A method for preparing a denitration catalyst

Abstract

The present invention relates to the technical field of catalyst preparation, and particularly relates to a method for preparing a denitration catalyst. The method includes: wet ball-milling the pretreated silica powder and titanium dioxide to obtain a mixture A; soaking glass fiber A in a first organic solvent, filtering, and washing with an organic acid solution to obtain pretreated glass fiber A; mixing a tungsten source and a first aqueous ammonia solution, and then mixing with the mixture A to obtain a mixture B; mixing ammonium metavanadate and a second aqueous ammonia solution, and then mixing with the mixture B to obtain a mixture C; performing a first kneading on the pretreated glass fiber A, the mixture C, and a part of the lubricant to obtain a mixture D; performing a second kneading on the mixture D, glass fiber B, the remaining lubricant, the binder, and the plasticizer, followed by aging, extrusion molding, drying, and calcination. This method uses a silicon material to replace part of the titanium dioxide, and at the same time optimizes the preparation conditions and fiber ratio to prepare a denitration catalyst with good performance.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a method for preparing a denitration catalyst. Background Art

[0002] NH3-SCR is an important denitrification technology in the coal-fired field, and the catalyst is the key to NH3-SCR. The titanium dioxide content in traditional commercial vanadium-titanium denitrification catalysts is above 70%, and at the same time, it is not the main active substance in the actual denitrification reaction process. Titanium dioxide and structural support material glass fiber are the components with the largest content in the catalyst material preparation process, and the effective combination of the two is also the key to the overall performance of the catalyst.

[0003] A large amount of titanium dioxide is used in denitration catalysts but its value is not fully utilized, resulting in a certain waste of resources. The price of titanium dioxide for preparing denitration catalyst carriers is relatively high, and the amount used is relatively large, resulting in a high cost of denitration catalysts.

[0004] If a reasonable formulation method can be adopted to allow some substances to replace titanium dioxide in the denitrification catalyst while ensuring that the catalyst has excellent performance, it will undoubtedly reduce the preparation cost of the catalyst. Summary of the invention

[0005] The purpose of the present invention is to fully reduce the usage of titanium dioxide in a denitration catalyst, optimize the preparation conditions, maintain the catalytic performance of the denitration catalyst and improve the wear resistance of the denitration catalyst, and provide a method for preparing a denitration catalyst.

[0006] In order to achieve the above object, the present invention provides a method for preparing a denitration catalyst, which comprises the following steps:

[0007] (1) wet-ball milling the silicon oxide powder, then soaking it in a weak alkaline solution, and then performing solid-liquid separation, then soaking the obtained solid phase in a weak acidic solution, and then performing solid-liquid separation, washing and drying to obtain pretreated silicon oxide powder; wet-ball milling the pretreated silicon oxide powder and titanium dioxide to obtain a mixture A;

[0008] (2) soaking the glass fiber A in a first organic solvent, filtering, and then washing with an organic acid solution to obtain a pretreated glass fiber A;

[0009] (3) mixing the tungsten source and the first ammonia solution, and then mixing with the mixed material A to obtain a mixed material B;

[0010] (4) mixing ammonium metavanadate and the second ammonia solution, and then mixing with mixed material B to obtain mixed material C;

[0011] (5) First, pre-treated glass fiber A, mixture C, and part of the lubricant are subjected to the first kneading to obtain mixture D;

[0012] (6) Then, mixture D, glass fiber B, the remaining lubricant, the binder, and the plasticizer are subjected to the second kneading, followed by aging, extrusion molding, drying, and calcination;

[0013] Among them, the length of glass fiber A is 0.2 - 3 mm, and the length of glass fiber B is 3 - 5 mm;

[0014] The solvent used for wet ball milling of the pre-treated silica powder and titanium dioxide is obtained by mixing a second organic solvent and a third aqueous ammonia solution.

[0015] Preferably, the weight ratio of the amount of glass fiber A to glass fiber B is 1:4 - 10.

[0016] Preferably, the weight ratio of the amount of pre-treated silica powder to titanium dioxide is 1:0.5 - 2.

[0017] Preferably, in step (1), the second organic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, acetone, and dimethyl ether; and / or

[0018] The concentration of the third aqueous ammonia solution is 1 - 10 wt%.

[0019] Preferably, the time for wet ball milling of the pre-treated silica powder and titanium dioxide is ≥ 30 min.

[0020] Preferably, in step (1), the ratio of the volume of the second organic solvent to the total weight of the pre-treated silica powder and titanium dioxide is 2 - 10 mL:1 g; and / or

[0021] The ratio of the volume of the third aqueous ammonia solution to the total weight of the pre-treated silica powder and titanium dioxide is 2 - 15 mL:1 g.

[0022] Preferably, in step (2), the first organic solution is methanol, ethanol, or ethylene glycol; and / or

[0023] The conditions for soaking include: temperature 50 - 90 °C, time 30 - 90 min; and / or

[0024] The organic acid is selected from one or more of citric acid, oxalic acid, acetic acid, and tartaric acid; and / or

[0025] The concentration of the organic acid in the organic acid solution is ≤ 0.2 mol / L.

[0026] Preferably, the ratio of the total weight of the pretreated silica powder and titanium dioxide, the total weight of glass fiber A and glass fiber B, the weight of the tungsten source, and the weight of ammonium metavanadate is 70:4-7:2-5:0.4-1.5, where the tungsten source is calculated as WO3 and the ammonium metavanadate is calculated as V2O5.

[0027] Preferably, in step (5), the conditions for the first kneading include: a temperature of 150-200 °C and a time of 15-60 min.

[0028] Preferably, in step (6), the conditions for the second kneading include: a temperature of 180-250 °C and a time of 3-8 h; and / or

[0029] the aging time is 30-40 h; and / or

[0030] The calcination is a two-stage continuous calcination process.

[0031] Preferably, the lubricant is selected from one or more of glycerol, triethanolamine, and stearic acid; and / or

[0032] The plasticizer is selected from phthalic acid and / or dioctyl phthalate; and / or

[0033] The binder is selected from one or more of polyvinyl alcohol, methylcellulose, hydroxymethylcellulose, polyacrylamide, and polyethylene glycol.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention uses a silicon material to replace part of the titanium dioxide, which can greatly reduce the usage amount of titanium dioxide. At the same time, by optimizing the catalyst preparation conditions and the glass fiber ratio, a denitration catalyst with good performance is prepared.

[0036] 2. In the method of the present invention, by pretreating the silica, the contact between the silica and the titanium dioxide can be made closer, and the pretreated silica is beneficial to improving the wear resistance and catalytic performance of the catalyst, thereby improving the overall performance of the catalyst. Detailed Embodiments

[0037] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention and are not used to limit the present invention.

[0038] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0039] The present invention provides a method for preparing a denitration catalyst, and the method comprises the following steps:

[0040] (1) Wet ball-mill the silica powder, then soak it in a weakly alkaline solution, then perform solid-liquid separation, then soak the obtained solid phase in a weakly acidic solution, then perform solid-liquid separation, washing and drying to obtain pretreated silica powder; wet ball-mill the pretreated silica powder and titanium dioxide to obtain a mixture A;

[0041] (2) Soak glass fiber A in a first organic solvent, filter, and then wash it with an organic acid solution to obtain pretreated glass fiber A;

[0042] (3) Mix a tungsten source and a first aqueous ammonia solution, and then mix it with mixture A to obtain mixture B;

[0043] (4) Mix ammonium metavanadate and a second aqueous ammonia solution, and then mix it with mixture B to obtain mixture C;

[0044] (5) Perform a first kneading on the pretreated glass fiber A, mixture C and part of the lubricant to obtain mixture D;

[0045] (6) Perform a second kneading on mixture D, glass fiber B, the remaining lubricant, the binder and the plasticizer, and then perform aging, extrusion molding, drying and calcination;

[0046] Wherein, the length of glass fiber A is 0.2 - 3 mm, and the length of glass fiber B is 3 - 5 mm; when wet ball-milling the pretreated silica powder and titanium dioxide, the solvent used is obtained by mixing a second organic solvent and a third aqueous ammonia solution.

[0047] In a preferred embodiment, the length of the glass fiber B is greater than the length of the glass fiber A.

[0048] In a preferred embodiment, the weight ratio of the amount of glass fiber A to glass fiber B is 1:4 - 10; specifically, it can be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. By treating the shorter glass fiber A with an organic solvent and an organic acid and reasonably controlling the amounts of glass fiber A and glass fiber B used in the present invention, the glass fiber can be made closer to the carrier material (i.e., the mixed material C), which is beneficial to improving the catalytic performance and strength of the prepared denitration catalyst.

[0049] In a preferred embodiment, in step (1), during the pretreatment of the silicon oxide powder, the wet ball milling makes the particle size of the silicon oxide powder ≤ 100 mesh; the weak alkaline solution can be a sodium hydroxide solution with a concentration of 0.1 - 0.5 mol / L. The conditions for soaking with the weak alkaline solution include: temperature of 60 - 80 °C, time of 30 - 60 min, and liquid-solid ratio of 5 - 15 ml:1 g; the weak acidic solution can be an organic acid solution with a concentration of 0.03 - 0.08 mol / L, and the organic acid can be citric acid, acetic acid, tartaric acid, or oxalic acid. The conditions for soaking with the weak acidic solution include: temperature of 50 - 70 °C, time of 10 - 40 min, and liquid-solid ratio of 5 - 15 ml:1 g. In the present invention, silicon oxide powder can be used to replace part of the titanium dioxide to reduce the preparation cost of the denitration catalyst; at the same time, by pretreating the silicon oxide powder according to the above method, the contact between the silicon oxide and the titanium dioxide can be made closer. After the silicon oxide is pretreated, the specific surface area of the catalyst can also be increased, which is beneficial to improving the performance and strength of the catalyst.

[0050] In the present invention, during the pretreatment of the silicon oxide powder, the solid-liquid separation, washing, and drying can be carried out in a conventional manner in the art.

[0051] In a preferred embodiment, the weight ratio of the amount of the pretreated silicon oxide powder to the titanium dioxide is 1:0.5 - 2; specifically, it can be 1:0.5, 1:1, 1:1.5, or 1:2.

[0052] In a preferred embodiment, in step (1), the second organic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, acetone, and dimethyl ether; the concentration of the third ammonia water solution is 1 - 10 wt%.

[0053] In a preferred case, the time for wet ball milling the pretreated silicon oxide powder and the titanium dioxide is ≥ 30 min, and more preferably 50 - 80 min.

[0054] Further preferably, in step (1), the ratio of the volume of the second organic solvent to the total weight of the pretreated silica powder and titanium dioxide is 2 - 10 mL:1 g; the ratio of the volume of the third aqueous ammonia solution to the total weight of the pretreated silica powder and titanium dioxide is 2 - 15 mL:1 g.

[0055] In a preferred embodiment, in step (2), the first organic solution can be methanol, ethanol or ethylene glycol.

[0056] In a preferred embodiment, in step (2), the conditions for soaking include: temperature is 50 - 90 °C, time is 30 - 90 min; the liquid-solid ratio of the first organic solution to glass fiber A is 5 - 30 mL:1 g.

[0057] In a preferred embodiment, the organic acid is selected from one or more of citric acid, oxalic acid, acetic acid and tartaric acid; the concentration of the organic acid in the organic acid solution ≤ 0.2 mol / L, more preferably 0.05 - 0.15 mol / L. In the present invention, by using the organic acid solution to treat the glass fiber soaked in the organic solvent, acidic sites can be modified on the glass fiber, and at the same time, it is beneficial to the dispersion of the glass fiber and avoids serious agglomeration during the preparation of the catalyst.

[0058] In the present invention, in order to further improve the denitration performance and strength of the prepared denitration catalyst, the dosages of each raw material component can be reasonably controlled. In a preferred case, the ratio of the total weight of the pretreated silica powder and titanium dioxide, the total weight of glass fiber A and glass fiber B, the weight of the tungsten source and the weight of ammonium metavanadate is 70:4 - 7:2 - 5:0.4 - 1.5, where the tungsten source is calculated as WO3 and ammonium metavanadate is calculated as V2O5.

[0059] In a preferred embodiment, in step (3), the concentration of the first aqueous ammonia solution is 5 - 15 wt%.

[0060] In the present invention, in step (3), there are no special requirements for the conditions of mixing the tungsten source and the first aqueous ammonia solution, and it can be carried out in a conventional manner in the art; there are also no special requirements for the conditions of mixing with mixture A, and it can be carried out according to the conventional conditions in the art.

[0061] In a preferred embodiment, the tungsten source can be a common tungsten salt in the art, for example, it can be ammonium paratungstate.

[0062] In a preferred embodiment, in step (4), the concentration of the second aqueous ammonia solution is 5 - 15 wt%.

[0063] In the present invention, in step (4), there are no special requirements for the mixing conditions of ammonium metavanadate and the second aqueous ammonia solution, and it can be carried out in a conventional manner in the art; there are also no special requirements for the mixing conditions for mixing with mixture B, and it can be carried out according to the conventional conditions in the art.

[0064] In a preferred embodiment, in step (5), the conditions for the first mixing include: the temperature is 150 - 200 °C, and the time is 15 - 60 min. The first mixing can be carried out in a common mixer in the art.

[0065] In a preferred embodiment, in step (6), the conditions for the second mixing include: the temperature is 180 - 250 °C, and the time is 3 - 8 h. The second mixing can be carried out in a common mixer in the art.

[0066] In a preferred embodiment, in step (6), the aging time is 30 - 40 h; specifically, it can be 30 h, 32 h, 35 h, 36 h, 38 h or 40 h.

[0067] In the present invention, in step (6), there are no special requirements for the drying conditions, and it can be carried out in a conventional manner in the art. For example, it can be dried at a temperature of 80 - 100 °C for 5 - 15 h.

[0068] In a preferred embodiment, in step (6), the calcination is a two-stage continuous calcination process, that is, first the first-stage calcination is carried out and then the second-stage calcination is carried out. Further preferably, the conditions for the first-stage calcination include: the temperature is 200 - 400 °C, and the time is 1 - 3 h; the conditions for the second-stage calcination include: the temperature is 500 - 700 °C, and the time is 2 - 4 h.

[0069] In a preferred case, the lubricant is selected from one or more of glycerol, triethanolamine, and stearic acid; the plasticizer is selected from phthalic acid and / or dioctyl phthalate; the binder is selected from one or more of polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, polyacrylamide, and polyethylene glycol.

[0070] In a preferred embodiment, the lubricant used in step (5) accounts for 1 - 10 wt%. of the total amount of the lubricant.

[0071] In the present invention, there are no special requirements for the dosages of the lubricant, binder, and plasticizer, and they can be used according to the conventional dosages in the art. In a preferred case, the ratio of the total weight of the pretreated silica powder and titanium dioxide to the weight of the lubricant, the weight of the binder, and the weight of the plasticizer is 1:0.05:0.1:0.06 - 0.1:0.07 - 0.1.

[0072] The present invention will be described in detail below by way of examples, but the scope of protection of the present invention is not limited thereto.

[0073] Unless otherwise specified, the reagents used in the following examples and comparative examples are all commercially available products.

[0074] Example 1

[0075] (1) Wet ball-mill the silica powder until the particle size is <100 mesh, then soak it in a 0.2 mol / L sodium hydroxide solution for 60 min at a temperature of 80 °C and a liquid-solid ratio of 10 mL:1 g. Then, perform solid-liquid separation. Next, soak the obtained solid phase in a 0.05 mol / L citric acid solution for 15 min at a temperature of 60 °C and a liquid-solid ratio of 10 mL:1 g. Then, perform solid-liquid separation, washing, and drying to obtain the pretreated silica powder;

[0076] Wet ball-mill the pretreated silica powder and titanium dioxide according to a weight ratio of 1:1 for 60 min. The solvent used for wet ball-milling is obtained by mixing a second organic solvent (ethanol) and a third aqueous ammonia solution (concentration of 3 wt%). The volume ratio of the second organic solvent to the total weight of the pretreated silica powder and titanium dioxide is 5 mL:1 g, and the volume ratio of the third aqueous ammonia solution to the total weight of the pretreated silica powder and titanium dioxide is 10 mL:1 g. After ball-milling, wash thoroughly to obtain mixture A;

[0077] (2) Immerse glass fiber A in a first organic solvent (ethanol) for reaction at a soaking temperature of 70 °C and a soaking time of 60 min. The liquid-solid ratio of the first organic solution to glass fiber A is 20 mL:1 g. Filter, and then wash with an organic acid solution (0.1 mol / L citric acid solution) to obtain the pretreated glass fiber A;

[0078] (3) Mix a tungsten source (ammonium paratungstate) with a first aqueous ammonia solution (concentration of 5 wt%), and then mix it with mixture A to obtain mixture B;

[0079] (4) Mix ammonium metavanadate and a second aqueous ammonia solution (concentration of 5 wt%), and then mix it with mixture B to obtain mixture C;

[0080] (5) Perform the first kneading (temperature of 180 °C, time of 30 min) on the pretreated glass fiber A, mixture C, and a part of the lubricant (5 wt% of the total amount of the lubricant) to obtain mixture D;

[0081] (6) Mix the mixture D, glass fiber B, the remaining lubricant (triethanolamine), binder (polyvinyl alcohol), and plasticizer (phthalic acid) for the second kneading (temperature: 200 °C, time: 5 h), then let it age for 36 h, followed by extrusion molding to obtain a honeycomb catalyst blank. Then dry it at 80 °C for 10 h, then raise the temperature to 300 °C and calcine for 2 h, and then raise the temperature to 600 °C and calcine for 3 h; then cut it to obtain the catalyst;

[0082] Among them, the length of glass fiber A is greater than 0.2 mm and less than 3 mm, the length of glass fiber B is 3 - 5 mm, and the weight ratio of glass fiber A to glass fiber B is 1:6;

[0083] The ratio of the total weight of the pretreated silica powder and titanium dioxide, the total weight of glass fiber A and glass fiber B, the weight of the tungsten source, and the weight of ammonium metavanadate is 70:6:3:1, where the tungsten source is calculated as WO3 and ammonium metavanadate is calculated as V2O5;

[0084] The ratio of the total weight of the pretreated silica powder and titanium dioxide to the weight of the lubricant, binder, and plasticizer is 1:0.08:0.08:0.09.

[0085] Example 2

[0086] (1) Wet ball-mill the silica powder until the particle size < 100 mesh, then soak it in a 0.3 mol / L sodium hydroxide solution for 60 min at a temperature of 80 °C and a liquid-solid ratio of 10 mL:1 g during soaking. Then perform solid-liquid separation, and then soak the obtained solid phase in a 0.06 mol / L citric acid solution for 15 min at a temperature of 60 °C and a liquid-solid ratio of 15 mL:1 g. After that, perform solid-liquid separation, washing, and drying to obtain the pretreated silica powder;

[0087] Wet ball-mill the pretreated silica powder and titanium dioxide for 60 min according to a weight ratio of 1:1.2. The solvent used for ball-milling is obtained by mixing a second organic solvent (ethylene glycol) and a third aqueous ammonia solution (concentration: 4 wt%). Among them, the volume ratio of the second organic solvent to the total weight of the pretreated silica powder and titanium dioxide is 5 mL:1 g, and the volume ratio of the third aqueous ammonia solution to the total weight of the pretreated silica powder and titanium dioxide is 10 mL:1 g; after ball-milling, wash it thoroughly to obtain mixture A;

[0088] (2) Soak glass fiber A in the first organic solvent (methanol) for reaction at a soaking temperature of 90 °C and a soaking time of 30 min. The liquid-solid ratio of the first organic solution to glass fiber A is 20 mL:1 g. Filter it, and then wash it with an organic acid solution (0.1 mol / L citric acid solution) to obtain the pretreated glass fiber A;

[0089] (3) Mix the tungsten source (ammonium paratungstate) with the first aqueous ammonia solution (concentration: 5 wt%) and then mix with mixture A to obtain mixture B;

[0090] (4) Mix ammonium metavanadate with the second aqueous ammonia solution (concentration: 5 wt%) and then mix with mixture B to obtain mixture C;

[0091] (5) Conduct the first kneading (temperature: 185 °C, time: 30 min) on the pretreated glass fiber A, mixture C, and a part of the lubricant (5 wt% of the total amount of the lubricant) to obtain mixture D;

[0092] (6) Conduct the second kneading (temperature: 200 °C, time: 5 h) on mixture D, glass fiber B, the remaining lubricant (triethanolamine), binder (polyvinyl alcohol), and plasticizer (phthalic acid), then conduct aging for 36 h, then extrude and form to obtain a honeycomb catalyst blank, then dry at 80 °C for 10 h, then raise the temperature to 300 °C and calcine for 2 h, and then raise the temperature to 600 °C and calcine for 3 h; then conduct cutting to obtain the catalyst;

[0093] Among them, the length of glass fiber A is greater than 0.2 mm and less than 3 mm, the length of glass fiber B is 3 - 5 mm, and the weight ratio of glass fiber A to glass fiber B is 1:6.5;

[0094] The ratio of the total weight of the pretreated silica powder and titanium dioxide, the total weight of glass fiber A and glass fiber B, the weight of the tungsten source, and the weight of ammonium metavanadate is 70:5:4:0.8, where the tungsten source is calculated as WO3 and ammonium metavanadate is calculated as V2O5;

[0095] The ratio of the total weight of the pretreated silica powder and titanium dioxide to the weight of the lubricant, binder, and plasticizer is 1:0.08:0.08:0.09.

[0096] Example 3

[0097] Implement according to the method described in Example 1, the difference is that in step (1), the pretreatment process of the silica powder is as follows: wet ball mill the silica powder to a particle size < 100 mesh, then soak it in a 0.4 mol / L sodium hydroxide solution for 50 min, the soaking temperature is 80 °C and the liquid-solid ratio is 10 mL:1 g, then conduct solid-liquid separation, then soak the obtained solid phase in a 0.05 mol / L oxalic acid solution for 40 min, the soaking temperature is 60 °C and the liquid-solid ratio is 10 mL:1 g, then conduct solid-liquid separation, washing, and drying to obtain the pretreated silica powder; and wet ball mill the pretreated silica powder and titanium dioxide according to a weight ratio of 1.2:1.

[0098] Comparative Example 1

[0099] The method described in Example 1 was implemented, except that in step (1), the pretreated silica powder was replaced with untreated silica powder of the same weight; and the solvent used for wet ball milling was water.

[0100] Comparative Example 2

[0101] The method described in Example 1 was implemented, except that the length of glass fiber A was 3 - 5 mm.

[0102] Comparative Example 3

[0103] The method described in Example 1 was implemented, except that in step (1), the process of pretreating the silica powder was as follows: the silica powder was wet ball milled to a particle size < 100 mesh, then soaked in a 0.2 mol / L sodium hydroxide solution for 60 min at a temperature of 80 °C and a liquid - solid ratio of 10 mL:1 g, and then solid - liquid separation, washing, and drying were carried out to obtain the pretreated silica powder.

[0104] Comparative Example 4

[0105] The method described in Example 1 was implemented, except that glass fiber B used in step (6) was used in step (5).

[0106] Specifically, the processes of steps (5) and (6) are as follows:

[0107] (5) The pretreated glass fiber A, glass fiber B, mixture C, and part of the lubricant (5 wt% of the total lubricant) were subjected to the first kneading (temperature: 180 °C, time: 30 min) to obtain mixture D;

[0108] (6) Mixture D, the remaining lubricant (triethanolamine), binder (polyvinyl alcohol), and plasticizer (phthalic acid) were subjected to the second kneading (temperature: 200 °C, time: 5 h), then aged for 36 h, then extruded into a honeycomb catalyst blank, then dried at 80 °C for 10 h, then heated to 300 °C and calcined for 2 h, and then heated to 600 °C and calcined for 3 h; then cut to obtain the catalyst.

[0109] Comparative Example 5

[0110] The method described in Example 1 was implemented, except that in step (1), the solvent used for wet ball milling of the pretreated silica powder and titanium dioxide was water.

[0111] Comparative Example 6

[0112] The denitration catalyst is prepared according to the traditional method, and the specific process is as follows:

[0113] (1) Dissolve 13.4 g of ammonium metatungstate in 25 mL of ammonia water solution (concentration 5%) to obtain a mixed solution A. Then mix the mixed solution A with 650 g of titanium source (titanium dioxide) and carry out ball milling for 20 - 30 min at a ball milling rate of 800 r / min to obtain a titanium-tungsten powder mixture;

[0114] (2) Dissolve 4.5 g of ammonium metavanadate in 50 mL of ammonia water solution (concentration 5%), then add 50 mL of monoethanolamine and mix evenly to obtain a mixed solution B. Then mix the mixed solution B with the titanium-tungsten powder mixture obtained in step (1) to obtain a mixture C;

[0115] (3) Mix the mixture C with 38 g of lubricant (triethanolamine), 42 g of binder (polyvinyl alcohol), 50 g of plasticizer (phthalic acid), 80 g of glass fiber (length 3 - 5 mm) and 160 g of water, and carry out kneading. The kneading temperature is 200 °C and the kneading time is 5 h. Then let it age at 25 °C for 36 h;

[0116] (4) Extrude the aged material to obtain a honeycomb catalyst blank, then dry it at 80 °C for 10 h and carry out two calcinations. The first calcination temperature is 350 °C and the first calcination time is 1.5 h. The second calcination temperature is 650 °C and the second calcination time is 4.5 h. After the calcination is completed, cut it to obtain the denitration catalyst;

[0117] Among them, based on the total weight of the tungsten source and the titanium source being 100 wt%, the content of the tungsten source is 3.5 wt%. Based on the weight of the vanadium source and the titanium source being 100 wt%, the content of the vanadium source is 1.2 wt%. Among them, the tungsten source is calculated as WO3 and the vanadium source is calculated as V2O5; the tungsten source is ammonium metatungstate and the vanadium source is ammonium metavanadate.

[0118] Comparative Example 7

[0119] Implement according to the method described in Example 1, the difference is that in step (1), the titanium dioxide is replaced with the same weight of pretreated silica powder.

[0120] Test Example

[0121] 1. Use a TYE-300 type pressure testing machine to test the axial compressive strength and longitudinal compressive strength of the denitration catalysts obtained in Examples 1 - 3 and the products obtained in Comparative Examples 1 - 7. The range of the pressure testing machine is 300 KN and the pressurization rate is 250 N / s. The test results are shown in Table 1.

[0122] 2. Take a small piece of the denitration catalysts obtained in Examples 1 - 3 and the products obtained in Comparative Examples 1 - 7. After crushing, use a fully automatic nitrogen adsorption and desorption instrument (Micromeritics 2020) to test the specific surface area of the denitration catalysts and the products. The test results are shown in Table 1.

[0123] 3. Test the denitration rate of nitrogen oxides for the denitration catalysts obtained in Examples 1 - 3 and the products obtained in Comparative Examples 1 - 7;

[0124] Test method: Test the denitration rate of nitrogen oxides of the denitration catalyst at different temperatures: The test method is to take small samples of the denitration catalyst and the product and place them into the catalyst performance evaluation reaction device, and introduce the simulated gas for activity evaluation. The composition of the simulated gas is similar to that of the industrial boiler tail gas, and its composition is as follows: 500 ppm of NO, 400 ppm of NH3, 10.00% of O2, 12% of water, and the rest is nitrogen. Pass the simulated gas into the denitration reactor for reaction. The reaction temperature is 210 °C. The concentration of nitrogen oxides in the flue gas before and after the reaction is analyzed using a 42i - HL flue gas analyzer, and then the denitration rate of the denitration catalyst at the reaction temperature of 210 °C is calculated. The test results are shown in Table 2;

[0125] Adjust the reaction temperature in the denitration reactor to 270 °C to obtain the denitration rate of the denitration catalyst at the reaction temperature of 270 °C. The test results are shown in Table 2;

[0126] The calculation method of the denitration rate of the denitration catalyst is: η=(a - b) / a×100%, where the concentration of nitrogen oxides in the flue gas before the reaction is a, the concentration of nitrogen oxides in the flue gas after the reaction is b, and the denitration rate of the denitration catalyst is η.

[0127] 4. Test the abrasion resistance of the denitration catalysts obtained in Examples 1 - 3 and the products obtained in Comparative Examples 1 - 7;

[0128] Test method: Divide the sample to be tested into two parts, which are used as the test sample and the reference sample respectively. Dry the test sample and the reference sample in an oven at 105 °C for 2 h, and weigh the test sample and the reference sample after natural cooling; then place the test sample and the reference sample into the test chamber and the reference chamber of the abrasion test device respectively. The test sample and the reference sample are completely sealed with ceramic fiber paper between them and the chamber wall. Then pass the air containing the abrasive through the test sample at a certain flow rate, and pass the air through the reference sample at the same flow rate. After 2 hours of abrasion, weigh the test sample, the reference sample and the abrasive after abrasion to calculate the abrasion strength.

[0129] The specific calculation method is as follows:

[0130]

[0131] Among them, ξ h represents the wear intensity, % / kg;

[0132] W1 represents the weight of the test sample before the test, kg;

[0133] W2 represents the weight of the test sample after the test, kg;

[0134] W3 represents the weight of the reference sample before the test, kg;

[0135] W4 represents the weight of the reference sample after the test, kg;

[0136] W represents the recorded weight of the abrasives, kg.

[0137] Table 1

[0138] Axial compressive strength MPa Radial compressive strength MPa <![CDATA[Specific surface area m 2 / g]]> Example 1 2.56 0.90 70.17 Example 2 2.58 0.91 71.04 Example 3 2.55 0.89 69.24 Comparative Example 1 1.87 0.57 55.75 Comparative Example 2 2.32 0.67 63.55 Comparative Example 3 2.45 0.76 61.33 Comparative Example 4 2.46 0.85 67.67 Comparative Example 5 1.97 0.61 57.75 Comparative Example 6 2.57 0.89 67.34 Comparative Example 7 1.76 0.48 69.98

[0139] Table 2

[0140] Denitrification rate %(210 °C) Denitrification rate %(270 °C) Wear strength (% / kg) Example 1 97.55 98.76 0.021 Example 2 98.04 98.44 0.019 Example 3 98.05 99.11 0.022 Comparative Example 1 76.22 81.03 0.054 Comparative Example 2 84.56 83.44 0.057 Comparative Example 3 79.33 80.25 0.041 Comparative Example 4 92.56 94.33 0.032 Comparative Example 5 86.22 87.19 0.041 Comparative Example 6 98.32 98.67 0.058 Comparative Example 7 72.53 78.22 0.054

[0141] From the data in Table 1 and Table 2, it can be seen that the denitration catalyst with high compressive strength, good wear resistance and high denitration efficiency can be prepared by using the method described in the present invention.

[0142] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a denitration catalyst, characterized in that, The method comprises the following steps: (1) Wet ball-mill the silicon oxide powder, then soak it in a weakly alkaline solution, then separate the solid and liquid, then soak the obtained solid phase in a weakly acidic solution, then separate the solid and liquid, wash and dry to obtain the pretreated silicon oxide powder; wet ball-mill the pretreated silicon oxide powder and titanium dioxide to obtain mixture A; (2) Soak glass fiber A in a first organic solvent, filter, and then wash it with a first organic acid solution to obtain pretreated glass fiber A; (3) Mix a tungsten source and a first aqueous ammonia solution, and then mix it with mixture A to obtain mixture B; (4) Mix ammonium metavanadate and a second aqueous ammonia solution, and then mix it with mixture B to obtain mixture C; (5) First knead the pretreated glass fiber A, mixture C and part of the lubricant to obtain mixture D; (6) Second knead mixture D, glass fiber B, the remaining lubricant, the binder and the plasticizer, then carry out aging, extrusion molding, drying and calcination; Wherein, the length of glass fiber A is 0.2 - 3 mm, and the length of glass fiber B is 3 - 5 mm; In step (1), the solvent used for wet ball-milling the pretreated silicon oxide powder and titanium dioxide is obtained by mixing a second organic solvent and a third aqueous ammonia solution.

2. The method according to claim 1, wherein The weight ratio of the dosage of glass fiber A to glass fiber B is 1:4 - 10.

3. The method according to claim 1, wherein In step (1), the weight ratio of the dosage of the pretreated silicon oxide powder to titanium dioxide is 1:0.5 - 2.

4. The method according to claim 1 or 2, characterized in that, In step (1), the second organic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, acetone and dimethyl ether; and / or The concentration of the third aqueous ammonia solution is 1 - 10 wt%.

5. The method according to claim 1 or 4, characterized in that, In step (1), the time for wet ball-milling the pretreated silicon oxide powder and titanium dioxide is ≥ 30 min.

6. The method according to claim 4, wherein In step (1), the ratio of the volume of the second organic solvent to the total weight of the pretreated silicon oxide powder and titanium dioxide is 2 - 10 mL:1 g; and / or The ratio of the volume of the third aqueous ammonia solution to the total weight of the pretreated silicon oxide powder and titanium dioxide is 2 - 15 mL:1 g.

7. The method according to claim 1, characterized in that, In step (2), the first organic solvent is methanol, ethanol or ethylene glycol; and / or The soaking conditions include: temperature is 50 - 90 °C, time is 30 - 90 min; and / or The organic acid is selected from one or more of citric acid, oxalic acid, acetic acid and tartaric acid; and / or The concentration of the organic acid in the organic acid solution is ≤ 0.2 mol / L.

8. The method according to claim 1 or 7, characterized in that The ratio of the total weight of the pretreated silicon oxide powder and titanium dioxide, the total weight of glass fiber A and glass fiber B, the weight of the tungsten source and the weight of ammonium metavanadate is 70:4 - 7:2 - 5:0.4 - 1.5, wherein, the tungsten source is calculated as WO3, and ammonium metavanadate is calculated as V2O5.

9. The method according to claim 1, wherein In step (5), the conditions for the first kneading include: temperature is 150 - 200 °C, time is 15 - 60 min.

10. The method according to claim 1 or 8, characterized in that In step (6), the conditions for the second kneading include: temperature is 180 - 250 °C, time is 3 - 8 h; and / or The aging time is 30 - 40 h; and / or The calcination is a two-stage continuous calcination process.

11. The method according to claim 1, characterized in that, The lubricant is selected from one or more of glycerol, triethanolamine, and stearic acid; and / or The plasticizer is selected from phthalic acid and / or dioctyl phthalate; and / or The binder is selected from one or more of polyvinyl alcohol, methyl cellulose, hydroxymethyl cellulose, polyacrylamide, and polyethylene glycol.

Images