Method for continuous production of methyl mercaptan

Abstract

The invention relates to a method for the continuous production of methyl mercaptan by reacting methanol with hydrogen sulphide in the presence of a catalyst. The method is characterized in that at least one partition is installed in a reactor to create at least two successive catalytic zones, wherein the partition hermetically connects an upper and / or a lower cover of the reactor to an upper and / or a lower tube plate, or plate, or coil, respectively. Use of the proposed method makes it possible to increase selectivity and the yield of methyl mercaptan, while also reducing capital costs and operating costs.

Description

[0001] METHOD FOR CONTINUOUS PRODUCTION OF METHYL MERCAPT ANA

[0002] Field of technology

[0003] The invention relates to the field of petrochemistry, namely to the production of alkyl mercaptans, in particular methyl mercaptan.

[0004] The invention relates to a method for producing methyl mercaptan by reacting a mixture of reagents containing, among other things, recycled methyl mercaptan synthesis products - dimethyl sulfide, and optionally dimethyl disulfide and / or dimethyl ether, with recycled and / or re-fed hydrogen sulfide on heterogeneous catalysts, followed by adding a mixture of recycled and / or re-fed methanol and hydrogen sulfide to the reaction gas.

[0005] Prior art

[0006] Methyl mercaptan is a semi-finished product in the synthesis of methionine and a number of other products, obtained industrially mainly by the “methanol method” from methanol and hydrogen sulfide on catalytic systems based on aluminum oxide, also containing transition metal oxides and, optionally, basic promoters.

[0007] A method is known for the continuous production of methyl mercaptan by converting an initial gas mixture containing methanol and hydrogen sulfide in the gas phase with a molar ratio of 1:1 to 10:1 at a reaction temperature of 200 to 600°C and an operating pressure of 1.5 to 40 bar in the presence of a catalyst in a multilayer shelf reactor, characterized in that the catalyst is distributed in portions across two or more zones separated from each other, into the first of which only the initial gas containing methanol and hydrogen sulfide is fed, and between the remaining zones methanol is additionally fed in liquid and / or gaseous form and the resulting methyl mercaptan is separated outside the reactor (patent RU 2374226).

[0008] Various implementations of this method include additional feeding of hydrogen sulfide and / or methanol between the shelves, placement of different catalysts or catalysts of varying activity and / or different catalyst volumes on the shelves, and alteration of the direction of gas flow through the catalyst bed(s). The active component of the catalysts may include alkali metal tungstates and / or their halides supported on aluminum oxide.

[0009] The main drawback of this method is that the process operates adiabatically, leading to heating of the gas mixture and catalyst along the bed height. This creates a significant temperature gradient in each catalytic zone, particularly significant in the initial (first along the gas flow) catalytic zones of the reactor. This ultimately reduces selectivity for the target product. Due to the suboptimal temperature regime in the region with elevated methanol concentrations, it necessitates limiting the amount of methanol fed to the increased catalyst bed. These drawbacks are characteristic of all methyl mercaptan production methods implemented in adiabatic reactors.

[0010] A method for synthesizing methyl mercaptan from dialkyl sulfides and dialkyl polysulfides is also known, as described in (RU Patent 2490255). This method does not utilize methanol as feedstock. The process is organized using a multi-zone reactor, the zones of which can be implemented as fixed beds, tube bundles, or fluidized beds. The method is characterized by a significant excess of hydrogen sulfide during synthesis (the molar ratio of hydrogen sulfide to methyl groups ranges from 3:1 to 20:1) and the use of feedstock substances that are not high-volume products and, therefore, expensive to produce. Furthermore, given the significant dilution of the feedstock with excess hydrogen sulfide, the method has a reduced efficiency in utilizing the space in the reaction zone.The disadvantages of the specified option of using a multi-zone reactor, composed of tube bundles connected in series in a single housing along the height, also include the complexity of reloading the catalysts, high capital costs for the manufacture of the reactor and the coolant distribution and supply system, which requires either separate pump supply of high-temperature coolant to each tube bundle, or the implementation of an individual thermosiphon cooling circuit for each tube bundle to avoid differences in boiling temperatures across the zones, determined by the hydrostatic column of the liquid coolant.

[0011] The closest in essence to the present invention is a method for producing methyl mercaptan from methanol and hydrogen sulfide (patent RU 2172311), which is carried out by continuous interaction of the initial gas mixture of methanol and hydrogen sulfide at a temperature of 300 to 500°C and an operating pressure of 5 to 15 bar on a catalyst layer based on aluminum oxide with applied potassium tungstate or other promoters, followed by absorption and distillation separation of methyl mercaptan from the mixture of gaseous reaction products and return of unused methanol and hydrogen sulfide to the process, as well as removal of inert gases and waste water and replenishment of spent methanol and hydrogen sulfide.In this case, the initial mixture of methanol and hydrogen sulfide is formed by compressing fresh gaseous hydrogen sulfide to an intermediate pressure with the addition of liquid methanol, mixing circulating gaseous hydrogen sulfide with the fresh gas and compressing the resulting mixture to a working pressure, introducing an additional amount of methanol in the form of vapor into the compressed gas mixture with the formation of an initial gas mixture with a molar ratio between hydrogen sulfide and methanol from 1.1 to 3, heating the initial gas mixture to a preliminary temperature in the range from 150 to 200 °C, after which the mixture is fed in a single stream into a reactor, the tubes of which are divided into zones, the first of which is filled with a layer of inert bulk material, where further heating of the initial gas mixture to the reaction temperature occurs by heat exchange with the heat of reaction released on the catalyst layer, and the second, filled with a catalyst, where contact of the heated gas mixture with the catalyst occurs.Disadvantages of the described method include reduced selectivity for the formation of the target product, due to the high methanol concentration at the reactor inlet and in the primary contacting catalytic beds. This shifts the equilibrium in the reactions of the byproducts dimethyl sulfide (DMS) and dimethyl ether (DME) toward their formation. Furthermore, dosing the recycled byproduct dimethyl sulfide simultaneously with methanol inhibits its decomposition and, in the absence of DMS removal, leads to its accumulation in the system. Another disadvantage of the method is the high energy consumption for hydrogen sulfide recovery, due to the need to maintain a significant excess (preferably 1.5 to 2%) to ensure increased selectivity for the target reaction of methyl mercaptan formation.Other methods for synthesizing methyl mercaptan from methanol and hydrogen sulfide, carried out in tubular reactors (patents RU 2443686, RU 2389541), also have similar disadvantages.

[0012] Disclosure of invention

[0013] The objective of the present invention is to increase the selectivity and yield of methyl mercaptan both in the main reaction of methanol with hydrogen sulfide and in the processing of by-products of the main reaction, ensuring maximum flexibility in process control and simultaneously reducing capital and operating costs for implementing the method.

[0014] The problem is solved using a method for the continuous production of methyl mercaptan by reacting methanol with hydrogen sulfide at elevated temperature and pressure over solid catalysts, followed by separation of the reaction products into the target product, recycled products, unreacted feedstock components, and waste streams. The combined flow of recycled reactants is mixed with newly fed feedstock components, and / or the individual recycled reactants are separately fed to the reactor. To create at least two sequentially arranged catalytic zones, the reactor is equipped with at least one baffle, hermetically sealing the upper and / or lower reactor covers with the upper and / or lower tube sheets, or a plate or coil, respectively.

[0015] Preferably, the interaction of methanol with hydrogen sulfide is carried out at a temperature of 280°C to 450°C, a pressure of 5-20 bar, and a molar ratio of hydrogen sulfide to methanol of 1.01 to 20.

[0016] Preferably, the method includes at least one partition connecting the upper and lower tube sheets in the reactor volume through which the coolant passes.

[0017] Preferably, individual feedstock components and / or recycled reactants are introduced into the reactor into various catalytic zones as they are depleted by the movement of the gas flow through the catalyst.

[0018] Preferably, shell-and-tube, plate or spiral designs are used.

[0019] Preferably, the tubes, plates and coils of the different catalytic zones have different transverse dimensions.

[0020] Preferably, the different catalytic zones have different numbers of tubes, plates or coils.

[0021] Preferably, the various catalytic zones are loaded with catalysts that differ in properties from the catalysts loaded in other catalytic zones.

[0022] Preferably, individual catalytic zones are loaded in height with catalysts of varying activity or mixtures of catalyst with inert material in varying proportions.

[0023] Preferably, the entire flow of return dimethyl sulfide obtained during the separation of reaction gases and at least part of the flow of return hydrogen sulfide obtained during the separation of reaction gases or its mixture with the initial hydrogen sulfide are fed into the first or several first catalytic zones along the gas flow, filled with a dimethyl sulfide decomposition catalyst.

[0024] Preferably, the decomposition of dimethyl sulfide in the presence of hydrogen sulfide is carried out in a separate reactor, the outlet stream of which is used as the input stream of the methyl mercaptan synthesis reactor.

[0025] Preferably, one or more catalytic zones, to ensure different temperatures in them, have coolant circulation loops, divided into separate chambers in the intertube space of a shell-and-tube reactor by means of partitions or by means of collectors in a plate or spiral reactor, while the heating of the decomposition zones of the returned products is achieved by the flow of a portion of the hot coolant between the chambers of the expansion tank. PC17RU2025 / 000277

[0026] The technical problem is solved by feeding the interacting components into a reactor filled with a heterogeneous catalyst or catalysts with equal or different activity, or different catalysts, in which the space formed by the heat exchange elements combined into a single bundle of tubes, plates or spirals and allocated for the catalyst is divided into several zones by means of partitions parallel to the tubes, plates or spirals. Thus, several catalytic zones are combined into a single tube bundle consisting of tubes filled with catalyst (Fig. 1, 2) or a bundle of plates (Fig. 3, 4), or spirals (Fig. 5). The numbers indicate: 1 - feedstock inlet nozzle; 2 - first catalytic zone; 3 - partition between the first and second catalytic zones; 4 - second catalytic zone; 5 - inter-section chamber between the second and third catalytic zones; 6 - body; 7 - upper and lower covers; 8 - tube sheets;9 - partition between the second and third catalytic zones; 10 - nozzle for introducing additional raw materials into the inter-section chamber between the first and second catalytic zones; 11 - inter-section chamber between the second and third catalytic zones; 12 - third catalytic zone; 13 - nozzle for introducing additional raw materials into the inter-section chamber between the second and third catalytic zones; 14 - nozzle for removing reaction products; 15 - coolant distributor by section / sections; 16 - device for common removal of coolant vapor-liquid mixture; 17 - partition of the intertube space; 18 - nozzle for introducing coolant into a dedicated coolant circulation chamber; 18a - coolant distributor in a dedicated coolant circulation section; 19 - device for removing the coolant vapor-liquid mixture from a dedicated coolant circulation section; 20 - heat exchange plate elements; 21 - common collector of the coolant circulation system;22 - collector of separate coolant circulation system; 23 - coolant circulation system; 24 - supporting structure.

[0027] To maintain the optimal reaction temperature, the second space—the intertube space of a shell-and-tube heat exchanger, or the space inside the plates or coils—is filled with a liquid coolant, which can be diphenyl-diphenyl oxide mixtures or eutectic molten salts. The first zone downstream of the gas flow, which optionally has a lower temperature than the other zones, is fed with the unreacted portion of the hydrogen sulfide, or a mixture of hydrogen sulfide and fresh hydrogen sulfide, along with vapors of dimethyl sulfide separated from the reaction products, and optionally other sulfides, dimethyl ether, and / or methanol.In the inter-section chambers, the gas can be mixed with some or all of the designated amount of liquid or vaporous methanol, maintaining an increased molar ratio of the reacting feedstock components (hydrogen sulfide to methanol or methyl groups of the supplied reactants) in the range of 1.01-20. This increased ratio is maintained in all subsequent catalytic zones of a single bundle of heat-exchange tubes, plates, or coils by feeding the appropriate recycled or feedstock reactants in the gas and, possibly, liquid phase. Feedstock or recycled components are fed as they are depleted in the preceding catalytic zones into the corresponding inter-section chamber of the tube space of the catalytic zone, where the contact gas enters.

[0028] In one embodiment of the invention, the first or several catalytic zones upstream of the supplied gas flow may be located in a space separated from the shell-and-tube heat exchanger by baffles, or in plate and spiral heat exchanger designs by separate coolant distributors and devices for the common discharge of the steam-gas mixture. Different catalyst bed temperatures can be maintained in the separated catalytic zones, and the coolant circulation system may also be divided into two or more communicating sections, each with a different coolant temperature. According to this embodiment of the invention, circulation in the various sections, in addition to the thermosiphon principle, may also be accomplished using blowers.In a preferred embodiment of the invention, heating of the coolant in the catalytic zone or zones where the endothermic reaction of dimethyl sulfide with hydrogen sulfide occurs is carried out by feeding a portion of the return coolant of the low-temperature section into the hot coolant circulation chamber of the expansion tank.

[0029] In various embodiments of the invention, the catalyst loaded in the first zone may be a γ-alumina-based catalyst, such as the known catalyst described in patent SU 1268571, or other catalysts, with or without promoters selected from alkali or transition metal oxides or alkali metal salts of transition metal acids. The catalysts may also be promoted with halides of alkali metal salts of transition metal acids and used in both sulfided and oxide forms. In addition to the catalysts listed above, the method allows for the use of catalysts obtained by impregnating supports based on silicon dioxide, aluminosilicates, and other materials.

[0030] The catalysts used in both the first and subsequent catalytic zones can, if necessary, be loaded in layers of varying activity, which can be controlled, among other things, by diluting the catalysts with any materials that are inert to the reaction gas, such as granules of α-aluminum oxide.

[0031] The subsequent zones are loaded with known catalysts based on γ-aluminum oxide containing tungstates or molybdates of alkali metals in oxide, sulfided or halogenated forms, for example, the catalyst according to the author's certificate SU 1316127, or patent SU 1608923.

[0032] The present invention is illustrated by embodiments shown in Figs. 1-5, which have identical designations for the elements of the devices used to implement the method. From here on, the method is discussed using the example of a three-zone shell-and-tube reactor, and the examples and detailed descriptions of these specific embodiments of the invention cannot be considered as any limitation on the essence or scope of the invention, or the appended claims.

[0033] According to the invention, when implementing the method in a three-zone reactor (Fig. 1), the initial reaction mixture, consisting of hydrogen sulfide and possibly a mixture thereof with recycled unreacted portion of hydrogen sulfide, possibly also containing dimethyl ether, as well as a portion of the total volume of provided fresh methanol, possibly in a mixture with recycled unreacted methanol separated from the reaction products, as well as dimethyl sulfide possibly separated from the reaction products, and optionally other sulfides in vapor form, are fed through nozzle 1 into the first reaction zone 2 filled with a catalyst and / or a mixture thereof with an inert material. The first catalytic zone is separated from the remaining zones by a partition 3, hermetically connecting the upper and / or lower reactor covers, respectively, with the upper and lower tube sheet, or plate or spiral.The gas mixture, flowing along the tubes and contacting the catalyst, is enriched with reaction products, thereby depleting the feedstock containing methyl groups. The outlets of the tubes of the first catalytic zone are connected to the inlets of the tubes of the second reaction zone 4 and the inter-section chamber 5 formed by the body 6 and / or the apparatus cover 7, the tube sheet 8 and the partition 9. In the second catalytic zone, the gas flow reverses its direction, and a portion of the feedstock containing fresh methanol vapor, possibly mixed with recycled methanol, and possibly recycled dimethyl sulfide, and optionally other sulfides, can be additionally fed into the inter-section chamber 5 between the first and second reaction zones through the nozzle 10.Similarly, at the outlet of the tubes of the second catalytic zone, an inter-section chamber 11 is formed by the housing 6 and / or apparatus cover 7, tube sheet 8, and baffle 3. This chamber is designed to redirect the flow into the third catalytic zone 12, reversing the direction of the gas flow. Additional feedstock components exhausted in the previous reaction zones, including, if necessary, hydrogen sulfide and / or its mixture with recycled unreacted hydrogen sulfide, possibly also containing dimethyl ether, can be supplied to the inter-section chamber 11 through nozzle 13. Gaseous reaction products are removed from the apparatus through nozzle 14. The inter-tube space of the reactor is filled with a high-temperature coolant or other coolants having a low saturated vapor pressure at the reaction temperature.The said coolant is continuously supplied into the inter-tube space through nozzle 15, and the vapor-liquid mixture of the high-temperature coolant is removed from the chamber for condensation and cooling through nozzle 16. If it is necessary to ensure different temperatures in different catalytic zones, the separation of the inter-tube space is provided by a partition or partitions 17, connecting the upper and lower tube sheets in the reactor volume, through which the coolant passes (Fig. 2), while the supply of the coolant to the various chambers of the inter-tube space and the removal of the vapor-liquid flow from it is provided, in addition to nozzles 15 and 16, by additional nozzles for the dedicated chamber 18 and 19.Thus, the present method enables the distribution of key feedstock components along the entire length of the tubular reactor tubes by introducing them fractionally into the inter-sectional chambers. This ensures a significantly greater excess of hydrogen sulfide relative to methanol in individual catalytic zones compared to the overall excess of hydrogen sulfide relative to methanol calculated for the entire reactor, thereby achieving increased process selectivity. Furthermore, when using a reactor according to Fig. 2, the method allows for varying the temperature of different zones of the same reactor, providing, if necessary, increased selectivity for byproduct processing.

[0034] When organizing the process in a plate reactor (Fig. 3), in contrast to a shell-and-tube reactor (Figs. 1-2), the space of the reaction zones is formed between the plates 20, which are combined (Fig. 4) into a common 21 or separate 22 inlet and outlet manifolds with nozzles for feeding the coolant 15, 18 and removing the vapor-liquid flow 16 of the high-temperature coolant circulation circuit 23. Thus, in the plate (Fig. 3) and spiral (Fig. 5) reactors, the space occupied by the catalyst is formed not inside the heat exchange elements, but in the outer space of the reactor between adjacent heat exchange elements, which makes it possible to increase the useful volume of the reactor occupied by the catalyst. The operating principle of the plate and spiral reactors is similar to the above-described embodiment of the method in a shell-and-tube reactor.

[0035] The best embodiment of the invention

[0036] The advantages of the method are demonstrated by the following implementation examples, carried out using a shell-and-tube reactor (Fig. 1). Table 1 lists the conditions for implementing the proposed method and the technical results achieved.

[0037] Example 1 (based on the prototype).

[0038] A gas stream containing 1.69 mol / h of evaporated methanol and 3.042 mol / h of hydrogen sulfide is fed through nozzle 1 into the first catalytic zone of a three-zone reactor similar to Fig. 1. The first two zones 2 and 9 are filled with a catalyst prepared according to patent SU 1268571. The third zone of the reactor 12 is filled with an inert material. The space velocity of the feedstock (SVFS) was ~400 h' 1 , the temperature in the tubes was maintained at 370±2°C, the pressure in the reactor was 9 kgf / cm 2The reaction products discharged from nozzle 14 had the composition given in column example 1 of table 1. The yield of the target product methyl mercaptan (CH3SH) based on the converted methanol was 82.34%, while the yields of recycled products were: dimethyl sulfide (CH3)28 - 3.92% dimethyl ether (CH3)2O - 9.24%.

[0039] Example 2.

[0040] The reaction was carried out similarly to example 1 with the same space velocity of the feedstock. The methanol feed was distributed between the two zones in a 60 / 40 ratio. 1.014 mol / h of methanol was fed into the first zone through nozzle 1 together with hydrogen sulfide fed in an amount of 3.042 mol / h, and 0.676 mol / h of methanol was fed into the second zone in vapor form through nozzle 10 without additional supply of hydrogen sulfide. The reaction products at the outlet of nozzle 14 had the composition given in the column of example 2 of Table 1. The yield of the target product CH3SH calculated on the converted methanol was 84.64%, while the yields of recycled products calculated on the converted methanol were: dimethyl sulfide (CH3)2S - 3.38% dimethyl ether (CH3)2O - 7.41%. Thus, in comparison with example 1, the production of by-products decreased by 13.7% and 19.8% relative, respectively, with a decrease in the total amount of non-condensable gases by 2.9% relative and an increase in the yield of the target product by 2.8% relative.

[0041] Example 3. The experiment was carried out similarly to Example 1 with the same feed space velocity. The catalyst in the same volume as in the first two experiments was distributed evenly between three zones 2, 9, 12, filling the remaining space of each zone with inert material. The methanol feed was distributed between all zones in the ratio 42.36 / 32.58 / 25.16. 0.716 mol / h of evaporated methanol and 3.042 mol / h of hydrogen sulfide were fed into the first zone 2 through nozzle 1, 0.551 mol / h of evaporated methanol was fed into the second zone 9 through nozzle 10, and 0.423 mol / h of evaporated methanol was fed into the third zone 12 through nozzle 13. The reaction products, collected at the reactor outlet through nozzle 14, had the composition given in column example 3 of table 1. The yield of the target product based on the converted methanol was 83.34%, while the yields of recycled products based on the converted methanol were: dimethyl sulfide - 3.12% dimethyl ether - 6.8%.Thus, compared to example 1, the production of by-products decreased by 20.47% and 26.34% relative, respectively, with a decrease in the total amount of non-condensable gases by 4.89% relative and an increase in the yield of the target product by 1.21% relative.

[0042] Example 4 (comparison example).

[0043] The process was carried out similarly to Example 1 at a similar contact time and identical other parameters, with a portion of the fed methanol replaced by dimethyl sulfide. Thus, 0.08 mol / h of dimethyl sulfide mixed with 1.53 mol / h of evaporated methanol was fed into the first zone through nozzle 1. 3.042 mol / h of hydrogen sulfide were also fed through nozzle 1. Thus, the molar ratio of hydrogen sulfide to methyl groups fed with the feedstock was maintained at 1.8:1. The composition of the products collected through nozzle 14 is given in column Example 4 of Table 1. The yield of the target product based on the converted methanol was 73.5%, while the yields of recycled products were: dimethyl sulfide - 10.04%, dimethyl ether - 7.03%.

[0044] Example 5.

[0045] The procedure was carried out similarly to Example 3 with a contact time identical to Example 4 and identical other parameters, wherein dimethyl sulfide was fed in evaporated form in a mixture with 3.042 mol of hydrogen sulfide through nozzle 1 into the first catalytic zone 2 in an amount of 0.08 mol / h, and the supply of evaporated methanol was distributed between the second 9 and third 12 catalytic zones, wherein 0.707 mol / h of evaporated methanol was fed into the second zone through nozzle 10, and 0.822 mol / h of evaporated methanol was fed into the third through nozzle 13. Thus, the molar ratio of hydrogen sulfide to methyl groups supplied with the feedstock was maintained at a level of 1.8:1. The composition of the products removed io from nozzle 14 is given in column example 5 of Table 1. The yield of the target product based on the converted methanol was 73.05%, while the yields of recycled products were: dimethyl sulfide - 1.92%, dimethyl ether - 7.04%.In comparison with example 4, the production of dimethyl sulfide decreased by 80.9% relative, and the total amount of non-condensable gases by 17.49% relative, with almost the same production of the target product and dimethyl ether.

[0046] Industrial applicability

[0047] The technical result of the proposed invention is an increase in the selectivity and yield of methyl mercaptan both in the main reaction of methanol with hydrogen sulfide and in the processing of by-products of the main reaction, ensuring maximum flexibility in process control and simultaneously reducing capital and operating costs for implementing the method.

[0048] Table 1

Claims

CLAUSES OF THE INVENTION 1. A method for the continuous production of methyl mercaptan by reacting methanol with hydrogen sulfide at elevated temperature and pressure on solid catalysts, followed by separation of the reaction products into the target product, recycled products, unreacted feedstock components and waste streams, mixing the combined flow of recycled reagents with newly fed feedstock components and / or separate feeding of individual recycled reagents into the reactor, characterized in that at least one partition is installed in the reactor to create at least two sequentially located catalytic zones, hermetically connecting the upper and / or lower reactor covers, respectively, with the upper and / or lower tube sheet, or plate, or spiral.

2. The method according to paragraph 1, characterized in that the interaction of methanol with hydrogen sulfide is carried out at a temperature from 280°C to 450°C, a pressure of 5-20 bar, and a molar ratio of hydrogen sulfide to methanol from 1.01 to 20.

3. The method according to claim 1, characterized in that it additionally includes at least one partition connecting the upper and lower tube sheets in the volume of the reactor through which the coolant passes.

4. The method according to claim 1, characterized in that individual components of the raw material and / or reagents returned to the process are introduced into the reactor in various catalytic zones as they are exhausted during the movement of the gas flow through the catalyst.

5. The method according to paragraph 1, characterized in that shell-and-tube, plate or spiral structures are used.

6. The method according to paragraph 5, characterized in that the tubes, plates and spirals of the different catalytic zones have different transverse dimensions.

7. The method according to claim 5, characterized in that the different catalytic zones have a different number of tubes, plates or spirals.

8. The method according to claim 6, characterized in that the various catalytic zones are loaded with catalysts that differ in properties from the catalysts loaded into other catalytic zones.

9. The method according to claim 1, characterized in that individual catalytic zones are loaded in height with catalysts of varying activity or mixtures of catalyst with inert material in various proportions.

10. The method according to claim 1, characterized in that the entire flow of return dimethyl sulfide obtained during the separation of reaction gases and at least part of the flow of return hydrogen sulfide obtained during the separation of reaction gases or its mixture with the initial hydrogen sulfide are fed into the first or several first catalytic zones along the gas flow, filled with a catalyst for the decomposition of dimethyl sulfide.

11. The method according to claim 1, characterized in that the decomposition of dimethyl sulfide in the presence of hydrogen sulfide is carried out in a separate reactor, the outlet stream of which is used as the input stream of the methyl mercaptan synthesis reactor.

12. The method according to any one of paragraphs 1-10, characterized in that one or more catalytic zones, in order to ensure different temperatures in them, have coolant circulation circuits separated by means of partitions in the inter-tube space or collectors, while the heating of the decomposition zones of the returned products is carried out due to the flow of part of the hot coolant between the chambers of the expansion tank.

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