Process for the preparation of a catalyst by high temperature water gas shift and process for reducing the carbon monoxide content

Abstract

The present invention relates to a catalyst for the conversion of CO by high temperature water gas shift reaction, which is free of chromium and iron, consisting of potassium and zinc oxide promoted alumina. The catalyst thus prepared maintains high CO conversion activity, has no environmental or operational limitations and has low excess steam in the process, which is present in the catalysts of the prior art. This catalyst is used in processes for the production of hydrogen or syngas by hydrocarbon steam reforming, enables the use of low steam / carbon ratios in the process, provides high activity and stability upon thermal deactivation, and has fewer environmental limitations for production, storage, use and disposal compared to industrial catalysts based on iron, chromium and copper oxides.

Description

Technical Field

[0001] This invention relates to a method for preparing high-temperature water-gas shift catalysts, which are free of chromium and iron or precious metals, wherein they are used in a process for converting carbon monoxide (CO) and are applied in an H2 production unit to maintain high CO conversion activity without environmental restrictions or to operate in the process with low excess steam. Background Technology

[0002] The water-gas shift reaction (“water-gas shift”) is an integral step in the steam reforming process used for hydrogen production. The reaction can be represented by Equation 1, and it is exothermic and generally limited by thermodynamic equilibrium. CO + H₂O = CO₂ + H₂ (Equation 1)

[0003] This reaction produces H2 while reducing CO levels. CO is a contaminant in catalysts used in ammonia synthesis, hydrotreating, and fuel cells, which use high-purity hydrogen. In syngas production processes, the water-gas shift reaction is used to adjust the desired ratio of CO to H2. The water-gas shift reaction is also part of other H2 production processes, such as partial oxidation and autothermal reforming.

[0004] In steam reforming processes, the water-gas shift reaction takes place in the first stage, known as the "High Temperature Shift" (HTS), where the catalyst operates at a typical temperature between 330°C at the inlet and up to 450°C at the reactor outlet. A subsequent second stage, cooling the effluent gas and carrying out additional reactions, is called the "Low Temperature Shift" (LTS), where the catalyst operates at a typical temperature between 180°C at the inlet and 240°C at the reactor outlet. In variations of process configuration, the LTS reactor and subsequent amine-CO2 separation system are replaced by a "Pressure Swing Adsorption" (PSA) process. The pressure conditions are determined by the amount of hydrogen used, typically between 10 bar and 40 bar.

[0005] Commercial LTS catalysts consist of copper oxide, zinc oxide, and alumina, typically in concentrations between 40% m / m and 35% m / m, and between 27% m / m and 44% m / m, with the balance being alumina. They may also contain small amounts of basic promoters such as cesium (Cs) or potassium (K). LTS catalysts rapidly lose activity when exposed to high temperatures, which is why they are typically used in a temperature range of 180°C to 240°C, or in their "medium-temperature shift" (MTS) form at temperatures between 180°C and 330°C. The lower temperature range is usually determined by the requirement that steam condensation should not occur in the reactor at the unit's operating pressure.

[0006] Industrially used for large-scale plants (here considered to be hydrogen production exceeding 50,000 Nm³)3 The HTS catalyst in the device (with a capacity of / d) consists of iron (Fe), chromium (Cr), and copper (Cu), and exists primarily in the form of oxides before the catalyst begins operation. Despite its widespread use, a drawback of this catalyst formulation is the presence of chromium. Specifically, during the calcination step in the manufacture of this catalyst, varying levels of chromium in oxidized state VI (CrO3 or Cr2O3) inevitably form. 6+ Chromium, a compound known to be carcinogenic and harmful to the environment, is subject to increasingly stringent legislation worldwide. As an example, OSHA (Occupational Health and Safety Organization) guidelines on workplace exposure to chromium can be cited. 6+ Management regulations. Cr 6+ The presence of chromium has a negative impact on the manufacturing process, handling, transportation, loading, unloading, and disposal of materials. Therefore, it is desirable to teach the formulation of HTS catalysts that are free of chromium.

[0007] Several studies have reported on replacing chromium in STH catalyst formulations with iron, chromium, and copper-based compositions. According to the literature review "Performance of water gas shift reaction catalysts: Areview" (Renewable and Sustainable Energy Reviews, Vol. 93, pp. 549-565, 2018) by PAL, DB et al., studies have reported on replacing chromium with various elements (such as oxides of cerium, silicon, titanium, magnesium, zirconium, and aluminum), with aluminum being the most studied element. However, in industrial practice, no effective substitute for chromium has yet been found that offers the desired performance of reducing the surface area loss of the iron oxide phase present in the catalyst at typical process temperatures, thereby reducing the rate of material deactivation.

[0008] Another disadvantage of existing formulations of HTS catalysts is the presence of iron oxide in their composition, typically accounting for 80% to 90% of the catalyst's mass. The iron oxide in HTS catalysts is primarily in the form of hematite (Fe₂O₃), with small amounts of other iron hydroxides. After being loaded into the reactor, the catalyst undergoes an activation process that reduces the hematite phase (Fe₂O₃) to the magnetite phase (Fe₃O₄), which then forms the active phase of the catalyst. Simultaneously, during the reduction process, the CuO phase is reduced to metallic copper. An example of the reaction is as follows: 3 Fe₂O₃ + H₂ = 2 Fe₃O₄ + H₂O (Equation 2) CuO + H2 = Cu + H2O

[0009] The activation process must be carried out carefully to avoid over-reduction of the iron oxide phase, which can form undesirable FeO or even metallic Fe phase, leading to several problems such as decreased activity, catalyst decomposition with increasing pressure drop in the reactor, and the formation of byproducts via the Fischer-Tropsch reaction or methanation. Therefore, from an industrial perspective, HTS catalysts that do not require a reduction process or can even be heated with a gas containing high levels of H2 but free of moisture are ideal.

[0010] Once the Fe3O4 phase forms, its stability under industrial conditions depends on the ratio between the oxidizing and reducing components present in the reactor feed, particularly the H2O / H2 and CO2 / CO ratios. Literature teaches that when the steam content in the process decreases below a certain value, typically expressed as the steam / carbon ratio from the previous reforming step, the iron oxide phase transforms into the undesirable iron carbide phase. This iron carbide phase, in turn, leads to the formation of byproducts such as hydrocarbons, alcohols, and other compounds, which reduces hydrogen production and introduces additional difficulties for purifying the hydrogen produced and the condensed steam in the process. Therefore, it is desirable to teach HTS catalysts that do not contain iron in their composition.

[0011] The solution taught in US6500403 for reducing excess steam in H2 production processes via steam reforming involves a water-gas shift reaction in the first step at temperatures between 280°C and 370°C, using an iron-free and copper-based catalyst on a support. This reduces the CO / CO2 ratio at the inlet of the second stage, which is carried out on a conventional Fe / Cr catalyst, typically at temperatures between 350°C and 500°C. However, this solution increases the additional cost of the steam reforming process because it includes an additional CO removal step, or a feed cooling step after heating, which introduces energy losses and / or greater process complexity.

[0012] US4861745 teaches a more practical solution to avoid the formation of an iron carbide phase in an HTS catalyst. This patent describes adding copper oxide to an HTS catalyst formulation consisting of oxides of iron and chromium. According to this teaching, commercial HTS catalysts used in large-scale H2 production plants consist of oxides of iron, chromium, and copper. However, this solution can only be used at a minimum steam / carbon ratio of at most about 2.8 mol / mol. Therefore, steam is still used in large excess relative to the stoichiometry of the shift reaction (Equation 3), resulting in the undesirable effect of high energy consumption in the process, and further leading to greater CO2 emissions due to the energy required to burn fuel to heat the excess steam. CH4 + H2O = 3H2 + CO (Equation 3) C x Hy + xH2O = (y+2x) / 2H2+ xCO

[0013] Another solution taught in the literature for producing iron-free HTS catalysts in their formulations is the use of precious metals. RATNASAMY, C. and Wagner, JP's "Water gas shift catalysis" (Catalysis Reviews, Vol. 51, pp. 325-440, 2009) reviews the literature and teaches the use of platinum (Pt) deposited on various oxides such as those of zirconium, vanadium, aluminum, and cerium. These catalysts are sometimes used in fuel cell systems; however, their use in large-scale H2 production plants is limited due to the high cost and low availability of precious metals. Another disadvantage is that these catalysts are more sensitive to poisons present in the reactor feed, such as chlorides or sulfur, compared to conventional HTS catalysts based on iron, chromium, and copper oxides.

[0014] Documents US7998897, US81119099, and WO2018 / 134162A1 teach an HTS catalyst formulation free of iron and chromium. This catalyst is a mixture of zinc aluminate (ZnAl₂O₄) and zinc oxide (ZnO) with a Zn / Al molar ratio between 0.5 and 1.0, combined with an alkali metal selected from Na, K, Rb, Cs, and mixtures thereof, with the alkali metal content between 0.4% m / m and 8.0% m / m based on the oxidizing material. Specifically, invention US7998898 teaches a catalyst with a Zn / Al molar ratio of 0.7, containing 34% m / m to 35% m / m Zn and 7% to 8% Cs. However, questions remain regarding the activity and stability of such materials.

[0015] Therefore, it is desirable to provide an HTS catalyst that is free of chromium (Cr) (an element harmful to health and the environment) and iron (Fe), thereby enabling the use of reduced excess steam in the process and improving efficiency and energy, while maintaining high activity and stability under steam reforming conditions, thus allowing replacement of existing HTS catalysts in existing plants.

[0016] Patent US7964114B2 relates to the development of a catalyst for a water-gas exchange process, a method for manufacturing the catalyst, and a method for using the catalyst. The catalyst optionally consists of iron oxide, copper oxide, zinc oxide, aluminum oxide, and potassium oxide. Furthermore, the catalyst exhibits remarkable carbon monoxide conversion activity under high to medium temperature reaction conditions. However, the use of iron oxide in its formulation to achieve energy efficiency in H2 production via steam reforming prevents it from working with low excess steam (relative to the stoichiometry of the shift reaction).

[0017] Therefore, no prior art documents disclose a high-temperature water-gas shift catalyst used in the carbon monoxide conversion process as described in this invention.

[0018] To address these issues, the present invention was developed by providing an HTS catalyst that is free of chromium, iron, and precious metals, exhibiting high activity and resistance to thermal deactivation, i.e., maintaining its activity for extended periods even when exposed to high process temperatures.

[0019] In CO conversion processes, the reduction of excess steam (expressed as steam / gas ratio or steam / carbon ratio) can only be achieved by using iron-free HTS catalysts (such as those obtained in this invention). Furthermore, the removal of chromium, particularly carcinogenic Cr, from the catalyst formulation is crucial. 6+ The use of chromium minimizes the risks associated with catalyst handling, loading, and unloading processes.

[0020] Furthermore, using HTS catalysts resistant to low steam / gas ratios reduces the risk of process anomalies, which could lead to increased head loss and / or the formation of byproducts in the reactor. Therefore, reducing the steam / carbon ratio in steam reforming processes for H2 production helps reduce CO2 emissions from this process, as H2 production and FCC processes are the two largest sources of CO2 emissions during refining. Summary of the Invention

[0021] This invention relates to a catalyst for converting CO via a high-temperature water-gas shift reaction. The catalyst is free of chromium and iron and consists of potassium and zinc oxide-promoted alumina. Catalysts prepared in this manner maintain high CO conversion activity, have no environmental or operational limitations, and exhibit low excess steam in the process, as with prior art catalysts.

[0022] This catalyst is used in processes for producing hydrogen or syngas by steam reforming hydrocarbons, allowing for the use of low steam / carbon ratios in these processes. Compared to industrially used catalysts based on iron, chromium, and copper oxides, it exhibits high activity and stability against thermal deactivation and has fewer environmental restrictions on production, storage, use, and disposal. Attached Figure Description

[0023] The invention will now be described in more detail with reference to the accompanying drawings, which illustrate embodiments of the invention in a schematic form and without limiting the scope of the invention. The drawings show: - Figure 1 X-ray diffraction (XRD) patterns of solids obtained according to Examples 1 and 9 are shown; - Figure 2 X-ray diffraction (XRD) patterns of solids obtained according to Embodiments 10, 11 and 12 of the present invention are shown. Detailed Implementation

[0024] This invention relates to a catalyst suitable for the water-gas shift step in a steam reforming process to produce hydrogen. This catalyst consists of a potassium aluminate-type support containing zinc oxide as a promoter. The catalyst has a specific surface area greater than 60 m². 2 / g, based on oxidizing materials, with potassium content between 4% m / m and 15% m / m, and zinc oxide content between 10% m / m and 30% m / m, is obtained by a preparation method including the following steps. 1. Alumina is impregnated with an aqueous solution of potassium salt, followed by drying and calcination at a temperature between 400°C and 800°C to obtain potassium-promoted alumina, wherein the alumina is selected from boehmite, γ-alumina or θ-alumina, and the potassium salt is preferably potassium hydroxide, potassium carbonate or potassium nitrate; 2. An alumina-type carrier that has been promoted by potassium is impregnated with a polar solution containing zinc salt, preferably zinc nitrate or zinc carbonate, preferably an aqueous solution, then dried, formed into tablets, and then calcined at a temperature of 300°C to 500°C, preferably 350°C to 450°C.

[0025] The term potassium-promoted alumina used in this invention refers to alumina containing potassium on its surface. Depending on the calcination temperature, the potassium-promoted alumina can exhibit a crystal structure of alumina and potassium, such as K2O.Al2O3 (CAS 12003-62-3), by X-ray diffraction.

[0026] Alternatively, step 1 can be omitted, and commercial potassium aluminate can be used, as long as their specific surface area is greater than 15 m². 2 / g, preferably greater than 40 m 2 / g. In the presence of steam and at temperatures between 250°C and 450°C, alumina with greater resistance to comparative surface area loss, such as alumina promoted by lanthanum content between 1% m / m and 5% m / m, can also be used.

[0027] The forming step can be performed using commercial machines to obtain tablets, preferably with a typical size of 3 mm to 6 mm in diameter and height. Other forms can also be used, such as single cylinders or connected multi-cylinders (trilobite, tetralobite) or Raschig rings. Alternatively, in step 1, pre-formed alumina, such as γ-alumina or θ-alumina, can be used.

[0028] In another manner, the carrier is impregnated simultaneously with a potassium salt, preferably potassium hydroxide or potassium nitrate, and a zinc salt, preferably zinc nitrate or zinc carbonate, in a solution of a polar solvent, preferably water, followed by drying and calcination at a temperature between 400°C and 800°C.

[0029] The catalyst prepared in this way is active, stable, and ready to use, requiring no additional activation steps, and can be used for the conversion of CO with water vapor to produce hydrogen. The reactor inlet temperature is between 280°C and 400°C, preferably between 300°C and 350°C, and the reactor outlet temperature is between 380°C and 500°C, preferably between 400°C and 450°C. The operating pressure in the reactor can be 10 kgf / cm³. 2 Up to 40 kgf / cm 2 Within the range, preferably 20 kgf / cm 2 Up to 30 kgf / cm 2 The steam / dry gas molar ratio at the reactor inlet is preferably in the range of 0.05 mol / mol to 0.6 mol / mol, more preferably in the range of 0.1 mol / mol to 0.3 mol / mol. Similarly, the steam / carbon ratio (mol / mol) at the inlet of the primary steam reforming reactor preceding the high-temperature water-gas shift (HTS) reactor is preferably in the range of 1 mol / mol to 5 mol / mol, more preferably in the range of 1.5 mol / mol to 2.5 mol / mol. The CO concentration in the dry gas at the inlet of the conversion reactor is typically from 5% v / v to 30% v / v, preferably from 8% v / v to 20% v / v.

[0030] A second aspect of the invention is to provide an HTS catalyst that can be used with low excess steam, equivalent to a low steam / gas ratio at the HTS reactor inlet or a low steam / carbon ratio during steam reforming at the reactor inlet, without the formation of byproducts or increased head loss due to phase change of the material.

[0031] A third aspect of the invention is to provide a carbon monoxide conversion process by contacting the catalyst with a stream of syngas at a temperature between 250°C and 450°C, with the steam / gas ratio between 0.2 mol / mol and 1.0 mol / mol and the pressure between 10 atm and 40 atm.

[0032] According to a first aspect of the invention, a catalyst for a high-temperature water-gas shift reaction (HTS) is taught, consisting of potassium aluminate (KAlO2) promoted by zinc oxide (ZnO). Example:

[0033] The examples given below are intended to illustrate some ways of implementing the present invention and to demonstrate the practical feasibility of its application, and do not constitute any limitation on the present invention. Example 1:

[0034] According to existing technology, this comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. First, an aqueous solution containing 311 g of softened water (H2O) and 415 g of aluminum nitrate (Al(NO3)3·9H2O, brand VETEC, PA) with a nominal Zn / Al ratio of 0.5 mol / mol was prepared by dissolving and stirring at room temperature.

[0035] The solution was then swollen to 830 mL with softened water, resulting in a pH of 1.04. Ammonium hydroxide solution (NH4OH, 28% w / w, VETEC) was added to this solution over 30 minutes at room temperature with stirring at 300 rpm until the pH of the stirred mixture was between 8.0 and 8.5. The mixture was stirred for 1 hour, then filtered and washed with softened water. The precipitated material was then dried at 110 °C for 12 hours and then calcined in static air at 750 °C for 3 hours.

[0036] Characterization of the material using N2 adsorption technology (Brunauer-Emmett-Teller BET method) showed a specific surface area of ​​65 m². 2 / g, pore volume is 0.23 cm³ 3 / g, with an average pore size of 144 Å; the characteristic spectrum of zinc aluminate obtained by X-ray diffraction (XRD, Cu-K radiation, 40 kV, 40 mA) (JCPDS card, number 05-0669), as shown. Figure 1 As shown. Example 2:

[0037] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. 10 g of the material prepared in Example 1 was impregnated with 6.1 mL of an aqueous solution containing 0.145 g of potassium hydroxide (VETEC) using a pore volume technique. The material was dried at 100 °C for 1 hour and then calcined at 500 °C for 2 hours to obtain a zinc aluminate-type catalyst promoted with 1% m / m potassium. The product exhibited a 60.7 m... 2 Specific surface area per g, 0.24 cm² 3 The pore volume is 1 / g and the average pore diameter is 144.6 A. Example 3:

[0038] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. The preparation method is the same as that used in Example 2, except that the potassium hydroxide content is varied to achieve a nominal potassium content of 2% m / m. The product exhibits a 60.0 m... 2Specific surface area per g, 0.24 cm² 3 / g pore volume and 143 A average pore diameter. Example 4:

[0039] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. The preparation method is the same as that used in Example 2, except that the potassium hydroxide content is varied to achieve a nominal potassium content of 4% m / m. The product exhibits a 52 m... 2 Specific surface area per g, 0.22 cm² 3 / g pore volume and 151 A average pore diameter. Example 5:

[0040] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. The preparation method is the same as that used in Example 2, except that the potassium hydroxide content is varied to achieve a nominal potassium content of 8% m / m. The product exhibits a 42 m... 2 Specific surface area per g, 0.19 cm² 3 / g pore volume and 151 A average pore diameter. Example 6:

[0041] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. The preparation method is the same as that used in Example 2, except that the potassium source is replaced with potassium carbonate (K₂CO₃) to achieve a nominal potassium content of 4% m / m. The product showed a 39.0 m³ / m² yield using N₂ adsorption technology. 2 Specific surface area per g, 0.18 cm² 3 / g pore volume and 188 A average pore diameter. Example 7:

[0042] According to existing technology, this comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. Except for changing the reagent ratio to achieve a Zn / Al ratio of 0.70 mol / mol, the material was prepared in the same manner as in Example 1.

[0043] Characterization of the material showed that: a) the specific surface area was 22 m² / g using N₂ adsorption technology. 2 / g, pore volume 0.12 cm³ 3 / g, with an average pore size of 235 Å; b) by X-ray fluorescence quantitative quantification (FRX), the composition contains 25% m / m Al and 40% m / m Zn, with the balance being oxygen, and the standard characteristics of zinc aluminate were obtained by X-ray diffraction (XRD), such as Figure 1 As shown. Example 8:

[0044] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. 10 g of the material prepared in Example 7 was impregnated with 4.0 mL of an aqueous solution containing 0.598 g of potassium hydroxide (VETEC) using a pore volume technique. This material was dried at 100 °C for 1 hour and then calcined at 500 °C for 2 hours to obtain a zinc aluminate-type catalyst promoted with 4% m / m potassium. The product showed a 16.7 m... 2 Specific surface area per g, 0.10 cm² 3 / g pore volume and 173 A average pore diameter. Example 9:

[0045] This prior art comparative example illustrates the preparation of an alkali metal-promoted zinc aluminate-type high-temperature water-gas shift (HTS) catalyst. The preparation method is the same as that used in Example 8, except that the potassium hydroxide content is varied to achieve a nominal potassium content of 8% m / m. The product exhibits a 17.5 m... 2 Specific surface area per g, 0.08 cm² 3 / g pore volume and 176 A average pore diameter. Example 10:

[0046] This embodiment illustrates the preparation of a potassium- and zinc oxide-promoted alumina-type high-temperature water-gas shift (HTS) catalyst according to the present invention. 100 g of commercially available hydrated alumina (boehmite, CATAPAL, SASOL) was impregnated in 70 mL of an aqueous solution containing 11.5 g of potassium hydroxide (VETEC) using a wet spot method. The material was then dried at 100°C for 12 hours and calcined in static air at 600°C for 2 hours to obtain a potassium-promoted alumina-type support, such as… Figure 2 As shown. Using nitrogen adsorption technology (BET), the specific surface area of ​​this material is 111 m². 2 / g, pore volume 0.27 cm³ 3 / g.

[0047] A 15-gram support, obtained by impregnation with a 9.3 mL aqueous solution containing 6.09 g of zinc nitrate (Zn(NO3)2·6H2O, Merck) using a wet-spot technique, was then dried at 100 °C for 12 hours and calcined in static air at 400 °C for 2 hours to obtain a Zn content of 8.0 m / m (semi-quantitative analysis using X-ray fluorescence showed a content of 7.1% m / m) and a specific surface area of ​​89.5 m². 2 / g and pore volume of 0.21 cm³ 3 / g of material, and no obvious crystalline zinc aluminate was observed by X-ray diffraction, such as Figure 2 As shown. Example 11:

[0048] This embodiment of the invention illustrates the preparation of a potassium- and zinc oxide-promoted alumina-type high-temperature water-gas shift (HTS) catalyst. 15 g of the support obtained in Example 10 was impregnated with 9.3 mL of an aqueous solution containing 9.80 g of zinc nitrate (Zn(NO3)2·6H2O, Merck) using a wet-point technique, then dried at 100°C for 12 hours and calcined in static air at 400°C for 2 hours to obtain a Zn content of 12.1% m / m (semi-quantitative analysis using X-ray fluorescence showed a content of 10% m / m) and a specific surface area of ​​86.1 m². 2 / g and pore volume of 0.19 cm³ 3 / g of catalyst, and no obvious crystalline zinc oxide was observed by X-ray diffraction, such as Figure 2 As shown. Example 12:

[0049] This embodiment of the invention illustrates the preparation of a potassium- and zinc oxide-promoted alumina-type high-temperature water-gas shift (HTS) catalyst. 15 g of the catalyst obtained in Example 10 was impregnated with 9.3 mL of an aqueous solution containing 6.09 g of zinc nitrate (Zn(NO3)2·6H2O, Merck) using a wet-point technique, then dried at 100°C for 12 hours and calcined in static air at 400°C for 2 hours to obtain a Zn content of 16.1% m / m and a specific surface area of ​​81.1 m². 2 / g and pore volume of 0.19 cm³ 3 / g of catalyst, and no obvious crystalline zinc oxide was observed by X-ray diffraction, such as Figure 2 As shown. Example 13:

[0050] This embodiment describes the measurement of catalytic activity of the catalysts obtained according to Examples 1 to 12. The shift reaction was carried out in a fixed-bed reactor at atmospheric pressure. The sample was first heated to 100°C in an argon stream, and then heated to 350°C in a 5% H2 stream at a rate of 5°C / min in argon saturated with water vapor at 73°C. After this pretreatment, the gas mixture was replaced with a mixture containing 10% CO, 10% CO2, 2% methane, and the balance H2, and the temperature of the saturator was maintained at 73°C with water, corresponding to a vapor / gas ratio of 0.55 mol / mol. The reaction was carried out at temperatures from 350°C to 450°C, and the reactor effluent was analyzed by gas chromatography. The catalyst activity was expressed as CO conversion (% v / v).

[0051] The results are shown in Table 1, and it can be concluded that the catalyst of the present invention has a better surface area and activity (measured by the CO conversion rate in the water-gas shift reaction) than catalysts prepared according to the prior art. This superior performance is ideal in industry because it allows for the use of smaller catalyst volumes and / or lower operating temperatures, both of which are economically advantageous in the process. Table 1: Activity of HTS catalyst prepared according to existing technology and according to the present invention in water-gas shift reaction (XCO). Temperature (°C)

[0052] It should be noted that although the present invention has been described in conjunction with the accompanying drawings, those skilled in the art can modify and adjust it according to the specific circumstances, as long as it is within the scope of the invention as defined herein.

Claims

1. A method for preparing a high-temperature water-gas shift catalyst, characterized in that, Includes the following steps: a) Impregnating an alumina support with a solution of a polar solvent and a soluble potassium salt, wherein the alumina is selected from boehmite, γ-alumina, θ-alumina or lanthanum-promoted alumina; b) Dry the support to remove the solvent, and calcine the support at a temperature between 400°C and 800°C to obtain potassium-promoted alumina; c) Impregnate the potassium-promoted alumina with a polar solution containing a soluble zinc salt; d) Drying and calcining the material obtained in step c) at a temperature between 300°C and 500°C, wherein the catalyst has a specific surface area greater than 60 m². 2 / g, based on the weight of the oxidation catalyst, with potassium content ranging from 4% m / m to 15% m / m, zinc oxide content ranging from 10% m / m to 30% m / m, and a Zn / Al ratio of less than 0.4 mol / mol.

2. The method according to claim 1, characterized in that, The calcination in step (d) is carried out at a temperature between 350°C and 450°C.

3. The method according to claim 1, characterized in that, The potassium salt is selected from hydroxides, nitrates, or carbonates.

4. The method according to claim 1, characterized in that, The zinc salt is a nitrate or a carbonate.

5. The method according to claim 1, characterized in that, The polar solvent is water.

6. A process for reducing the carbon monoxide content, wherein the water-gas shift reaction comprises contacting the catalyst obtained in claim 1 with a stream of syngas, characterized in that, The synthesis gas contains between 5% and 30% CO, the steam / gas dry ratio is between 0.05 mol / mol and 0.6 mol / mol, the inlet temperature in the reactor is between 280°C and 400°C, and the pressure is 10 kgf / cm³. 2 Up to 40 kgf / cm 2 between.

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