JPS6312866B2 - - Google Patents

Description

[Detailed description of the invention]

Methyl mercaptan is a well-known product that is being used as an intermediate for the production of various pesticides and as a raw material for the production of methionine, a feed supplement widely used for poultry. The existing preferred industrial method for producing methyl mercaptan is by reaction of methanol and hydrogen sulfide. Thoria, zirconia, activated alumina, silica promoted with tungstates or molybdates (U.S. Pat. No. 2,820,062) or with heteropolyacids or their salts (U.S. Pat. No. 3,035,097)
A variety of catalysts can be used, such as alumina and alumina. These processes are highly efficient when carried out industrially and provide methyl mercaptan in high yield and purity. Nevertheless, further economics can be obtained by substituting methanol with the basic raw materials carbon monoxide or carbon dioxide. Methyl mercaptan can be prepared from carbon oxides according to the following formula: (1) CO+H ₂ S+2H ₂ →CH ₃ SH+H ₂ O (2) CO ₂ +H ₂ S+3H ₂ →CH ₃ SH+2H ₂ O U.S. Pat. A conventional method related to equations (1) and (2) is disclosed. The prior art methods described above have a number of drawbacks from an industrial point of view. First, the yield is somewhat low.
The best yield for methyl mercaptan is 23.2% in Example 2 of the above patent. The two-phase catalyst system is a complex system consisting of a large amount of powdered sulfur-active hydrogenation catalyst suspended in a large volume of liquid organic amine relative to the amount of reactants used. In addition, the preferred reaction conditions disclosed in the above patent are:
It is inherently expensive from an industrial point of view. This is because they involve operating at high pressures in the range of 1200-2000 psig for long reaction times of 3-6 hours. In addition, the amine cocatalysts of prior art processes result in hydrosulfide salts in the reaction conditions, and these salts are unstable at standard pressure conditions, thereby allowing highly toxic hydrogen sulfide gas to be eliminated. .
The yield in the above patent is particularly low when carbon dioxide is used as the raw material, as shown in formula (2) above. Furthermore, in Example 1 of the above patent, carbon monoxide is 17.7
% yield. Conversions of less than 5% are obtained with carbon dioxide. The improved process of the present invention overcomes these drawbacks and provides a practical and economical method for producing methyl mercaptan from carbon oxides. The process of the present invention combines reactions (1) and
(2) includes a single phase solid catalyst composition that is highly active in promoting. Additionally, the process of the present invention provides a continuous process requiring relatively short reaction times under mild conditions of temperature and pressure, thereby making the process of the present invention have practical applications. The process of the present invention involves feeding carbon oxide, hydrogen sulfide or elemental sulfur and hydrogen reactants into a reactor and subjecting the reactants to reaction conditions including elevated temperatures and pressures in the presence of a hydrogenation catalyst. improved conversion in a short reaction time at low temperature and pressure conditions without substantial formation of undesirable by-products in a continuous gas phase process for the production of methyl mercaptan, which involves the production of methyl mercaptan by (A) (1) selected from the group consisting of iron, nickel, zinc, chromium, cobalt and molybdenum;
to the oxides, sulfides, hydroxides or salts of more than one metal ()(a) aliphatic, cycloaliphatic or saturated with more than 6 carbon atoms in the aliphatic, cycloaliphatic or aromatic group; organic amine bases selected from heterocyclic and aromatic amines;
or (b) forming a mixture by mixing an alkali metal inorganic base selected from the group of alkali metal bases consisting of oxides, hydroxides, sulfides or salts of alkali metals, and then (B) forming a mixture of (A) ) is at least partially sulfided by heating the mixture in the presence of hydrogen sulfide or elemental sulfur, provided that steps (A)( ) and
A method for producing methyl mercaptan characterized by using a single-phase solid catalyst prepared by a method in which step (B) is optional when a metal sulfide is used in both (A)() and (b). Defined as continuous gas phase method. The metal oxide, sulfide, hydroxide or salt in step (A)() is preferably on a support, and the most preferred support is activated alumina. The preferred metal is nickel, and nickel oxide is preferred as the presulfided form. The method works well with either carbon monoxide or carbon dioxide, but carbon monoxide is preferred. A preferred amine in step (A)()(a) is tridodecylamine. In step (A)()(b), the inorganic base may be an oxide, hydroxide, sulfide or salt of potassium, rubidium or cesium, most preferably cesium. The carbon oxide, hydrogen sulfide and hydrogen reactants are each preferably fed to the reactor in molar ratios within the range of about 1/3/2 to about 1/8/8. The hydrogen sulfide reactant can be prepared in situ within the reactor by feeding elemental sulfur into the reactor, in which case the carbon oxides, elemental sulfur and hydrogen charged to the reactor are The respective molar ratios of are within the range of about 1/3/3 to about 1/8/10. The preferred temperature within the reactor is within the range of about 250 to about 350 °C, whereas the preferred pressure is about 600 °C.
In the range of ~1000 psig. About 5 to about 200 volumes of carbon oxide/catalyst capacity/hr
It is preferred to operate the method under conditions that provide a space velocity within the range of . Each reactant is charged at approximately 180% prior to feeding to the reactor.
Preferably, the preheating temperature is within the range of ~300°C. Further, the catalyst can also be defined as the composition after the sulfurization step (B). The catalyst composition also includes (a) iron, nickel, zinc, chromium, a single-phase solid catalyst composition comprising a metal sulfide or a mixture of metal sulfides selected from the group of sulfides consisting of cobalt and molybdenum sulfides in admixture with (b) an alkali metal sulfide and/or a hydrogenated sulfide; Defined as a thing. The catalyst of the invention consists of a conventional hydrogenation catalyst treated with an organic or inorganic base and sulfided with hydrogen sulfide at elevated temperatures. The organic base can be any high molecular weight amine with a boiling point high enough that it does not volatilize from the catalyst surface at an appreciable rate under process conditions. The amine may be primary, secondary or tertiary and may be an aliphatic, cycloaliphatic, aromatic or saturated heterocyclic amine. A preferred example is tridodecylamine. The inorganic base may be any alkali metal oxide, sulfide, hydroxide or salt, and is preferably an oxide, sulfide, hydroxide or salt of potassium, rubidium or cesium. It is understood that upon treatment with _H2S , these bases are at least partially converted to hydrosulfides and/or sulfides. The customary hydrogenation catalysts used are oxides, sulfides, hydroxides or salts of iron, nickel, zinc, chromium, cobalt or molybdenum, alone or in combination, or of alumina, silica, diatomaceous earth, carbon,
It can be supported on a suitable carrier such as clay or refractory material. The preferred hydrogenation metal is nickel. The hydriding metal is at least partially converted to sulfide upon treatment with _H2S . A preferred support is activated alumina. The proportion of hydrogenation catalyst used in admixture with an alkali metal promoter as described herein is preferably within the range of about 70-95%, based on the weight of the mixture, as opposed to an alkali metal promoter. The proportion of the agent is approx.
It is within the range of 30 to about 5%. The mixture is preferably supported on an alumina support, where the alumina accounts for about 10 to about 90% of the total weight of the catalyst system, hydrogenation catalyst, alkali metal promoter, and support. The most preferred catalyst composition contains about 5% by weight cesium sulfide and 13% by weight nickel sulfide supported on activated alumina. In a typical preparation, 950 g of a commercially available pellet hydrogenation catalyst (“Harshaw Ni-0301 T”) containing 11% nickel oxide supported on activated alumina was predried at 150°C and 250 c.c. of water with a solution containing 50 g of cesium hydroxide. The solution is added gradually with good mixing and the wet catalyst is dried in an oven at 150° C. overnight. By charging the dry catalyst into a process reactor and passing hydrogen sulfide gas at about 370° C. and atmospheric pressure for several hours (e.g., 6 to 8 hours) until there is no longer any water of reaction in the effluent gas stream. Sulfurize. The catalyst is now ready for use in the process. The process preferably involves preheating and premixing the reactant gases carbon monoxide or carbon dioxide, hydrogen sulfide, and hydrogen, and feeding the mixture over the catalyst bed under conditions suitable for the reaction to occur. Possibly operated in a continuous manner. The proportions of reactants to be used are based on the stoichiometry of equations (1) and (2).
Preferably, the carbon oxide is reacted with a molar excess of hydrogen sulfide and a molar excess of hydrogen. Most preferably between 1/3/2 and 1/8/8 CO _1-2 /
A _H2S / _H2 molar ratio is used. Gas is about 180 ~
It is preheated to 300°C, mixed and passed through a catalyst bed to effect the reaction. A wide range of reaction conditions can be used to achieve conversion to methyl mercaptan. Generally, the production of methyl mercaptan is approximately 600 to
Advantageously, high pressures up to 1000 psig, catalyst bed temperatures in the range of 250-350°C and space velocities in the range of about 5-200 carbon oxides/catalyst/hr are used. The production of methyl mercaptan is also promoted by long catalyst contact times, i.e. low space velocities; however, in industrial processes where high production rates are desired, this process can be carried out using 60 to 200 carbon oxides/catalyst. It is possible to operate at high space velocities in the range of /hr, in which case the conversion of carbon oxides to methyl mercaptan per pass is relatively high.
Unconverted reactants can be separated by distillation from the product and recycled in industrial operations for maximum economy in feedstock. Since carbon monoxide is more reactive than carbon dioxide in this process, it is the preferred feedstock to operate at high conversions and high space velocities. Elemental sulfur can be used in place of hydrogen sulfide in this method. This is because the hydrogen present in the feed mixture converts the sulfur to hydrogen sulfide in situ at the process conditions. When elemental sulfur is used instead of hydrogen sulfide, correspondingly higher proportions of hydrogen can of course be used, and the preferred molar ratio of CO _1-2 /S/H ₂ is from about 1/3/3 to about It is within the range of 1/8/10. The equation for the reaction with elemental sulfur is: (3) CO+S+3H ₂ →CH ₃ SH+H ₂ O (4) CO ₂ +S+4H ₂ →CH ₃ SH+2H ₂ O Carbon monoxide-hydrogen mixtures are inexpensively prepared from methane and steam by the well-known “syngas” process. be able to. (5) CH ₄ +H ₂ O→CO + 3H ₂ By adding hydrogen sulfide or elemental sulfur to the “synthesis gas”, a low cost reactant mixture suitable for producing methyl mercaptan by this method is obtained. can get. The following example illustrates an improved process for making methyl mercaptan. Example 1 A commercially available 11% nickel oxide supported alumina catalyst (Harshyo Ni-
A series of organic amines and inorganic alkali metal and alkaline earth metal hydroxides and basic promoters were evaluated at 5% by weight for T). The reactant is
It was carbon monoxide, hydrogen sulfide and hydrogen. The initial nickel oxide-alumina catalyst had a surface area of 64 m ² /g, a pore volume of 0.32 cc/g and an average bulk density of 70 lb/ft ³ and was tabletted into 1/8 inch tablets. The reactants were mixed and immediately sent downward through a vertically oriented reactor.
In this case, no preheating was performed. Conversion to methyl mercaptan was relatively low due to the lack of preheating and the use of low pressure (175 psig), but this data was useful for comparing the efficiency of various basic promoters. The main by-product at low pressure was carbon dioxide. The pressure was controlled by an automatic backpressure regulator, and the crude product stream was sent as vapor via a thermal line to a gas sampling unit of a gas chromatograph at atmospheric pressure for analysis. Single flow conversion and yield of carbon monoxide to methyl mercaptan (MM) were calculated from gas chromatographic analysis. The yield takes into account only the unreacted carbon monoxide remaining in the crude product after a single flow through the reactor, and the carbon dioxide that can actually be recycled to produce additional MM with a high final yield. Does not contain by-products such as carbon, carbonyl sulfide and carbon disulfide. The reaction conditions, conversion to MM and yield are shown in Table 1 below. All experiments are at least 15 hours in duration. All catalysts are presulfided by passing hydrogen sulfide gas over them for about 6 hours at about 370° C. and atmospheric pressure.

[Table] (2) Conversion rate and yield decreased with time.
(3) KPT: Potassium phosphotungstate Example 2 Following the results of Example 1 and using the same procedure and general reaction conditions (175 psig), for alumina catalyst supported on 11% nickel oxide (Harshyo Ni-0301 T). Various levels of cesium hydroxide promoter were studied. All catalysts were presulfided. Also,
All experiments were conducted at a space velocity of 5 CO/catalyst/hr, a CO/H ₂ S/H ₂ molar feed ratio of 1/8/4, and a pressure of 175 psig. The results are shown in Table 2 below and show that the 5% cerium hydroxide supported NiO/Al ₂ O ₃ catalyst gave the highest conversion to MM. Conversions and yields in this and subsequent examples were calculated in the same manner as in Example 1.

Table: Example 3 Using the same operating and reaction conditions (175 psig) as in Example 2, various 5% alkali metal hydroxide promoted metal oxide hydrogenation catalysts were evaluated. All catalysts were presulfided. Submit the results in the third section below.
Shown in the table.

EXAMPLE 4 High conversions and yields of carbon monoxide to methyl mercaptan were obtained by preparing the reactants and conducting the reaction at high pressures above 400 psig. At this higher pressure, more CO was converted to MM at the expense of by-product _CO2 . CO ₂ is believed to result from the reaction of starting material CO with reaction by-product H ₂ O according to the well-known reaction CO+H ₂ O→CO ₂ +H ₂ . CO ₂ becomes H ₂ S at low pressure
and H ₂ (according to equation (2)), but slowly and rapidly at higher pressures. However, Hershiyo Ni−0301 T
prepared from NiO/Al ₂ O ₃ and freshly prepared before use.
5% KOH supported NiO/Al ₂ O ₃ and 5 presulfided with hydrogen sulfide for about 6 hours at 370 °C and atmospheric pressure
Pressures above about 700 psig are not required to obtain high MM conversions as shown by the results in Table 4 below using the %CsOH supported NiO/Al ₂ O ₃ catalyst.

【table】

Table Example 5 As the CO space velocity increases, the conversion to MM decreases and the amount of by-product CO ₂ increases.
The use of less than a molar excess of H ₂ S and H ₂ with respect to CO in the feed mixture and a slightly higher catalyst temperature was found to be advantageous in obtaining high conversions at high space velocities. . The data in Table 5 show that fairly high conversions of CO to MM can be obtained at industrially practical space velocities in the range of 60 to 180 CO/catalyst/hr. The main by-product at high space velocities is CO ₂ , which can be recycled to produce additional MM (as shown in Example 6 below) or to produce high final MM. It can be reconverted to CO by the well known reaction CO ₂ + CH ₄ →2CO + 2H ₂ or by other means with methane to provide a yield. The catalyst used in these experiments was 5 wt% CsOH impregnated with a commercially available 11% NiO/Al ₂ O ₃ (Harshayo Ni-0301 T) catalyst and presulfided with hydrogen sulfide as previously described. It is.

【table】

[Table] Example 6 Carbon dioxide, hydrogen sulfide and hydrogen flows separately
Preheat to 150-190 ° _C , mix and 5 wt% cesium hydroxide promoted NiO/ _Al2O3 catalyst (Harshyo
Ni−0301 T) in a horizontal reactor containing 260 to 295
It was passed continuously at ℃. The pressure within the reactor was maintained at 700 psig by a back pressure regulating valve. The _CO2 / _H2S / _H2 molar ratio in the feed mixture was 1/8/4. The crude product mixture was sent via thermal 316 stainless steel tubing at atmospheric pressure to the hot gas sampler of a gas chromatograph for analysis. _CO2 to MM
The conversion and yield of were calculated from gas chromatographic analysis. According to the results summarized in Table 6 below, CO ₂
is similarly converted to MM, but it is shown to react somewhat slower than carbon monoxide at the same reaction conditions and results in lower conversion to MM per pass.

[Table] It seems that it will be further converted.
Example 7 In another embodiment of the present invention, an alkali metal promoted zinc chromite supported alumina catalyst provides certain advantages over the above-described catalysts of the present invention. A specific example of this will be illustrated below. Zinc chromite supported alumina catalyst (Harsho)
ZN-0601) was impregnated with cesium hydroxide so that the final catalyst contained 10% by weight of cesium hydroxide and sulfided by passing hydrogen sulfide over the catalyst as described above. A catalyst was thus prepared. “Harshaw ZN−
0601'' catalyst consists of 38% zinc oxide and 25% chromium oxide supported on activated alumina. It has an average bulk density of 97 lb/ft ³ , a surface area of 56 m ² /g and a fines of 0.18 cc/g. The zinc-containing catalyst thus prepared was used below for the production of methyl mercaptan. The molten sulfur was vaporized in a preheater and mixed with carbon monoxide and hydrogen to form carbon monoxide,
A gaseous feed mixture containing sulfur and hydrogen in a molar ratio of 1/6/4 was prepared. This mixture was passed continuously over the above zinc catalyst at a space velocity of 80. The reactor pressure was maintained at 250 psig and the catalyst bed temperature was maintained at 665°C (395.6°C). Gas chromatographic analysis of the product stream exiting the reactor showed a high hydrogen sulfide content and 27.6% conversion of carbon monoxide to methyl mercaptan.
All of the sulfur was consumed in one pass through the reactor. Recycling the hydrogen sulfide formed in the first pass through the catalyst produced additional methyl mercaptan. Examples 1 to 7 above show that the process of the invention can be used in continuous mode at industrially applicable reaction conditions to produce methyl mercaptan from carbon monoxide and carbon dioxide with high conversions and yields. When using the preferred carbon monoxide as starting material, gas chromatographic analysis of the crude product stream shows that carbon dioxide is the main by-product and small amounts of carbonyl and dimethyl sulfides and traces of methane are also detected. . Methane production is minimized by maintaining the reaction temperature below about 300°C. The remaining by-products are easily separated by distillation. At no time was methanol detected to be present in the crude product stream, indicating that methanol is not an intermediate in the process. Thus, carbon monoxide
The reaction sequence for converting to MM is as follows. (6) CO+H ₂ S→COS+H ₂ (7) COS+3H ₂ →CH ₃ SH+H ₂ O Reactions (6) and (7) proceed easily with the preferred catalyst and conditions of this method, whereas CO and H ₂ does not react to produce methanol under these conditions.

Claims (1)

[Claims] 1. From feeding reactants of carbon oxide, hydrogen sulfide or elemental sulfur and hydrogen into a reactor and subjecting the reactants to elevated temperatures and pressures in the presence of a hydrogenation catalyst. In the method for producing methyl mercaptan, a metal sulfide or a metal sulfide mixture selected from the sulfide group consisting of iron, nickel, zinc, chromium, cobalt and molybdenum sulfides is combined with an alkali metal sulfide and/or water. A method for producing methyl mercaptan, characterized in that a single-phase solid catalyst composition containing a carrier supported in a mixed state with a sulfide is used as a hydrogenation catalyst. 2. The method of claim 1, wherein the temperature is in the range of 250-350°C and the pressure is in the range of 600-1000 psig. 3. The method according to claim 1, wherein the support is activated alumina. 4. The method according to claim 2, wherein the carrier is an activated alumina carrier. 5. The method according to claim 4, wherein the metal sulfide is nickel sulfide and the alkali metal sulfide is cesium sulfide or potassium sulfide. 6. The method of claim 4, wherein the reactants carbon oxide, hydrogen sulfide and hydrogen are each fed to the reactor in a molar ratio within the range of 1/3/2 to 1/8/8. 7. Claim 4, wherein the reactants carbon oxide, elemental sulfur and hydrogen are each fed to the reactor in a molar ratio within the range of 1/3/3 to 1/8/10.
The method described in section. 8. The metal sulfide is nickel sulfide, the alkali metal sulfide is cesium sulfide, and the space velocity is within the range of 5 to 200 volumes of carbon oxide/catalyst capacity/hr. the method of. 9. The metal sulfide is nickel sulfide, the alkali metal sulfide is cesium sulfide, and the space velocity is within the range of 5 to 200 volumes of carbon oxide/catalyst capacity/hr. the method of.