阅读说明：本技术 高温稳定负载型核壳结构四氧化三钴催化剂及其制备方法和应用 (High-temperature stable supported cobaltosic oxide catalyst with core-shell structure and preparation method and application thereof ) 是由 蔡婷 袁静 刘喆 赵昆峰 金彩虹 于 2019-09-09 设计创作，主要内容包括：本发明公开一种高温稳定的负载型核壳结构四氧化三钴催化剂的制备方法及其产品和应用,该催化剂为Al<Sub>2</Sub>O<Sub>3</Sub>,TiO<Sub>2</Sub>或SiO<Sub>2</Sub>负载的Co<Sub>3</Sub>O<Sub>4</Sub>,负载量为1%~5%。该催化剂是以商用Al<Sub>2</Sub>O<Sub>3</Sub>,TiO<Sub>2</Sub>或SiO<Sub>2</Sub>为载体,以Co(NO)<Sub>3</Sub>6H<Sub>2</Sub>O为钴源,以尿素为沉淀剂,通过沉淀结合热处理的方法得到负载型核壳结构Co<Sub>3</Sub>O<Sub>4</Sub>催化剂。该制备方法主要包括两部分：第一部分先合成前驱体材料,第二部分将前驱体进行热处理得到不同载体负载的核壳结构Co<Sub>3</Sub>O<Sub>4</Sub>催化剂。该工艺不仅制备方法简单,制备的核壳结构Co<Sub>3</Sub>O<Sub>4</Sub>具有高的分散度,且对VOCs和CVOCs均具有良好的催化性能。(The invention discloses a preparation method of a high-temperature stable supported cobaltosic oxide catalyst with a core-shell structure, and a product and application thereof, wherein the catalyst is Al 2 O 3 ，TiO 2 Or SiO 2 Loaded Co 3 O 4 the loading amount is 1% -5%, and the catalyst is commercial Al 2 O 3 ,TiO 2 Or SiO 2 as a carrier, with Co (NO) 3 6H 2 O is used as a cobalt source, urea is used as a precipitator, and the supported core-shell structure Co is obtained by a precipitation and heat treatment method 3 O 4 a catalyst. The preparation method mainly comprises two parts: the first part firstly synthesizes precursor materials, and the second part carries out heat treatment on the precursors to obtain Co with different carrier loads and a core-shell structure 3 O 4 A catalyst. The process is simple, and the prepared Co with the core-shell structure 3 O 4 Having a high degree of dispersionAnd has good catalytic performance on VOCs and CVOCs.)

1. A preparation method of a high-temperature stable supported cobaltosic oxide catalyst with a core-shell structure is characterized in that Al is used₂O₃、TiO₂or SiO₂As a carrier, with Co (NO)₃6H₂O is used as a cobalt source, urea is used as a precipitator, and the supported core-shell structure Co is obtained by a precipitation and heat treatment method₃O₄The catalyst is prepared by a method of combining precipitation and heat treatment, and at least comprises two partial steps of synthesis of a precursor and heat treatment, wherein:

A first part: synthesis of a precursor:

(1) preparing 1mol/L urea aqueous solution;

(2) weighing carrier Al₂O₃、TiO₂or SiO₂dispersing in water to enable the mass ratio of the carrier to the water to be 1/50, and stirring for 15-30 min to obtain a suspension;

(3) with Co₃O₄measured as Co₃O₄weighing cobalt nitrate with the mass ratio of 1-5% to the carrier, and dissolving the cobalt nitrate in the suspension of the carrier in the step (2);

(4) Transferring the suspension into an oil bath kettle at 80 ℃, dropwise adding the urea solution obtained in the step (1) until the pH is =9, and continuously stirring for 2 hours;

(5) Taking out, and aging overnight;

(6) performing suction filtration, washing with deionized water for 3-5 times, and then washing with ethanol for 2-3 times;

(7) drying in a 50 ℃ oven overnight to obtain a precursor;

A second part: and (3) heat treatment:

(1) roasting the obtained precursor in air at 500-800 ℃ for 4-6 h;

(2) Reducing the roasted catalyst in 5-10% hydrogen-argon mixed gas at 300-800 ℃ for 3-5 h;

(3) Passivating the reduced catalyst for 12 hours at room temperature in air;

(4) taken out and then put in a reaction atmosphere (0.1 percent (V)_propanev or V_{Vinyl chloride}v) + air) at 300-500 ℃ for 4-6 h to obtain the high-temperature stable supported cobaltosic oxide catalyst with the core-shell structure.

2. high-temperature stable load type core-shell structure Co₃O₄Catalyst, characterized in that it is obtained by a process according to claim 1, made of Al₂O₃，TiO₂Or SiO₂Loaded Co₃O₄the catalyst has a loading of 1-5%.

3. the high-temperature stable supported core-shell structure Co according to claim 2₃O₄the application of the catalyst VOCs or CVOCs in the catalytic combustion process.

Technical Field

The invention belongs to the technical field of catalytic environmental protection, and particularly relates to a preparation method of a high-temperature stable supported cobaltosic oxide catalyst with a core-shell structure, and a product and application thereof.

Background

Co₃O₄is one of the transition metal oxides having the highest catalytic combustion activity for VOCs. Because the high activity performance of the catalyst is similar to that of noble metals, the catalyst has wide application prospect. But when present alone, tend to agglomerate, resulting in a substantial reduction in activity. The dispersion degree and the stability of the catalyst can be improved by loading the catalyst on a carrier, so that the catalyst is not easy to agglomerate. However, in supported cobalt-based catalysts, the active cobalt species are prone to strong interactions with the support, resulting in reduced activity. In response to this problem, various methods have been proposed to increase the activity of the supported catalyst. The method comprises the following steps of modifying a carrier, doping an active component, carrying out post-treatment (acid, alkali and the like) on a catalyst, and the like so as to improve the catalytic oxidation activity of the catalyst. However, it is difficult to substantially increase the activity of the supported cobalt-based catalyst in any of these ways.

The invention provides high-temperature stable load type core-shell structure Co₃O₄The preparation method of the catalyst mainly comprises the steps of improving the thermal stability of the supported cobalt-based catalyst through high-temperature roasting, and then highly dispersing active components in the supported cobalt-based catalyst on the surface of a carrier through reduction and in-situ reoxidation. By controlling oxidation, high-stability core-shell structure Co is obtained₃O₄A catalyst. The catalyst shows higher catalytic oxidation activity and stability to VOCs and CVOCs. The method provides reference for the preparation of the existing supported cobalt-based catalyst.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a preparation method of a supported cobaltosic oxide catalyst with a core-shell structure, which is stable at high temperature.

yet another object of the present invention is to: provides a high-temperature stable supported type core-shell structure cobaltosic oxide catalyst product prepared by the method.

Yet another object of the present invention is to: provides an application of the product.

The object of the present invention is achieved bythe scheme is realized as follows: a process for preparing the high-temp stable load-type cobaltosic oxide catalyst with core-shell structure from Al₂O₃、TiO₂or SiO₂as a carrier, with Co (NO)₃6H₂o is used as a cobalt source, urea is used as a precipitator, and the supported core-shell structure Co is obtained by a precipitation and heat treatment method₃O₄The catalyst is prepared by a method of combining precipitation and heat treatment, and at least comprises two partial steps of synthesis of a precursor and heat treatment, wherein:

A first part: synthesis of a precursor:

(1) preparing 1mol/L urea aqueous solution;

(2) Weighing carrier Al₂O₃、TiO₂Or SiO₂dispersing in water to enable the mass ratio of the carrier to the water to be 1/50, and stirring for 15-30 min to obtain a suspension;

(3) With Co₃O₄measured as Co₃O₄Weighing cobalt nitrate with the mass ratio of 1-5% to the carrier, and dissolving the cobalt nitrate in the suspension of the carrier in the step (2);

(4) Transferring the suspension into an oil bath kettle at 80 ℃, dropwise adding the urea solution obtained in the step (1) until the pH is about =9, and continuously stirring for 2 hours;

(5) Taking out, and aging overnight;

(6) Performing suction filtration, washing with deionized water for 3-5 times, and then washing with ethanol for 2-3 times;

(7) drying in a 50 ℃ oven overnight to obtain a precursor;

A second part: and (3) heat treatment:

(1) roasting the obtained precursor in air at 500-800 ℃ for 4-6 h;

(2) reducing the roasted catalyst in 5-10% hydrogen-argon mixed gas at 300-800 ℃ for 3-5 h;

(3) passivating the reduced catalyst for 12 hours at room temperature in air;

(4) Taken out and then put in a reaction atmosphere (0.1 percent (V)_PropaneV or V_{Vinyl chloride}v) + air) at 300-500 ℃ for 4-6 h to obtainthe high-temperature stable supported cobaltosic oxide catalyst with the core-shell structure.

The invention obtains a high-stability cobalt-based catalyst by carrying out post-treatment on the supported cobalt-based catalyst on the existing research, compared with the Co existing independently₃O₄it shows high catalytic oxidation activity to both VOCs and CVOCs.

The invention also provides a high-temperature stable load type core-shell structure Co₃O₄Catalyst, prepared according to the process described above, with Al₂O₃，TiO₂Or SiO₂Loaded Co₃O₄the catalyst has a loading of 1-5%.

the invention also provides a high-temperature stable load type core-shell structure Co₃O₄the application of the catalyst VOCs or CVOCs in the catalytic combustion process.

VOCs pollutant gas is simulated by propane standard gas, and the activity evaluation of the catalyst for catalytic combustion is carried out in a fixed bed microreactor (a quartz tube with an inner diameter of 3 mm). The catalyst amount is 100mg, and the temperature is automatically controlled by a K-type thermocouple. The methane/propane standard mixed gas is mixed with air and fed into the reactor to make combustion. The total flow is controlled by a mass flow meter, the concentration of propane is 100ppm, air is used as carrier gas, the concentration of oxygen is 10 percent, the reaction temperature is 50-550 ℃, and the reaction is carried out under the normal pressure environment.

The evaluation of the activity of the catalyst used for the catalytic combustion of vinyl chloride is carried out in a fixed bed microreactor (a quartz tube with an inner diameter of 3 mm), the dosage of the catalyst is 200mg, and the temperature is automatically controlled by a K-type thermocouple. The chloroethylene standard gas is mixed with air and enters a reactor for combustion. The total flow is controlled by a mass flow meter, the concentration of chloroethylene is 0.05 vol%, air is used as carrier gas, the concentration of oxygen is 10%, the reaction temperature is 140-500 ℃, and the reaction is carried out under the normal pressure environment. The relationship between the conversion of vinyl chloride and the reaction temperature is shown in Table 1, wherein T_50%、T_90%The reaction temperatures required for 50% and 90% conversion, respectively. The reaction tail gas is subjected to chromatographic on-line tracking, and the main reaction products are HCl, carbon dioxide, water and a very small amount of trichloroethylene.

Compared with the existing catalyst, the catalyst and the preparation method thereof provided by the invention have the characteristics that: (1) the thermal stability of the existing supported cobalt-based catalyst is improved; (2) a method for increasing the activity of a supported cobalt-based catalyst is provided.

Drawings

FIG. 1 is a TEM image of example 2;

FIG. 2 is a TEM image of example 4.

Detailed Description