A process for the preparation of a sulfur tolerant shift catalyst

Abstract

The application relates to a preparation method of a sulfur-tolerant shift catalyst, and belongs to the technical field of sulfur-tolerant shift catalyst preparation. The H2S content in the crude synthetic gas of a coal gasification device is generally low, and in the running process, the catalyst activity is reduced due to the low H2S content, leading to the situation that the CO at the shift outlet is over the standard. The application comprises the following steps: preparing SBA-16 molecular sieves containing sulfur, a solution of a cobalt salt and a molybdenum salt, impregnating the obtained SBA-16 molecular sieves, and calcining the obtained sulfur-tolerant shift catalyst in an inert gas environment; wherein the step of preparing the SBA-16 molecular sieves containing sulfur comprises the following steps: dissolving an aluminum source in a template solution, adjusting the pH to 2-4, adding an S precursor aqueous solution, adding a silicon source in the stirring process, uniformly stirring, and then performing a crystallization reaction at 80-120 DEG C, filtering, and calcining the obtained solid to obtain SBA-16 molecular sieves containing S. The sulfur-tolerant shift catalyst has high stability and catalyst service life under the harsh working condition of low sulfur content.

Description

Technical Field

[0001] A method for preparing a sulfur-resistant shift catalyst belongs to the field of preparation technology of sulfur-resistant shift catalysts resistant to low sulfur. Background Technology

[0002] Carbon monoxide shift conversion (CO conversion) technology and catalysts are mainly used in industrial production such as hydrogen production, methanol synthesis, ammonia synthesis, gasoline synthesis, and city gas production. Due to the shortage and rising price of crude oil, high-sulfur substances such as coal, residual oil, and petroleum coke have gradually attracted attention as alternative feedstocks for light hydrocarbons. Furthermore, the development and advancement of residual oil and coal gasification processes, especially the large-scale industrial application of pressurized coal-water slurry gasification technology, have further promoted the research and development of sulfur-resistant shift catalysts. Since the 1960s, cobalt-molybdenum based sulfur-resistant shift catalysts have been widely used due to their wide temperature range, sulfur resistance, and high activity in the CO conversion reaction.

[0003] Cobalt-molybdenum (CMO)-based sulfur-resistant shift catalysts require their active components to transform from an oxidized state to a sulfide state to exhibit shift activity. Furthermore, the active component, Co-Mo sulfide, in CMO-based shift catalysts requires a certain concentration of H2S to maintain its activity. However, our understanding of the sulfide structure of CMO-based catalysts, especially the structure of the active center, is still insufficient. In practical applications, when the H2S concentration is below a certain equilibrium concentration, the active component sulfide is prone to react with water molecules to form oxides, i.e., desulfurization occurs, thus affecting the activity and activity stability of the catalyst.

[0004] In recent years, with the clean development and utilization of coal resources, the H2S content in the crude syngas of coal gasification units has generally been low, with many units as low as below 0.1%. During operation, the low H2S content has led to a decrease in catalyst activity, resulting in excessive CO at the conversion outlet, which is particularly prominent in coal gasification processes with high pressure, high CO content, and high water-to-gas ratio (1.0~1.5). Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a sulfur-resistant shift catalyst that can still maintain high catalytic activity when the feed gas has a low sulfur content.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a method for preparing a sulfur-resistant shift catalyst, characterized by the following steps: preparing a sulfur-containing SBA-16 molecular sieve, obtaining an SBA-16 molecular sieve by impregnation with a solution of cobalt salt and molybdenum salt, and obtaining a sulfur-resistant shift catalyst by calcination under an inert gas environment.

[0007] The steps for preparing sulfur-containing SBA-16 molecular sieves include: dissolving an aluminum source in a template agent solution, adjusting the pH to 2-4, adding an aqueous solution of sulfur precursor, adding a silicon source during stirring, stirring until homogeneous, crystallizing at 80-120°C, filtering, and calcining the resulting solid to obtain sulfur-containing SBA-16 molecular sieves.

[0008] In the above steps for preparing sulfur-containing SBA-16 molecular sieves, the pH is 6-6.5 after adding the S precursor aqueous solution.

[0009] The preferred method for adding the silicon source is slow dripping, which can effectively prevent silicon precipitation.

[0010] More preferably, the solution of cobalt salt and molybdenum salt uses ammonia water as solvent, and the volume ratio of the cobalt salt and molybdenum salt solution to the sulfur-containing SBA-16 molecular sieve is 1:1~1.5.

[0011] More preferably, the impregnation is performed at room temperature for 7 to 9 hours.

[0012] A modified hydrothermal crystallization method was employed to fix sulfur elements within the molecular sieve channels, on the framework, or on the silica surface, replacing some oxygen atoms and forming a weak bond with the SBA-16 molecular sieve. Then, cobalt and molybdenum were loaded as active components, which not only improved the dispersion of the active components but also fully utilized the advantages of the molecular sieve catalyst. Simultaneously, sulfur self-sufficiency was achieved, enhancing the low-sulfur resistance of the cobalt-molybdenum-based sulfur-resistant shift catalyst during the reaction process, further improving the catalyst's activity and stability under low-sulfur conditions. The resulting Co-Mo-S active phase addresses the problem of low activity in sulfur-resistant shift catalysts under low-sulfur conditions. After sulfidation, the sulfur-resistant shift catalyst prepared by this sulfur-modified molecular sieve exhibits increased content of active components on the catalyst surface, which are uniformly dispersed on the support surface. The sulfides remain stable, and during actual shift reactions, the catalyst maintains high activity and stability even when the H2S content in the reactant gas fluctuates.

[0013] Preferably, the aluminum source is one of boehmite, aluminum colloid, and aluminum nitrate. The aluminum source is converted into alumina in the sulfur-resistant shift catalyst, and the weight content of alumina in the final sulfur-resistant shift catalyst is 50-70%.

[0014] Preferably, the template agent solution is a solution obtained by dissolving one or a mixture of two of F127 and P123 in any proportion in water, and the weight ratio of template agent to water in the template agent solution is 1:20~30; the amount of template agent used is 2~5% of the weight of the sulfur-resistant conversion catalyst.

[0015] Preferably, the S precursor aqueous solution is one of thiourea, ammonium sulfide, thioacetamide, sodium thiosulfate and dodecanethiol, and the amount of sulfur used, calculated as S element, is 3 to 6% of the weight of the sulfur-resistant conversion catalyst.

[0016] If the sulfur content is too low, it will not meet the required amount of sulfidated catalyst. If it is too high, it will affect the catalyst strength and pore structure.

[0017] Preferably, the silicon source is one of TEOS, TEMS and sodium silicate, and the silicon source is converted into silicon dioxide in the sulfur-resistant conversion catalyst, wherein the weight content of silicon dioxide in the sulfur-resistant conversion catalyst is 10-25%.

[0018] Preferably, the filter residue is washed until the pH is neutral before filtration.

[0019] Preferably, the calcination before obtaining the SBA-16 molecular sieve containing S is as follows: under a nitrogen mixed gas containing 10% hydrogen, the temperature is raised from 30°C to 550°C for 400 min, including a constant temperature of 120°C for 30 min, a constant temperature of 250°C for 1 h, and a constant temperature of 550°C for 2 h, with the remaining time being the heating time.

[0020] Compared to other molecular sieves, the pore structure of SBA-16 is more conducive to the formation of CoMo active centers with specific crystal sizes, making it easier to sulfide, resulting in a relatively high sulfide content, and also making it easier to stabilize the catalyst.

[0021] Preferably, the calcination process for obtaining the sulfur-resistant conversion catalyst is as follows: drying at 50~100℃ for 20~30h, followed by calcination at 30℃ to 420℃ for 5h, including 1h at 220℃ and 2h at 420℃, with the remaining time being the heating time.

[0022] All of the above-mentioned optimal conditions are for obtaining better sulfur loading results and ensuring the sulfur loading amount and load stability.

[0023] Preferably, the cobalt salt is cobalt nitrate or cobalt oxalate, and the cobalt nitrate is converted into CoO in the sulfur-resistant shift catalyst, with the CoO content being 1 to 4% of the total weight of the sulfur-resistant shift catalyst.

[0024] Preferably, the molybdenum salt is ammonium molybdate, in which molybdenum is converted into MoO3 in the sulfur-resistant shift catalyst, and the MoO3 content is 7-12% of the total weight of the sulfur-resistant shift catalyst.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: A modified hydrothermal crystallization method is used to fix sulfur elements in the molecular sieve channels, framework, or silica surface by replacing some oxygen atoms, forming a weak bond with the SBA-16 molecular sieve. Then, cobalt and molybdenum are loaded as active components, which not only improves the dispersion of the active components but also fully utilizes the advantages of the molecular sieve catalyst. Simultaneously, sulfur is "self-sufficient," enhancing the low-sulfur resistance of the cobalt-molybdenum based sulfur-resistant shift catalyst during the reaction process, further improving the catalyst's activity and stability under low-sulfur conditions. The formed Co-Mo-S active phase solves the problem of low activity in sulfur-resistant shift catalysts under low-sulfur conditions. After sulfidation, the sulfur-resistant shift catalyst prepared by this sulfur-modified molecular sieve exhibits increased content of active components on the catalyst surface, which are uniformly dispersed on the support surface. The sulfides are stably present, and during the actual shift reaction, the catalyst can maintain high activity and stability even when the H2S content in the reaction gas fluctuates.

[0026] The method for preparing the low-sulfur resistant and sulfur-resistant shift catalyst of the present invention is easy to operate, and the catalyst is used in sulfur-resistant shift reactions. This results in high stability and long catalyst lifetime under harsh low-sulfur content conditions. Simultaneously, the catalyst has a high specific surface area, increased exposure of active sites, high dispersion of active components, and significantly increased catalytic activity. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments, wherein Embodiment 1 is the preferred embodiment of the present invention.

[0028] In Examples 1-6, the selection of template agents and sulfur precursors, and the amounts of sulfur precursors, cobalt salts, molybdenum salts, silicon sources, and aluminum sources are shown in Table 1 below. Specifically, all sulfur precursors are incorporated into the sulfur-resistant shift catalyst, and the amount of sulfur precursor is expressed as the weight percentage of sulfur in the final sulfur-resistant shift catalyst. All silicon sources are converted to silicon dioxide in the sulfur-resistant shift catalyst, and the amount of silicon source is expressed as the weight percentage of silicon dioxide in the sulfur-resistant shift catalyst. All aluminum sources are converted to aluminum oxide in the sulfur-resistant shift catalyst, and the amount of aluminum source is expressed as the weight percentage of alumina in the sulfur-resistant shift catalyst. All molybdenum salts are converted to MoO3 in the sulfur-resistant shift catalyst, and the amount of molybdenum salt is expressed as the weight percentage of MoO3 in the sulfur-resistant shift catalyst. All cobalt salts are converted to CoO in the sulfur-resistant shift catalyst, and the amount of cobalt salt is expressed as the weight percentage of CoO in the sulfur-resistant shift catalyst. In Example 4, the template agent is a mixture of F127 and P123 at a weight ratio of 1:1.

[0029] Table 1 Raw materials for the examples

[0030] .

[0031] Examples 1-4

[0032] A method for preparing a sulfur-resistant shift catalyst, comprising the following steps:

[0033] 1) Dissolve 4g of template agent in 96 mL of deionized water, stir well, and pour into a three-necked flask. Add aluminum oxide to the three-necked flask, add 60g of hydrochloric acid, and adjust the pH to 3.0.

[0034] 2) Add the sulfur precursor aqueous solution dropwise, stir thoroughly, and the pH value is 6.0~6.5;

[0035] 3) Weigh TEOS and pour it into a constant pressure funnel. Slowly add the solution dropwise into a three-necked flask while stirring constantly until homogeneous. Pour the solution into a reaction vessel and carry out a crystallization reaction at 80-120℃ for 24 hours.

[0036] 4) The material obtained from the reactor was filtered and washed until the pH was neutral, dried, and calcined with a nitrogen mixture containing 10% H2 for 400 min. The calcination process was as follows: the temperature was programmed to rise from 30℃ to 550℃, with a constant temperature of 120℃ for 30 min, a constant temperature of 250℃ for 1 h, a constant temperature of 550℃ for 2 h, and the remaining time was a constant temperature rise. After cooling to room temperature, SBA-16 molecular sieve containing S was obtained.

[0037] 5) Molybdenum nitrate and cobalt oxalate are dissolved in ammonia water to prepare a cobalt-molybdenum solution. The amount of cobalt-molybdenum solution is the same as the water absorption capacity of SBA-16 molecular sieve containing sulfur. The volume ratio of cobalt-molybdenum solution to SBA-16 molecular sieve containing sulfur is 1:1~1.5. The cobalt-molybdenum solution is poured into the prepared SBA-16 molecular sieve and mixed. It is then impregnated at room temperature for 8 hours until the cobalt-molybdenum solution is completely absorbed.

[0038] 6) Place it in an 80℃ drying oven for 24 hours and calcine it with an inert gas for 5 hours. The calcine process is as follows: the temperature is programmed to rise from 30℃ to 420℃, with a constant temperature of 220℃ for 1 hour and a constant temperature of 420℃ for 2 hours. Then cool it to room temperature to obtain CoMo / S-SBA-16, which is a sulfur-resistant conversion catalyst.

[0039] Example 5

[0040] A method for preparing a sulfur-resistant shift catalyst, based on the preparation method of Example 1, wherein step 4) involves calcining with a nitrogen mixture containing 10% H2 for 400 min. The calcination process is as follows: the temperature is programmed to rise from 30°C to 250°C, held at that temperature for 1 h, and then raised to 550°C and held at that temperature for 2.5 h. The remaining time is a uniform heating process.

[0041] Other conditions are the same as in Example 1.

[0042] Example 6

[0043] A method for preparing a sulfur-resistant shift catalyst, based on the preparation method of Example 1, wherein step 6) involves calcining with an inert gas for 5 hours. The calcination process is as follows: programmed temperature increase from 30°C to 420°C, wherein the temperature is kept constant at 420°C for 2 hours, and the remaining time is a uniform temperature increase process.

[0044] Other conditions are the same as in Example 1.

[0045] Comparative Example 1

[0046] A method for preparing a sulfur-resistant shift catalyst, based on Example 1, omits steps 2) and 4) to obtain SBA-16 molecular sieves free of sulfur. The obtained SBA-16 molecular sieves are heated to 200°C and subjected to a sulfidation reaction under a sulfidation gas atmosphere. The sulfidation gas consists of 0.8 vol% hydrogen sulfide and the remainder hydrogen, with the sulfidation gas pressure at 18 MPa throughout the process. The sulfidation process involves heating to 230°C at a rate of 8°C / h and holding at that temperature for 3 hours; then further heating to 360°C and holding at that temperature for 2 hours to complete the sulfidation.

[0047] The other processes are the same as in Example 1, and the final product is CoMo / S-SBA-16, which is a sulfur-resistant shift catalyst.

[0048] Comparative Example 2

[0049] A method for preparing a sulfur-resistant shift catalyst, based on Example 1, omitting steps 2) and 6) to obtain the CoMo / SBA-16 sulfur-resistant shift catalyst. The sulfidation conditions for this oxidized catalyst are: temperature 250℃, pressure 2.0 MPa, dry gas space velocity 2000 h⁻¹, water-to-gas ratio 1.0 (v / v), H₂S concentration 0.2%–0.5% (v / v), and sulfidation time 20 h.

[0050] The other processes are the same as in Example 1.

[0051] Performance testing

[0052] The pressurized activity evaluation device in the prior art is used to simulate industrial conditions. Gasified water and feed gas enter the reactor through a mixer. Temperature, pressure, water-to-gas ratio, and space velocity are controlled under industrial conditions. After the shift reaction, the gas passes through a condenser and separator before entering a gas chromatograph for analysis. Comparing the shift activity and stability of the sulfur-resistant shift catalysts obtained in the above examples and comparative examples, a certain amount of water is added according to different water-to-gas ratio requirements. After high-temperature gasification, it enters the reaction tube together with the feed gas for a water-gas shift reaction. The tail gas after the reaction is analyzed by chromatography.

[0053] Catalyst loading: 5 mL;

[0054] Sulfurization conditions for sulfur-resistant shift catalysts:

[0055] Pressure: 2.0 MPa; Dry gas hourly velocity: 1000 h⁻¹ -1 H2S content: 0.2%~0.3%; 250℃ is kept constant for 10 hours, then the temperature is raised to 300℃ and kept constant for 5 hours, then raised to 350℃ and kept constant for 5 hours, with a heating rate of 50℃ / h.

[0056] Evaluation conditions for sulfur-resistant shift catalysts under pressure:

[0057] Evaluation of feed gas composition: CO content: 50.0%; H2S content: 0.02%~0.05%; balance: H2; inlet temperature: 280℃; pressure: 4.0MPa; water / gas ratio: 1.0; dry gas hourly space velocity: 3000h. -1 Time: 20 hours.

[0058] The performance test results are shown in Table 2 below.

[0059] Table 2 Performance Test Results

[0060] .

[0061] A comparison of the performance test results of Examples 5 and 6 with that of Example 1 shows that, under specific heating conditions, the catalytic performance of the CoMo / S-SBA-16 sulfur-resistant shift catalyst can be further improved. Based on the performance comparison results of Comparative Examples 1 and 2 with that of Example 1, the CoMo / S-SBA-16 sulfur-resistant shift catalyst prepared by the method described in this invention exhibits high catalytic activity during the carbon monoxide shift reaction, and maintains its catalytic activity even with low hydrogen sulfide content.

[0062] The catalyst prepared in Example 1 was subjected to a lifetime performance test for 200 hours. The specific changes are shown in Table 3 below.

[0063] Table 3 Lifetime Test

[0064] .

[0065] Sulfidation was carried out under the conditions described above, and the feed gas (H2S volume 0.02%) was evaluated after sulfidation. For the first 100 hours, under the evaluation conditions described above, sulfidation and evaluation were performed, and the catalyst activity was good, with CO conversion maintained at 90%. From 100 to 120 hours, with other conditions unchanged, feed gas without hydrogen sulfide was introduced, and the activity was found to decrease only slightly. From 120 to 180 hours, with other conditions unchanged, the original feed gas containing hydrogen sulfide was reintroduced, and the activity recovered. From 180 to 200 hours, with the feed gas weight unchanged, a destructive test was conducted under different experimental conditions (inlet temperature: 400℃; pressure: 4.0MPa; water / gas ratio: 1.5; dry gas space velocity: 4000h).-1 (Time: 20h) The activity only decreased slightly.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a sulfur-resistant shift catalyst, characterized in that: Includes the following steps: SBA-16 molecular sieve containing sulfur was prepared by impregnation of SBA-16 molecular sieve with cobalt and molybdenum salts and calcination under an inert gas environment to obtain sulfur-resistant conversion catalyst. The steps for preparing sulfur-containing SBA-16 molecular sieves include: dissolving an aluminum source in a template agent solution, adjusting the pH to 2-4, adding an aqueous solution of the sulfur precursor, adding a silicon source during stirring, stirring evenly, crystallizing at 80-120°C, filtering, and calcining the resulting solid to obtain an SBA-16 molecular sieve containing sulfur. The calcination process before obtaining SBA-16 molecular sieve containing S is as follows: under a nitrogen mixed gas containing 10% hydrogen, the temperature is increased from 30℃ to 550℃ for 400 minutes, including 30 minutes at 120℃, 1 hour at 250℃, and 2 hours at 550℃, with the remaining time being the heating time.

2. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The aluminum source is one of boehmite, aluminum gel and aluminum nitrate. The aluminum source is converted into alumina in the sulfur-resistant shift catalyst. The weight content of alumina in the final sulfur-resistant shift catalyst is 50-70%.

3. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The template agent solution is a solution obtained by dissolving one or a mixture of two of F127 and P123 in any proportion in water. The weight ratio of template agent to water in the template agent solution is 1:20~30. The amount of template agent used is 2~5% of the weight of the sulfur-resistant conversion catalyst.

4. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The S precursor aqueous solution is one of thiourea, ammonium sulfide, thioacetamide, sodium thiosulfate and dodecanethiol. The amount of sulfur used, calculated as S element, is 3 to 6% of the weight of the sulfur-resistant conversion catalyst.

5. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The silicon source is one of TEOS, TEMS and sodium silicate. The silicon source is converted into silicon dioxide in the sulfur-resistant conversion catalyst. The weight content of silicon dioxide in the sulfur-resistant conversion catalyst is 10-25%.

6. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The filter residue is washed until the pH is neutral before filtration.

7. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The calcination process for obtaining the sulfur-resistant conversion catalyst is as follows: after drying at 50~100℃ for 20~30h, the temperature is increased from 30℃ to 420℃ for 5h, including 1h at 220℃ and 2h at 420℃, with the remaining time being the heating time.

8. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The cobalt salt is cobalt nitrate or cobalt oxalate. Cobalt nitrate is converted into CoO in the sulfur-resistant shift catalyst, and the CoO content is 1 to 4% of the total weight of the sulfur-resistant shift catalyst.

9. The method for preparing the sulfur-resistant shift catalyst according to claim 1, characterized in that: The molybdenum salt is ammonium molybdate, in which molybdenum is converted into MoO3 in the sulfur-resistant shift catalyst, and the content of MoO3 is 7-12% of the total weight of the sulfur-resistant shift catalyst.