A CuKMoS2 / SiO2 catalyst for the synergistic preparation of methyl mercaptan from carbon dioxide and hydrogen sulfide

Abstract

The present invention relates to a CuKMoS2 / SiO2 catalyst for the synergistic production of methyl mercaptan from carbon dioxide and hydrogen sulfide. By introducing a small amount of copper (Cu) into the KMoS2 / SiO2 catalyst system, the catalyst's selectivity for the reaction intermediate methanol (CH3OH) is significantly improved, thereby enhancing the selectivity for the target product methyl mercaptan (CH3SH). The introduction of Cu promotes electron transfer at active sites on the MoS2 catalyst surface, optimizing the reaction pathway. This invention provides a method for preparing a highly efficient, selective, and stable catalyst and a new process for methyl mercaptan production.

Description

Technical Field

[0001] The present invention relates to a preparation technology of an environmental catalyst and its application field, and particularly to a preparation method of a CuKMo / SiO2 catalyst for synergistically preparing methyl mercaptan from carbon dioxide and hydrogen sulfide and its application. Background Art

[0002] Carbon dioxide (CO2) and hydrogen sulfide (H2S) are common byproducts of industrial processes. CO2 is a greenhouse gas, and excessive emissions contribute to global warming. H2S is highly corrosive and toxic, requiring rigorous treatment before release. Therefore, the effective utilization of CO2 and H2S is a key research topic in environmental protection and resource utilization.

[0003] Methyl mercaptan (CH3SH) is an important chemical raw material widely used in organic synthesis, pesticides, pharmaceuticals, and rubber. Traditionally, the industrial production of methyl mercaptan relies on the reaction of methanol with hydrogen sulfide (H2S) over an acidic catalyst. However, with increasing environmental protection requirements and the need for sustainable resource utilization, research has focused in recent years on developing green catalytic systems for the production of methyl mercaptan using carbon monoxide (CO) and hydrogen sulfide as raw materials. The ability to convert carbon dioxide (CO2) and H2S into high-value-added chemicals would not only reduce greenhouse gas emissions but also fully utilize sulfur-containing waste gas resources, which has significant environmental and economic significance.

[0004] In previous research on the synergistic catalytic reaction of CO and H₂S, molybdenum sulfide (MoS₂) and its derivatives, due to their unique layered structure and good sulfur affinity, have become one of the main catalyst materials for this reaction. However, single MoS₂ catalysts suffer from low activity and poor selectivity in actual reactions, especially in controlling the formation of intermediates such as methanol (CH₃OH). Furthermore, the long-term stability of MoS₂ catalysts presents certain challenges. Therefore, optimizing the composition and structure of MoS₂ catalysts to improve their activity and selectivity has become a research focus in this field.

[0005] The present invention develops a CuKMoS2 / SiO2 catalyst for the synergistic preparation of methyl mercaptan from carbon dioxide and hydrogen sulfide. By optimizing the incorporation ratio of Cu and K and the sulfidation process, the catalyst's selectivity for the methanol intermediate is significantly improved, thereby increasing the selectivity for the formation of methyl mercaptan and effectively inhibiting the formation of by-products, providing a new and efficient catalytic material for the green synthesis of methyl mercaptan. Summary of the Invention

[0006] The present invention addresses the shortcomings of existing technologies by providing a method and application for preparing CuKMoS2 / SiO2 for the synergistic production of methyl mercaptan from carbon dioxide and hydrogen sulfide. Adding a small amount of Cu to the KMoS2 / SiO2 catalyst effectively adsorbs and dissociates the reactants H2 and H2S, inducing a reaction to produce methanol, a key intermediate, thereby significantly improving selectivity for methyl mercaptan.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A method for preparing a CuKMoS2 / SiO2 catalyst comprises the following steps:

[0009] (1) Mix Cu(NO3)2·3H2O and K2MoO4 and add a small amount of water to initially moisten them;

[0010] (2) grinding the mixture obtained in step (1) under a warming lamp, and gradually adding citric acid aqueous solution during the grinding process;

[0011] (3) adding a SiO2 carrier to the solution obtained in step (2), stirring at 80°C to allow the metal ions to be evenly impregnated onto the carrier;

[0012] (4) Drying the impregnated sample and calcining it under N2 atmosphere to promote the decomposition and fixation of the precursor;

[0013] (5) Sulfurization in H2S atmosphere to form MoS2 structure, and introduce sulfur element into the catalyst to finally form CuKMoS2 / SiO2 catalyst.

[0014] Preferably, the molar ratio of Mo to Cu in step (1) is 1:0.01 to 1:0.5, preferably 1:0.05.

[0015] Preferably, the grinding time in step (2) does not exceed 20 minutes, preferably 15 minutes.

[0016] Preferably, the concentration of the citric acid aqueous solution in step (2) does not exceed 25 wt%.

[0017] Preferably, the amount of citric acid added in step (2) is 1.74 mmol.

[0018] Preferably, the loading amount of Mo on the carrier in step (3) (calculated as MoO3) is 5wt% to 30wt%, preferably 20wt%.

[0019] Preferably, the stirring rate in step (3) is 300 r / min.

[0020] Preferably, the calcination temperature in step (4) is 300-500°C, preferably 450°C.

[0021] Preferably, the volume concentration of sulfide gas in step (5) is H2S / H2=5%~90%, preferably 10%.

[0022] Preferably, the vulcanization temperature in step (5) is 250-700°C.

[0023] Preferably, the vulcanization temperature in step (5) is 250°C for in-situ vulcanization for 4 hours, and then raised to 350°C for further vulcanization for 4 hours.

[0024] Preferably, the final product is CuKMoS2 / SiO2.

[0025] Application: Application of CuKMoS2 / SiO2 catalyst in the synergistic preparation of methyl mercaptan from carbon dioxide and hydrogen sulfide: The reaction temperature for the synergistic preparation of methyl mercaptan from H2S and CO2 is 200~500℃, and the reaction pressure is 0.5~1.8 MPa. Preferably, the reaction temperature is 320℃ and the reaction pressure is 1.5MPa.

[0026] Preferably, the amount of the CuKMoS2 / SiO2 catalyst is 1 g; the volume concentration of H2S is 4%, the volume concentration of CO2 is 1%, the volume concentration of H2 is 4%, and N2 is the balance gas.

[0027] The present invention has the following advantages and beneficial effects:

[0028] 1. By introducing a small amount of copper (Cu) into the KMoS2 / SiO2 catalyst, this invention significantly improves the catalyst's selectivity for the reaction intermediate methanol (CH3OH), thereby enhancing the selectivity for the formation of methyl mercaptan (CH3SH). Compared to the KMoS2 / SiO2 catalyst, under the same conditions, the catalyst of this invention more effectively promotes the formation of the target product methyl mercaptan while reducing the formation of byproducts, particularly unnecessary byproducts such as methane (CH4).

[0029] 2. By grinding the Mo and Cu precursors under a warm baking lamp, Cu can be effectively bonded to the Mo structure and the dispersion of Cu can be promoted, so that a small amount of Cu addition can obtain high catalytic reaction activity.

[0030] 3. The introduction of copper (Cu) not only promotes electron transfer in the active center, but also regulates the reaction path of CO2 and H2S, making the reaction more inclined to produce methyl mercaptan.

[0031] 4. The catalyst preparation method of the present invention is simple, and the active components of Cu, K, and MoS2 can be loaded through conventional impregnation and sulfurization processes. This process is reproducible, suitable for industrial large-scale production, and has low cost and good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 X-ray powder diffraction spectra of the catalysts prepared in Examples 1, 2, and 3 of the present invention and Comparative Examples 1 and 2;

[0033] Figure 2 The EPR diagrams of the catalysts prepared in Examples 1, 2, and 3 of the present invention and Comparative Examples 1 and 2 are shown;

[0034] Figure 3 TEM and mapping images of 0.05CuKMo / SiO2 prepared in Example 1 of the present invention;

[0035] Figure 4 TEM image of Example 1 of the present invention;

[0036] Figure 5 N2 adsorption isotherms of Example 1 and Comparative Example 1 of the present invention;

[0037] Figure 6 The pore size distribution diagrams of Example 1 and Comparative Example 1 of the present invention;

[0038] Figure 7 This is the Cu LMMXPS characterization of Example 1 of the present invention;

[0039] Figure 8 The Mo 3d XPS characterization of Example 1 of the present invention and Comparative Example 1 is shown. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to embodiments and drawings. The examples described are intended to further illustrate the present invention rather than to limit the contents of the present invention.

[0041] Example 1

[0042] A method for preparing CuKMoS2 / SiO2 is described: 1.74 mmol of potassium molybdate and 0.085 mmol of copper nitrate are weighed and mixed. An equal volume of water is added dropwise to initially moisten the powder. The mixture is then ground under a warming lamp. During the grinding process, 5 mL of an aqueous solution containing 1.74 mmol of citric acid is slowly added dropwise. After grinding for 15 minutes, the mixture is transferred to a beaker, 1 g of a SiO2 carrier is added, and the mixture is stirred at 80°C at 300 rpm until slightly dry. After drying at 80°C for 12 hours, the sample is calcined at 400°C in a muffle furnace under a nitrogen atmosphere for 3 hours. After cooling to room temperature, the product is sieved to a mesh size of 40-60. The product is then in situ sulfurized at 250°C for 4 hours in a reaction gas (10% H2S / H2 mixture), then raised to 350°C and sulfurized for another 4 hours. The final product, designated 0.05CuKMo / SiO2, is obtained.

[0043] Example 2

[0044] A method for preparing CuKMoS2 / SiO2 is described: 1.74 mmol potassium molybdate and 0.1275 mmol copper nitrate are weighed and initially moistened with water equal to the powder volume. The mixture is then ground under a warming lamp. During the grinding process, 5 mL of an aqueous solution containing 1.74 mmol citric acid is slowly added dropwise. After grinding for 15 minutes, the mixture is transferred to a beaker, 1 g of a SiO2 carrier is added, and the mixture is stirred at 80°C at 300 rpm until slightly dry. After drying at 80°C for 12 hours, the sample is calcined at 400°C for 3 hours in a muffle furnace. After cooling to room temperature, the product is sieved to a mesh size of 40-60. The product is then in situ sulfurized at 250°C for 4 hours in a reaction gas (10% H2S / H2 mixture), then raised to 350°C and sulfurized for another 4 hours. The final product, designated 0.075CuKMo / SiO2, is obtained.

[0045] Example 3

[0046] A method for preparing CuKMoS2 / SiO2 is described: 1.74 mmol potassium molybdate and 0.0425 mmol copper nitrate are weighed and initially moistened with an equal volume of water. The mixture is then ground under a warming lamp. During the grinding process, 5 mL of an aqueous solution containing 1.74 mmol citric acid is slowly added dropwise. After grinding for 15 minutes, the mixture is transferred to a beaker and 1 g of a SiO2 carrier is added. The mixture is stirred at 80°C at 300 rpm until slightly dry. After drying at 80°C for 12 hours, the sample is calcined in a muffle furnace at 400°C for 3 hours. After cooling to room temperature, the product is sieved to a mesh size of 40-60. The product is then in situ sulfurized at 250°C for 4 hours in a reaction gas (10% H2S / H2 mixture), then raised to 350°C and sulfurized for another 4 hours. The final product, designated 0.025CuKMo / SiO2, is obtained.

[0047] Comparative Example 1 (no Cu added)

[0048] A K2MoS x Preparation of KMo / SiO2: 1.74 mmol of potassium molybdate was weighed and initially moistened with an equal volume of water. The mixture was then ground under a warming lamp. During the grinding process, 5 mL of an aqueous solution containing 1.74 mmol of citric acid was slowly added dropwise. After grinding for 15 minutes, the mixture was transferred to a beaker, and 1 g of SiO2 support was added. The mixture was stirred at 80°C at 300 rpm until slightly dry. After drying at 80°C for 12 hours, the sample was calcined in a muffle furnace at 400°C for 3 hours. After cooling to room temperature, the product was sieved to a mesh size of 40-60. The product was then in situ sulfurized at 250°C for 4 hours in a reaction gas (10% H2S / H2 mixture), then raised to 350°C and sulfurized for another 4 hours. The final product, designated KMo / SiO2, was obtained.

[0049] Comparative Example 2 (without Cu and K)

[0050] A MoS x Preparation of Mo / SiO2: 1.49 mmol of ammonium molybdate was weighed and ground under a warming lamp. An equal volume of water was added dropwise to initially moisten the powder. During the grinding process, 5 mL of an aqueous solution containing 1.74 mmol of citric acid was slowly added dropwise. After grinding for 15 minutes, the mixed solution was transferred to a beaker, and 1 g of SiO2 carrier was added. The mixture was stirred at 80°C at 300 rpm until slightly dry. After drying at 80°C for 12 hours, the sample was calcined in a muffle furnace at 400°C for 3 hours. After cooling to room temperature, the product was sieved to a mesh size of 40-60. The product was then in situ sulfurized at 250°C for 4 hours in a reaction gas (10% H2S / H2 mixture), then raised to 350°C and sulfurized for another 4 hours. The final product, designated Mo / SiO2, was obtained.

[0051] Application Experiment

[0052] 1g of catalyst was loaded into a fixed-bed reactor, and the reaction pressure was set at 1.5 MPa and a total space velocity of 300 GHSV. The reactor was started, heated to the target reaction temperature, and the system stabilized. A reaction gas consisting of 4% by volume H2S / 1% by volume CO2 / 4% by volume H2 / N2 was introduced. The reaction products were condensed and analyzed by online gas chromatography for methyl mercaptan yield and selectivity. The formation of intermediate products, such as methanol, was also monitored.

[0053] X-ray powder diffraction (XRD): The phase characterization of the samples was carried out using an X'pert pro powder diffractometer from Panalytical. The detector was an X'celerator, the copper target (Cu Kα, λ = 0.154 nm) was used as the excitation radiation source, the operating voltage was 45 KV, and the operating current was 40 mA.

[0054] N2 physisisorption: Specific surface area, pore size distribution, and other parameters of the sample were determined using N2 physisisorption. The instrument used was a 3Flex fully automatic analyzer manufactured by Micrometrics (USA). The test conditions were as follows: 0.15 g of sample was pre-treated and degassed at 250°C for 4 hours, cooled to room temperature, and then static adsorption was performed in a cold trap cooled to -196°C with liquid nitrogen to obtain textural information. The specific surface area and pore size distribution of the sample were calculated using the BET equation and the BJH model, respectively.

[0055] Electron Paramagnetic Resonance (EPR): Defects or oxygen vacancies in the sample can be detected using a Bruker E-500 electron paramagnetic resonance instrument. Measurements are performed at room temperature and a frequency of 100 kHz. After placing the sample in a quartz cuvette, the cuvette must be kept upright, and the instrument's operating environment must be stable and well-ventilated.

[0056] Scanning electron microscopy (SEM): The morphology of the catalyst was observed using an S-4800 field emission scanning electron microscope. The vacuum degree of the analysis chamber was less than 2.7×10 –6 Pa, the scanning voltage and current were 5 kV and 7 μA respectively. The sample powder was stuck on the conductive glue and sprayed with gold before observation.

[0057] X-ray Photoelectron Spectroscopy (XPS): EscaLab 250Xi spectrometer was used to analyze the elemental composition and chemical state of the catalyst surface. The excitation light source was Al target Kα radiation, and the vacuum degree of the analysis chamber was <10 –8 bar, the excitation power was 22.5 W, and the binding energy of C1s at 284.8 eV was used for calibration.

[0058] Field emission transmission electron microscopy (TEM): TEM images of the samples were observed on a JEM-F200 transmission electron microscope (TEM) with an accelerating voltage of 200 kV.

[0059] Figure 1 The XRD patterns of Examples 1, 2, and 3 of the present invention and Comparative Examples 1 and 2 show that the peak at 9° is that of 1T-MoS2. The incorporation of K is beneficial to the formation of 1T-MoS2. With the addition of Cu, the peak attributable to Cu appears.0.67 Mo6S 0.95 The peak indicates that there is a bond between Cu and MoS2, and it is not a simple free state. As the amount of Cu added increases, the aggregation of K2SO4 in the catalyst becomes more obvious, indicating that excessive Cu addition may have an adverse effect on the catalytic effect.

[0060] Figure 2 These are the EPR graphs of Examples 1, 2, and 3 of the present invention and Comparative Examples 1 and 2. It can be seen from the graph that with the increase in the amount of Cu added, the sulfur vacancies of the catalyst first increase and then decrease. Combined with the XRD characterization, it can be inferred that the K2SO4 on the surface covers the catalytic active sites, which is not conducive to the sulfurization of the catalyst.

[0061] Figure 3 TEM and mapping images of 0.05CuKMo / SiO2 prepared in Example 1 of the present invention. It can be observed from the figure that Cu and Mo are partially deposited on the surface of the carrier, but most of them still penetrate into the pores of the carrier and are dispersed relatively evenly.

[0062] Figure 4 This is the TEM image of Example 1 of the present invention. It can be seen from the figure that MoS2 has multiple crystal planes, and the molybdenum disulfide prepared by this method can expose more active sites.

[0063] Figure 5 The N2 adsorption isotherms of Example 1 and Comparative Example 1 of the present invention are both type IV isotherms.

[0064] Figure 6 The pore size distribution diagrams of Example 1 and Comparative Example 1 of the present invention show that the particle size of the samples is more uniform after Cu is added.

[0065] Figure 7 The Cu LMMXPS characterization of Example 1 of the present invention shows that Cu exists in two forms: 0-valent and 1-valent. 0 Can adsorb and dissociate H2, Cu + It can stabilize the reaction intermediate methoxy group.

[0066] Figure 8 This is the Mo 3d XPS characterization of Example 1 of the present invention and Comparative Example 1. It can be seen that after Cu doping, Mo 6+ The peak of Cu is obviously lowered, indicating that Cu doping can effectively induce the sulfidation of Mo.

[0067] Tables 1 and 2 show the CO2 conversion rate and CH3SH selectivity data of the catalysts of Examples 1, 2, and 3 of the present invention and Comparative Examples 1 and 2 under different reaction temperature conditions. In the reaction of CO2 and H2S synergistically preparing CH3SH, the CO2 conversion rate of all catalysts increases with increasing reaction temperature. As can be seen from Tables 1 and 2, when the reaction temperature is 320°C, the methyl mercaptan selectivity of Example 1 is the highest, at 90.1%; when the reaction temperature is 320°C, the methyl mercaptan selectivity of Example 2 is the highest, at 86.4%; the selectivity of all examples is better than that of Comparative Example 1, that is, the Cu-doped KMoS2 / SiO2 designed by the present invention has better performance.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

[0072] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a CuKMoS2 / SiO2 catalyst for the synergistic preparation of methyl mercaptan from carbon dioxide and hydrogen sulfide, characterized in that: The following steps are involved: (1) Mix Cu(NO3)2·3H2O and K2MoO4 and add a small amount of water for initial wetting; (2) grinding the mixture obtained in step (1) under a warming lamp, and gradually adding citric acid aqueous solution during the grinding process; (3) Adding SiO2 carrier to the solution obtained in step (2) and stirring at 80°C to allow the metal ions to be evenly impregnated into the carrier; (4) Dry the impregnated sample and calcine it under N2 atmosphere to promote the decomposition and fixation of the precursor; (5) Sulfidation in H2S atmosphere to form MoS2 structure and introduce sulfur element into the catalyst to finally form CuKMoS2 / SiO2 catalyst; The molar ratio of Mo to Cu in step (1) is 1:0.01 to 1:0.

5.

2. The preparation method according to claim 1, wherein: The concentration of the citric acid aqueous solution in step (2) does not exceed 25 wt%.

3. The preparation method according to claim 1, wherein: The grinding time in step (2) does not exceed 20 minutes.

4. The preparation method according to claim 1, wherein: In step (3), the loading amount of Mo on the carrier is 5 wt% to 30 wt% calculated as MoO3.

5. The preparation method according to claim 1, wherein: The calcination temperature in step (4) is 300-500°C.

6. The preparation method according to claim 1, wherein: The concentration of sulfide gas in step (5) is H2S / H2=5%~90%.

7. The preparation method according to claim 1, wherein: The temperature of vulcanization in step (5) is 250-700°C.

8. A CuKMoS2 / SiO2 catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the CuKMoS2 / SiO2 catalyst according to claim 8 in the coordinated preparation of methyl mercaptan by carbon dioxide and hydrogen sulfide, characterized in that: When H2S and CO2 are used to synergistically prepare methyl mercaptan, the volume ratio of the components in the raw gas is H2:H2S:CO2=4:4:1, the reaction temperature is 200~500 ℃, and the reaction pressure is 0.5~1.8 MPa.

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