CN112762468B

CN112762468B - Method for catalytic combustion of volatile organic compounds

Info

Publication number: CN112762468B
Application number: CN201911001557.6A
Authority: CN
Inventors: 于鹏; 荣峻峰; 谢婧新; 吴耿煌; 宗明生; 林伟国; 纪洪波
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: 2022-04-08
Anticipated expiration: 2039-10-21
Also published as: CN112762468A

Abstract

The invention provides a method for catalytic combustion of volatile organic compounds, comprising: catalyzing a volatile organic compound to perform an oxidation reaction by taking a composite material of carbon-coated nickel aluminum as a catalyst; the nano composite material comprises a core film structure with an outer film and an inner core, wherein the outer film is a graphitized carbon film, the inner core comprises nickel oxide and aluminum oxide, and the nano composite material comprises 59-80% of nickel oxide, 19-40% of aluminum oxide and not more than 1% of carbon by taking the total mass of the nano composite material as a reference. The nano composite material with the nickel oxide and the alumina core 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 catalystsAn oxidizing agent. Among them, noble metal catalysts (such as Pt, Ru, Au, Pd, etc.) have good performance, but are expensive and easy to be poisoned; 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 with high efficiency by using a nanocomposite material in which a graphite carbon film coats nickel oxide and an alumina core as a catalyst, and thus is helpful for solving the problem of purification of VOCs, and has an important meaning 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: catalyzing a volatile organic compound to perform an oxidation reaction by taking a composite material of carbon-coated nickel aluminum as a catalyst; the nano composite material comprises a core film structure with an outer film and an inner core, wherein the outer film is a graphitized carbon film, the inner core comprises nickel oxide and aluminum oxide, and the nano composite material comprises 59-80% of nickel oxide, 19-40% of aluminum oxide and not more than 1% of carbon by taking the total mass of the nano composite material as a reference.

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 nickel oxide content is 69% to 79%, the alumina content is 20% to 30%, and the carbon content is 0.3% to 1%.

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 in terms of mass ratio.

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 5nm and 80 nm.

According to one embodiment of the invention, the inner core further comprises an alkali metal oxide, the content of which in mass% represents not more than 5%, preferably not more than 2.5% of the content of the nanocomposite.

According to the technical scheme, the catalytic combustion of 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 a carbon-coated nickel-aluminum nano composite material as a catalyst, the composite material comprises a nuclear membrane structure with a graphitized carbon membrane and an inner core of nickel oxide and aluminum oxide, has excellent catalytic activity, can efficiently catalyze the oxidation combustion of VOCs at a lower temperature, is beneficial to solving the purification problem of VOCs, reduces the air 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;

FIGS. 2a and 2b are transmission electron microscope images of the nanocomposite material of preparation example 1 at different magnifications, respectively;

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;

FIGS. 5a and 5b are transmission electron microscope images of the nanocomposite material of preparation example 2 at different magnifications, respectively;

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

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 comprising nickel oxide and aluminum oxide nanoparticles. The composite material formed after the graphitized carbon film is coated with nickel oxide and aluminum 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: catalyzing a volatile organic compound to perform an oxidation reaction by taking a composite material of carbon-coated nickel aluminum as a catalyst; the nano composite material comprises a core film structure with an outer film and an inner core, wherein the outer film is a graphitized carbon film, the inner core comprises nickel oxide and aluminum oxide, and the nano composite material comprises 59-80% of nickel oxide, 19-40% of aluminum oxide and not more than 1% of carbon by taking the total mass of the nano composite material as a reference. In some embodiments, the nickel oxide content is 69% to 79%, the alumina content is 20% to 30%, and the carbon content is 0.3% to 1%.

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. Inverse directionSpace velocity is the amount of gas treated per unit volume of catalyst per unit time under the specified conditions, and is given 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 surfaces of nickel oxide and aluminum oxide. The inventor of the invention unexpectedly finds that the core film structure coated with the graphitized carbon film on the outer layer has relatively little carbon content in the film layer, but greatly improves the performance of the whole material, particularly the catalytic performance, specifically, the core film structure not only can generate a certain limited domain effect, effectively avoids the aggregation and growth of core particles, 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 obviously improves the catalytic performance.

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 5nm to 80 nm.

In some embodiments, the core of the nanocomposite material of the invention further comprises an alkali metal oxide, the content of alkali metal oxide in the nanocomposite material being not more than 5% by mass, preferably not more than 2.5% by mass.

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

preparing a nickel-aluminum precursor; carrying out heating treatment on the nickel-aluminum precursor, and carrying out vapor deposition by taking low-carbon alkane as a carbon source gas; and carrying out oxygen treatment on the product after vapor deposition to obtain the carbon-coated nickel-aluminum nano composite material.

According to the preparation method provided by the invention, a nickel-aluminum precursor is prepared, and then the graphite shell is wrapped on the outer surface of the nickel-aluminum core in a vapor deposition mode. The nickel-aluminum precursor prepared by the invention generally has a hydrotalcite crystal structure, and can be prepared by various ways by those skilled in the art, such as coprecipitation and/or hydrothermal crystallization.

Specifically, the nickel aluminum precursor may be prepared by, but is not limited to, the following method.

According to a specific embodiment of the present invention, the nickel aluminum precursor is prepared by a coprecipitation method, and the specific steps may include: simultaneously dripping alkali liquor and aqueous solution containing trivalent aluminum salt and divalent nickel salt into water for precipitation treatment to enable trivalent aluminum salt and divalent nickel salt to generate coprecipitate; the coprecipitate is aged. The feeding amount of the aqueous solution containing the trivalent aluminum salt and the divalent nickel salt can be controlled according to the nickel-aluminum content in the target carbon-coated nickel-aluminum composite material, and the adding amount of the alkali liquor is controlled according to the condition that the trivalent aluminum salt and the divalent nickel salt are completely precipitated. The simultaneous addition of the alkali solution, the trivalent aluminum salt and the divalent nickel salt to the water can improve the dispersion effect of the alkali solution, the aluminum salt and the nickel salt during the initial dropwise addition. In addition, the trivalent aluminum salt and the divalent nickel salt are not particularly limited as long as they are soluble in water, and the alkali in the alkali solution is not particularly limited as long as they are capable of precipitating the trivalent aluminum salt and the divalent nickel salt, for example, the trivalent aluminum salt may include aluminum nitrate and/or aluminum chloride, the divalent nickel salt may include nickel nitrate and/or nickel chloride, and the molar ratio of aluminum in the trivalent aluminum salt to nickel in the divalent nickel salt may be 1: (2-4), the molar concentration of the trivalent aluminum salt can be 0.3-0.6 mol/L; the alkali liquor can be an aqueous solution containing sodium hydroxide and sodium carbonate, the concentration of the sodium hydroxide in the alkali liquor can be 0.2-4 mol/L, and the concentration of the sodium carbonate can be 0.1-2 mol/L; the ratio of the number of moles of sodium hydroxide to the total number of moles of aluminum and nickel in the trivalent aluminum salt and the divalent nickel salt may be (2-4): the ratio of the number of moles of the sodium carbonate to the total number of moles of aluminum and nickel in the trivalent aluminum salt and the divalent nickel salt can be (0.5-2): 1.

according to the invention, the precipitation treatment refers to a process of generating a precipitate from trivalent aluminum salt and divalent nickel salt by using an alkali solution, wherein the alkali solution can be mixed with the trivalent aluminum salt and the divalent nickel salt in various ways such as dripping, pumping or pouring. The aging treatment refers to further reacting the precipitate generated by the precipitation treatment to obtain the nickel-aluminum hydrotalcite crystal. The steps of the precipitation treatment and the aging treatment are not particularly limited, and only a nickel-aluminum precursor is obtained, for example, the conditions of the precipitation treatment may include: the temperature may be room temperature to less than 100 deg.c, preferably 40 deg.c to less than 100 deg.c, to increase the speed of the precipitation process. After the dropwise addition is started, the nickel ions and the aluminum ions are controlled to be precipitated under the condition that the pH value is greater than 7, preferably between 8 and 9, and the specific operation can be as follows: controlling the pH value of the aqueous solution to be between 8 and 9 through the dropping speed of the alkali liquor, accelerating the dropping speed of the alkali liquor if the pH value is lower than 8, and slowing down the dropping speed of the alkali liquor if the pH value is higher than 9; the aging treatment conditions may include: the temperature is 40 ℃ to less than 100 ℃, and the time is 2-72 hours, preferably 6-72 hours, and more preferably 24-48 hours. The nickel-aluminum hydrotalcite crystal obtained by aging treatment can be further washed to be neutral and dried to obtain a nickel-aluminum precursor.

In some embodiments, the temperature raising treatment includes raising the temperature of the nickel-aluminum precursor to 500-900 ℃ in the presence of a protective gas, where the protective gas is nitrogen and/or argon, the flow rate of the protective gas is 10-500 ml/(min-g nickel-aluminum precursor), and the temperature raising speed is 1-5 ℃/min. The protective gas is used as a carrier gas in the temperature rise process of the nickel-aluminum precursor, so that the danger of contact with air is avoided when the reduction and carbon deposition reaction of the nickel-aluminum precursor is carried out, and the graphite shell is prevented from being oxidized when contacting with air at high temperature after being coated with the graphite shell.

In some embodiments, the graphitic carbon shell is formed on the surface of the material by vapor deposition. The temperature of the vapor deposition is 750-900 ℃, preferably 780-850 ℃, and the time is 5-240 min, preferably 60-120 min; the carbon source gas is preferably methane or ethane, and the flow rate of the carbon source gas is 10-500 ml/(min g nickel-aluminum precursor), preferably 30-100 ml/(min g nickel-aluminum precursor), and more preferably 30-60 ml/(min g nickel-aluminum precursor).

According to the invention, after the nickel-aluminum precursor is obtained, the nickel-aluminum precursor subjected to temperature rise treatment is contacted with hydrogen to be subjected to reduction treatment. The reduction treatment has the functions of: on one hand, the nickel-aluminum precursor existing in the form of hydroxide (hydrotalcite) is further dehydrated to generate nickel-aluminum oxide, on the other hand, the generated nickel-aluminum oxide is reduced to generate simple substance nickel as an active center, so that the aluminum oxide and the nickel oxide are combined to form an amorphous structure, and the proportion of carboxyl oxygen in the graphite shell can be reduced. The conditions of the hydrogen reduction treatment may include: the temperature is 500-900 ℃, the time is 120-480 minutes, and the hydrogen flow is 30-50 ml/(min. g nickel-aluminum precursor).

In some embodiments, the present invention further comprises mixing a nickel aluminum precursor with a salt solution of an alkali metal to perform a coprecipitation reaction, and subjecting the obtained precipitate to the aforementioned temperature-increasing heat treatment, wherein the molar ratio of the alkali metal to the nickel is not greater than 0.2. The inventors of the present invention have found that N is catalyzed when this material is used as a catalyst by the aforementioned coprecipitation reaction with a small amount of alkali metal before the temperature raising treatment₂When an acidic oxide such as O reacts, the catalytic activity is further improved.

In some embodiments, the invention further comprises subjecting the vapor deposited product to an oxygen treatment by which the material acquires a specific graphitized carbon film structure.

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 0.5h to 10h, and then the carbon-coated nickel-aluminum 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 vapor-deposited product forms a nanocomposite material in which a graphitized carbon shell covers a nickel-aluminum core, wherein the carbon content is about 3% to 8%. After the product is treated with oxygen, most of the carbon in the material is lost with the oxidation reaction. However, the present inventors have unexpectedly found that the oxygen treated material, while burning off most of the carbon, not only oxidized the nickel and aluminum of the core, but also retained a small portion of the carbon. As mentioned above, XPS and Raman spectrum detection and analysis prove that the carbon is a graphitized carbon film layer coated on the surfaces of nickel oxide and aluminum oxide, and the carbon film layer further has a plurality of excellent properties, so that the nanocomposite has great application potential, especially catalytic activity, in catalytic materials, energy storage materials and electromagnetic materials. 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 used to illustrate the preparation of the carbon-coated nickel-aluminum nanocomposite material of the present invention.

(1) Weighing 11.64g (0.04mol) of nickel nitrate hexahydrate and 7.5g (0.02mol) of aluminum nitrate nonahydrate, adding 60ml of deionized water to prepare a mixed salt solution, preparing a mixed alkali solution by adding 5.40g (0.135mol) of sodium hydroxide, 5.08g (0.048mol) of anhydrous sodium carbonate and 120ml of deionized water, simultaneously dripping the two mixed solutions into a 100ml of deionized water three-neck flask which is pre-filled with constant temperature of 60 ℃, stirring simultaneously, strictly controlling the pH value of the precipitate of the trivalent aluminum salt and the divalent nickel salt in the three-neck flask to be 8.4 (namely controlling the pH value to be 8.3-8.5), continuously stirring at 60 ℃ for 30min after finishing dripping, aging at 80 ℃ for 24h, centrifuging and washing to be neutral, drying at 80 deg.C for 4 hr, mixing with 0.14g (0.001mol) potassium carbonate, adding 150ml deionized water, stirring at 60 deg.C for 10 hr, and drying at 80 deg.C for 10 hr to obtain nickel-aluminum precursor coprecipitated with alkali metal.

(2) Weighing 1.0g of the nickel-aluminum precursor obtained in the step (1), placing the nickel-aluminum precursor into a porcelain boat, then placing the porcelain boat into a tubular furnace in a nitrogen protective atmosphere, carrying out programmed temperature rise of 5 ℃/min at the nitrogen flow of 100mL/min, raising the temperature to 500 ℃, introducing 30mL/min of hydrogen for 180min, and closing the hydrogen; and continuously raising the temperature to 800 ℃, introducing 50mL/min of methane at the temperature, reacting for 60min, closing the methane after the reaction is finished, and naturally cooling in a nitrogen atmosphere to obtain the composite material coated with the carbon shell after vapor deposition.

(3) And (3) placing the material 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 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 oxide after mild oxidation treatment, and fig. 2a and 2b respectively show Transmission Electron Micrographs (TEM) of the nanocomposite material of preparation example 1 at different magnifications, and 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 nanocomposite had a carbon content of 0.79 wt%, a nickel oxide content of 77.14 wt%, an aluminum oxide content of 20.05 wt%, and a potassium oxide content of 2.02 wt%. By means of X-raysPhotoelectron Spectroscopy (XPS) analysis revealed that the elements of the surface layer of the nanocomposite detected carbon, oxygen, nickel, aluminum, and potassium. 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 2.1/1. It can be seen that most of the carbon in this material is graphitic carbon.

Preparation example 2

(1) Weighing 11.64g (0.04mol) of nickel nitrate hexahydrate and 7.5g (0.02mol) of aluminum nitrate nonahydrate, adding 60ml of deionized water to prepare a mixed salt solution, adding 5.40g (0.135mol) of sodium hydroxide and 5.08g (0.048mol) of anhydrous sodium carbonate and 120ml of deionized water to prepare a mixed alkali solution, simultaneously dropwise adding the two mixed solutions into a 100ml of deionized water pre-filled with constant temperature of 60 ℃, stirring simultaneously, strictly controlling the pH value of the precipitate of trivalent aluminum salt and divalent nickel salt in the three-neck flask to be 8 (namely controlling the precipitate to be 7.9-8.1), continuously stirring at 60 ℃ for 30min after dropwise adding, aging at 80 ℃ for 24h, centrifugally washing to be neutral, and drying at 80 ℃ to obtain the nickel-aluminum precursor.

(2) Weighing 1.0g of the nickel-aluminum precursor obtained in the step (1), placing the nickel-aluminum precursor into a porcelain boat, then placing the porcelain boat into a tubular furnace in a nitrogen protective atmosphere, carrying out programmed temperature rise of 5 ℃/min at the nitrogen flow of 100mL/min, raising the temperature to 500 ℃, introducing 30mL/min of hydrogen for 240min, and closing the hydrogen; and continuously raising the temperature to 800 ℃, introducing 50mL/min of methane at the temperature, reacting for 60min, closing the methane after the reaction is finished, and naturally cooling in a nitrogen atmosphere to obtain the composite material coated with the carbon shell after vapor deposition.

(3) And (3) placing the material 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 10 hours, stopping heating, and cooling to room temperature under the atmosphere of the standard gas to obtain black solid, namely the nano composite material.

Material characterization:

fig. 4 is an X-ray diffraction pattern (XRD) of the nanocomposite of preparation example 2, and it can be seen from fig. 4 that nickel in the nanocomposite exists in the form of an oxide after mild oxidation treatment, and fig. 5a and 5b respectively show Transmission Electron Micrographs (TEM) of the nanocomposite of preparation example 2 at different magnifications, and it can be observed that the surface of the material has a carbon layer thin 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 nanocomposite had a carbon content of 0.95 wt%, a nickel oxide content of 77.14 wt%, and an aluminum oxide content of 21.64 wt%. It was found by X-ray photoelectron spectroscopy (XPS) analysis that carbon, oxygen, nickel, and aluminum 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 43/1. 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

Placing the nickel-aluminum precursor obtained in the step (1) in the preparation example 1 into a porcelain boat, then placing the porcelain boat into a tubular furnace in a nitrogen protective atmosphere, carrying out programmed temperature rise of 5 ℃/min at a nitrogen flow of 100mL/min, raising the temperature to 500 ℃, introducing 30mL/min hydrogen for 180min, closing the hydrogen, and naturally cooling in a hydrogen atmosphere to obtain an intermediate product.

And then placing the intermediate product 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 3h, stopping heating, and cooling to room temperature under the atmosphere of the standard gas to obtain the nickel-aluminum composite oxide without carbon film coating.

As can be seen from X-ray fluorescence spectrum analysis (XRF) and elemental analysis, the material contained 76.94 wt% of nickel oxide, 20.87 wt% of aluminum oxide, and 2.19 wt% of potassium oxide.

Comparative preparation example 2

Placing the nickel-aluminum precursor obtained in the step (1) in the preparation example 2 in a porcelain boat, then placing the porcelain boat in a tubular furnace in a nitrogen protection atmosphere, carrying out programmed temperature rise of 5 ℃/min at a nitrogen flow of 100mL/min, heating to 500 ℃, introducing 30mL/min hydrogen for 240min, closing the hydrogen, and naturally cooling in a hydrogen atmosphere to obtain an intermediate product.

As can be seen from X-ray fluorescence spectrum analysis (XRF) and elemental analysis, the nickel oxide content in this material was 77.96 wt%, and the aluminum oxide content was 22.04 wt%.

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 4500h^-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 reaction for catalytic combustion of VOCs was carried out by the method of example 1 except that the material of comparative preparation example 2 was used as a 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-aluminum nanocomposite prepared by the method of the present invention has a better performance of catalytic combustion of VOCs compared with nickel-aluminum oxide not coated with a carbon film, 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: catalyzing a volatile organic compound to perform an oxidation reaction by taking a composite material of carbon-coated nickel aluminum as a catalyst;

the nano composite material comprises a core film structure with an outer film and an inner core, wherein the outer film is a graphitized carbon film, the inner core comprises nickel oxide and aluminum oxide, and the nano composite material comprises 59-80% of nickel oxide, 19-40% of aluminum oxide and less than 1% of carbon by total mass.

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 nickel oxide content is 69% to 79%, the alumina content is 20% to 30%, and the carbon content is 0.3% to 1%.

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

9. 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.

10. The method of claim 1, wherein the nuclear membrane structure has a particle size of 5nm to 80 nm.

11. The method of claim 1, wherein the inner core further comprises an alkali metal oxide, and the content of the alkali metal oxide in the nanocomposite does not exceed 5% by mass.

12. The method of claim 11, wherein the alkali metal oxide content in the inner core does not exceed 2.5% by mass of the nanocomposite.