阅读说明：本技术 一种高分散负载型钙钛矿催化剂及其制备方法和应用 (High-dispersion supported perovskite catalyst and preparation method and application thereof ) 是由 龚彩荣 曾丽蓉 于 2018-08-07 设计创作，主要内容包括：本发明公开一种高分散负载型钙钛矿催化剂及其制备方法和应用,催化剂由催化剂载体和催化活性组分构成,其中载体为γ-Al<Sub>2</Sub>O<Sub>3</Sub>,催化剂活性组分为LaCoO<Sub>3</Sub>和LaCo<Sub>0.96</Sub>Pt<Sub>0.04</Sub>O<Sub>3</Sub>中的一种,催化剂活性组分的负载量在10wt％-15wt％。所述催化剂通过溶胶凝胶法和等体积浸渍法相结合制备而成,此制备方法的优点在于操作简便,活性组分的分散性高,充分增加了催化剂活性,将其应用于柴油机尾气净化领域,减小了颗粒物的排放,从而达到空气污染度降低的目的。(The invention discloses a high-dispersion load type perovskite catalyst and a preparation method and application thereof 2 O 3 The active component of the catalyst is LaCoO 3 And LaCo 0.96 Pt 0.04 O 3 In the preparation method, the loading amount of the active component of the catalyst is 10-15 wt%. The catalyst is prepared by combining a sol-gel method and an isometric impregnation methodThe preparation method has the advantages of simple operation, high dispersibility of active components, full increase of catalyst activity, application of the catalyst in the field of diesel engine tail gas purification, and reduction of particulate matter emission, thereby achieving the purpose of reducing air pollution.)

1. The high-dispersion supported perovskite catalyst is characterized by consisting of a carrier of the catalyst and an active component of the catalyst, wherein the carrier is gamma-Al₂O₃The active component of the catalyst is LaCoO₃Or LaCo_0.96Pt_0.04O₃In the catalyst, the loading amount of the active component of the catalyst is 8-15 wt%, and the particle size of the active component of the catalyst is kept between 4 and 6 nm.

2. A highly dispersed supported perovskite catalyst as claimed in claim 1, wherein the loading of the active component of the catalyst is in the range of 10 to 15%.

3. A preparation method of a high-dispersion supported perovskite catalyst is characterized by comprising the following steps:

step 1, mixing lanthanum nitrate and cobalt nitrate or lanthanum nitrate, cobalt nitrate and platinum nitrate according to the active component ratio of a catalyst, uniformly dispersing the mixture in distilled water, adding citric acid with the molar ratio equal to the total metal ions, and uniformly dispersing the mixture to form an impregnation solution;

step 2, weighing a catalyst carrier according to the loading amount of the active components of the catalyst, placing the catalyst carrier into the impregnation liquid obtained in the step 1, and performing equal-volume impregnation at room temperature to load the metal elements onto the catalyst carrier to obtain an impregnated sample;

step 3, heating the impregnated sample obtained in the step 2 to form wet gel, namely heating to 60-80 ℃ at the heating rate of 1-5 ℃/min and preserving the heat for 1-5h to form wet gel; then heating to 120 ℃ at the heating rate of 1-5 ℃/min, and preserving the heat for 5-10h to form dry gel; then raising the temperature to 350-450 ℃ at the temperature raising speed of 5-10 ℃/min for heat preservation so as to completely decompose the citric acid, raising the temperature to 700-800 ℃ at the temperature raising speed of 5-10 ℃/min for heat preservation treatment, and naturally cooling to the room temperature of 20-25 ℃ along with the furnace so as to obtain the high-dispersion load type perovskite catalyst.

4. The process for preparing a highly dispersed supported perovskite catalyst as claimed in claim 3, wherein in the step 1, the dispersion is carried out by magnetic stirring at a rotation speed of 300 to 500rpm or by ultrasonic dispersion for 5 to 10 min.

5. The process for preparing a highly dispersed supported perovskite catalyst as claimed in claim 3, wherein in the step 2, the catalyst is immersed at room temperature of 20-25 ℃ for 12-24h at constant volume.

6. The preparation method of a highly dispersed supported perovskite catalyst as claimed in claim 3, wherein in step 3, heating is performed by using an oven or a crucible in an atmosphere of air to obtain a wet gel and a dry gel in sequence; the high-temperature heat treatment is carried out by using a muffle furnace and taking air as an atmosphere.

7. The preparation method of the highly dispersed supported perovskite catalyst as claimed in claim 3, wherein in the step 3, the temperature is raised to 70-80 ℃ at a temperature raising rate of 3-5 ℃/min and is kept for 3-5h to form wet gel; then the temperature is raised to 110-120 ℃ at the heating rate of 3-5 ℃/min, and the temperature is kept for 7-10h to form xerogel.

8. The process for preparing a highly dispersed supported perovskite catalyst as claimed in claim 3, wherein in the step 3, the holding time for completely decomposing citric acid is 1 to 5 hours, preferably 2 to 4 hours, the holding temperature is 350 ℃ and 400 ℃, and the temperature rising rate is 8 to 10 ℃/min.

9. The method for preparing a highly dispersed supported perovskite catalyst as claimed in claim 3, wherein in step 3, the temperature is raised to 700-800 ℃ at a temperature raising rate of 5-10 ℃/min for 1-5 hours, preferably 3-5 hours, the temperature is raised to 750-800 ℃ at a temperature raising rate of 8-10 ℃/min.

10. Use of a highly dispersed supported perovskite catalyst as claimed in claim 1 or 2 for the catalytic oxidation of soot particulates in diesel exhaust.

Technical Field

The invention belongs to the technical field of diesel engine tail gas purification catalysts, and particularly relates to a preparation method and application of a high-dispersion supported perovskite catalyst for diesel engine tail gas purification, which is applied to catalytic oxidation of soot particles in diesel engine tail gas.

Background

At present, diesel engines are widely used in heavy long-distance transportation due to their excellent characteristics of high stability, high efficiency, etc., however, a series of harmful gases such as particulate matters, carbon monoxide, hydrocarbons, nitrogen oxides, etc. generated therefrom have seriously caused a great reduction in air quality and seriously threatened the environment and human health. Therefore, the treatment of the automobile exhaust emitted by the diesel engine is not slow, and the improvement and development of an efficient and stable exhaust emission treatment technology are the key for solving the problems. Particulate Filters (DPF) are currently one of the most well recognized and most effective technologies for the aftertreatment of automobile exhaust. The filter with a special structure is made of high-temperature-resistant materials serving as a substrate, and can adsorb particulate matters in a filter body in an adsorption mode and recover the performance of the materials through a regeneration device, so that the particulate matter purification effect is achieved. The efficiency of the DPF for filtering particulate matter can reach around 65% -90%. However, it is disadvantageous in that the trapped particulate matter is deposited more and the back pressure is increased as the operating time of the DPF increases, and the service life of the filter is greatly reduced beyond a certain limit, so that it is necessary to periodically remove the particulate matter to restore the operating state. Therefore, the development of catalytic regeneration technology inevitably leads people to focus on the development of efficient and stable catalyst.

According to previous studies, noble metal catalysts and rare earth metal catalysts have great advantages in catalytic oxidation of particulate matter, but it is known that noble metals are expensive and a series of side reactions in the exhaust process cause catalyst failure, failing to achieve the intended effect. The perovskite catalyst is the most studied so far, has the advantages of low price and high stability, and is widely applied to the field of diesel engine tail gas purification.

The perovskite oxide is ideally a cubic crystal, with an alkaline earth metal at the A site coordinated to the neighboring atom 12 and an transition metal element at the B site coordinated to the oxygen element 6 to form a regular octahedral structure. Numerous studies have shown that the B-site metal ion acts as an active center, determining the catalytic activity of the catalyst. Ming-Cai soldiers and the likePreparing B-substituted LaCo1-xRexO by adopting a sol-gel method_3-δThe (x ═ 0.04) type perovskite composite oxide catalyst Re (Pt, Pd, Rh, Au, Ag) was found to have a significantly improved catalytic activity. However, the perovskite oxide nanoparticles in the traditional sense have large particle size which is approximately 100-200nm, and small overall surface area, and cannot well contact with soot particles, so that the advantages of the catalyst cannot be fully exerted. Therefore, the selective development of a supported perovskite catalyst has a great application prospect, and the supported catalyst is favorable for improving the specific surface area of the traditional perovskite catalyst, so that particles can be contacted more fully, and the catalytic activity of the particles is improved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a high-dispersion supported perovskite catalyst and a preparation method and application thereof, namely, the high-efficiency supported perovskite catalyst with low raw material cost, good stability and high dispersibility is provided to overcome the defect of low specific surface area of the traditional perovskite catalyst, the preparation method combining an isometric impregnation method and a sol-gel method is adopted to greatly improve the uniformity of the load, overcome the agglomeration of nano particles and reduce the size of the nano particles. The method can not only improve the specific surface area of the active component of the catalyst, but also meet the requirement of close contact between the active component and carbon smoke particles in the catalytic oxidation process, further improve the automobile exhaust purification effect, and reduce environmental damage caused by atmospheric pollution and threat to human health.

The technical purpose of the invention is realized by the following technical scheme:

the high-dispersion supported perovskite catalyst consists of carrier of catalyst and active component of catalyst, in which the carrier is gamma-Al₂O₃The active component of the catalyst is LaCoO₃Or LaCo_0.96Pt_0.04O₃(i.e., LaCo)_0.96Pt_0.04O_3-δ) The loading amount of the catalyst active component is 8-15 wt% (namely the mass of the catalyst active component/the mass of the catalyst carrier), and preferably 10-15％。

The preparation method of the high-dispersion supported perovskite catalyst comprises the following steps:

step 1, mixing lanthanum nitrate and cobalt nitrate or lanthanum nitrate, cobalt nitrate and platinum nitrate according to the active component ratio of a catalyst, uniformly dispersing the mixture in distilled water, adding citric acid with the molar ratio equal to the total metal ions, and uniformly dispersing the mixture to form an impregnation solution;

in step 1, magnetic stirring is adopted for dispersion, the rotating speed is 300-500 rpm or ultrasonic is adopted for dispersion, and the time is 5-10 min.

In step 1, the two ions (lanthanum + cobalt) and citric acid are in equimolar ratio, or the three ions (lanthanum + cobalt + platinum) and citric acid are in equimolar ratio.

Step 2, weighing a catalyst carrier according to the loading amount of the active components of the catalyst, placing the catalyst carrier into the impregnation liquid obtained in the step 1, and performing equal-volume impregnation at room temperature to load the metal elements onto the catalyst carrier to obtain an impregnated sample;

in step 2, the solution prepared according to the principle of the equal-volume impregnation method is subjected to equal-volume impregnation for 12-24h at the room temperature of 20-25 ℃.

Step 3, heating the impregnated sample obtained in the step 2 to form wet gel, namely heating to 60-80 ℃ at the heating rate of 1-5 ℃/min and preserving the heat for 1-5h to form wet gel; then heating to 120 ℃ at the heating rate of 1-5 ℃/min, and preserving the heat for 5-10h to form dry gel; then raising the temperature to 350-450 ℃ at the temperature raising speed of 5-10 ℃/min for heat preservation so as to completely decompose the citric acid, raising the temperature to 700-800 ℃ at the temperature raising speed of 5-10 ℃/min for heat preservation treatment, and naturally cooling to the room temperature of 20-25 ℃ along with the furnace so as to obtain the high-dispersion load type perovskite catalyst.

In step 3, an oven or a crucible is selected for heating, and the atmosphere is air, so that the wet gel and the xerogel are sequentially obtained.

In step 3, a muffle furnace is selected for high-temperature heat treatment, and air is used as an atmosphere.

In the step 3, heating to 70-80 ℃ at a heating rate of 3-5 ℃/min, and preserving heat for 3-5h to form wet gel; then the temperature is raised to 110-120 ℃ at the heating rate of 3-5 ℃/min, and the temperature is kept for 7-10h to form xerogel.

In step 3, the temperature holding time for completely decomposing the citric acid is 1-5 hours, preferably 2-4 hours, the temperature holding temperature is 350-.

In step 3, the temperature is raised to 700-.

The invention adopts isovolumetric impregnation to synthesize the supported catalyst, can improve the dispersibility of the catalyst on the surface of the carrier, reduce the agglomeration of catalyst nano particles, fully contact with carbon smoke particles and improve the catalytic activity of the catalyst. Compared with the prior art, the sample prepared by doping Pt at the B site has higher catalytic performance, and the catalytic activity is better when the loading amount of the active component of the catalyst is 10 wt%.

Drawings

FIG. 1 is an XRD diffraction pattern of a sample of an embodiment of the present invention.

FIG. 2 shows TEM and HRTEM photographs of a sample obtained in example 1 of the present invention.

FIG. 3 shows TEM and HRTEM photographs of a sample obtained in example 2 of the present invention.

FIG. 4 shows TEM and HRTEM photographs of a sample obtained in example 3 of the present invention.

FIG. 5 shows TEM and HRTEM photographs of a sample obtained in example 4 of the present invention.

FIG. 6 is a graph of conversion rates calculated from thermogravimetric test data for an embodiment of the present invention.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples. According to the research progress of the active alumina carrier in the references of flag of Tang national, Zhang Chunfu, Sun Changshan, harsh bin, Yang national auspicious, Daiwei, Tian Bao Lian]A chemical process, 2011(30), 1756-₂O₃Preparation and water absorption determination of (a), as follows: placing 10-20g of pseudo-boehmite in a muffle furnace, heating to 400-600 ℃ at a heating rate of 3-5 ℃/min, continuously calcining at 400-600 ℃ for 3-5h, and then calcining after the firing is finishedCooling the furnace, namely opening the muffle furnace after the room temperature is 20-25 ℃, and taking out to obtain white powder, namely gamma-Al₂O₃. Weighing 5-10g of the mixture and a beaker, slowly dripping distilled water into the beaker until the mixture just reaches a thin and thick state, recording the total weight as 7.3078g, and calculating to obtain the gamma-Al₂O₃The water absorption was 0.6842, and the muffle furnace was an air atmosphere.