High-catalytic-activity catalyst taking fly ash as matrix as well as preparation method and application of high-catalytic-activity catalyst

Abstract

The invention relates to the technical field of coal ash utilization, in particular to a high-catalytic-activity catalyst with coal ash as a matrix and a preparation method and application of the high-catalytic-activity catalyst with the coal ash as the matrix, the composite material takes the coal ash as the matrix, Fe is loaded on the coal ash, and the composite material is treated and calcined to form a FeOx-FA heterogeneous catalyst. The catalyst is used for catalytic ozonation of phenol which is a pollutant difficult to degrade in water, the phenol removal capacity is high, the organic mineralization efficiency of the catalyst is obviously higher than that of a traditional carbon matrix catalyst, and the catalyst is high in catalytic activity and good in stability and has a good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of fly ash utilization, and in particular relates to a high catalytic activity catalyst with fly ash as a matrix, a preparation method and application thereof. Background Art

[0002] Fly ash is the most common waste from coal-fired power plants. At present, fly ash is mainly dumped in landfills, which not only occupies a large amount of land resources, but also causes environmental cycle interruption, soil erosion, affects the human DNA repair mechanism, and poses a threat to human health. Therefore, finding a suitable disposal site, long-term maintenance costs, inefficient land development and utilization, and adverse environmental impacts are important factors hindering the disposal of fly ash. The large amount of fly ash stockpiling has become a double burden on the environment and the economy.

[0003] In recent years, fly ash has attracted wide attention as a catalyst matrix for ozone catalytic oxidation, because its main components are silicon dioxide, aluminum oxide, etc., and it has good loading performance. As research focuses on the development of efficient and inexpensive water treatment methods, fly ash, as a low-cost solid powder with adsorption, catalytic and high mass transfer properties, has attracted much attention in the wastewater field.

[0004] At present, the treatment technology of phenol wastewater can be divided into physical and chemical methods, biological methods and advanced oxidation methods according to the working principle. Physical and chemical methods mainly include incineration, salting out, adsorption and ion exchange. Such methods are generally simple to operate, but expensive and have problems such as secondary pollution. Biological methods mainly include activated sludge method, biofilm method, anaerobic method and enzyme biotechnology. Due to the toxicity of phenolic substances to microorganisms, it is difficult to popularize and apply them. Advanced oxidation methods mainly include photocatalytic oxidation, ultrasonic oxidation, Fenton reagent, ozone oxidation, wet oxidation, supercritical water oxidation, electrochemical oxidation, etc., which are the methods currently used in the catalytic oxidation of phenol. Among them, heterogeneous ozone catalytic oxidation water treatment technology is a research hotspot for treating phenolic wastewater due to its advantages such as fast treatment effect, less consumption of chemical reagents and easy control.

[0005] In recent years, a series of studies have been conducted on fly ash doped Fe catalysts, which have improved the catalytic activity or life of the catalysts to a certain extent, but further research is needed on the pretreatment of fly ash and the preparation of silica and alumina catalyst substrates. Therefore, a solution is urgently needed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a high catalytic activity catalyst based on fly ash, a preparation method and application thereof. The catalyst is used for ozone catalytic oxidation of phenol, a difficult-to-degrade pollutant in water. The results show that it has a strong ability to remove phenol and an organic mineralization efficiency that is significantly higher than that of traditional carbon-based catalysts. The catalyst also has high catalytic activity and good stability and has good prospects for industrial application.

[0007] To achieve the above-mentioned purpose, the technical solution of the present invention is implemented as follows: a high catalytic activity catalyst based on fly ash, a preparation method and application thereof, wherein the composite material is based on fly ash and Fe is loaded on the fly ash, and the composite material is treated and calcined to form a FeOx-FA heterogeneous catalyst.

[0008] Furthermore, the preparation method comprises the following steps:

[0009] (1) After the fly ash solid particles are immersed in an alcohol solution to remove impurities, they are placed in a muffle furnace, heated to 400° C. at a heating rate of 5° C. / min, and calcined for 2 hours to convert all the metal elements in the fly ash into metal oxides;

[0010] (2) After heating for 2 hours, continue to heat up to 1200° C. at a heating rate of 10° C. / min and calcine for 20 minutes to remove non-metallic oxidizing substances such as SO3 in the fly ash, and obtain fly ash solid powder after cooling for standby use;

[0011] (3) The calcined fly ash solid powder is immersed in an alcohol solution to remove impurities, boiled in an oxalic acid solution to remove other metal oxides except aluminum oxide, washed with double distilled water, and dried for later use;

[0012] (4) stirring ferric citrate and distilled water at a temperature of 90-100° C., mixing thoroughly until the ferric citrate is completely dissolved in the water, cooling, and standing to obtain a ferric citrate precursor solution;

[0013] (5) using a vacuum-impregnation method, placing the fly ash powder obtained in step (3) in a three-necked flask for vacuum induction; when the pressure in the three-necked flask is less than 0.001 MPa, slowly opening the valve of the constant pressure dropping funnel to fully mix the ferric citrate precursor solution with the treated fly ash powder; after vacuum impregnation for 30 minutes, placing the mixed solution in a constant temperature oven for drying to obtain a ferric citrate-fly ash mixture;

[0014] (6) The dried ferric citrate-fly ash mixture is placed in a vacuum tube furnace, heated to 500-600°C at a heating rate of 5°C, and calcined for 2 h. After cooling to room temperature, the mixture is washed and dried to obtain a FeOx-FA heterogeneous catalyst.

[0015] Furthermore, the fly ash powder particles selected in step (1) have a particle size of 100-300 microns, and the mass of the fly ash calcined once is 5 g.

[0016] Furthermore, in step (3), the concentration of ferric citrate is 0.5 mol / L, and 100 mL of the precursor solution is prepared.

[0017] Furthermore, the washing in step (6) is performed multiple times with distilled water, and the product is dried in a constant temperature drying oven.

[0018] Furthermore, the high catalytic activity catalyst is used for ozone catalytic oxidation of phenol in water.

[0019] The beneficial effects of the present invention are embodied in:

[0020] (1) The main inventive point of the present invention is that the silicon dioxide-alumina after calcining fly ash is used as the substrate of the ozone catalytic oxidation catalyst, and at the same time, iron oxide is loaded by vacuum impregnation to form an ozone catalytic oxidation catalyst with high catalytic activity. The catalyst has a porous structure, which can increase the specific surface area, thereby increasing the contact probability between the catalyst and the reactants, and further improving the mass transfer effect. Since the SiO2 in the catalyst is in a stable state, the surface mass transfer efficiency, catalytic stability and mechanical stability of the catalyst all have good advantages in practical applications.

[0021] (2) The FeOx-FA heterogeneous catalyst prepared by the present invention can be used to catalytically oxidize phenol solution, and the removal rate of phenol and the mineralization efficiency of organic matter (i.e., TOC removal rate) are significantly improved, and the ozone concentration in the ozone catalytic oxidation reaction can be reduced, thereby reducing energy consumption.

[0022] (3) The vacuum impregnation method and high-temperature calcination method adopted in the present invention are used to prepare the FeOx-FA heterogeneous catalyst. The preparation method is simple and efficient and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the contact angle diagram of fly ash and FeOx-FA heterogeneous catalyst;

[0024] Figure 2 The phenol COD removal rate curve of the catalyst prepared in the embodiment and the comparative example and the pure ozone reaction;

[0025] Figure 3 The graph is a graph showing the TOC mineralization rate of phenol in the reaction of pure ozone with the catalysts prepared in the examples and comparative examples. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Example

[0028] 1. Pretreatment of fly ash:

[0029] After 5 g of fly ash solid particles with a diameter of 300 microns are immersed in an alcohol solution to remove impurities, they are placed in a muffle furnace, heated to 400°C at a heating rate of 5°C / min, and calcined for 2 hours to convert all the metal elements in the fly ash into metal oxides; after heating for 2 hours, the temperature is continued to be raised to 1200°C at a heating rate of 10°C / min, and calcined for 20 minutes to remove non-metallic oxidizing substances such as SO3 in the fly ash, and a solid is obtained after cooling for use; the calcined fly ash solid powder is immersed in an alcohol solution to remove impurities, boiled in an oxalic acid solution to remove the remaining metal oxides except aluminum oxide, washed with double distilled water, and dried for use.

[0030] 2. Preparation of precursor solution:

[0031] 0.5 mol / L ferric citrate and distilled water were stirred evenly at 90-100° C., fully mixed until the ferric citrate was completely dissolved in the water, and then cooled and allowed to stand to obtain 100 mL of ferric citrate precursor solution.

[0032] 3. Vacuum-impregnation induction:

[0033] The fly ash powder after multiple calcinations was placed in a three-necked flask for vacuum induction. When the pressure in the three-necked flask was less than 0.001 MPa, the valve of the constant pressure dropping funnel was slowly opened to fully mix the ferric citrate precursor solution with the treated fly ash powder. After vacuum impregnation for 30 minutes, the mixed solution was placed in a constant temperature oven for drying to obtain a ferric citrate-fly ash mixed substance.

[0034] 4. Preparation of FeOx-FA heterogeneous catalyst:

[0035] The dried ferric citrate-fly ash mixture is placed in a vacuum tube furnace, heated to 500-600°C at a heating rate of 5°C and calcined for 2 hours. After cooling to room temperature, the mixture is washed and dried to obtain a FeOx-FA heterogeneous catalyst.

[0036] 5. Ozone catalytic oxidation experiment of phenol:

[0037] A cylindrical reactor is used, and ozone is aerated from the bottom of the reactor through an aeration head. The ozone concentration is 15 mg / L, the initial concentration of phenol in water is 100 mg / L, the dissolved oxygen concentration is controlled to float around 0.25-0.35 mg / L, and the fly ash and FeOx-FA catalyst concentration is 5 g / L. Ozone catalytic oxidation reaction is carried out after adsorption.

[0038] After 40 minutes of reaction, the concentration of phenol in the aqueous solution was determined by high performance liquid chromatography. It was found that the system with FeOx-FA as the catalyst had the highest COD removal rate and TOC mineralization rate, which were 77.3% and 59.2%, respectively.

[0039] FeO x -FA heterogeneous catalyst performance analysis:

[0040] like Figure 1 As shown in the contact angle diagram of fly ash and FeOx-FA heterogeneous catalyst, the contact angle of the original fly ash is 60.1°, and the contact angle of the treated FeOx-FA heterogeneous catalyst is 35.05°, so the FeOx-FA catalyst is more hydrophilic.

[0041] Figure 2 The figure shows the COD removal rate of ozone reaction, ozone + fly ash reaction, and ozone + FeOx-FA catalyst catalytic oxidation reaction. It can be seen from the figure that the COD removal efficiency of ozone + FeOx-FA catalyst catalytic oxidation reaction is the fastest. At 40 minutes, the COD removal rates of ozone reaction, ozone + fly ash reaction, and ozone + FeOx-FA catalyst catalytic oxidation reaction are 36.87%, 65.83% and 77.30%, respectively. Therefore, FeOx-FA catalyst has the best effect in the ozone catalytic oxidation system.

[0042] Figure 3 The figure shows the TOC removal rate of ozone reaction, ozone + fly ash reaction, and ozone + FeOx-FA catalyst catalytic oxidation reaction. It can be seen from the figure that the TOC removal efficiency of ozone + FeOx-FA catalyst catalytic oxidation reaction is the fastest. At 40 minutes, the TOC removal rates of ozone reaction, ozone + fly ash reaction, and ozone + FeOx-FA catalyst catalytic oxidation reaction are 29.97%, 52.37% and 59.20%, respectively. Therefore, FeOx-FA catalyst has the best effect in the ozone catalytic oxidation system.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high catalytic activity catalyst based on fly ash, characterized in that: The composite material uses fly ash as a matrix and loads Fe on the fly ash. The composite material is treated and calcined to form a FeOx-FA heterogeneous catalyst.

2. A method for preparing a high catalytic activity catalyst based on fly ash, characterized in that: The following steps are involved: (1) After the fly ash solid particles are immersed in an alcohol solution to remove impurities, they are placed in a muffle furnace, heated to 400° C. at a heating rate of 5° C. / min, and calcined for 2 hours to convert all the metal elements in the fly ash into metal oxides; (2) After heating for 2 hours, the temperature is further increased to 1200° C. at a heating rate of 10° C. / min and calcined for 20 minutes to remove non-metallic oxides in the fly ash, and then the fly ash solid powder is obtained after cooling; (3) the fly ash solid powder in step (2) is immersed in an alcohol solution to remove impurities, boiled in an oxalic acid solution to remove other metal oxides except aluminum oxide, washed with double distilled water, and dried for later use; (4) stirring ferric citrate and distilled water at 90-100° C. until the ferric citrate is completely dissolved in the water, cooling, and standing to obtain a ferric citrate precursor solution; (5) using a vacuum-impregnation method, placing the fly ash powder obtained in step (3) in a three-necked flask for vacuum induction; when the pressure in the three-necked flask is less than 0.001 MPa, slowly opening the valve of the constant pressure dropping funnel to allow the ferric citrate precursor solution to be fully mixed with the treated fly ash powder; after vacuum impregnation for 30 minutes, placing the mixed solution in a constant temperature oven for drying to obtain a ferric citrate-fly ash mixture; (6) The ferric citrate-fly ash mixture obtained in step (5) is placed in a vacuum tube furnace, heated to 500-600°C at a heating rate of 5°C and calcined for 2 hours, cooled to room temperature, washed and dried to obtain FeO x -FA heterogeneous catalyst.

3. The method for preparing a fly ash-based catalyst with high catalytic activity according to claim 2, characterized in that: The particle size of the fly ash powder selected in step (1) is 100-300 microns, and the mass of the fly ash calcined once is 5g.

4. The method for preparing a fly ash-based catalyst with high catalytic activity according to claim 2, characterized in that: Step (4) The concentration of ferric citrate is 0.5 mol / L, and 100 mL of precursor solution is prepared.

5. The method for preparing a fly ash-based catalyst with high catalytic activity according to claim 2, characterized in that: The washing in step (6) is performed at least 3 times with distilled water, and the drying is performed in a constant temperature drying oven.

6. The use of a fly ash-based catalyst with high catalytic activity according to claim 1, characterized in that: The catalyst with high catalytic activity is used for ozone catalytic oxidation of phenol in water.

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