CN112762469B

CN112762469B - Method for catalytic combustion of volatile organic compounds

Info

Publication number: CN112762469B
Application number: CN201911002419.XA
Authority: CN
Inventors: 于鹏; 荣峻峰; 徐国标; 吴耿煌; 谢婧新; 宗明生; 林伟国
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2019-10-21
Filing date: 2019-10-21
Publication date: 2022-04-12
Anticipated expiration: 2039-10-21
Also published as: CN112762469A

Abstract

The invention provides a method for catalytic combustion of volatile organic compounds, comprising: the carbon-coated nickel oxide nano composite material is used as a catalyst to catalyze a volatile organic compound to carry out an oxidation reaction; the nanocomposite comprises a core film structure having an outer film and an inner core, the outer film being a graphitized carbon film, the inner core comprising nickel oxide nanoparticles, wherein the carbon content is not more than 5 wt% of the nanocomposite. The nano composite material of nickel oxide coated by the graphite carbon film is used as the catalyst, so that the oxidation and combustion of the volatile organic compound can be efficiently catalyzed at a lower temperature, the purification problem of the volatile organic compound is favorably solved, the nano composite material has an important significance for reducing the air pollution, and has a wide application prospect.

Description

Method for catalytic combustion of volatile organic compounds

Technical Field

The invention relates to the technical field of catalysis, in particular to a method for catalytic combustion of volatile organic compounds.

Background

Volatile Organic Compounds (VOCs) are Organic Compounds having a saturated vapor pressure at room temperature of greater than 70Pa and a boiling point at atmospheric pressure of 260 ℃ or lower. The VOCs are various in types, mainly comprise alkanes, aromatics, esters, aldehydes, halogenated hydrocarbons and the like, most of the VOCs have pungent odor and can cause poisoning and carcinogenesis, and the VOCs are important sources for forming photochemical smog and atmospheric particulate matters PM 2.5. As a large country of manufacturing industry, the discharge amount of VOCs in China reaches the first world, and VOCs discharged in industrial production is high in discharge concentration, long in duration and various in pollutants, so that the VOCs are harmful to human health and seriously damage the ecological environment. In recent years, the systematic prevention and treatment of VOCs as a pollutant in China, the development of efficient VOCs purification technology and the control of the discharge amount of VOCs have become important subjects in the field of environmental protection.

The purification methods of VOCs mainly fall into two categories: the first is physical absorption, adsorption, which is commonly used for recovering high concentration (>5000mg/m³) Of VOCs, but the process is carried out at low concentrations of (C)<1000mg/m³) The purification effect of VOCs is not ideal, the adsorption efficiency is low, and secondary wastewater or solid waste can be generated by adsorption, absorption and elution. The second type is a chemical reaction method, which converts VOCs into non-toxic chemicals by introducing an oxidant into the VOCs. The method is mainly used for treating medium-concentration or low-concentration VOCs.

The chemical reaction method is widely applied to combustion technology, and the combustion technology is particularly divided into direct flame combustion and catalytic combustion. The direct flame combustion is to take VOCs as fuel to be directly combusted, the combustion needs to be carried out at the high temperature of about 600-900 ℃, the energy consumption is high, and black smoke and peculiar smell can be generated due to incomplete combustion. Catalytic combustion is a typical gas-solid catalytic reaction, and the essence is that VOCs and O adsorbed on the surface of the catalyst₂Catalytic reaction to produce harmless CO₂And H₂The O, reaction is usually carried out at the temperature of 300-500 ℃, so that the energy consumption is low, secondary pollution is not generated, and the method is an energy-saving, effective, economic and environment-friendly technology.

The catalyst is the core of catalytic combustion technology. The catalysts for catalyzing and burning VOCs reported in the current research mainly comprise noble metal catalysts and non-noble metal oxide catalysts. Among them, noble metal catalysts (such as Pt, Ru, Au, Pd, etc.) have good performance, but are expensiveAnd is susceptible to poisoning; non-noble metal oxide catalysts (e.g. Co)₂O₃、MnO₂、CeO₂、CuO、TiO₂Perovskite, etc.) are low in cost and not easy to poison, but the catalytic activity is low.

Therefore, the catalyst with low development cost and high activity is a problem to be solved in the field of catalytic combustion of VOCs.

It is noted that the information disclosed in the foregoing background section is only for enhancement of background understanding of the invention and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

One of the main objects of the present invention is to overcome at least one of the above drawbacks of the prior art, and to provide a method for catalytic combustion of volatile organic compounds, which can catalyze the oxidation combustion of VOCs at a low temperature and a high efficiency by using a nanocomposite material in which a graphite carbon film is coated with nickel oxide as a catalyst, and thus is helpful for solving the problem of purification of VOCs, and has a great significance for reducing atmospheric pollution.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for catalytic combustion of volatile organic compounds, comprising: the carbon-coated nickel oxide nano composite material is used as a catalyst to catalyze a volatile organic compound to carry out an oxidation reaction; wherein the nano composite material comprises a core film structure with an outer film and an inner core, the outer film is a graphitized carbon film, the inner core comprises nickel oxide nano particles, and the carbon content is not more than 5 wt% of the nano composite material.

According to one embodiment of the present invention, the oxidation reaction comprises catalytic combustion of a mixed gas containing volatile organic compounds and a standard gas containing oxygen in contact with a catalyst.

According to one embodiment of the present invention, the volume percentage of the volatile organic compound in the mixed gas is 0.01% to 2%, and the volume percentage of the oxygen is 5% to 20%.

According to one embodiment of the present invention, the volatile organic compound is one or more selected from hydrocarbon compounds having 1 to 4 carbon atoms.

According to one embodiment of the invention, the space velocity of the oxidation reaction is 1000h^-1～5000h^-1。

According to one embodiment of the invention, the temperature of the oxidation reaction is between 300 ℃ and 450 ℃.

According to one embodiment of the invention, the carbon content is not more than 1 wt% of the nanocomposite.

According to one embodiment of the present invention, the ratio of the carbon element in the nanocomposite material as determined by X-ray photoelectron spectroscopy to the carbon element content as determined by elemental analysis is not less than 10.

According to one embodiment of the invention, the Raman spectrum of the nanocomposite material is at 1580cm^-1Intensity of nearby G peak at 1320cm^-1The ratio of the intensities of the nearby D peaks is greater than 2.

According to one embodiment of the invention, the particle size of the nuclear membrane structure is between 1nm and 100 nm.

According to the technical scheme, the method for catalytically combusting the volatile organic compounds has the advantages and positive effects that:

the method for catalytic combustion of volatile organic compounds provided by the invention adopts the carbon-coated nickel oxide nano composite material as the catalyst, the composite material comprises a nuclear membrane structure with a graphitized carbon membrane and a nickel oxide inner core, has excellent catalytic activity, can catalyze the oxidation combustion of VOCs at a low temperature with high efficiency, is beneficial to solving the purification problem of VOCs, reduces the atmospheric pollution, and has good industrial application prospect.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is an X-ray diffraction pattern of the nanocomposite of preparation example 1;

FIG. 2 is a transmission electron microscope photograph of the nanocomposite material of preparation example 1;

FIG. 3 is a Raman spectrum of the nanocomposite of preparation example 1;

FIG. 4 is an X-ray diffraction pattern of the nanocomposite of preparation example 2;

FIG. 5 is a transmission electron microscope photograph of the nanocomposite material of preparation example 2;

FIG. 6 is a Raman spectrum of the nanocomposite of preparation example 2;

FIG. 7 is an X-ray diffraction spectrum of the material obtained in comparative preparation example 1;

FIGS. 8a and 8b show transmission electron micrographs of the material obtained in comparative preparation example 1 at different magnifications, respectively.

Detailed Description

The following presents various embodiments or examples in order to enable those skilled in the art to practice the invention with reference to the description herein. These are, of course, merely examples and are not intended to limit the invention. The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to yield one or more new ranges of values, which ranges of values should be considered as specifically disclosed herein.

Any terms not directly defined herein should be understood to have meanings associated with them as commonly understood in the art of the present invention. The following terms as used throughout this specification should be understood to have the following meanings unless otherwise indicated.

The term "nuclear membrane structure" in the present invention means a nuclear membrane structure having an outer membrane which is a graphitized carbon membrane and an inner core containing nickel oxide nanoparticles. The composite material formed after the graphitized carbon film is coated with the nickel oxide nano particles is spherical or quasi-spherical.

The term "graphitized carbon film" refers to a thin film structure composed mainly of graphitized carbon.

The term "carbon element content determined by X-ray photoelectron spectroscopy" refers to the relative content of carbon elements on the surface of a material measured by quantitative elemental analysis using an X-ray photoelectron spectrometer as an analysis tool.

The term "carbon content determined in elemental analysis" refers to the relative content of total carbon elements of a material measured by elemental quantitative analysis using an elemental analyzer as an analysis tool.

The invention provides a method for catalytic combustion of volatile organic compounds, comprising: the carbon-coated nickel oxide nano composite material is used as a catalyst to catalyze a volatile organic compound to carry out an oxidation reaction; the nanocomposite comprises a core film structure having an outer film and an inner core, the outer film being a graphitized carbon film, the inner core comprising nickel oxide nanoparticles, wherein the carbon content is not more than 5 wt% of the nanocomposite. In some embodiments, the carbon content is no greater than 1 wt% of the nanocomposite.

In some embodiments, the volatile organic compound is selected from one or more of hydrocarbon compounds with 1-4 carbon atoms. For example, n-butane, n-propane, ethane, methane are possible.

In some embodiments, the oxidation reaction comprises catalytic combustion of a mixed gas containing volatile organic compounds and a standard gas in contact with a catalyst, wherein the standard gas contains oxygen, and the balance gas may be an inert gas such as nitrogen or argon, and the volume percentage of the volatile organic compounds is 0.01% to 2%, and the volume percentage of the oxygen is 5% to 20%.

In some embodiments, the space velocity of the oxidation reaction is 1000h^-1～5000h^-1. The space velocity of the reaction is the amount of gas treated per unit volume of catalyst per unit time under the specified conditions, and is expressed in m³/(m³Catalyst h) can be simplified to h^-1. The high reaction space velocity allowed by the invention shows that the catalyst has high activity and large device processing capacity when the reaction is applied.

In some embodiments, the temperature of the oxidation reaction is from 300 ℃ to 450 ℃, preferably from 350 ℃ to 400 ℃. This indicates that the catalytic oxidation reaction can be well performed at low temperature by using the catalyst of the present invention.

According to the present invention, as described above, industrial waste gas often contains Volatile Organic Compounds (VOCs), which have been one of the main causes of photochemical smog, and are used together with nitrogen oxides, inhalable particles, etc. as important pollutants for controlling the quality of the atmosphere, and in addition, they have high toxicity, carcinogenic hazards, etc., so that catalytic oxidation materials with excellent performance are urgently required for treatment.

The invention adopts the novel catalyst to catalyze and combust VOCs, and has excellent catalytic activity and stability at low temperature. The catalyst is a nuclear membrane structure comprising an outer membrane layer and an inner nuclear layer, wherein the outer membrane layer mainly comprises a graphitized carbon membrane, and the graphitized carbon membrane is a thin membrane structure mainly comprising graphitized carbon and is coated on the surface of nickel oxide nano particles. The inventor of the invention unexpectedly finds that the core membrane structure coated with the graphitized carbon membrane on the outer layer has relatively little carbon content in the membrane layer, but greatly improves the performance of the whole material, particularly the catalytic performance, specifically, the core membrane structure not only can generate a certain confinement effect, effectively avoids the aggregation and growth of nickel oxide nanoparticles in the core, and enables the catalytic activity of the composite material to be stable, but also can synergistically increase the catalytic activity of the whole composite material, and has obvious improvement compared with the catalytic activity of pure nickel oxide.

In some embodiments, the nanocomposite material of the present invention has a ratio of the content of carbon element determined by X-ray photoelectron spectroscopy to the content of carbon element determined by elemental analysis of not less than 10 in terms of mass ratio. As mentioned above, the carbon content determined by X-ray photoelectron spectroscopy refers to the relative carbon content on the surface of the material measured by quantitative element analysis using an X-ray photoelectron spectrometer as an analysis tool. The carbon element content determined in the element analysis refers to the relative content of the total carbon elements of the material, which is measured by carrying out element quantitative analysis by taking an element analyzer as an analysis tool. When the ratio of the carbon element determined by X-ray photoelectron spectroscopy to the carbon element determined by element analysis is larger, most of carbon in the whole nano composite material is concentrated on the surface of the material to form a carbon film layer, and further the nuclear film structure is formed.

In some embodiments, the raman spectrum of the nanocomposite material of the present invention is at 1580cm^-1Intensity of nearby G peak at 1320cm^-1The ratio of the intensities of the nearby D peaks is greater than 2. As will be understood by those skilled in the art, the peak D and the peak G are both Raman characteristic peaks of a crystal of C atoms, the peak D represents a defect in a lattice of carbon atoms, and the peak G represents a sp of C atoms²Hybrid in-plane stretching vibration. It is understood that a greater ratio of the intensity of the G peak to the intensity of the D peak indicates that more graphitic carbon is present in the nanocomposite than amorphous carbon. That is, the carbon element in the nanocomposite material of the present invention exists mainly in the form of graphitic carbon. The graphite carbon has better oxidation resistance, and can increase the catalytic activity with the nickel oxide nano-particles of the kernel in a synergistic manner, thereby improving the performance of the whole composite material.

In some embodiments, the aforementioned nuclear membrane structure generally has a particle size of 1nm to 100nm, preferably 2nm to 40 nm.

The preparation method of the carbon-coated nickel oxide nanocomposite comprises the following steps:

putting a nickel-containing compound and polybasic organic carboxylic acid into a solvent to be mixed to form a homogeneous solution;

removing the solvent in the homogeneous solution to obtain a precursor;

pyrolyzing the precursor in inert atmosphere or reducing atmosphere;

and carrying out oxygen treatment on the product after pyrolysis to obtain the nano composite material.

Specifically, the precursor is a water-soluble mixture, which refers to a nickel-containing water-soluble mixture obtained by dissolving a nickel-containing compound and a polybasic organic carboxylic acid in a solvent such as water and ethanol to form a homogeneous solution, and then directly evaporating and removing the solvent. The foregoing temperature and process of evaporating the solvent may be by any available prior art, for example, spray drying at 80 ℃ to 120 ℃ or drying in an oven.

In addition, other organic compounds than the two mentioned above, which can be any organic compound that can supplement the carbon source required in the product without containing other doping atoms, can also be added to form a homogeneous solution. Organic compounds having no volatility such as organic polyols, lactic acid and the like are preferable.

In some embodiments, the mass ratio of the nickel-containing compound, the poly-organic carboxylic acid, and the other organic compound is 1:0.1 to 10:0 to 10, preferably 1:0.5 to 5:0 to 5, more preferably 1:0.8 to 3:0 to 3; the nickel-containing compound is one or more of organic acid salt of nickel, nickel carbonate, basic nickel carbonate, nickel hydroxide and nickel oxide; preferably, the organic acid salt is an organic carboxylate salt of nickel free of other heteroatoms. The polybasic organic carboxylic acid is selected from one or more of citric acid, maleic acid, trimesic acid, terephthalic acid, gluconic acid and malic acid.

In some embodiments, the pyrolyzing comprises: heating the precursor to a constant temperature section in an inert atmosphere or a reducing atmosphere, and keeping the constant temperature in the constant temperature section;

wherein the heating rate is 0.5-30 ℃/min, preferably 1-10 ℃/min; the temperature of the constant temperature section is 400-800 ℃, and preferably 500-800 ℃; the constant temperature time is 20min to 600min, preferably 60min to 480 min; the inert atmosphere is nitrogen or argon, and the reducing atmosphere is a mixed gas of an inert gas and hydrogen, for example, a small amount of hydrogen is doped in the inert atmosphere.

In some embodiments, the oxygen treatment comprises introducing standard gas into the pyrolyzed product and heating, wherein the standard gas comprises oxygen and balance gas, and the volume concentration of the oxygen is 10% to 40%, optionally 10% to 30%. The balance gas may be an inert gas such as nitrogen or argon, but the present invention is not limited thereto.

In some embodiments, the temperature of the oxygen treatment is from 200 ℃ to 500 ℃, preferably from 300 ℃ to 400 ℃; the time of the oxygen treatment is 0.5 to 10 hours, preferably 1 to 10 hours. Then the carbon-coated nickel oxide nano composite material can be obtained.

As known to those skilled in the art, carbon is oxidized to generate gas after contacting with oxygen at high temperature, and it can be understood that the product after high temperature pyrolysis forms a nanocomposite material in which a graphite carbon shell coats an inner core nickel, wherein the carbon content is about 15% to 60%. After the pyrolysis product is treated with oxygen, most of the carbon in the material is lost along with the oxidation reaction. However, the inventors of the present invention have unexpectedly found that the oxygen treated material burns off most of the carbon while oxidizing not only the nickel of the core but also a small portion of the carbon remains. As mentioned above, XPS and Raman spectrum detection analysis prove that the carbon is a graphitized carbon film layer coated on the surface of the nickel oxide, and the carbon film layer further enables the nanocomposite material to have a plurality of excellent properties, especially catalytic activity. The nano composite material is used for catalytic combustion of volatile organic compounds, shows excellent catalytic activity and stability, can catalyze the oxidation combustion of VOCs at a low temperature with high efficiency, is beneficial to solving the purification problem of VOCs, and has important significance for reducing air pollution.

The invention will be further illustrated by the following examples, but is not to be construed as being limited thereto. Unless otherwise specified, all reagents used in the invention are analytically pure.

The invention detects elements on the surface of the material by an X-ray photoelectron spectrum analyzer (XPS). The adopted X-ray photoelectron spectrum analyzer is an ESCALB 220i-XL type ray photoelectron spectrum analyzer which is manufactured by VG scientific company and is provided with Avantage V5.926 software, and the X-ray photoelectron spectrum analysis test conditions are as follows: the excitation source is monochromatized A1K alpha X-ray, the power is 330W, and the basic vacuum is 3X 10 during analysis and test^-9mbar。

The analysis of carbon (C) element is carried out on an Elementar Micro Cube element analyzer which is mainly used for analyzing four elements of carbon (C), hydrogen (H), oxygen (O) and nitrogen (N), and the specific operation method and conditions are as follows: weighing 1-2 mg of a sample in a tin cup, placing the sample in an automatic sample feeding disc, feeding the sample into a combustion tube through a ball valve for combustion, wherein the combustion temperature is 1000 ℃ (the atmosphere interference during sample feeding is removed, helium is adopted for blowing), and then reducing the combusted gas by using reduced copper to form nitrogen, carbon dioxide and water. The mixed gas is separated by three desorption columns and sequentially enters a TCD detector for detection. The oxygen element is analyzed by converting oxygen in a sample into CO under the action of a carbon catalyst by utilizing pyrolysis, and then detecting the CO by adopting TCD. Since the composite material of the present invention contains only carbon and a metal oxide, the total content of the metal oxide can be determined from the content of the carbon element.

The ratio between the different metal oxides was measured by an X-ray fluorescence spectrometer (XRF), and the content of the different metal oxides in the composite material was calculated from the known content of carbon element. The X-ray fluorescence spectrum analyzer (XRF) adopted by the invention is a Rigaku 3013X-ray fluorescence spectrometer, and the X-ray fluorescence spectrum analysis and test conditions are as follows: the scanning time was 100s and the atmosphere was air.

The Raman detection adopts a LabRAM HR UV-NIR laser confocal Raman spectrometer produced by HORIBA company of Japan, and the laser wavelength is 325 nm.

The high-resolution transmission electron microscope (HRTEM) adopted by the invention is JEM-2100(HRTEM) (Nippon electronics Co., Ltd.), and the test conditions of the high-resolution transmission electron microscope are as follows: the acceleration voltage was 200 kV.

The model of the XRD diffractometer adopted by the invention is an XRD-6000X-ray powder diffractometer (Shimadzu Japan), and the XRD test conditions are as follows: the Cu target was irradiated with K α rays (wavelength λ is 0.154nm), tube voltage was 40kV, tube current was 200mA, and scanning speed was 10 ° (2 θ)/min.

Preparation example 1

This preparation example is intended to illustrate the preparation of the carbon-coated nickel oxide nanocomposite material of the present invention.

(1) Weighing 10g of nickel carbonate and 10g of citric acid, adding the nickel carbonate and the citric acid into a beaker containing 100mL of deionized water, stirring the mixture at 70 ℃ to obtain a homogeneous solution, and continuously heating and evaporating the homogeneous solution to dryness to obtain a solid precursor.

(2) And (2) placing the solid precursor obtained in the step (1) in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing nitrogen with the flow of 100mL/min, heating to 600 ℃ at the speed of 4 ℃/min, keeping the temperature for 2h, stopping heating, and cooling to room temperature under the nitrogen atmosphere to obtain a black solid.

(3) And (3) placing the black solid obtained in the step (2) in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing standard gas (15% of oxygen and balance gas) with the flow rate of 100mL/min, heating to 350 ℃ at the speed of 2 ℃/min, keeping the temperature for 8 hours, stopping heating, and cooling to room temperature under the atmosphere of the standard gas to obtain the black solid, namely the nano composite material.

Material characterization:

FIG. 1 is an X-ray diffraction pattern (XRD) of the nanocomposite material of preparation example 1, and it can be seen from FIG. 1 that nickel in the nanocomposite material exists in the form of an oxide after mild oxidation treatment. FIG. 2 is a Transmission Electron Microscope (TEM) image of the nanocomposite material of preparation example 1, in which it can be observed that the surface of the material has a carbon layer film, and the particle size is about 5 to 20 nm.

As can be seen from X-ray fluorescence spectrum analysis (XRF) and elemental analysis, the carbon content in the nanocomposite was 0.64 wt% and the nickel oxide content was 99.36 wt%. It was found by X-ray photoelectron spectroscopy (XPS) analysis that carbon, oxygen, and nickel were detected as surface layer elements of the nanocomposite. Wherein the ratio of the carbon element content of the surface layer to the total carbon element content is 32.7/1. It can be seen that the carbon in the nanocomposite is mainly present on the surface of the core film structure. FIG. 3 shows a Raman spectrum of the nanocomposite, wherein the G peak (1580 cm)^-1) Intensity of (3) and intensity of D peak (1320 cm)^-1) The ratio of (A) to (B) is 2.2/1. It can be seen that most of the carbon in this material is graphitic carbon.

Preparation example 2

(1) Weighing 10g of nickel acetate and 10g of citric acid, adding the nickel acetate and the citric acid into a beaker containing 100mL of deionized water, stirring the mixture at 70 ℃ to obtain a homogeneous solution, and continuously heating and evaporating the homogeneous solution to dryness to obtain a solid precursor.

(2) And (2) placing the solid precursor obtained in the step (1) in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing nitrogen with the flow of 100mL/min, heating to 650 ℃ at the speed of 2 ℃/min, keeping the temperature for 2h, stopping heating, and cooling to room temperature under the nitrogen atmosphere to obtain a black solid.

(3) And (3) placing the black solid obtained in the step (2) in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing standard gas (15% of oxygen and balance gas) with the flow rate of 100mL/min, heating to 330 ℃ at the speed of 2 ℃/min, keeping the temperature for 8 hours, stopping heating, and cooling to room temperature under the atmosphere of the standard gas to obtain the black solid, namely the nano composite material.

Material characterization:

fig. 4 shows an X-ray diffraction pattern of the nanocomposite material of preparation example 2, and it can be seen from fig. 4 that nickel in the nanocomposite material exists in the form of oxide after the mild oxidation treatment. FIG. 5 shows a transmission electron microscope image of the nanocomposite material of preparation example 2, in which it can be observed that the material surface has a carbon layer film with a particle size of about 5 to 20 nm.

As can be seen from X-ray fluorescence spectrum analysis (XRF) and elemental analysis, the carbon content in the nanocomposite was 0.91 wt% and the nickel oxide content was 99.09 wt%. It was found by X-ray photoelectron spectroscopy (XPS) analysis that carbon, oxygen, and nickel were detected as surface layer elements of the nanocomposite. Wherein the ratio of the carbon element content of the surface layer to the total carbon element content is 22.4/1. It can be seen that the carbon in the nanocomposite is mainly present on the surface of the core film structure. FIG. 6 shows a Raman spectrum of the nanocomposite, wherein the G peak (1580 cm)^-1) Intensity of (3) and intensity of D peak (1320 cm)^-1) The ratio of (A) to (B) is 2.4/1. It can be seen that most of the carbon in this material is graphitic carbon.

Comparative preparation example 1

And (3) placing 10g of nickel acetate solid in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing air with the flow rate of 150mL/min, heating to 500 ℃ at the speed of 2 ℃/min, keeping the temperature for 2h, stopping heating, and cooling to room temperature in the air atmosphere to obtain a sample material.

Fig. 7 is an X-ray diffraction pattern of the material obtained in comparative example 1, and as can be seen from fig. 7, the XRD pattern of the material shows characteristic peaks of nickel oxide, indicating that nickel is mainly present in the form of nickel oxide. Fig. 8a and 8b show transmission electron microscope images of the material obtained in comparative example 1 at different magnifications, respectively, and it can be seen that nickel oxide is agglomerated together in a large amount, indicating that nickel oxide nanoparticles without carbon film coating are very easily agglomerated. XRF and elemental analysis showed that the material of comparative example 1 had 0.12 wt% carbon and 99.88 wt% nickel oxide.

Example 1

This example is intended to illustrate the catalytic combustion of VOCs using the nanocomposite of preparation 1 as a catalyst.

0.2g of catalyst is placed in a continuous flow fixed bed reactor, the reaction gas comprises 0.5 percent of n-butane and 8 percent of oxygen by volume percentage, nitrogen is balance gas, the flow rate of the reaction gas is 15ml/min, and the space velocity is 1800h^-1The activity evaluation temperature range is 300-500 ℃, and the conversion rate of VOCs in catalytic combustion of the catalyst at different temperatures is shown in Table 1.

Example 2

The reaction for catalytic combustion of VOCs was carried out by the method of example 1 except that the nanocomposite material of preparation example 2 was used as a catalyst, and the results are shown in table 1.

Comparative example 1

The reaction for catalytic combustion of VOCs was carried out by the method of example 1 except that the material of comparative preparation example 1 was used as a catalyst, and the results are shown in table 1.

Comparative example 2

The catalytic combustion reaction of VOCs was carried out using the method of example 1 except that commercially available nickel oxide (NiO) (analytical grade: 20160803, manufacturer: national pharmaceutical group chemical Co., Ltd.) was used as the catalyst, and the results are shown in Table 1.

TABLE 1

As can be seen from the above table 1, in the catalytic combustion evaluation experiment performed by using n-butane as a model molecule, the carbon-coated nickel oxide nanocomposite prepared by the method of the present invention has a better performance of catalytic combustion of VOCs compared with uncoated pure nickel oxide, and can catalyze n-butane to completely combust to generate carbon dioxide and water at a relatively low temperature with high efficiency, thereby greatly reducing the reaction temperature, reducing the energy consumption, and having good industrial application prospects.

It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.

Claims

1. A method of catalytically combusting volatile organic compounds, comprising: the carbon-coated nickel oxide nano composite material is used as a catalyst to catalyze a volatile organic compound to carry out an oxidation reaction;

wherein the nanocomposite comprises a core film structure having an outer film and an inner core, the outer film being a graphitized carbon film, the inner core comprising nickel oxide nanoparticles, wherein the carbon content is less than 1 wt% of the nanocomposite.

2. The method according to claim 1, wherein the oxidation reaction comprises catalytic combustion by contacting a mixed gas containing the volatile organic compound and a standard gas containing oxygen with a catalyst.

3. The method of claim 2, wherein the volume percentage of the volatile organic compound in the mixed gas is 0.01-2%, and the volume percentage of the oxygen is 5-20%.

4. The method according to claim 1, wherein the volatile organic compound is one or more selected from hydrocarbon compounds having 1 to 4 carbon atoms.

5. The process according to claim 1, wherein the space velocity of the oxidation reaction is 1000h^-1～5000h^-1。

6. The process according to claim 1, wherein the temperature of the oxidation reaction is 300 ℃ to 450 ℃.

7. The method of claim 1, wherein the nanocomposite material has a carbon content as determined by X-ray photoelectron spectroscopy in a ratio of not less than 10 to a carbon content as determined by elemental analysis.

8. The method of claim 1, wherein the nanocomposite material has a Raman spectrum at 1580cm^-1Intensity of nearby G peak at 1320cm^-1The ratio of the intensities of the nearby D peaks is greater than 2.

9. The method of claim 1, wherein the nuclear membrane structure has a particle size of 1nm to 100 nm.