Catalyst, process for its preparation, use and process for the treatment of carbon monoxide

Abstract

The application discloses a catalyst, a preparation method and application thereof, and a carbon monoxide treatment method. The catalyst comprises a base body and an alkali metal element loaded on the base body; the base body comprises SiO2 and a copper element, and the mass ratio of the SiO2 and the copper element is (65-85):25; the alkali metal element is selected from one or more of Na and K; and the content of the alkali metal element is 0.02-0.4 wt% based on the mass of the catalyst. The catalyst has good catalytic effect on a water-gas shift reaction at low temperature.

Description

Technical Field

[0001] This invention relates to a catalyst, its preparation method, its uses, and a method for treating carbon monoxide. Background Technology

[0002] Hydrogen energy is considered one of the most promising energy sources. Most hydrogen in nature combines with other elements such as carbon and oxygen and is stored in compounds such as water, fossil fuels, and biomass. Various methods have been developed to extract hydrogen from these compounds. The water-gas shift reaction (SFR) is a crucial step in clean hydrogen production and has received considerable attention in recent years due to its application in fuel cell hydrogen supply systems. The presence of CO can cause a decline in the performance of proton exchange membrane fuel cells due to electrode poisoning, while the SFR can reduce CO concentration. The SFR involves reacting CO and H2O in the gasification or reforming products of coal-hydrogen fuels, converting CO back into CO2, while H2O becomes the source of H2 generation. This allows for the production of clean H2 while reducing CO concentration.

[0003] The water-gas shift reaction is a reversible, moderately exothermic reaction, and lower temperatures are more favorable for it. However, as the reaction temperature decreases, the reaction rate also decreases, requiring longer reaction times and larger catalyst dosages to achieve the same CO conversion rate. To obtain clean H2 for fuel cells, novel water-gas shift catalysts with high activity and stability at low temperatures have become a key research focus. Copper-based catalysts, as non-precious metal catalysts, have the advantage of low cost; however, traditional copper-based catalysts have low conversion rates at their active sites, making it difficult to meet the requirements of fuel cell hydrogen supply systems. Summary of the Invention

[0004] One object of the present invention is to provide a catalyst that exhibits good catalytic activity for the water-gas shift reaction under low-temperature conditions. Further, the catalyst exhibits good selectivity, and the resulting catalytic product does not contain CH4. Another object of the present invention is to provide a method for preparing the catalyst, which improves the catalytic effect of the catalyst for the water-gas shift reaction under low-temperature conditions. A further object of the present invention is to provide an application of the catalyst. A still other object of the present invention is to provide a method for treating carbon monoxide, which enables the water-gas shift reaction to be carried out under low-temperature conditions with a high CO conversion rate. Further, this treatment method exhibits good selectivity, and the resulting product does not contain CH4.

[0005] The above objectives are achieved through the following technical solutions.

[0006] On one hand, the present invention provides a catalyst comprising a matrix and an alkali metal element supported on the matrix;

[0007] The matrix comprises SiO2 and copper, wherein the mass ratio of SiO2 to copper is (65-85):25.

[0008] The alkali metal element is selected from one or more of Na and K; based on the mass of the catalyst, the content of the alkali metal element is 0.02 to 0.4 wt%.

[0009] Alkali metal elements supported on a matrix can exist in the form of their oxides. In some embodiments, the catalyst consists of a matrix and an alkali metal oxide supported on the matrix.

[0010] Preferably, the mass ratio of SiO2 to copper in the matrix is ​​(70-80):25. Copper may be present in the form of its oxide. In some embodiments, the matrix consists of SiO2 and copper oxide.

[0011] Preferably, the content of alkali metal elements is 0.1–0.35 wt% based on the mass of the catalyst. Most preferably, the content of alkali metal elements is 0.25–0.3 wt% based on the mass of the catalyst.

[0012] In the catalyst according to the present invention, preferably, the alkali metal element is K.

[0013] On the other hand, the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0014] (1) The copper-containing silicate precursor was calcined to obtain the matrix;

[0015] (2) The matrix is ​​immersed in an aqueous solution containing an alkali metal element precursor to obtain a precursor loaded with alkali metal;

[0016] (3) The precursor loaded with alkali metal is calcined to obtain the catalyst.

[0017] According to the preparation method of the present invention, preferably, in step (1), the calcination temperature is 300-500°C, the calcination time is 2-6 hours, and the calcination is carried out in an air atmosphere;

[0018] In step (2), an equal-volume impregnation method is used, and the impregnation time is 15 to 35 hours;

[0019] In step (3), the roasting temperature is 300-500℃, the roasting time is 2-6h, and the roasting is carried out in an air atmosphere.

[0020] More preferably, in step (1), the roasting temperature is 350-450°C.

[0021] More preferably, in step (1), the roasting time is 3 to 5 hours.

[0022] In step (2), an equal-volume impregnation method can be used. The alkali metal precursor can be selected from alkali metal carbonates or alkali metal nitrates. For example, sodium carbonate, sodium nitrate, potassium carbonate, and potassium nitrate.

[0023] The concentration of the aqueous solution containing the alkali metal element precursor can be determined based on the water absorption ratio of the matrix. In some embodiments, the concentration of the aqueous solution containing the alkali metal element precursor can be 0.01–0.4 wt%. For example, 0.03–0.3 wt%; or 0.1–0.2 wt%.

[0024] The soaking time can be 15 to 35 hours; preferably 20 to 30 hours; more preferably 24 to 28 hours.

[0025] The impregnated product can be dried to obtain a precursor loaded with alkali metals. Drying can be carried out under vacuum conditions. Vacuum can refer to a pressure ≤10 Pa; preferably, a pressure ≤1 Pa; more preferably, a pressure ≤10 Pa. -1 The drying temperature can be 40–80°C; preferably 50–70°C. The drying time can be 5–20 h; preferably 10–15 h.

[0026] More preferably, in step (3), the roasting temperature is 350-450°C.

[0027] More preferably, in step (3), the roasting time is 3 to 5 hours.

[0028] According to the preparation method of the present invention, preferably, the copper-containing silicate precursor is a layered silicate precursor obtained by the ammonia stripping method.

[0029] According to the preparation method of the present invention, preferably, it further includes the following steps:

[0030] (a) Add ammonia water to the aqueous solution containing the copper precursor and adjust the pH to 11-12 to obtain a copper ammonia solution;

[0031] (b) Add silica sol to a copper ammonia solution and then perform ammonia stripping to obtain a copper silicate precursor.

[0032] Ammonia can be added to an aqueous solution containing a copper precursor under stirring. The stirring speed can be 1000–1600 r / min; preferably 1200–1400 r / min.

[0033] Preferably, ammonia is added to the aqueous solution of the copper-containing precursor to adjust the pH to 11.3-11.5.

[0034] After the ammonia solution is added, stirring can continue to obtain a copper ammonium solution. The stirring time can be 15–50 min; preferably 25–40 min.

[0035] According to the preparation method of the present invention, preferably, in the aqueous solution containing the copper precursor, the mass-to-volume ratio of the copper precursor to water is (3.5-7) g / 100 mL; and the concentration of ammonia is 20-28 wt%.

[0036] More preferably, in the aqueous solution containing the copper precursor, the mass-to-volume ratio of the copper precursor to water is (5-6.5) g / 100 mL.

[0037] More preferably, the concentration of ammonia water is 25–28 wt%.

[0038] The copper precursor can be selected from one or more of copper nitrate, copper chloride, and copper acetate. Preferably, the copper precursor is copper nitrate.

[0039] Silica sol can be added to the copper ammonia solution under stirring. The stirring speed can be 1000–1600 r / min; preferably 1200–1400 r / min.

[0040] The concentration of silica sol can be 15–35 wt%; preferably 20–30 wt%.

[0041] The mass ratio of copper precursor to silica sol can be 5.7:(10-25); preferably 5.7:(15-20).

[0042] According to the preparation method of the present invention, preferably, in step (b), after the silica sol is added, the mixture is stirred for 5 to 10 hours, and then subjected to ammonia stripping treatment under a water bath at 75 to 100°C for 1 to 3 hours.

[0043] Before ammonia stripping, the mixture formed by the copper ammonia solution and silica sol is stirred. The stirring time can be 5 to 10 hours; preferably 5 to 7 hours.

[0044] Ammonia stripping can be carried out at 75–100°C; preferably, at 85–95°C. Heating can be performed using a water bath.

[0045] The preferred ammonia stripping treatment time is 1.5 to 2.5 hours.

[0046] The gel obtained from ammonia stripping can be washed and dried to obtain a copper-containing silicate precursor.

[0047] The washing process can be performed by vacuum filtration. The washing solvent can be selected from one or more of water, methanol, ethanol, n-propanol, and isopropanol. In some embodiments, water and ethanol are used for washing separately.

[0048] Drying can be carried out under vacuum conditions. Vacuum can refer to a pressure ≤10 Pa; preferably, the pressure ≤1 Pa; more preferably, the pressure ≤10 Pa. -1 The drying temperature can be 40–80°C; preferably 50–70°C. The drying time can be 5–20 h; preferably 10–15 h.

[0049] On the other hand, the present invention provides the use of the above-mentioned catalyst in water-gas shift reaction.

[0050] In another aspect, the present invention provides a method for treating carbon monoxide, comprising the following steps:

[0051] (I) The above catalyst is reduced in an atmosphere containing H2 and an inert gas to obtain the reduced catalyst;

[0052] (II) The reaction gas containing CO and H2O is reacted in the presence of a reduced catalyst.

[0053] The above method can react CO and H2O to form CO2 and H2. This is the water-gas shift reaction.

[0054] The inert gas can be selected from one or more of nitrogen, helium, neon, and argon. Preferably, the inert gas is nitrogen.

[0055] The volume ratio of H2 to inert gas can be 1:(6-12); preferably 1:(8-10).

[0056] The reduction reaction temperature can be 200–500℃; preferably 300–400℃. The reaction time can be 0.5–4 h; preferably 1–2 h.

[0057] The reduction reaction can be carried out in a reactor. The flow rate of the mixture of H2 and inert gas into the reactor can be 20–70 mL / min; preferably 40–60 mL / min.

[0058] The reaction temperature in step (II) can be 150–400°C; preferably 200–350°C; more preferably 300–350°C.

[0059] The reaction gas may also contain N2. The content of H2O can be 10-20 vol%, preferably 13-17 vol%. The content of CO can be 1-10 vol%, preferably 3-7 vol%. The content of N2 can be 70-90 vol%, preferably 75-85 vol%.

[0060] The reactant gas and the reduced catalyst can react in a fixed-bed reactor. The flow rate of the reactant gas can be 45–80 mL / min; preferably 55–70 mL / min.

[0061] The amount of the reduced catalyst can be 0.05–0.5 g; preferably 0.1–0.3 g.

[0062] The catalyst of this invention exhibits excellent catalytic activity at low temperatures, effectively catalyzing the water-gas shift reaction and improving CO conversion. Furthermore, the catalyst of this invention demonstrates excellent selectivity, and the catalytic products do not contain CH4. Detailed Implementation

[0063] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0064] The testing method is described below:

[0065] CO conversion rate: The post-reaction gases were analyzed online using an Agilent 7890A gas chromatograph. This gas chromatograph mainly consists of three separation columns: two MolSieve 5A columns, one PoraPak Q capillary column, and three backflush columns. The molecular sieve columns and backflush columns are primarily used to separate CO2, CO, N2, and other gases, while the capillary columns are mainly used to separate organic compounds (methane and C). 2+ The three detectors consist of a flame ionization detector (FID) and two thermal conductivity detectors (TCDs). The reaction products are primarily detected using TCDs.

[0066] Finally, data analysis was performed on the spectrum, including the CO conversion rate X. CO Calculate using the following formula: X CO =(F CO,in -F CO,out ) / F CO,in ×100%.

[0067] Wherein: F CO,in F CO,out These represent the molar flow rates of carbon monoxide in the reactant gas and the post-reaction gas, respectively.

[0068] Examples 1-4

[0069] 5.7 g of copper nitrate was dissolved in 100 mL of deionized water to form an aqueous solution containing a copper precursor. Under mechanical stirring at 1300 r / min, 25 wt% ammonia solution was added to the aqueous solution containing the copper precursor, the pH was adjusted to 11.5, and then stirred for 30 min to obtain a copper-ammonia solution.

[0070] Under mechanical stirring at 1300 r / min, 18 g of silica sol with a concentration of 25 wt% was added dropwise to a copper ammonia solution. After stirring for 6 h, the solution was treated with ammonia vaporization in a 90 °C water bath for 2 h to form a gel. The gel was washed three times with deionized water and ethanol respectively, and then vacuum dried at 60 °C for 12 h to obtain a copper-containing silicate precursor.

[0071] The copper-containing silicate precursor was calcined in air at 400°C for 4 hours to obtain the matrix.

[0072] 0.5 g of the matrix was impregnated in an equal volume of an aqueous solution containing an alkali metal precursor for 24 h, and then vacuum dried at 60 °C for 12 h to obtain the precursor loaded with the alkali metal. The aqueous solution containing the alkali metal precursor was formed by mixing an alkali metal salt solution and water.

[0073] The precursor loaded with alkali metal was calcined in air at 400°C for 4 h to obtain the catalyst. In the obtained catalyst, the alkali metal element was supported on a matrix containing SiO2 and copper, with a mass ratio of SiO2 to copper (calculated as Cu) of 75:25.

[0074] The selection, concentration, and amount of alkali metal salt solution, the amount of water used to prepare the aqueous solution containing alkali metal element precursors, and the types and contents of alkali metal elements contained in the catalyst are shown in Table 1.

[0075] Table 1

[0076]

[0077] Comparative Example 1

[0078] Except that the alkali metal salt solution is a lithium nitrate solution with a concentration of 1 wt%; and the amount of alkali metal salt solution and water used to form the aqueous solution containing the alkali metal element precursor is adjusted so that the lithium content in the catalyst is 0.05 wt%, the rest is the same as in Example 1.

[0079] Comparative Example 2

[0080] Except for adjusting the amount of alkali metal salt solution and water used to form the aqueous solution containing alkali metal element precursor, so that the potassium content in the catalyst is 0.5 wt%, the rest is the same as in Example 1.

[0081] Comparative Example 3

[0082] Except for adjusting the amount of alkali metal salt solution and water used to form the aqueous solution containing alkali metal element precursor, so that the potassium content in the catalyst is 1 wt%, the rest is the same as in Example 1.

[0083] Comparative Example 4

[0084] The matrix prepared using the method of Example 1 was used as the catalyst in this comparative example.

[0085] Examples 5-20 and Comparative Examples 5-20

[0086] The catalyst was reacted in a reactor at 350°C for 1 h in a mixed gas atmosphere consisting of H2 and N2 in a volume ratio of 1:9 to obtain the reduced catalyst. The flow rate of the mixed gas into the reactor was 50 mL / min.

[0087] The reaction gas was introduced at a flow rate of 60 mL / min into an atmospheric pressure fixed-bed reactor (model MRE-962, purchased from Beijing Xiandali Petrochemical Technology and Trade Co., Ltd.) containing 0.2 g of reduced catalyst. The reduced catalyst and reaction gas were reacted in the fixed-bed reactor for 1 h to obtain the reaction gas. The reaction gas consisted of 15 vol% H2O, 5 vol% CO, and 80 vol% N2.

[0088] The selection of catalyst, reaction temperature of catalyst and reactant gas, CO conversion rate, and catalyst selectivity are shown in Table 2.

[0089] Table 2

[0090]

[0091]

[0092] Comparing the catalysts of Examples 1-4 and Comparative Example 4, it is evident that the addition of potassium and sodium elements can improve the catalytic effect of the catalyst in the water-gas shift reaction under low-temperature conditions, thereby increasing the CO conversion efficiency. Comparing the catalysts of Examples 1, 3, and Comparative Example 1, it is evident that while the molar content of alkali metal elements in the catalysts of Examples 1, 3, and Comparative Example 1 is consistent, the catalytic effect of the catalyst of Comparative Example 1 is far inferior to that of the catalysts of Examples 1 and 3, indicating that the selection of alkali metal elements has a significant impact on the catalytic effect of the catalyst. Comparing the catalysts of Examples 1-2, 4, and Comparative Examples 2-3, it is evident that the potassium (K) content has a significant impact on the catalytic performance of the catalyst.

[0093] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A catalyst, characterized in that, The catalyst comprises a matrix and an alkali metal element supported on the matrix; The matrix comprises SiO2 and copper, wherein the mass ratio of SiO2 to copper is (65-85):

25. The alkali metal element is selected from one or more of Na and K; based on the mass of the catalyst, the content of the alkali metal element is 0.02 to 0.4 wt%.

2. The catalyst according to claim 1, characterized in that, The alkali metal element is K.

3. The method for preparing the catalyst according to any one of claims 1 to 2, characterized in that, The steps include the following: (1) The copper-containing silicate precursor was calcined to obtain the matrix; (2) The matrix is ​​immersed in an aqueous solution containing an alkali metal element precursor to obtain a precursor loaded with alkali metal; (3) The precursor loaded with alkali metal is calcined to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that: In step (1), the roasting temperature is 300-500℃, the roasting time is 2-6h, and the roasting is carried out in an air atmosphere; In step (2), an equal-volume impregnation method is used, and the impregnation time is 15 to 35 hours; In step (3), the roasting temperature is 300-500℃, the roasting time is 2-6h, and the roasting is carried out in an air atmosphere.

5. The preparation method according to claim 3, characterized in that, The copper-containing silicate precursor is a layered silicate precursor obtained by the ammonia stripping method.

6. The preparation method according to claim 3, characterized in that, It also includes the following steps: (a) Add ammonia water to the aqueous solution containing the copper precursor and adjust the pH to 11-12 to obtain a copper ammonia solution; (b) Add silica sol to a copper ammonia solution and then perform ammonia stripping to obtain a copper silicate precursor.

7. The preparation method according to claim 6, characterized in that, In the aqueous solution containing the copper precursor, the mass-to-volume ratio of the copper precursor to water is (3.5–7) g / 100 mL; the concentration of ammonia is 20–28 wt%.

8. The preparation method according to claim 6, characterized in that, In step (b), after the silica sol is added, the mixture is stirred for 5 to 10 hours, and then subjected to ammonia stripping treatment for 1 to 3 hours under a water bath at 75 to 100°C.

9. Use of the catalyst according to any one of claims 1 to 2 in water-gas shift reaction.

10. A method for treating carbon monoxide, characterized in that, The steps include the following: (I) The catalyst according to any one of claims 1 to 2 is subjected to a reduction reaction in an atmosphere containing H2 and an inert gas to obtain a reduced catalyst; (II) The reaction gas containing CO and H2O is reacted in the presence of a reduced catalyst.

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