Preparation and desulfurization application of indium-modified hydrotalcite derivative sulfide

Abstract

The invention discloses preparation and desulfurization application of indium modified hydrotalcite derivative sulfide. The method comprises the following steps: calcining a ternary hydrotalcite precursor to obtain a hydrotalcite-derived oxide, soaking the hydrotalcite-derived oxide in an indium precursor solution, stirring, drying, calcining, and vulcanizing to obtain the indium-modified hydrotalcite-derived sulfide catalyst. The atomic radius of In is larger than that of the S element, and the In is introduced into the lattice structure of MoS2, so that the interlayer spacing of MoS2 can be enlarged, the number of stacked layers of MoS2 can be reduced, generation of edge vacancies is promoted, favorable conditions are created for formation of sulfur vacancies, and high catalytic stability is kept. The indium modified hydrotalcite derivative sulfide prepared by the method has rich sulfur vacancies and better stability, is beneficial to promoting desorption and activation of intermediate products and by-products, and shows high catalytic activity and target product selectivity in the reaction of catalyzing CO2 / H2S hydrogenation to prepare methyl mercaptan.

Description

Technical Field

[0001] The present invention relates to a preparation technology of an environmental catalyst and its application field, and particularly relates to a preparation method of indium-modified hydrotalcite-derived sulfide and its application in the hydrogenation of CO2 / H2S to methanethiol. Background Art

[0002] In the mining operations of coal, petroleum, and natural gas, not only highly toxic hydrogen sulfide (H2S) is generated, but also a large amount of carbon dioxide (CO2) is associated. The presence of CO2 will reduce the calorific value of natural gas and weaken its pipeline transportation capacity; moreover, as a typical greenhouse gas, CO2 will cause a series of ecological and environmental problems such as global warming. Based on this, the pollution control of H2S and the emission reduction of CO2 are extremely urgent. Currently, the solvent method is mainly used in the industrial field to separate CO2 and H2S first. For the separated CO2, it is generally first captured, then compressed, and finally the compressed CO2 is transported to the oil well underground. This method not only realizes the sequestration of CO2 but also can improve the oil recovery rate of the oil field. However, this method has the problem of poor safety. CO2 will react chemically with underground heavy metals and then penetrate, polluting the groundwater.

[0003] In recent years, the co-catalysis of CO2 and H2S has become a research hotspot. Some researchers have proposed to convert acidic gases (CO2 and H2S) into elemental sulfur and syngas (H2 + CO) with industrial value through pyrolysis reactions or redox reactions. However, the results of numerical simulation studies show that only when the temperature is above 1550 °C and the composition of the acidic gas meets specific conditions (H2S content < 60%), can an ideal syngas (H2 / CO ratio between 0.33 - 1.26) suitable for fuel engines or ammonia synthesis be generated, which indicates that the reaction conditions are extremely harsh and difficult to effectively control. Using H2S and CO2 as raw materials to synthesize methanethiol by a one-step method, this process can not only realize the simultaneous conversion of H2S and CO2 but also obtain a high-value-added product, methanethiol, thus achieving the maximum utilization of resources. Methanethiol, as a key raw material for fine chemical production and an industrial synthetic organic intermediate, has attracted much attention due to its wide range of uses and significant economic benefits. It can be applied to the synthesis in fields such as pesticides, pharmaceuticals, and food, and particularly plays an important role in the preparation of the feed additive methionine. This fully shows that the reaction route of preparing methanethiol by the co-conversion of CO2 and H2S is a very valuable exploration route. Summary of the Invention

[0004] One-step synthesis of methanethiol from H2S and CO2 can not only simultaneously convert H2S and CO2, but also obtain high-value-added product methanethiol, maximizing the utilization of sulfur and carbon resources. It is a desulfurization process with application prospects, and the development of new, efficient and stable desulfurization catalysts is the key to realizing this process.

[0005] Double metal composite oxides (LDO) are the calcination products of layered double hydroxides (LDH). Compared with LDH, they have stable metal dispersion, larger specific surface area, more active sites and stronger redox synergy effect. However, the catalytic activity of LDO is usually limited by the tendency of aggregation and the lack of good electron transfer ability, which hinders the formation of more vacancies. Loading MoS2 on LDO can solve these problems. Considering that the layers of MoS2 are prone to stack and aggregate under high temperature and pressure, resulting in a decrease in its surface energy and a reduction in the exposure of edge active sites, affecting the catalytic activity. Therefore, introducing In with an atomic radius larger than that of S element into the lattice structure of MoS2 can expand the layer spacing of MoS2, reduce its stacking layers, and promote the generation of edge vacancies, thereby improving the catalytic activity of the catalyst in the hydrogenation of H2S and CO2 to methanethiol.

[0006] The purpose of the present invention is to provide a preparation method and application of indium-modified hydrotalcite-derived sulfide aiming at the deficiencies of the prior art, and to solve the problems such as poor sulfur tolerance and insufficient active sites of the catalyst in the prior art. The indium-modified hydrotalcite-derived sulfide catalyst provides more sulfur vacancies through indium doping, shows excellent catalytic activity and selectivity in the reaction of catalytic hydrogenation of CO2 / H2S to methanethiol, and also has good activity stability.

[0007] To achieve the above purpose, the present invention is realized through the following technical solutions: A preparation method of indium-modified hydrotalcite-derived sulfide, comprising the following steps: (1) Weigh a certain amount of titanium source and dissolve it in an organic solvent, stir to obtain solution 1; then dissolve a certain amount of metal salt and anion source in deionized water to obtain solution 2; mix solution 1 and solution 2, stir, hydrothermal react for a period of time, then wash and dry to obtain a ternary hydrotalcite precursor; (2) Weigh a certain amount of the ternary hydrotalcite precursor and place it in a muffle furnace for calcination for a period of time to obtain a hydrotalcite-derived oxide; (3) Sieve the hydrotalcite-derived oxide prepared in step (2) and reserve it. Weigh a certain amount of indium salt and complexing agent to prepare an indium precursor solution, immerse the sieved hydrotalcite-derived oxide powder in the solution, stir and dry to obtain indium-modified hydrotalcite-derived oxide powder; (4) The indium-modified hydrotalcite-derived oxide powder obtained in step (3) is placed in a muffle furnace for calcination for a period of time, and then transferred to a sulfidation device for sulfidation. After cooling, indium-modified hydrotalcite-derived sulfide is finally obtained.

[0008] Preferably, in step (1), the titanium source is tetrabutyl titanate, and the addition amount is 1-5 mmol.

[0009] Preferably, in step (1), the metal salts are cobalt nitrate and aluminum nitrate, and the addition amount is 1-5 mmol; the anion source is urea, and the addition amount is 10-20 mmol.

[0010] Preferably, in step (1), the hydrothermal time is 8-20 h; the hydrothermal temperature is 120-160 h.

[0011] Preferably, in step (2), the calcination temperature is 400-600 °C; the holding time is 3-6 h.

[0012] Preferably, in step (3), the indium salt is indium nitrate; the complexing agents are citric acid and potassium molybdate.

[0013] Preferably, in step (3), the stirring time is 10-20 h; the drying temperature is 60-100 °C; the drying time is 10-20 h.

[0014] Preferably, in step (4), the calcination temperature is 400-600 °C, and the calcination time is 1-5 h; the sulfidation temperature is 250-400 °C, and the sulfidation time is 5-12 h.

[0015] Preferably, in the indium-modified hydrotalcite-derived sulfide, the In / Mo molar ratio is 5%-7%.

[0016] Preferably, the final product, indium-modified hydrotalcite-derived sulfide, is the calcined powder.

[0017] An application of the indium-modified hydrotalcite-derived sulfide prepared by the above preparation method: for the reaction of hydrogenation of CO2 / H2S to methanethiol.

[0018] Preferably, the reaction temperature for the hydrogenation of CO2 / H2S to methanethiol is 200-360 °C.

[0019] Preferably, the dosage of the indium-modified hydrotalcite-derived sulfide catalyst is 1 g; the volume percentage of the raw material gas is 1% CO2, 4% H2S, 4% H2, and the balance gas nitrogen.

[0020] Further, the specific conditions for indium-modified hydrotalcite-derived sulfide as a catalyst for the hydrogenation of CO2 / H2S to methanethiol are as follows: the volume percentages of the reaction raw material gases are 1% CO2, 4% H2S, 4% H2, and balance gas nitrogen, the reaction pressure is 1.5 MPa, and the reaction temperature is 200 - 360 °C. The outlet gas after the reaction is collected and analyzed by a GC-9790Plus gas chromatograph, the detector is a TCD detector, and the chromatographic column uses an Agilent 19095P-QQ4 capillary column. The test temperature points are spaced at 40 °C intervals, stay at each temperature point for 2 h, collect data every 20 min, and take the average value of the last three results.

[0021] In the present invention, a hydrotalcite-derived oxide is obtained by calcining a ternary hydrotalcite precursor, soaked in an indium precursor solution and stirred, dried, and then sulfided after calcination to obtain an indium-modified hydrotalcite-derived sulfide catalyst. The preparation method of this catalyst is simple and has strong repeatability. Urea is used as a homogeneous precipitant and an anion source. It will decompose gently and uniformly under heating to generate ammonia, which makes the pH value of the solution increase steadily, providing a suitable alkaline environment for the formation of LDH by metal ions and facilitating the formation of LDH with good crystallinity and high purity. In addition, the carbonate ions generated by the reaction of the decomposed carbon dioxide and ammonia can be used as the interlayer anions of the hydrotalcite. Introducing In into the lattice structure of MoS2 can expand the layer spacing of MoS2, reduce its stacking layers, and promote the generation of edge vacancies, thereby improving the catalytic activity of the catalyst in the hydrogenation of H2S and CO2 to methanethiol and maintaining high catalytic stability. The indium-modified hydrotalcite-derived sulfide (denoted as xInK2Mo / CoAl1Ti1-S) prepared in the present invention has abundant sulfur vacancies and good stability, which is beneficial to promoting the desorption and activation of intermediate products and by-products, and making it show high catalytic activity and target product selectivity in the reaction of catalytic hydrogenation of CO2 / H2S to methanethiol.

[0022] The present invention has the following advantages and beneficial effects: 1. The introduced In in the present invention further weakens the metal-sulfur bond and reduces the number of strong basic sites, generates more sulfur vacancies, and promotes the desorption of intermediate products and by-products; 2. For the indium-modified hydrotalcite-derived sulfide synthesized in the present invention, the modification of In enhances the electron transfer ability of the catalyst without affecting the basic structure; 3. The indium-modified hydrotalcite-derived sulfide catalyst provided by the present invention has good catalytic activity and selectivity, and strong sulfur tolerance stability. Description of the Drawings

[0023] Figure 1 X-ray powder diffraction patterns of the indium-modified hydrotalcite-derived sulfide and the corresponding precursors prepared in Examples 1 - 3 and Comparative Example 1 of the present invention; Figure 2 Scanning electron micrographs of indium-modified hydrotalcite-derived sulfides prepared in Examples 1 to 3 of the present invention. a-c are Example 1, d-f are Example 2, and g-i are Example 3; Figure 3 Transmission electron micrograph of indium-modified hydrotalcite-derived sulfide prepared in Example 2 of the present invention; Figure 4 Raman spectra of indium-modified hydrotalcite-derived sulfides prepared in Examples 1 to 3 and Comparative Example 1 of the present invention; Figure 5 EPR spectra of indium-modified hydrotalcite-derived sulfides prepared in Examples 1 to 3 and Comparative Example 1 of the present invention; Figure 6 H2-TPR spectra of indium-modified hydrotalcite-derived sulfides prepared in Examples 1 to 3 and Comparative Example 1 of the present invention; Figure 7 Catalytic activity result diagrams of indium-modified hydrotalcite-derived sulfides prepared in Examples 1 to 3 and Comparative Example 1 of the present invention in the hydrogenation of CO2 / H2S to methanethiol. Detailed implementation manners

[0024] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described in detail below with reference to examples and drawings. The examples described are further illustrations of the present invention rather than limitations on the content of the present invention.

[0025] Example 1 A preparation method of indium-modified hydrotalcite-derived sulfide: Dissolve 3 mmol of tetrabutyl titanate (Ti(OC4H9)4) in 30 mL of isopropanol and continuously stir for half an hour. Then, dissolve 3 mmol of Co(NO3)2·6H2O, Al(NO3)3·9H2O, and 18 mmol of urea successively in 100 mL of deionized water (the molar ratio of titanium to aluminum is 1:1). After mixing the above two solutions, continuously stir for half an hour. Then, pour the mixed solution into a 150 mL hydrothermal autoclave and react at 140 °C for 12 hours. After the temperature of the hydrothermal autoclave drops to room temperature, collect the precipitate and centrifuge and wash it 3 times with anhydrous ethanol and deionized water in sequence. Then, place the filter cake in an oven at 80 °C to dry and obtain the ternary hydrotalcite precursor powder. Transfer this powder to a muffle furnace and calcine it at 500 °C for 4 h to obtain the hydrotalcite-derived oxide CoAl1Ti1-LDO, and sieve it to 40 - 60 mesh for standby. Measure 1.5 g of deionized water, and simultaneously weigh 0.413 g of potassium molybdate, 0.34 g of citric acid, and In(NO3)3·4H2O with an In / Mo molar ratio of 3% and dissolve them in 1.5 g of deionized water. After the solution is clear and transparent, add 1 g of the sieved CoAl1Ti1-LDO and completely immerse it below the solution surface. Stir it multiple times at room temperature and transfer it to an oven at 80 °C to dry for 12 h after 12 h, and then calcine it at 450 °C for 2 h. Then, transfer this sample to a sulfidation device and maintain it at 400 °C for 8 hours at a flow rate of 10 mL / min in an atmosphere of 10% H2S / H2 by volume concentration. Cool it to room temperature to obtain the indium-modified hydrotalcite-derived sulfide, denoted as 3InK2Mo / CoAl1Ti1-S catalyst.

[0026] Example 2 Preparation method of indium-modified hydrotalcite-derived sulfide: Dissolve 3 mmol of tetrabutyl titanate (Ti(OC4H9)4) in 30 mL of isopropanol and continuously stir for half an hour. Then, dissolve 3 mmol of Co(NO3)2·6H2O, Al(NO3)3·9H2O, and 18 mmol of urea successively in 100 mL of deionized water (the molar ratio of titanium to aluminum is 1:1). After mixing the above two solutions, continuously stir for half an hour. Then, pour the mixed solution into a 150 mL hydrothermal autoclave and react at 140 °C for 12 hours. After the temperature of the hydrothermal autoclave drops to room temperature, collect the precipitate and centrifuge and wash it 3 times with anhydrous ethanol and deionized water in sequence. Then, place the filter cake in an oven at 80 °C to dry, and obtain the ternary hydrotalcite precursor powder. Transfer this powder to a muffle furnace and calcine it at 500 °C for 4 h to obtain the hydrotalcite-derived oxide CoAl1Ti1-LDO, and sieve it to 40-60 mesh for standby. Measure 1.5 g of deionized water, and simultaneously weigh 0.413 g of potassium molybdate, 0.34 g of citric acid, and In(NO3)3·4H2O with an In / Mo molar ratio of 5% and dissolve them in 1.5 g of deionized water. After the solution is clear and transparent, add 1 g of sieved CoAl1Ti1-LDO and immerse it completely below the solution surface. Stir it multiple times at room temperature and transfer it to an oven at 80 °C to dry for 12 h after 12 h, and then calcine it at 450 °C for 2 h. Then, transfer this sample to a sulfidation device and keep it at 400 °C for 8 hours at a flow rate of 10 mL / min in an atmosphere of 10% H2S / H2 by volume concentration. Cool it to room temperature to obtain the indium-modified hydrotalcite-derived sulfide, denoted as 5InK2Mo / CoAl1Ti1-S catalyst.

[0027] Example 3 Preparation method of indium-modified hydrotalcite-derived sulfide: Dissolve 3 mmol of tetrabutyl titanate (Ti(OC4H9)4) in 30 mL of isopropanol and continuously stir for half an hour. Then, dissolve 3 mmol of Co(NO3)2·6H2O, Al(NO3)3·9H2O, and 18 mmol of urea successively in 100 mL of deionized water (the molar ratio of titanium to aluminum is 1:1). After mixing the above two solutions, continuously stir for half an hour. Then, pour the mixed solution into a 150 mL hydrothermal autoclave and react at 140 °C for 12 hours. After the temperature of the hydrothermal autoclave drops to room temperature, collect the precipitate and centrifuge and wash it 3 times with anhydrous ethanol and deionized water in sequence. Then, place the filter cake in an oven at 80 °C to dry, and obtain the ternary hydrotalcite precursor powder. Transfer this powder to a muffle furnace and calcine it at 500 °C for 4 h to obtain the hydrotalcite-derived oxide CoAl1Ti1-LDO, and sieve it to 40 - 60 mesh for standby. Measure 1.5 g of deionized water, and simultaneously weigh 0.413 g of potassium molybdate, 0.34 g of citric acid, and In(NO3)3·4H2O with an In / Mo molar ratio of 7% and dissolve them in 1.5 g of deionized water. After the solution is clear and transparent, add 1 g of sieved CoAl1Ti1-LDO and immerse it completely below the solution surface. Stir it multiple times at room temperature and transfer it to an oven at 80 °C to dry for 12 h after 12 h, and then calcine it at 450 °C for 2 h. Then, transfer this sample to a sulfidation device, and under an atmosphere of 10% H2S / H2 by volume concentration, maintain it at 400 °C for 8 hours at a flow rate of 10 mL / min. Cool it to room temperature to obtain the indium-modified hydrotalcite-derived sulfide, denoted as 7InK2Mo / CoAl1Ti1-S catalyst.

[0028] Comparative Example 1 Preparation method of a hydrotalcite-derived sulfide: Dissolve 3 mmol of tetrabutyl titanate (Ti(OC4H9)4) in 30 mL of isopropanol and continuously stir for half an hour. Then, dissolve 3 mmol of Co(NO3)2·6H2O and Al(NO3)3·9H2O and 18 mmol of urea successively in 100 mL of deionized water (the molar ratio of titanium to aluminum is 1:1). After mixing the above two solutions, continuously stir for half an hour. Then, pour the mixed solution into a 150 mL hydrothermal autoclave and react at 140 °C for 12 hours. After the temperature of the hydrothermal autoclave drops to room temperature, collect the precipitate and centrifuge and wash it 3 times with anhydrous ethanol and deionized water in sequence. Then, place the filter cake in an oven at 80 °C to dry, and obtain a ternary hydrotalcite precursor powder. Transfer this powder to a muffle furnace and calcine it at 500 °C for 4 h to obtain a hydrotalcite-derived oxide CoAl1Ti1-LDO, and sieve it to 40 - 60 mesh for standby. Measure 1.5 g of deionized water, and simultaneously weigh 0.413 g of potassium molybdate and 0.34 g of citric acid and dissolve them in 1.5 g of deionized water. After the solution is clear and transparent, add 1 g of the sieved CoAl1Ti1-LDO and make it completely immersed below the solution. Stir it multiple times at room temperature and transfer it to an oven at 80 °C to dry for 12 h after 12 h, and then calcine it at 450 °C for 2 h. Then, transfer this sample to a sulfidation device, and under an atmosphere of 10% H2S / H2 with a volume concentration, keep it at 400 °C for 8 h at a flow rate of 10 mL / min. After cooling to room temperature, a hydrotalcite-derived sulfide is obtained, denoted as the K2Mo / CoAl1Ti1-S catalyst.

[0029] Application example The specific conditions for indium-modified hydrotalcite-derived sulfide as a catalyst for the hydrogenation of CO2 / H2S to methanethiol are as follows: The volume percentage of the reaction raw material gas is 1% CO2, 4% H2S, 4% H2, and balance gas nitrogen. The reaction pressure is 1.5 MPa, and the reaction temperature is 200 - 360 °C. The outlet gas after the reaction is collected and analyzed by a GC-9790Plus gas chromatograph. The detector is a TCD detector, and the chromatographic column uses an Agilent 19095P-QQ4 capillary column. The test temperature point interval is 40 °C, stay at each temperature point for 2 h, collect data every 20 min, and take the average value of the last three results.

[0030] X-ray powder diffraction (XRD): The phase characterization of the sample is measured using an X’pert pro powder diffractometer from Panalytical. The detector is X’celerator, and a copper target (Cu Kα, λ = 0.154 nm) is used as the excitation ray source. The working voltage is 45 KV, and the working current is 40 mA.

[0031] Field emission scanning electron microscope (SEM): The morphology of the catalyst was observed by an S-4800 field emission scanning electron microscope. The vacuum degree in the analysis chamber was less than 2.7×10 -6 Pa, and the scanning voltage and current were 5 kV and 7 μA respectively. The sample powder was adhered to the conductive adhesive and then sputtered with gold for observation.

[0032] Fourier transform infrared spectroscopy (FT-IR): A Nicolet 6700 infrared spectrometer was used to analyze the surface chemical bonds and functional groups of the samples. First, the sample was mixed with KBr and ground evenly, and then pressed into a thin slice by a tablet press and placed in the infrared spectrometer for testing. Scanning range: 400 - 4000 cm -1 -1, the scanning resolution was 4 cm -1 -1, and the number of scans was 64 times.

[0033] Electron paramagnetic resonance spectrum (EPR): Information on the defects or oxygen vacancies of the samples was obtained by an E-500 electron paramagnetic resonance spectrometer (Bruker). The test was carried out at room temperature, and the test frequency was 100 kHz. After the sample was placed in a quartz test tube, the test tube should be kept vertical, and the working environment of the instrument should be kept stable and the air should circulate.

[0034] Raman characterization (Raman): The structural information of the samples was analyzed by an in Via Reflex Raman spectrometer (RENIS-HAW, U.K.). The scanning range was 300 - 2500 cm -1 -1, the excitation light source was λ = 325 nm, the exposure time was 2 - 10 s, the laser intensity was 1%, and the number of scans was 6 times.

[0035] Figure 1 This is the X-ray powder diffraction pattern of the indium-modified hydrotalcite-derived sulfides prepared in Examples 1 - 3 and Comparative Example 1 of the present invention, as well as the hydrotalcite-derived sulfides without indium modification. It can be seen from the figure that the catalyst after adding indium still maintains the structure of coexisting polysulfides. It is worth noting that with the increase of indium content, the characteristic peaks of cobalt sulfide in the catalyst become sharper, and Co3S4 is particularly obvious. And the characteristic peaks belonging to 1T-MoS2 at about 2θ = 10° are shifted to lower angles compared with the catalyst without indium modification, which is caused by the expansion of the MoS2 layer spacing by the addition of indium. Comparing this series of catalysts, when the In / Mo molar ratio is 5%, the 1T-MoS2 characteristic peak is at the lowest position, indicating that the layer spacing of 5InK2Mo / CoAl1Ti1-S is the largest and it may be the catalyst most conducive to defect formation.

[0036] Figure 2SEM images of indium-modified hydrotalcite-derived sulfides prepared in Examples 1-3 and Comparative Example 1 of the present invention. As can be seen from the figures, all samples still retain the flaky characteristics of hydrotalcite, and the accumulation of morphology also appears, indicating that the addition of In has no obvious effect on the morphology of the catalyst.

[0037] Figure 3 TEM image of indium-modified hydrotalcite-derived sulfide prepared in Example 2 of the present invention. As can be seen from the figure, the main lattice spacings are 0.28, 0.30 and 0.62 nm, corresponding to the (311) crystal plane of Co3S4, the (311) crystal plane of Co9S8 and the (002) crystal plane of MoS2 respectively, confirming that the catalyst is a structure with coexistence of polysulfides, which is consistent with the above XRD and Raman analyses.

[0038] Figure 4 Raman spectra of indium-modified hydrotalcite-derived sulfides prepared in Examples 1-3 and Comparative Example 1 of the present invention. As can be seen from the figure, the Raman spectra of the catalyst do not change significantly due to indium modification, and the characteristic peaks of various sulfides are still shown in the spectra. Among them, the spectral peak at about 400 cm -1 corresponds to the out-of-plane Mo-S mode (A 1g ) of 2H-MoS2. Except for the 3InK2Mo / CoAl1Ti1-S catalyst, the in-plane Mo-S phonon mode (E 2g 1 ) of MoS2 is not observed, which may be due to the relatively low content of the 1T-MoS2 phase in this catalyst, which may cause a decrease in catalytic activity. The spectral peaks at 200 and 327 cm -1 correspond to the J1 and J3 modes of 1T-MoS2 respectively. The vibration mode of cobalt sulfide is still observed, indicating that the catalyst is still in a state of coexistence of various sulfides.

[0039] Figure 5 EPR spectra of indium-modified hydrotalcite-derived sulfides prepared in Examples 1-3 and Comparative Example 1 of the present invention. As can be seen from the figure, all catalysts still show an EPR signal peak attributed to sulfur vacancies at g = 2.002, indicating that sulfur defects exist on the catalyst surface. The addition of In enhances this signal peak, indicating that indium modification successfully promotes the further formation of sulfur vacancies. When the In / Mo molar ratio is 5%, the peak intensity is the strongest, indicating that this may be the optimal indium-molybdenum ratio.

[0040] Figure 6 H2-TPR spectra of indium-modified hydrotalcite-derived sulfides prepared in Examples 1-3 and Comparative Example 1 of the present invention. As can be seen from the figure, all catalysts still mainly have two reduction peaks: the reduction of non-stoichiometric sulfur atoms (S x ) located at 200-400 °C (Sx The reduction peak of +xH2→ xH2S) and the reduction peaks of MoS2 and CoS located at 500-600 °C x The reduction peaks of sulfur species in the middle. The modification of In shifts the reduction peak positions of non-stoichiometric sulfur atoms to lower temperatures. It can be seen from XPS analysis that the addition of In improves the electron transfer ability of titanium, further weakens the strength of the metal-sulfur bond, and simultaneously further increases the sulfur vacancy concentration. However, the size of the sulfur species reduction peak of the 3InK2Mo / CoAl1Ti1-S catalyst is lower than that of the K2Mo / CoAl1Ti1-S catalyst, which also indirectly explains the reason for the decrease in the catalytic activity of this catalyst.

[0041] Figure 7 This is the activity diagram of indium-modified hydrotalcite-derived sulfides prepared in Examples 1-3 and Comparative Example 1 of the present invention in the reaction of hydrogenation of CO2 / H2S to methanethiol. Figure 7 In (a) is the change curve of the CO2 conversion rate of the catalyst. In the test temperature range, the conversion rate also shows an upward trend, and the highest CO2 conversion rate exceeds 30%. The change curve of the CH3SH selectivity shows that the product selectivity of the indium-modified catalyst has been improved to a certain extent. The 5InK2Mo / CoAl1Ti1-S catalyst reaches up to 86% at 280 °C, but the selectivity of the catalyst with a molar ratio of In / Mo = 3% decreases instead. There are fewer surface adsorbed oxygen species and a lower concentration of 1T-MoS2 in the 3InK2Mo / CoAl1Ti1-S catalyst, resulting in a decrease in its ability to activate reactants. The curve of the space-time yield of methanethiol is also consistent with the change trend of methanethiol selectivity. The catalyst with a molar ratio of In / Mo = 5% has the optimal CH3SH production rate per unit time, while the 3InK2Mo / CoAl1Ti1-S catalyst is the lowest. Also, due to the excessive hydrogenation of CO2 to form by-products such as CH4 at too high reaction temperatures, the catalytic activity of the catalysts begins to gradually decrease after 280 °C.

[0042] In summary, it can be seen that the indium-modified hydrotalcite-derived sulfides prepared by the present invention have different catalytic performances in the reaction of hydrogenation of CO2 / H2S to methanethiol. Among them, the 5InK2Mo / CoAl1Ti1-S sample has the highest catalytic activity and has great application potential.

[0043] The specific embodiments described above have further detailed the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of indium-modified hydrotalcite-derived sulfide, characterized in that: It includes the following steps: (1) Weigh a certain amount of titanium source and dissolve it in an organic solvent, stir to obtain Solution 1; then dissolve a certain amount of metal salt and anion source in deionized water to obtain Solution 2; mix Solution 1 and Solution 2, stir, hydrothermal react for a period of time, then wash and dry to obtain a ternary hydrotalcite precursor; (2) Weigh a certain amount of the ternary hydrotalcite precursor and calcine it in a muffle furnace for a period of time to obtain a hydrotalcite-derived oxide; (3) Sieve the hydrotalcite-derived oxide prepared in step (2) for standby, weigh a certain amount of indium salt and complexing agent to prepare an indium precursor solution, soak the sieved hydrotalcite-derived oxide powder in the indium precursor solution, stir and dry to obtain indium-modified hydrotalcite-derived oxide powder; (4) Place the indium-modified hydrotalcite-derived oxide powder obtained in step (3) in a muffle furnace and calcine it for a period of time, then transfer it to a sulfidation device for sulfidation, and finally obtain indium-modified hydrotalcite-derived sulfide after cooling.

2. The preparation method of indium-modified hydrotalcite-derived sulfide according to claim 1, characterized in that: The titanium source in step (1) is tetrabutyl titanate, and the organic solvent is isopropanol.

3. The preparation method of indium-modified hydrotalcite-derived sulfide according to claim 1, characterized in that: The metal salts in step (1) are cobalt nitrate and aluminum nitrate, and the anion source is urea.

4. The preparation method of indium-modified hydrotalcite-derived sulfide according to claim 1, characterized in that: The hydrothermal time in step (1) is 8 - 20 h, and the hydrothermal temperature is 120 - 160 °C.

5. The method for preparing indium-modified hydrotalcite-derived sulfide according to claim 1, wherein: The calcination temperature in step (2) is 400 - 600 °C, and it is maintained for 3 - 6 h.

6. The preparation method of indium-modified hydrotalcite-derived sulfide according to claim 1, characterized in that: The indium salt in step (3) is indium nitrate; the complexing agents are citric acid and potassium molybdate.

7. The preparation method of indium-modified hydrotalcite-derived sulfide according to claim 1, characterized in that: The calcination temperature in step (4) is 400 - 600 °C, and it is maintained for 1 - 5 h; the sulfidation time is 5 - 12 h, and the sulfidation temperature is 280 - 400 °C.

8. Indium-modified hydrotalcite-derived sulfide prepared by the preparation method according to any one of claims 1 - 7.

9. Use of the indium-modified hydrotalcite-derived sulfide according to claim 8 in the reaction of catalytic hydrogenation of CO2 / H2S to methanethiol, characterized in that: It is used for the catalytic reaction of hydrogenation of CO2 / H2S to methanethiol, the reaction temperature is 200 - 360 °C, and the reaction pressure is 1.5 Mpa.

10. The application according to claim 9, characterized in that: In the catalytic reaction of hydrogenation of CO2 / H2S to methanethiol, the dosage of the indium-modified hydrotalcite-derived sulfide material is 1 g; the volume percentage of the raw material gas is 1% CO2, 4% H2S, 4% H2 and the balance gas nitrogen.

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