EP4041708A1

EP4041708A1 - Method for preparing mercaptans by sulfhydrolysis of sulfides

Info

Publication number: EP4041708A1
Application number: EP20797157.3A
Authority: EP
Inventors: Georges Fremy; Hélori SALEMBIER; Guillaume LAUDUMIEY
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2019-10-04
Filing date: 2020-09-28
Publication date: 2022-08-17
Also published as: US20240025847A1; WO2021064312A1; FR3101631A1; CN114728896A; FR3101631B1

Abstract

The present invention concerns a method for sulfhydrolysis from dialkyl sulfides and hydrogen sulfide, in the presence of a specific catalyst based on titanium dioxide and/or zirconium dioxide, as well as the corresponding use of such a catalyst. The present invention also concerns a method for preparing mercaptans, in particular methyl mercaptan, from at least one alcohol and hydrogen sulfide, comprising said sulfhydrolysis method.

Description

PROCESS FOR PREPARING MERCAPTANS BY SULPHYDROLYSIS OF

SULPHIDES

The present invention relates to a process for preparing mercaptans, in particular methylmercaptan, from dialkylsulfides and hydrogen sulfide (also called sulfhydrolysis process or reaction), in the presence of a specific catalyst based on titanium dioxide and / or zirconium dioxide, as well as the corresponding use of such a catalyst. The present invention also relates to a process for preparing mercaptans and dialkylsulfides, from at least one alcohol and hydrogen sulfide, integrating the sulfhydrolysis process as defined above.

Mercaptans are of great industrial interest and are now widely used by the chemical industries, in particular as raw materials for the synthesis of more complex organic molecules. For example, methylmercaptan (CH ₃ SH) is used as a raw material in the synthesis of methionine, an essential amino acid for animal feed. Methylmercaptan is also used in the synthesis of dialkyl disulphides, in particular in the synthesis of dimethyl disulphide (DMDS), a sulphurization additive of hydrotreatment catalysts of petroleum fractions, among other applications.

The industrial synthesis of mercaptans, and in particular of methyl mercaptan, is generally carried out according to a known process, from an alcohol and hydrogen sulfide at elevated temperature in the presence of a catalyst according to equation (1) below:

Main reaction R0H + H ₂ S -> RSH + H ₂ 0 (1)

However, this reaction gives rise to the formation of by-products, such as sulphides (which in the case below are symmetrical), according to the following equation (2):

ROH + RSH -> RSR + H ₂ 0 (2)

In addition, when the main reaction is carried out in the presence of several alcohols, it is also possible to obtain unsymmetrical sulphides according to the following equations (3) and (4) (example given with two alcohols):

ROH + R'OH + 2H ₂ S -> RSH + R'SH + 2H ₂ 0 (3)

ROH + R'SH -> RSR '+ H ₂ 0 (4)

The sulphides by-products, symmetrical or not, are obtained in large quantities at the industrial level and are mainly brought to be destroyed. This represents a loss of efficiency for the mercaptan production process and an additional cost associated with their destruction.

Thus, the sulfides are sometimes upgraded to obtain the corresponding mercaptans, thanks to the following reaction (5) (also called sulfhydrolysis): RSR '+ H ₂ S -> RSH + R'SH sulfhydrolysis reaction (5)

In the case of methylmercaptan, the sulfhydrolysis reaction is written according to equation (6):

CH ₃ SCH ₃ + H ₂ S -> 2 CH ₃ SH (6)

The sulfhydrolysis reaction is generally catalyzed by catalysts of alumina type (Al ₂ 0 ₃ ) OR of NiMo type (Nickel / Molybdenum) or C0M0 (Cobalt / Molybdenum) on an alumina support as described in applications WO 2017/210070 and WO 2018/035316. However, such a process needs to be improved so as to be more economical and more suitable for the industrial scale.

There is therefore a need for an improved process for the sulfhydrolysis of sulfides to mercaptans, in particular dimethylsulfide to methylmercaptan.

There is also a need for an improved process for upgrading sulphides, in particular dimethyl sulphide, by-products during the production of mercaptans made from alcohol (s) and hydrogen sulphide.

An objective of the present invention is to provide a catalyst for the sulfhydrolysis of sulfides to mercaptans which is easy to use, economical and which allows satisfactory conversion.

Another objective of the present invention is to provide a process for the sulfhydrolysis of sulfides into mercaptans which can be easily integrated into an industrial production unit of mercaptans, in particular produced from alcohol (s) and H ₂ S.

An objective of the present invention is to provide a process for the preparation of mercaptans in which the sulphides by-products (for example during the reaction between an alcohol and the H ₂ S) are recycled or upgraded economically, easy to put. implemented and industrially viable.

The present inventors have surprisingly discovered that the use of a specific catalyst, based on titanium dioxide (of formula Ti0 ₂ ) and or zirconia (also called zirconium dioxide, of formula Zr0 ₂ ) during the sulfhydrolysis makes it possible to obtain a good conversion of the sulphides, in particular a conversion of at least 36%, preferably of at least 50%, or even of at least 70%. In addition, methane as a by-product of sulfhydrolysis is produced with very low selectivity, for example less than 2%.

The catalysts according to the invention are known as inert catalyst supports (that is to say without catalytic activity). They are therefore of simple, economical and not very harmful compositions, which makes it possible to obtain a sulfhydrolysis process that is more efficient and more respectful of the environment. In particular, the sulfhydrolysis process as according to the invention can be integrated into an industrial production plant for mercaptans, produced in particular from at least one alcohol and H ₂ S. The sulfhydrolysis process according to the invention then makes it possible to increase the productivity of mercaptans in a simple and economical manner by upgrading the sulphides by-products during the main reaction and by also transforming them into mercaptans.

In addition, surprisingly, the present inventors have also discovered that the mercaptans resulting from the sulfhydrolysis and the _{unreacted H 2} S could be reintroduced directly (in particular without a separation and / or purification step), into the product. main reactor and this without consequence for the main reaction between the alcohol (s) and H ₂ S. The mercaptans produced by the two reactions (main and sulfhydrolysis) can then be separated and / or purified and / or recovered at a single location, for example at the outlet of the main reactor.

This integration of the sulfhydrolysis process into the main mercaptan production chain can be reinforced by the presence of a single supply of H ₂ S for the two main reactions and of sulfhydrolysis (for example at the inlet of the sulfhydrolysis reactor). Thus, according to the invention, it is possible to obtain a simple and effective process for upgrading sulphides which is fully integrated into an industrial production line for mercaptans. This device is particularly simple to implement: it can be easily connected to the main unit and requires only few modifications to the latter.

Thus, the present invention relates to a sulfhydrolysis process, in which a sulfide, preferably a dialkylsulfide, is reacted with hydrogen sulfide (H ₂ S) in the presence of Zr0 ₂ and / or Ti0 ₂ as a catalyst. (s), to obtain at least one mercaptan, preferably a mercaptan.

The present invention also relates to a process for preparing mercaptan (s) comprising the steps of:

- preparation of mercaptan (s) and dialkylsulphide (s) from at least one alcohol and H ₂ S, and

- reaction of (s) said (s) dialkylsulfide (s) product (s) with H ₂ S according to the sulfhydrolysis process as according to the invention, to obtain (s) said (s) mercaptan (s) ).

Definitions

The term “catalyst” is understood to mean in particular a substance or a composition of chemical substances accelerating a chemical reaction and which is (are) unchanged at the end of this reaction.

According to the present invention, the catalyst used during the sulfhydrolysis reaction comprises titanium dioxide (Ti0 ₂ ) and / or zirconia (Zr0 ₂ ), preferably titanium dioxide. Such catalysts can also be called catalysts based on titanium dioxide and / or zirconia.

Titanium dioxide and / or zirconia are used as catalyst (s) in the sulfhydrolysis reaction. It is understood that Ti0 ₂ and / or Zr0 ₂ are the active components of the catalyst (ie compounds having catalytic activity). In particular, the catalysts according to the invention do not include other compounds having catalytic activity on the sulfhydrolysis reaction.

Preferably, the catalysts according to the invention consist essentially of, or even consist of titanium dioxide and / or zirconia, and optionally stabilizers and / or binders. The stabilizers and the binders are those conventionally used in the field of catalysts.

By "promoter" (also called "dopant") is meant a chemical substance or a composition of chemical substances which can modify, in particular improve, the catalytic activity of a catalyst. For example, by "promoter" is meant a chemical substance or a composition of chemical substances which makes it possible to improve the conversion and / or the selectivity of the catalyzed reaction relative to the catalyst alone. Preferably, the catalysts according to the invention do not include a promoter.

The usual definitions of conversion, selectivity and yield are as follows: Conversion = (number of moles of reagent in the initial state - number of moles of reagent remaining after the reaction) / (Number of moles of reagent in the initial state) / (Number of moles of reagent in the initial state) 'initial state)

Selectivity = Number of moles of reagent converted to desired product / (Number of moles of reagent in the initial state - number of moles of reagent remaining after the reaction)

Yield = Conversion X Selectivity

In particular, the sulfhydrolysis catalysts according to the invention make it possible to obtain a conversion of the sulfides of between 30% and 90%, preferably between 50% and 80%, even more preferably between 50% and 75%.

The selectivity of the sulfhydrolysis reaction for mercaptans is in particular greater than or equal to 98%.

Sulphides and mercaptans

The term “sulfide” is understood to mean any organic compound comprising a -C-S-C- function.

Preferably, the term “sulfide” is understood to mean a dialkylsulfide.

The term “dialkylsulfide” is understood to mean in particular a compound of the following general formula (I):

RS-R '(I) in which, R and R', identical or different, are, independently of one another, a hydrocarbon radical, saturated, linear, branched or cyclic, optionally substituted. Preferably, R and R ', which are identical or different, are, independently of one another, an alkyl radical, linear or branched; more preferably a linear or branched, preferably linear, alkyl radical containing between 1 and 18 carbon atom (s), preferably between 1 and 12 carbon atom (s).

R and R ', identical or different, can be chosen independently of one another from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl , octyl, nonyl, decyl, undecyl and dodecyl, as well as their isomers. Preferably, R and R ’, the same or different, can be independently selected from the group consisting of methyl, ethyl, octyl, and dodecyl.

Preferably, R and R ’are the same (which corresponds to a symmetrical dialkylsulfide).

The symmetrical dialkylsulphides are in particular of the following general formula (II):

R-S-R (II) in which R is defined as above.

In particular, the dialkylsulfides according to the invention are chosen from the group consisting of dimethylsulfide, diethylsulfide, dioctylsulfide, didodecylsulfide and methylethylsulfide. The dialkylsulfides according to the invention can be chosen from the group consisting of dimethylsulfide, diethylsulfide, dioctylsulfide and didodecylsulfide. Very particularly preferably, the dialkylsulphide is dimethylsulphide.

The mercaptans according to the invention are those corresponding to the sulfhydrolysis of sulfides as defined above. Preferably, the term “mercaptans” is understood to mean alkylmercaptans.

In particular, the term “alkylmercaptan” is understood to mean a compound of the following general formulas (III) and / or (IV):

R-SH (III) and or R’SH (IV), where R and R ’are as defined above.

Particularly preferably, the mercaptan obtained according to the invention is methylmercaptan.

Process for sulfhydrolysis of sulfides to mercaptans

The present invention therefore relates to a process for preparing at least one mercaptan by sulfhydrolysis. In particular, the present invention relates to a process for preparing at least one mercaptan, in which a dialkylsulphide is reacted with hydrogen sulphide (H ₂ S) in the presence of Zr0 ₂ and / or Ti0 ₂ as catalyst (s).

Preferably, said catalyst does not include an alkali metal oxide, in particular such as the oxides of lithium, sodium, potassium, rubidium and cesium.

Preferably, said catalyst does not include a promoter. In particular, said catalyst does not include alumina (Al ₂ 0 ₃ ).

In particular, said catalyst does not include phosphorus.

Preferably, said catalyst is Ti0 ₂ . Particularly preferably, the catalyst comprises only TiO ₂ as active component, and in particular in its crystalline anatase form.

When the catalyst comprises Ti0 ₂ and Zr0 ₂ , then it can comprise between 30% and 50%, preferably between 35% and 45%, for example approximately 40% by weight of Ti0 ₂ relative to the total weight of the catalyst and / or between 50% and 70%, preferably between 55% and 65%, for example approximately 60% by weight of Zr0 ₂ relative to the total weight of the catalyst.

The catalysts according to the invention can have a specific area greater than 40 m ² .g ^_ ¹ . Preferably, the specific area is at least 50 m ² .g ^_1 for a catalyst based on Zr0 2. Preferably, the specific area is at least 80 m ² .g ^_1 for a catalyst _{based on Zr0 2.} Ti0 ₂ .

The shape of the catalysts can be of any type, for example of spherical, cylindrical, ring, star, aggregate or any other three-dimensional shape, or else in the form of a powder which can be pressed, extruded or granulated.

The sulfhydrolysis reagents can be in the gaseous, liquid or solid state, preferably gaseous or liquid.

The sulfhydrolysis reaction temperature can be between 100 ° C and 500 ° C, preferably between 200 ° C and 400 ° C, preferably between 200 ° C and 380 ° C, more preferably between 250 ° C and 380 ° C. ° C.

The sulfhydrolysis reaction can be carried out under a pressure of between 50 mbar and 100 bar, preferably between atmospheric pressure (approximately 1 bar) and 50 bar, and advantageously between 5 and 20 bar.

The H ₂ S / sulphide molar ratio can be between 0.1 / 1 and 50/1, preferably between 2/1 and 20/1. Preferably, said ratio is between 2/1 and 15/1, more preferably between 2/1 and 10/1, for example 4/1.

Advantageously, the reactants (sulphide and H ₂ S) can respect a particular contact time with the catalyst within the reactor where the sulphhydrolysis takes place. This parameter is expressed with the equation of the hourly volume speed:

(WH) = (total flow of sulphide + H ₂ S entering) / (Volume of catalyst in the reactor).

The WH can be between 100 and 1200 h ^-1 .

The sulfhydrolysis reaction can take place in any type of reactor, for example fixed bed tubular, multitubular, microchannel, catalytic wall or fluidized bed reactors, preferably a fixed bed tubular reactor.

In particular, the sulfhydrolysis process according to the invention is carried out in a reactor comprising a single catalytic zone (said zone is in particular continuous). The amount of each reagent supplied to the reactor can vary depending on the reaction conditions (eg temperature, hourly volume rate, etc.) and is determined according to conventional knowledge. Hydrogen sulfide may be present in excess.

Mercaptan production process

The present invention relates to a process for the preparation of mercaptan (s) and dialkylsulfide (s) from at least one alcohol and H ₂ S, in which the said dialkylsulfide (s) produced ( s) then reacts (reacts) with H ₂ S according to the sulfhydrolysis process as defined above, to obtain the said mercaptan (s).

Thus, the present invention relates to a process for preparing mercaptan (s) comprising the steps of:

- reaction of said dialkylsulfide (s) product (s) with H ₂ S according to the sulfhydrolysis process as defined above, to obtain said mercaptan (s) ).

The reaction between an alcohol and H ₂ S to form a mercaptan (and a sulfide as a by-product) is a known reaction, described for example in US Patents 2820062A, US 7645906B2 and US 2820831 A. For example, the reaction can be carried out at a temperature between 200 ° C and 450 ° C and / or at a pressure ranging from a reduced pressure to 100 bar. Usually, a catalyst is present such as alumina promoted by alkali metals and or alkaline earth metals. The H ₂ S can be present in excess.

Among the reagents, at least one alcohol, preferably one or two alcohols, can (can) be used. Preferably, a single alcohol is used. The alcohol (s) can be chosen from alcohols (Ci-Ci ₈ ), or even (CrCi ₂ ), and mixtures thereof. In particular, the alcohols can be chosen from the group consisting of methanol, ethanol, octanol, dodecanol and their mixtures. Preferably, the alcohol used is methanol.

Below, it is understood that when two streams are introduced into a reactor, they can each be introduced separately into the reactor or be combined before they enter the reactor.

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

A) in a first reactor, a stream comprising H ₂ S and a stream comprising at least one alcohol is introduced;

B) the two streams are reacted to obtain an outgoing stream comprising at least one mercaptan, at least one dialkylsulfide and optionally H ₂ S;

C) we separate from the outgoing flow from step B):

- a flow comprising the mercaptan (s), - a flow comprising the dialkylsulphide (s), and

- optionally a flow comprising H ₂ S;

D) in a second reactor, said stream comprising the dialkylsulphide (s) is introduced with a stream of H ₂ S;

E) the two streams are reacted according to the sulfhydrolysis process as defined above to obtain an outgoing stream comprising the said mercaptan (s) and optionally H ₂ S;

F) optionally, the flow of H ₂ S resulting from stage C) is recycled to stage A).

The mercaptan (s) can be recovered at the end of step C) and / or after separation of the flow leaving step E), preferably at the end of step C).

The outgoing stream from step B) can comprise at least one mercaptan, at least one dialkylsulfide, optionally water, unconverted alcohol (s) and H ₂ S The outgoing stream from step E) can comprise the said mercaptan (s), H ₂ S and optionally methane and the unconverted dialkylsulphide (s). .

The flow leaving the second reactor of step E) can be recycled, preferably entirely, into the first reactor of step A). Thus, the outgoing stream from the sulfhydrolysis process comprising the mercaptan (s) and optionally H ₂ S can be introduced directly into the main reactor (or first reactor), in particular without a separation step and or prior purification. . In particular, the flow leaving the second reactor of stage E) can correspond entirely or partially, preferably entirely, to the flow comprising H ₂ S from stage A), optionally with the _{recycled H 2} S resulting from of step C). In this case, the outgoing flow from step E) comprises H ₂ S.

Surprisingly, the introduction of mercaptans into the main reactor has no influence on the main reaction between at least one alcohol and the H ₂ S. In addition, the H ₂ S which can be obtained from the step E) is thus completely recycled to step A). Such recycling has in particular the advantage of having only one H ₂ S inlet for the entire mercaptan production process, at the inlet of the sulfhydrolysis reactor for example.

Thus, the sulfhydrolysis process according to the invention integrated into an industrial installation for the production of mercaptans makes it possible to completely reprocess the sulfides 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 sulfhydrolysis reaction, which increases the productivity.

The separation step C) can be carried out by distillation, for example under reduced pressure, according to conventional methods. For example, the distillation can be carried out at a pressure of between 0.1 bar and 10 bar, in particular between 1 and 10 bar. Step C) can in particular make it possible to separate from the outgoing flow resulting from step B):

- a flow comprising the mercaptan (s), - a stream comprising the dialkylsulphide (s), optionally a stream comprising H ₂ S, optionally a stream comprising methane,

- possibly water, possibly unconverted alcohol.

According to a particular embodiment, said preparation process comprises the following steps: a) in a first reactor, a stream comprising a mercaptan and H ₂ S is introduced and a stream comprising at least one alcohol, preferably an alcohol ; b) the two streams are reacted to obtain an outgoing stream comprising the mercaptan, a dialkylsulfide and optionally H ₂ S; c) separating from the outgoing flow resulting from step b):

- a flow comprising mercaptan;

- a flow comprising the dialkylsulphide; and

- optionally a flow comprising H ₂ S; d) in a second reactor, the stream comprising the dialkylsulfide is introduced with a stream of H ₂ S; e) the two streams are reacted according to the sulfhydrolysis process as defined above to obtain an outgoing stream comprising the mercaptan and H ₂ S; f) the outgoing stream from step e) is introduced, preferably directly, into the reactor from step a); g) optionally, the stream comprising the mercaptan obtained from step c) is recovered; and h) optionally, the flow of H ₂ S resulting from step c) is recycled to step a).

The flow leaving step f) can correspond entirely or partially, preferably entirely, to the entering flow of mercaptan and H ₂ S from stage a).

According to another particular embodiment, said preparation process comprises the following steps: a ′) in a first reactor, a stream comprising H ₂ S and a stream comprising at least one alcohol, preferably an alcohol, is introduced; b ') the two streams are reacted to obtain an outgoing stream comprising a mercaptan, a dialkylsulfide and optionally H ₂ S; c ') we separate from the outgoing flow from step b'):

- a flow comprising mercaptan;

- a flow comprising the dialkylsulphide; and optionally a stream comprising H ₂ S; d ′) optionally, the stream comprising the mercaptan obtained from step c ′) is recovered; e ′) optionally, the stream of H ₂ S resulting from step c ′) is recycled to step a ′); f) in a second reactor, the stream comprising the dialkylsulfide is introduced with a stream of H ₂ S; g ′) the two streams are reacted according to the sulfhydrolysis process as defined above to obtain an outgoing stream comprising the mercaptan and H ₂ S; h ') we separate from the outgoing flow from step g'):

- a flow comprising mercaptan; a stream comprising H ₂ S; i ′) the flow comprising the mercaptan resulting from step h ′) is combined with that exiting from step b ′ before and / or during step c ′); j ′) optionally, the flow of H ₂ S resulting from step h ′) is recycled to step f).

This embodiment offers in particular an independence of the supply of H ₂ S to the main reactor with respect to the sulfhydrolysis reactor.

The present invention also relates to the use of Zr0 ₂ and / or Ti0 ₂ as catalyst (s), in the reaction by reacting a sulphide with hydrogen sulphide to obtain a mercaptan. In particular, said catalyst and said reaction are as defined for the sulfhydrolysis process as described above. Sulfides and mercaptans are also as defined above.

Description of figures

Figure 1 schematically shows a methylmercaptan production unit integrating the sulfhydrolysis process as according to the invention. The production unit may be pre-existing and may correspond to the items circled in dotted lines.

The secondary reactor (1) (where the sulfhydrolysis takes place) comprises an H ₂ S inlet and a dimethyl sulfide (DMS) inlet. At the outlet, stream A comprises H ₂ S and methyl mercaptan.

Stream A enters directly into the main reactor (2) also comprising a methanol inlet. The stream B leaving the reactor (2) comprises methylmercaptan, dimethylsulfide and H ₂ S.

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

- a flow comprising methylmercaptan (MeSH);

- a stream comprising dimethylsulfide (DMS); and

- a stream comprising H ₂ S, then recycled to the reactor (2) (not shown diagrammatically). The DMS stream is then recycled to the reactor (1). FIG. 2 schematically represents another implementation of a methylmercaptan production unit integrating the sulfhydrolysis process as according to the invention. The production unit can be pre-existing and can correspond to the elements surrounded by dotted lines. The secondary reactor (1A) (where the sulfhydrolysis takes place) comprises an H ₂ S inlet and a dimethyl sulfide (DMS) inlet. At the outlet, stream A comprises H ₂ S and methyl mercaptan.

Stream A undergoes a separation step by distillation in (1 B), which gives rise to a stream of H ₂ S recycled into the reactor (1A) and a stream B which comprises methyl mercaptan which is combined in (3) with the flow C leaving the reactor (2), where the main reaction between methanol and H ₂ S takes place.

A separation step by distillation (3) gives two different streams:

- a flow comprising methylmercaptan (MeSH);

- a stream comprising dimethylsulfide (DMS);

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

FIG. 3 represents the selectivity in percentage in terms of sulphides for three different reaction temperatures as a function of the percentage by weight of mercaptans in the feed entering the main mercaptan synthesis reactor.

EXAMPLES

Example 1: Process for the sulfhydrolysis of dimethylsulfide (DMS) to methylmercaptan (MeSH)

Before testing, the catalysts were activated in situ with a procedure comprising a first step of drying with nitrogen at 250 ° C, followed by sulphurization with H ₂ S at 350 ° C for 1 hour.

The performance of the catalysts was evaluated for the reaction of producing MeSH from DMS in a fixed bed reactor comprising a single catalytic zone with a volume of catalyst of 30 mL, a temperature ranging from 300 ° C to 350 ° C, under a pressure of 9 bar absolute, with a feed gas composition DMS / H ₂ S = 1/4 (v / v) and an hourly volume speed of 800 h ^-1 . The reagents are preheated to a temperature> 100 ° C and are flashed during their introduction from the bottom of the reactor.

The products were analyzed online by gas chromatography.

The results of conversion of DMS and of selectivity for MeSH and CH ₄ obtained for 3 different catalysts are described in Table 1 opposite:

It is noted that the catalysts according to the invention make it possible to significantly increase the conversion of dimethylsulfide, while retaining very good selectivity. In particular, with the catalysts according to the invention, the conversion can be greater than 70%, compared to a maximum of 35% for alumina, a conventional catalyst used in sulfhydrolysis. It is also observed that only a negligible amount of methane is formed. Example 2: Production of mercaptans

The influence of the sulfhydrolysis reaction on the main mercaptan synthesis reaction was evaluated.

To do this, the content of sulphides coproduced by the main reaction of synthesis of mercaptans was monitored as a function of the variation of the content of mercaptans entering within reactor 1 (where the mercaptans are produced from alcohol and H ₂ S).

The conditions of the main reaction are as follows:

Pressure = 3.5 bar

H ₂ S / Ethanol ratio (molar) = 2.4

GHSV = 580 h ¹

The sulphide selectivity results obtained for three incoming mercaptan contents at three different temperatures with an alumina-based catalyst are described in Figure 3.

As shown in FIG. 3, the selectivity for sulphides coproduced during the main synthesis reaction of mercaptan (Reactor 1) remains independent of the content of incoming mercaptans, resulting from the sulphhydrolysis reaction. The non influence of the presence of mercaptans on the main synthesis reaction is therefore demonstrated.

Claims

1. Sulfhydrolysis process, in which a dialkylsulfide is reacted with hydrogen sulfide (H ₂ S) in the presence of Zr0 ₂ and / or Ti0 ₂ as catalyst (s), to obtain at least one mercaptan.

2. The method of claim 1, wherein said (s) (s) catalyst (s) does (include) no alkali metal oxide.

3. Process according to claim 1 or 2, said process being carried out in a reactor comprising a single catalytic zone.

4. Method according to any one of claims 1 to 3, wherein the reaction temperature is between 100 ° C and 500 ° C, preferably between 200 ° C and 400 ° C, more preferably between 200 ° C and 380 ° C, more preferably between 250 ° C and 380 ° C.

5. Method according to any one of the preceding claims, in which the H ₂ S / dialkylsulfide molar ratio is between 0.1 / 1 and 50/1, preferably between 2/1 and 20/1.

6. A method according to any preceding claim, wherein the dialkylsulfide is selected from the group consisting of: dimethylsulfide, diethylsulfide, dioctylsulfide, didodecylsulfide and methylethylsulfide, preferably dimethylsulfide.

7. Process for preparing mercaptan (s) comprising the steps of:

- reaction of (s) said (s) dialkylsulfide (s) product (s) with H ₂ S according to the sulfhydrolysis process as defined in any one of claims 1 to 6, to obtain the (s) said mercaptan (s).

8. The method of claim 7, comprising the following steps:

B) the two streams are reacted to obtain an outgoing stream comprising at least one mercaptan and at least one dialkylsulfide and optionally H ₂ S; C) we separate from the outgoing flow from step B):

- a flow comprising the mercaptan (s),

- a flow comprising the dialkylsulphide (s), and

- optionally a flow comprising H ₂ S;

D) in a second reactor, the stream comprising the dialkylsulfide (s) is introduced with a stream of H ₂ S;

E) the two streams are reacted according to the sulfhydrolysis process as defined in any one of claims 1 to 6 to obtain an outgoing stream comprising the said mercaptan (s) and optionally H ₂ S;

F) optionally, the flow of H ₂ S from step C) is recycled to step A)

9. The method of claim 8, wherein the flow leaving the second reactor of step E) is recycled to the first reactor of step A).

10. The method of claim 7, comprising the following steps: a) in a first reactor, introducing a stream comprising a mercaptan and H ₂ S and a stream comprising an alcohol; b) the two streams are reacted to obtain an outgoing stream comprising the mercaptan, a dialkylsulfide and optionally H ₂ S; c) separating from the outgoing flow resulting from step b):

- a flow comprising mercaptan,

- a flow comprising the dialkylsulphide; and

- optionally a flow comprising H ₂ S; d) in a second reactor, the stream comprising the dialkylsulfide is introduced with a stream; H ₂ S; e) the two streams are reacted according to the sulfhydrolysis process as defined in any one of claims 1 to 6 to obtain an outgoing stream comprising the mercaptan and H ₂ S; f) the outgoing stream from step e) is introduced, preferably directly, into the reactor from step a); g) optionally, the stream comprising the mercaptan obtained from step c) is recovered; and h) optionally, the flow of H ₂ S resulting from step c) is recycled to step a).

11. Use of Zr0 ₂ and / or Ti0 ₂ as catalyst (s) in the reaction by reacting a dialkylsulfide with hydrogen sulfide to obtain a mercaptan.