Sequential and independent synthesis of mercaptans and asymmetric sulfides in single reactor

Abstract

The present disclosure generally relates to processes for producing mercaptans and asymmetric sulfides using a stacked bed catalyst system containing CoMo and NiMo, and these processes exhibit a synergistic reduction in the amount of ethylene, methyl mercaptan, ethyl mercaptan, and H2S in the product mixture. In some aspects, the conversion of restrictive reactants in the synthesis of asymmetric sulfides is unexpectedly maintained higher under conditions of increased flow rate through the catalyst bed and reduced temperature and pressure. In further aspects, reactor systems configured for the independent synthesis of mercaptans and asymmetric sulfides in a single fixed bed catalyst vessel are also disclosed as a simplification as existing reactor systems employing separate reactors for separate mercaptan and sulfide synthesis.

Description

[0001] Citation of Related Applications

[0002] This application was filed on August 9, 2023 as a PCT international patent application and claims the benefit and priority of U.S. patent application No. 17 / 884,774 filed on August 10, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to methods and reactor systems for producing mercaptans and asymmetric sulfides using supported catalysts, and related methods and reactor systems for independently producing mercaptans and asymmetric sulfides using layered CoMo / NiMo catalysts. Background Art

[0004] Transulfidation of symmetric sulfides using supported cobalt-molybdenum (CoMo) catalysts is a pathway to synthesize asymmetric sulfides such as methyl ethyl sulfide. Mercaptan synthesis can typically be performed using cobalt-molybdenum catalysts or nickel-molybdenum (NiMo) catalysts. It would be beneficial to have a single reactor system that can perform both asymmetric sulfide synthesis and mercaptan synthesis with high yield and selectivity. Therefore, the present disclosure is generally directed to this purpose. Summary of the invention

[0005] The present invention summary is provided to introduce a series of concepts that will be further described in the detailed description below in a simplified form. The present invention summary is not intended to identify the necessary or essential features of the claimed subject matter. The present invention summary is also not intended to be used to limit the scope of the claimed subject matter.

[0006] Disclosed herein are methods for producing mercaptans and asymmetric sulfides. In one aspect, such methods may sequentially include (a) flowing a first feed mixture comprising hydrogen sulfide (HS) and an olefin through a first catalyst layer of a fixed bed reactor comprising a supported CoMo catalyst, and then flowing through a second catalyst layer of a fixed bed reactor comprising a supported NiMo catalyst to produce a first reaction mixture comprising mercaptans, and (b) flowing a second feed mixture comprising a first symmetric sulfide and a second symmetric sulfide through the first catalyst layer in the fixed bed reactor, and then flowing through the second catalyst layer in the fixed bed reactor to produce a second reaction mixture comprising an asymmetric sulfide.

[0007] A reactor system is also disclosed herein, and in certain aspects, the reactor system may include (i) a fixed bed reactor comprising a reactor inlet for a feed stream, a first catalyst layer comprising a supported CoMo catalyst, a second catalyst layer comprising a supported NiMo catalyst, and a reactor outlet for a reaction mixture, (ii) a first feed source comprising an H2S storage container and an olefin storage container, and (iii) a second feed source comprising a first symmetric sulfide storage container and a second symmetric sulfide storage container. The flow path of the feed stream begins at the reactor inlet, passes through the first catalyst layer, and then passes through the second catalyst layer, and reaches the reactor outlet. In general, the weight ratio of the first catalyst layer to the second catalyst layer is 1:4 to 4:1.

[0008] The foregoing summary of the invention and the following detailed description all provide examples and are illustrative only. Therefore, the foregoing summary of the invention and the following detailed description should not be considered restrictive. In addition, in addition to those features or variations set forth herein, features or variations may also be provided. For example, certain aspects may relate to various feature combinations and sub-combinations described in the embodiments and the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following drawings form part of this specification and are included to further demonstrate certain aspects of the present disclosure. The present disclosure may be better understood by referring to the drawings in combination with the detailed description and examples.

[0010] Figure 1 A schematic block diagram of a representative reactor system for the sequential and independent production of mercaptans and asymmetric sulfides is presented.

[0011] definition

[0012] In order to more clearly define the terms used herein, the following definitions are provided. Unless otherwise indicated, the following definitions apply to the present disclosure. If the term is used in the present disclosure, but is not specifically defined in this article, the definition in IUPAC Compendium of Chemical Terminology, the 2nd edition (1997) can be applied, as long as the definition does not conflict with any other disclosure or definition used in this article, or any claim applying the definition will not be uncertain or invalid. If any definition or usage provided by any file incorporated herein by reference conflicts with the definition or usage provided herein, then the definition or usage provided herein shall prevail.

[0013] In this article, the features of the subject matter are described so that combinations of different features can be envisioned within a particular aspect. For each aspect and each feature disclosed herein, all combinations that do not adversely affect the systems, processes, or methods described herein are considered, with or without explicit description of a particular combination. In addition, unless otherwise explicitly stated, any aspect or feature disclosed herein can be combined to describe a system, process, or method of the present invention consistent with the present disclosure.

[0014] In the present disclosure, although systems and methods are described in a manner of “comprising” various components or steps, unless otherwise specified, the systems and methods may also “consist essentially of” or “consist of” the various components or steps.

[0015] The terms "a", "an", and "the" are intended to include plural alternatives, such as at least one. For example, unless otherwise indicated, disclosure of "a catalyst" is intended to cover one catalyst, or a mixture or combination of more than one catalyst.

[0016] Several types of ranges are disclosed herein. When any type of range is disclosed or claimed, it is intended to disclose or claim each possible number that such range can reasonably cover, including the endpoints of the range and any subranges and combinations of subranges covered therein. For example, the molar ratio of the first and second symmetrical sulfides in the second feed mixture may fall within the range of 10:1 to 1:10. By disclosing that the molar ratio of the first and second symmetrical sulfides in the second feed mixture may be within the range of 10:1 to 1:10, it is intended to state that the molar ratio may be any ratio within the range, for example, any range or range combination of 10:1 to 1:10 may be included, such as 5:1 to 1:5, 4:1 to 1:4, 3:1 to 1:3, 2:1 to 1:2, or 1.5:1 to 1:1.5, etc. Similarly, all other ranges disclosed herein should be interpreted in a manner similar to this example.

[0017] Generally, an amount, size, formulation, parameter, range, or other quantity or characteristic is "about" or "approximately", whether or not expressly stated as such. Whether or not modified by the term "about" or "approximately", the claims include equivalents to the quantities or characteristics.

[0018] Process steps involving flowing a feed mixture through a catalyst bed can be described in terms of weight hourly space velocity (WHSV), or the ratio of the weight of components in the feed mixture that contact a given weight of catalyst per unit time (which can be expressed in units of lb / lb / hour, or alternatively in units of g / g / hour). As used herein, WHSV refers to the flow rate of the total feed mixture past the catalyst, and in certain aspects can be expressed as the total feed mixture flowing past the total amount of supported catalyst in a fixed bed reactor, or as a specified weight of feed mixture flowing past a unit weight of catalyst in a specified period of time, for example, in units of lb / lb / hour.

[0019] Unless otherwise expressly indicated, all disclosed product yields are based on the limiting reactant in the respective reaction. For example, the limiting reactant in the asymmetric sulfide synthesis process may be diethyl sulfide, and thus the conversion and yield are based on the initial amount of diethyl sulfide.

[0020] Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, the typical methods, devices, and materials are described herein.

[0021] All publications and patents mentioned herein are incorporated by reference in their entirety for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications and patents, which might be used in connection with the present disclosure. DETAILED DESCRIPTION

[0022] Disclosed herein is a method for producing mercaptans and asymmetric sulfides in a fixed bed reactor utilizing a stacked bed of a first catalyst layer comprising a supported cobalt-molybdenum (CoMo) catalyst and a second catalyst layer comprising a supported nickel-molybdenum (NiMo) catalyst. The reactor comprising the CoMo / NiMo stacked catalyst layer is capable of independently and efficiently producing mercaptans and asymmetric sulfides in a single reactor without the need to change catalyst beds and / or without the need for multiple reactors.

[0023] catalyst

[0024] As generally described herein, supported CoMo and NiMo catalysts will be understood to refer to cobalt-molybdenum catalysts and nickel-molybdenum catalysts supported on any suitable solid oxide or similar material, as disclosed in U.S. Patent Nos. 4,277,623 and 10,927,074 and U.S. Patent Application Publication No. 2022 / 0106266. For example, a supported CoMo catalyst may contain about 2-4% by weight of cobalt and about 8-16% by weight of platinum supported on alumina, although the respective amounts of Co and Mo are not limited thereto. Similarly, a supported NiMo catalyst may contain about 2-4% by weight of nickel and about 11-17% by weight of platinum supported on alumina. CoMo and NiMo catalysts are not limited to any specific ratio or carrier type of cobalt or nickel to platinum components.

[0025] The absolute amount and relative amount of the supported CoMo and NiMo catalysts of each of the first and second catalyst layers may also be any suitable amount. In some aspects, the ratio of the amount of the catalyst in the first layer to the amount of the catalyst in the second layer may be in the range of 4: 1 to 1: 4, 3: 1 to 1: 3, 2: 1 to 1: 2, 4: 1 to 1: 1 or 1: 1 to 1: 4. In this way, although the amount of the catalyst in the first and second catalyst layers is not necessarily equal, the desired synergistic effect observed by causing the feed stream to flow first through the first catalyst layer including the supported CoMo catalyst and then causing the feed stream to flow through the second catalyst layer including the supported NiMo catalyst can still be achieved. As will be understood by the results and description of the present disclosure, these benefits become relatively more significant as the scale or output increases (and higher WHSV).

[0026] Synthesis of thiols and asymmetric sulfides

[0027] The method for producing mercaptan disclosed herein may include flowing the first feed mixture through a fixed catalyst bed comprising a double-layer CoMo / NiMo catalyst as described herein. In some aspects, the first feed stream may include H2S and olefins, and its amount and relative amount are as disclosed in U.S. Patent Application Publication No. 2022 / 0106266. Non-limiting examples of olefins that may be reactants in the first feed mixture include ethylene, propylene, butene, pentene, hexene, heptene, octene, decene, dodecene, tetradecene, hexadecene, octadecene, cyclopentene, cyclohexene, etc., and combinations thereof. Exemplary and non-limiting examples of mercaptan produced by the method disclosed herein may include methyl mercaptan, ethyl mercaptan, isopropyl mercaptan, sec-butyl mercaptan, etc., and combinations thereof.

[0028] The method for producing asymmetric sulfide by transsulfurization of the first and second symmetrical sulfides can include making the second feed stream comprising the first symmetrical sulfide and the second symmetrical sulfide flow through a fixed catalyst bed-identical to the fixed catalyst bed for producing mercaptan directly described above. In this way, transsulfurization can produce asymmetric sulfide, which contains one of each sulfide group present in the first and second symmetrical sulfide reactants. In some aspects, the first and second symmetrical sulfides can independently include dimethyl sulfide, diethyl sulfide, dibutyl sulfide, dioctyl sulfide or any combination thereof (wherein the first symmetrical sulfide is different from the second symmetrical sulfide). For example, the first symmetrical sulfide can include dimethyl sulfide, and the second symmetrical sulfide can include diethyl sulfide. Therefore, the asymmetric sulfide produced by the transsulfurization process can include methyl ethyl sulfide.

[0029] The molar ratio of the first and second symmetrical sulfides in the second feed stream is not particularly limited, and may generally fall within the range of 10:1 to 1:10. The typical range of the molar ratio of the symmetrical sulfides in the feed stream may include, but is not limited to, 5:1 to 1:5, 4:1 to 1:4, 3:1 to 1:3, 2:1 to 1:2, or 1.5:1 to 1:1.5. In general, the molar ratio may be selected based on cost or availability, or the difficulty of separating one of the symmetrical sulfides in the second feed mixture, so that the component is consumed by the maximum during the process. For example, dimethyl sulfide may be oversupplied in a production unit, and therefore may be provided with a high molar ratio (e.g., about 4:1) relative to the second symmetrical sulfide (such as diethyl sulfide) in the second feed stream. In such cases, the molar ratio of the first and second symmetrical sulfides may be in the range of 1:1 to 10:1, 2:1 to 10:1, 2:1 to 5:1, or 3:1 to 5:1.

[0030] Surprisingly, it is found that a small amount of carbon disulfide can improve the catalytic activity of the CoMo / NiMo catalyst disclosed herein, as demonstrated by the increase in conversion and yield of the process carried out in the presence of carbon disulfide. Therefore, in some aspects, the first and / or second feed streams may also include 500 parts per million by weight (ppmw) to 50,000 ppmw, 1,000 ppmw to 10,000 ppmw, 3,000 ppmw to 7,500 ppmw or 3,500 ppm to 6,500 ppmw of the amount of carbon disulfide. The method disclosed herein may further include adding a certain amount of carbon disulfide (CS2) to the first feed stream, the second feed stream or both, in an amount to achieve any amount required for the carbon disulfide concentration disclosed above. For example, carbon disulfide may be added to the first and / or second feed streams in an amount ranging from 500 ppmw to 25,000 ppmw, from 1000 ppmw to 10,000 ppmw, or from 1,500 ppmw to 4,500 ppmw.

[0031] The operating conditions of a fixed bed reactor containing a CoMo / NiMo stacked catalyst bed for producing mercaptans may be different from the operating conditions of a fixed bed reactor containing a CoMo / NiMo stacked catalyst bed for producing asymmetric sulfides. Representative and non-limiting ranges of the temperature at which the first feed mixture flows through the fixed bed reactor and contacts the CoMo / NiMo stacked catalyst bed (or the temperature at which mercaptans are formed in step (a)) may include 100° C. to 300° C., 125° C. to 275° C., 175° C. to 275° C., 175° C. to 250° C., 200° C. to 300° C., 200° C. to 275° C., or 200° C. to 250° C. These temperature ranges are also intended to encompass situations where the first feed mixture contacts the CoMo / NiMo stacked catalyst bed (or where mercaptan compounds are formed) at a series of different temperatures falling within the respective temperature ranges (rather than at a single fixed temperature), wherein at least one temperature is within the recited range.

[0032] The temperature at which the second feed mixture flows through the fixed bed reactor and contacts with the CoMo / NiMo stacked catalyst bed (or the temperature at which asymmetric sulfide is formed in step (b)) may include the same range as those disclosed in the above-mentioned steps (a) and mercaptan production, or in some aspects, at a higher temperature. For example, the production of mercaptan can be carried out at a relatively low temperature to minimize the impact of the supported CoMo catalyst in the catalyst bed, thereby allowing the first feed mixture to continue to pass through the catalyst bed without too much interaction with the CoMo catalyst. In such aspects, the catalyst bed can be operated like a catalyst bed containing only NiMo. However, when the CoMo catalyst reacts with the second feed mixture, a significant benefit of sulfur conversion reaction can be achieved. In such aspects, the second feed mixture flows through the catalyst bed at a higher temperature than the first reaction mixture. For example, the second feed mixture may flow through the fixed bed reactor and contact the CoMo / NiMo stacked catalyst bed (or may form an asymmetric sulfide in step (b)) at a temperature of 200°C to 500°C, such as 225°C to 450°C, 250°C to 350°C, 250°C to 300°C, 270°C to 300°C, or 280°C to 290°C.

[0033] The interaction between the first and second feed mixtures and the catalyst bed may be proportional to any one of the flow rate of the respective feed streams, the amount of catalyst in the fixed bed reactor, and the concentration of the reactants in the respective feed mixtures. Therefore, the process step in which the respective feed mixture flows through the catalyst bed can be described by the weight hourly space velocity (WHSV) as defined herein. The WHSV of the first or second feed mixture flowing through the reactor to produce mercaptans or asymmetric sulfides, respectively, may have a minimum value of 0.01, 0.1, 0.2, 0.5, 1 or 2; or alternatively, a maximum value of 10, 8, 7, 5, 4 or 2. In general, the WHSV may be in the range of any minimum WHSV disclosed herein to any maximum WHSV disclosed herein. In non-limiting aspects, the WHSV in step (a) and / or step (b) may be in the range of 0.1 to 5; alternatively, in the range of 1 to 5; or alternatively, in the range of 2 to 4. Other WHSV ranges are apparent in the present disclosure.

[0034] Although not limited thereto, step (a) and step (b) may be independently performed at a reaction pressure in the range of 25 pounds per square inch gauge (psig) to 1000 psig (172 kPag to 6890 kPag). Other representative and non-limiting ranges of reaction pressure may include 25 to 500 psig (172 kilopascal gauge (kPag) to 3447 kPag), 50 psig to 800 psig (344 kPag to 5515 kPag), 50 psig to 450 psig (344 kPag to 3103 kPag), 200 psig to 450 psig (1379 kPag to 3103 kPag), 50 psig to 250 psig (344 kPag to 1722 kPag), or 100 psig to 200 psig (689 kPag to 1379 kPag).

[0035] Advantageously, the reaction conditions of step (a) and step (b) are independent and can be tailored according to the desired mercaptan product and the desired asymmetric sulfide product. In certain aspects, step (a) can be carried out at a temperature in the range of 150° C. to 250° C., a pressure in the range of 350 psig to 550 psig, and a WHSV of 0.2 to 1. In certain aspects, step (b) can be carried out at a temperature in the range of 270° C. to 300° C., a pressure in the range of 100 psig to 200 psig, and a WHSV in the range of 2 to 4.

[0036] In general, the methods described herein result in unexpectedly high conversions of limiting reactants and / or the yields of asymmetric sulfides or mercaptan products, particularly when the WHSV is reduced due to the long contact time of the reactants with the catalyst bed. In one aspect, the minimum conversion (or yield) may be at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95%. In addition, the maximum conversion (or yield) may be 97%, 98%, 99%, or 99.5%, and may approach 100% conversion of the limiting reactant (or the yield of asymmetric sulfides and / or mercaptan). In general, the conversion (or yield) may be in the range of any minimum conversion (or yield) disclosed herein to any maximum conversion (or yield) disclosed herein. The non-limiting range of the conversion (or yield) may include 50% to 99.5%, 80% to 99%, 90% to 98%, or 95% to 100%.

[0037] When controlling higher WHSV (for example, about 3 or higher), conversion rate and yield still remain excellent. When WSHV is 3, the non-limiting range of the conversion rate of asymmetric sulfide (for example, diethyl sulfide) may include 65% to 95%, 75% to 80%, 80% to 90% or 82% to 88%. It is considered that these conversions are carried out under any suitable reaction conditions disclosed above, for example, at a reaction temperature of 285° C. and a pressure of 150psig, but is not limited thereto. For conversion rate, the percentage is the amount of the limiting reactant converted based on the initial amount of the limiting reactant. The yield value is a molar percentage, and is based on the mole number of the asymmetric sulfide produced (for example, the mole number of methyl ethyl sulfide in the embodiment disclosed herein) and the mole number of the limiting reactant (for example, diethyl sulfide).

[0038] Without being bound by theory, it is believed that utilizing relatively mild reaction conditions during the production of mercaptans can result in stacked CoMo / NiMo stacked bed catalysts approaching the performance of 100% NiMo catalysts, as disclosed in U.S. Patent Application Publication No. 2022 / 0106266. As a non-limiting example, the method for producing mercaptans can be carried out at a reactor temperature below 235°C to prevent significant interaction between the supported CoMo catalyst layers. In this way, the production of mercaptans and asymmetric sulfides may be unexpectedly well suited for use within a single reactor system comprising a CoMo / NiMo layered catalyst bed. Surprisingly, the advantages of producing asymmetric sulfides using the CoMo / NiMo stacked bed catalyst disclosed herein relative to processes for producing mercaptans using a 100% NiMo catalyst bed do not require sacrificing yield and conversion during the production of mercaptans in subsequent processes.

[0039] Thus, the mercaptan synthesis disclosed herein can be operated under reactor conditions where the CoMo catalyst bed may have little to no activity to a first reagent stream comprising H2S and olefins. In certain aspects, the method for producing mercaptan may include flowing the first reagent stream through the reactor at a temperature in the range of 100°C to 300°C, 175°C to 275°C, or 150°C to 250°C. In other aspects, the flow of the first reagent stream through the reactor may be carried out at a reactor pressure in the range of 50psig to 1000psig, 100psig to 800psig, 300psig to 600psig, or 200psig to 400psig. In certain aspects, the molar ratio of H2S:olefins may be in the range of 3:1 to 30:1, 3:1 to 10:1, 4:1 to 30:1, 5:1 to 20:1, or 10:1 to 15:1. In certain aspects, flowing the first reagent stream comprising a thiol compound through the reactor can comprise a WHSV in a range of 0.01 to 3, 0.05 to 1.5, 0.2 to 1, 0.01 to 10, 1 to 10, or 2 to 4.

[0040] In addition to the above characterization of yield and conversion, the production of asymmetric sulfides and mercaptans as disclosed herein can be characterized relative to a given set of reaction conditions and other catalyst systems. For example, the conversion of a symmetric sulfide (or the yield of the resulting asymmetric sulfide) using a stacked bed catalyst comprising a first catalyst layer (comprising a supported CoMo catalyst) and a second catalyst layer (comprising a supported NiMo catalyst) can be higher than the conversion of an otherwise identical process comprising a different catalyst component or arrangement. In certain aspects, the conversion or yield can be greater (e.g., at least 0.5% greater, at least 1% greater, at least 2% greater, at least 3% greater, or at least 5% greater) than the conversion or yield observed using: (1) a single layer of supported NiMo catalyst, or (2) a single layer of supported CoMo catalyst, or (3) a mixed catalyst bed comprising a mixture of supported NiMo catalyst and supported CoMo catalyst, or (4) a stacked bed catalyst in which the order of the NiMo catalyst and the CoMo catalyst is reversed (i.e., the first catalyst layer comprises a supported NiMo catalyst and the second catalyst layer comprises a supported CoMo catalyst), or any combination thereof.

[0041] Surprisingly, while the process utilizing the CoMo / NiMo stacked bed catalyst exhibits synergistic improvements in the conversion of the limiting symmetric sulfide reactant and the yield of the resulting asymmetric sulfide, it is also observed that the process disclosed herein does not result in a significant increase in the amount of mercaptan byproduct present in the second reaction mixture. In addition, the amount of HS is virtually unchanged relative to the process with a lower conversion of the limiting symmetric sulfide reactant. In certain processes contemplated herein, the amount of ethylene, HS, methyl mercaptan or methyl mercaptan (MeSH), ethyl mercaptan or ethyl mercaptan (EtSH), or any combination thereof may be within 1%, within 0.5%, within 0.3%, within 0.2%, within 0.1%, equal to, or less than that of a process for producing asymmetric sulfides utilizing: (1) a single layer of supported NiMo catalyst, or (2) a single layer of supported CoMo catalyst, or (3) a mixed catalyst bed comprising a mixture of supported NiMo catalyst and supported CoMo catalyst, or (4) a stacked bed catalyst in which the order of the NiMo catalyst and the CoMo catalyst is reversed (i.e., the first catalyst layer comprises a supported NiMo catalyst and the second catalyst layer comprises a supported CoMo catalyst), or any combination thereof.

[0042] In many cases, it is desirable to separate asymmetric sulfide and / or mercaptan from respective reaction mixtures for sale or for further industrial processes. Therefore, in some aspects, the method for producing asymmetric sulfide and mercaptan may further include the step of separating asymmetric sulfide (or separating mercaptan compounds) from respective reaction mixtures by any suitable technology to form a product stream (or a product stream containing mercaptan) containing asymmetric sulfide. Suitable technology may include but is not limited to extraction, filtration, evaporation or distillation, and a combination of two or more of these technologies. In a particular aspect of the present disclosure, the separation step utilizes distillation (wherein one or more than one distillation tower may be used) under any suitable pressure. Advantageously, the low level of mercaptan in the second reaction mixture makes it possible to separate via distillation for example asymmetric sulfide (such as methyl ethyl sulfide) into a relatively simple process. After the separation step, the purity of asymmetric sulfide (or mercaptan) in product stream may be at least 80 wt %, at least 85 wt %, at least 90 wt %, at least 95 wt % or at least 98 wt %.

[0043] Reactor system

[0044] A reactor system consistent with the present disclosure may include (i) a fixed bed reactor including a reactor inlet for a feed stream, a first catalyst layer including a supported CoMo catalyst, a second catalyst layer including a supported NiMo catalyst, and a reactor outlet for a reaction mixture, (ii) a first feed source including an H2S storage container and an olefin storage container, and (iii) a second feed source including a first symmetric sulfide storage container and a second symmetric sulfide storage container. In the reactor system, the flow path of the feed stream starts at the reactor inlet, passes through the first catalyst layer, and then passes through the second catalyst layer, and reaches the reactor outlet, and the weight ratio of the first catalyst layer to the second catalyst layer ranges from 1:4 to 4:1.

[0045] Catalysts suitable for use in the reactor systems disclosed herein can be any catalyst as described above, and are suitable for producing mercaptans and asymmetric sulfides, and are suitable for downstream processing. For example, in certain aspects, the supported CoMo catalyst and the supported NiMo catalyst can each be independently supported on silica, alumina, silica-alumina, aluminum phosphate, zinc aluminate, zirconium oxide, thoria, etc. In certain aspects, either or both of the supported CoMo catalyst and the supported NiMo catalyst can comprise an alumina support.

[0046] Surprisingly, the reactor system disclosed herein is able to accommodate the production of both mercaptans and asymmetric sulfides in a single reactor system without the need for separate equipment or interchange of catalysts and flow paths through catalyst beds. Integrated catalyst systems have previously been described for producing both mercaptans and asymmetric sulfides via separate reactors as part of a carefully coordinated system of feed streams, products, and recovery of by-products. Therefore, previously disclosed integrated systems are limited by the reliance on separate reactors for synthesizing mercaptans and asymmetric sulfides.

[0047] In contrast, the reactor system disclosed herein can be configured to produce mercaptan and asymmetric sulfide in a single reactor, including the arrangement of two independent reagents and product streams in a single reactor. In some aspects, the reactor system may include a feed selection valve, which is located in a feed stream between a fixed bed reactor (e.g., a reactor inlet of a fixed bed reactor) and the first and second feed sources. The feed selection valve can be connected to each of the first and second feed sources and the reactor inlet fluid, and therefore can be used in which the first feed stream is delivered to the first position of the reactor inlet from the first feed source. The feed selection valve can also be used in which the second feed stream is delivered to the second position of the reactor inlet from the second feed source. In this way, each of the first and second feed streams can be delivered to a fixed bed reactor to carry out sequential and independent processes, thereby producing mercaptan and asymmetric sulfide as disclosed herein.

[0048] Similarly, the reaction system disclosed herein may include a product selection valve located between the reactor outlet and the first and second product streams of the reactor system. Similar to the feed selection valve, the product selection valve may adopt a first position, thereby delivering the reaction mixture from the reactor outlet to either of the first or second product stream lines. In this way, a single catalyst bed (e.g., a catalyst bed comprising supported CoMo / NiMo) may receive feed streams associated with both mercaptan synthesis and asymmetric sulfide synthesis, and deliver the reaction mixture to their respective downstream processes without the need to exchange components or catalysts within the reactor system.

[0049] Reactor systems disclosed herein may include additional components arranged as needed to maintain reaction conditions disclosed above. For example, with respect to the temperature in the reactor and the catalyst bed, a fixed bed reactor may include a heating jacket around the catalyst bed to control the temperature in the reactor and / or maintain the temperature within the expected range of producing mercaptan or asymmetric sulfide. Additionally or alternatively, the feed source pipeline may include a preheater to raise its temperature before the reagent mixture enters the reactor, and ensure that in the entire reaction process, even when the feed stream enters the reactor, the temperature in the reactor is maintained. Reactor components for regulating and maintaining reaction pressure and additional reaction parameters (e.g., feed stream flow rate, reagent concentration) are also contemplated herein, and the reactor components are understood by those skilled in the art.

[0050] As will be appreciated by those skilled in the art, controllers and analytical modules for monitoring reactor conditions, feed streams, product streams, etc. are also contemplated within the reactor systems disclosed herein. The first and second feed sources are not limited to any particular sources, and may be any source that provides a feed stream or components thereof in a form suitable for the reaction.

[0051] Figure 1A representative fixed bed reactor system 100 consistent with aspects of the present disclosure is illustrated. As shown, the reactor system 100 includes a fixed bed reactor 150, wherein a feed stream inlet 148 leads to the reactor and leads downward to a reaction mixture outlet 154. As will be appreciated by those skilled in the art, the fixed bed reactor 150 may be equipped with a jacket heater to maintain a suitable reaction temperature within the reactor. The fixed bed reactor 150 includes a double-layer catalyst bed as described above, the double-layer catalyst bed having a first catalyst layer 151 including a supported CoMo catalyst, which is positioned to first contact the downward feed stream flowing from the inlet 148 to the outlet 154, and then contact the second catalyst layer 152 including a supported NiMo catalyst. The first reactant line 132 and the second reactant line 134 enter the feed selection valve 140, which further directs the selected feed stream from the first reactant line 132 or the second reactant line 134 to the reactor feed 145, and then to the reactor 150 via the inlet 148. Similarly, reaction products 155 deliver the product mixture exiting reactor 150 via reactor outlet 154 to product selector valve 160 , which further directs the product streams to respective first product line 162 or second product line 164 .

[0052] If selected by feed selection valve 140, the first reactant line 132 connected to the H2S storage container and the olefin storage container (not shown) delivers the H2S-olefin feed stream to the reactor 150, thereby producing a mercaptan product, which is transmitted to the first product line 162 through the product selection valve 160. Similarly, if selected by feed selection valve 140, the second reactant line 134 connected to the first symmetric sulfide storage container and the second symmetric sulfide storage container (not shown) delivers the mixed sulfide feed stream to the reactor 150, thereby producing an asymmetric sulfide product, which is transmitted to the second product line 164 through the product selection valve 160. The storage container referred to herein may include one or more physical storage containers (e.g., tanks) capable of long-term storage and regular replenishment. In other aspects, such as in an integrated reactor system, the storage container considered herein may include a crude product stream or a purified product stream of the integrated reactor system.

[0053] The reactor system 100 may also include sensors configured to monitor reaction parameters (e.g., temperature, pressure, flow rate) and status of components within the reactor system 100. An analysis module 180 is provided as a means for receiving system information (e.g., reaction parameters) and transmitting data 185, shown in connection with a controller 190, which then controls or adjusts any aspect of the reactor system 100 (e.g., increasing or decreasing reaction temperature, increasing or decreasing feed stream flow rate entering the reactor) via a control output 195 based on the data 185 from the analysis module 180.

[0054] Example

[0055] The present disclosure is further illustrated by the following examples, which should not be construed as limiting the scope of the present disclosure in any way. Various other aspects, modifications and equivalents thereof may occur to one of ordinary skill in the art after reading the description herein without departing from the spirit of the present disclosure or the scope of the appended claims. These examples demonstrate that reaction conditions favorable for mercaptan synthesis may also produce favorable results in transsulfurization reactions utilizing a double-layer catalyst comprising a first layer (top layer) comprising a supported CoMo catalyst and a second layer (bottom layer) comprising a supported NiMo catalyst.

[0056] In each of Examples 1-16, the transsulfurization reaction was carried out using a feed stream prepared by blending dimethyl sulfide (DMS) and diethyl sulfide (DES) in a molar ratio of 4:1. The DMS and DES mixture was fed to the top of a fixed bed reactor containing an appropriate catalyst. Carbon disulfide was also present in the feed stream as a residue from dimethyl sulfide production in an amount of about 3000 ppmw (0.3 wt %). For Examples 1-12, a double catalyst bed was employed, (i) supported CoMo on alumina, and (ii) supported NiMo on alumina, in a weight ratio of 1:1. Examples 13-16 examined alternative catalyst arrangements as discussed in detail below.

[0057] The results of the experiments performed in Examples 1-16 are provided in Tables I-III and determined by gas chromatography (GC) performed on an Agilent 7890 AGC system (Agilent Technologies, Wilmington, DE, USA) using an Agilent HP-5 GC column (dimethylpolysiloxane, capillary 30 m x 0.32 μm x 0.25 μm, nominal) with a program of 35°C temperature hold for 5 min, followed by a ramp from 35°C to 70°C at a rate of 5°C / min, followed by a ramp to 260°C at 15°C / min, and then held at 260°C for 10 min. Dimethyl sulfide (DMS), diethyl sulfide (DES), and methyl ethyl sulfide (MES) standards were used to identify the respective reactants and products. WHSV was calculated as described herein based on the total weight of DES in contact with the catalyst per unit time.

[0058] Unexpectedly, even under conditions favorable for mercaptan synthesis, a stacked bed catalyst comprising a CoMo catalyst as the first layer and a NiMo catalyst as the second layer converts high levels of diethyl sulfide (e.g., greater than 80-85 mole %) and produces only minimal amounts of light byproducts and unreacted reactants in the product mixture. Examples 1-16 demonstrate that the transsulfurization reaction converts DMS and DES primarily into methyl ethyl sulfide (MES).

[0059] Examples 1-6

[0060] Favorable asymmetric sulfide reaction conditions were evaluated to complement thiol synthesis protocols.

[0061] In Examples 1-6, the reaction conditions for transsulfurization were varied according to temperature, pressure, and flow rate (weight hourly space velocity (WHSV)) of the reactants through the reactor. Each of Examples 1-6 was conducted using a stacked bed catalyst comprising a first layer (top layer) of CoMo catalyst and a second layer (bottom layer) of NiMo catalyst. The results are shown in Table 1.

[0062] Examples 1-3 examine the effect of temperature on the transsulfurization reaction, holding pressure, and flow rate / WSHV constants. As expected, the conversion of the reactants generally increases with increasing temperature from 270° C. to 300° C., but surprisingly, the amount of byproducts increases significantly at 300° C., causing the total yield of methyl ethyl sulfide to decrease above 285° C. At a temperature of 270° C., a significant reduction in the amount of unwanted light (e.g., HS, MeSH, EtSH) in the product mixture was also observed, however, this reduction was accompanied by a decrease in diethyl sulfide conversion and, therefore, a decrease in the yield of methyl ethyl sulfide.

[0063] Example 4 examined the effect of increasing the flow rate of the reactant mixture through the catalyst bed. As expected, due to the reduced contact time with the catalyst, the conversion of diethyl sulfide decreased significantly compared to the results illustrated in Example 2. The amount of lights produced as unwanted byproducts was not greatly reduced, and higher amounts of EtSH were produced.

[0064] Embodiment 5-6 examines the influence of reducing the pressure in the reactor.Although lower pressure is expected to result in lower yield and conversion of limiting reactants, carrying out transsulfurization reaction under lower pressure can advantageously allow transsulfurization reaction to be carried out on the equipment conventionally used for mercaptan synthesis.Example 5-6 is carried out under the reduced pressure of 150psig and 100psig respectively.Surprisingly, although the reaction pressure is reduced to 150psig (only 50% of the pressure in embodiment 1-4), the conversion of diethyl sulfide remains higher than 80%.Similarly, the diethyl sulfide conversion observed in embodiment 6 (100psig) is also close to 80%.In addition, relative to the embodiment of higher pressure, the amount of light produced is reduced.Therefore, the excellent results of transsulfurization reaction under relatively mild conditions show that the reaction can be carried out in the reactor system that is usually adopted under lower pressure and temperature, such as the equipment dedicated to the production of mercaptan synthesis.

[0065] Examples 7-12

[0066] The impact of adding CS2 and recovering lights in an asymmetric sulfide feed stream was evaluated.

[0067] In Examples 7-12, the effect of the composition of the feed stream on the conversion rate and the amount of by-products produced was examined. Similar to Examples 1-6, each of Examples 7-12 was conducted using the same stacked bed catalyst comprising a first layer (top layer) of CoMo catalyst and a second layer (bottom layer) of NiMo catalyst. The results are shown in Table II.

[0068] Examples 7-8 examined the effect of carbon disulfide present in the reaction feed. Example 7 represents a feed mixture with a low CS2 concentration (i.e., less than 3000 ppmw). Example 8 provides an additional 1905 ppmw CS2 to the feed stream of Example 7. As shown in Table II, the conversion of the low CS2 reactant feed is significantly lower than that of Example 8, in which CS2 is added to the feed stream.

[0069] Embodiment 9-12 examines the influence of light in reactant feed stream, and described light may exist due to some component in recovery product stream.In closed reactor system, the unwanted light of production needs to be separated from product mixture (for example, by fractionation) and as waste treatment or preferably reclaimed in process.In embodiment 9-11, MeSH is added to the amount of 2.2 weight % in feed stream.Also checked this feed stream with MeSH addition, it has low CS2 level (no CS2 is added, total CS2 is less than 3000ppmw), medium CS2 level (add 1905ppmw CS2, total CS2 is 3000ppmw to 5000ppmw) and high CS2 level (add 3810ppmw CS2, total CS2 is 5000ppmw to 7000ppmw).Example 12 adopts the feed stream with 0.7% EtSH and 0.1 weight % CS2.

[0070] The amount of CS2 in the feed stream initially improves conversion, but this improvement appears to diminish after reaching an amount of about 5000 ppmw. Specifically, the conversion of diethyl sulfide observed in the medium CS2 feed stream of Example 10 is about 8% higher than the conversion of the low CS2 feed stream (Example 9). However, in the high CS2 Example 11, increasing the same amount of CS2 results in a further increase of less than 2%.

[0071] Surprisingly, it was also noted that the presence of light byproducts was generally well tolerated despite the addition of approximately three to five times the amount of light byproducts to the transsulfurization feed streams of Examples 9-12 compared to the amounts observed in the transsulfurization product mixtures examined, such as in Example 8. Thus, it was determined that the amount of unwanted lights produced could be recycled back into the feed stream without significantly affecting the conversion or yield of these processes.

[0072] Examples 13-16

[0073] Asymmetric sulfide synthesis over alternative arrangements of CoMo and NiMo catalysts was evaluated.

[0074] In Examples 13-16, the effect of the composition and arrangement of the catalyst within the fixed bed reactor on conversion, yield, and production of light by-products in the product mixture was examined. Examples 13-16 are summarized in Table III, compared to Example 8, which utilized a stacked bed catalyst comprising a first layer (top layer) of CoMo catalyst and a second layer (bottom layer) of NiMo catalyst.

[0075] Example 13 utilized a stacked bed catalyst in which the positions of the first and second catalyst layers were reversed relative to Example 8, i.e., the stacked bed catalyst consisted of a first layer (top layer) of a supported NiMo catalyst and a second layer (bottom layer) of a supported CoMo catalyst. Example 14 utilized a single catalyst layer consisting of a mixture of a supported CoMo catalyst and a supported NiMo catalyst in a weight ratio of 1:1. Examples 15 and 16 utilized a single catalyst layer having only a supported CoMo catalyst, or a single catalyst layer having only a supported NiMo catalyst, respectively.

[0076] As shown in Table III, a decrease in conversion was observed in each of the alternative catalyst arrangements of Examples 13-16 relative to Example 8. Surprisingly, the CoMo / NiMo stacked bed catalyst of Example 8 outperformed each of Examples 13-16 in both diethyl sulfide conversion and methyl ethyl sulfide yield. In particular, each of Examples 8, 13-14, and 16, which employed at least some portion of the supported NiMo catalyst in the catalyst bed, performed much better than the 100% CoMo catalyst utilized in Example 15, indicating that the supported NiMo catalyst may be more effective in transsulfurization than a similar CoMo catalyst. This was further demonstrated by Examples 13-14, where a slight decrease in conversion and yield relative to the 100% NiMo catalyst of Example 16 was observed, and the decrease may be attributed to the proportional dilution of the efficacy after including the CoMo catalyst.

[0077] Surprisingly, the performance of using CoMo as the first layer of the CoMo / NiMo stacked bed catalyst (Example 8) was superior to each of Examples 13-16, including Example 15 in which a 100% NiMo catalyst bed was used. In addition, Example 8 showed that there was no increase in the amount of H2S produced during the reaction, and only a moderate increase in the amount of MeSH and EtSH relative to Examples 13-16. Therefore, without being bound by theory, it is believed that when a catalyst bed comprising a first layer of CoMo is accompanied by a NiMo catalyst as a second layer in the catalyst bed, the catalyst bed will provide a synergistic benefit for the transsulfurization reaction.

[0078]

[0079] The present disclosure is described above with reference to many aspects and specific embodiments. Based on the above specific embodiments, many variations will occur to those skilled in the art. All such obvious variations are within the full intended scope of the appended claims. Other aspects of the present disclosure may include, but are not limited to, the following (aspects are described as "comprising", but alternatively, may be "essentially composed of" or "consisting of"):

[0080] Aspect 1. A method for sequentially producing mercaptans and asymmetric sulfides, the method comprising: (a) flowing a first feed mixture comprising H2S and olefins through a first catalyst layer of a fixed bed reactor comprising (or essentially consisting of or consisting of) a supported CoMo catalyst, and then through a second catalyst layer of the fixed bed reactor comprising (or essentially consisting of or consisting of) a supported NiMo catalyst, to produce a first reaction mixture comprising the mercaptans; and (b) flowing a second feed mixture comprising a first symmetric sulfide and a second symmetric sulfide through the first catalyst layer in the fixed bed reactor, and then through the second catalyst layer in the fixed bed reactor, to produce a second reaction mixture comprising the asymmetric sulfide.

[0081] Aspect 2. The method of aspect 1, wherein the first feed mixture flows through the fixed bed reactor at any temperature from 150°C to 250°C and any pressure from 25 psig to 450 psig.

[0082] Aspect 3. The method according to aspect 1 or 2, wherein the olefin comprises ethylene, propylene, 1-butene or a combination thereof.

[0083] Aspect 4. The method according to any one of aspects 1 to 3, wherein the mercaptan comprises isopropyl mercaptan, sec-butyl mercaptan, or a combination thereof.

[0084] Aspect 5. The method of any one of aspects 1 to 4, wherein the first feed mixture flows through the fixed bed reactor at a WHSV in the range of 0.01 to 10 (or 0.1 to 2).

[0085] Aspect 6. A method as described in any of Aspects 1 to 5, wherein the second feed mixture flows through the fixed bed reactor at any temperature from 250°C to 350°C (or 270°C to 300°C); at any pressure from 25psig to 400psig (or 50psig to 250psig); and at any WHSV from 0.1 to 10 relative to the limiting reactant (e.g., diethyl sulfide).

[0086] Aspect 7. The method of any one of aspects 1 to 6, wherein the first symmetric sulfide and the second symmetric sulfide independently comprise dimethyl sulfide, diethyl sulfide, dipropyl sulfide, dibutyl sulfide, dioctyl sulfide, or any combination thereof.

[0087] Aspect 8. The method of any one of aspects 1 to 7, wherein the first symmetric sulfide comprises dimethyl sulfide, the second symmetric sulfide comprises diethyl sulfide, and the asymmetric sulfide comprises methyl ethyl sulfide.

[0088] Aspect 9. The method according to aspect 8, wherein the molar ratio of dimethyl sulfide to diethyl sulfide in the second feed mixture is from 1:1 to 10:1, or from 2:1 to 5:1.

[0089] Aspect 10. The method of any one of aspects 1 to 9, wherein the second feed mixture further comprises 2,500 ppmw to 10,000 ppmw (or 3,500 ppmw to 6,500 ppmw) of carbon disulfide.

[0090] Aspect 11. The method of any one of aspects 1 to 10, wherein the second feed mixture flows through the fixed bed reactor at any WHSV of 2 to 4.

[0091] Aspect 12. The method according to any one of aspects 8 to 11, wherein the conversion rate of diethyl sulfide is 60 mol% to 90 mol%.

[0092] Aspect 13. The method according to any one of aspects 8 to 12, wherein the yield of methyl ethyl sulfide in the second mixture is 38 to 50 wt % based on the amount of diethyl sulfide.

[0093] Aspect 14. A method as described in any one of Aspects 1 to 13, wherein the amount of lights (e.g., H2S, MeSH, EtSH) in the second reaction mixture is less than or equal to 5 wt.%, or less than or equal to 2 wt.%.

[0094] Aspect 15. A method as described in any one of Aspects 1 to 14, wherein under the same reaction conditions, the yield of the asymmetric sulfide (or the conversion rate of the limiting sulfide reactant) is higher than the yield of an otherwise identical method wherein the first catalyst layer is the supported NiMo catalyst and the second catalyst layer is the supported CoMo catalyst.

[0095] Aspect 16. A method as described in any one of Aspects 1 to 15, wherein under the same reaction conditions, the yield of the asymmetric sulfide (or the conversion rate of the limiting sulfide reactant) is higher than the yield of an otherwise identical method wherein the fixed bed reactor comprises a mixed bed of the supported NiMo catalyst and the supported CoMo catalyst.

[0096] Aspect 17. A method as described in any one of Aspects 1 to 16, wherein under the same reaction conditions, the yield of the asymmetric sulfide (or the conversion rate of the limiting sulfide reactant) is higher than the yield of an otherwise identical method wherein the fixed bed reactor comprises a single catalyst layer consisting of the supported NiMo catalyst or the supported CoMo catalyst.

[0097] Aspect 18. The method of any one of aspects 15 to 17, wherein the second reaction mixture comprises less residual ethylene, methyl mercaptan, ethyl mercaptan, or any combination thereof than the otherwise identical method.

[0098] Aspect 19. The method according to any one of aspects 1 to 18, wherein the supported NiMo catalyst comprises an alumina support, the supported CoMo catalyst comprises an alumina support, or both.

[0099] Aspect 20. The method of any one of Aspects 1 to 19, wherein a weight ratio of the first catalyst layer of the supported CoMo catalyst to the second catalyst layer of the supported NiMo catalyst is 1:4 to 4:1, or 1:1.5 to 1.5:1.

[0100] Aspect 21. A reactor system comprising: (i) a fixed bed reactor comprising a reactor inlet for a feed stream, a first catalyst layer comprising a supported CoMo catalyst, a second catalyst layer comprising a supported NiMo catalyst, and a reactor outlet for a reaction mixture, wherein a flow path of the feed stream starts from the reactor inlet, passes through the first catalyst layer, and then passes through the second catalyst layer, and reaches the reactor outlet, and a weight ratio of the first catalyst layer to the second catalyst layer is 1:4 to 4:1, (ii) a first feed source comprising an H2S storage container and an olefin storage container, and (iii) a second feed source comprising a first symmetric sulfide storage container and a second symmetric sulfide storage container.

[0101] Aspect 22. The system of aspect 21, wherein the supported CoMo catalyst is supported on alumina, the supported NiMo catalyst is supported on alumina, or both.

[0102] Aspect 23. A system as described in Aspect 21 or 22, wherein the system further comprises a feed selection valve located between the fixed bed reactor and the first feed source and the second feed source, the feed selection valve being configured to operate between: a first feed position that delivers a first feed stream comprising H2S and olefins from the first feed source to the reactor inlet; and a second feed position that delivers a second feed stream comprising a first symmetric sulfide and a second symmetric sulfide from the second feed source to the reactor inlet.

[0103] Aspect 24. A system as described in any of Aspects 21 to 23, wherein the system further includes a product selection valve located between the fixed bed reactor and the first product pipeline and the second product pipeline, and the product selection valve is configured to operate between: a first product position, which delivers the reaction mixture from the reactor outlet to a mercaptan product stream; and a second product position, which delivers the reaction mixture from the reactor outlet to an asymmetric sulfide product stream.

Claims

1. A method for sequentially producing a mercaptan and an asymmetric sulfide, the method comprising: (a) flowing a first feed mixture comprising H2S and olefins through a first catalyst layer of a fixed bed reactor comprising a supported CoMo catalyst and then through a second catalyst layer of the fixed bed reactor comprising a supported NiMo catalyst to produce a first reaction mixture comprising the mercaptan; and (b) flowing a second feed mixture comprising a first symmetric sulfide and a second symmetric sulfide through the first catalyst layer in the fixed bed reactor, and then flowing through the second catalyst layer in the fixed bed reactor to produce a second reaction mixture comprising the asymmetric sulfide.

2. The process of claim 1, wherein the first feed mixture flows through the fixed bed reactor under the following conditions: Temperature from 150°C to 250°C; Pressures from 25 psig to 450 psig; and WHSV on a scale of 1 to 10.

3. The method of claim 1 or 2, wherein the olefin comprises ethylene, propylene, 1-butene or a combination thereof.

4. The method of any one of claims 1 to 3, wherein the mercaptan comprises isopropyl mercaptan, sec-butyl mercaptan, or a combination thereof.

5. The process of any one of claims 1 to 4, wherein the second feed mixture flows through the fixed bed reactor under the following conditions: Temperatures from 250°C to 350°C; Pressures from 25 psig to 400 psig; and WHSV of 2 to 4.

6. The method of any one of claims 1 to 5, wherein the first symmetric sulfide and the second symmetric sulfide independently comprise dimethyl sulfide, diethyl sulfide, dipropyl sulfide, dibutyl sulfide, dioctyl sulfide, or any combination thereof.

7. The method according to any one of claims 1 to 6, wherein: The first symmetrical sulfide comprises dimethyl sulfide; The second symmetrical sulfide comprises diethyl sulfide; and The asymmetric sulfide includes methyl ethyl sulfide.

8. The method of claim 7, wherein the molar ratio of dimethyl sulfide to diethyl sulfide in the second feed mixture is 2:1 to 5:

1.

9. The process of any one of claims 1 to 8, wherein the second feed mixture further comprises 3,500 ppmw to 6,500 ppmw carbon disulfide.

10. The process according to any one of claims 7 to 9, wherein the conversion of diethyl sulfide is 60 mol% to 90 mol%.

11. The method of any one of claims 7 to 10, wherein the yield of methyl ethyl sulfide in the second reaction mixture is 38 wt% to 50 wt%.

12. The method of any one of claims 1 to 11, wherein under the same reaction conditions, the conversion rate of either the first asymmetric sulfide or the second asymmetric sulfide is higher than the conversion rate of an otherwise identical method in which the first catalyst layer is the supported NiMo catalyst and the second catalyst layer is the supported CoMo catalyst.

13. The process of any one of claims 1 to 12, wherein the conversion of either the first asymmetric sulfide or the second asymmetric sulfide is higher than the conversion of an otherwise identical process wherein the fixed bed reactor comprises a mixed bed of the supported NiMo catalyst and the supported CoMo catalyst under the same reaction conditions.

14. The process of any one of claims 1 to 13, wherein the conversion of either the first asymmetric sulfide or the second asymmetric sulfide is higher than the conversion of an otherwise identical process wherein the fixed bed reactor comprises a single catalyst layer consisting of the supported NiMo catalyst or the supported CoMo catalyst under the same reaction conditions.

15. The method of any one of claims 1 to 14, wherein the supported NiMo catalyst comprises an alumina support, the supported CoMo catalyst comprises an alumina support, or both.

16. The method of any one of claims 1 to 15, wherein a weight ratio of the first catalyst layer of the supported CoMo catalyst to the second catalyst layer of the supported NiMo catalyst is 1:4 to 4:

1.

17. A reactor system comprising: (i) a fixed bed reactor comprising: a reactor inlet for a feed stream; a first catalyst layer comprising a supported CoMo catalyst; a second catalyst layer comprising a supported NiMo catalyst; and a reactor outlet for the reaction mixture; in: The flow path of the feed stream starts at the reactor inlet, passes through the first catalyst layer, and then passes through the second catalyst layer, and reaches the reactor outlet; and The weight ratio of the first catalyst layer to the second catalyst layer is 1:4 to 4:1; (ii) a first feed source comprising an H2S storage vessel and an olefin storage vessel; and (iii) a second feed source comprising a first symmetric sulfide storage vessel and a second symmetric sulfide storage vessel.

18. The system of claim 17, wherein: The supported CoMo catalyst is supported on alumina; The supported NiMo catalyst is supported on alumina; Or both.

19. The system of claim 17 or 18, wherein the system further comprises a feed selection valve located between the fixed bed reactor and the first feed source and the second feed source, the feed selection valve being configured to operate between: a first feed location that delivers a first feed stream comprising H2S and olefins from the first feed source to the reactor inlet; and A second feed location delivers a second feed stream comprising a first symmetric sulfide and a second symmetric sulfide from the second feed source to the reactor inlet.

20. The system of any one of claims 17 to 19, wherein the system further comprises a product selection valve located between the fixed bed reactor and the first product line and the second product line, the product selection valve being configured to operate between: a first product location that delivers the reaction mixture from the reactor outlet to a mercaptan product stream; and A second product location delivers the reaction mixture from the reactor outlet to an asymmetric sulfide product stream.

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