An iron-based catalyst using CO2-assisted washing to eliminate sulfur poisoning, and its preparation method and application

Abstract

The present invention discloses an iron-based catalyst that utilizes CO2-assisted washing to eliminate the poisoning effect of sulfur element, as well as its preparation method and application. The preparation method of the iron-based catalyst of the present invention is: when washing the precipitate obtained from the reaction of ferrous sulfate and ammonium carbonate, CO2 gas is introduced while stirring, and the washed precipitate is separated by centrifugation or suction filtration; then the solid is obtained by drying and roasting. When other preparation parameters remain the same, the catalyst that has not been washed with CO2 assistance is used as a reference. The reaction performance of the catalyst obtained by CO2-assisted washing is not only higher than that of the reference catalyst with the same number of washing times, but also higher than that of the reference catalyst with more washing times. The measured reaction data show that the catalyst preparation method disclosed in the present invention effectively eliminates the poisoning effect of the S element in the raw material ferrous sulfate, which not only reduces the raw material cost of the iron-based catalyst, but also reduces the amount of washing wastewater generated.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and relates to an iron-based catalyst which utilizes CO2-assisted washing to eliminate the poisoning effect of sulfur element, as well as a preparation method and application thereof. Background Art

[0002] Iron-based catalysts are commonly used (Chinese invention patent CN 112354540 A), for example, in Fischer-Tropsch synthesis and photocatalytic reactions. They also exhibit excellent reactivity in CO2 hydrogenation reactions. Ferric nitrate is a commonly used raw material for preparing iron-based catalysts, while ferrous sulfate is rarely used as an iron source for preparing iron-based catalysts. This is because the sulfur (S) it contains is a recognized catalyst poison, significantly degrading the catalyst's activity. Since ferrous sulfate is much cheaper than ferric nitrate, if the residual S in the catalyst can be effectively removed, it can be used to prepare iron-based catalysts with satisfactory reactivity, significantly reducing the preparation and operating costs of iron-based catalysts.

[0003] Chinese patent CN 112354540 A discloses a method for preparing an iron-based catalyst using ferrous sulfate as a raw material. The method uses oxalic acid as a precipitant, sugar as a reducing agent, and high-temperature roasting to reduce S ions. As is well known, high-temperature roasting consumes a lot of energy to generate a high-temperature environment and is also prone to high-temperature sintering of the catalyst, resulting in a reduction in the catalyst's active sites and thus lowering the catalyst's activity.

[0004] Chinese patent CN 113318744 A discloses a method for preparing an iron-based catalyst with high hydrocarbon selectivity. Specifically, ferrous sulfate is reacted with oxalic acid and potassium sodium tartrate by stirring simultaneously. The separated precipitate is washed three times with deionized water. The purpose of multiple washings and centrifugation is to remove free sulfur species from the precipitate.

[0005] The present invention adopts a CO2-assisted washing method to improve the washing effect, reduce the number of washing times, and endow the prepared iron-based catalyst with excellent reaction performance. Summary of the Invention

[0006] In view of the above technical problems existing in the prior art, the purpose of the present invention is to provide an iron-based catalyst and its preparation method and application that utilize CO2-assisted washing to eliminate the poisoning effect of sulfur element. The present invention discloses a washing method that effectively eliminates the poisoning effect of S element on the catalyst when preparing an iron-based catalyst using ferrous sulfate as raw material.

[0007] The method for preparing an iron-based catalyst that uses CO2-assisted washing to eliminate the poisoning effect of sulfur comprises the following steps: dissolving ferrous sulfate in deionized water to obtain a ferrous sulfate solution, adding ammonium carbonate to the solution, stirring the solution to react, and obtaining a precipitate; when washing the precipitate with deionized water, introducing CO2 gas while stirring, and then separating the washed precipitate by centrifugation or filtration; repeating the above washing and separation operations 0-2 times, preferably once; and then drying and calcining to obtain an iron-based catalyst solid.

[0008] Furthermore, the mass ratio of ferrous sulfate to ammonium carbonate is 1.2-1.8:1, preferably 1.4-1.6:1.

[0009] Furthermore, when the precipitate is washed with deionized water and CO2 is introduced to wash the precipitate, the washing time is 10 min to 180 min; based on the volume of the mixed solution for washing the precipitate with deionized water being 100 mL, the flow rate of the introduced CO2 is 5 ml / min to 40 ml / min.

[0010] Furthermore, the washing time is 80 min to 100 min.

[0011] Furthermore, after washing the precipitate, the precipitate is dried at 100-160°C for 8-16 h.

[0012] Furthermore, after drying the precipitate, the precipitate is calcined in an air atmosphere at 300-500° C. for 6-10 hours.

[0013] The iron-based catalyst provided by the present invention utilizes CO2-assisted washing to eliminate the poisoning effect of sulfur element and can be well applied in CO2 hydrogenation reaction.

[0014] The present invention achieves the following beneficial effects: When other preparation parameters remain the same, using a catalyst without CO2-assisted washing as a reference, the reaction performance of the catalyst obtained with CO2-assisted washing is not only higher than that of a reference catalyst washed the same number of times, but also higher than that of a reference catalyst washed more times. Measured reaction data demonstrates that the catalyst preparation method disclosed in this invention effectively eliminates the toxic effects of the sulfur element in the raw ferrous sulfate, reducing both the raw material cost of the iron-based catalyst and the amount of washing wastewater generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 2 is a comparison chart of the CO2 hydrogenation reaction activities of the catalysts of the embodiment and the comparative example. DETAILED DESCRIPTION

[0016] The invention is introduced below with reference to specific embodiments. It should be pointed out that the embodiments only describe the preparation process of the catalyst within a certain range. Without departing from the technical premise of the present invention, other researchers can make multiple modifications to the present invention, and these modifications should also be regarded as within the scope of protection of the present invention.

[0017] Example 1: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve it fully to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate into it to generate a turbid liquid, continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 30 minutes, and at the same time introduce CO2 into the solution at a flow rate of 10 ml / min. After washing is completed, centrifuge again and pour off the supernatant; then repeat the above washing and separation operations once; transfer the washed precipitate to a beaker, place it in a 120°C oven and dry it for 12 hours, and then calcine it at 350°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired particulate catalyst, recorded as catalyst 1.

[0018] Example 2: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve thoroughly to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate thereto to generate a turbid liquid, continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 60 minutes, and at the same time introduce CO2 into the solution at a flow rate of 20 ml / min. After washing is completed, centrifuge again and pour off the supernatant; then repeat the above washing and separation operations once; transfer the washed precipitate to a beaker, place it in a 120°C oven and dry it for 12 hours, and calcine it at 350°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired particulate catalyst, recorded as catalyst 2.

[0019] Example 3: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir to dissolve thoroughly, and obtain a ferrous sulfate solution. Add 24.0 g of ammonium carbonate to it to form a turbid liquid, and continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 90 minutes, and at the same time, introduce CO2 into the solution at a flow rate of 30 ml / min. After washing, filter and separate; then repeat the above washing and separation operations once; transfer the washed precipitate to a beaker, place it in a 140°C oven and dry it for 10 hours, and calcine it at 400°C for 6 hours to obtain a red powder. The powder is pressed into tablets, crushed and sieved to obtain the desired particulate catalyst, recorded as catalyst 3.

[0020] Example 4: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve thoroughly to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate thereto to generate a turbid liquid, continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 120 minutes, and at the same time introduce CO2 into the solution at a flow rate of 20 ml / min. After washing, centrifuge again and pour off the supernatant; then repeat the above washing and separation operations once; transfer the washed precipitate to a beaker, place it in a 120°C oven and dry it for 12 hours, and calcine it at 350°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired granular catalyst, recorded as catalyst 4.

[0021] Comparative Example 1: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve thoroughly to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate thereto to generate a turbid liquid, and continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 30 minutes, and after washing, centrifuge again and pour off the supernatant; then repeat the above washing and separation operations once; transfer the washed precipitate to a beaker, place it in a 120°C oven and dry it for 12 hours, and calcine it at 350°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired granular catalyst, recorded as Reference Catalyst 1.

[0022] Comparative Example 2: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve thoroughly to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate thereto to generate a turbid liquid, and continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 60 minutes, and after washing, centrifuge again and pour off the supernatant; then repeat the above washing and separation operations twice; transfer the washed precipitate to a beaker, place it in a 120°C oven and dry it for 12 hours, and calcine it at 350°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired granular catalyst, recorded as Reference Catalyst 2.

[0023] Comparative Example 3: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve thoroughly to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate thereto to form a turbid liquid, and continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 90 minutes, and then filter and separate after washing; then repeat the above washing and separation operations twice; transfer the washed precipitate to a beaker, place it in a 140°C oven and dry it for 10 hours, and calcine it at 400°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired granular catalyst, recorded as Reference Catalyst 3.

[0024] Comparative Example 4: First weigh 34.75 g of ferrous sulfate and place it in a beaker, react in a 40°C water bath, add an appropriate amount of deionized water (about 80 ml), stir and dissolve it to obtain a ferrous sulfate solution, add 24.0 g of ammonium carbonate thereto to form a turbid liquid, and continue stirring and aging; then centrifuge the turbid liquid; then wash the precipitate with 100 ml of deionized water for 120 minutes, and after washing, centrifuge again and pour off the supernatant; then repeat the above washing and separation operations once; transfer the washed precipitate to a beaker, place it in a 120°C oven and dry it for 12 hours, and calcine it at 350°C for 6 hours to obtain a red powder, press the powder into tablets, crush and sieve it to obtain the desired granular catalyst, recorded as Reference Catalyst 4.

[0025] The above catalysts were all tested for CO2 hydrogenation performance under the same reaction conditions. The specific reaction conditions were as follows: 1 g of catalyst was loaded into a fixed bed reactor for evaluation, first reduced at 300°C, a volume ratio of CO / N2=3 under normal pressure for 6 hours, and then reacted at 235°C, 1.6 MPa, a volume ratio of H2 / CO2=3, and a flow rate of H2 / CO2 mixed gas through the catalyst bed of 100 mL / min for 24 hours before sampling and analysis. The catalyst's CO2 conversion ability was shown in Table 1. Figure 1 The experimental results show that the reaction performance of the catalyst obtained by CO2-assisted washing is not only higher than that of the reference catalyst with the same number of washing times, but also higher than that of the reference catalyst with more washing times, indicating that CO2-assisted washing is an effective preparation method to eliminate the poisoning effect of S element on iron-based catalysts.

[0026] comparison Figure 1 In the curve (introducing CO2 and washing twice), the washing times of 30, 60, 90, and 120 min on the horizontal axis correspond to the application results of catalyst 1, catalyst 2, catalyst 3, and catalyst 4, respectively.

[0027] The horizontal axis of the curve (no CO2 injection, 2 washes) has washing times of 30 and 120 min, which correspond to the application results of reference catalyst 1 and reference catalyst 4, respectively.

[0028] The horizontal axis of the curve (no CO2 injection, washing 3 times) with washing times of 60 and 90 min corresponds to the application results of reference catalyst 2 and reference catalyst 3, respectively.

Claims

1. A method for preparing an iron-based catalyst using CO2-assisted washing to eliminate the poisoning effect of sulfur, characterized in that: Using deionized water to dissolve ferrous sulfate to obtain a ferrous sulfate solution, ammonium carbonate is added to the solution and stirred to react to obtain a precipitate; when washing the precipitate with deionized water, CO2 gas is introduced while stirring, and the washed precipitate is separated by centrifugation or filtration; Repeat the above washing and separation operations 0-2 times; then dry and calcine to obtain an iron-based catalyst solid; The mass ratio of ferrous sulfate to ammonium carbonate is 1.2-1.8:1; When the precipitate is washed with deionized water and CO2 is introduced to wash the precipitate, the washing time is 80 min to 100 min; Based on the volume of the mixed solution for washing the precipitate with deionized water being 100 mL, the flow rate of CO2 is 5 ml / min to 40 ml / min; After drying the precipitate, it is calcined at 300-500 °C in air atmosphere for 6-10 h.

2. The method for preparing an iron-based catalyst using CO2-assisted washing to eliminate sulfur poisoning as claimed in claim 1, characterized in that: The mass ratio of the ferrous sulfate to ammonium carbonate is 1.4-1.6:

1.

3. The method for preparing an iron-based catalyst using CO2-assisted washing to eliminate sulfur poisoning as claimed in claim 1, characterized in that: After washing the precipitate, dry it at 100 ~ 160 ℃ for 8 ~ 16 h.

4. The method for preparing an iron-based catalyst using CO2-assisted washing to eliminate sulfur poisoning as claimed in claim 1, characterized in that: Repeat the washing and separation process once.

5. An iron-based catalyst prepared by the method according to any one of claims 1 to 4 and using CO2-assisted washing to eliminate the poisoning effect of sulfur.

6. Use of an iron-based catalyst as claimed in claim 5 that utilizes CO2-assisted washing to eliminate the poisoning effect of sulfur in a CO2 hydrogenation reaction.

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