Iron-based catalyst for eliminating toxic action of sulfur element by using calcium and sodium as well as preparation method and application of iron-based catalyst

Abstract

The invention discloses an iron-based catalyst for eliminating toxic action of sulfur element by calcium and sodium as well as a preparation method and application of the iron-based catalyst. The preparation method of the iron-based catalyst comprises the following steps: respectively preparing an aqueous solution of ferrous sulfate and a mixed aqueous solution of calcium nitrate and sodium nitrate, slowly dropwise adding the aqueous solution of ferrous sulfate into the mixed solution of calcium nitrate and sodium nitrate, magnetically stirring and reacting for a period of time under a water-bath heating condition; and cooling to room temperature, filtering, drying and crystallizing the filtrate, and then roasting and crystallizing to obtain the iron-based catalyst. According to the method, the content of the sulfur element in the catalyst is effectively reduced, the toxic action of the sulfur element on the catalyst is weakened, the prepared iron-based catalyst has the activity of catalyzing the CO2 hydrogenation reaction, the CO2 conversion rate is higher than 13%, and the C5 + hydrocarbon selectivity of the product is 55% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to an iron-based catalyst which eliminates the poisoning effect of sulfur element by using calcium and sodium, and a preparation method and application thereof. Background Art

[0002] Iron-based catalyst is a low-cost and highly active catalyst, and has a good catalytic effect on reverse water gas reaction, Fischer-Tropsch synthesis reaction, Fenton reaction, ammonia synthesis reaction, etc.

[0003] When using iron salts as raw materials to prepare iron-based catalysts, ferric nitrate is a commonly used raw material, while ferrous sulfate is rarely used because it contains sulfur, a recognized catalyst poison. Sulfur can not only inhibit the reduction of the catalyst, but also react with the active center of the catalyst, changing the surface structure and chemical properties of the catalyst, resulting in a decrease in catalyst activity or even direct deactivation. However, some studies have shown that a small amount of sulfur can have a positive effect on the catalyst, such as improving the reaction activity, stability, and selectivity of the catalyst.

[0004] Ferrous sulfate is cheap, with a selling price far lower than that of ferric nitrate, but the sulfur element in it is toxic to catalysts. If most of the sulfur element can be removed through certain technical means, it will not only greatly reduce the preparation cost and use cost of the catalyst, but also enable a small amount of sulfur to have a positive enhancing effect on the catalyst.

[0005] Chinese patent CN112354540A discloses a method for preparing an iron-based catalyst using ferrous sulfate as a raw material, using oxalic acid as a precipitant, and after centrifugal separation, adding monosaccharides to the precipitate to reduce the residual sulfur element, making it easier to remove. Chinese patent CN 113318744 A discloses a method for preparing an iron-based catalyst with high carbon hydrocarbon selectivity, specifically stirring ferrous sulfate with oxalic acid and potassium sodium tartrate at the same time, washing the separated precipitate with deionized water 3 times, and the purpose of multiple washings and centrifugal separation is to remove free sulfur species from the precipitate. Chinese patent CN116237047A discloses an iron-based catalyst and a preparation method thereof that uses CO2-assisted washing to eliminate the poisoning effect of sulfur element, specifically using ammonium carbonate as a precipitant to precipitate iron ions in ferrous sulfate, and then eliminating the residual sulfur element by passing CO2 for washing.

[0006] The above catalyst preparation methods all firstly precipitate ferrous ions by a precipitant to remove most of sulfate ions, and then use a reducing agent or repeatedly wash to remove the remaining sulfur element, which inevitably produces a large amount of waste water, and it is necessary to develop a new preparation method. The present invention uses calcium nitrate to remove the sulfur element in the catalyst raw material, and introduces calcium and sodium to weaken the adverse effects of the residual sulfur element in the catalyst, providing a new method for preparing an iron-based catalyst using ferrous sulfate as a raw material. Summary of the invention

[0007] In view of the above problems, the present invention provides an iron-based catalyst that uses calcium and sodium to eliminate the poisoning effect of sulfur, and a preparation method and application thereof, which can effectively solve the problem of sulfur poisoning the catalyst and generating a large amount of wastewater during the catalyst preparation process.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing an iron-based catalyst that eliminates the poisoning effect of sulfur by using calcium and sodium comprises the following process steps: S1. Dissolve ferrous sulfate in deionized water to obtain solution A; S2, dissolving calcium nitrate and sodium nitrate together in deionized water to obtain solution B, and then slowly dropping solution A into solution B; S3, reacting with magnetic stirring under heating in a water bath, and cooling to room temperature after the reaction is completed; S4, filtering and separating the solid and the liquid, drying the filtrate, crystallizing, and then calcining the dried crystals to obtain an iron-based catalyst.

[0009] Furthermore, the mass ratio of ferrous sulfate to calcium nitrate is 1:1.08-1.35.

[0010] Furthermore, the mass ratio of ferrous sulfate to sodium nitrate is 1:0.015-0.125.

[0011] Furthermore, the mass ratio of ferrous sulfate to deionized water is 1:4.0-6.0; the mass ratio of the mixture of calcium nitrate and sodium nitrate to deionized water is 1:4.0-5.5.

[0012] Furthermore, the reaction temperature of the water bath magnetic stirring is 40-70°C and the reaction time is 30-60 min.

[0013] Furthermore, the drying temperature is 80-140°C, and the drying time is 18-24 hours.

[0014] Furthermore, the calcination temperature is 650-800°C, and the calcination time is 5-8 h.

[0015] The present invention also provides an iron-based catalyst which uses calcium and sodium to eliminate the poisoning effect of sulfur element, and is prepared by the preparation method as described above.

[0016] The present invention also proposes an application of the iron-based catalyst as described above in which calcium and sodium are used to eliminate the poisoning effect of sulfur in the CO2 hydrogenation reaction to produce hydrocarbons. The iron-based catalyst has the activity of catalyzing the CO2 hydrogenation reaction, the CO2 conversion rate is higher than 13%, and the product C5 + The hydrocarbon selectivity is above 55%.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) By adding calcium nitrate to ferrous sulfate and filtering it, most of the sulfate ions in the iron source are removed, and the remaining sulfate ions exist in the catalyst in the form of calcium sulfate, which reduces the toxic effect of sulfur on the iron-based catalyst. At the same time, sodium is introduced into the catalyst. The electronic synergy of sulfur and sodium further weakens the effect of residual sulfur on the catalyst performance, so that the iron-based catalyst prepared with ferrous sulfate as raw material has the activity of catalyzing CO2 hydrogenation. In addition, no washing is required during the preparation process, no wastewater is generated, and the filtered and separated calcium sulfate can also be recycled.

[0018] (2) The technical solution of the present invention effectively reduces the content of sulfur in the catalyst and weakens its poisoning effect on the catalyst. The iron-based catalyst prepared has the activity of catalyzing CO2 hydrogenation reaction, the CO2 conversion rate is higher than 13%, and the product C5 + The hydrocarbon selectivity is above 55%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a graph showing the H2-TPR results of the catalysts prepared in the examples and comparative examples of the present invention. DETAILED DESCRIPTION

[0020] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. Example 1

[0021] (1) First weigh 14.00 g of ferrous sulfate heptahydrate into a 250 ml beaker, add 40.00 g of deionized water and stir to dissolve. Separately weigh 14.00 g of calcium nitrate tetrahydrate and 0.26 g of sodium nitrate and mix and dissolve in 40.00 g of deionized water.

[0022] (2) The ferrous sulfate solution was slowly added dropwise to the mixed solution of calcium nitrate and sodium nitrate, heated in a water bath at 60°C with magnetic stirring for 40 min, cooled to room temperature and filtered, the filtrate was dried at 120°C for 20 h, and the obtained solid was calcined in a muffle furnace at 750°C for 6 h, and then the catalyst was pressed into tablets. Example 2

[0023] (1) First weigh 14.00 g of ferrous sulfate heptahydrate into a 250 ml beaker, add 40.00 g of deionized water and stir to dissolve. Separately weigh 12.00 g of calcium nitrate tetrahydrate and 0.26 g of sodium nitrate and mix and dissolve in 40.00 g of deionized water.

[0024] (2) The ferrous sulfate solution was slowly added dropwise to the mixed solution of calcium nitrate and sodium nitrate, heated in a water bath at 60°C with magnetic stirring for 40 min, cooled to room temperature and filtered, the filtrate was dried at 120°C for 20 h, and the obtained solid was calcined in a muffle furnace at 750°C for 6 h, and then the catalyst was pressed into tablets. Example 3

[0025] (1) First weigh 14.00 g of ferrous sulfate heptahydrate into a 250 ml beaker, add 40.00 g of deionized water and stir to dissolve. Separately weigh 14.00 g of calcium nitrate tetrahydrate and 0.78 g of sodium nitrate and mix and dissolve them in 40.00 g of deionized water.

[0026] (2) The ferrous sulfate solution was slowly added dropwise to the mixed solution of calcium nitrate and sodium nitrate, heated in a water bath at 60°C with magnetic stirring for 40 min, cooled to room temperature and filtered, the filtrate was dried at 120°C for 20 h, and the obtained solid was calcined in a muffle furnace at 750°C for 6 h, and then the catalyst was pressed into tablets. Comparative Example 1

[0027] (1) First weigh 14.00 g of ferrous sulfate heptahydrate into a 250 ml beaker, add 40.00 g of deionized water and stir to dissolve. Separately weigh 14.00 g of calcium nitrate tetrahydrate and dissolve it in 40.00 g of deionized water.

[0028] (2) The ferrous sulfate solution was slowly added dropwise to the calcium nitrate solution, heated in a water bath at 60°C with magnetic stirring for 40 min, cooled to room temperature and filtered, the filtrate was dried at 120°C for 20 h, and the obtained solid was calcined in a muffle furnace at 750°C for 6 h, and then the catalyst was pressed into tablets. Comparative Example 2

[0029] Weigh 14.00 g of ferrous sulfate heptahydrate into a 250 ml beaker, add 40.00 g of deionized water and stir to dissolve, heat in a 60°C water bath and stir with a magnetic stirrer for 40 min, cool to room temperature and dry at 120°C for 20 h, calcine the obtained solid at 750°C in a muffle furnace for 6 h, and then press the catalyst into tablets.

[0030] The difference between Comparative Example 1 and Examples 1, 2, and 3 is that no sodium nitrate is added to Comparative Example 1.

[0031] The iron-calcium mass ratios of Examples 1 and 3 are the same, but the iron-sodium mass ratios are different.

[0032] The iron-calcium mass ratios of Examples 1 and 2 are different, but the iron-sodium mass ratios are the same.

[0033] In Comparative Example 2, no calcium and sodium were added.

[0034] The above catalysts were all tested for CO2 hydrogenation reaction performance under the same reaction conditions. The specific reaction conditions were: the catalyst was reduced at a space velocity of 3000 mL / (h·g-cat.), CO / N2=3:1, normal pressure and 300°C for 6 h; then reacted in a mixed gas of H2 / CO2 / N2 of 69 / 23 / 8, 1.6 MPa, 235°C and a space velocity of 6000 mL / (h·g-cat.) for 24 h. The activity and selectivity of the catalyst for the reaction of CO2 and H2 are shown in Table 1.

[0035] Table 1 Catalyst CO2 hydrogenation reaction performance

[0036] The experimental results show that: Comparative Example 2 without adding calcium and sodium ions has no catalytic activity; Comparative Example 1 shows that calcium nitrate can be used to remove most of the sulfate ions in ferrous sulfate, so that the catalyst has higher activity; Examples 1, 2 and 3 show that adding sodium ions further improves the reaction activity of the catalyst.

[0037] Figure 1 The H2-TPR result diagram of the catalyst prepared in the embodiment and the comparative example of the present invention is as follows: the temperature is first raised from room temperature to 430°C at a rate of 10°C / min, and then reduced at a constant temperature of 430°C for 2 hours; Figure 1 It can be seen that the reduction peak temperature of comparative example 1 containing only calcium is the lowest, the reduction peak temperature of comparative example 2 without adding calcium and sodium is the highest, and the reduction peak temperatures of examples 1, 2 and 3 are between the two comparative examples, indicating that the simultaneous addition of calcium and sodium has a harmonizing effect on the reduction ability of the catalyst.

[0038] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing an iron-based catalyst that eliminates the poisoning effect of sulfur by using calcium and sodium, characterized in that: The process steps include: S1. Dissolve ferrous sulfate in deionized water to obtain solution A; S2, dissolving calcium nitrate and sodium nitrate together in deionized water to obtain solution B, and then slowly dropping solution A into solution B; S3, reacting with magnetic stirring under heating in a water bath, and cooling to room temperature after the reaction is completed; S4, filtering and separating the solid and the liquid, drying the filtrate, crystallizing, and then calcining the dried crystals to obtain an iron-based catalyst.

2. The method for preparing an iron-based catalyst for eliminating the poisoning effect of sulfur element by using calcium and sodium according to claim 1, characterized in that: The mass ratio of ferrous sulfate to calcium nitrate is 1:1.08-1.

35.

3. The method for preparing an iron-based catalyst for eliminating the poisoning effect of sulfur by using calcium and sodium according to claim 1, characterized in that: The mass ratio of ferrous sulfate to sodium nitrate is 1:0.015-0.

125.

4. The method for preparing an iron-based catalyst for eliminating the poisoning effect of sulfur element by using calcium and sodium according to claim 1, characterized in that: The mass ratio of ferrous sulfate to deionized water is 1:4.0-6.0; the mass ratio of the mixture of calcium nitrate and sodium nitrate to deionized water is 1:4.0-5.

5.

5. The method for preparing an iron-based catalyst for eliminating the poisoning effect of sulfur by calcium and sodium according to claim 1, characterized in that: The reaction temperature is 40-70°C and the reaction time is 30-60 min under water bath magnetic stirring.

6. The method for preparing an iron-based catalyst for eliminating the poisoning effect of sulfur by calcium and sodium according to claim 1, characterized in that: The drying temperature is 80-140°C and the drying time is 18-24 hours.

7. The method for preparing an iron-based catalyst for eliminating the poisoning effect of sulfur by calcium and sodium according to claim 1, characterized in that: The calcination temperature is 650-800℃ and the calcination time is 5-8 h.

8. An iron-based catalyst that uses calcium and sodium to eliminate the poisoning effect of sulfur, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. Use of the iron-based catalyst as claimed in claim 8 in which calcium and sodium are used to eliminate the poisoning effect of sulfur in the CO2 hydrogenation reaction to produce hydrocarbons, characterized in that: The CO2 conversion rate is higher than 13%, and the product C5 + The hydrocarbon selectivity is above 55%.

10. The use of an iron-based catalyst that eliminates the poisoning effect of sulfur with calcium and sodium in the CO2 hydrogenation reaction according to claim 9, characterized in that: The specific reaction conditions are as follows: the catalyst was reduced at a space velocity of 3000 mL / (h·g-cat.), CO / N2=3:1, normal pressure and 300°C for 6 h; and then reacted in a mixed gas of H2 / CO2 / N2 of 69 / 23 / 8, at 1.6 MPa, 235°C and a space velocity of 6000 mL / (h·g-cat.) for 24 h.

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