Modified hogalite catalysts and methods for making the same
A modified hogallat catalyst with high water resistance and low-temperature activity was prepared by complexation precipitation and hydrophobic modification, which solved the problems of poor water resistance and low catalytic activity of hogallat catalyst at low temperature, and achieved efficient CO conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI HENGYE MOLECULAR SIEVE CO LTD
- Filing Date
- 2026-04-28
- Publication Date
- 2026-07-07
AI Technical Summary
Existing hogallat catalysts suffer from poor water resistance, low low-temperature catalytic activity, and poor catalytic efficiency, making it difficult to effectively treat high volume concentrations of CO.
Modified Hogarat catalysts were prepared by complexation precipitation method. Nano-boron carbide and nano-molybdenum carbide were used as co-precipitation nuclei, and the metal ion precipitation process was controlled by aqueous solutions of phytic acid, tannic acid, polyethyleneimine and guanidine. Subsequently, hydrophobic modification was performed to improve the low-temperature activity and water resistance of the catalyst.
It achieves high water resistance and low-temperature catalytic activity. The catalyst maintains excellent CO conversion performance even after long-term operation under high water vapor conditions. The initial T100 is 7~15℃, and the T100 after 1000h of continuous operation is 10~20℃.
Smart Images
Figure CN122098643B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to modified hogallat catalysts and their preparation methods, belonging to the field of catalyst technology. Background Technology
[0002] Carbon monoxide (CO) is a toxic gaseous pollutant widely distributed in industrial kiln exhaust, coking tail gas, boiler combustion emissions, and motor vehicle exhaust. CO poses a serious threat to the environment and human health. Therefore, the research and development of efficient CO removal technologies has significant environmental and social value.
[0003] To effectively control CO, researchers have developed various removal methods, mainly including physical and chemical methods. Physical methods rely on the surface adsorption properties of porous materials to separate and enrich CO. In contrast, chemical catalytic oxidation promotes the complete oxidation reaction of CO and O2 under mild conditions (usually <300℃) through the action of a catalyst: 2CO + O2 → 2CO2. Chemical catalytic oxidation has advantages such as high efficiency, low energy consumption, and no secondary pollution, and has become the most promising CO control technology. In recent years, researchers have focused on developing catalysts with higher CO oxidation performance. Currently, CO catalytic oxidation catalysts can be divided into two main categories based on the difference in active components: noble metals and non-noble metals. Noble metal catalysts are mainly composed of platinum (Pt), palladium (Pd), and gold (Au), and their excellent low-temperature activity and stability have been widely verified in the field of CO catalytic oxidation. However, these catalysts are expensive and difficult to widely promote and apply. On the other hand, non-noble metal catalysts have attracted much attention due to their low cost and tunable redox properties. Among non-precious metal catalysts, hopcalite catalysts, which have high CO removal efficiency and very low cost, are the most widely used. However, commercially available hopcalite catalysts still have two major problems: first, poor water resistance (generally requiring the use of a desiccant under relative humidity greater than 10%, and easily poisoned and ineffective when relative humidity exceeds 45%); and second, low catalytic activity at low temperatures, which leads to a significant reduction in CO removal rate at low temperatures. Therefore, there is an urgent need to develop hopcalite catalysts with good water resistance and high catalytic activity at low temperatures to meet the application requirements of low-cost and high-efficiency CO removal.
[0004] Chinese patent application CN107537515A discloses a supported copper-manganese catalyst, its preparation method, and its application in low-temperature catalytic oxidation of CO. The supported copper-manganese catalyst prepared in this patent is a modified hogallat catalyst. The specific preparation method involves mixing cerium dioxide with an impregnation solution containing copper and manganese salts to obtain a mixture; drying the mixture to obtain a catalyst precursor; and calcining the catalyst precursor to obtain the supported copper-manganese catalyst. This catalyst includes a cerium dioxide support and active components supported on the support, wherein the active components are copper oxide and manganese dioxide. The supported copper-manganese catalyst obtained in this patent achieves a CO conversion rate of only 50% in the temperature range of 40–90°C, indicating relatively low low-temperature catalytic activity. Furthermore, this patent does not address the catalyst's water resistance.
[0005] Chinese patent application CN117299146A discloses a modified hogalata catalyst and its preparation method. The modified hogalata comprises the following components by mass percentage: hogalata: 85-97%; modifier: 3-15%; the modifier is one of potassium hydroxide, sodium hydroxide, or lithium hydroxide, and the modifier is coated on the outer surface of the hogalata. The modified hogalata catalyst prepared by this patent shows good removal efficiency for trace amounts of CO, but its removal efficiency for higher volume concentrations of CO has not been verified. It is possible that the catalytic efficiency of the modified hogalata catalyst obtained by this patent is not very high, making it difficult to handle high volume concentrations of CO.
[0006] As can be seen above, the current hoggarat catalyst still suffers from prominent problems such as poor water resistance, low low-temperature catalytic activity, and poor catalytic efficiency. Therefore, developing a modified hoggarat catalyst with high water resistance, high low-temperature activity, and high catalytic efficiency has very practical application value. Summary of the Invention
[0007] To address the shortcomings of the existing technology, this invention provides a modified hogallat catalyst and its preparation method, achieving the following objective: to prepare a modified hogallat catalyst with high water resistance, high low-temperature activity, and high catalytic efficiency.
[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:
[0009] A modified hogallat catalyst and its preparation method, wherein the preparation method of the modified hogallat catalyst includes three steps: preparation of mother liquor, complexation precipitation, and hydrophobic modification;
[0010] The following are further improvements to the above technical solution:
[0011] Step 1: Prepare the mother liquor
[0012] Copper salt, manganese salt, cerium salt, and ZrOCl2·8H2O were added to deionized water and dissolved completely. Then, polyvinylpyrrolidone K30 was added and dissolved completely. Under strong stirring and dispersion, nano boron carbide and nano molybdenum carbide were slowly added. After the addition was completed, strong stirring and dispersion were continued to obtain the mother liquor.
[0013] The copper salt is one or a mixture of any two or more of copper sulfate, copper nitrate, and copper chloride in any mass ratio.
[0014] The manganese salt is one or a mixture of any two or more of manganese sulfate, manganese nitrate, and manganese chloride in any mass ratio.
[0015] The cerium salt is one or a mixture of any two or more of cerium sulfate, cerium nitrate, and cerium chloride in any mass ratio.
[0016] The particle size of the boron carbide nanoparticles is 10~100nm;
[0017] The particle size of the nano-molybdenum carbide is 10~100nm;
[0018] The mass ratio of the copper salt, manganese salt, cerium salt, ZrOCl2·8H2O, deionized water, polyvinylpyrrolidone K30, nano boron carbide, and nano molybdenum carbide is 20~80:8~70:5~20:80~170:400~700:0.1~0.4:0.5~2:1.5~5;
[0019] The high-intensity stirring and dispersion has a dispersion rate of 8000~13000 rpm;
[0020] Continue vigorous stirring to disperse evenly for 5-9 hours.
[0021] Step 2, Complexation Precipitation
[0022] The mother liquor was heated to the reaction temperature, and a mixed acid aqueous solution was slowly added dropwise while stirring continuously. The dropping rate was controlled to avoid the formation of gels or precipitates. After the addition was completed, stirring was continued until the complexation was complete. Then, a polyethyleneimine aqueous solution and a guanidine aqueous solution were added dropwise to the mother liquor at the same time. The dropping rates of both were controlled to keep the pH value of the mother liquor constant. After the addition was completed, stirring was continued until the reaction was complete. The mixture was then cooled to room temperature, and after aging, filtration, washing with water, drying, and calcination, the catalyst powder was obtained.
[0023] The mixed acid aqueous solution is composed of phytic acid, tannic acid, and deionized water.
[0024] The mass ratio of phytic acid, tannic acid and deionized water is 10~50:70~180:260~600;
[0025] The polyethyleneimine aqueous solution contains polyethyleneimine at a mass concentration of 8-20 wt%.
[0026] The guanidine aqueous solution has a guanidine concentration of 6-13 wt%.
[0027] The mass ratio of the mother liquor, mixed acid aqueous solution, polyethyleneimine aqueous solution, and guanidine aqueous solution is 60~280:20~90:5~14:25~75;
[0028] The reaction temperature is 50~70℃;
[0029] The continuous stirring is carried out at a speed of 500-900 rpm.
[0030] Continue stirring until complete complexation, for a period of 2-5 hours;
[0031] The pH value is kept constant, ranging from 9 to 10.
[0032] The stirring is continued until the reaction is complete, and the stirring time is 3 to 7 hours.
[0033] The aging process takes 14 to 20 hours.
[0034] The water washing process involves washing the filtered solids with deionized water 3-4 times, with the mass of deionized water used in each wash being equal to the mass of the filtered solids.
[0035] The drying process involves a drying temperature of 70-95℃ and a drying time of 13-19 hours.
[0036] The roasting process involves a roasting temperature of 450-580℃ and a roasting time of 2-5 hours.
[0037] Step 3: Hydrophobic modification
[0038] The catalyst powder was placed in an aqueous solution of methylsilicate, stirred and dispersed evenly, filtered, and the filtered solid was dried, washed and dried again to obtain the modified hogalat catalyst.
[0039] The methylsilicate is one or a mixture of two of potassium methylsilicate and sodium methylsilicate in any mass ratio;
[0040] The methylsilicate aqueous solution contains 1-2 wt% methylsilicate.
[0041] The mass ratio of the catalyst powder to the aqueous methylsilicate solution is 30~77:180;
[0042] The stirring and dispersion are uniform, with a stirring speed of 2000~4000 rpm and a dispersion time of 30~50 minutes;
[0043] The drying process involves a drying temperature of 80-90℃ and a drying time of 1.5-4 hours.
[0044] The washing process involves washing the dried solid with deionized water 4-5 times, with the mass of deionized water used in each wash being equal to the mass of the dried solid.
[0045] The secondary drying process involves a drying temperature of 85-95℃ and a drying time of 12-20 hours.
[0046] Compared with the prior art, the present invention achieves the following beneficial effects:
[0047] 1. This invention prepares a modified Hogarat catalyst using a complexation precipitation method. In order to promote the low-temperature catalytic activity of the main metal oxide components in the Hogarat catalyst (the main metal oxide components in this invention are copper oxide, manganese oxide, cerium oxide, and zirconium oxide), this invention uses the following three methods to precisely control the complexation precipitation process of metal oxides, so as to maximize the uniformity of the precipitation process of various metal ions, and thus ensure the maximum fineness of the corresponding metal oxide crystals after calcination. The three methods are as follows: (1) Adding nano-boron carbide and nano-molybdenum carbide as co-precipitation nuclei, so that various metal ions can carry out complexation precipitation reactions around the nano-nuclei. In this way, the disorder of the complexation precipitation reaction can be improved and the metal ions can be avoided. The disordered and rapid aggregation and precipitation of the particles, and the crystal nuclei of the nano-sized particles can exponentially increase the number of precipitate particles, which can both increase the specific surface area of the precipitate microparticles formed during the complex precipitation process and reduce the size of the precipitate microparticles; (2) a strong complexing agent composed of phytic acid and tannic acid is used to control the decomplexation rate of metal ions, thereby controlling the precipitation rate of metal ions; (3) a water solution of polyethyleneimine and a water solution of guanidine are used to control the pH value and precipitation rate of the reaction system. The water solution of polyethyleneimine has a large viscosity, which can limit the movement speed of metal ions and reduce the precipitation rate of metal ions. The water solution of guanidine has a strong pH buffering capacity, so it can ensure that the pH value of the reaction system is more stable, which will make the precipitation reaction rate more uniform and stable. Under the combined effect of the above three methods, the present invention achieves precise control of the complex precipitation reaction, and thus can obtain a modified Hogarat catalyst with very high low-temperature catalytic activity;
[0048] 2. In addition to serving as nuclei for the co-precipitation reaction, the nano-boron carbide and nano-molybdenum carbide added in this invention also have certain catalytic effects and co-catalytic effects that accelerate charge transfer. Both nano-boron carbide and nano-molybdenum carbide are conductive. After metal ions precipitate on these two nano-powders and are calcined into metal oxides, the conductivity of nano-boron carbide and nano-molybdenum carbide can promote charge transfer between metal oxides and CO during the catalytic conversion of CO to CO2, thus significantly increasing the conversion rate of CO to CO2. Especially under low temperature conditions, the promoting effect of this charge transfer effect is more obvious. Therefore, the modified Hogarth catalyst obtained by this invention has excellent low-temperature catalytic activity.
[0049] 3. The nano-boron carbide and nano-molybdenum carbide added in this invention have a certain effect on improving the water resistance of the modified hoggarat catalyst. The specific reason may be the hydrophobicity and catalytic performance of these two nano-carbides themselves. Their hydrophobicity may improve the overall hydrophobicity of the modified hoggarat catalyst. It is also possible that after water vapor penetrates into the nano-boron carbide and nano-molybdenum carbide, these two substances may inhibit the reaction between metal oxides and water molecules by forming certain intermediate phase products, thus preventing the metal oxides from losing their catalytic activity prematurely due to water erosion.
[0050] 4. In this invention, methylsilicate is used to hydrophobically modify the hogallat catalyst. Methylsilicate has strong permeability and can form a breathable but water-impermeable nano-scale film on the surface of inorganic materials. Based on this property of methylsilicate, the hydrophobically modified hogallat catalyst obtained in this invention has very strong hydrophobicity on the catalyst surface without affecting the contact between CO gas and the catalytically active substance. Therefore, the modified hogallat catalyst obtained in this invention has excellent water resistance and can maintain the catalyst's long-lasting water resistance during long-term operation.
[0051] 5. The modified hogallat catalyst obtained by this invention has an initial T100 of 7~15℃ and a T100 of 10~20℃ after continuous operation for 1000h. Attached Figure Description
[0052] Figure 1 The surface of the modified hogallat catalyst obtained in Example 1 is shown in a scanning electron microscope image magnified 10,000 times.
[0053] Figure 2 The modified hogallat catalyst obtained in Example 2 is shown in a scanning electron microscope image magnified 10,000 times.
[0054] Figure 3 The modified hogallat catalyst obtained in Example 3 is shown in a scanning electron microscope image magnified 10,000 times.
[0055] Figure 4 Transmission electron microscope image at 10,000x magnification of the modified hogallat catalyst obtained in Example 1;
[0056] Figure 5 Transmission electron microscope image at 10,000x magnification of the modified hogallat catalyst obtained in Example 2;
[0057] Figure 6 The image shown is a transmission electron microscope (TEM) image of the modified hogallat catalyst obtained in Example 3, magnified 10,000 times. Detailed Implementation
[0058] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0059] Example 1: Preparation method of modified hogallat catalyst
[0060] Step 1: Prepare the mother liquor
[0061] Copper salt, manganese salt, cerium salt, and ZrOCl2·8H2O were added to deionized water and dissolved completely. Then, polyvinylpyrrolidone K30 was added and dissolved completely. Under strong stirring and dispersion, nano boron carbide and nano molybdenum carbide were slowly added. After the addition was completed, strong stirring and dispersion were continued to obtain the mother liquor.
[0062] The copper salt is copper sulfate;
[0063] The manganese salt is manganese sulfate;
[0064] The cerium salt is cerium sulfate;
[0065] The particle size of the boron carbide nanoparticles is 40 nm;
[0066] The particle size of the molybdenum carbide nanoparticles is 50 nm;
[0067] The mass ratio of the copper salt, manganese salt, cerium salt, ZrOCl2·8H2O, deionized water, polyvinylpyrrolidone K30, nano boron carbide, and nano molybdenum carbide is 60:20:11:120:600:0.3:1:3.
[0068] The high-intensity stirring and dispersion has a dispersion rate of 11,000 rpm;
[0069] Continue vigorous stirring to disperse evenly for 6 hours.
[0070] Step 2, Complexation Precipitation
[0071] The mother liquor was heated to the reaction temperature, and a mixed acid aqueous solution was slowly added dropwise while stirring continuously. The dropping rate was controlled to avoid the formation of gels or precipitates. After the addition was completed, stirring was continued until the complexation was complete. Then, a polyethyleneimine aqueous solution and a guanidine aqueous solution were added dropwise to the mother liquor at the same time. The dropping rates of both were controlled to keep the pH value of the mother liquor constant. After the addition was completed, stirring was continued until the reaction was complete. The mixture was then cooled to room temperature, and after aging, filtration, washing with water, drying, and calcination, the catalyst powder was obtained.
[0072] The mixed acid aqueous solution is composed of phytic acid, tannic acid, and deionized water.
[0073] The mass ratio of phytic acid, tannic acid and deionized water is 30:120:450.
[0074] The polyethyleneimine aqueous solution contains 15 wt% polyethyleneimine.
[0075] The aqueous solution of guanidine has a guanidine concentration of 11 wt%.
[0076] The mass ratio of the mother liquor, mixed acid aqueous solution, polyethyleneimine aqueous solution, and guanidine aqueous solution is 140:60:9:50.
[0077] The reaction temperature is 65°C;
[0078] The continuous stirring is carried out at a stirring rate of 800 revolutions per minute.
[0079] Continue stirring until complete complexation, for a total of 4 hours;
[0080] The pH value remains constant at 9.5.
[0081] The stirring continues until the reaction is complete, and the stirring time is 6 hours.
[0082] The aging process lasts for 18 hours.
[0083] The water washing process involves washing the filtered solids three times with deionized water, with the mass of deionized water used in each wash being equal to the mass of the filtered solids.
[0084] The drying process is carried out at a temperature of 90°C for 17 hours.
[0085] The roasting process is carried out at a temperature of 500°C for 4 hours.
[0086] Step 3: Hydrophobic modification
[0087] The catalyst powder was placed in an aqueous solution of methylsilicate, stirred and dispersed evenly, filtered, and the filtered solid was dried, washed and dried again to obtain the modified hogalat catalyst.
[0088] The methylsilicate is potassium methylsilicate;
[0089] The methylsilicate aqueous solution has a methylsilicate mass concentration of 1.3 wt%.
[0090] The mass ratio of the catalyst powder to the aqueous methylsilicate solution is 60:180;
[0091] The stirring and dispersing were carried out evenly at a stirring speed of 3000 rpm for 45 minutes.
[0092] The drying process is carried out at a temperature of 87°C for 3 hours.
[0093] The washing process involves washing the dried solid with deionized water four times, with the mass of deionized water used in each wash being equal to the mass of the dried solid.
[0094] The secondary drying process involves a drying temperature of 90°C and a drying time of 16 hours.
[0095] Example 2: Preparation method of modified hogallat catalyst
[0096] Step 1: Prepare the mother liquor
[0097] Copper salt, manganese salt, cerium salt, and ZrOCl2·8H2O were added to deionized water and dissolved completely. Then, polyvinylpyrrolidone K30 was added and dissolved completely. Under strong stirring and dispersion, nano boron carbide and nano molybdenum carbide were slowly added. After the addition was completed, strong stirring and dispersion were continued to obtain the mother liquor.
[0098] The copper salt is copper nitrate;
[0099] The manganese salt is manganese nitrate;
[0100] The cerium salt is cerium nitrate;
[0101] The particle size of the boron carbide nanoparticles is 10 nm;
[0102] The particle size of the molybdenum carbide nanoparticles is 10 nm;
[0103] The mass ratio of the copper salt, manganese salt, cerium salt, ZrOCl2·8H2O, deionized water, polyvinylpyrrolidone K30, nano boron carbide, and nano molybdenum carbide is 20:8:5:80:400:0.1:0.5:1.5.
[0104] The vigorous stirring and dispersion has a dispersion rate of 8000 rpm.
[0105] Continue vigorous stirring to disperse evenly for 5 hours.
[0106] Step 2, Complexation Precipitation
[0107] The mother liquor was heated to the reaction temperature, and a mixed acid aqueous solution was slowly added dropwise while stirring continuously. The dropping rate was controlled to avoid the formation of gels or precipitates. After the addition was completed, stirring was continued until the complexation was complete. Then, a polyethyleneimine aqueous solution and a guanidine aqueous solution were added dropwise to the mother liquor at the same time. The dropping rates of both were controlled to keep the pH value of the mother liquor constant. After the addition was completed, stirring was continued until the reaction was complete. The mixture was then cooled to room temperature, and after aging, filtration, washing with water, drying, and calcination, the catalyst powder was obtained.
[0108] The mixed acid aqueous solution is composed of phytic acid, tannic acid, and deionized water.
[0109] The mass ratio of phytic acid, tannic acid and deionized water is 10:70:260.
[0110] The polyethyleneimine aqueous solution contains 8 wt% polyethyleneimine.
[0111] The aqueous solution of guanidine has a guanidine concentration of 6 wt%.
[0112] The mass ratio of the mother liquor, mixed acid aqueous solution, polyethyleneimine aqueous solution, and guanidine aqueous solution is 60:20:5:25.
[0113] The reaction temperature is 50°C;
[0114] The continuous stirring is carried out at a stirring speed of 500 revolutions per minute.
[0115] Continue stirring until complete complexation, for a total stirring time of 2 hours;
[0116] The pH value remains constant at 9.
[0117] The stirring is continued until the reaction is complete, and the stirring time is 3 hours.
[0118] The aging process lasts for 14 hours.
[0119] The water washing process involves washing the filtered solids three times with deionized water, with the mass of deionized water used in each wash being equal to the mass of the filtered solids.
[0120] The drying process is carried out at a temperature of 70°C for 13 hours.
[0121] The roasting process is carried out at a temperature of 450°C for 2 hours.
[0122] Step 3: Hydrophobic modification
[0123] The catalyst powder was placed in an aqueous solution of methylsilicate, stirred and dispersed evenly, filtered, and the filtered solid was dried, washed and dried again to obtain the modified hogalat catalyst.
[0124] The methylsilicate is sodium methylsilicate;
[0125] The methylsilicate aqueous solution has a methylsilicate mass concentration of 1 wt%.
[0126] The mass ratio of the catalyst powder to the aqueous methylsilicate solution is 30:180;
[0127] The stirring and dispersion were carried out evenly at a stirring speed of 2000 rpm for 30 minutes.
[0128] The drying process is carried out at a temperature of 80°C for 1.5 hours.
[0129] The washing process involves washing the dried solid with deionized water four times, with the mass of deionized water used in each wash being equal to the mass of the dried solid.
[0130] The secondary drying process involves a drying temperature of 85°C and a drying time of 12 hours.
[0131] Example 3: Preparation method of modified hogallat catalyst
[0132] Step 1: Prepare the mother liquor
[0133] Copper salt, manganese salt, cerium salt, and ZrOCl2·8H2O were added to deionized water and dissolved completely. Then, polyvinylpyrrolidone K30 was added and dissolved completely. Under strong stirring and dispersion, nano boron carbide and nano molybdenum carbide were slowly added. After the addition was completed, strong stirring and dispersion were continued to obtain the mother liquor.
[0134] The copper salt is copper chloride;
[0135] The manganese salt is manganese chloride;
[0136] The cerium salt is cerium chloride;
[0137] The particle size of the boron carbide nanoparticles is 100 nm;
[0138] The particle size of the molybdenum carbide nanoparticles is 100 nm;
[0139] The mass ratio of the copper salt, manganese salt, cerium salt, ZrOCl2·8H2O, deionized water, polyvinylpyrrolidone K30, nano boron carbide, and nano molybdenum carbide is 80:70:20:170:700:0.4:2:5.
[0140] The high-intensity stirring and dispersion has a dispersion rate of 13,000 rpm;
[0141] Continue vigorous stirring to disperse evenly for 9 hours.
[0142] Step 2, Complexation Precipitation
[0143] The mother liquor was heated to the reaction temperature, and a mixed acid aqueous solution was slowly added dropwise while stirring continuously. The dropping rate was controlled to avoid the formation of gels or precipitates. After the addition was completed, stirring was continued until the complexation was complete. Then, a polyethyleneimine aqueous solution and a guanidine aqueous solution were added dropwise to the mother liquor at the same time. The dropping rates of both were controlled to keep the pH value of the mother liquor constant. After the addition was completed, stirring was continued until the reaction was complete. The mixture was then cooled to room temperature, and after aging, filtration, washing with water, drying, and calcination, the catalyst powder was obtained.
[0144] The mixed acid aqueous solution is composed of phytic acid, tannic acid, and deionized water.
[0145] The mass ratio of phytic acid, tannic acid and deionized water is 50:180:600.
[0146] The polyethyleneimine aqueous solution contains 20 wt% polyethyleneimine.
[0147] The aqueous solution of guanidine has a guanidine concentration of 13 wt%.
[0148] The mass ratio of the mother liquor, mixed acid aqueous solution, polyethyleneimine aqueous solution, and guanidine aqueous solution is 280:90:14:75.
[0149] The reaction temperature is 70°C;
[0150] The continuous stirring is carried out at a stirring rate of 900 revolutions per minute.
[0151] Continue stirring until complete complexation, for a total of 5 hours;
[0152] The pH value remains constant at 10.
[0153] The stirring continues until the reaction is complete, and the stirring time is 7 hours.
[0154] The aging process lasts for 20 hours.
[0155] The water washing process involves washing the filtered solids four times with deionized water, with the mass of deionized water used in each wash being equal to the mass of the filtered solids.
[0156] The drying process involves a drying temperature of 95°C and a drying time of 19 hours.
[0157] The roasting process is carried out at a temperature of 580°C for 5 hours.
[0158] Step 3: Hydrophobic modification
[0159] The catalyst powder was placed in an aqueous solution of methylsilicate, stirred and dispersed evenly, filtered, and the filtered solid was dried, washed and dried again to obtain the modified hogalat catalyst.
[0160] The methylsilicate is potassium methylsilicate;
[0161] The methylsilicate aqueous solution has a methylsilicate mass concentration of 2 wt%.
[0162] The mass ratio of the catalyst powder to the aqueous methylsilicate solution is 77:180;
[0163] The stirring and dispersion were carried out evenly at a stirring speed of 4000 rpm for 50 minutes.
[0164] The drying process is carried out at a temperature of 90°C for 4 hours.
[0165] The washing process involves washing the dried solid with deionized water five times, with the mass of deionized water used in each wash being equal to the mass of the dried solid.
[0166] The secondary drying process involves a drying temperature of 95°C and a drying time of 20 hours.
[0167] Comparative Example 1: Based on Example 1, in step 1, the preparation of the mother liquor was carried out without adding nano-boron carbide and nano-molybdenum carbide. Instead, 1 part of nano-boron carbide and 3 parts of nano-molybdenum carbide were replaced with 4 parts of deionized water in equal amounts. The specific operation is as follows:
[0168] Step 1: Prepare the mother liquor
[0169] Replace 1 part of nano boron carbide and 3 parts of nano molybdenum carbide with 4 parts of deionized water, and perform the other operations as in Example 1;
[0170] Steps 2 and 3 are the same as in Example 1.
[0171] Comparative Example 2: Based on Example 1, in step 1, the preparation of the mother liquor was carried out without adding boron carbide nanoparticles. Instead, 1 part of boron carbide nanoparticles was replaced with 1 part of deionized water. The specific operation is as follows:
[0172] Step 1: Prepare the mother liquor
[0173] Replace 1 part of nano boron carbide with 1 part of deionized water, and perform the other operations as in Example 1;
[0174] Steps 2 and 3 are the same as in Example 1.
[0175] Comparative Example 3: Based on Example 1, in step 1, the preparation of the mother liquor was carried out without adding nano-molybdenum carbide. Instead, 3 parts of nano-molybdenum carbide were replaced with 3 parts of deionized water in equal amounts. The specific operation is as follows:
[0176] Step 1: Prepare the mother liquor
[0177] Replace 3 parts of nano-molybdenum carbide with 3 parts of deionized water, and perform the other operations as in Example 1;
[0178] Steps 2 and 3 are the same as in Example 1.
[0179] Comparative Example 4: Based on Example 1, in step 2, complexation precipitation, 60 parts of mixed acid aqueous solution were replaced with 60 parts of oxalic acid aqueous solution. The mass ratio of oxalic acid to deionized water in the oxalic acid aqueous solution was 150:450. The specific operation is as follows:
[0180] Step 1 is the same as in Example 1;
[0181] Step 2, Complexation Precipitation
[0182] Replace 60 parts of mixed acid aqueous solution with 60 parts of oxalic acid aqueous solution, and perform the other operations as in Example 1;
[0183] The mass ratio of oxalic acid to deionized water in the oxalic acid aqueous solution is 150:450.
[0184] Step 3 is the same as in Example 1.
[0185] Comparative Example 5: Based on Example 1, in step 2, the complexation precipitation, with the pH of the mother liquor kept constant at 9.5 during the reaction, 9 parts of polyethyleneimine aqueous solution and 50 parts of guanidine aqueous solution were replaced with 46 parts of ammonia water with a mass concentration of 12wt%. The specific operation is as follows:
[0186] Step 1 is the same as in Example 1;
[0187] Step 2, Complexation Precipitation
[0188] Replace 9 parts of polyethyleneimine aqueous solution and 50 parts of guanidine aqueous solution with 45 parts of ammonia solution with a mass concentration of 12wt%, and perform the other operations as in Example 1.
[0189] Step 3 is the same as in Example 1.
[0190] Comparative Example 6: Based on Example 1, without performing step 3 (hydrophobic modification) and step 2 (complex precipitation), the modified hogalat catalyst was directly obtained. The specific operation is as follows:
[0191] Step 1 is the same as in Example 1;
[0192] Step 2, Complexation Precipitation
[0193] The procedure was the same as in Example 1, and the modified hogalat catalyst was obtained directly;
[0194] Step 3, hydrophobic modification, is not performed.
[0195] Catalyst performance testing:
[0196] The modified hogallat catalysts obtained in Examples 1-3 and Comparative Examples 1-6 were evaluated for their catalytic activity in removing CO in a fixed-bed reactor. The reactor was a quartz reaction tube with an inner diameter of 8 mm. The catalyst dosage was 100 mg, in powder form. The feed gas composition (volume ratio) was 3% CO, 20% O2, 10% or 30% H2O, and the remainder was equilibrium gas N2. The mass hourly space velocity of the feed gas was 600 L / (g·h), and the pressure was atmospheric pressure. The CO content in the gas before and after the reaction was analyzed by gas chromatography. The reaction temperature was gradually decreased from high to low. The lowest temperature at which CO was completely converted and remained stable for 15 min was taken as the minimum complete conversion temperature, denoted as T100. The initial T100 of the freshly prepared modified hogallat catalyst and the T100 after 1000 h of continuous operation were tested. The test results are shown in Table 1.
[0197] Table 1
[0198]
[0199] As shown in Table 1, the modified hogalata catalysts obtained in Examples 1-3, under 10% H2O conditions, had an initial T100 of only 11°C at most, and after 1000 hours of operation, the T100 only increased to a maximum of 16°C. Under 30% H2O conditions, the initial T100 was still below 15°C at most, and after 1000 hours of operation, the T100 only increased to a maximum of 20°C. This indicates that the modified hogalata catalyst obtained by this invention not only possesses excellent low-temperature catalytic performance but also exhibits excellent water resistance. Because even under long-term operation under high water vapor content conditions, the modified hogalata catalyst obtained by this invention... The low-temperature catalytic performance degradation was minimal. In Comparative Example 1, without the addition of nano-boron carbide and nano-molybdenum carbide, the initial T100 of Comparative Example 1 increased significantly under both 10% H2O and 30% H2O conditions. After 1000 hours of operation, the increase in T100 under 30% H2O conditions was even more dramatic. This indicates that nano-boron carbide and nano-molybdenum carbide not only affect the low-temperature catalytic activity of the modified Hogarat catalyst but also severely impact its water resistance. Comparative Example 2 and Comparative Example 3, without the addition of nano-boron carbide and nano-molybdenum carbide respectively, showed significantly improved low-temperature catalytic performance compared to Comparative Example 1 under both 10% H2O and 30% H2O conditions. Under 2O conditions, the increase in T100 was significantly reduced, indicating that nano-boron carbide and nano-molybdenum carbide have a synergistic effect in improving the low-temperature catalytic activity and water resistance of the modified hogalata catalyst. Compared with Comparative Example 2, the initial T100 of Comparative Example 3 was greater than that of Comparative Example 2, but after 1000 hours of operation, the T100 of Comparative Example 3 was significantly smaller than that of Comparative Example 2. This suggests that boron carbide, which was not added in Comparative Example 2, significantly improved the water resistance of the modified hogalata catalyst, while molybdenum carbide, which was not added in Comparative Example 3, may have mainly enhanced the water resistance of the modified hogalata catalyst. The low-temperature catalytic activity of the catalyst was evaluated. In Comparative Example 4, the mixed acid aqueous solution was replaced with an oxalic acid aqueous solution. The initial T100 and the T100 after 1000 hours of operation in Comparative Example 4 under 10% H2O and 30% H2O conditions increased significantly. This indicates that the mixed acid aqueous solution can more effectively improve the low-temperature catalytic activity of the modified Hogarat catalyst compared with the oxalic acid aqueous solution. This may be because the phytic acid and tannic acid in the mixed acid aqueous solution have a much stronger complexing effect on metal ions such as copper, manganese, zirconium, and cerium than oxalic acid. Therefore, it is easier to obtain metal oxides with finer grains. The smaller the grain size of the metal oxide, the higher the low-temperature catalytic activity.In Comparative Example 5, the aqueous solutions of polyethyleneimine and guanidine were replaced with ammonia. Similar to Comparative Example 4, the initial T100 and the T100 after 1000 hours of operation in Comparative Example 5 under 10% H2O and 30% H2O conditions increased significantly, indicating a severe decrease in low-temperature catalytic activity. This suggests that the metal oxides precipitated from the aqueous solutions of polyethyleneimine and guanidine exhibit better low-temperature catalytic activity compared to ammonia. This may be due to the higher viscosity of the polyethyleneimine aqueous solution and the stronger pH buffering capacity of the guanidine aqueous solution. The combination of these two factors results in a slower and more uniform precipitation rate of metal ions, thus enhancing their catalytic activity in subsequent processes. During calcination, the resulting metal oxide crystals became finer and more uniform, ultimately significantly improving the low-temperature catalytic activity of the catalyst. In Comparative Example 6, no hydrophobic modification was performed. The initial T100 of Comparative Example 6 under 10% H2O and 30% H2O conditions was not significantly different from that of Example 1. However, after 1000 hours of operation, the T100 under 10% H2O and 30% H2O conditions was significantly higher than that of Example 1, and the low-temperature catalytic activity decreased drastically. This indicates that hydrophobic modification can effectively improve the water resistance of the modified Hogarth catalyst, maintaining high low-temperature catalytic activity over long operating periods.
[0200] Appendix Figure 1 Appendix Figure 2 and attached Figure 3The images shown are scanning electron microscope (SEM) images at 10,000x magnification of the modified hogallat catalysts obtained in Examples 1, 2, and 3, respectively. The surface states shown in these three images are essentially similar. It can be seen that the surface of the modified hogallat catalyst is composed of agglomerated large particles ranging from hundreds of nanometers to several micrometers. These agglomerated large particles are basically formed by the sintering of irregular small particles ranging in size from tens to hundreds of nanometers. Moreover, some boundaries are clearly visible between these irregular small particles, indicating that before sintering, these irregular small particles did not hard agglomerate into a single entity. During the sintering process, the boundaries between the irregular small particles gradually blurred, and they became a single entity. That is, before sintering, these irregular small particles existed almost entirely as nanometer or submicrometer-sized particles. This indicates that the precipitated particles obtained by the complexation precipitation of this invention still have a particle size at the nanometer or submicrometer scale. Combined with the specific process in the technical solution of this invention, namely using nano-boron carbide and nano-carbon... After the metal ions precipitated on the surface of the two nanoparticles in the molybdenum crystal nucleus and complexation precipitation steps, they still exist in a highly dispersed form at the nanoscale or submicron scale. Therefore, the precipitation of metal ions on the surface of the nanoparticle crystal nucleus is very uniform, and there is no random and uncontrolled rapid precipitation phenomenon. However, during the sintering process, these irregular small particles undergo an oxidation reaction. During the formation of metal oxides, a certain degree of agglomeration occurs due to sintering. However, this agglomeration is still not hard agglomeration, because the boundaries between the irregular small particles can still be vaguely seen, indicating that soft agglomeration is still the main process during sintering. The surface morphology shown in these three pictures is consistent with the low-temperature high catalytic activity exhibited by the modified Hogarth catalyst in this invention. The soft agglomeration state of the irregular small particles indicates that the size of the metal oxide grains obtained in this invention is very small and the precipitation rate of various metal ions is relatively uniform. There is no uncontrolled rapid precipitation, and the metal oxide grains do not exhibit sintering growth.
[0201] Appendix Figure 4 Appendix Figure 5 and attached Figure 6 The modified hogallat catalysts obtained in Examples 1, 2, and 3 are shown in transmission electron microscopy (TEM) images magnified 10,000 times. These three images show that the black and dark areas formed by transmitted light are essentially similar. The black areas are generally considered to be regions where copper oxide and manganese oxide crystals are relatively concentrated. The distribution and area of the black areas in the three images are relatively uniform, indicating that the distribution of copper oxide and manganese oxide within the catalyst is very uniform. This also indirectly confirms that the precipitation process of various metal ions during the complexation precipitation process of this invention is relatively uniform and stable, without any excessive aggregation of a single metal ion in certain areas. This fundamentally ensures the low-temperature high catalytic activity of the modified hogallat catalyst.
[0202] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing a modified hogallat catalyst, characterized in that: The preparation method of the modified hogallat catalyst includes preparing mother liquor, complexing precipitation, and... Three steps to hydrophobic modification; To prepare the mother liquor, copper salt, manganese salt, cerium salt, and ZrOCl2·8H2O are added to deionized water and completely dissolved. Then, polyvinylpyrrolidone K30 is added and completely dissolved. Under strong stirring and dispersion, nano boron carbide and nano molybdenum carbide are slowly added. After the addition is complete, strong stirring and dispersion are continued to obtain the mother liquor. The mass ratio of the copper salt, manganese salt, cerium salt, ZrOCl2·8H2O, deionized water, polyvinylpyrrolidone K30, nano boron carbide, and nano molybdenum carbide is 20~80:8~70:5~20:80~170:400~700:0.1~0.4:0.5~2:1.5~5; The complexation precipitation process involves heating the mother liquor to the reaction temperature, continuously stirring, and slowly adding a mixed acid aqueous solution dropwise to the mother liquor, controlling the dropping rate to avoid the formation of gels or precipitates. After the addition is complete, stirring continues until the complexation is complete. Then, simultaneously, an aqueous solution of polyethyleneimine and an aqueous solution of guanidine are added dropwise to the mother liquor, controlling the dropping rate of both to keep the pH value of the mother liquor constant. After the addition is complete, stirring continues until the reaction is complete. The mixture is then cooled to room temperature, and after aging, filtration, washing, drying, and calcination, catalyst powder is obtained. The mixed acid aqueous solution is composed of phytic acid, tannic acid, and deionized water. The mass ratio of phytic acid, tannic acid and deionized water is 10~50:70~180:260~600; The pH value is kept constant, ranging from 9 to 10. The mass ratio of the mother liquor, mixed acid aqueous solution, polyethyleneimine aqueous solution, and guanidine aqueous solution is 60~280:20~90:5~14:25~75; The hydrophobic modification involves placing the catalyst powder into an aqueous solution of methylsilicate, stirring and dispersing it evenly, filtering it, and then drying, washing, and drying the filtered solid to obtain the modified Hogarat catalyst.
2. The method for preparing the modified hogallat catalyst according to claim 1, characterized in that: The copper salt is one or a mixture of any two or more of copper sulfate, copper nitrate, and copper chloride in any mass ratio. The manganese salt is one or a mixture of any two or more of manganese sulfate, manganese nitrate, and manganese chloride in any mass ratio. The cerium salt is one of cerium sulfate, cerium nitrate, and cerium chloride, or a mixture of any two or more in any mass ratio.
3. The method for preparing the modified hogallat catalyst according to claim 1, characterized in that: The particle size of the boron carbide nanoparticles is 10~100nm; The particle size of the nano-molybdenum carbide is 10~100nm.
4. The method for preparing the modified hogallat catalyst according to claim 1, characterized in that: The polyethyleneimine aqueous solution contains polyethyleneimine at a mass concentration of 8-20 wt%. The guanidine aqueous solution has a guanidine concentration of 6-13 wt%.
5. The method for preparing the modified hogallat catalyst according to claim 1, characterized in that: The methylsilicate is one or a mixture of two of potassium methylsilicate and sodium methylsilicate in any mass ratio; The methylsilicate aqueous solution contains 1-2 wt% methylsilicate. The mass ratio of the catalyst powder to the aqueous methylsilicate solution is 30~77:
180.
6. The modified hogallat catalyst prepared by the preparation method according to any one of claims 1-5.