阅读说明：本技术 高-低温脱硝催化剂及其制备方法 (High-low temperature denitration catalyst and preparation method thereof ) 是由 刘少光 刘沁昱 于 2019-09-18 设计创作，主要内容包括：本发明公开了一种高-低温脱硝催化剂及其制备方法。该方法包括以下步骤：将纳米二氧化钛、纳米二氧化锆、五氧化二钽、三氧化二锑与稀硫酸溶液混合均匀,浸润30-45分钟得到第一混合物；将偏钨酸铵、七钼酸铵、偏钒酸铵、铈盐、钐盐、钕盐、铬盐、铁盐、铜盐和质量浓度为15％的氨水、醇胺混合均匀,再加入85-90℃的去离子热水,直至完全溶解成第二溶液；将第二溶液加入到第一混合物中,并加入碳纤维丝、聚环氧乙烷、甲基纤维素、磷酸、纳米氧化铝,然后搅拌混炼均匀制成胶泥坯体；将胶泥坯体经过24-30h陈腐后挤出成蜂窝状,经过20-70℃程序升温干燥180-220h后,再经过550-630℃焙烧28-36h,制成高-低温脱硝催化剂。本发明的高-低温脱硝催化剂在150-430℃长期高效,具有优异的耐硫、抗中毒能力,较高的强度。(The invention discloses a high-low temperature denitration catalyst and a preparation method thereof. The method comprises the following steps: uniformly mixing nano titanium dioxide, nano zirconium dioxide, tantalum pentoxide, antimony trioxide and a dilute sulfuric acid solution, and soaking for 30-45 minutes to obtain a first mixture; uniformly mixing ammonium metatungstate, ammonium heptamolybdate, ammonium metavanadate, cerium salt, samarium salt, neodymium salt, chromium salt, iron salt and copper salt with ammonia water and alcohol amine with the mass concentration of 15%, and adding deionized hot water with the temperature of 85-90 ℃ until the mixture is completely dissolved into a second solution; adding the second solution into the first mixture, adding carbon fiber filaments, polyethylene oxide, methyl cellulose, phosphoric acid and nano aluminum oxide, and then stirring and mixing uniformly to prepare a cement blank; and (3) ageing the cement blank for 24-30h, extruding the cement blank into a honeycomb shape, carrying out programmed heating and drying at 20-70 ℃ for 180-36 h, and roasting at 550-630 ℃ for 28-36h to prepare the high-low temperature denitration catalyst. The high-low temperature denitration catalyst disclosed by the invention is efficient for a long time at the temperature of 150-.)

1. A preparation method of a high-low temperature denitration catalyst is characterized by comprising the following steps:

step 1, uniformly mixing 65-75 parts by weight of nano titanium dioxide, 10-15 parts by weight of nano zirconium dioxide, 0.3-0.5 part by weight of tantalum pentoxide, 1-3 parts by weight of antimony trioxide and 27-38 parts by weight of dilute sulfuric acid solution, and soaking for 30-45 minutes to obtain a first mixture;

step 2, uniformly mixing 5-7 parts by weight of ammonium metatungstate, 4-6 parts by weight of ammonium heptamolybdate, 0.5-1.5 parts by weight of ammonium metavanadate, 2-6 parts by weight of cerium salt, 3-5 parts by weight of samarium salt, 2-4 parts by weight of neodymium salt, 1-4 parts by weight of chromium salt, 1-3 parts by weight of iron salt, 3-6 parts by weight of copper salt, 12-16 parts by weight of ammonia water with the mass concentration of 15-25% and 2-5 parts by weight of alcohol amine, and then adding 8-18 parts by weight of water with the temperature of 85-90 ℃ until the ammonium metatungstate, the ammonium heptamolybdate, the iron salt, the copper salt, the ammonia water and the alcohol amine are completely dissolved to form a second solution;

step 3, adding the second solution into the first mixture, and adding 1.0-2.2 parts by weight of carbon fiber filaments, 1.3-2.8 parts by weight of polyethylene oxide, 1.5-2.7 parts by weight of methyl cellulose and 2-4 parts by weight of phosphoric acid H ₃PO ₄2-4 parts of nano alumina by weight, and then uniformly stirring and mixing to prepare a cement blank;

and 4, ageing the cement blank for 24-30 hours, extruding the cement blank into a honeycomb shape, carrying out programmed heating and drying at 20-70 ℃ for 220 hours, and roasting at 550-630 ℃ for 28-36 hours to prepare the high-low temperature denitration catalyst.

2. The method of preparing a high-low temperature denitration catalyst according to claim 1, wherein the cerium salt, samarium salt, neodymium salt, chromium salt, iron salt, copper salt is nitrate.

3. The method of preparing a high-low temperature denitration catalyst according to claim 1, wherein the alcohol amine is ethanolamine.

4. The method as claimed in claim 1, wherein the number average molecular weights of the polyethylene oxide and the methylcellulose are 6000000-8000000 and 10000-30000 respectively, and the mixture is pre-stirred uniformly in proportion for use.

5. The method for preparing a high-low temperature denitration catalyst according to claim 1, wherein in the step 1, the dilute sulfuric acid solution is a deionized sulfuric acid water solution with a mass concentration of 0.5-2.5%.

6. The method as claimed in claim 1, wherein the nano titanium dioxide has an anatase structure, a nanocrystal size of 5-10nm, a specific surface area of 140-200m ²Per g, containing SO ₃The content is 3-8 wt%.

7. The preparation method of the high-low temperature denitration catalyst according to any one of claims 1 to 6, wherein the carbon fiber filaments are 1K chopped fibers, have a length of 3-8mm, are uniformly mixed with nano alumina, and are then proportionally and previously mixed with phosphoric acid H ₃PO ₄Stirring evenly, and standing for later use.

8. A high-low temperature denitration catalyst, comprising a carrier and an active element composite structure distributed on the carrier, wherein the active element composite structure comprises a main active element and an auxiliary active element and is represented by the following formula I:

wherein each Va is independently a primary active element selected from vanadium, cerium, tantalum, chromium, and iron;

each T is independently a co-activating element selected from samarium, neodymium, antimony, tungsten, molybdenum, and copper.

9. The high-low temperature denitration catalyst according to claim 8, wherein the support comprises nano titania modified with ammonium metatungstate and ammonium heptamolybdate.

10. The high-low temperature denitration catalyst according to claim 8 or 9, further comprising nano zirconia uniformly dispersed in the carrier.

Technical Field

The invention relates to the field of flue gas denitration, and particularly relates to a high-low temperature denitration catalyst and a preparation method thereof.

Background

As is well known, Nitrogen Oxides (NO) _x) Can cause serious environmental dangerHarmful to human body and affecting human health. Therefore, NO reduction by various technical means and processes _xEmissions have become a common general consensus and have formulated strict NO _xThe emission standard of (1).

In China, coal-fired power generation is the main energy supply form, and NO generated by a coal-fired power generation boiler _xOccupies China NO _xA greater portion of the total emissions is reduced, thereby reducing NO in large coal-fired power generation boilers _xThe amount of discharge is very important. For this reason, China made corresponding NO _xUltra-low emission standard (less than or equal to 50 mg/Nm) ³) The denitration technology and the denitration process mainly adopt a medium-high temperature selective catalytic reduction method (medium-high temperature SCR method), and account for more than 90 percent. Even so, NO still exists when the unit load is adjusted bee and the boiler is started and stopped _xThe reason for the excessive emissions is that the flue gas temperature of the denitration reactor is lower than 300 ℃ in the process. At present, all medium-high temperature SCR denitration devices and catalysts used in the same are only suitable for being used in the range of 300-420 ℃, and the adopted catalyst is V ₂O ₅/TiO ₂The catalyst can only be used in the smoke with the temperature of above 300 ℃, otherwise, the denitration can be carried out under the smoke condition with the temperature of below 300 ℃, the catalyst can have serious sulfur oxide poisoning and water poisoning, and the poisoning process is irreversible.

Aiming at NO in atmosphere of China _xThe severe reality that the concentration and haze are high, and the national ministry of ecological environment further provides 'full load and full working condition' NO of coal-fired units _xThe requirement of standard emission, namely the denitration system must be used within the range of 220 ℃ and 420 ℃ and cannot be over-exhausted. The existing SCR denitration catalyst can not meet the requirement of long-term use in the range of 220-420 ℃ without failure, and can not be used in the wide range of 150-430 ℃, and the existing catalyst generally exists: (1) it is easy to be poisoned and can not be recovered at low temperature; (2) the strength is low, and the material is easy to break and collapse; (3) the specific surface area is small, and the catalytic activity is low; (4) the temperature change range is large, and the catalyst is easy to have thermal shock cracking. Therefore, a catalyst having excellent denitration performance and mechanical properties and strong poisoning resistance over a wide temperature range is required.

Disclosure of Invention

In order to solve the problems that the denitration catalyst in the prior art can only be used at the temperature of more than 300 ℃ and has low denitration efficiency, no sulfur resistance, easy poisoning, low strength and the like when used at the temperature of less than 300 ℃, the invention provides the high-low temperature denitration catalyst which can be used at the temperature of 150-430 ℃ for a long time and has high efficiency, sulfur resistance, strong poisoning resistance and high strength, and the preparation method thereof.

According to an aspect of the present invention, there is provided a method for preparing a high-low temperature denitration catalyst, comprising the steps of:

step 1, uniformly mixing 65-75 parts by weight of nano titanium dioxide, 10-15 parts by weight of nano zirconium dioxide, 0.3-0.5 part by weight of tantalum pentoxide, 1-3 parts by weight of antimony trioxide and 27-38 parts by weight of dilute sulfuric acid solution, and soaking for 30-45 minutes to obtain a first mixture;

step 2, uniformly mixing 5-7 parts by weight of ammonium metatungstate, 4-6 parts by weight of ammonium heptamolybdate, 0.5-1.5 parts by weight of ammonium metavanadate, 2-6 parts by weight of cerium salt, 3-5 parts by weight of samarium salt, 2-4 parts by weight of neodymium salt, 1-4 parts by weight of chromium salt, 1-3 parts by weight of iron salt, 3-6 parts by weight of copper salt, 12-16 parts by weight of ammonia water with the mass concentration of 15-25% and 2-5 parts by weight of alcohol amine, and then adding 8-18 parts by weight of water with the temperature of 85-90 ℃ until the ammonium metatungstate, the ammonium heptamolybdate, the iron salt, the copper salt, the ammonia water and the alcohol amine are completely dissolved to form a second solution;

step 3, adding the second solution into the first mixture, and adding 1.0-2.2 parts by weight of carbon fiber filaments, 1.3-2.8 parts by weight of polyethylene oxide, 1.5-2.7 parts by weight of methyl cellulose and 2-4 parts by weight of phosphoric acid H ₃PO ₄2-4 parts of nano alumina by weight, and then uniformly stirring and mixing to prepare a cement blank;

and 4, ageing the cement blank for 24-30 hours, extruding the cement blank into a honeycomb shape, carrying out programmed heating and drying at 20-70 ℃ for 220 hours, and roasting at 550-630 ℃ for 28-36 hours to prepare the high-low temperature denitration catalyst.

Preferably, the cerium salt, samarium salt, neodymium salt, chromium salt, iron salt and copper salt are nitrates.

The alcohol amine is ethanolamine.

Specifically, the number average molecular weights of the polyethylene oxide and the methyl cellulose are 6000000-.

Specifically, in the step 1, the dilute sulfuric acid solution is a 0.5-2.5% sulfuric acid deionized water solution.

Preferably, the nano titanium dioxide is of an anatase structure, the size of the nano crystal particle is 5-10nm, and the specific surface area is 140-200m ²Per g, containing SO ₃The content is 3-8 wt%.

Preferably, the carbon fiber filaments are 1K chopped fibers with the length of 3-8mm, are uniformly mixed with the nano-alumina and then are pre-mixed with the phosphoric acid H in proportion ₃PO ₄Stirring evenly, and standing for later use.

According to another aspect of the present invention, there is provided a high-low temperature denitration catalyst comprising a carrier and an active element composite structure distributed on the carrier, wherein the active element composite structure comprises a main active element and an auxiliary active element and is represented by the following formula I:

wherein each Va is independently a primary active element selected from vanadium, cerium, tantalum, chromium, and iron;

each T is independently a co-activating element selected from samarium, neodymium, antimony, tungsten, molybdenum, and copper.

Preferably, the carrier comprises nano titanium dioxide modified by ammonium metatungstate and ammonium heptamolybdate.

Specifically, the high-low temperature denitration catalyst further comprises nano zirconium dioxide uniformly dispersed in the carrier.

Therefore, the high-low temperature denitration catalyst has excellent denitration catalytic reaction efficiency and anti-poisoning capability in a wider temperature range, and is suitable for being applied in the range of 150 ℃ and 430 ℃.

Detailed Description

The preparation method of the high-low temperature denitration catalyst provided by the invention comprises the following steps:

step 1, uniformly mixing 65-75 parts by weight of nano titanium dioxide, 10-15 parts by weight of nano zirconium dioxide, 0.3-0.5 part by weight of tantalum pentoxide, 1-3 parts by weight of antimony trioxide and 27-38 parts by weight of dilute sulfuric acid solution, and soaking for 30-45 minutes to obtain a first mixture;

step 2, uniformly mixing 5-7 parts by weight of ammonium metatungstate, 4-6 parts by weight of ammonium heptamolybdate, 0.5-1.5 parts by weight of ammonium metavanadate, 2-6 parts by weight of cerium salt, 3-5 parts by weight of samarium salt, 2-4 parts by weight of neodymium salt, 1-4 parts by weight of chromium salt, 1-3 parts by weight of iron salt, 3-6 parts by weight of copper salt, 12-16 parts by weight of ammonia water with the mass concentration of 15-25% and 2-5 parts by weight of alcohol amine, and then adding 8-18 parts by weight of water with the temperature of 85-90 ℃ until the ammonium metatungstate, the ammonium heptamolybdate, the iron salt, the copper salt, the ammonia water and the alcohol amine are completely dissolved to form a second solution;

step 3, adding the second solution into the first mixture, and adding 1.0-2.2 parts by weight of carbon fiber filaments, 1.3-2.8 parts by weight of polyethylene oxide, 1.5-2.7 parts by weight of methyl cellulose and 2-4 parts by weight of phosphoric acid H ₃PO ₄2-4 parts of nano alumina by weight, and then uniformly stirring and mixing to prepare a cement blank;

and 4, ageing the cement blank for 24-30 hours, extruding the cement blank into a honeycomb shape, carrying out programmed heating and drying at 20-70 ℃ for 220 hours, and roasting at 550-630 ℃ for 28-36 hours to prepare the high-low temperature denitration catalyst.

Preferably, in step 1, the nano titanium dioxide is preferably of an anatase structure, the size of the nano crystal particle is 5-10nm, and the specific surface area is 140-200m ²Per g, containing SO ₃The content is 3-8 wt%. Selecting the material with a higher specific surface area (140-200 m) ²Per g) and higher SO ₃Nano TiO with content of 3-8 wt% ₂Is used as carrier for increasing NO _xMolecule and TiO ₂The contact area and probability of the particles and the active ingredient.

The dilute sulfuric acid solution is preferably a 0.5-2.5% sulfuric acid deionized water solution.

In step 1, the Zr outer electronic structure (4 d) of the nano zirconium dioxide ²5s ²) Outer layer electronic structure with titanium (3 d) ²4s ²) Similarly, the atomic radius is larger, the outer layer electrons are more active and easier to transfer, the polarity is larger, and the catalytic reduction effect of the catalyst at high temperature and low temperature can be obviously improved. Adding dilute sulfuric acid solution (such as 0.5-2.5% dilute sulfuric acid deionized water solution) to make SO ₄ ^2-Ion adsorption on TiO ₂Surface of the particles, TiO ₂Outer electron and SO ₄ ^2-Common and biased towards SO ₄ ^2-From this TiO ₂The surface is positively charged (in an electron deficient state), and the state can be transferred to the surface of the active component, so that the number and the strength of Lewis acid sites of the active component are increased. Increase of specific surface area, number of acid sites and acid strength of carrier for catalytic decomposition of NO in large temperature range from high temperature section to low temperature section _xIs very advantageous. The dilute sulfuric acid solution can dissolve the tantalum pentoxide and the antimony trioxide to the maximum extent, so that the dispersibility of the solution is better.

Deionized hot water is preferably added in step 2. Also, the purity requirements of the deionized water used in the present invention are: the conductivity is less than or equal to 0.067 mu S/cm, and the resistivity is more than or equal to 15M omega cm. The purity of the grade is high, and the aim is to reduce Na in water to the maximum extent ⁺、K ⁺、Ca ²⁺、Mg ²⁺In order to increase the catalytic efficiency, since these ions undergo neutralization with the acid sites, deactivating the active sites, and greatly affecting the catalytic reaction.

Further, in step 2, cerium salt, samarium salt, neodymium salt, chromium salt, iron salt, and copper salt are preferably nitrates. Preferably, the alcohol amine is ethanolamine.

Adding ammonium metatungstate and ammonium metavanadate in the step 2 to the nano TiO ₂The carrier is modified, so that the chemical structure stability of the carrier can be improved. On the other hand, ammonium metatungstate and ammonium metavanadate are dispersedly distributed in TiO ₂The surface of the nano-particles is beneficial to increasing the implantation rate and the dispersity of active components added subsequently, so that the catalytic efficiency and the anti-poisoning capability are improved, and the modification effect of the subsequent addition is obviously better than the effect of the pre-addition in the production process of the nano-titanium dioxide powder.

In step 3, the number average molecular weights of the polyethylene oxide (P.E.O) and the Methylcellulose (MC) are 6000000-.

The carbon fiber filament is 1K chopped fiber with the length of 3-8mm, is uniformly mixed with nano alumina and then is pre-mixed with phosphoric acid H in proportion ₃PO ₄The solution is stirred uniformly and allowed to stand (e.g., for 15 minutes) until ready for use.

In the method of the invention, the added Ta outer electronic structure 5d of tantalum pentoxide ³6s ²V outer layer electronic structure 3d with vanadium pentoxide ³4s ²Similarly, but two electron shells are larger, i.e. the atomic radius is larger, so that the outer electron is more active and easier to transfer, and V ₂O ₅Combined ratio of single V ₂O ₅Has better denitration catalytic activity.

In step 3, the short carbon fiber filaments with the length of 3-8mm and 1K are added into the high-low temperature denitration catalyst and are uniformly mixed with the nano alumina, and then the mixture is pre-mixed with H according to the proportion ₃PO ₄The solution is stirred evenly and kept stand for 15 minutes, and the functions of the solution are that ① carbon fiber filaments are firstly mixed with nano-alumina to be beneficial to the carbon fiber filaments to be dispersed evenly, ② nano-alumina and H ₃PO ₄The solution is mixed and reacted to form colloidal Al (H) ₂PO ₄) ₃， Al(H ₂PO ₄) ₃The carbon fiber is coated on the surface of the carbon fiber to bond the carbon fiber and the carrier material together through a strong colloid, thereby improving the strength of the catalyst, avoiding the thermal shock cracking problem of the catalyst caused by large variation range of smoke temperature, and having the effect obviously superior to that of the traditional method for adding glass fiber, ③ Al (H) ₂PO ₄) ₃The colloid also has the function of binder to the nano titanium dioxide powder, the integral strength and the wear resistance of the catalyst are obviously improved, ④ the carbon fiber yarn is coated with Al (H) ₂PO ₄) ₃After the colloid is coated, the phenomenon that the colloid loses the fiber strengthening effect due to oxidation caused by contact with oxygen in the subsequent calcining process is avoided.

The high-low temperature denitration catalyst comprises a carrier and an active element composite structure distributed on the carrier, wherein the active element composite structure comprises a main active element and an auxiliary active element and is represented by the following formula I:

wherein each Va is independently a primary active element selected from vanadium, cerium, tantalum, chromium, and iron;

each T is independently a co-activating element selected from samarium, neodymium, antimony, tungsten, molybdenum, and copper.

The high-low temperature denitration catalyst forms a composite structure with V, Ce, Ta, Cr and Fe (shown as Va) as main active elements and Sm, Nd, Sb, W, Mo and Cu (shown as T) as auxiliary active elements, ammonia can provide H required by Bronsted acid sites (shown as-O-H), the auxiliary active elements T provide Lewis acid sites through electron transfer or help the main active elements Va to obtain the Lewis acid sites (shown as:), and the molecular structural formula of the composite structure and the acid sites is shown as formula I.

In this formula, H-O-and-are the acid sites required to participate in the catalytic reduction reaction. The composite active structure composed of the active elements and the auxiliary active elements has more acid sites, and the H-O-acid sites can adsorb a reducing agent NH ₃And can capture NH in ammonium sulfate ₃Playing a role in decomposing ammonium sulfate; by loss of electrons at the Lewis acid site (i.e. by NO abstraction) _xMiddle O atom) shows a catalytic ability, and the acid site shows a good resistance because it does not react with alkali (earth) metal, arsenic, mercury, and the like.

The high-low temperature denitration catalyst provided by the invention has stable three-dimensional structure property formed by multi-element combination and meets SO ₂、SO ₃The catalyst has good resistance to poisoning substances such as ammonium sulfate, alkali (earth) metal, arsenic, mercury and the like, and has high denitration catalytic activity within the temperature range of 150 ℃ and 430 ℃.

Therefore, the high-low temperature denitration catalyst has a porous structure and the specific surface area can reach 80-100m ²(ii) in terms of/g. And contains a large number of acid sites, and shows excellent denitration catalytic reaction capability and long service life at high temperature and low temperatureIs suitable for being used in the range of 150 ℃ and 430 ℃, particularly suitable for being used in the range of 200 ℃ and 420 ℃.

The present invention is further illustrated by way of the following examples, which are not intended to limit the scope of the invention.