阅读说明：本技术 一种改性纳米碳材料及其制备方法和应用 (Modified nano carbon material and preparation method and application thereof ) 是由 史春风 康振辉 王肖 孙悦 刘阳 黄慧 赵娟 周赟杰 于 2020-05-29 设计创作，主要内容包括：本发明涉及一种改性纳米碳材料及其制备方法和应用,该方法包括：在含有模板剂的分子筛的焙烧过程中,将纳米碳材料和所述分子筛在300-600℃下一同焙烧1-12小时,焙烧过程中,气氛中氧含量为8-20体积％。本发明的方法制备得到的改性纳米碳材料具有更优的催化活性。(The invention relates to a modified nano carbon material and a preparation method and application thereof, wherein the method comprises the following steps: in the roasting process of the molecular sieve containing the template agent, the nano carbon material and the molecular sieve are roasted for 1 to 12 hours at the temperature of 300-600 ℃, and the oxygen content in the atmosphere is 8 to 20 volume percent in the roasting process. The modified nano carbon material prepared by the method has better catalytic activity.)

1. A method of preparing a modified nanocarbon material, the method comprising: in the roasting process of the molecular sieve containing the template agent, the nano carbon material and the molecular sieve are roasted for 1 to 12 hours at the temperature of 300-600 ℃, and the oxygen content in the atmosphere is 8 to 20 volume percent in the roasting process.

2. The method of claim 1, wherein the method comprises: and placing the nano carbon material and the molecular sieve in the same muffle furnace, and roasting at the temperature of 300-500 ℃ for 3-12 hours.

3. The method of claim 1, wherein the nanocarbon material is placed separately from the molecular sieve and the nanocarbon material is located above the molecular sieve.

4. The method of any of claims 1-3, wherein the method further comprises: nitrogen and/or oxygen are introduced into the muffle to maintain the oxygen content in the muffle at 9-17 vol%, preferably 10-15 vol%.

5. The method of claim 1, wherein the weight ratio of the amount of the nanocarbon material to the amount of the molecular sieve is 1: (0.1-500), preferably 1: (1-100).

6. The method of claim 1, wherein the molecular sieve is calcined in an atmosphere comprising a quaternary ammonium base, ammonia, an alcohol, a fatty amine, or an alcohol amine, or two or three thereof.

7. The method of claim 1, wherein the template is present in the molecular sieve in an amount of from 1 to 20 wt.%, based on the dry weight of the molecular sieve.

8. The method of claim 1, wherein the templating agent is a quaternary ammonium base compound, a fatty amine compound, or an alcohol amine compound, or a combination of two or three thereof;

preferably, the quaternary ammonium base compound is tetraethylammonium hydroxide, tetrabutylammonium hydroxide or tetrapropylammonium hydroxide, or two or three thereof;

the aliphatic amine compound is butanediamine, ethylamine, hexanediamine or n-butylamine, or two or three of the butanediamine, the ethylamine, the hexanediamine or the n-butylamine;

the alcohol amine compound is diethanolamine, monoethanolamine or triethanolamine, or a combination of two or three of the two or three.

9. The method of claim 1, wherein the carbon nanomaterial is selected from carbon nanotubes, nanographite, graphene, nanodiamond, fullerenes or activated carbon, or a combination of two or three thereof.

10. The method of claim 1, wherein the molecular sieve is selected from a titanium silicalite, a silicoaluminophosphate, an all-silica molecular sieve, or a vanadosilicate molecular sieve, or a combination of two or three thereof;

preferably, the molecular sieve is selected from TS-1, TS-2, Ti-MCM-22, Ti-MOR, Ti-beta or Ti-ZSM-48, or a combination of two or three thereof.

11. A modified nanocarbon material prepared according to the method of any one of claims 1 to 10.

12. The modified carbon nanomaterial according to claim 11, wherein the modified nanocarbon material has a total nitrogen content of 0.01 to 10% by weight, preferably 0.5 to 5% by weight;

the ratio of the weight content of nitrogen elements representing ammonia nitrogen species to the weight content of the total nitrogen elements on the surface of the modified nanocarbon material is 20 to 90%, preferably 40 to 80%.

13. Use of the modified nanocarbon material of claim 11 in the dehydrogenation of alkanes to olefins.

Technical Field

The invention relates to a modified nano carbon material and a preparation method and application thereof.

Background

In the sixty-seven decades of the last century, the development of the modern oil refining chemical industry is greatly promoted by the appearance of high-silicon molecular sieves. It is known that the synthesis of high silicon molecular sieves with excellent performance generally requires hydrothermal crystallization in the presence of nitrogen-containing organic templates. Therefore, the synthesized high-silicon molecular sieves in the presence of the template all contain a certain amount of organic template before roasting. The current general treatment method is roasting, namely, carrying out high-temperature heat treatment on the high-silicon molecular sieve containing the organic template agent obtained by hydrothermal synthesis at a certain temperature. And the organic template agent is removed or decomposed from the particles of the high-silicon molecular sieve, so that the microporous pore channels of the high-silicon molecular sieve are effectively released, and the high-silicon molecular sieve is used as a catalyst to effectively diffuse reactants and products in the microporous pore channels in the molecular sieve, so that smooth reaction is ensured. However, in the roasting process of the high silicon molecular sieve, ammonia nitrogen gas is generated due to the desorption or decomposition of the nitrogen-containing organic template, at present, the catalyst is generally directly discharged or discharged after being subjected to harmless treatment such as nitration, and the application of the ammonia nitrogen gas generated due to the desorption or decomposition of the nitrogen-containing organic template in the roasting process of the high silicon molecular sieve is rarely reported.

Disclosure of Invention

The invention aims to provide a modified nano carbon material and a preparation method and application thereof.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a modified nanocarbon material, the method comprising: in the roasting process of the molecular sieve containing the template agent, the nano carbon material and the molecular sieve are roasted for 1 to 12 hours at the temperature of 300-600 ℃, and the oxygen content in the atmosphere is 8 to 20 volume percent in the roasting process.

Optionally, the method comprises: and placing the nano carbon material and the molecular sieve in the same muffle furnace, and roasting at the temperature of 300-500 ℃ for 3-12 hours.

Optionally, the nanocarbon material is placed separately from the molecular sieve, and the nanocarbon material is located above the molecular sieve.

Optionally, the method further comprises: nitrogen and/or oxygen are introduced into the muffle to maintain the oxygen content in the muffle at 9-17 vol%, preferably 10-15 vol%.

Optionally, the weight ratio of the amount of the nanocarbon material to the amount of the molecular sieve is 1: (0.1-500), preferably 1: (1-100).

Optionally, the atmosphere resulting from calcining the molecular sieve contains a quaternary ammonium base, ammonia, an alcohol, a fatty amine, or an alcohol amine, or two or three thereof.

Optionally, the template is present in the molecular sieve in an amount of 1 to 20 wt%, based on the dry weight of the molecular sieve.

Optionally, the template agent is a quaternary ammonium base compound, a fatty amine compound or an alcohol amine compound, or a combination of two or three of the compounds;

preferably, the quaternary ammonium base compound is tetraethylammonium hydroxide, tetrabutylammonium hydroxide or tetrapropylammonium hydroxide, or two or three thereof;

the aliphatic amine compound is butanediamine, ethylamine, hexanediamine or n-butylamine, or two or three of the butanediamine, the ethylamine, the hexanediamine or the n-butylamine;

the alcohol amine compound is diethanolamine, monoethanolamine or triethanolamine, or a combination of two or three of the two or three.

Optionally, the carbon nanomaterial is selected from carbon nanotubes, nanographite, graphene, nanodiamond, fullerene, or activated carbon, or a combination of two or three thereof.

Optionally, the molecular sieve is selected from a titanium silicalite molecular sieve, a silicon-aluminum molecular sieve, an all-silicon molecular sieve or a vanadium-silicon molecular sieve, or a combination of two or three of them;

preferably, the molecular sieve is selected from TS-1, TS-2, Ti-MCM-22, Ti-MOR, Ti-beta or Ti-ZSM-48, or a combination of two or three thereof.

The second aspect of the invention provides a modified nano carbon material prepared by the method provided by the first aspect of the invention.

Optionally, the content of the total nitrogen element on the surface of the modified nano carbon material is 0.01-10 wt%, preferably 0.5-5 wt%;

the ratio of the weight content of nitrogen elements representing ammonia nitrogen species to the weight content of the total nitrogen elements on the surface of the modified nanocarbon material is 20 to 90%, preferably 40 to 80%.

In a third aspect, the invention provides a use of the modified nanocarbon material provided in the first aspect of the invention in preparation of olefin through alkane dehydrogenation.

By adopting the technical scheme, the ammonia nitrogen gas generated by the separation or decomposition of the nitrogenous organic template agent in the roasting process of the molecular sieve is directly utilized on site, so that the resource utilization of waste gas is realized, and the modified nano carbon material with more excellent catalytic oxidation performance can be prepared.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The present invention provides, in a first aspect, a method for producing a modified nanocarbon material, the method comprising: in the roasting process of the molecular sieve containing the template agent, the nano carbon material and the molecular sieve are roasted for 1 to 12 hours at the temperature of 300-600 ℃, and the oxygen content in the atmosphere is 8 to 20 volume percent in the roasting process.

The step of roasting the nano carbon material and the molecular sieve together refers to roasting the nano carbon material and the molecular sieve together in the same equipment under the same atmosphere.

The inventor of the invention finds that the ammonia nitrogen atmosphere generated by the desorption or decomposition of the nitrogenous organic template agent in the roasting process of the molecular sieve can be directly used for modifying the nano carbon material on site, so that the resource utilization of waste gas can be realized, and the modified nano carbon material with more excellent catalytic oxidation performance can be prepared. According to the method, nitrogen elements can be introduced to the surface of the nano carbon material in the modification process, namely, the surface of the modified nano carbon material contains the nitrogen elements, so that the prepared modified nano carbon material has better catalytic activity, and the conversion rate of the raw material and the selectivity of the raw material to a target product are further improved.

In one embodiment, the nano-carbon material and the molecular sieve containing the template are roasted together in the same roasting equipment at the temperature of 300-600 ℃ for 1-12 hours, and the oxygen content in the roasting atmosphere is 8-20% by volume. Preferably, the nanocarbon material and the molecular sieve containing the template are co-calcined at 300-500 ℃ for 3-12 hours.

In a preferred embodiment, the method comprises: and respectively placing the molecular sieve and the nano carbon material, wherein the nano carbon material is positioned above the molecular sieve.

In another more preferred embodiment, the method comprises: respectively placing the molecular sieve and the nano carbon material under the condition that the oxygen content is 10-20 vol%, wherein the nano carbon material is positioned above the molecular sieve, and roasting the molecular sieve and the nano carbon material at the temperature of 300-500 ℃ for 3-12 hours. In the specific implementation mode, the template removal agent of the molecular sieve calcination and the modification of the nano carbon material are carried out simultaneously in the equipment adopted by the molecular sieve calcination, so that the equipment investment can be reduced without additionally purchasing modification equipment and the like for fixing the assets. Meanwhile, in the roasting process, the nitrogen-containing organic template agent in the molecular sieve is removed or decomposed to generate ammonia nitrogen gas which can be directly and fully contacted with the nano carbon material, so that the prepared modified nano carbon material has better catalytic activity, and the conversion rate of the modified nano carbon material to raw materials and the selectivity of the modified nano carbon material to target products can be further improved.

According to the invention, the calcination treatment of the molecular sieve and the modification of the nanocarbon material can be carried out in an apparatus known to the person skilled in the art, which may be, for example, a muffle furnace or a tube furnace.

In a preferred embodiment, the method may comprise: the nano-carbon material and the molecular sieve are placed in the same muffle furnace and are roasted at the temperature of 300-600 ℃ for 1-12 hours, preferably at the temperature of 300-500 ℃ for 3-12 hours, and more preferably at the temperature of 350-450 ℃ for 3-8 hours.

In another preferred embodiment, the nanocarbon material is placed separately from the molecular sieve in a muffle furnace, and the nanocarbon material is located above the molecular sieve. According to the present invention, the specific relative positions of the carbon nanomaterial and the molecular sieve are not limited, and the upper side may be a right upper side or an obliquely upper side. Further preferably, the nanocarbon material is located closer to the gas outlet side of the muffle than the molecular sieve, i.e. the molecular sieve is located below the gas inlet of the muffle and the nanocarbon material is located above the gas outlet of the muffle. The modified nano carbon material with better catalytic activity can be prepared by adopting the method. The container for holding the nano material and the molecular sieve is not particularly limited, and may be a heat-resistant open container, such as a porcelain tray, a porcelain support net, etc., and a general porcelain boat may be used for laboratory preparation.

According to the invention, the method may further comprise: nitrogen and/or oxygen is introduced into the roasting apparatus such as a muffle furnace so that the oxygen content therein is maintained at 9 to 17 vol%, preferably 10 to 15 vol%, more preferably 11 to 14 vol%. The method of introducing nitrogen and/or oxygen is not particularly limited, and a method known to those skilled in the art may be used, and will not be described herein.

According to the present invention, the atmosphere generated by calcining the molecular sieve may contain a quaternary ammonium base, ammonia, an alcohol, a fatty amine, an alcohol amine, or the like, or two or three of them, preferably a quaternary ammonium base, an alcohol amine. Wherein, the alcohol can be monohydric alcohol, dihydric alcohol, trihydric alcohol or polyhydric alcohol, such as methanol, ethanol, ethylene glycol, etc. In the atmosphere created by calcining the molecular sieve, there are also organic substances such as alcohols, because the templating agent (e.g., quaternary ammonium base, etc.) will decompose to lower organic bases and alcohols, or to organic amines and alcohols, during the process. In the atmosphere generated by roasting the molecular sieve, organic matters such as alcohol and the like exist, and not only can participate in the modification process of the nano carbon material, so that the alcohol reacts with the surface functional groups of the nano carbon material, but also can react with oxygen in the modification process of the nano carbon material, so that the nano carbon material is effectively protected, side reactions such as ablation of the nano carbon material are effectively reduced and even avoided, the modification quality is improved, and the catalytic performance of the modified nano carbon material is further improved.

According to the invention, the weight ratio of the amount of nanocarbon material to molecular sieve may vary within wide limits, and may be, for example, 1: (0.1-500), preferably 1: (1-100).

The amount of templating agent in the molecular sieve according to the present invention can vary over a wide range, for example, from 1 to 20 wt.%, preferably from 5 to 18 wt.%, more preferably from 8 to 15 wt.%, based on the dry weight of the molecular sieve.

According to the invention, the template agent is a quaternary ammonium base compound, a fatty amine compound or an alcohol amine compound, or a combination of two or three of the quaternary ammonium base compound, the fatty amine compound and the alcohol amine compound.

Wherein, the molecular general formula of the quaternary ammonium base compound can be (R)¹)₄NOH wherein R¹May be selected from C₁-C₄Straight chain alkyl of (2) and C₃-C₄At least one of the branched alkyl groups of (a), for example, methyl, ethyl, n-propyl, isopropyl, isobutyl, methylene, sec-butyl, n-butyl or tert-butylpropyl. Preferably, the quaternary ammonium base compound is tetraethylammonium hydroxide, tetrabutylammonium hydroxide or tetrapropylammonium hydroxide, or two or three of them.

The molecular general formula of the aliphatic amine compound can be R²(NH₂)_nWherein R is²Can be C₁-C₆Straight chain alkyl of (2) and C₃-C₆At least one of the branched alkyl groups of (1), e.g. methyl, ethyl, n-alkylPropyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl or n-hexyl, R²May also be C₁-C₆For example methylene, ethylene, n-propylene, n-butylene or n-hexylene, n is an integer of 1 or 2. Preferably, the aliphatic amine compound is butanediamine, ethylamine, hexanediamine or n-butylamine, or two or three of them.

The molecular general formula of the alcohol amine compound can be (HOR)³)_mNH_(3-m)Wherein R is³Can be C₁-C₄M is an integer of 1, 2 or 3. Preferably, the alkanolamine is diethanolamine, monoethanolamine or triethanolamine, or a combination of two or three thereof.

According to the present invention, the carbon nanomaterial is well known to those skilled in the art and may be selected from, for example, carbon nanotubes, nanographite, graphene, nanodiamond, fullerene, or activated carbon, or a combination of two or three thereof.

According to the present invention, the molecular sieve may be any molecular sieve containing a template, for example, the molecular sieve may be selected from titanium-silicon molecular sieve, silicon-aluminum molecular sieve, all-silicon molecular sieve or vanadium-silicon molecular sieve in high-silicon molecular sieve, or a combination of two or three of them. Preferably a titanium silicalite molecular sieve, which can be selected from different topological structures such as TS-1, TS-2, Ti-MCM-22, Ti-MOR, Ti-beta or Ti-ZSM-48, or a combination of two or three of the above.

The second aspect of the invention provides a modified nano carbon material prepared by the method provided by the first aspect of the invention.

The inventors of the present invention found that nitrogen elements are introduced into the surface of the modified nanocarbon material of the present invention during the modification process, i.e., the surface of the modified nanocarbon material contains nitrogen elements.

According to the present invention, when nitrogen atoms are introduced into a nanocarbon material, the nitrogen atoms are generally classified into chemical nitrogen and structural nitrogen according to the chemical environment in which the nitrogen atoms are present in the nanocarbon material. The chemical nitrogen is mainly presented on the surface of the material in the form of surface functional group, such as amino or nitrosyl, etcA nitrogen-containing functional group. The structural nitrogen refers to nitrogen atoms bonded with carbon atoms entering a skeleton structure of the nano carbon material, and mainly comprises graphite type nitrogen, pyridine type nitrogen and pyrrole type nitrogen. In general, the N1s peaks in X-ray photoelectron spectroscopy (XPS) can be divided into three groups of peaks, namely peaks in the range of 403.5-406.5eV (corresponding to-NO)₂Species), peaks in the range of 400.6-401.5eV (corresponding to graphitic nitrogen species) and peaks in the range of 398.5-400.1eV (excluding graphitic nitrogen and-NO)₂Nitrogen species other than type nitrogen, typically NH-containing nitrogen species, i.e., ammonia nitrogen-based nitrogen species).

In one embodiment, the total nitrogen content of the surface of the modified nanocarbon material is 0.1 to 10% by weight, preferably 0.5 to 5% by weight; the ratio of the weight content of nitrogen elements representing ammonia nitrogen species on the surface of the modified nano carbon material to the total weight content of nitrogen elements on the surface of the modified nano carbon material is 20-90%, preferably 40-80%, wherein the ammonia nitrogen species refers to nitrogen species in the range of 398.5-400.1eV in an N1s XPS spectrum. The total nitrogen content on the surface of the modified nanocarbon material and the weight content of nitrogen representing ammonia nitrogen species can be measured by XPS. The XPS measurement method is well known to those skilled in the art and there is no particular requirement for the present invention.

The third aspect of the invention provides an application of the modified nano carbon material provided by the second aspect of the invention in olefin preparation through alkane dehydrogenation.

Alkanes according to the present invention are well known to those skilled in the art and are not particularly limited herein, and may be, for example, monocyclic cycloalkanes of C5-C9, bicyclic cycloalkanes of C10-C20.

Conditions for the dehydrogenation of alkanes to olefins in accordance with the present invention are well known to those skilled in the art and, in one embodiment, may include: the temperature is 280-450 ℃ and the time is 0.1-24 hours. The dehydrogenation of alkanes to olefins may be carried out in apparatuses conventionally employed by those skilled in the art, and may be, for example, a fixed bed reactor or a slurry bed reactor.

According to the present invention, the amount of the modified nanocarbon material used may vary within a wide range, for example, from 0.01 to 10g, preferably from 0.1 to 2g, based on 100mL of alkane.

The invention is further illustrated by the following examples, but is not to be construed as being limited thereto.

The reagents adopted by the invention are all commercial analytical pure reagents. The templating agent-containing titanium silicalite molecular sieves (TS-1) used in the comparative examples and examples were samples of molecular sieves (TS-1) prepared according to the methods described in Zeolite, 1992, Vol.12, pp.943 to 950 of the prior art.

The preparation method of the molecular sieve (TS-1-1) comprises the following steps: 22.5 g of tetraethyl orthosilicate was mixed with 7.0 g of tetrapropylammonium hydroxide (25% aqueous solution), 50 g of distilled water was added and further mixed uniformly, a solution consisting of 1.1 g of tetrabutyl titanate and 5.0 g of anhydrous isopropanol was slowly added with vigorous stirring, and the resulting mixture was stirred at 75 ℃ for 3 hours to give a colloid. Placing the colloid in a stainless steel reaction kettle, and standing at a constant temperature of 170 ℃ for 3 days to obtain a mixture of crystallized products; filtering the mixture, washing with water, and drying at 110 deg.C for 60 min to obtain the product containing template agent titanium-silicon molecular sieve (TS-1-1), wherein the content of template agent in the molecular sieve TS-1-1 is 14 wt%.

The preparation method of the molecular sieve (TS-1-2) comprises the following steps: 22.5 g of tetraethyl orthosilicate was mixed with 15 g of tetraethylammonium hydroxide (25% aqueous solution), 50 g of distilled water was added and further mixed well, a solution consisting of 1.1 g of tetrabutyl titanate and 5.0 g of anhydrous isopropanol was slowly added with vigorous stirring, and the resulting mixture was stirred at 75 ℃ for 3 hours to give a colloid. Placing the colloid in a stainless steel reaction kettle, and standing at a constant temperature of 140 ℃ for 6 days to obtain a mixture of crystallized products; filtering the mixture, washing with water, and drying at 110 deg.C for 60 min to obtain the product containing template agent titanium-silicon molecular sieve (TS-1-2), wherein the content of template agent in the molecular sieve TS-1-2 is 22 wt%.

In the comparative examples and the examples, the total content of nitrogen elements and the ammonia nitrogen content of the surface of the material were measured by an X-ray photoelectron spectroscopy (XPS) method. An X-ray photoelectron spectrometer model ESCALb 220i-XL equipped with Avantage V5.926 software manufactured by VG Scientific corporation was used,the excitation source is monochromatized Al alpha X-ray, the power is 300W, and the basic vacuum in the analysis test is 3 multiplied by 10^-7Pa, processing data on ThermoAvantage software, and carrying out quantitative analysis in an analysis module by adopting a sensitivity factor method.

Example 1

2g of CNT (carbon nano tube, the average tube diameter is 25nm) and 100g of template-containing titanium silicalite molecular sieve (TS-1-1) are respectively placed on a ceramic tray (ceramic boat), the ceramic tray is transferred into a muffle furnace, the two trays are not overlapped, the ceramic tray containing the CNT is obliquely arranged above the ceramic tray containing the template-containing titanium silicalite molecular sieve (TS-1-1), and the position of the ceramic tray containing the CNT is deviated to the gas outlet side. And (2) closing a muffle door, heating to 400 ℃ and roasting for 6 hours, and introducing nitrogen and oxygen in the process to ensure that the oxygen content in the atmosphere generated by roasting the template-containing titanium silicalite molecular sieve (TS-1-1) is 11 volume percent. And after the baking and sintering, taking out the ceramic tray filled with the CNT after the temperature of the muffle furnace is cooled to be below 50 ℃, thereby obtaining the modified nano carbon material A. The surface nitrogen content and the ammonia nitrogen content are shown in the table 1 and the same below.

Example 2

1g of graphene (average lamella thickness is 3nm) and 100g of titanium silicalite molecular sieve containing template (TS-1-1) are respectively placed on a porcelain tray (porcelain boat). And transferring the mixture to the same horizontal line in a muffle furnace, enabling the position of a porcelain tray filled with graphene to be deviated to the gas outlet side, closing a muffle furnace door, heating to 450 ℃ for roasting for 5 hours, and introducing nitrogen and oxygen in the process to enable the oxygen content in the atmosphere generated by roasting the titanium-silicon molecular sieve (TS-1-1) containing the template to be 10 volume percent. And after the baking and sintering, taking out the ceramic tray filled with the graphene when the temperature of the muffle furnace is cooled to be below 50 ℃ to obtain the modified nano carbon material B.

Example 3

The modified nanocarbon material C was prepared in the same manner as in example 1, except that the muffle door was closed, and then the temperature was raised to 550 ℃ to perform calcination for 4 hours.

Example 4

The modified nanocarbon material D was prepared by the same method as in example 1, except that the ceramic tray containing the CNT was at the same level as the ceramic tray containing the templating agent-containing titanium silicalite molecular sieve (TS-1-1).

Example 5

The modified carbon nanomaterial E was prepared by the same method as in example 1, except that nitrogen and oxygen were introduced during the calcination process, so that the oxygen content in the atmosphere generated by calcination of the template-containing titanium silicalite molecular sieve (TS-1-1) was 8 vol%.

Example 6

The modified carbon nanomaterial F was prepared by the same method as in example 1, except that the templating agent-containing titanium silicalite molecular sieve (TS-1-1) was replaced with the templating agent-containing titanium silicalite molecular sieve (TS-1-2).

Example 7

The modified nanomaterial G was prepared by the same method as in example 1, except that 0.1G of cnt (carbon nanotubes, average diameter of 25nm) and 100G of the templating agent-containing titanium silicalite molecular sieve (TS-1-1) were placed on a porcelain tray (porcelain boat), respectively.

Comparative example 1

A comparative modified nano carbon material a was prepared by the same method as in example 1, except that the titanium silicalite molecular sieve (TS-1-1) containing the template agent was replaced with the same mass of titanium silicalite molecular sieve (TS-1-1) which did not contain the template agent after calcination.

In a muffle furnace, 2g of CNT and 100g of titanium silicalite molecular sieve (TS-1-1) which is roasted and does not contain a template agent are respectively arranged on a porcelain tray, the porcelain tray filled with the CNT is ensured to be obliquely above the porcelain tray filled with the titanium silicalite molecular sieve (TS-1-1), and the position of the porcelain tray filled with the CNT is deviated to the gas outlet side. And (2) closing a muffle door, heating to 400 ℃ and roasting for 6 hours, and introducing a proper amount of nitrogen and oxygen in the process to ensure that the oxygen content in the roasting atmosphere of the titanium silicalite molecular sieve (TS-1-1) without the template is 11%. After the completion of the baking, the ceramic tray containing the CNTs was taken out after the muffle furnace temperature was cooled to 50 ℃ or lower, and a comparative modified nanocarbon material a was obtained.

Comparative example 2

A comparative modified nanocarbon material b was prepared in the same manner as in example 1, except that the templating agent-containing titanium silicalite molecular sieve (TS-1-1) was replaced with the same mass of the templating agent solution.

In a muffle furnace, 2g of CNT and 100g of tetrapropylammonium hydroxide solution (14 wt% concentration) were placed on a porcelain tray, respectively, and the tray containing the CNT was placed above the tray containing the templating agent. And (3) closing a muffle door, raising the temperature to 400 ℃ and roasting for 6 hours, and introducing nitrogen and oxygen in the process to ensure that the oxygen content in the roasting atmosphere is 11 volume percent. After the completion of the baking, the ceramic tray containing the CNTs was taken out after the muffle furnace temperature was cooled to 50 ℃ or lower, and a comparative modified nanocarbon material b was obtained.

Comparative example 3

The modified nano carbon material c is prepared by the same method as the embodiment 1, except that the muffle door is closed, the temperature is raised to 400 ℃ and the calcination is carried out for 6 hours, and nitrogen and oxygen are introduced in the process, so that the oxygen content in the atmosphere generated by the calcination of the template-containing titanium silicalite molecular sieve (TS-1-1) is 25 volume percent.

Comparative example 4

The modified nano carbon material d is prepared by the same method as the embodiment 1, except that the muffle door is closed, the temperature is raised to 400 ℃ for roasting for 6 hours, and only nitrogen is introduced in the process, so that the atmosphere generated by roasting the titanium silicalite molecular sieve (TS-1-1) containing the template agent does not contain molecular oxygen.

Comparative example 5

The modified nanocarbon material e was prepared in the same manner as in example 1, except that the calcination temperature was 200 ℃ and the calcination time was 24 hours.

Test example

50mg of the modified nanocarbon materials prepared in examples and comparative examples, and the unmodified nanocarbon material were each charged as a catalyst into a universal fixed bed microtquartz tube reactor, both ends of which were sealed with quartz sand, and the reaction was carried out under normal pressure and at 420 ℃ at a total volume flow rate of 25mL/min for materials (butane concentration of 1.98 vol%, butane and oxygen molar ratio of 1: 2, equilibrium gas being nitrogen), and after 6 hours of the reaction, the oxidation product was analyzed by gas chromatography (GC: Agilent, 7890A), and the butane conversion, butadiene selectivity, and total olefin selectivity were measured according to the methods in the literature (Jian Zhang et al, Science 322(2008), 73-77), and the results are shown in Table 1.

Conditions of GC: nitrogen carrier gas, temperature programmed at 140K: 60 ℃, 1 minute, 15 ℃/minute, 180 ℃, 15 minutes; split ratio, 10: 1; the injection port temperature is 300 ℃; detector temperature, 300 ℃.

The butane conversion, butadiene selectivity and total olefin selectivity are calculated as follows:

the conversion of butane is the amount of butane participating in the reaction/amount of butane added x 100%,

butadiene selectivity is the amount of butadiene in the product/amount of butane participating in the reaction x 100%,

total olefin selectivity is the total amount of olefins in the product/amount of butanes participating in the reaction x 100%.

TABLE 1

Wherein, the ratio of ammonia nitrogen to ammonia nitrogen in table 1 means the ratio of the weight content of nitrogen element representing ammonia nitrogen type nitrogen species to the weight content of total nitrogen element on the surface of the modified nanocarbon material.

The modified nano carbon material prepared by the method has better olefin selectivity, and has higher selectivity to olefin and conversion rate of raw materials when being used for the reaction of preparing olefin by selectively converting alkane. Preferably, the nano-carbon material and the molecular sieve are placed in the same muffle furnace and are roasted for 3-12 hours at the temperature of 300-500 ℃, so that the modified nano-carbon material with better catalytic activity can be prepared; preferably, the nano-carbon material and the molecular sieve are respectively placed, and when the nano-carbon material is positioned above the molecular sieve, the modified nano-carbon material with better catalytic activity can be prepared; preferably, when the content of the template agent in the molecular sieve is 1-20 wt% based on the dry weight of the molecular sieve, the modified nano carbon material with better catalytic activity can be prepared; preferably, the weight ratio of the nano carbon material to the molecular sieve is 1: (0.1-500), the modified nano carbon material with better catalytic activity can be prepared.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.