A methanethiol synthesis catalyst with a wide hydrogen sulfide to methanol ratio and a preparation method thereof

Abstract

The application discloses a methanethiol synthesis catalyst with a wide hydrogen sulfide to methanol ratio and a preparation method thereof. The catalyst comprises the following components in parts of mass: 1-10 parts of magnesium oxide, 60-80 parts of aluminum oxide, 10-25 parts of potassium tungstate and 2-10 parts of vanadium pentoxide. The catalyst can keep high activity, high selectivity and long service life in a wide methanethiol ratio range, and has wide application value.

Description

Technical Field

[0001] This invention relates to catalyst synthesis processes, and more particularly to a catalyst for the synthesis of methanethiol with a wide hydrogen sulfide to methanol ratio and its preparation method. Background Technology

[0002] Methanethiol is an important organic intermediate widely used in the production of pesticides, pharmaceuticals, and synthetic materials. The route for synthesizing methanethiol from methanol and hydrogen sulfide has attracted considerable attention due to its inexpensive feedstock and the potential for resource utilization through combination with hydrogen sulfide-containing industrial waste gas. However, in industrial practice, the molar ratio of hydrogen sulfide to methanol in the feedstock gas (thiol ratio) varies over a wide range (0.1 / 1 to 5 / 1) due to fluctuations in upstream processes. Existing catalysts are often optimized for specific thiol ratios, and deviations from design conditions can easily lead to problems such as decreased methanol conversion, reduced methanethiol selectivity, increased byproducts (such as dimethyl ether, hydrocarbons, and carbon deposits), and accelerated catalyst deactivation. For example, under low thiol ratio conditions, the catalyst is prone to deactivation due to over-reduction and carbon deposition; under high thiol ratio conditions, although carbon deposition can be suppressed, excessive hydrogen sulfide may cause over-sulfidation of the active component, affecting the catalyst structure and stability. Therefore, there is an urgent need in this field to develop a methanethiol synthesis catalyst that can maintain high activity, high selectivity, and long lifetime across a wide range of thiol ratios.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] To address the problems existing in the prior art, the primary objective of this invention is to provide a methanethiol synthesis catalyst with a wide hydrogen sulfide to methanol ratio. This catalyst can maintain high activity, high selectivity, and long lifespan across a wide mercaptan ratio range, and has broad application value.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned methanethiol synthesis catalyst, which has simple operation steps and produces a catalyst with good catalytic activity.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] The present invention provides a methanethiol synthesis catalyst with a wide hydrogen sulfide to methanol ratio, which mainly comprises the following components: by mass parts, 1-10 parts of magnesium oxide, 60-80 parts of aluminum oxide, 10-25 parts of potassium tungstate, and 2-10 parts of vanadium pentoxide.

[0008] Preferably, as a further feasible option, the composition by mass is 3-7 parts magnesium oxide, 65-75 parts aluminum oxide, 12-20 parts potassium tungstate, and 5-8 parts vanadium pentoxide.

[0009] Preferably, as a further feasible option, the composition by mass is 5 parts magnesium oxide, 70 parts aluminum oxide, 18 parts potassium tungstate, and 7 parts vanadium pentoxide.

[0010] Preferably, as a further feasible option, the catalyst has a specific surface area of ​​100-250 m² / g and a pore volume of 0.30-0.65 ml / g.

[0011] The catalyst of this invention mainly consists of two active components, potassium tungstate and vanadium pentoxide, and two catalyst supports, magnesium oxide and aluminum oxide. The support used is a composite support, unlike previous methods that used only a single alumina support. This invention constructs a composite support... In the composite carrier, the alkalinity of MgO effectively neutralizes the Lewis acid centers on the carrier surface from the alumina matrix, significantly inhibiting the side reaction of methanol dehydration to form dimethyl ether and improving the selectivity of methanethiol.

[0012] Regarding active ingredients, With additives There is a synergistic effect; the introduction of species V not only adjusts the electronic band state of the active center W, enhancing its intrinsic activity, but also its variable valence state... It also effectively promotes the oxidation and removal of carbon precursors during the reaction process, greatly enhances the catalyst's resistance to carbon deposition, and broadens its adaptability to low mercaptan ratios.

[0013] In terms of dosage, the mass fraction of potassium tungstate should be controlled between 10 and 25 parts. Too little potassium tungstate will affect the service life of the catalyst, while too much potassium tungstate will clog the micropores of the catalyst, affecting its activity and increasing the production cost of the catalyst. The mass fraction of vanadium pentoxide should be controlled between 2 and 10 parts, because practice has shown that combining it with potassium tungstate within this dosage range can greatly improve the activity. Too much or too little vanadium pentoxide will have a certain impact on the service life of the catalyst itself and will not allow the catalyst to be in its optimal state of activity.

[0014] The mass fraction of magnesium oxide needs to be controlled between 1 and 10 parts. If the amount is too small, it cannot effectively improve (or neutralize and cover) the L acid sites on the surface of alumina, and the modification effect is not obvious. If the amount is too large, it will affect the pore volume and specific surface area of ​​the catalyst. Therefore, the amount of magnesium oxide needs to be controlled within the range required by this invention.

[0015] The present invention also provides a method for preparing the above-mentioned methanethiol synthesis catalyst, which mainly adopts the impregnation method or the mixing and grinding method to prepare the catalyst.

[0016] The catalyst can be prepared by impregnation or grinding, and can be shaped into spheres, five-toothed spheres, four-leaf impellers, strips, clover shapes, or four-leaf clover shapes.

[0017] Preferably, as a further feasible option, the impregnation method includes the following steps:

[0018] Magnesium-aluminum composite carriers were prepared by coprecipitation method. Potassium salt, ammonium metavanadate, ethylenediamine disuccinic acid and ammonia were dissolved in deionized water at a dissolution temperature of 40-95℃ to prepare an active component solution.

[0019] The magnesium-aluminum composite carrier is immersed in the active component solution at an immersion temperature of 40–95°C for 0.5–24 h. The immersed carrier is then removed, dried at 40–200°C to constant weight, and finally calcined at 450–500°C.

[0020] Preferably, as a further feasible option, the mixing and milling method includes the following steps:

[0021] Magnesium-aluminum composite carriers were prepared by coprecipitation method. Potassium salt, ammonium metavanadate, ethylenediamine disuccinic acid and ammonia were dissolved in deionized water at a dissolution temperature of 40-95℃ to prepare an active component solution.

[0022] The magnesium-aluminum composite carrier is mixed with the active component solution, then fully rolled until homogeneous, and calcined to form the final product.

[0023] Preferably, as a further feasible option, the method for preparing the magnesium-aluminum composite support by co-precipitation includes:

[0024] Mix a mixed solution of magnesium nitrate and aluminum nitrate with a sodium carbonate solution, and control the pH value at the final reaction point to be 7.5–8.5;

[0025] The obtained precipitate was dried at 120–150°C, pulverized, shaped, heated and dried again, and then calcined at 450–650°C to obtain a magnesium-aluminum composite carrier.

[0026] Preferably, as a further feasible option, the amount of ethylenediamine disuccinic acid added is 0.5% to 2.5% of the mass of the magnesium-aluminum composite support. Ethylenediamine disuccinic acid (EDDS) is a complexing agent for catalyst preparation. It decomposes during catalyst heat treatment. Ethylenediamine disuccinic acid is a key component in preparing the catalyst active component solution. The active component solution is stable, and the active component is more uniformly impregnated on the catalyst. As an environmentally friendly chelating agent (biodegradable), EDDS has the advantage of "dynamic complexation-directional pore formation" compared with traditional PVP and sodium citrate. The two carboxyl groups and two amino groups in its molecule can interact with the active component. A dynamic chelate is formed, which slowly releases metal ions with temperature changes during impregnation, allowing the active components to form a "monolayer dispersion" on the carrier surface, avoiding pore blockage; simultaneously, EDDS decomposes during calcination to generate... The addition of a small amount of ethylenediamine allows for the construction of hierarchical channels with diameters of 15–25 nm within the support, increasing the proportion of macropores >15 nm by 30% and significantly accelerating reactant / product diffusion. Furthermore, the biodegradability of EDDS avoids residual pollution from traditional complexing agents, thus meeting the demands of green chemistry.

[0027] The method requires the addition of ammonia water because ammonia water can promote the dissolution of the complexing agent EDDS, thereby enabling EDDS to be stably dissolved in ammonia water.

[0028] In summary, the catalyst of this invention has an optimized pore structure (high proportion of macropores >15 nm), which facilitates the diffusion of reactants and products, reduces deep reactions and carbon deposition, thereby further extending the catalyst lifetime. This catalyst maintains high activity and selectivity across an extremely wide thiol ratio range of 0.1 / 1 to 5 / 1, exhibits strong adaptability to fluctuations in feed gas, and shows promising prospects for industrial applications.

[0029] To further optimize reaction performance, especially in large industrial reactors, the catalyst can be layered. For example, a catalyst with better anti-carbon deposition properties prepared by a grinding method can be loaded upstream of the reactor, while a highly active catalyst prepared by an impregnation method with active components enriched on the surface can be loaded downstream. This adapts to the concentration and temperature distribution along the reactor axis, achieving high efficiency and stability throughout the entire process. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] To more clearly illustrate the technical solutions in this invention, specific embodiments are described below.

[0033] Example 1

[0034] Preparation of methanethiol synthesis catalyst by impregnation method:

[0035] 1) Carrier preparation: A mixed solution of magnesium nitrate and aluminum nitrate was prepared and added to the reactor in parallel with a sodium carbonate solution. The pH was controlled at 8.0, and the mixture was aged for 2 hours. The precipitate was filtered, washed, dried at 120℃ for 12 hours, pulverized, and extruded into clover-shaped strips. The strips were then calcined at a programmed temperature of 550℃ for 4 hours to obtain the magnesium-aluminum composite carrier. The specific surface area of ​​the carrier was measured to be 235 m² / g, and the pore volume was 0.50 ml / g, of which the pore volume >15 nm was 0.13 ml / g.

[0036] 2) Preparation of impregnation solution: Weigh out a certain amount of the catalyst... and (by The active component solution was prepared by dissolving ethylenediamine disuccinic acid and ammonia in deionized water and stirring at 60°C until completely dissolved. The amount of ethylenediamine disuccinic acid added was 1.5% of the mass of the magnesium-aluminum composite carrier.

[0037] 3) Impregnation and calcination: The carrier obtained in step 1 was impregnated in the above-mentioned active component solution at a constant temperature of 60°C for 12 hours. After removal, it was dried at 110°C for 12 hours and then calcined at 480°C for 4 hours to obtain the catalyst. The composition of the catalyst was determined to be: by mass percentage, 5% magnesium oxide, 70% aluminum oxide, 18% potassium tungstate, and 7% vanadium pentoxide.

[0038] Example 2

[0039] Preparation of methanethiol synthesis catalyst by impregnation method:

[0040] 1) Carrier preparation: A mixed solution of magnesium nitrate and aluminum nitrate was prepared and added to the reactor in parallel with a sodium carbonate solution. The pH was controlled at 8.5, and the mixture was aged for 2 hours. The precipitate was filtered, washed, dried at 140℃ for 12 hours, pulverized, and extruded into clover-shaped strips. The strips were then calcined at a programmed temperature of 450℃ for 4 hours to obtain the magnesium-aluminum composite carrier. The specific surface area of ​​the carrier was measured to be 220 m² / g, and the pore volume was 0.35 ml / g, of which the pore volume >15 nm was 0.13 ml / g.

[0041] 2) Preparation of impregnation solution: Weigh out a certain amount of the catalyst... and (by The active component solution was prepared by dissolving ethylenediamine disuccinic acid and ammonia in deionized water and stirring at 40°C until completely dissolved. The amount of ethylenediamine disuccinic acid added was 2.5% of the mass of the magnesium-aluminum composite carrier.

[0042] 3) Impregnation and calcination: The carrier obtained in step 1 was impregnated in the above active component solution at a constant temperature of 95°C for 1 hour. After removal, it was dried at 40°C for 12 hours and then calcined at 500°C for 4 hours to obtain the catalyst. The composition of the catalyst was determined to be: by mass percentage, 1% magnesium oxide, 80% aluminum oxide, 10% potassium tungstate, and 9% vanadium pentoxide.

[0043] Example 3

[0044] Preparation of methanethiol synthesis catalyst by impregnation method:

[0045] 1) Carrier preparation: A mixed solution of magnesium nitrate and aluminum nitrate was prepared and added to the reactor in parallel with a sodium carbonate solution. The pH was controlled at 7.5, and the mixture was aged for 2 hours. The precipitate was filtered, washed, dried at 150℃ for 12 hours, pulverized, and extruded into clover-shaped strips. The mixture was then calcined at 650℃ for 4 hours to obtain the magnesium-aluminum composite carrier. The specific surface area of ​​the carrier was measured to be 210 m² / g, and the pore volume was 0.30 ml / g, of which the pore volume >15 nm was 0.13 ml / g.

[0046] 2) Preparation of impregnation solution: Weigh out a certain amount of the catalyst... and (by The active component solution is prepared by dissolving ethylenediamine disuccinic acid and ammonia in deionized water and stirring at 95°C until completely dissolved. The amount of ethylenediamine disuccinic acid added is 1% of the mass of the magnesium-aluminum composite carrier.

[0047] 3) Impregnation and calcination: The carrier obtained in step 1 was impregnated in the above-mentioned active component solution at a constant temperature of 40°C for 24 hours. After removal, it was dried at 200°C for 12 hours and then calcined at 450°C for 4 hours to obtain the catalyst. The composition of the catalyst was determined to be: by mass percentage, 10% magnesium oxide, 60% aluminum oxide, 25% potassium tungstate, and 5% vanadium pentoxide.

[0048] Example 4

[0049] Preparation of methanethiol synthesis catalyst by grinding and mixing:

[0050] 1) Carrier preparation: A mixed solution of magnesium nitrate and aluminum nitrate was prepared and added to the reactor in parallel with a sodium carbonate solution. The pH was controlled at 8.0, and the mixture was aged for 2 hours. The precipitate was filtered, washed, dried at 120℃ for 12 hours, pulverized, and extruded into clover-shaped strips. The strips were then calcined at a programmed temperature of 550℃ for 4 hours to obtain the magnesium-aluminum composite carrier. The specific surface area of ​​the carrier was measured to be 235 m² / g, and the pore volume was 0.50 ml / g, of which the pore volume >15 nm was 0.13 ml / g.

[0051] 2) Mixing and compacting: Mixing the carrier powder with powder containing... The mixture, along with a solution of ethylenediamine disuccinic acid and ammonia, is ground until homogeneous in a mixer. After initial drying at 100°C, a small amount of solution is added again for secondary grinding. The amount of ethylenediamine disuccinic acid added is 2.5% of the mass of the magnesium-aluminum composite carrier.

[0052] 3) Molding and calcination: The uniformly crushed material is extruded into strips, dried at 100℃, and then calcined at 470℃ for 4 hours to obtain the catalyst. The composition of the catalyst is as follows (by mass percentage): 3% magnesium oxide, 75% aluminum oxide, 17% potassium tungstate, and 5% vanadium pentoxide.

[0053] Example 5

[0054] Preparation of methanethiol synthesis catalyst by grinding and mixing:

[0055] 1) Carrier preparation: A mixed solution of magnesium nitrate and aluminum nitrate was prepared and added to the reactor in parallel with a sodium carbonate solution. The pH was controlled at 8.5, and the mixture was aged for 2 hours. The precipitate was filtered, washed, dried at 140℃ for 12 hours, pulverized, and extruded into clover-shaped strips. The strips were then calcined at 600℃ for 4 hours to obtain the magnesium-aluminum composite carrier. The specific surface area of ​​the carrier was measured to be 235 m² / g, and the pore volume was 0.50 ml / g, of which the pore volume >15 nm was 0.13 ml / g.

[0056] 2) Mixing and compacting: Mixing the carrier powder with powder containing... The mixture, along with a solution containing ethylenediamine disuccinic acid and ammonia, is ground in a mixer until homogeneous. After initial drying at 100°C, a small amount of solution is added again for secondary grinding. The amount of ethylenediamine disuccinic acid added is 0.5% of the mass of the magnesium-aluminum composite carrier.

[0057] 3) Molding and calcination: The uniformly crushed material is extruded into strips, dried at 100℃, and then calcined at 480℃ for 3 hours to obtain the catalyst. The composition of the catalyst is as follows (by mass percentage): 7% magnesium oxide, 65% aluminum oxide, 12% potassium tungstate, and 6% vanadium pentoxide.

[0058] Comparative Example 1

[0059] The specific operating steps are the same as in Example 1, except that the catalyst does not contain vanadium pentoxide.

[0060] Comparative Example 2

[0061] The specific operating steps are the same as in Example 1, except that the catalyst does not contain magnesium oxide.

[0062] Example 6

[0063] The specific operating steps are the same as in Example 1, except that the catalyst composition is: 3% magnesium oxide, 74% aluminum oxide, 18% potassium tungstate, and 5% vanadium pentoxide.

[0064] Application and Performance Evaluation: The catalysts from the above-mentioned examples and comparative examples were crushed and sieved to 20-40 mesh, and 10 mL was charged into a fixed-bed reactor. The reaction conditions were: temperature 360℃, pressure 0.5 MPa, and the molar ratio (thiol ratio) of hydrogen sulfide to methanol in the feed gas was set to 0.8 / 1 (low), 1.5 / 1 (conventional), and 5.0 / 1 (high) for evaluation. The reaction results are shown in Table 1 below (data after reaction stabilization):

[0065] Table 1 Experimental Results

[0066] Catalyst Thiol ratio Methanol conversion (%) Methyl mercaptan selectivity (%) Example 1 0.8 / 1 76.3 86.9 Example 1 1.5 / 1 92.6 94.5 Example 1 5.0 / 1 94.9 95.4 Example 2 0.8 / 1 73.4 82.5 Example 3 0.8 / 1 75.5 90.7 Example 4 0.8 / 1 73.1 83.6 Example 5 0.8 / 1 74.5 87.6 Example 6 1.5 / 1 90.4 93.8 Comparative Example 1 0.8 / 1 70.1 73.5 Comparative Example 2 0.8 / 1 72.3 70.9

[0067] The experimental data above show that when the components are selected and proportioned according to the scheme of the present invention, it can achieve better methanol conversion rate and methanethiol selectivity, and can maintain high activity and high selectivity over a very wide range of thiol ratios.

[0068] Finally, it is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the principles and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A catalyst for the synthesis of methanethiol with a wide hydrogen sulfide to methanol ratio, characterized in that, It mainly includes the following components: by mass parts, 1-10 parts of magnesium oxide, 60-80 parts of aluminum oxide, 10-25 parts of potassium tungstate and 2-10 parts of vanadium pentoxide.

2. The methanethiol synthesis catalyst according to claim 1, characterized in that, By mass fraction, it contains 3-7 parts magnesium oxide, 65-75 parts aluminum oxide, 12-20 parts potassium tungstate, and 5-8 parts vanadium pentoxide.

3. The methanethiol synthesis catalyst according to claim 1, characterized in that, By mass fraction, there are 5 parts magnesium oxide, 70 parts aluminum oxide, 18 parts potassium tungstate, and 7 parts vanadium pentoxide.

4. The methanethiol synthesis catalyst according to claim 1, characterized in that, The catalyst has a specific surface area of ​​100-250 m² / g and a pore volume of 0.30-0.65 ml / g.

5. The methanethiol synthesis catalyst according to claim 1, characterized in that, The catalyst is spherical, five-toothed spherical, four-leaf impeller, strip-shaped, clover-shaped, or four-leaf clover-shaped.

6. The method for preparing the methanethiol synthesis catalyst according to any one of claims 1-5, characterized in that, The process includes the following steps: preparing the catalyst using an impregnation method or a grinding method.

7. The method for preparing the methanethiol synthesis catalyst according to claim 6, characterized in that, The impregnation method includes the following steps: Magnesium-aluminum composite carriers were prepared by coprecipitation method. Potassium salt, ammonium metavanadate, ethylenediamine disuccinic acid and ammonia were dissolved in deionized water at a dissolution temperature of 40-95℃ to prepare an active component solution. The magnesium-aluminum composite carrier is immersed in the active component solution at an immersion temperature of 40–95°C for 0.5–24 h. The immersed carrier is then removed, dried at 40–200°C to constant weight, and finally calcined at 450–500°C.

8. The method for preparing the methanethiol synthesis catalyst according to claim 7, characterized in that, The mixing and milling method includes the following steps: Magnesium-aluminum composite carriers were prepared by coprecipitation method. Potassium salt, ammonium metavanadate, ethylenediamine disuccinic acid and ammonia were dissolved in deionized water at a dissolution temperature of 40-95℃ to prepare an active component solution. The magnesium-aluminum composite carrier is mixed with the active component solution, then fully rolled until homogeneous, and calcined to form the final product.

9. The method for preparing the methanethiol synthesis catalyst according to claim 8, characterized in that, The method for preparing magnesium-aluminum composite carriers by co-precipitation includes: Mix a mixed solution of magnesium nitrate and aluminum nitrate with a sodium carbonate solution, and control the pH value at the final reaction point to be 7.5–8.5; The obtained precipitate was dried at 120–150°C, pulverized, shaped, heated and dried again, and then calcined at 450–650°C to obtain a magnesium-aluminum composite carrier.

10. The method for preparing the methanethiol synthesis catalyst according to any one of claims 6-9, characterized in that, The amount of ethylenediamine disuccinic acid added is 0.5% to 2.5% of the mass of the magnesium-aluminum composite carrier.