A method for preparing petroleum coke-based carbon nanotubes and its application in Pb 2+ detection

Abstract

The present disclosure provides a preparation method of petroleum coke-based carbon nanotubes and its application in Pb2+ detection. The method comprises the following steps: crushing, grinding and screening the petroleum coke raw material to obtain petroleum coke primary powder; pretreating the petroleum coke primary powder with an oxidizing agent, adding the petroleum coke primary powder into the oxidizing agent solution to form a suspension, heating in a hydrothermal reactor, washing the solid product to neutral, and drying to obtain petroleum coke secondary powder; mixing the petroleum coke secondary powder and a template agent, placing in a closed furnace body, filling with protective gas, activating, and then washing with water and drying to obtain petroleum coke-based carbon nanotubes. The petroleum coke-based carbon nanotubes are applied to detect ultra-trace Pb 2+ A high-sensitivity electrochemical sensing platform can be constructed, which has the advantages of high sensitivity and strong anti-interference ability.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for preparing petroleum coke-based carbon nanotubes and applications thereof. BACKGROUND

[0002] In recent years, due to the rapid development of renewable and sustainable energy, the proportion of fossil fuels such as petroleum in the energy structure of our country is gradually decreasing. However, in the foreseeable future, petroleum will still play an indispensable role in modern society. The petroleum industry is the largest industry, which not only produces automobile fuel, but also produces many products that almost penetrate into every aspect of our life. Due to the long-term overconsumption of petroleum resources, one of the very serious situations we have to face now is that the crude oil supplied to the petroleum industry is becoming heavier and heavier, which inevitably leads to the production of more and more low-value and extremely heavy by-products such as asphalt and petroleum coke. Therefore, how to effectively utilize these heavy by-products poses a great challenge to today's petroleum industry.

[0003] Compared with carbon from biomass and / or polymer precursors, polycyclic aromatic hydrocarbon-derived carbon has higher electrical conductivity and tunability. In addition, petroleum coke is usually carbonized by a liquid-phase process, which provides multiple opportunities for carefully manipulating the structure of the final carbon material. These characteristics make heavy by-products of the petroleum industry excellent precursors for building new types of nanostructured carbon. Through innovative and simple methods, zero-dimensional carbon quantum dots, one-dimensional carbon nanofibers, two-dimensional carbon nanosheets, and three-dimensional carbon frameworks have been successfully prepared. Compared with biomass and polymer precursors, heavy oil-derived precursors have rich tunability, low cost, and wide availability, which makes them more competitive in producing new types of nanostructured carbon materials.

[0004] CN101908389A uses cheap petroleum coke powder to replace expensive inert gas as air isolation medium for preparation of activated carbon / carbon nanotube mixed electrode material; CN104362344A physically mixes pitch coke, natural graphite, mesocarbon microbeads and a substance selected from needle coke or carbon mold material powder in a certain mass ratio, and then prepares a graphite matrix material for lithium ion battery negative electrode material under high temperature conditions of above 2000 DEG C in vacuum or with a protective atmosphere for 1 hour or more; CN116553528A uses waste plastic as raw material, first introduces transition metal precursor and support precursor in the petroleum coke activation process, and obtains a catalytic material precursor by in-situ synthesis, and then prepares easy functionalized carbon nanotubes by one-step pyrolysis. CN103887523A discloses a method for preparing a microbial fuel cell air cathode using petroleum coke as raw material, which realizes resource utilization of petroleum coke and full utilization of natural resources. CN109665522A adopts a method for preparing graphene modified activated carbon using hydrophilic petroleum coke, and realizes oxidation of petroleum coke under mild conditions by using an oxidizing agent to obtain hydroxylated petroleum coke, increases the hydrophilic functional groups on the surface of petroleum coke, and makes the oxidized graphene more uniformly coated on the surface of petroleum coke, so that the activated carbon has high electrical conductivity and reduces the internal resistance of the carbon material. Although the materials prepared by the above methods can realize effective utilization of petroleum coke, the above preparation processes are very complex and have high energy consumption.

[0005] According to the search, there is no report on the preparation of carbon nanotubes using petroleum coke as raw material without adding metal catalyst. SUMMARY

[0006] The present disclosure provides a preparation method of petroleum coke-based carbon nanotubes, which uses petroleum coke as a precursor and prepares petroleum coke-based carbon nanotubes through an in-situ deformation strategy. Moreover, it has been proved by characterization means that the petroleum coke-based carbon nanotubes can be used to construct a high-sensitivity electrochemical sensing platform for detecting ultra-trace Pb 2+ The constructed sensor has high sensitivity and strong anti-interference ability, which provides a feasible research direction for using petroleum coke as a carbon source to synthesize high-value-added carbon materials.

[0007] The technical solution provided by the present disclosure is as follows:

[0008] A preparation method of petroleum coke-based carbon nanotubes, comprising the following steps: using petroleum coke as a precursor, and preparing petroleum coke-based carbon nanotubes through an in-situ deformation strategy, specifically comprising:

[0009] The petroleum coke raw material is crushed, ground and sieved to obtain petroleum coke primary powder;

[0010] The primary petroleum coke powder is pretreated by an oxidant, the primary petroleum coke powder is added into an oxidant solution to form a uniform suspension, the suspension is heated in a hydrothermal reactor, the solid product is washed with water until neutral, and dried to obtain the pretreated secondary petroleum coke powder;

[0011] The pretreated secondary petroleum coke powder is mixed with a template agent, and placed in a closed furnace body, and then protected gas is filled in to activate the mixture, and then the activated product is washed with water and dried to obtain the petroleum coke-based carbon nanotube.

[0012] The oxidant includes one or more of hydrogen peroxide, sulfuric acid, nitric acid and perchloric acid, and the template agent includes one or more of graphite phase carbon nitride, urea, melamine and thiourea.

[0013] Further, the method of crushing the petroleum coke raw material is one of ball milling, air jet milling or mechanical milling; and the particle size of the primary petroleum coke powder is less than 80 mesh.

[0014] Further, the ratio of the primary petroleum coke powder to nitric acid is 10 g of petroleum coke to 8 mL of 1M HNO3.

[0015] Further, the suspension is heated in the hydrothermal reactor at a temperature of 80°C for 8 hours.

[0016] Further, when the pretreated secondary petroleum coke powder is mixed with the template agent, the mass ratio of the pretreated secondary petroleum coke powder to the template agent is 1:(1-6).

[0017] Further, when the protected gas is filled in to activate the mixture, the activation temperature is 800°C, and the activation time is 2 hours.

[0018] The second aspect of the present disclosure provides the petroleum coke-based carbon nanotube prepared by the above-mentioned method for detecting Pb 2+ in an actual water sample after high-temperature calcination.

[0019] The third aspect of the present disclosure provides a method for constructing an electrochemical sensing platform, which comprises weighing a certain amount of the petroleum coke-based carbon nanotube prepared by the above-mentioned method, preparing a petroleum coke-based carbon nanotube film on the surface of a glassy carbon electrode to obtain a modified glassy carbon electrode, uniformly casting a carbon nanotube-water-ethanol solution on the surface of the polished modified glassy carbon electrode, and drying the modified glassy carbon electrode at room temperature to form an electrochemical sensing platform capable of detecting Pb 2+ in 0.1M HAc-NaAc (pH=5.0).

[0020] As a preferred solution:

[0021] The preparation of the petroleum coke-based carbon nanotube film on the surface of the glassy carbon electrode requires that the glassy carbon electrode on the felt is polished with 0.3mm and 0.05mm alumina powder slurries in sequence, and then 5ul of the carbon nanotube-water-ethanol solution is uniformly dropped on the surface of the modified glassy carbon electrode after polishing.

[0022] Further, the drying time of the modified glassy carbon electrode at room temperature is 3-8h.

[0023] The petroleum coke is pretreated by nitric acid, the pore structure and the microcrystalline structure of the petroleum coke are changed, and the petroleum coke-based carbon nanotube is synthesized for the first time by using the graphite phase carbon nitride as a template.

[0024] 1) The petroleum coke used in the application has rich adjustability, low cost and wide availability, which is conducive to mass production.

[0025] 2) The petroleum coke is used as a carbon source, and high value-added conversion of the petroleum coke to carbon nanotubes can be realized.

[0026] 3) The graphite phase carbon nitride is used as a template agent, which has the advantages of easy preparation, low price, good thermal stability, etc., and can be easily removed by water washing, thereby minimizing the damage to the carbon nanotubes. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Scanning electron microscope images of petroleum coke-based carbon nanotubes prepared with different proportions of template agents.

[0028] Figure 2 XRD image of petroleum coke-based carbon nanotubes.

[0029] Figure 3 XPS image of petroleum coke-based carbon nanotubes after adsorbing heavy metal ions (a) C 1s; (b) N 1s; (c) O 1s; (d) Pb 4f; (e) Cd 3d; (f) Cu 2p.

[0030] Figure 4 The anodic stripping voltammogram of the petroleum coke-based carbon nanotube modified glassy carbon electrode for detecting Pb 2+ in 0.1M HAc-NaAc (pH=5.0).

[0031] Figure 5 The anodic stripping voltammogram of the petroleum coke-based carbon nanotube modified glassy carbon electrode for detecting different concentrations of Pb 2+ in 0.1M HAc-NaAc (pH=5.0) when the template ratio is 4. DETAILED DESCRIPTION

[0032] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0033] In the present application, the open technical features include the closed technical solutions composed of the listed features, and also include the open technical solutions containing the listed features.

[0034] In the present application, if no special description is made, the numerical range is regarded as continuous and includes the minimum value and the maximum value of the range and each value between the minimum value and the maximum value. Further, when the range is an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all the ranges disclosed herein should be understood as including any and all sub-ranges.

[0035] In the present application, the specific dispersion and stirring treatment method is not particularly limited. In the present application, unless otherwise specified, the part is mass part.

[0036] The reagents or instruments used in the present application are not specified by the manufacturer, and are all conventional products that can be obtained by purchase. The raw material information used in the embodiments and comparative examples of the present application is as follows:

[0037] The petroleum coke is from a certain petrochemical company; glacial acetic acid, urea, concentrated nitric acid, sodium acetate trihydrate and lead chloride are purchased from the Chemical Reagent Co., Ltd. of China National Pharmaceutical Group.

[0038] The specific embodiments disclosed in the present application prepare a petroleum coke-based carbon nanotube and are used for detecting Pb 2+ At the same time, the sensitivity and anti-interference performance of the sensing platform are systematically studied. The carbon nanotube has a multi-layer adsorption effect and can provide sufficient active sites. The XPS study also reveals the selective adsorption of Pb 2+ , indicating that it has good anti-interference performance. The petroleum coke-based carbon nanotube prepared by the present application provides a feasible research direction for synthesizing high-value-added carbon materials using abundant petroleum coke as a carbon source.

[0039] The present application will be further explained and described below in combination with specific embodiments.

[0040] Embodiment 1:

[0041] This example illustrates a method for preparing petroleum coke-based carbon nanotubes and SEM characterization:

[0042] a) Pretreatment of petroleum coke

[0043] The petroleum coke was pretreated with nitric acid. The specific steps are as follows: 10 g of petroleum coke was added to a 1 M HNO3 solution (8 mL) and stirred vigorously to form a uniform suspension. Then the suspension was placed in a hydrothermal reactor and heated at 80 °C for 8 h. Then, the pretreated petroleum coke was collected and washed with deionized water.

[0044] b) Preparation of the template

[0045] Urea (10 g) was calcined in air at 520 °C for 4 h (heating rate 5 °C / min) to prepare a yellow graphitic carbon nitride template. The product was allowed to cool in air and then removed. It was ground into a powder in a mortar and pestle for later use.

[0046] c) Activation of petroleum coke

[0047] A certain amount of pretreated petroleum coke powder was mixed with the graphitic carbon nitride in a weight ratio of 1:4 in a mortar and pestle to ensure uniform mixing. The mixed powder was placed in a porcelain boat and placed in a tube furnace for activation under nitrogen. The temperature of the tube furnace was increased to 800 °C at a rate of 5 °C / min and held for 2 h. After the activation process was complete, the petroleum coke activation product was allowed to cool in a nitrogen environment and then removed. It was rinsed with deionized water until the pH was close to neutral and then dried in a drying oven at 80 °C. The dried activation product was ground into a powder in a mortar and pestle for later use.

[0048] The petroleum coke-based carbon nanotubes described above were characterized by SEM, and the results are shown in Figure 1 The graphitic carbon nitride template was fully converted to various N-containing gases during pyrolysis, inducing the in-situ bending of the carbon matrix and absorbing nitrogen atoms. The N-CNTs with different amounts of template were characterized by SEM to further study the function of the graphitic carbon nitride template. When the mass ratio of petroleum coke to graphitic carbon nitride template in the initial mixture reached 1:4, most of the carbon matrix was converted into a uniform tubular morphology. However, it should be noted that as the content of graphitic carbon nitride template increased to a certain extent, the carbon matrix could not be completely converted into a tubular structure. The obtained N-CNTs were in a tubular structure with a highly smooth appearance, which was conducive to capturing target ions, and also showed that the diameter of the individual carbon nanotubes was about 200 nm.

[0049] Example 2:

[0050] This example illustrates a method for preparing petroleum coke-based carbon nanotubes and XRD characterization:

[0051] In order to analyze the crystal structure of carbon nanotubes, the petroleum coke-based carbon nanotubes prepared in the first step were characterized by XRD. The results show that the spectrum shows two carbon main peaks, and the low intensity (002) wide peak indicates that the prepared carbon nanotube has a low degree of graphitization. Figure 2 ), the spectrum shows two carbon main peaks, and the low intensity (002) wide peak indicates that the prepared carbon nanotube has a low degree of graphitization. The two significant characteristic peaks of carbon are clearly visible in all samples, and are arranged in order along the stacking direction, which is related to the degree of graphitization. In particular, with the different amounts of graphitic nitrogen carbon added, the interlayer spacing of the carbon layer increases significantly, revealing the influence of N doping and N-containing gas (such as C2N2 + , C3N2 + , C3N3 + ) stripping process.

[0052] Test and results

[0053] The specific method for investigating the heavy metal ion detection performance provided by the present application is as follows:

[0054] The steps for preparing the petroleum coke-based carbon nanotube film on the surface of the glassy carbon electrode are as follows: first, the glassy carbon electrode on the felt is polished with 0.3 mm and 0.05 mm alumina powder slurries in sequence. Then, 5 μL of the carbon nanotube-water-ethanol solution is uniformly cast on the surface of the just polished glassy carbon electrode. Finally, the modified glassy carbon electrode is dried at room temperature for about 4 h. With it, Pb 2+ is detected in 0.1 M HAc-NaAc (pH = 5.0).

[0055] Figure 3 For the chemical state and element composition of the heavy metal ions adsorbed by the carbon nanotubes, the presence of N element in the XPS spectrum of the carbon nanotubes may be related to the pyrolysis reaction of graphitic nitrogen carbon, which produces some N-containing gas. In the high-resolution N1s spectrum of the carbon nanotube, the three component peaks of pyridine-N (398.2 eV), pyridine-N (399.8 eV) and quaternary ammonium salt-N (401.2 eV) coexist, and the XPS spectra of Pb 4f, Cd 3d and Cu 2p reveal the difference in adsorption capacity of the carbon nanotubes to Pb 2+ , Cu 2+ and Cd 2+ (three heavy metal ions) ( Figure 3 d-f). Note that the adsorption capacity of Pb 2+ is much higher than that of Cu 2+ and Cd 2+ . That is, we can make full use of the strong chemical interaction between Pb 2+ and the carbon nanotubes to construct a high-sensitivity sensing platform.

[0056] Figure 4 The carbon nanotubes prepared with different ratios of template agent are used to detect Pb 2+The peak current of the carbon nanotube modified glassy carbon electrode prepared by using the petroleum coke and template ratio of 1:4 can reach 33.1 μA, which is superior to the carbon nanotubes prepared by using other ratios of template.

[0057] Figure 5 The anodic stripping voltammograms of different concentrations of Pb 2+ were detected by using the petroleum coke based carbon nanotube modified glassy carbon electrode prepared by using the template ratio of 4 in 0.1 M HAc-NaAc (pH=5.0). As shown in the figure, the anodic stripping voltammograms of the obtained electrode have obvious Pb 2+ current signals at about 0.5 V. In the concentration range of 0.1-4 μM, the stripping peak current has a good linear relationship with the concentration of Pb 2+ . The corresponding linear equation (see the inserted figure) is Y=4.991+6.517X, which shows a high correlation coefficient value (R 2 ≥0.99). It is worth noting that the detection sensitivity of the petroleum coke based carbon nanotube modified glassy carbon electrode to Pb 2+ is as high as 6.517 μA·μM -1 ·cm -2

[0058] Although the content of the present application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation to the present application.

Claims

1. A method for producing petroleum coke-based carbon nanotubes, characterized by, Preparation of petroleum coke-based carbon nanotubes by in-situ deformation strategy, including the following steps: The petroleum coke raw material is crushed, ground, and sieved to obtain a petroleum coke primary powder; The petroleum coke primary powder is pretreated with an oxidizing agent, the petroleum coke primary powder is added to an oxidizing agent solution, and the mixture is stirred to form a uniform suspension, the suspension is heated in a hydrothermal reactor, the solid product is washed to neutral, and dried to obtain a pretreated petroleum coke secondary powder; The suspension is heated in the hydrothermal reactor at a temperature of 80°C for 8 hours; The pretreated petroleum coke secondary powder and a template agent are mixed and placed in a closed furnace, protected gas is filled, and activation is performed, the activated product is then washed with water and dried to obtain petroleum coke-based carbon nanotubes; In the step of mixing the pretreated petroleum coke secondary powder and the template agent, the mass ratio of the pretreated petroleum coke secondary powder to the template agent is 1:(1-6); in the step of filling the protected gas for activation, the activation temperature is 800°C, and the activation time is 2 hours; The oxidizing agent is nitric acid, the template agent is graphite-phase carbon nitride, and the ratio of the petroleum coke primary powder to the nitric acid is 10g of petroleum coke to 8mL of 1M HNO3.

2. The method of claim 1, wherein: The method for crushing the petroleum coke raw material is one of ball milling, air-jet milling, or mechanical milling; the particle size of the petroleum coke primary powder is less than 80 mesh.

3. The petroleum coke-based carbon nanotube prepared by the method of any one of claims 1-2, wherein the petroleum coke-based carbon nanotube, after high-temperature calcination, is used for detecting Pb in an actual water sample. 2+ applications.

4. A method of constructing an electrochemical sensing platform, characterized by: A certain amount of petroleum coke-based carbon nanotubes prepared by the method of any one of claims 1-2 is weighed, a petroleum coke-based carbon nanotube film is prepared on the surface of a glassy carbon electrode, and a modified glassy carbon electrode is obtained; the specific preparation method is that the carbon nanotube-water-ethanol solution is uniformly drop-cast on the surface of a just polished glassy carbon electrode; the modified glassy carbon electrode is dried at room temperature to form an electrochemical sensing platform capable of detecting Pb 2+ in 0.1M HAc-NaAc, pH=5.

0.

5. The method of claim 4, wherein: In the step of preparing the petroleum coke-based carbon nanotube film on the surface of the glassy carbon electrode, the glassy carbon electrode on the felt is first polished with 0.3mm and 0.05mm alumina powder slurries, and then 5μL of the carbon nanotube-water-ethanol solution is uniformly cast on the surface of the modified glassy carbon electrode after polishing.

6. The method of claim 5, wherein: The modified glassy carbon electrode is dried at room temperature for 3-8 hours.

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