阅读说明：本技术 用于催化燃烧挥发性有机物的非贵金属催化剂及制备方法 (Non-noble metal catalyst for catalytic combustion of volatile organic compounds and preparation method thereof ) 是由 刘勇军 肖敏 于 2020-07-07 设计创作，主要内容包括：本发明公开了用于催化燃烧挥发性有机物的非贵金属催化剂及制备方法。所述非贵金属催化剂包含层状二氧化锰和掺杂金属氧化物。本发明通过在层状氧化锰的层间引入金属氧化物得到用于催化燃烧挥发性有机物的非贵金属催化剂,提高了层状氧化锰的结构稳定性、比表面积和表面活性氧物种数量。经对照试验验证得到,本发明的非贵金属催化剂高、稳定性强,在相同测试条件下,未掺杂改性的层状氧化锰的甲苯完全转化温度(T<Sub>90</Sub>)为230℃,而铜、锶和镍掺杂改性的层状氧化锰催化剂的甲苯完全转化温度(T<Sub>90</Sub>)可降低至196℃。该结果表明,铜、锶和镍掺杂改性的层状氧化锰催化剂的催化性能优越,其性能优于传统商品贵金属催化剂(其T<Sub>90</Sub>一般高于220℃)。(The invention discloses a non-noble metal catalyst for catalytic combustion of volatile organic compounds and a preparation method thereof. The non-noble metal catalyst comprises layered manganese dioxide and a doped metal oxide. According to the invention, the non-noble metal catalyst for catalytic combustion of volatile organic compounds is obtained by introducing the metal oxide between the layers of the layered manganese oxide, so that the structural stability, the specific surface area and the number of surface active oxygen species of the layered manganese oxide are improved. Verified by a contrast testThe non-noble metal catalyst has high stability, and the toluene complete conversion temperature (T) of the undoped modified lamellar manganese oxide is high under the same test condition 90 ) 230 ℃ and the toluene complete conversion temperature (T) of the copper, strontium and nickel doped modified layered manganese oxide catalyst 90 ) Can be reduced to 196 ℃. The results show that the copper, strontium and nickel doped modified layered manganese oxide catalyst has superior catalytic performance, and the performance of the catalyst is superior to that of the traditional commercial noble metal catalyst (T of the catalyst) 90 Typically above 220 c).)

1. A non-noble metal catalyst for catalytic combustion of volatile organic compounds, characterized in that: the non-noble metal catalyst comprises layered manganese dioxide and a doped metal oxide.

2. A non-noble metal catalyst for the catalytic combustion of volatile organic compounds according to claim 1, characterized in that: the doped metal in the doped metal oxide is any one or more of copper, strontium and nickel.

3. A non-noble metal catalyst for the catalytic combustion of volatile organic compounds according to claim 2, characterized in that: the doped metal in the doped metal oxide is copper/strontium.

4. A non-noble metal catalyst for the catalytic combustion of volatile organic compounds according to claim 1, characterized in that: in the non-noble metal catalyst, the molar ratio of the doping metal in the doping metal oxide to the manganese is 0.05-0.3, preferably 0.1-0.2.

5. A non-noble metal catalyst for the catalytic combustion of volatile organic compounds according to claim 1, characterized in that: birnessite or birnessite type MnO is detected at a 2 theta of 12.4 degrees and a 2.1 degree in an X-ray diffraction pattern₂Characteristic diffraction peaks of the '001' and '002' crystal faces, and the average grain size of the non-noble metal catalyst is 5-30 nanometers.

6. A non-noble metal catalyst for the catalytic combustion of volatile organic compounds according to claim 1, characterized in that: the catalyst has a mesoporous structure, an adsorption loop can be observed in a low-temperature nitrogen adsorption curve, and the specific surface area of a non-noble metal catalyst is 20-150 m²/g。

7. The preparation method of the non-noble metal catalyst for catalytic combustion of volatile organic compounds comprises the following steps:

(1) preparing a potassium hydroxide solution; preparing a potassium permanganate solution; preparing a mixed salt solution containing manganese salt and a salt of a doped metal in a doped metal oxide;

(2) firstly, dropwise adding a mixed salt solution into a potassium hydroxide solution, then dropwise adding a potassium permanganate solution, and stirring for a period of time after dropwise adding is finished;

(3) and collecting, washing and precipitating, drying and then carrying out heat treatment to obtain the non-noble metal catalyst.

8. The method of claim 7 for preparing a non-noble metal catalyst for the catalytic combustion of volatile organic compounds, wherein: the manganese salt is selected from one or more of manganese acetate, manganese nitrate and manganese sulfate.

9. The method of claim 7 for preparing a non-noble metal catalyst for the catalytic combustion of volatile organic compounds, wherein: the heat treatment is roasting at 300-500 ℃ for 2-8 h.

10. A method of catalytically combusting volatile organic compounds, characterized by: non-noble metal catalyst prepared with the non-noble metal catalyst according to any one of claims 1 to 6 or with the preparation process according to any one of claims 7 to 9.

Technical Field

The invention relates to the technical field of catalytic combustion of volatile organic compounds, in particular to a non-noble metal catalyst for catalytic combustion of volatile organic compounds and a preparation method thereof.

Background

The large amount of Volatile Organic Compounds (VOCs) emitted by industrial processes is PM_2.5And O₃The main precursor of pollution is an important reason for regional atmospheric problems in China. The catalytic combustion technology is a mainstream technology for controlling VOCs pollution, and has the advantages of low energy consumption, no secondary pollution, convenient operation and the like. The traditional noble metal catalyst has high activity, but has the problems of high price, easy poisoning, easy inactivation and the like. Therefore, the manganese oxide catalyst has wide industrial application prospect due to low price and good activity of catalyzing and oxidizing volatile organic compounds such as toluene and the like.

The manganese oxide includes manganese oxide (MnO), manganese dioxide (MnO)₂) Manganese oxide (Mn)₂O₃) Manganomanganic oxide (Mn)₃O₄) And the like, wherein the catalytic activity of manganese dioxide is the best. The structure and performance of the catalyst are strongly related. MnO₂The layered manganese oxide can be divided into three major structures, namely birnessite with a (1 × ∞) configuration, birnessite or birnessite with a (2 × ∞) configuration and bushel with a (3 × ∞) configuration, wherein the interlayer charge density and the interlayer spacing (d ═ 0.7nm) of the birnessite or birnessite type layered manganese oxide are moderate, and the layered structure has strong ion exchange activity.

Disclosure of Invention

The invention mainly aims to further improve the catalytic activity of birnessite or birnessite type layered manganese oxide in catalytic combustion of volatile organic compounds, and provides a non-noble metal catalyst for catalytic combustion of volatile organic compounds, a preparation method and application thereof by carrying out metal doping modification on the birnessite or birnessite type layered manganese oxide, so as to solve the technical problems of unstable structure, smaller specific surface area and lower catalytic reaction activity of the layered manganese oxide catalyst in the prior art.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a non-noble metal catalyst for catalytic combustion of volatile organic compounds comprises layered manganese dioxide and doped metal oxide.

Further, the doped metal in the doped metal oxide is one or more of copper, strontium and nickel.

Further, the doped metal in the doped metal oxide is copper/strontium.

Further, in the non-noble metal catalyst, the molar ratio of the doping metal in the doping metal oxide to manganese is 0.05-0.3, preferably 0.1-0.2.

Further, birnessite or birnessite type MnO was detected at 12.4 ° and 25.1 ° 2 θ in an X-ray diffraction pattern₂Characteristic diffraction peaks of the '001' and '002' crystal faces, and the average grain size of the non-noble metal catalyst is 5-30 nanometers.

Furthermore, the catalyst has a mesoporous structure, an adsorption loop can be observed in a low-temperature nitrogen adsorption curve, and the specific surface area of the non-noble metal catalyst is 20-150 m²/g。

The preparation method of the non-noble metal catalyst for catalytic combustion of volatile organic compounds comprises the following steps:

(1) preparing a potassium hydroxide solution; preparing a potassium permanganate solution; preparing a mixed salt solution containing manganese salt and a salt of a doped metal in a doped metal oxide;

(2) firstly, dropwise adding a mixed salt solution into a potassium hydroxide solution, then dropwise adding a potassium permanganate solution, and stirring for a period of time after dropwise adding is finished;

(3) and collecting, washing and precipitating, drying and then carrying out heat treatment to obtain the non-noble metal catalyst.

Further, the manganese salt is selected from one or more of manganese acetate, manganese nitrate and manganese sulfate.

Further, the heat treatment is roasting at 300-500 ℃ for 2-8 h.

The method for catalytic combustion of volatile organic compounds adopts the non-noble metal catalyst or the non-noble metal catalyst prepared by the preparation method.

According to the invention, the non-noble metal catalyst for catalytic combustion of volatile organic compounds is obtained by introducing the metal oxide between the layers of the layered manganese oxide, so that the structural stability, the specific surface area and the number of surface active oxygen species of the layered manganese oxide are improved. The non-noble metal catalyst has high stability and the toluene complete conversion temperature (T) of the non-doped modified layered manganese oxide is proved by a control test under the same test condition₉₀) 230 ℃ and the toluene complete conversion temperature (T) of the copper, strontium and nickel doped modified layered manganese oxide catalyst₉₀) Can be reduced to 196 ℃. The results show that the copper, strontium and nickel doped modified layered manganese oxide catalyst has superior catalytic performance, and the performance of the catalyst is superior to that of the traditional commercial noble metal catalyst (T of the catalyst)₉₀Generally above 220 ℃); in conclusion, the catalytic activity of the layered manganese oxide for catalytic oxidation of volatile organic compounds can be remarkably improved by introducing metal oxides such as copper, strontium, nickel and the like into the layered manganese oxide layer.

The invention is further described with reference to the following figures and detailed description. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to assist in understanding the invention, and are included to explain the invention and their equivalents and not limit it unduly. In the drawings:

fig. 1 is a schematic view of a miniature fixed bed apparatus for evaluating the catalytic activity of a non-noble metal catalyst.

FIG. 2 shows the removal efficiency of L-MnO, L-CuMnO, L-SrMnO and L-NiMnO for toluene at different temperatures.

FIG. 3 shows the removal efficiency of ethyl acetate at different temperatures for L-MnO, L-CuMnO, L-SrMnO, and L-NiMnO.

FIG. 4 is an X-ray diffraction pattern of L-MnO, L-CuMnO, L-SrMnO, L-NiMnO.

FIG. 5 shows N in L-MnO, L-CuMnO, L-SrMnO and L-NiMnO₂Adsorption-desorption isotherms (a) and pore size profiles (B).

FIG. 6 shows the removal efficiency of L-CuSrMnO, L-NiSrMnO and L-CuNiMnO for toluene at different temperatures.

FIG. 7 shows the removal efficiency of L-CuSrMnO, L-NiSrMnO and L-CuNiMnO for ethyl acetate at different temperatures.

FIG. 8 is an X-ray diffraction pattern for L-CuSrMnO, L-NiSrMnO and L-CuNiMnO.

Detailed Description

The invention will be described more fully hereinafter with reference to the accompanying drawings. Those skilled in the art will be able to implement the invention based on these teachings. Before the present invention is described in detail with reference to the accompanying drawings, it is to be noted that:

the technical solutions and features provided in the present invention in the respective sections including the following description may be combined with each other without conflict.

Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

With respect to terms and units in the present invention. The terms "comprising," "having," and any variations thereof in the description and claims of this invention and the related sections are intended to cover non-exclusive inclusions.

The preparation method of the non-noble metal catalyst for catalytic combustion of volatile organic compounds comprises the following steps:

(1) preparing a solution:

preparing a potassium hydroxide solution: dissolving 250mmol of potassium hydroxide in 20-200 mL of distilled water;

preparing a potassium permanganate solution: dissolving 6mmol of potassium permanganate in 50-500 mL of distilled water;

preparing a mixed salt solution: dissolving 16mmol of manganese salt and a certain amount of metal-doped salt in 10-100 mL of distilled water; the usage amount of the doped metal salt is determined according to the theoretical calculation molar ratio of the doped metal/Mn in the target product; the resulting layered manganese oxide catalyst was used as a control to illustrate the effect of the doped metal oxide on the catalytic activity of the non-noble metal catalyst when no salt of the doped metal was added.

(2) Firstly, dropwise adding the mixed salt solution into a potassium hydroxide solution, then dropwise adding a potassium permanganate solution, and stirring for 2-24 hours at 20-60 ℃ after dropwise adding.

(3) And collecting, washing and precipitating, drying and roasting for 2-8 hours at the temperature of 300-500 ℃ to obtain the non-noble metal catalyst.

The manganese salt is any one or more of manganese acetate, manganese nitrate and manganese sulfate.

The metal-doped salt is any one or more of metal-doped chloride salt, nitrate and sulfate.

The phase analysis and the crystal structure determination of the non-noble metal catalyst are characterized by powder X-ray diffraction (XRD) by using a PANalyticalX' PertPRO diffractometer and adopting Cu target Ka radiation (lambda is 0.1540598nm), the voltage is 40kV, the current is 30mA, the scanning range 2 theta is 5-80 degrees, and the scanning step is 0.03 degrees. The XRD results were indexed to determine the phase according to the reference data from the international diffraction data centre.

The pore structure of the obtained non-noble metal catalyst adopts an AUTONORB-IQ automatic adsorption instrument to measure N₂And analyzing an absorption and desorption curve. All non-noble metal catalysts were degassed for 6h at 180 ℃ under vacuum before each analysis. Adsorption isotherm number from non-noble metal catalyst using Brunauer-Emmett-teller (bet) equationThe specific surface area and the total pore volume were calculated. The pore size distribution was calculated using the Barrett-Joyner-Halenda (BJH) formula.

The catalytic activity of the obtained non-noble metal catalyst was evaluated using a miniature fixed bed apparatus as shown in fig. 1, and the tests were all performed under normal pressure. In fig. 1, the heating parts outside the reactor are a tubular resistance furnace and an electric heating box, a thermocouple is arranged on the catalyst bed layer inside the reactor and used for measuring the actual temperature of the catalyst bed layer, and the thermocouple, the heating parts and a temperature controller are interlocked with each other to accurately control the temperature of the reactor; toluene or ethyl acetate is used as a target pollutant in the experiment, and dry air is used as an air source. The gas volume space velocity (GHSV) is 30000h^-1The filling volume of the non-noble metal catalyst is 1mL, and the reactor is a quartz tube with the inner diameter of 8 mm. And (3) measuring the concentration of the target pollutant before and after the reaction by using a gas chromatograph. The conversion of the target pollutant was calculated using the following formula:

wherein η is the conversion of the target contaminant, C_inAnd C_outFeed and outlet concentrations of the target contaminant, respectively.

The following describes advantageous effects of the present invention by using specific embodiments and with reference to the drawings.