CN112264007A

CN112264007A - Aromatic compound catalytic combustion catalyst and preparation and application thereof

Info

Publication number: CN112264007A
Application number: CN202011267607.8A
Authority: CN
Inventors: 周永华; 杜旭弘; 林百宁
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2020-11-13
Filing date: 2020-11-13
Publication date: 2021-01-26
Anticipated expiration: 2040-11-13
Also published as: CN112264007B

Abstract

The invention belongs to the technical field of environmental catalysis, and particularly discloses an aromatic compound catalytic combustion catalyst which comprises a wood substrate with a cell wall array structure, wherein a carbon film and graphene oxide coated noble metal nano-particles which are dispersed are compounded on the surface of a skeleton of a cell wall in situ. The invention also provides the preparation of the catalyst and the application of the catalyst in catalyzing the oxidative degradation of aryl compounds such as toluene. The catalyst of the invention has excellent catalytic activity and stability, such as initial conversion temperature (T) when catalyzing toluene₁₀) At 75-100 deg.C, complete conversion temperature (T)₉₀) 135 ℃ and 210 ℃ shows good catalytic activity. In addition, the catalyst also has the advantages of easily obtained raw materials, low cost, environmental friendliness and simple preparation method, and has wide application rangeHas wide application prospect.

Description

Aromatic compound catalytic combustion catalyst and preparation and application thereof

Technical Field

The invention belongs to the field of environmental catalysis, and relates to a catalytic combustion catalyst for aromatic compounds.

Background

Volatile Organic Compounds (VOCs) are major atmospheric pollutants, mainly derived from fuel combustion, industrial manufacturing and solvent emissions, and pose serious hazards to the atmospheric environment and human health. Aromatic compounds, such as toluene, are a major contaminant of VOCs. As a common solvent, toluene is widely applied to the manufacturing industry of chemicals such as decorative materials, paint coatings and the like. How to effectively convert or remove the toluene waste gas generated in various industries has important significance.

Common methods for removing toluene from air are: adsorption, photocatalytic degradation, plasma degradation, non-oxidation combustion, catalytic oxidation (combustion), and the like. The catalytic oxidation method can convert toluene into carbon dioxide and water at a lower temperature by utilizing the catalytic oxidation property of the catalyst, has the advantages of simple operation, low energy consumption, high efficiency, no secondary pollution, wide application range and the like, and is the most effective mode accepted in the world at present.

The catalysts for catalytic combustion of toluene mainly comprise three catalysts: the first is a load type noble metal catalyst, which takes noble metals such as Pt, Pd, Au, Ru and the like as representatives; second, a transition metal oxide catalyst, commonly V₂O₅、MnOx、Co₃O₄、CeO、CuO、Fe₂O₃And the like: and the third is composite oxide catalyst, mainly perovskite type composite oxide and spinel type composite oxide. Transition metal oxides and composite metal oxides are relatively inexpensive, but have problems of high light-off temperature and low catalytic activity. In contrast, the supported noble metal catalyst has better catalytic activity, lower light-off temperature and complete conversion temperature, and is widely researched in the field of catalytic oxidation of VOCs.

The important research point of the supported noble metal catalyst for toluene catalytic combustion is to improve the activity of the catalyst. Generally, the higher the activity of the catalyst, the lower the light-off temperature and the full conversion temperature of toluene. There are two main research directions. One is alloying, namely, the surface electronic property of the active metal is modulated through the interaction between two metals, so that the catalytic activity is improved; the other is to increase the dispersion degree of the metal, namely, the dispersion degree of the metal is increased and the catalytic activity is improved by changing the type of the carrier and optimizing the loading method. For example, patent CN101733165A. CN201110064279 and CN201610223024.2 report that when preparing Pd and Pt monolithic catalysts with cordierite and alumina as carriers, the conversion rate of toluene reaches 99% at the temperature of 182 ℃ and 250 ℃. In addition, compared with Pt, Pd has the advantage of low cost, and is one of the best active components for industrial production and application. CN 109225319 takes SAPO-34 molecular sieve as carrier to prepare Pt/SAPO-34 molecular sieve catalyst, and toluene is catalyzed and combusted at the temperature of 140-250 ℃. CN106362736 reports low-load Pd @ Pt/Al with the load less than 0.05%₂O₃The core-shell structure catalyst can ensure that the toluene is ignited at about 150 ℃ and is completely converted at 220 ℃. CN108906039A reports low-loading Au @ Pt/Al₂O₃The core-shell structure catalyst completely oxidizes toluene at 210 ℃.

In summary, the existing toluene catalytic oxidation catalyst also has a light-off temperature (T)₁₀) And complete conversion temperature (T)₉₀) The temperature is higher.

Disclosure of Invention

Aiming at the technical defects of non-ideal catalytic performance, high light-off temperature and high complete conversion temperature of the existing aromatic compound catalytic combustion catalyst, the invention provides an aromatic compound catalytic combustion catalyst (the invention is also referred to as a catalyst for short) and aims to provide a brand-new catalyst with excellent catalytic activity, lower light-off temperature and complete conversion temperature.

The second purpose of the invention is to provide a preparation method of the catalyst.

The third purpose of the invention is to provide the application of the catalyst in the catalytic combustion of aromatic compounds.

A catalytic combustion catalyst for aromatic compounds comprises a wood substrate with a cell wall array structure, a carbon film compounded on the surface of a skeleton of a cell wall in situ, and graphene oxide-coated noble metal nanoparticles dispersed and distributed.

The invention provides a catalyst with a brand new structure, which innovatively utilizes a primary cell wall structure of wood as a supporting substrate, and a carbon film and graphene oxide coated noble metal nanoparticles (marked as GO @ M) are compounded on the surface of an array skeleton (cell wall framework) of a cell wall in situ. The research shows that the catalyst provided by the invention can unexpectedly improve the catalytic activity of the catalyst in the catalytic combustion process of aromatic compounds, reduce the ignition temperature and the complete conversion temperature, and has excellent structural stability and catalytic cycle stability based on the synergy of components and morphological structures.

In the invention, the wood primary (natural) cell wall biomass framework structure, the carbon film coating structure on the surface of the wood primary (natural) cell wall biomass framework structure and the characteristic of the GO @ M uniform dispersion distribution structure are the keys for endowing the catalyst with excellent catalytic performance in aromatic compounds.

The research of the invention finds that the regulation and control of the wood cell wall framework structure is beneficial to further cooperating with the structural characteristics of the surface in-situ carbon film and GO @ M, and is beneficial to further improving the catalytic activity of the wood cell wall framework in the catalytic combustion process of aromatic compounds.

Preferably, the wood has 40-60 mu m longitudinal through pore channels and 5-15 mu m transverse pores.

Preferably, the wood is broadleaf forest wood, and further preferably is at least one of poplar, fir and zelkova; most preferably poplar. The invention unexpectedly discovers that poplar is adopted as an in-situ biomass framework, and the surface in-situ carbon film and the GO @ M structural characteristics are matched, so that the catalytic activity of the catalyst is further improved.

In the present invention, the control of the composition of the noble metal contributes to further synergistic improvement of the catalytic activity of the catalyst.

Preferably, the noble metal is palladium, platinum or palladium-platinum alloy; palladium is preferred. The research of the invention finds that the palladium is beneficial to further cooperating with the structure to further improve the catalytic performance.

The particle size of the noble metal nano-particles is 1-5 nm.

In the invention, the noble metal is coated by a graphene oxide film, and the thickness of the graphene oxide is not higher than 5 nm.

In the invention, the carbon film is obtained by in-situ conversion on the surface of a cell wall, and the thickness of the carbon film is not more than 5 nm.

Preferably, the noble metal loading is from 0.01 wt% to 0.5 wt%.

The invention also provides a preparation method of the aromatic compound catalytic combustion catalyst, which comprises the following steps:

step (1): putting the wood maintaining the original cell wall array structure into a solution dissolved with a noble metal source; dipping is carried out; then drying to obtain wood loaded with noble metal source;

step (2): reducing the wood loaded with the noble metal source to reduce the noble metal source into a simple substance to obtain the wood loaded with the noble metal simple substance;

and (3): the surface in-situ carbonization is carried out on the wood cell wall skeleton by the wood loaded with the noble metal simple substance under the protective atmosphere and the temperature of 200-350 ℃, so as to prepare the catalyst.

The research of the invention finds that successfully maintaining the primary biomass frame structure of the wood cell wall, avoiding structure collapse, controlling the in-situ conversion degree of the carbon film and the in-situ composite structure of GO @ M are the key points for successfully constructing the material and improving the catalytic combustion performance of the material. Therefore, the invention innovatively finds that the wood is used as a substrate, precious metal nano particles are reduced in a cell wall structure in advance and then the cell wall surface is treated at the required temperature, so that the in-situ carbon coating of the cell wall surface is realized, the cell wall structure is prevented from being carbonized, and the in-situ graphene oxide coating of the precious metal particle surface is also realized. The research of the invention finds that the catalyst with the brand new structure can be unexpectedly constructed and the catalytic performance of the prepared catalyst can be improved based on the raw materials, the dipping-reduction and the controllable surface treatment process at the special temperature.

In the invention, the wood is segment-shaped primary wood. The segment-like structure is different from the conventional crushed raw material and aims to provide a primary cell wall framework structure of wood on the basis of the raw material.

In the present invention, the wood may be stem tissue directly obtained from a segment (block) structure of the original wood, for example, stem tissue (for example, a cylinder) obtained from a cylinder structure of the wood. The length direction of the column is preferably the height direction of the wood.

In the invention, the noble metal source is a water-soluble salt of a noble metal element, preferably at least one of chloride, nitrate, acetate and acetylacetone salt of the noble metal element;

preferably, the temperature of the impregnation process is 0-40 ℃, and further preferably 20-30 ℃;

preferably, the dipping time is 20 to 90 days, and more preferably 30 to 40 days.

The reduction in the step (2) is liquid phase reduction or gas phase reduction.

And (2) the liquid phase reduction refers to that the wood treated in the step (1) is placed in a solution containing a reducing agent, and the reducing agent is utilized to reduce the precious metal source into a simple substance.

The gas-phase reduction refers to: and (3) placing the wood loaded with the noble metal source in a reducing atmosphere for gas-solid reduction in a dosage form.

Preferably, the reduction step is a gas phase reduction.

Preferably, the reducing atmosphere is an atmosphere containing hydrogen.

Preferably, the reduction is carried out at a temperature in the gas phase reduction range of 50-200 deg.C, preferably 100-150 deg.C.

In the present invention, the temperature control of the surface treatment of step (3) is one of the keys to the successful preparation of the catalyst. It was found that the catalytic performance of the material in aromatic compounds can be surprisingly improved based on said temperature control, thereby achieving surface-controlled carbon membrane building of the cell wall framework structure and avoiding carbonization of the overall structure and collapse of the structure primary structure.

Preferably, the temperature of the surface in-situ carbonization process is 200-350 ℃; further preferably 250 to 320 ℃.

Preferably, the time for in situ carbonization of the surface is 0.5 to 5 hours, preferably 1 to 3 hours.

The invention also provides the application of the aromatic compound catalytic combustion catalyst, and the aromatic compound catalytic combustion catalyst is used as a catalyst for catalyzing the oxidative degradation of aromatic compounds.

Preferably, the aromatic compound is at least one of benzene, alkyl substituted benzene and halogenated benzene; more preferably at least one of toluene and xylene.

Preferably, the temperature of the catalytic process is greater than or equal to 75 ℃; preferably 130 to 150 ℃.

Advantageous effects

1. The invention provides a catalyst with a brand-new structure, and finds that the catalyst has unexpected technical effects in the aspect of catalytic combustion of aromatic compounds, has lower ignition temperature and complete conversion temperature, and has excellent structure and cycle stability.

For example, compared with the prior art, the catalyst provided by the invention has the advantages of high catalytic activity (the toluene initiation temperature is 75-100 ℃, the complete conversion temperature is 135 ℃. 210 ℃), low carrier cost, environmental friendliness (economic broadleaf forest), simple preparation method and good stability.

2. The invention also provides a preparation method of the catalyst, which is based on the use of the raw materials and is matched with the cooperation of the impregnation-reduction-surface treatment process, so that the original structure of wood can be successfully maintained, and a carbon film and the graphene oxide coated noble metal particles can be formed on the surface of a cell wall in situ. Based on the control of the preparation process and conditions of the present invention, a catalyst material having excellent performance in catalytic combustion of aromatic compounds can be prepared.

Drawings

FIG. 1 is a high-resolution Transmission Electron Microscope (TEM) image of the Pd/CP catalyst prepared in example 1

FIG. 2 TEM image of poplar

FIG. 3X-ray diffraction spectra (XRD) of Pd/CP and Pd/NP catalysts

As can be seen from figure 1, after the in-situ low-temperature carbonization treatment of the catalyst, the surface of the frame structure is provided with a carbon film, and the surface of the palladium nanoparticles which are dispersed has an obvious GO film.

As can be seen from FIG. 2, the original poplar wood after low temperature carbonization remains intact longitudinal through pore canal structure and transverse intercommunicated pore canals.

As can be seen from fig. 3, the carbonized structure of the catalyst of the present invention retained the cellulose peak. Indicating the presence of a cell wall structure.

Detailed description of the preferred embodiments

The technical solution of the present invention is further described in detail below with reference to specific examples and comparative examples, but the examples do not limit the scope of the present invention. It should be noted that, in order to ensure the comparability of the catalyst, the actual loading of palladium is controlled between 0.23-0.25 wt%, and the floating (deviation) is controlled within 2%.

Example 1

The original poplar (produced by Henan Jones, peeled, cut into a cylinder with a diameter (width) of 1 cm and a length of 5 cm) was immersed in an aqueous solution of chloropalladic acid at a concentration of 0.022mol/L at room temperature for 30 days. Taking out, airing in the shade, and reducing for 2h at 180 ℃ by using hydrogen with the flow of 30 ml/min. And finally, heating to 300 ℃ at the temperature of 5 ℃/min under the nitrogen atmosphere, preserving the heat, carrying out surface treatment for 2 hours, cooling, and obtaining the Pd/surface carbonized poplar catalyst with the palladium mass percent of 0.23 wt%, which is recorded as Pd/CP.

Example 2

Compared with the example 1, the difference is only that the wood species are different, specifically:

virgin balsa wood (produced in south America, peeled, cut into cylinders of 1 cm in diameter and 5 cm in length) was immersed in an aqueous solution of chloropalladite acid at a concentration of 0.022mol/L for 30 days at room temperature. Taking out, airing in the shade, and reducing for 2h at 180 ℃ by using hydrogen with the flow of 30 ml/min. And finally, heating to 300 ℃ at the temperature of 5 ℃/min under the nitrogen atmosphere, carrying out surface treatment for 2 hours under the heat preservation condition, and cooling to obtain the Pd/surface carbonized fir catalyst with the mass percent of palladium of 0.25 wt%, which is recorded as Pd/CC.

Example 3

Compared with the embodiment 1, the difference is only that the noble metal source is a Pt source, specifically:

virgin aspen wood (same as example 1) was immersed in an aqueous solution of chloroplatinic acid at a concentration of 0.022mol/L for 30 days at room temperature. Taking out, airing in the shade, and reducing for 2h at 180 ℃ by using hydrogen with the flow of 30 ml/min. And finally, heating to 300 ℃ at the temperature of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, cooling, and obtaining the Pt/surface carbonized poplar catalyst with the platinum mass percent of 0.23 wt%, which is recorded as Pt/CP.

Example 4

Compared with the example 2, the difference is only that the noble metal source is a Pt source, specifically:

virgin balsa wood (same as example 2) was immersed in an aqueous solution of chloroplatinic acid having a concentration of 0.022mol/L at room temperature for 30 days. Taking out, airing in the shade, and reducing for 2h at 180 ℃ by using hydrogen with the flow of 30 ml/min. And finally, heating to 300 ℃ at the temperature of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, cooling, and obtaining the Pt/surface carbonized fir catalyst with the platinum mass percent of 0.25 wt%, which is recorded as Pt/CC.

Example 5

Compared with the example 1, the difference is that the temperature of the surface treatment process is 200 ℃, specifically:

the virgin aspen wood (same as example 1) was immersed in an aqueous solution of chloropalladite acid at a concentration of 0.022mol/L at room temperature for 30 days. Taking out, air drying in shade, reducing with 30ml/min hydrogen at 180 deg.C for 2 hr, cooling. And then, carrying out heat preservation treatment at 200 ℃ for 2 hours in a nitrogen atmosphere to obtain a Pd/low-temperature surface carbonized poplar catalyst with the palladium mass percent of 0.23 wt%, and marking as Pd/LCP.

Example 6

Compared with the embodiment 1, the difference lies in that the reduction process adopts a liquid phase reduction means, specifically:

the virgin aspen wood (same as example 1) was immersed in an aqueous solution of chloropalladite acid at a concentration of 0.022mol/L at room temperature for 30 days. Taking out and airing in the shade, standing and soaking by using a sodium borohydride solution with the concentration of 0.1mol/L at room temperature, and reducing for 2 hours. And finally, heating to 300 ℃ at the temperature of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, cooling, and obtaining the Pd/surface carbonized poplar catalyst with the liquid phase reduction palladium mass percent of 0.23 wt%, which is recorded as Pd/RCP.

Comparative example 1

Compared with the example 1, the difference is that the surface carbonization treatment is not carried out, specifically:

the virgin aspen wood (same as example 1) was immersed in an aqueous solution of chloropalladite acid at a concentration of 0.022mol/L at room temperature for 30 days. Taking out and airing in the shade, reducing for 2h at 180 ℃ by using hydrogen with the flow rate of 30ml/min, cooling, and obtaining a Pd/non-carbonized poplar catalyst with the palladium mass percent of 0.23 wt%, which is recorded as Pd/NP.

Comparative example 2

Compared with the example 2, the difference is that the surface carbonization treatment is not carried out, specifically:

the original Barbadia wood (same as example 2) was immersed in an aqueous solution of chloropalladite at a concentration of 0.022mol/L for 30 days at room temperature. Taking out and airing in the shade, reducing for 2h at 180 ℃ by using hydrogen with the flow rate of 30ml/min, cooling, and obtaining the Pd/non-carbonized fir catalyst with the palladium mass percent of 0.23 wt%, which is recorded as Pd/NP.

Comparative example 3

The difference from example 1 is only that the temperature of the surface carbonization treatment is 500 degrees, specifically:

the virgin aspen wood (same as example 1) was immersed in an aqueous solution of chloropalladite acid at a concentration of 0.022mol/L at room temperature for 30 days. Taking out, air drying in shade, reducing with 30ml/min hydrogen at 180 deg.C for 2 hr, cooling. And then, carrying out heat preservation treatment at 500 ℃ for 2 hours in a nitrogen atmosphere to obtain a Pd/high-temperature carbonized poplar catalyst with the palladium mass percent of 0.23 wt%, and marking as Pd/HCP.

Comparative example 4

Compared with the embodiment 1, the difference is mainly that the impregnation and the reduction are synchronously carried out, and specifically, the method comprises the following steps:

the original poplar (same as example 1) was put into 0.022mol/L chloropalladic acid aqueous solution and reduced by in-situ dipping-reduction method, i.e. sodium borohydride was slowly added dropwise to reduce for 3 hours while dipping. Taking out and airing in a shade, heating to 300 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, cooling, and obtaining the catalyst with the palladium mass percent of 0.24 wt%, which is recorded as Pd/CP (M1).

Comparative example 5

The method adopts a carbonization-impregnation-reduction process to prepare the 0.238 wt% Pd/carbonized poplar catalyst, and specifically comprises the following steps:

and (3) heating the primary poplar (same as the example 1) to 300 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, and cooling to obtain carbonized poplar. Then, the resultant was immersed in an aqueous solution of chloropalladite having a concentration of 0.022mol/L for 30 days. Taking out, air drying in shade, and reducing with 30ml/min hydrogen at 180 deg.C for 2 h. After removal of the catalyst by cooling, a catalyst having a palladium content of 0.238% by weight was obtained, and this was designated as Pd/CP (M2).

Comparative example 6

Compared with example 1, the difference is that the wood primary cell wall array is not reserved, specifically:

virgin aspen wood (same as example 1) was ground by a ball mill, and 40 to 60 mesh powder was immersed in an aqueous solution of chloropalladite acid having a concentration of 0.022mol/L at room temperature for 30 days. Taking out, airing in the shade, and reducing for 2h at 180 ℃ by using hydrogen with the flow of 30 ml/min. And finally, heating to 300 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, cooling, and obtaining the catalyst with the palladium mass percent of 0.243 wt%, which is recorded as Pd/CP (powder).

Comparative example 7

Compared with the embodiment 1, the difference is that bamboo is adopted to replace the wood of the invention, and the concrete steps are as follows:

raw bamboo (produced by Yiyang in Hunan province, peeled, cut into cylinders of 1 cm in diameter and 5 cm in length) was immersed in an aqueous solution of chloropalladite acid at a concentration of 0.022mol/L at room temperature for 30 days. Taking out, airing in the shade, and reducing for 2h at 180 ℃ by using hydrogen with the flow of 30 ml/min. And finally, heating to 300 ℃ at the temperature of 5 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 2 hours, cooling, and obtaining the catalyst with the palladium mass percent of 0.232 wt%, which is marked as the Pd/Bamboo catalyst.

The performance profiles of the toluene catalyzed combustion of all the different examples, comparative examples and literature catalysts are shown in table 1.

Determination of toluene catalytic Combustion Performance

The test conditions of the low-temperature catalytic combustion performance of the catalyst for toluene are as follows: 1g of the catalyst was charged in a tubular reactor and then bubbled with nitrogenCarrying toluene, mixing with air and entering a reactor. The air inlet flow is 30-100 mL/min, and the airspeed is 6000h^-1. The toluene concentration in the reaction gas was 5000ppm, and the other gas components and the composition were as shown in Table 1. Slowly heating, monitoring the composition of the outlet gas on line by a gas chromatograph, and calculating the conversion rate of the toluene. The temperatures at which the toluene conversion was 10% and 90% were respectively denoted as T₁₀And T₉₀The light-off temperature and the complete conversion temperature are indicated, respectively.

TABLE 1 composition of the reaction gases

Composition of the reaction gas	Content (wt.)
		Toluene	5000ppm
O₂	18％
		N₂	81％
CO₂	333ppm
		Others	4667ppm

TABLE 2 comparison of the performance of the toluene catalytic combustion of the different examples, comparative examples and literature catalysts

Note: 1. the cordierite-supported palladium catalyst coated with graphene oxide is sourced from the literature (Chinese Journal of Catalysis 39(2018) 946-954). 2. Cerium oxide (CeO)₂) Carrying palladium catalyst, the reaction condition is that the toluene concentration is 1000pm, and the space velocity is 48000h^-1From the Applied Catalysis B, Environmental 220(2018) 462-470.

From a comparison of the catalysts of the examples in Table 1 with the catalysts of the literature, it can be seen that the light-off temperature of the catalysts of the invention is reduced and the complete conversion temperature is also lower than most of the literature values. Among these, it is noteworthy that the documents Pt/CeO₂The catalyst test conditions were different from the present invention, with lower toluene concentration and higher space velocity, and these two parameters were increased to favor catalytic combustion of toluene, and therefore the catalyst data are incorporated herein by reference.

In the catalyst of the invention, the Pd/CP catalyst has the highest activity and T₁₀And T₉₀Are all the lowest. It can be seen that palladium performs better than platinum in the wood-supported catalyst. Compared with the fir, the performance of the poplar is better from the viewpoint of wood species.

From the comparison of examples 1, 2 with comparative examples 1, 2, it can be seen that the catalyst was not surface carbonized, so that both the light-off temperature and the final conversion temperature were increased, which indicates that the surface carbonization process plays an important role in the catalyst performance. According to the TEM and XRD researches, the process conditions are matched with an innovative surface controllable carbonization means, the original cell array structure can be kept, a grown carbon film and graphene oxide coated noble metal particles are formed on the surface of the cell array structure in situ, and the special structure can unexpectedly improve the catalytic activity. In addition, it is seen from example 5 and comparative example 3 that the carbonization temperature is too low, and the desired effect is not obtained. When the carbonization temperature is too high (such as 500 ℃), collapse of the wood skeleton structure is easily caused, and the whole cell array structure is carbonized, so that the catalytic performance is easily greatly reduced. Therefore, only surface carbonization is performed at the temperature required in the present invention, the cell array structure can be unexpectedly maintained, and the catalytic activity can be unexpectedly improved.

As can be seen from the comparison of example 1 with comparative examples 4 and 5, the preparation process of the catalyst of the present invention needs to strictly follow the sequence of "impregnation-reduction-in situ carbonization". If the order is changed, the structure of the catalyst protected by the present invention cannot be obtained, thus causing the performance of the catalyst to be degraded.

As can be seen from the comparison between example 1 and comparative examples 6 and 7, the original wood powder changes the pore structure thereof, which is not beneficial to the performance of the catalyst, and this also shows that the cell array pore structure of the original wood can unexpectedly improve the catalytic performance of the catalyst in a synergistic manner by matching with the special process of the invention. In addition, although the bamboo with longitudinal pore canals but compact transverse direction is adopted as the carrier, the high-activity catalyst is not easy to obtain. This demonstrates the structural uniqueness of the broadleaf forest primary wood used in the present invention, and the unexpected synergistic effect of the process described in the present invention.

In addition, compared with cerium dioxide, the primary structure of wood as a carrier can also obtain close metal dispersion degree. We determined that the average particle size of the palladium on the catalyst of example 1 and example 2 was 2.21 and 2.35nm, respectively. With Pt/CeO₂The grain diameter of the above 1.5-2.5nm is approximate. The invention takes the renewable resource in the nature, namely wood as the carrier, and obtains the effect similar to other rare earth metal oxides on the particle size distribution.

Example 7

Stability of Pd/CP catalyst (same as example 1) in continuous test of catalytic Combustion in toluene

The Pd/CP catalyst of example 1 was subjected to a long-term stability test at 150 ℃ in accordance with the reaction gas composition of example 5. The result shows that the concentration of the toluene before treatment is 5000ppm, the concentration of the toluene after catalytic treatment is reduced to 50ppm, the conversion rate is maintained at 99 percent, and the concentration reaches the national exhaust emission standard GB16297-1996, namely Integrated emission Standard of atmospheric pollutants. After 168 hours of continuous operation, no decrease in the activity of the catalyst was observed.

Claims

1. The aromatic compound catalytic combustion catalyst is characterized by comprising a wood substrate with a cell wall array structure, wherein a carbon film and graphene oxide-coated noble metal nanoparticles are compounded on the surface of a skeleton of a cell wall in situ.

2. The catalytic combustion catalyst for aromatic compounds according to claim 1, wherein the wood has longitudinal through-channels of 40 to 60 μm and transverse grooves of 5 to 15 μm;

preferably, the wood is broadleaf forest wood, and further preferably is at least one of poplar, fir and zelkova; most preferably poplar.

3. The aromatic compound catalytic combustion catalyst according to claim 1 wherein the noble metal is palladium, platinum or palladium platinum alloy; palladium is preferred.

4. The aromatic compound catalytic combustion catalyst of claim 1 wherein the noble metal loading is from 0.01 wt% to 0.5 wt%.

5. A method for preparing a catalyst for catalytic combustion of aromatic compounds according to any one of claims 1 to 4, comprising the steps of:

6. The method for preparing a catalyst for catalytic combustion of aromatic compounds according to claim 5, wherein the wood is a segment-shaped virgin wood;

preferably, the noble metal source is a water-soluble salt of a noble metal element, preferably at least one of a chloride, a nitrate, an acetate and an acetylacetonate of the noble metal element;

7. The method for preparing a catalyst for catalytic combustion of an aromatic compound according to claim 5, wherein the reduction of the step (2) is liquid phase reduction or gas phase reduction; preferably gas phase reduction;

preferably, the gas phase reduction is: placing the wood loaded with the noble metal source in a reducing atmosphere, and reducing at the temperature of 50-200 ℃, preferably 100-150 ℃;

preferably, the reducing atmosphere is an atmosphere containing hydrogen.

8. The method for preparing the aromatic compound catalytic combustion catalyst as claimed in claim 5, wherein the temperature of the surface in-situ carbonization process is 200-350 ℃, preferably 250-320 ℃;

9. Use of the aromatic compound catalytic combustion catalyst according to any one of claims 1 to 4 or the aromatic compound catalytic combustion catalyst prepared by the preparation method according to any one of claims 5 to 8 as a catalyst for catalyzing oxidative degradation of aromatic compounds;

preferably, the aromatic compound is at least one of benzene, alkyl substituted benzene and halogenated benzene.

10. The use of claim 9, wherein the temperature of the catalytic process is greater than or equal to 75 ℃; preferably 130 to 150 ℃.