Method for catalytically decomposing hydrogen sulfide using core-shell microwave catalyst and catalyst thereof

Abstract

The present invention provides a method for catalytically decomposing hydrogen sulfide using a core-shell microwave catalyst and a catalyst thereof. The method comprises using the core-shell microwave catalyst to directly catalyze the decomposition of hydrogen sulfide to generate hydrogen and sulfur under microwave conditions, wherein the core-shell catalyst comprises a Ce-Mo2C core structure and a WO3 shell structure coated on the outside of the Ce-Mo2C core structure, which is represented as a Ce-Mo2C@WO3 catalyst. The Ce-Mo2C@WO3 catalyst provided by the present invention can directly catalyze the decomposition of hydrogen sulfide to generate hydrogen and sulfur under microwave conditions, has a high conversion rate at a relatively low temperature, and the catalyst can maintain a relatively high activity for a long time during use, and has good stability.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and particularly relates to a method for using a core-shell type microwave catalyst to catalytically decompose hydrogen sulfide and a catalyst thereof. Background Art

[0002] H 2 S is a toxic and highly corrosive pollutant gas, mainly from natural sources, petroleum refining, natural gas processing, and coal gasification. 2 S is mainly processed by the Claus process, which makes H 2 Incomplete oxidation of S to SO 2 and water, and the reaction temperature is extremely high (>1300K).

[0003] H 2 S directly decomposes to generate H 2 and S, is a sustainable and efficient direct decomposition technology of hydrogen sulfide. 2 The direct decomposition reaction of S faces two major challenges: 1. Thermodynamically, H 2 The direct decomposition reaction of S is limited by thermodynamic equilibrium, even at temperatures as high as 1000 °C, H 2 The conversion rate of S is also very low (the conversion rates at 1010℃ and 1130℃ are only 20% and 30% respectively); 2. Kinetically, H 2 The direct decomposition reaction kinetics of S is slow, and the apparent activation energy is as high as 495.62 kJ / mol. Therefore, finding a suitable catalyst to directly and efficiently decompose hydrogen sulfide is the key to achieving H 2 S is the key to low-temperature, efficient and direct decomposition.

[0004] Chen et al. invented a Mo 2 C-TiO 2 Microwave catalysts are used for the direct decomposition of hydrogen sulfide, where Mo 2 C was prepared by programmed temperature method, which is a cumbersome process and the obtained H 2 The S conversion rate was 48% at 550°C, 66.4% at 600°C, 84% at 650°C, 87.1% at 700°C, and 90.3% at 750°C. They also invented a MoN x @SiO 2 Microwave catalysts were used for the direct decomposition of hydrogen sulfide, with a hydrogen sulfide conversion rate of 92.1% at 700°C. Zhu et al. prepared Mo 2 C@BN microwave catalyst is applied to direct decomposition of hydrogen sulfide, the best Mo 2The hydrogen sulfide conversion rate of C@BN-1000 catalyst is 76.2% at 600°C. Due to the serious thermodynamic equilibrium limitation of the direct decomposition reaction of hydrogen sulfide, the above microwave catalysts are not very active at low temperatures below 600°C for the direct decomposition reaction of hydrogen sulfide. Therefore, it is still necessary to develop new catalysts to further improve the catalytic activity at low temperatures below 600°C. Summary of the invention

[0005] The purpose of the present invention is to improve the use of a new core-shell microwave catalyst that can directly catalyze the decomposition of hydrogen sulfide to generate hydrogen and sulfur under microwave conditions, has a high conversion rate at a relatively low temperature, and the catalyst can maintain a high activity for a long time during use and has good stability.

[0006] In order to achieve the above object, the present invention provides a method for catalytically decomposing hydrogen sulfide using a core-shell microwave catalyst, the method comprising using the core-shell microwave catalyst to directly catalyze the decomposition of hydrogen sulfide to generate hydrogen and sulfur under microwave conditions, the core-shell catalyst comprising Ce-Mo 2 C core structure and cladding on the Ce-Mo 2 WO outside the C core structure 3 Shell structure, represented by Ce-Mo 2 C@WO 3 catalyst.

[0007] In a specific embodiment, the Ce-Mo 2 C@WO 3 The catalyst was prepared by the following method:

[0008] Step (1), preparing powdered Ce-Mo by metal doping and organic-inorganic hybridization 2 C;

[0009] Step (2), using powdered Ce-Mo 2 C was used as raw material to prepare two identical groups of Ce-Mo 2 C solution, and then to one of the Ce-Mo 2 C solution, add metatungstic acid and hydrochloric acid and mix them evenly to obtain a first mixed solution, and add another group of Ce-Mo 2 Add metatungstic acid to solution C and mix well to obtain a second mixed solution;

[0010] Step (3), performing a preset treatment on the first mixed liquid and the second mixed liquid respectively to obtain a first precursor and a second precursor, wherein the preset treatment includes solid-liquid separation, washing and drying performed in sequence;

[0011] Step (4), respectively loading the first precursor and the second precursor into two magnetic boats and placing them in a tube furnace, and calcining them in a nitrogen-containing atmosphere under preset calcination conditions to obtain the Ce-Mo 2 C@WO 3 Catalyst, wherein the magnetic boat loaded with the first precursor is placed in front of the magnetic boat loaded with the second precursor.

[0012] In a specific embodiment, the step (1) comprises:

[0013] After ammonium molybdate, p-phenylenediamine and cerium salt are mixed with a first dispersant, an amine precipitation reaction occurs at 30 to 80° C. under stirring, and a reaction solution including amine precipitation is obtained after the reaction is completed;

[0014] The reaction solution including the amine precipitate is subjected to solid-liquid separation, washing, drying and calcination to obtain a powdered Ce-Mo 2 C.

[0015] In a specific embodiment, the cerium salt is cerium nitrate, the mass ratio of the cerium element in the cerium nitrate to the molybdenum element in ammonium molybdate is 1:(10-20), and the molar ratio of ammonium molybdate to p-phenylenediamine is 1:(0.5-10); the first dispersant includes hydrochloric acid and water, and the volume ratio of the hydrochloric acid to water is 1:(0.1-200).

[0016] In a specific embodiment, the Ce-Mo 2 The method for obtaining the C solution is as follows: 2 C is dispersed in the second dispersant, and then polyvinyl pyrrolidone is added, mixed evenly, and then subjected to ultrasonic and stirring treatment to obtain the Ce-Mo 2 C solution, wherein the second dispersant comprises anhydrous ethanol and water, and the volume ratio of the anhydrous ethanol to water is 1:(1-10).

[0017] In a specific embodiment, the atomic molar ratio of the tungsten element in the metatungstic acid and the molybdenum element in the cerium-doped molybdenum carbide in the first mixed solution and the second mixed solution is 1:(0.5-2).

[0018] In a specific embodiment, in step (4), the nitrogen-containing atmosphere is one or a mixture of nitrogen and ammonia, and the preset calcination conditions include a calcination temperature of 500 to 1000° C. and a calcination time of 3 to 6 hours.

[0019] In a specific embodiment, the reaction temperature for direct catalytic decomposition of hydrogen sulfide under microwave conditions is 400-600°C, preferably 450-550°C.

[0020] The present invention also provides a method for preparing a core-shell type microwave catalyst, wherein the core-shell type catalyst comprises Ce-Mo 2 C core structure and cladding on the Ce-Mo 2 WO outside the C core structure 3 Shell structure, represented by Ce-Mo 2 C@WO 3 Catalyst, the preparation method comprises the following steps:

[0021] Step (1), preparing powdered Ce-Mo by metal doping and organic-inorganic hybridization 2 C;

[0022] Step (2), using powdered Ce-Mo 2 C was used as raw material to prepare two identical groups of Ce-Mo 2 C solution, and then to one of the Ce-Mo 2 C solution, add metatungstic acid and hydrochloric acid and mix them evenly to obtain a first mixed solution, and add another group of Ce-Mo 2 Add metatungstic acid to solution C and mix well to obtain a second mixed solution;

[0023] Step (3), performing a preset treatment on the first mixed liquid and the second mixed liquid respectively to obtain a first precursor and a second precursor, wherein the preset treatment includes solid-liquid separation, washing and drying performed in sequence;

[0024] Step (4), respectively loading the first precursor and the second precursor into two magnetic boats and placing them in a tube furnace, and calcining them in a nitrogen-containing atmosphere under preset calcination conditions to obtain the Ce-Mo 2 C@WO 3 Catalyst, wherein the magnetic boat loaded with the first precursor is placed in front of the magnetic boat loaded with the second precursor.

[0025] The present invention also provides a core-shell type microwave catalyst, which is prepared by the preparation method described above.

[0026] The beneficial effects of the present invention include at least:

[0027] 1. The core-shell catalyst Ce-Mo in the present invention 2 C@WO 3 When hydrogen sulfide is directly decomposed into hydrogen and sulfur under microwave conditions, it exhibits good catalytic activity and stability. When the bed temperature is controlled at 500°C, the conversion rate of hydrogen sulfide can reach 87.61%, and it still maintains good activity after 400 minutes without obvious deactivation, and has high stability.

[0028] 2. Preparation of core-shell catalyst Ce-Mo by the present invention2 C@WO 3 When the first precursor and the second precursor are calcined together, the first precursor is used to provide a tungstic acid environment to make the thermally stable and chemically stable WO 3 Can be well coated on Ce-Mo 2 C surface layer forms a core-shell structure, which is different from the non-shell catalyst Ce-Mo 2 Compared with C, it not only improves the conversion rate at a lower reaction temperature (450-600°C), but also greatly improves the reaction stability of the catalyst.

[0029] 3. The core-shell catalyst Ce-Mo provided by the present invention 2 C@WO 3 The raw materials are easily available, the preparation cost is low, the wave absorbing performance is good, and the efficient direct decomposition of hydrogen sulfide can be achieved at a relatively low reaction temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The core-shell catalyst Ce-Mo prepared in Example 1 2 C@WO 3 XRD pattern of

[0031] Figure 2 The non-core-shell Ce-Mo prepared in Comparative Example 1 2 XRD pattern of catalyst C;

[0032] Figure 3 The relationship between the catalytic activity under microwave conditions, i.e., the hydrogen sulfide conversion rate of the catalysts prepared in Example 1, Comparative Example 2 and Comparative Example 3, and the temperature;

[0033] Figure 4 This is a graph showing the relationship between the catalytic activity, i.e., the hydrogen sulfide conversion rate, of the catalysts prepared in Example 1 and Comparative Example 1 at 500° C. under microwave conditions and time. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and embodiments, but the present invention can be implemented in many different ways as limited and covered by the claims.

[0035] The present invention provides a core-shell type microwave catalyst for catalytically decomposing hydrogen sulfide, wherein the core-shell type catalyst comprises Ce-Mo 2 C core structure and cladding on the Ce-Mo 2 WO outside the C core structure 3 Shell structure, represented by Ce-Mo 2 C@WO 3 catalyst.

[0036] The present invention also provides a method for preparing a core-shell type microwave catalyst, wherein the core-shell type catalyst comprises Ce-Mo 2 C core structure and cladding on the Ce-Mo 2 WO outside the C core structure 3 Shell structure, represented by Ce-Mo 2 C@WO 3 Catalyst, the preparation method comprises the following steps:

[0037] Step (1), preparing powdered Ce-Mo by metal doping and organic-inorganic hybridization 2 C.

[0038] Preferably, Ce-Mo 2 C is prepared by using doped rare metal Ce and p-phenylenediamine as a C precursor.

[0039] Specifically, the step (1) comprises:

[0040] Step (a), after ammonium molybdate, p-phenylenediamine and cerium salt are mixed with the first dispersant, an amine precipitation reaction occurs at 30-80° C. under stirring, and after the reaction is completed, a reaction solution containing amine precipitation is obtained.

[0041] Preferably, the stirring temperature is 50° C. and the stirring speed is 10 to 20 rpm.

[0042] Preferably, the first dispersant includes hydrochloric acid and water, and the volume ratio of the hydrochloric acid to water is 1:(0.1-200), and more preferably, the volume ratio of the hydrochloric acid to water is 1:(10-50).

[0043] In the present invention, the hydrochloric acid is a hydrochloric acid solution with a mass fraction of 36%.

[0044] In step (a), hydrochloric acid is added under heating and stirring.

[0045] The step (a) is specifically as follows: after adding ammonium molybdate and p-phenylenediamine into water, cerium salt is added, mixed evenly, and then vigorously stirred at 30-80° C. for a preset time to obtain a reaction solution including amine precipitate, wherein hydrochloric acid with a mass fraction of 36% is added under heating and stirring.

[0046] In the present invention, the cerium salt is cerium nitrate.

[0047] Preferably, the mass ratio of the cerium element in cerium nitrate to the molybdenum element in ammonium molybdate is 1:(10-20).

[0048] Preferably, the molar ratio of ammonium molybdate to p-phenylenediamine is 1:(0.5-10), and more preferably, the molar ratio of ammonium molybdate to p-phenylenediamine is 1:(2-6).

[0049] Preferably, the reaction time (preset time) of the amine precipitation reaction is 2 to 3 hours.

[0050] Preferably, the reaction temperature of the amine precipitation reaction is 40-60°C.

[0051] Step (b), subjecting the reaction solution including the amine precipitate to solid-liquid separation, washing, drying, and calcination to obtain a powdered Ce-Mo 2 C.

[0052] In step (b), the solid-liquid separation method is suction filtration, and distilled water is used for washing.

[0053] Preferably, the drying temperature in step (b) is 80 to 120° C., and the drying time is 12 to 24 hours.

[0054] Preferably, the calcination process conditions in step (b) include: the calcination atmosphere is nitrogen, the calcination temperature is 500-1000°C, and the calcination time is 8-16h. More preferably, the calcination temperature in step (b) is 700-900°C, and the calcination time is 12-14h.

[0055] Preferably, the calcination process conditions in step (b) further include: a heating rate of 1 to 10° C. / min, more preferably, a heating rate of 5° C. / min.

[0056] The calcination process in step (b) is as follows: the dried amine precipitate is loaded into a magnetic boat, the magnetic boat is placed in a tube furnace, and then nitrogen is introduced, and the temperature is raised to 500-1000°C at a rate of 5°C / min at room temperature and calcined for 8-16 hours, and Ce-Mo is obtained after cooling. 2 C powder.

[0057] Step (2), using powdered Ce-Mo 2 C as raw materials to prepare two groups of the same Ce-Mo 2 C solution, and then to one of the Ce-Mo 2 C solution, add metatungstic acid and hydrochloric acid and mix them evenly to obtain a first mixed solution, and add another group of Ce-Mo 2 Metatungstic acid is added to solution C and mixed evenly to obtain a second mixed solution.

[0058] The Ce-Mo 2 The method for obtaining the C solution is as follows: 2 C is dispersed in the second dispersant, and then polyvinyl pyrrolidone is added, mixed evenly, and then subjected to ultrasonic and stirring treatment to obtain the Ce-Mo 2 C solution, wherein the second dispersant comprises anhydrous ethanol and water.

[0059] In the present invention, polyvinyl pyrrolidone plays the role of dispersion and binding.

[0060] Preferably, the powdered Ce-Mo 2 The mass volume ratio of C to the second dispersant is 1: (150-300) g / mL.

[0061] Preferably, the volume ratio of the anhydrous ethanol to water is 1:(0.1-10), and more preferably, the volume ratio of the anhydrous ethanol to water is 1:(0.5-2).

[0062] Preferably, the powdered Ce-Mo 2 The mass ratio of C to the polyvinyl pyrrolidone is 1:(1-3).

[0063] In this step, you can first press two groups of Ce-Mo 2 The amount of solution C is prepared and then divided into two groups; or the preparations are made separately directly, both methods are acceptable.

[0064] In the present invention, the method for uniformly mixing the first mixed liquid and the second mixed liquid is: stirring at room temperature for 24 hours to 36 hours.

[0065] Preferably, the tungsten element in the metatungstate and the cerium-doped molybdenum carbide (Ce-Mo) in the first mixed solution and the second mixed solution 2 C) The atomic molar ratio of the molybdenum element is 1:(0.5 to 2).

[0066] Preferably, the hydrochloric acid and Ce-Mo added to the first mixed solution 2 The volume of water added to solution C is 1:(15~20).

[0067] Step (3), performing preset treatment on the first mixed liquid and the second mixed liquid respectively to obtain a first precursor and a second precursor, wherein the preset treatment includes solid-liquid separation, washing and drying performed in sequence.

[0068] The solid-liquid separation in the preset treatment adopts centrifugal separation.

[0069] The cleaning in the preset treatment is performed by washing with deionized water and anhydrous ethanol.

[0070] The drying process conditions in the preset treatment include: a drying temperature of 80 to 120° C. and a drying time of 12 to 24 hours.

[0071] Step (4), respectively loading the first precursor and the second precursor into two magnetic boats and placing them in a tube furnace, calcining them in a nitrogen-containing atmosphere under preset calcination conditions to obtain the Ce-Mo 2 C@WO 3Catalyst, wherein the magnetic boat loaded with the first precursor is placed in front of the magnetic boat loaded with the second precursor.

[0072] In the present invention, the first precursor is used to provide a tungstic acid environment to make the thermally and chemically stable WO 3 Can be well coated on Ce-Mo 2 C surface layer, forming a core-shell Ce-Mo 2 C@WO 3 catalyst.

[0073] Preferably, the nitrogen-containing atmosphere is one of nitrogen and ammonia or a mixture of the two. More preferably, the nitrogen-containing atmosphere is nitrogen.

[0074] Preferably, the preset calcination conditions include a calcination temperature of 500-1000° C. and a calcination time of 3-6 hours. More preferably, the preset calcination conditions include a calcination temperature of 550-750° C. and a calcination time of 3-4 hours.

[0075] Preferably, the preset calcination conditions further include: a heating rate of 1 to 10° C. / min, more preferably, a heating rate of 5° C. / min.

[0076] The present invention also provides a core-shell microwave catalyst prepared by the above preparation method, represented by Ce-Mo 2 C@WO 3 catalyst.

[0077] The present invention also provides a method for catalytically decomposing hydrogen sulfide using a core-shell type microwave catalyst, the method comprising using the core-shell type microwave catalyst to directly catalyze the decomposition of hydrogen sulfide to generate hydrogen and sulfur under microwave conditions, the core-shell type catalyst comprising Ce-Mo 2 C core structure and cladding on the Ce-Mo 2 WO outside the C core structure 3 Shell structure, represented by Ce-Mo 2 C@WO 3 catalyst.

[0078] The Ce-Mo 2 C@WO 3 The preparation method of the catalyst is the same as the preparation method of the core-shell type microwave catalyst described above, and will not be repeated here.

[0079] Preferably, the reaction temperature for catalytic direct decomposition of hydrogen sulfide under microwave conditions is 400-600°C, more preferably 450-550°C.

[0080] Preferably, the microwave conditions are that the microwave frequency is 2.45 GHz, and the microwave power is 1 to 1350 W, preferably 300 to 900 W.

[0081] Preferably, H 2 The volume content of hydrogen sulfide in the S gas is 1-50 vol%, preferably 10-20 vol%.

[0082] Example 1

[0083] Core-shell catalyst Ce-Mo 2 C@WO 3 Preparation

[0084] Step 1: Powdered Ce-Mo 2 Preparation of C:

[0085] Step 1.1, weigh 6g of ammonium molybdate tetrahydrate and 12.55g of p-phenylenediamine into a beaker, add 400mL of deionized water, then add 1.48g of cerium nitrate, mix well, stir vigorously at 50°C for 2.5h, add 9.4mL of 36% hydrochloric acid during stirring. After the solution is cooled naturally, filter it, wash it with distilled water several times, and dry it in a drying oven at 80°C overnight.

[0086] Step 1.2: Place the dried sample in step 1.1 into a magnetic boat, place the magnetic boat in a tube furnace, and then introduce N 2 , the temperature was raised to 900℃ at a rate of 5℃ / min and calcined for 12h, and Ce-Mo was obtained after cooling. 2 C powder.

[0087] Step 2: Core-shell catalyst Ce-Mo 2 C@WO 3 Preparation:

[0088] Step 2.1, weigh two groups of 3g Ce-Mo 2 The C powder sample was dispersed in a mixed dispersant of 100 mL of distilled water and 100 mL of anhydrous ethanol, and then 5 g of PVP was added and mixed evenly, first ultrasonically treated for 30 min, and then stirred for 30 min. 3.0 g of metatungstic acid was added to the first group and then 6 mL of 36% hydrochloric acid was added, and 3.0 g of metatungstic acid was added to the second group. The two groups of solutions were transferred to 500 mL flasks respectively, and stirred at 30 ° C for 24 h to obtain the first mixed solution (with hydrochloric acid) and the second mixed solution (without hydrochloric acid).

[0089] Step 2.2, the first mixed liquid and the second mixed liquid are respectively subjected to preset treatment to obtain the first precursor and the second precursor, wherein the preset treatment is specifically: centrifuging at a speed of 6000 rpm, collecting the precipitate, repeatedly washing with deionized water and anhydrous ethanol for multiple times, and drying in a vacuum drying oven at 80°C overnight.

[0090] Step 2.3: Place the first precursor and the second precursor obtained in step 2.2 into two magnetic boats respectively, and then place the two magnetic boats together in a tube furnace, with the first precursor placed in front of the second precursor (close to the inlet side), and introduce N 2 The temperature was raised from room temperature to 600°C at a rate of 5°C / min, and the sample was calcined at 600°C for 3 hours to obtain a core-shell Ce-Mo 2 C@WO 3 catalyst.

[0091] Figure 1 is the Ce-Mo in Example 1 2 C@WO 3 XRD pattern of the catalyst. Figure 1 It can be seen that the catalyst has Mo 2 The diffraction peaks of C correspond to Mo 2 C(JCPDS Card No.35-0787)、CeO 2 (JCPDS Card No.43-1002), WO 3 (JCPDS Card No.41-1230), confirming that Mo 2 C, CeO 2 , WO 3 formation.

[0092] Comparative Example 1

[0093] Non-core-shell Ce-Mo 2 Preparation of C catalyst

[0094] 1. Powdered Ce-Mo 2 Preparation of C:

[0095] Step 1.1, weigh 6g of ammonium molybdate tetrahydrate and 12.55g of p-phenylenediamine into a beaker, add 400mL of deionized water, then add 1.48g of cerium nitrate, mix well, stir vigorously at 50°C for 2.5h, add 9.4mL of 36% hydrochloric acid during stirring. After the solution is cooled naturally, filter it, wash it with distilled water several times, and dry it in a drying oven at 80°C overnight.

[0096] Step 1.2: Place the dried sample in step 1.1 into a magnetic boat, place the magnetic boat in a tube furnace, and then introduce N 2 , the temperature was raised to 900℃ at a rate of 5℃ / min and calcined for 12h, and Ce-Mo was obtained after cooling. 2 C powder.

[0097] 2. Non-core-shell Ce-Mo 2 Preparation of C catalyst

[0098] Step 2.1, weigh 3g Ce-Mo 2 The C powder sample was dispersed in a mixed dispersant of 100 mL of distilled water and 100 mL of anhydrous ethanol, firstly ultrasonically treated for 30 min and then stirred for 30 min. The solution was then transferred to a 500 mL flask and stirred at 30 °C for 24 h.

[0099] Step 2.2: centrifuge the solution obtained in step 2.1 at 6000 rpm, collect the precipitate, wash it repeatedly with deionized water and anhydrous ethanol for several times, and dry it in a vacuum drying oven at 80°C.

[0100] Step 2.3: Place the dried sample in step 2.2 into a magnetic boat, place the magnetic boat in a tube furnace, and introduce N 2 The temperature was raised from room temperature to 600°C at a rate of 5°C / min, and the sample was calcined at 600°C for 3 hours to obtain a non-core-shell Ce-Mo 2 C catalyst.

[0101] Figure 2 The non-core-shell Ce-Mo in the comparative example 2 XRD pattern of C catalyst. It can be seen from the figure that the catalyst has Mo 2 The diffraction peaks of C, Mo 2 C(JCPDS Card No.35-0787)、CeO 2 (JCPDS Card No.43-1002), confirming that Ce-Mo 2 The formation of C.

[0102] Comparative Example 2

[0103] Non-core-shell Ce-Mo 2 C@WO 3 Catalyst preparation

[0104] Comparative Example 2 is the same as Example 1, except that in step 2 and step 2.1, only one group of 3g Ce-Mo 2 The C powder sample was dispersed in a mixed dispersant of 100 mL of distilled water and 100 mL of anhydrous ethanol, and then 5 g of PVP was added and mixed evenly, firstly ultrasonically treated for 30 min, then stirred for 30 min, and then tungstic acid and hydrochloric acid were added, and stirred evenly to obtain a first mixed solution; step 2.2 only centrifuged, washed and dried the first mixed solution to obtain a first precursor; step 2.3, calcined the first precursor to obtain a non-core-shell Ce-Mo 2 C@WO 3 catalyst.

[0105] Comparative Example 3

[0106] Core-shell Ce-Mo 2 C@WO 3 Preparation of Catalyst-2

[0107] Comparative Example 3 is the same as Example 1, except that step 2 is the only difference. Specifically, step 2.1 only weighs a group of 3g Ce-Mo 2 The C powder sample was dispersed in a mixed dispersant of 100 mL of distilled water and 100 mL of anhydrous ethanol, and then 5 g of PVP was added and mixed evenly, firstly ultrasonically treated for 30 min, then stirred for 30 min, and then tungstic acid was added and stirred evenly to obtain a second mixed solution; step 2.2 only the second mixed solution was centrifuged, washed and dried to obtain a second precursor; step 2.3, the second precursor was calcined to obtain a core-shell Ce-Mo 2 C@WO 3 Catalyst-2.

[0108] Comparative Example 4

[0109] Non-core-shell Mo 2 Preparation of C catalyst

[0110] Comparative Example 4 is the same as Comparative Example 2, except that cerium nitrate is not added in step 1.1, and the obtained catalyst is non-core-shell Mo 2 C catalyst.

[0111] Comparative Example 5

[0112] Core-shell catalyst Mo 2 C@WO 3

[0113] Comparative Example 5 is the same as in Example 1, except that cerium nitrate is not added in step 1.1, and the obtained catalyst is a core-shell catalyst Mo 2 C@WO 3 .

[0114] Experiment on direct decomposition of hydrogen sulfide by microwave catalysis

[0115] Example 2

[0116] The microwave catalytic reactor was purchased from Hunan Changyi Microwave Technology Co., Ltd. The microwave power ranged from 0 to 1350 W, preferably from 300 to 900 W, and the frequency was 2450 MHz.

[0117] The H 2 The S standard gas is provided by Dalian Data Gas Co., Ltd. 2 and H 2 S, where H 2 The S content is 15 vol%, and the N 2 The content is 85vol%.

[0118] Detection H 2 The gas chromatograph model is Agilent GC 7890A.

[0119] The microwave catalyst prepared in Example 1 was filled into a quartz tube reactor to form a catalyst bed. The amount of catalyst filled was 2 g and the mesh size was 20-60 mesh. H 2 S standard gas (15 vol% H 2 S+85vol%N 2 ) was used for the experiment, with a flow rate of 60 mL / min and a reaction pressure of atmospheric pressure. The microwave power was adjusted to change the reaction bed temperature of the catalyst, and the bed temperature was maintained at 450°C, 500°C, 550°C, and 600°C, respectively, to perform microwave catalytic direct decomposition of H 2 The experimental results are shown in Table 1. Table 1 shows that at different temperatures, Ce-Mo 2 C@WO 3 Conversion rate of direct decomposition of H2S over the catalyst under microwave action.

[0120] Comparative Example 6 to Comparative Example 10

[0121] Comparative Examples 6 to 10 are the same as Example 2, except that the microwave catalysts used are different. Specifically, the microwave catalyst used in Comparative Example 6 is the microwave catalyst prepared in Comparative Example 1, the microwave catalyst used in Comparative Example 7 is the microwave catalyst prepared in Comparative Example 2, the microwave catalyst used in Comparative Example 8 is the microwave catalyst prepared in Comparative Example 3, the microwave catalyst used in Comparative Example 9 is the microwave catalyst prepared in Comparative Example 4, and the microwave catalyst used in Comparative Example 10 is the microwave catalyst prepared in Comparative Example 5. The experimental results of Comparative Examples 6 to 10 are shown in Table 1.

[0122] Table 1 Conversion rate of direct decomposition of hydrogen sulfide by microwave catalysis with different catalysts at different temperatures

[0123]

[0124] Comparing the conversion rate data of Example 1 and Comparative Example 1 in Table 1, it can be seen that when the reaction temperature is in the range of 450-600°C, the conversion rate of WO 3 The activity of the coated core-shell catalysts is always higher than that of the uncoated non-core-shell catalysts.

[0125] Based on the conversion rate data of Example 1 and Comparative Examples 2 and 3 in Table 1, a comparison chart of the decomposition efficiency of the three microwave catalysts at different temperatures was drawn, as shown in FIG. Figure 3 As shown, from Figure 3 It can be seen that non-core-shell Ce-Mo 2 C@WO3 The catalyst activity is relatively good, the core-shell catalyst Ce-Mo 2 C@WO 3 -2 catalyst has higher catalytic activity than non-core-shell Ce-Mo 2 C@WO 3 catalyst, but it is also much lower than the core-shell catalyst Ce-Mo 2 C@WO 3 The reason is that the core-shell catalyst Ce-Mo 2 C@WO 3 -2 The chemical structure of the core-shell type is unstable.

[0126] From the conversion rate data of Comparative Example 4, it can be seen that below 600°C, the non-core-shell Mo 2 C catalyst under microwave irradiation 2 The conversion rate of S directly decomposed is low. Comparing the conversion rate data of Example 1 and Comparative Example 4 in Table 1, it can be seen that the non-core-shell Ce-Mo 2 C catalyst under microwave irradiation 2 The conversion rate of direct decomposition of S is lower than that of the core-shell catalyst Ce-Mo 2 C@WO 3 , the catalytic activity is relatively low. This indicates that the catalyst does not have high activity at low temperatures.

[0127] According to the conversion rate data of Example 1 and Comparative Example 4 in Table 1, the core-shell Mo 2 C@WO 3 Catalyst and core-shell Ce-Mo 2 C@WO 3 Compared with the catalyst, under the action of microwave, the core-shell Mo 2 C@WO 3 The catalyst H 2 The conversion rate of direct decomposition of S is low, and its activity at low temperature is far less than that of core-shell Ce-Mo 2 C@WO 3 Therefore, the core-shell microwave catalyst Ce-Mo 2 C@WO 3 When compared at low temperatures below 500 °C, it is a more efficient method for directly decomposing H 2 Microwave catalyst of S.

[0128] Investigation of microwave catalytic H 2 Stability of direct decomposition of S

[0129] Example 3

[0130] Basically the same as Example 2, the microwave catalyst prepared in Example 1 was filled into a quartz tube reactor to form a catalyst bed, the catalyst loading was 2 g, and the mesh size was 20-60. 2 S standard gas (15 vol% H 2 The experiment was carried out with a flow rate of 60 mL / min, a reaction pressure of atmospheric pressure, and a bed temperature of 500°C. The difference from Example 2 is that the core-shell microwave catalyst Ce-Mo 2 C@WO 3 The stability of the catalyst was investigated by the catalytic reaction time. The activity of the catalyst changed with time. Figure 4 As shown, from Figure 4 It can be seen that after the catalytic reaction time reaches 400 minutes, the conversion rate is still 80%, and it still maintains good activity without obvious deactivation, indicating that the catalyst can maintain long-term stability under the reaction atmosphere.

[0131] Example 4 is the same as Example 3, except that Example 4 examines non-core-shell Ce-Mo 2 C The activity of the catalyst. The activity of the catalyst changes with time. Figure 4 As shown, from Figure 4 It can be seen that non-core-shell Ce-Mo 2 Catalyst C deactivates faster.

[0132] Non-core-shell Ce-Mo 2 The conversion rate of C catalyst at 450℃~600℃ is only slightly lower than that of Ce-Mo core-shell microwave catalyst. 2 C@WO 3 ,but Figure 4 It can be seen that with the extension of reaction time, the non-core-shell Ce-Mo 2 The hydrogen sulfide conversion rate of C catalyst decreased significantly, that is, its stability was poor. Therefore, the thermally and chemically stable WO 3 The shell will be Ce-Mo 2 After coating with C, not only the conversion rate at a lower reaction temperature is improved, but also the reaction stability of the catalyst is greatly improved. 2 C@WO 3 It has high activity at low temperatures and can maintain high activity for a long time.

[0133] Under the condition of maintaining a high conversion rate, the lower the catalytic reaction temperature, the more energy-saving and environmentally friendly it is. Therefore, the reaction temperature of the catalytic direct decomposition of hydrogen sulfide corresponding to the catalyst of the present invention is preferably 400-700°C, more preferably 450-600°C.

[0134] Comparison of catalytic performance with microwave catalysts provided by prior art

[0135] The core-shell microwave catalyst Ce-Mo provided by the present invention 2 C@WO 3 The catalytic effects of the catalysts were compared with those of other microwave catalysts disclosed in the prior art. The results are shown in Table 2.

[0136] Table 2 Statistical table of conversion rates of direct catalytic decomposition of hydrogen sulfide by various microwave catalysts

[0137]

[0138]

[0139] Invention patent CN107803208A provides a supported microwave catalyst prepared by hydrothermal synthesis method - 10-30wt% CoS / NiS / CNT. As can be seen from Table 2, under microwave irradiation, the Ce-Mo provided in the present invention 2 C@WO 3 Core-shell microwave catalyst for H 2 The conversion rate of the S decomposition reaction is significantly higher than that of the 10% CoS / 10% NiS / CNT catalyst.

[0140] The inventor previously invented a patent CN111203259A which provides a Mo 2 C@BN catalyst, as can be seen from Table 2, Mo 2 C@BN-1000、Mo 2 The conversion rates of hydrogen sulfide of C@BN-900 and Mo2C@BN-800 catalysts are relatively low at low temperatures. 2 C@BN-900 and Mo 2 When the catalyst bed temperature of C@BN-800 is 600℃, H 2 The conversion rates of Ce-Mo in the present invention are 44.9% and 33.8% respectively. 2 C@WO 3 The hydrogen sulfide conversion rate of the catalyst at low temperature is much higher than that of the Mo 2 C@BN catalyst.

[0141] Patent CN109821564A previously invented by the inventor provides a method for preparing a coated catalyst, wherein the catalyst comprises a molybdenum-based compound core structure and a silicon dioxide shell structure coated thereon, wherein the molybdenum-based compound core structure is molybdenum nitride. The MoNx@SiO prepared by the method provided therein 2 The catalyst catalyzes the direct decomposition of hydrogen sulfide under microwave conditions. When the reaction temperature is 650℃, the corresponding H 2 The S conversion rate is 87.6%. 2C@WO 3 The catalyst has a hydrogen sulfide conversion rate of 87.61% at 500°C, and a more efficient hydrogen sulfide conversion rate is achieved at a relatively lower temperature. 2 C@WO 3 The hydrogen sulfide conversion rate of the catalyst was 87.61% at 500°C and 97.95% at 550°C, indicating that the Ce-Mo catalyst of the present invention 2 C@WO 3 The activity of the core-shell microwave catalyst at a lower reaction temperature is higher than that of the coated catalyst in the prior art.

[0142] From the comparison between the above examples and comparative examples, it can be seen that the core-shell Ce-Mo prepared by the present invention 2 C@WO 3 The conversion rate of hydrogen sulfide can reach 87.61% at 500℃, which is higher than that of Ce-Mo catalyst. 2 The conversion rate of hydrogen sulfide decomposition by C catalyst is higher than that of non-core-shell Mo 2 C catalyst, and higher than the core-shell Mo 2 C@WO 3 Catalyst. And compared with Mo prepared by programmed temperature method in the background data 2 Compared with all the catalysts in the comparative examples, Ce-Mo has much higher activity at low temperature, and their activity is also much higher than the hydrogen sulfide conversion rate under conventional reactions, indicating that these catalysts and microwaves can break the balance of hydrogen sulfide decomposition reaction, greatly improve the conversion rate of hydrogen sulfide, and achieve the purpose of efficient decomposition of hydrogen sulfide at a lower reaction temperature, thus achieving the purpose of energy saving. 2 Thermally and chemically stabilized WO 3 After the shell is coated, the stability of the reaction is greatly improved. The core-shell Ce-Mo prepared by the method described in the present invention 2 C@WO 3 The catalyst is suitable for working together with microwaves to catalyze the direct decomposition of hydrogen sulfide. It can not only achieve a high hydrogen sulfide conversion rate at low temperature and obtain high activity, but also has high stability. It can turn hydrogen sulfide into treasure and save energy.

[0143] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for catalytically decomposing hydrogen sulfide using a core-shell microwave catalyst, characterized in that: The method comprises using the core-shell microwave catalyst to directly catalyze the decomposition of hydrogen sulfide to generate hydrogen and sulfur under microwave conditions. The core-shell catalyst comprises a Ce-Mo2C core structure and a WO3 shell structure coated on the outside of the Ce-Mo2C core structure, which is represented by a Ce-Mo2C@WO3 catalyst.

2. The method for catalytically decomposing hydrogen sulfide using the core-shell microwave catalyst according to claim 1, characterized in that: The Ce-Mo2C@WO3 catalyst is prepared by the following method: Step (1), preparing powdered Ce-Mo2C by metal doping and organic-inorganic hybridization, wherein the step (1) comprises: After ammonium molybdate, p-phenylenediamine and cerium salt are mixed with a first dispersant, an amine precipitation reaction occurs at 30 to 80° C. under stirring, and a reaction solution including amine precipitation is obtained after the reaction is completed; The reaction solution including the amine precipitate is subjected to solid-liquid separation, washing, drying and calcination to obtain powdered Ce-Mo2C; Step (2), using powdered Ce-Mo2C as a raw material, preparing two groups of identical Ce-Mo2C solutions, then adding metatungstic acid and hydrochloric acid to one group of Ce-Mo2C solutions and mixing them uniformly to obtain a first mixed solution, and adding metatungstic acid to the other group of Ce-Mo2C solutions and mixing them uniformly to obtain a second mixed solution; Step (3), performing a preset treatment on the first mixed liquid and the second mixed liquid respectively to obtain a first precursor and a second precursor, wherein the preset treatment includes solid-liquid separation, washing and drying performed in sequence; Step (4), respectively loading the first precursor and the second precursor into two magnetic boats and placing them in a tube furnace, calcining them in a nitrogen-containing atmosphere under preset calcination conditions to obtain the Ce-Mo2C@WO3 catalyst, wherein the magnetic boat loaded with the first precursor is placed in front of the magnetic boat loaded with the second precursor.

3. The method for catalytically decomposing hydrogen sulfide using the core-shell microwave catalyst according to claim 2, characterized in that: The cerium salt is cerium nitrate, the mass ratio of cerium element in cerium nitrate to molybdenum element in ammonium molybdate is 1:(10-20), and the molar ratio of ammonium molybdate to p-phenylenediamine is 1:(0.5-10); the first dispersant includes hydrochloric acid and water, and the volume ratio of hydrochloric acid to water is 1:(0.1-200).

4. The method for catalytically decomposing hydrogen sulfide using the core-shell microwave catalyst according to claim 3, characterized in that: The method for preparing the Ce-Mo2C solution is as follows: dispersing the powdered Ce-Mo2C in a second dispersant, then adding polyvinyl pyrrolidone, mixing evenly, and then subjecting to ultrasonic and stirring treatment to obtain the Ce-Mo2C solution, wherein the second dispersant includes anhydrous ethanol and water, and the volume ratio of the anhydrous ethanol to water is 1: (0.1-10).

5. The method for catalytically decomposing hydrogen sulfide using the core-shell microwave catalyst according to claim 3, characterized in that: The atomic molar ratio of the tungsten element in the metatungstic acid and the molybdenum element in the cerium-doped molybdenum carbide in the first mixed solution and the second mixed solution is 1:(0.5-2).

6. The method for catalytically decomposing hydrogen sulfide using the core-shell microwave catalyst according to claim 2, characterized in that: In the step (4), the nitrogen-containing atmosphere is one of nitrogen and ammonia or a mixture of the two, and the preset calcination conditions include a calcination temperature of 500 to 1000° C. and a calcination time of 3 to 6 hours.

7. The method for catalytically decomposing hydrogen sulfide using the core-shell microwave catalyst according to any one of claims 1 to 6, characterized in that: The reaction temperature for direct decomposition of hydrogen sulfide under microwave conditions is 400~600℃.

8. A method for preparing a core-shell microwave catalyst, characterized in that: The core-shell catalyst comprises a Ce-Mo2C core structure and a WO3 shell structure coated on the outside of the Ce-Mo2C core structure, which is expressed as a Ce-Mo2C@WO3 catalyst. The preparation method comprises the following steps: Step (1), preparing powdered Ce-Mo2C by metal doping and organic-inorganic hybridization, wherein the step (1) comprises: After ammonium molybdate, p-phenylenediamine and cerium salt are mixed with a first dispersant, an amine precipitation reaction occurs at 30 to 80° C. under stirring, and a reaction solution including amine precipitation is obtained after the reaction is completed; The reaction solution including the amine precipitate is subjected to solid-liquid separation, washing, drying and calcination to obtain powdered Ce-Mo2C; Step (2), using powdered Ce-Mo2C as a raw material, preparing two groups of identical Ce-Mo2C solutions, then adding metatungstic acid and hydrochloric acid to one group of Ce-Mo2C solutions and mixing them uniformly to obtain a first mixed solution, and adding metatungstic acid to the other group of Ce-Mo2C solutions and mixing them uniformly to obtain a second mixed solution; Step (3), performing a preset treatment on the first mixed liquid and the second mixed liquid respectively to obtain a first precursor and a second precursor, wherein the preset treatment includes solid-liquid separation, washing and drying performed in sequence; Step (4), respectively loading the first precursor and the second precursor into two magnetic boats and placing them in a tube furnace, calcining them in a nitrogen-containing atmosphere under preset calcination conditions to obtain the Ce-Mo2C@WO3 catalyst, wherein the magnetic boat loaded with the first precursor is placed in front of the magnetic boat loaded with the second precursor.

9. A core-shell microwave catalyst, characterized in that: The core-shell type microwave catalyst is prepared by the preparation method described in claim 8.

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