CN112316943A

CN112316943A - A low-temperature CO-SCR denitration Cu2O/AC catalyst and its preparation method and application

Info

Publication number: CN112316943A
Application number: CN202011268795.6A
Authority: CN
Inventors: 黄帮福; 汪德富; 施哲; 张桂芳; 李露; 代蒙; 杨征宇; 文桢晶; 李婉君; 周晓雷; 阴树标; 漆鑫
Original assignee: Kunming University of Science and Technology
Current assignee: Kunming University of Science and Technology
Priority date: 2020-11-13
Filing date: 2020-11-13
Publication date: 2021-02-05

Abstract

本发明涉及一种低温CO‑SCR脱硝Cu₂O/AC催化剂及其制备方法与应用，属于烟气净化技术领域。本发明催化剂包括经空气热氧化法活化的椰壳活性炭载体和Cu₂O活性组分，其中Cu₂O活性组分中Cu元素与椰壳活性炭的质量比为0.02‑0.1:1。低温CO‑SCR脱硝Cu₂O/AC催化剂可作为低温催化剂且以CO为还原剂脱除烟气中NO。本发明低温CO‑SCR脱硝Cu₂O/AC催化剂的制备工艺简单、能耗低、铜氧化物分散性好、环保无污染，且具有脱硝效率高、氮选择性好等特点。The invention relates to a low-temperature CO-SCR denitration Cu ₂ O/AC catalyst, a preparation method and application thereof, and belongs to the technical field of flue gas purification. The catalyst of the invention comprises a coconut shell activated carbon carrier activated by an air thermal oxidation method and a Cu ₂ O active component, wherein the mass ratio of Cu element and coconut shell activated carbon in the Cu ₂ O active component is 0.02-0.1:1. The low-temperature CO-SCR denitration Cu ₂ O/AC catalyst can be used as a low-temperature catalyst to remove NO in flue gas with CO as a reducing agent. The low-temperature CO-SCR denitration Cu ₂ O/AC catalyst of the invention has the advantages of simple preparation process, low energy consumption, good copper oxide dispersion, environmental protection and no pollution, and has the characteristics of high denitration efficiency, good nitrogen selectivity and the like.

Description

Low-temperature CO-SCR denitration Cu2O/AC catalyst, preparation method and application thereof

Technical Field

The invention relates to low-temperature CO-SCR denitration Cu₂An O/AC catalyst, a preparation method and application thereof, which belong to the technical field of flue gas purification.

Background

At present, the flue gas denitration technology is most widely applied to a Selective Catalytic Reduction (SCR) process, but the technology still has the problems of poor low-temperature denitration performance, easy blockage of pore channels, easy poisoning and the like in the application process.

In addition, the SCR process requires the use of easily fugitive and highly corrosive NH during the denitration process₃As reducing agent, NH₃Is easy to react with SO in flue gas₂、H₂O, etc. form ammonium salts to poison and deactivate the SCR catalyst.

Disclosure of Invention

Aiming at the problems of the SCR process in the flue gas denitration in the prior art, the invention provides a low-temperature CO-SCR denitration Cu₂The invention relates to an O/AC catalyst, a preparation method and application thereofCO as reducing agent and NO at low temperature_XRemoving; can solve the problems of low-temperature denitration rate, easy blockage of pore channels, easy poisoning and the like of the SCR process catalyst in the prior flue gas denitration.

Low-temperature CO-SCR denitration Cu₂The O/AC catalyst comprises coconut shell activated carbon carrier activated by air thermal oxidation and Cu₂O active component of which Cu₂The mass ratio of the Cu element in the O active component to the coconut shell active carbon is 0.02-0.1: 1; if the mass ratio of the copper element is too large, the active component copper oxide can be agglomerated, so that the pore channel is blocked, the active sites are covered, and the denitration activity of the catalyst is reduced due to insufficient active sites;

the particle size of the coconut shell activated carbon carrier is 20-40 meshes.

The low-temperature CO-SCR denitration Cu₂The preparation method of the O/AC catalyst comprises the following specific steps:

(1) adding coconut shell activated carbon into deionized water, performing ultrasonic oscillation treatment for 2-3h, performing solid-liquid separation, and performing vacuum drying on the solid to obtain pretreated coconut shell activated carbon;

(2) activating the coconut shell activated carbon pretreated in the step (1) by an air thermal oxidation method to obtain an activated AC carrier;

(3) adding the activated AC carrier obtained in the step (2) into a copper nitrate solution, performing ultrasonic impregnation treatment for 2-3h at the temperature of 60-80 ℃, performing solid-liquid separation, and performing vacuum drying on the solid to obtain impregnated AC;

(4) under the atmosphere of protective gas, the dipping AC in the step (3) is heated to 350-600 ℃ at a constant speed and is roasted at a constant temperature for 4-6h to obtain the low-temperature CO-SCR denitration Cu₂An O/AC catalyst;

the temperature for activating the air thermal oxidation method in the step (2) is 350-400 ℃, and the time is 2-3 h;

the concentration of the copper nitrate solution in the step (3) is 0.031-0.157 g/mL;

the protective atmosphere in the step (4) is nitrogen atmosphere;

the low-temperature CO-SCR denitration Cu₂The O/AC catalyst can be used as a low-temperature catalyst for removing NO in the flue gas;

further, in the application of removing NO in the flue gas, CO is used as a reducing agentThe catalytic temperature is 100-400 ℃; CO is adopted as reducing gas, and the problem of the conventional reducing agent NH can be solved₃Easy escape.

The coconut shell activated carbon is activated by adopting an air thermal oxidation method, so that the surface functional groups of the coconut shell activated carbon can be greatly improved, the specific surface area is increased, and the pore volume and the pore diameter in the activated carbon are improved; the ultrasonic impregnation method effectively ensures the dispersibility of the copper element on the surface of the catalyst, thereby ensuring the characteristics of high denitration activity, good nitrogen selectivity and the like, ensuring the dispersibility of the copper element on the surface of the activated carbon and effectively reducing the clustering phenomenon of copper oxide; adding the impregnated activated carbon into N₂And roasting under the protection of atmosphere to convert the copper nitrate precursor into cuprous oxide.

The invention has the beneficial effects that:

(1) the invention takes cheap coconut shell activated carbon as a carrier and cuprous oxide as an active component to realize the reaction of NO with CO as a reducing agent under the condition of low temperature_XRemoving; the problems that the low-temperature denitration rate of the SCR process catalyst is low, pore channels are easy to block, poisoning is easy and the like in the existing flue gas denitration can be solved;

(2) the invention discloses low-temperature CO-SCR denitration Cu₂The O/AC catalyst has higher denitration efficiency and excellent nitrogen selectivity, and the NO conversion rate can reach 97.9% at the catalytic temperature of 100-400 ℃;

(3) the method adopts an air thermal oxidation method to activate the coconut shell activated carbon, improves the surface active functional groups of the coconut shell activated carbon, increases the specific surface area and improves the pore volume and pore diameter in the activated carbon; active components are activated and ultrasonically dipped by a carrier air thermal oxidation method, so that the Cu content is greatly improved₂The dispersibility of copper elements on the surface of the O/AC catalyst;

(4) the invention adopts CO to replace the traditional NH₃As a reducing gas, NH can be solved₃Can solve the problems of toxic gas, easy escape, pipeline blockage, environmental pollution and the like and can also solve the problem of NH₃Can react with SO in the flue gas₃The ammonium sulfate generated by the reaction corrodes downstream equipment, and the like.

Drawings

FIG. 1 shows different active components Cu₂SEM picture of catalyst for O content;

FIG. 2 shows different active components Cu₂Catalyst XRD pattern of O content;

FIG. 3 shows that the catalytic temperature is 150 ℃, and different active components Cu of the catalyst₂Influence of O content on denitration rate is shown;

FIG. 4 is 8% Cu₂FTIR plots for O/AC at various firing temperatures;

FIG. 5 shows the baking temperature vs. 8% Cu₂The O/AC denitration rate.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.

Example 1: low-temperature CO-SCR denitration Cu₂The O/AC catalyst comprises coconut shell activated carbon carrier activated by air thermal oxidation and Cu₂O active component of which Cu₂The mass ratio of the Cu element in the O active component to the coconut shell activated carbon is 0.02-0.1:1, namely the Cu element content in the catalyst is 2-10% and the particle size of the coconut shell activated carbon carrier is 20-40 meshes, wherein the mass of the coconut shell activated carbon is 100%;

low-temperature CO-SCR denitration Cu₂The preparation method of the O/AC catalyst comprises the following specific steps:

(1) adding coconut shell activated carbon into deionized water, performing ultrasonic oscillation treatment for 2h, performing solid-liquid separation, and performing vacuum drying on the solid to obtain pretreated coconut shell activated carbon;

(2) activating the coconut shell activated carbon pretreated in the step (1) by an air thermal oxidation method to obtain an activated AC carrier; wherein the temperature of the air thermal oxidation activation is 350 ℃, and the time is 2 h;

(3) adding the activated AC carrier obtained in the step (2) into a copper nitrate solution, performing ultrasonic impregnation treatment for 2 hours at the temperature of 60 ℃, performing solid-liquid separation, and performing vacuum drying on the solid to obtain impregnated AC; wherein the concentration of the copper nitrate solution is 0.031-0.157 g/mL; the solid-to-liquid ratio g: mL of the activated AC carrier to the copper nitrate solution is constant to be 1: 2.5;

(4) under the protective gas atmosphere (nitrogen), the dipping AC in the step (3) is heated to 500 ℃ at a constant speed and roasted at a constant temperature for 4 hours to obtain the low-temperature CO-SCR denitration Cu₂An O/AC catalyst;

low-temperature CO-SCR denitration Cu₂The Cu content of the O/AC catalyst is shown in Table 1;

TABLE 1 Low temperature CO-SCR denitrated Cu₂Cu element content in O/AC catalyst

Sample number	1	2	3	4	5	Control sample
							Cu element content	2％	4％	6％	8％	10％	0

Different active component Cu₂The SEM image of the catalyst with O content is shown in FIG. 1, wherein a is 0Cu₂O/AC, b is 2Cu₂O/AC, c is 4Cu₂O/AC, d is 6Cu₂O/AC, e is 8Cu₂O/AC, f is 10Cu₂O/AC; as can be seen from FIG. 1, Cu is supported₂After O, the active carbon still keeps the pore diameter structure of the substrate, Cu₂Uniform distribution of OThe catalyst is dispersed on the surface of an AC pore channel, is spherical and has uniform size, so that the active sites and the specific surface area of the catalyst in contact with reaction gas can be greatly increased, and the rapid progress of CO-SCR reaction is promoted;

different active component Cu₂The specific surface area of the catalyst and the pore volume and pore size distribution with respect to the O content are shown in Table 2.

TABLE 2500 deg.C Cu₂Pore size parameter of O/AC catalyst

As can be seen from Table 2, the specific surface area and pore volume of the catalyst increased with increasing loading, due to Cu₂The addition of the O active component causes the aperture to be reduced, but does not influence the reduction performance, and a new pore channel is generated on the basis of the original pore channel to improve the catalytic capability;

different active component Cu₂The XRD pattern of the catalyst with O content is shown in FIG. 2, and from FIG. 2, Cu (NO) can be seen₃)₂Interaction of metal precursors with AC surface functional groups to effect Cu⁺Easily migrate into the AC hole and slow down Cu₂The O is condensed and grown on the AC surface, and the Cu is improved₂O dispersion on AC; from 8% Cu₂The XRD characterization pattern of O/AC shows that the peak at each angle is not sharp, which indicates that Cu₂The dispersibility of O in the AC load is good, and the O plays a role in promoting the denitration reaction;

the low-temperature CO-SCR denitration Cu of the embodiment₂Taking an O/AC catalyst and common coconut shell activated carbon (purchased from Henan Jiangyi blue sky Water purification technology Co., Ltd.) as denitration raw materials, respectively carrying out denitration reaction at 100-400 ℃, wherein the loading amount of the catalyst is 10 g; using N before the experimental test starts₂Introducing the mixture into a fixed bed reactor at 200 ℃ for in-situ flushing, and discharging other gases in the reactor for interference so as to avoid the interference of other gases;

simulated smoke (NO 16ml/min, CO 16ml/min, O)₂5% of balance gas N₂) Mixing and feeding into a fixed bed reactor, and reducing NO into N by CO under the action of a catalyst₂(ii) a After the reactionThe gas is discharged into the atmosphere after unreacted NO and CO are absorbed by limestone solution; the NO concentrations at the inlet and the outlet of the fixed bed reactor evaluation device are detected by a TESTO-340 flue gas analyzer of Germany Degraph instruments, and the denitration conversion rate is calculated by adopting the following formula:

different active component Cu₂The influence of the catalyst with the O content on the denitration rate (the denitration temperature is 150 ℃) is shown in figure 3, and as can be seen from figure 3, when the denitration temperature is 150 ℃, the loading is 4% -8%, and the denitration rate of the catalyst calcined at 500 ℃ for 4 hours is kept above 85%; different active component Cu₂The denitration rates of the O-loaded catalysts are different, and when the O-loaded catalysts are loaded to 8%, the denitration rate can reach 97.9%.

Example 2: low-temperature CO-SCR denitration Cu₂The O/AC catalyst comprises coconut shell activated carbon carrier activated by air thermal oxidation and Cu₂O active component of which Cu₂The mass ratio of the Cu element in the O active component to the coconut shell activated carbon is 0.08:1, namely the Cu element content in the catalyst is 8% and the particle size of the coconut shell activated carbon carrier is 20-40 meshes, wherein the mass of the coconut shell activated carbon is 100%;

low-temperature CO-SCR denitration Cu₂The preparation method of the O/AC catalyst is basically the same as that of the embodiment 1, except that the constant temperature roasting temperature for dipping AC is 350 ℃, 400 ℃, 450 ℃, 500 ℃ and 550 ℃ in sequence;

example 8% Cu₂The FTIR chart at each O/AC firing temperature is shown in FIG. 4, and it can be seen from FIG. 4 that 8% Cu₂O/AC catalyst at 3440cm^-1Is in a reinforced state with 1630cm as carboxyl and O-H stretching vibration absorption peak in chemisorption water^-1The asymmetric vibration absorption peak of the lactone group becomes more obvious, and a small amount of nitrogen-containing functional groups are found on the surface of the catalyst; along with the rise of the roasting temperature, adsorption sites such as oxygen-containing functional group carboxyl, lactone group and the like on the surface of the catalyst are continuously increased;

example 8% Cu₂O/AC roastingThe influence of the temperature on the denitration rate (denitration catalyst temperature: 150 ℃ C.) is shown in FIG. 5, and it can be seen from FIG. 5 that the calcination temperature is 8% Cu in the catalyst₂The influence of the activity of O/AC is large, and the denitration rate is only 65% when the roasting temperature is 350 ℃; when the roasting temperature is 500 ℃, the denitration rate is as high as 97.9 percent, and when the roasting temperature is 550 ℃, the denitration rate is reduced to 88.5 percent; with increasing temperature, NO_XThe removal efficiency of (a) shows a tendency to increase from 67.5% at 350 c to 97.9% at 500 c, since the crystallinity and the kind of the metal oxide on the surface of the AC catalyst increase with the rise of the calcination temperature.

While the present invention has been described in detail with reference to the specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims

1. A low-temperature CO-SCR denitration Cu ₂ O/AC catalyst, characterized in that: comprising a coconut shell activated carbon carrier and a Cu ₂ O active component activated by air thermal oxidation, wherein Cu element in the Cu ₂ O active component The mass ratio to coconut shell activated carbon is 0.02-0.1:1.

2 . The low-temperature CO-SCR denitration Cu ₂ O/AC catalyst of claim 1 , wherein the particle size of the coconut shell activated carbon carrier is 20 to 40 meshes. 3 .

3. the preparation method of the low temperature CO-SCR denitration Cu ₂ O/AC catalyst described in claim 1 or 2, is characterized in that, concrete steps are as follows:

(1) Add coconut shell activated carbon into deionized water for ultrasonic vibration treatment for 2-3 hours, separate solid from liquid, and dry the solid in vacuum to obtain pretreated coconut shell activated carbon.

(2) The activated AC carrier is obtained by performing air thermal oxidation activation on the pretreated coconut shell activated carbon in step (1).

(3) adding the activated AC carrier in step (2) into the copper nitrate solution, ultrasonically impregnating it at a temperature of 60-80° C. for 2-3 hours, separating the solid from the liquid, and drying the solid in vacuum to obtain the impregnated AC.

(4) Under a protective gas atmosphere, the step (3) is immersed in AC and heated to 350-600° C. at a constant speed and calcined at a constant temperature for 4-6 hours to obtain a low-temperature CO-SCR denitration Cu ₂ O/AC catalyst.

4 . The method for preparing a low-temperature CO-SCR denitration Cu ₂ O/AC catalyst according to claim 3 , wherein the activation temperature of step (2) by air thermal oxidation is 350-400° C. and the time is 2-3 h. 5 .

5 . The method for preparing a low-temperature CO-SCR denitration Cu ₂ O/AC catalyst according to claim 3 , wherein the concentration of the copper nitrate solution in step (3) is 0.031-0.157 g/mL. 6 .

6 . The application of the low-temperature CO-SCR denitration Cu ₂ O/AC catalyst of claim 1 as a low-temperature catalyst for removing NO in flue gas. 7 .

7. The application according to claim 6, characterized in that: CO is a reducing agent, and the catalytic temperature is 100-400°C.