High-purity low-sodium methanol synthesis catalyst and preparation method thereof

Abstract

The invention relates to the field of methanol synthesis catalysts, and particularly discloses a high-purity low-sodium methanol synthesis catalyst and a preparation method thereof. The preparation method of the high-purity low-sodium methanol synthesis catalyst comprises the following steps: mixing aluminum nitrate and sodium hydroxide for reaction to obtain pseudo-boehmite colloid; carrying out cross-flow filtration on the pseudo-boehmite colloid by adopting an ultrafiltration membrane under an ultrasonic condition, and carrying out backwashing to obtain sodium-removed alumina gel; mixing sodium carbonate with the copper-zinc mixed solution for co-precipitation, and washing the precipitate to obtain a binary precursor; and mixing the sodium-removed alumina gel with the binary precursor, pulping, aging, washing to further remove sodium, filtering, and drying, granulating, calcining and forming a filter cake to obtain the high-purity low-sodium methanol catalyst. The preparation method of the high-purity low-sodium methanol catalyst has the advantages that the content of impurity sodium can be reduced, and the catalytic activity and selectivity of the methanol synthesis catalyst are improved.

Description

Technical Field

[0001] This application relates to the field of methanol synthesis catalysts, and more specifically, it relates to a method for preparing a high-purity, low-sodium methanol synthesis catalyst. Background Technology

[0002] Methanol is a basic chemical raw material and an energy carrier, widely used in the synthesis of pharmaceuticals, pesticides, acetic acid, formaldehyde, and other chemicals, playing a crucial role in chemical production. With the depletion of fossil resources such as coal, oil, and natural gas, and increasingly stringent domestic environmental protection requirements, methanol, as an environmentally friendly energy source, is gaining increasing favor among researchers. Uniformly dispersed boehmite (aluminum colloid) serves as the carrier for the active components copper and zinc in methanol synthesis catalysts, significantly impacting catalyst performance. Currently, the method of synthesizing aluminum colloid using sodium carbonate as a precipitant is widely used due to its compliance with increasingly stringent environmental requirements. However, the aluminum colloid produced by this method has a high sodium ion content, and removing sodium ions while maintaining uniform dispersion is extremely difficult. Excessive sodium impurities negatively affect the performance of methanol synthesis catalysts. Existing academic research has demonstrated that high sodium content in methanol synthesis catalysts promotes the formation of higher alcohols, ultimately masking the catalyst's activity and stability.

[0003] To address the issue of excessive sodium content in methanol synthesis catalysts, a method for preparing high-temperature resistant, low-sodium aluminum hydroxide has been disclosed. This method involves slowly adding an inorganic acid solution dropwise to a sodium aluminate solution at 80–90°C. After 1–3 minutes of acid addition, ultrasonic treatment begins and continues for 0.5–1 hour after sedimentation. The ultrasonic treatment is then stopped, and the precipitate is filtered, washed, and the solid aluminum hydroxide is obtained. During the experiment, the aluminum hydroxide was in a colloidal state. Sodium ions loaded on its surface were easily washed away, while sodium ions encapsulated in the bulk were difficult to remove due to a lack of contact sites with water.

[0004] In light of the aforementioned technologies, finding a highly efficient sodium removal technology that can effectively remove sodium ions without damaging the dispersibility of aluminum glue is an urgent problem to be solved. Summary of the Invention

[0005] In order to fully remove sodium impurities from methanol synthesis catalysts, this application provides a method for preparing high-purity, low-sodium methanol synthesis catalysts.

[0006] In a first aspect, this application provides a method for preparing a high-purity, low-sodium methanol synthesis catalyst, employing the following technical solution:

[0007] A method for preparing a high-purity, low-sodium methanol synthesis catalyst includes the following steps:

[0008] Aluminum nitrate and sodium hydroxide were mixed and reacted to obtain boehmite colloid;

[0009] Under ultrasonic conditions, the pseudoboehmite colloid is subjected to cross-flow filtration using an ultrafiltration membrane, and the ultrafiltration membrane is backwashed while the pseudoboehmite colloid is circulated and washed to obtain desodium-free aluminum colloid.

[0010] Sodium carbonate was mixed with a copper-zinc mixture for co-precipitation, and the precipitate was washed to obtain a binary precursor.

[0011] The sodium-removed aluminum gel is mixed with the binary precursor, pulped, aged, and then washed to further remove sodium. After filtration, the filter cake is dried, granulated, calcined, and shaped to obtain a high-purity, low-sodium methanol catalyst.

[0012] By employing the above technical solution, aluminum hydroxide particles with a diameter between 20µm and 30µm, and sodium ions with a diameter less than 1nm, can effectively filter and remove sodium ions while retaining the boehmite colloids through ultrafiltration membrane filtration. The cross-flow filtration method creates turbulent flow of the boehmite colloidal fluid on the membrane surface, flushing the membrane and reducing the possibility of aluminum colloid deposition. Simultaneously, backwashing further ensures the unobstructed flow of the membrane surface and internal pores, reducing aluminum colloid deposition. Ultrasonic assistance further promotes the removal of sodium ions and reduces aluminum colloid deposition. The synergistic effect of cross-flow filtration, backwashing agent, and ultrasonic assistance improves filtration efficiency and effectiveness, ensures filtration stability, and reduces membrane pore blockage and aluminum colloid deposition. Combined with circulating washing, the sodium content in the boehmite colloid is further reduced, ensuring the boehmite remains in a colloidal state with good dispersibility, providing abundant loading sites for copper and zinc, which is beneficial for improving catalytic effect and stability, and extending catalyst lifespan.

[0013] Preferably, the preparation method of the pseudoboehmite colloid specifically includes: adding 1-2 mol / L sodium hydroxide solution to a 3-15 g / L aluminum nitrate solution at 40-80℃ until the pH value is 7-8, and then aging to obtain the pseudoboehmite colloid.

[0014] Preferably, the ultrafiltration membrane is selected from one of PES membrane, PVDF membrane, and PAN membrane.

[0015] Preferably, the ultrafiltration membrane is a PES membrane, and the membrane molecular weight of the ultrafiltration membrane is 5000-30000.

[0016] By adopting the above technical solution, as the membrane molecular weight increases, the membrane pore size decreases, and the selective filtration effect is improved, which is beneficial to improving the removal effect of sodium ions. However, when the membrane molecular weight exceeds 30,000, the membrane pore size becomes too small, the separation effect decreases, and membrane pore blockage may occur. Adjusting the membrane molecular weight within the range of 5,000-30,000 can ensure that the ultrafiltration membrane has a better sodium filtration effect and reduce the possibility of decreased filtration efficiency due to membrane pore blockage.

[0017] Preferably, the molecular weight of the PES membrane is 8000, and the ultrasonic conditions are: ultrasonic power 50W and ultrasonic temperature 50℃.

[0018] By adopting the above technical solution, excessively high ultrasonic power or ultrasonic temperature will cause the temperature of the pseudoboehmite colloid to be too high, which in turn will cause the temperature of the ultrafiltration membrane to rise and affect the filtration function. When the temperature of the ultrafiltration membrane is too high, it will age and decompose, and will not have the ability to separate sodium ions. Adjusting the ultrasonic power and ultrasonic temperature within the scope disclosed in this application can ensure filtration stability, promote the filtration of sodium ions and reduce aluminum colloid residue.

[0019] Preferably, the molecular weight of the PES membrane is 8000, and the ultrasonic conditions are: ultrasonic power 50W and ultrasonic time 90W.

[0020] Through the above technical solutions, the applicant has demonstrated through extensive creative work that, under the aforementioned conditions, the methanol synthesis catalyst exhibits superior catalytic activity and selectivity, as well as better overall performance.

[0021] Preferably, the backwashing includes gas washing of the outer layer of the ultrafiltration membrane and liquid washing of the inner layer of the ultrafiltration membrane.

[0022] By adopting the above technical solution, the ultrafiltration membrane is backwashed through gas washing and liquid washing, which reduces the possibility of aluminum colloid clogging the membrane pores, thus improving filtration efficiency and enhancing the fluidity and dispersibility of the aluminum colloid.

[0023] Preferably, the washing time of the cyclic washing is 60-180 minutes, and the washing water volume is 200-1000 ml of water per 1000 ml of pseudoboehmite colloid.

[0024] By adopting the above technical solution, thorough washing can reduce the sodium content in the pseudoboehmite colloid, and it is beneficial to ensure that the pseudoboehmite is in a colloidal state with good flowability and dispersibility.

[0025] Preferably, the method for preparing the binary precursor specifically includes:

[0026] Under a pressure of 150-250 psi, a copper-zinc mixture and a sodium carbonate solution were mixed at a flow rate ratio of 1:3 and subjected to intermittent co-precipitation under stirring at a speed of 500-2000 r / min. The precipitate was washed with deionized water to obtain the binary precursor.

[0027] The mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:(1-4), and the concentration of copper ions is 50-80 g / L; the concentration of sodium carbonate solution is 1-2 mol / L.

[0028] Preferably, the high-purity, low-sodium methanol synthesis catalyst specifically comprises: mixing the desodium-aluminum gel with the binary precursor, slurrying, aging, washing with 20-40L of deionized water and filtering, drying the filter cake at 90-100℃ for 6-8h, then crushing and granulating, calcining at high temperature, and forming into flakes.

[0029] By adopting the above technical solution, the copper-zinc active components are loaded together with the aluminum gel carrier components and then deeply washed with deionized water to further remove residual sodium on the surface, which is beneficial to further reduce the residual sodium content on the catalyst.

[0030] Secondly, this application provides a high-purity, low-sodium methanol synthesis catalyst, employing the following technical solution:

[0031] A high-purity, low-sodium methanol synthesis catalyst is prepared by the above-mentioned method for preparing a high-purity, low-sodium methanol synthesis catalyst.

[0032] The high-purity, low-sodium methanol synthesis catalyst includes a boehmite support and copper-zinc active components dispersed on the boehmite support; and the sodium content of the high-purity, low-sodium methanol synthesis catalyst is not higher than 645 ppm.

[0033] Preferably, the particle size of the high-purity, low-sodium methanol synthesis catalyst is 16-40 mesh.

[0034] Preferably, the high-purity, low-sodium methanol synthesis catalyst needs to be activated before participating in the catalytic methanol synthesis reaction. The activation includes: placing the high-purity, low-sodium methanol synthesis catalyst in an inert atmosphere containing hydrogen and calcining and reducing it at 200-250°C for 8-16 hours.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. Because this application uses an ultrafiltration membrane to filter boehmite colloids, it can filter out sodium ions and retain boehmite colloids. Through the synergistic effect of cross-flow filtration, backwashing agent and ultrasonic assistance, the filtration efficiency and effect are improved, the filtration stability is ensured, and membrane pore clogging and aluminum colloid deposition are reduced. At the same time, with the addition of circulating washing, the sodium content in the boehmite colloids is further reduced, and the boehmite is kept in a colloidal state with good dispersibility, providing abundant loading sites for copper and zinc, which is beneficial to improving the catalytic effect and catalytic stability, and promoting the improvement of catalyst life.

[0037] 2. In this application, an ultrafiltration membrane with a molecular weight of 5,000-30,000 is preferred, which can ensure a better sodium ion removal effect, while avoiding the possibility of membrane pore blockage and reduced separation effect caused by excessively large molecular weight and small pore size.

[0038] 3. By controlling the ultrasonic power and ultrasonic temperature of the ultrasonic treatment, the filtration stability is ensured and the aluminum glue residue is reduced. It can also reduce the possibility of decreased ultrafiltration membrane stability and reduced filtration function caused by excessive ultrasonic power or ultrasonic temperature. Detailed Implementation

[0039] To further aid in understanding the technical solution of this invention, several specific implementation examples are provided below to describe the technical solution of this invention in more detail. All of these described embodiments are only some embodiments of this invention, and not all of them.

[0040] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments; and the reaction devices, monomer compounds, etc. involved in the following embodiments are all commercially available.

[0041] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0042] The following examples further illustrate the present invention, but the invention is not limited thereto. Unless otherwise specified in the examples, all percentages (%) are mass percentages.

[0043] Example

[0044] Example 1

[0045] This embodiment discloses a high-purity, low-sodium methanol synthesis catalyst, which is prepared by a method including the following steps:

[0046] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0047] Step 2: Control the ultrasonic power to 30W and the ultrasonic temperature to 40℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. In this embodiment, the membrane separation device with backwashing function is an ultrafiltration membrane evaluation instrument of model UFMT-01. Using the membrane separation device, cross-flow filtration is performed on the pseudoboehmite colloid using a PES membrane with a molecular weight of 5000, followed by circulation washing and backwashing to obtain desodium-free aluminum colloid. The circulation washing time and ultrasonic time are both 60min, and the water volume for circulation washing is 200ml.

[0048] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0049] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 20L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 90℃ suspension oven to dry for 6 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0050] In this embodiment, the particle size range of the high-purity, low-sodium methanol synthesis catalyst is 16-40 mesh.

[0051] Example 2

[0052] The only difference between this embodiment and Example 1 is that the preparation method of the high-purity, low-sodium methanol synthesis catalyst is as follows:

[0053] Step 1: At 60℃, add 1mol / L sodium hydroxide solution to 6g / L aluminum nitrate solution until the pH of the mixed solution is 7.2, and then age for 30 minutes to obtain pseudoboehmite colloid.

[0054] Step 2: Control the ultrasonic power to 50W and the ultrasonic temperature to 50℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 8000 to perform cross-flow filtration on the pseudoboehmite colloid, and perform circulating washing and backwashing to obtain desodium-free aluminum colloid. The circulating washing time and ultrasonic time are both 90min, and the water volume for circulating washing is 400ml.

[0055] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1.5mol / L sodium carbonate solution and 1L of copper-zinc mixture were mixed at a flow rate ratio of 3:1, and intermittent coprecipitation was carried out under stirring at 800r / min. The coprecipitated product was washed 4 times with deionized water to obtain the binary precursor. In this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture was 1:2, and the copper ion concentration was 60g / L.

[0056] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 25L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 100℃ suspension oven to dry for 7 hours. Then, after rolling, granulation, high-temperature calcination, and sheet forming, a high-purity low-sodium methanol synthesis catalyst is obtained.

[0057] Example 3

[0058] The only difference between this embodiment and Example 1 is that the preparation method of the high-purity, low-sodium methanol synthesis catalyst is as follows:

[0059] Step 1: At 70℃, add 1mol / L sodium hydroxide solution to 9g / L aluminum nitrate solution until the pH of the mixed solution is 7.5, and then age for 30 minutes to obtain pseudoboehmite colloid.

[0060] Step 2: Control the ultrasonic power to 60W and the ultrasonic temperature to 60℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 10000 to perform cross-flow filtration on the pseudoboehmite colloid, and perform circulation washing and backwashing to obtain desodium-free aluminum colloid. The circulation washing time and ultrasonic time are both 120min, and the water volume for circulation washing is 600ml.

[0061] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture were mixed at a flow rate ratio of 3:1, and intermittent coprecipitation was carried out under stirring at 1000r / min. The coprecipitated product was washed 5 times with deionized water to obtain the binary precursor. In this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture was 1:3, and the copper ion concentration was 60g / L.

[0062] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 30L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 100℃ suspension oven to dry for 8 hours. Then, after rolling, granulation, high-temperature calcination, and sheet forming, a high-purity low-sodium methanol synthesis catalyst is obtained.

[0063] Example 4

[0064] The only difference between this embodiment and Example 1 is that the preparation method of the high-purity, low-sodium methanol synthesis catalyst is as follows:

[0065] Step 1: At 80℃, add 2mol / L sodium hydroxide solution to 12g / L aluminum nitrate solution until the pH of the mixed solution is 8, and then age for 30 minutes to obtain pseudoboehmite colloid.

[0066] Step 2: Control the ultrasonic power to 60W and the ultrasonic temperature to 70℃. Under ultrasonic assistance, add 1000ml of boehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 10000 to perform cross-flow filtration on the boehmite colloid, and perform circulating washing and backwashing to obtain desodium-free aluminum colloid. The circulating washing time and ultrasonic time are both 150min, and the water volume for circulating washing is 800ml.

[0067] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture were mixed at a flow rate ratio of 3:1, and intermittent coprecipitation was carried out under stirring at 1500r / min. The coprecipitated product was washed 5 times with deionized water to obtain the binary precursor. In this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture was 1:4, and the copper ion concentration was 60g / L.

[0068] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 40L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 100℃ suspension oven to dry for 7 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0069] Example 5

[0070] The only difference between this embodiment and Example 1 is that the preparation method of the high-purity, low-sodium methanol synthesis catalyst is as follows:

[0071] Step 1: At 80℃, add 1 mol / L sodium hydroxide solution to 15 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0072] Step 2: Control the ultrasonic power to 80W and the ultrasonic temperature to 80℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 30000 to perform cross-flow filtration on the pseudoboehmite colloid, and perform circulation washing and backwashing to obtain desodium-free aluminum colloid. The circulation washing time and ultrasonic time are both 180min, and the water volume for circulation washing is 1000ml.

[0073] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 2000r / min; the coprecipitated product is washed 5 times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:4, and the copper ion concentration is 60g / L.

[0074] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 40L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 110℃ suspension oven to dry for 8 hours. Then, after rolling, granulation, high-temperature calcination, and sheet forming, a high-purity low-sodium methanol synthesis catalyst is obtained.

[0075] Example 6

[0076] The only difference between this embodiment and Example 1 is that the high-purity, low-sodium methanol synthesis catalyst is prepared by a method including the following steps:

[0077] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0078] Step 2: Control the ultrasonic power to 50W and the ultrasonic temperature to 50℃. Under ultrasonic assistance, add 1000ml of boehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 8000 to perform cross-flow filtration on the boehmite colloid, and perform circulating washing and backwashing to obtain desodium-aluminate colloid. The circulating washing time and ultrasonic time are both 90min, and the water volume for circulating washing is 200ml.

[0079] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0080] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 20L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 90℃ suspension oven to dry for 6 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0081] Example 7

[0082] The only difference between this embodiment and Example 6 is that the high-purity, low-sodium methanol synthesis catalyst is prepared by a method including the following steps:

[0083] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0084] Step 2: Control the ultrasonic power to 30W and the ultrasonic temperature to 50℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 8000 to perform cross-flow filtration on the pseudoboehmite colloid, and perform circulating washing and backwashing to obtain desodium-free aluminum colloid. The circulating washing time and ultrasonic time are both 90min, and the water volume for circulating washing is 200ml.

[0085] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0086] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 20L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 90℃ suspension oven to dry for 6 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0087] Example 8

[0088] The only difference between this embodiment and Example 6 is that the high-purity, low-sodium methanol synthesis catalyst is prepared by a method including the following steps:

[0089] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0090] Step 2: Control the ultrasonic power to 50W and the ultrasonic temperature to 40℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 8000 to perform cross-flow filtration on the pseudoboehmite colloid, and perform circulation washing and backwashing to obtain desodium-free aluminum colloid. The circulation washing time and ultrasonic time are both 90min, and the water volume for circulation washing is 200ml.

[0091] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0092] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 20L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 90℃ suspension oven to dry for 6 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0093] Example 9

[0094] The only difference between this embodiment and Example 6 is that the high-purity, low-sodium methanol synthesis catalyst is prepared by a method including the following steps:

[0095] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0096] Step 2: Control the ultrasonic power to 50W and the ultrasonic temperature to 50℃. Under ultrasonic assistance, add 1000ml of boehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 5000 to perform cross-flow filtration on the boehmite colloid, and perform circulating washing and backwashing to obtain desodium-free aluminum colloid. The circulating washing time and ultrasonic time are both 90min, and the water volume for circulating washing is 200ml.

[0097] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0098] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 20L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 90℃ suspension oven to dry for 6 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0099] Example 10

[0100] The only difference between this embodiment and Example 6 is that the high-purity, low-sodium methanol synthesis catalyst is prepared by a method including the following steps:

[0101] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0102] Step 2: Control the ultrasonic power to 50W and the ultrasonic temperature to 50℃. Under ultrasonic assistance, add 1000ml of pseudoboehmite colloid into a membrane separation device with backwashing function. Using the membrane separation device, use a PES membrane with a molecular weight of 10000 to perform cross-flow filtration on the pseudoboehmite colloid, and perform circulating washing and backwashing to obtain desodium-free aluminum colloid. The circulating washing time and ultrasonic time are both 90min, and the water volume for circulating washing is 200ml.

[0103] Step 3: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0104] Step 4: Put the desodium-free aluminum gel and the binary precursor into a three-in-one filter for pulping, age for 30 minutes, then wash with 20L of deionized water to remove sodium, filter under pressure, and place the filter cake in a 90℃ suspension oven to dry for 6 hours. Then, it is granulated by rolling, calcined at high temperature, and formed into tablets to obtain a high-purity, low-sodium methanol synthesis catalyst.

[0105] Comparative Example

[0106] Comparative Example 1

[0107] The only difference between this comparative example and Example 1 is that the preparation method of the methanol synthesis catalyst is as follows:

[0108] Step 1: At 40℃, add 1 mol / L sodium hydroxide solution to 3 g / L aluminum nitrate solution until the pH of the mixed solution is 7, and then age for 30 min to obtain pseudoboehmite colloid.

[0109] Step 2: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture are mixed at a flow rate ratio of 3:1, and intermittent coprecipitation is carried out under stirring at 500r / min; the coprecipitated product is washed three times with deionized water to obtain the binary precursor; in this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:1, and the copper ion concentration is 60g / L.

[0110] Step 3: Mix the pseudoboehmite colloid and the binary precursor into a slurry, age for 30 minutes, wash and remove sodium again by vacuum filtration, place the filter cake in a 90℃ suspension oven to dry for 6 hours, and then granulate, calcine at high temperature, and form into flakes to obtain the methanol synthesis catalyst.

[0111] Comparative Example 2

[0112] The only difference between this comparative example and Example 4 is that the preparation method of the methanol synthesis catalyst is as follows:

[0113] Step 1: At 80℃, add 2mol / L sodium hydroxide solution to 12g / L aluminum nitrate solution until the pH of the mixed solution is 8, and then age for 30 minutes to obtain pseudoboehmite colloid.

[0114] Step 2: Under the action of a 200psi high-pressure infusion pump, 3L of 1mol / L sodium carbonate solution and 1L of copper-zinc mixture were mixed at a flow rate ratio of 3:1, and intermittent coprecipitation was carried out under stirring at 1500r / min. The coprecipitated product was washed 5 times with deionized water to obtain the binary precursor. In this embodiment, the mass ratio of zinc ions to copper ions in the copper-zinc mixture was 1:4, and the copper ion concentration was 60g / L.

[0115] Step 3: Mix the pseudoboehmite colloid and the binary precursor into a slurry, age for 30 minutes, wash and remove sodium again by vacuum filtration, place the filter cake in a 100℃ suspension oven to dry for 7 hours, and then granulate, calcine at high temperature, and form into flakes to obtain the methanol synthesis catalyst.

[0116] Performance testing

[0117] Take methanol synthesis catalyst samples from Examples 1-5 and Comparative Examples 1-2, place them in a reducing atmosphere, which includes 95% nitrogen and 5% hydrogen by volume percentage; heat to 230°C and reduce for 12 hours to activate the methanol synthesis catalyst samples.

[0118] The activated methanol synthesis catalyst sample was tested as follows:

[0119] Test 1: The specific surface area, pore volume, average pore size, and sodium content of each methanol synthesis catalyst sample were measured. The specific surface area was measured using the BET method, the pore volume and average pore size were measured using the BJH method, and the sodium content was measured using atomic absorption spectrometry. The test results are summarized in Table 1.

[0120] Test 2: Each methanol synthesis catalyst was added to a reactor, and synthesis gas was introduced. The synthesis gas consisted of the following components in molar percentage: carbon monoxide 14%, carbon dioxide 4%, hydrogen 60%, and the balance nitrogen. The initial activity and reaction selectivity of each methanol synthesis catalyst were tested, and the ethanol content, methyl formate content, and total impurity content in the mixed gas after the reaction were also tested. The activated methanol synthesis catalyst was then treated at 400℃ for 5 hours, and then added to the reactor again and synthesis gas was introduced. The activity of the methanol synthesis catalyst after the heat treatment was tested.

[0121] Catalyst activity is defined as the amount of methanol (g) synthesized per unit time (h) and per unit volume of catalyst (ml); selectivity is defined as the mass percentage of methanol in the total gas after the catalytic reaction is complete; methanol content, ethanol content, methyl formate content, and total impurity content are determined by gas chromatography; the results are summarized in Table 2.

[0122] Table 1

[0123]

[0124]

[0125] Table 2

[0126]

[0127] As can be seen from Examples 1-5, Comparative Examples 1-2 and Table 1, the method disclosed in this application, which uses an ultrafiltration membrane to filter the pseudoboehmite colloid and combines it with ultrasonic assistance, backwashing, and circulating washing, can significantly reduce the sodium content of the methanol synthesis catalyst, ensuring that the sodium content of the methanol synthesis catalyst is no higher than 650 ppm, and can reach as low as 489 ppm. Furthermore, it has better specific surface area, pore volume, and average pore size.

[0128] As can be seen from Examples 1-5, Comparative Examples 1-2, and Table 2, the methanol synthesis catalyst prepared according to the method disclosed in this application exhibits improved initial activity, selectivity, and catalytic activity after heat treatment. The contents of the main impurities, ethanol and methyl formate, are significantly reduced, as is the total impurity content. This may be because the reduced sodium content in the methanol synthesis catalyst helps decrease the yield of byproducts. The preparation method disclosed in this application provides more loading sites for the copper-zinc active components and improves the dispersibility of the active components. Simultaneously, the increased specific surface area of ​​the catalyst also promotes improved catalytic activity and selectivity.

[0129] As can be seen from Examples 1-5 and Tables 1-2, by controlling the membrane molecular weight of the ultrafiltration membrane and the ultrasonic treatment conditions, the specific surface area, pore volume, pore size, and sodium impurity content of the methanol synthesis catalyst can be adjusted, thereby adjusting the catalytic effect of the methanol synthesis catalyst.

[0130] Based on Examples 1, 2, 6-10 and Table 1, it can be seen that when a PES membrane with a molecular weight of 8000 is selected and the ultrasonic power is controlled at 50W and the ultrasonic temperature at 50℃, the methanol synthesis catalyst exhibits the best overall performance, better initial activity, better heat resistance, better selectivity, and lower impurity content.

[0131] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a high-purity, low-sodium methanol synthesis catalyst, characterized in that, Includes the following steps: Aluminum nitrate and sodium hydroxide were mixed and reacted to obtain boehmite colloid; Under ultrasonic conditions, the pseudoboehmite colloid is subjected to cross-flow filtration using an ultrafiltration membrane, and the ultrafiltration membrane is backwashed while the pseudoboehmite colloid is circulated and washed to obtain desodium-free aluminum colloid. Sodium carbonate was mixed with a copper-zinc mixture for co-precipitation, and the precipitate was washed to obtain a binary precursor. The sodium-removed aluminum gel is mixed with the binary precursor, pulped, aged, and then washed to further remove sodium. After filtration, the filter cake is dried, granulated, calcined, and shaped to obtain a high-purity, low-sodium methanol catalyst.

2. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 1, characterized in that, The specific preparation method of the pseudoboehmite colloid includes: adding 1-2 mol / L sodium hydroxide solution to 3-15 g / L aluminum nitrate solution at 40-80℃ until the pH value is 7-8, and then aging to obtain pseudoboehmite colloid.

3. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 1, characterized in that, The ultrafiltration membrane is selected from one of PES membrane, PVDF membrane, and PAN membrane.

4. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 3, characterized in that, The ultrafiltration membrane is a PES membrane, and the molecular weight of the PES membrane is 5000-30000.

5. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 4, characterized in that, The ultrasonic conditions include: ultrasonic power 30-80W, ultrasonic temperature 40-80℃, and ultrasonic time 60-180min.

6. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 5, characterized in that, The PES membrane has a molecular weight of 8000, and the ultrasonic conditions are: ultrasonic power of 50W and ultrasonic temperature of 50℃.

7. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 1, characterized in that, The washing time for the circulating washing is 60-180 minutes, and the washing water volume is 200-1000 ml of water per 1000 ml of pseudoboehmite colloid.

8. The method for preparing the high-purity, low-sodium methanol synthesis catalyst according to claim 1, characterized in that, The preparation method of the binary precursor specifically includes: Under a pressure of 150-250 psi, a copper-zinc mixture and a sodium carbonate solution were mixed at a flow rate ratio of 1:3 and subjected to intermittent co-precipitation under stirring at a speed of 500-2000 r / min. The precipitate was washed with deionized water to obtain the binary precursor. The mass ratio of zinc ions to copper ions in the copper-zinc mixture is 1:(1-4), and the concentration of copper ions is 50-80 g / L; the concentration of sodium carbonate solution is 1-2 mol / L.

9. The high-purity, low-sodium methanol synthesis catalyst according to claim 1, characterized in that, The high-purity, low-sodium methanol synthesis catalyst specifically includes: mixing the desodium-aluminate gel with the binary precursor, slurrying, aging, washing with 20-40L of deionized water and filtering, drying the filter cake at 90-100℃ for 6-8h, then crushing and granulating, calcining, and forming into sheets.

10. A high-purity, low-sodium methanol synthesis catalyst, characterized in that, It is prepared by the method described in any one of claims 1-9 for the preparation of high-purity, low-sodium methanol synthesis catalyst; The high-purity, low-sodium methanol synthesis catalyst includes a boehmite support and copper-zinc active components dispersed on the boehmite support; and the sodium content of the high-purity, low-sodium methanol synthesis catalyst is not higher than 645 ppm.

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