacting the two streams to obtain an outlet stream comprising at least one mercaptan, at least one dialkyl sulfide and optionally H2S; C) separating the outlet stream obtained in step B) into: - a stream comprising said mercaptans, - a stream comprising said dialkyl sulfide, and - optionally a stream comprising H2S; D) introducing a stream comprising dialkyl sulfide into a second reactor together with a stream of H2S; E) reacting the two streams according to a sulphide hydrogenolysis process as defined in any one of claims 1 to 7 to obtain an outlet stream comprising the mercaptans and optionally H2S; F) optionally recycling the H2S stream obtained in step C) into step A).

10. The process according to claim 9, wherein the outlet stream from the second reactor in step E) is recycled into the first reactor in step A).

11. The method according to claim 8, comprising the steps of: a) introducing a stream comprising mercaptans and H2S and a stream comprising alcohols into a first reactor; b) reacting the two streams to obtain an outlet stream comprising mercaptans, dialkyl sulfides and optionally H2S; c) separating the outlet stream obtained from step b) into: - a stream comprising said mercaptans; - a stream comprising the dialkyl sulfide; and - optionally a stream comprising H2S; d) introducing a stream comprising the dialkyl sulfide into a second reactor together with a H2S stream; e) reacting the two streams according to the sulphide hydrogenolysis process as defined in any one of claims 1 to 7 to obtain an outlet stream comprising mercaptans and H2S; f) introducing the outlet stream obtained from step e) into the reactor of step a); g) optionally recovering the stream comprising said mercaptans obtained from step c); and h) optionally recycling the H2S stream obtained in step c) into step a).

12. Use of ZrO2 and / or TiO2 as catalyst in the reaction of dialkyl sulfides with hydrogen sulfide to obtain mercaptans; wherein the catalyst does not contain Al2O3 and phosphorus.

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