CN109046461B

CN109046461B - Preparation method of sulfur-containing complex catalyst and method for preparing spiral carbon nanofibers through catalysis of sulfur-containing complex catalyst

Info

Publication number: CN109046461B
Application number: CN201810890923.7A
Authority: CN
Inventors: 龚勇; 陈建; 辜其隆; 廖明东; 黄坤; 金永中; 管清宇; 王伦露; 任意如
Original assignee: Sichuan University of Science and Engineering
Current assignee: Sichuan University of Science and Engineering
Priority date: 2018-08-07
Filing date: 2018-08-07
Publication date: 2021-07-20
Anticipated expiration: 2038-08-07
Also published as: CN109046461A

Abstract

The invention discloses a preparation method of a sulfur-containing complex catalyst and a method for preparing spiral carbon nanofibers by catalysis of the sulfur-containing complex catalyst, wherein the preparation method of the sulfur-containing complex catalyst comprises the steps of (1) respectively preparing a potassium sodium tartrate solution and a nickel chloride solution, and dropwise adding the potassium sodium tartrate solution into the nickel chloride solution under the stirring condition; (2) after the dropwise adding is finished, transferring the mixed solution into a reaction kettle for hydrothermal reaction; (3) after the hydrothermal reaction is finished, standing the mixed solution, removing supernatant liquor, carrying out suction filtration and washing on the precipitate, and drying to obtain tartrate radical and Ni²⁺A complex of (a); (4) adding the obtained complex and sulfur powder into a ball milling tank according to the mass ratio of 10-100: 1, carrying out ball milling, and grinding dried materials into powder to obtain the sulfur-containing complex catalyst. When the sulfur-containing complex catalyst prepared by the invention is used for preparing the spiral carbon fiber, hydrogen is not needed to be introduced for reduction, and the uniform and high-purity spiral carbon nanofiber can be prepared at a low temperature.

Description

Preparation method of sulfur-containing complex catalyst and method for preparing spiral carbon nanofibers through catalysis of sulfur-containing complex catalyst

Technical Field

The invention belongs to the field of preparation of spiral carbon nanofibers, and particularly relates to a preparation method of a sulfur-containing complex catalyst and a method for preparing spiral carbon nanofibers through catalysis of the sulfur-containing complex catalyst.

Technical Field

The spiral carbon nanofiber has good mechanical property, thermal property, wave-absorbing property, hydrogen storage property and the like due to the unique spiral structure, and attracts the attention of a plurality of scientific researchers. At present, the preparation of the spiral carbon nanofiber mainly adopts a chemical vapor deposition method (CVD method) and takes simple substances of iron, cobalt, nickel or copper or compounds thereof as catalysts to catalyze the high-temperature (600-1200 ℃) cracking deposition preparation of an organic carbon source. Since the chemical vapor deposition is affected by many factors such as temperature, gas flow rate, and temperature rise rate, it is still a serious challenge to prepare the spiral carbon nanofibers with uniform spiral structure and high purity. Meanwhile, a hydrogen reduction catalyst is often introduced in the preparation process of the spiral carbon nanofibers, so that serious potential safety hazards are caused.

Due to the above factors, the spiral carbon nanofibers are difficult to realize industrial production at present and are only limited to unstable small-batch preparation in a laboratory, so that the related excellent applications of the spiral carbon nanofibers cannot be further researched. Liu et al (Direct synthesis of micro-linked carbon fibers on graphite substrates using co-electrodeposition of nickel and sulfur as catalysts [ J ] Materials & Design, 2009, 30(3): 649-. Although the method relieves the agglomeration phenomenon of the nano nickel particles to a certain extent, the operation steps are complicated and the mass production is not facilitated; and at the same time, the contact area of the catalyst and acetylene is reduced, resulting in a reduction in yield. Therefore, the method for obtaining the nano catalyst particles with good dispersibility by decomposing the precursor in the heat treatment process is a simple and effective method for solving the agglomeration phenomenon of the nano catalyst particles.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method of a sulfur-containing complex catalyst, which solves the problems that hydrogen needs to be introduced to reduce the catalyst and nano nickel particles are easy to agglomerate in the existing preparation process of spiral nano carbon fibers.

The invention also provides a method for preparing the spiral carbon nanofiber by using the catalyst prepared by the method, and solves the problem that the existing method is difficult to prepare the uniform and high-purity spiral carbon nanofiber.

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

a preparation method of a sulfur-containing complex catalyst comprises the following steps:

(1) respectively preparing a potassium sodium tartrate solution and a nickel chloride solution, wherein the molar ratio of potassium sodium tartrate to nickel chloride is 1: 0.95-1, and dropwise adding the prepared potassium sodium tartrate solution into the nickel chloride solution under the condition of stirring;

(2) after the dropwise adding is finished, transferring the mixed solution into a reaction kettle for hydrothermal reaction;

(3) after the hydrothermal reaction is finished, standing the mixed solution, removing supernatant liquor, carrying out suction filtration and washing on the precipitate, and drying to obtain tartrate radical and Ni²⁺A complex of (a);

(4) adding the obtained complex and sulfur powder into a ball milling tank according to the mass ratio of 10-100: 1, carrying out ball milling, and drying after the ball milling is finished, thus obtaining the sulfur-containing complex catalyst.

The invention prepares the sulfur-containing tartrate radical and Ni by a hydrothermal method²⁺Complex catalyst of (2), tartrate and Ni² ⁺The complex compound is directly cracked into simple substance nickel in the temperature rising process of preparing the spiral carbon nanofiber, and the catalytic effect can be achieved without hydrogen reduction. Wherein, the molar ratio of the potassium sodium tartrate to the nickel chloride is controlled to be 1: 0.95-1 in the step (1), so that the molar ratio of the potassium sodium tartrate is controlled to be slightly higher than that of the nickel chloride, divalent nickel ions can be fully complexed, and the cost can be reduced because the price of the nickel tartrate is obviously higher than that of the potassium sodium tartrate; meanwhile, the content of divalent nickel ions in the waste liquid is reduced, and the pollution to the environment is reduced. In the step (4), the obtained catalyst and sulfur powder are mixed and ball-milled, so that the catalytic effect of the catalyst can be improved, the prepared spiral carbon nanofibers are in a tightly wound twist shape, meanwhile, the sulfur powder can also be used as a growth promoter of the spiral carbon nanofibers to promote the growth of the spiral carbon nanofibers, and the drying condition can be 60-80 ℃ for vacuum drying for 12-16 hours. In the step (3), the mixed solution can be kept stand for 4-8 h, and the washed product can be dried in vacuum at 60-80 ℃ for 12-16 h.

Preferably, the potassium sodium tartrate and the nickel chloride are respectively dissolved at 40-60 ℃ and are ultrasonically dispersed for 5-10 min.

Preferably, the mixed solution after dropwise addition in the step (2) is stirred for 2-4 h. Thus, the solution can be mixed evenly, which is beneficial to tartaric acid radical and Ni in hydrothermal reaction²⁺And (3) complexing.

Preferably, the hydrothermal reaction temperature is 100-200 ℃, and the reaction time is 12-48 h. The potassium sodium tartrate and the nickel chloride can be fully dissolved in the solution through hydrothermal reaction, the complex is favorably formed under the condition of high pressure of 100-120 ℃, the catalyst yield can be improved by keeping the temperature at the high pressure of 100-120 ℃ for 12-48 hours, the residual impurity ions in the waste liquid are reduced, and the pollution to the environment is further reduced.

Preferably, the rotation speed during ball milling is 300-500 r/min, and the ball milling lasts for 2-4 h. Thus, the sulfur powder and the catalyst can be uniformly mixed, the particle size is smaller after ball milling, the catalytic effect of the catalyst is favorably improved, and the growth promoting effect of the sulfur powder can also be improved.

The method for preparing the spiral carbon nanofiber by using the catalyst provided by the invention comprises the following steps: and (2) placing the sulfur-containing complex catalyst prepared by the method on a graphite substrate, placing the graphite substrate in a tubular furnace, heating to 377.5-650 ℃ under protective gas flow, introducing acetylene for 30-60 min, and then cooling to room temperature to obtain the spiral carbon nanofibers.

According to the invention, the precursor is decomposed in the heat treatment process to obtain the nano catalyst particles with good dispersibility, so that the problem that the nano catalyst particles are easy to agglomerate is solved, the catalytic efficiency is improved, the uniform and high-purity spiral carbon nanofibers can be prepared at a lower temperature, and the sulfur powder in the spiral carbon nanofibers can be sublimated into gas at the reaction temperature, so that the growth of the spiral carbon nanofibers is promoted.

Wherein the protective gas flow can be argon gas flow or nitrogen gas flow, and the flow rate of the gas flow can be 100-200 mL/min. The protective gas can effectively protect the catalyst from being oxidized in the heating process and maintain the catalytic action of the catalyst

Preferably, the heating rate is 1-5 ℃/min. The temperature rise rate has direct influence on the particle diameter of the simple substance nickel obtained after the complex is decomposed, the particle diameter of the catalyst is related to the shape and the particle diameter of the spiral carbon nanofiber grown by catalysis, and the catalyst can be less in high-temperature decomposition impurities, small in particle diameter and better in catalysis effect at the temperature rise rate of 1-5 ℃/min.

Preferably, acetylene is introduced into the tube furnace at a rate of 80 to 300 mL/min. The utilization of acetylene can be maximized by controlling the flow of acetylene, the acetylene is not completely decomposed due to the introduction of excessive acetylene to cause waste, and the efficiency of the catalyst cannot be fully exerted due to the small flow of the acetylene, so that the proper flow of the acetylene needs to be selected.

Compared with the prior art, the invention has the following beneficial effects:

the invention adopts a hydrothermal method to prepare tartrate radical and Ni²⁺The complex is mixed with sulfur powder and ball milled, so that the catalytic efficiency of the catalyst is effectively improved, and the complex is used for preparing tartrate and Ni in the process of preparing the spiral nano carbon fiber²⁺The complex can be directly cracked into simple substance nickel to play a catalytic role, hydrogen is not needed to be introduced for reduction, and the preparation of the uniform and high-purity spiral carbon nanofibers at low temperature can be realized. The yield and the purity of the complex catalyst can be greatly improved by a hydrothermal method; the sulfur powder and the complex catalyst with smaller particle size can be obtained by ball milling, and the added sulfur powder can promote the growth of the spiral carbon nanofibers.

Drawings

FIG. 1 shows tartrate and Ni prepared in example 1²⁺TG profile of the complex;

FIG. 2 shows tartrate and Ni prepared in example 1²⁺XRD pattern of the complex;

FIG. 3 is an SEM image of the spiral filamentous nanocarbon prepared in example 1;

fig. 4 is a spiral filamentous nanocarbon prepared in example 1.

Detailed Description

The present invention will be further described with reference to the following specific examples.

Example 1:

first of all, tartrate containing sulphur and Ni²⁺Preparation of the complex of (1): weighing 0.05 mol of potassium tartrateRespectively dissolving sodium and 0.05 mol of nickel chloride in 100 mL of deionized water, fully stirring the two solutions at 60 ℃ until the solute is completely dissolved, performing ultrasonic treatment for 5min, dropwise adding a potassium sodium tartrate solution into the nickel chloride solution under the stirring condition, and after dropwise adding, continuously stirring for 2h under the unchanged condition to fully and uniformly mix the two solutions; ② transferring the mixed solution into a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 12h at 125 ℃. After the hydrothermal reaction is finished, standing the fully complexed turbid liquid for 4h, pouring out supernatant, washing with deionized water, carrying out suction filtration, repeating for 3 times, carrying out vacuum drying on the product at 60 ℃ for 12h, and grinding the product into powder to obtain tartrate and Ni²⁺A complex catalyst precursor of (3). Thirdly, adding the catalyst precursor and the sulfur powder into a ball milling tank according to the mass ratio of 80:1, carrying out ball milling for 2h at the rotating speed of 300r/min, fully mixing the sulfur powder and the precursor powder, carrying out vacuum drying at 60 ℃ for 12h after the ball milling is finished, and then grinding into powder to obtain the sulfur-containing complex catalyst.

Secondly, preparing the spiral nano carbon fiber: taking 0.2 g of the prepared sulfur-containing catalyst precursor on a graphite substrate, placing the graphite substrate in a tubular furnace, heating to 500 ℃ at a heating rate of 2 ℃/min under the protective atmosphere of argon (100 mL/min), introducing acetylene (120 mL/min) for 30 min under the heat preservation of 500 ℃, and continuing to reduce the temperature to room temperature under the protective atmosphere of argon (80 mL/min) after the acetylene introduction is finished, thereby obtaining the spiral carbon nanofiber product.

Example 2:

first of all, tartrate containing sulphur and Ni²⁺Preparation of the complex of (1): weighing 0.05 mol of sodium potassium tartrate and 0.0495 mol of nickel chloride, respectively dissolving the two solutions in 100 mL of deionized water, fully stirring the two solutions at 40 ℃ until the solute is completely dissolved, performing ultrasound treatment for 5min, dropwise adding the sodium potassium tartrate solution into the nickel chloride solution under the stirring condition, and after dropwise adding is completed, continuously stirring for 2h under the unchanged condition to fully and uniformly mix the two solutions; ② transferring the mixed solution into a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 24 h at 150 ℃. Standing the fully complexed turbid liquid for 4h after the hydrothermal reaction is finished, then pouring out supernatant liquid, washing with deionized water, performing suction filtration, repeating the process for 3 times, and then cooling the product at 60 DEG CVacuum drying for 12 hr, grinding into powder to obtain tartrate radical and Ni²⁺A complex catalyst precursor of (3). Thirdly, adding the catalyst precursor and the sulfur powder into a ball milling tank according to the mass ratio of 60:1, carrying out ball milling for 4 hours at the rotating speed of 400r/min, fully mixing the sulfur powder and the precursor powder, carrying out vacuum drying at 70 ℃ for 12 hours after the ball milling is finished, and then grinding into powder to obtain the sulfur-containing catalyst precursor powder.

Secondly, preparing the spiral nano carbon fiber: taking 0.3 g of the prepared catalyst precursor on a graphite substrate, placing the graphite substrate in a tube furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under the protective atmosphere of argon (120 mL/min), introducing acetylene (160 mL/min) for 60min under the heat preservation of 600 ℃, and continuing to reduce the temperature to room temperature under the protective atmosphere of argon (100 mL/min) after the acetylene introduction is finished, thereby obtaining the spiral carbon nanofiber product.

Example 3:

first of all, tartrate containing sulphur and Ni²⁺Preparation of the complex of (1): weighing 0.05 mol of sodium potassium tartrate and 0.049 mol of nickel chloride, respectively dissolving the two solutions in 100 mL of deionized water, fully stirring the two solutions at 50 ℃ until the solute is completely dissolved, performing ultrasound treatment for 5min, dropwise adding the sodium potassium tartrate solution into the nickel chloride solution under the stirring condition, and after dropwise adding is completed, continuously stirring for 2h under the unchanged condition to fully and uniformly mix the two solutions; ② transferring the mixed solution into a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 36 h at 175 ℃. After the hydrothermal reaction is finished, standing the fully complexed turbid liquid for 4h, pouring out supernatant, washing with deionized water, carrying out suction filtration, repeating for 3 times, carrying out vacuum drying on the product at 80 ℃ for 12h, and grinding the product into powder to obtain tartrate and Ni²⁺A complex catalyst precursor of (3). Thirdly, adding the catalyst precursor and the sulfur powder into a ball milling tank according to the mass ratio of 40:1, ball milling for 6 hours at the rotating speed of 500r/min to fully mix the sulfur powder and the precursor powder, and after the ball milling is finished, carrying out vacuum drying for 12 hours at the temperature of 80 ℃ and then grinding the mixture into powder to obtain the sulfur-containing catalyst precursor powder.

Preparing the spiral nano carbon fiber: taking 0.4 g of the prepared catalyst precursor on a graphite substrate, placing the graphite substrate in a tube furnace, heating to 650 ℃ at a heating rate of 4 ℃/min under the protective atmosphere of argon (100 mL/min), introducing acetylene (200 mL/min) for 50 min under the heat preservation of 650 ℃, and continuing to reduce the temperature to room temperature under the protective atmosphere of argon (100 mL/min) after the acetylene introduction is finished, thereby obtaining the spiral carbon nanofiber product.

FIG. 1 shows tartrate and Ni prepared in example 1²⁺TG diagram of complex, FIG. 2 tartrate and Ni prepared in example 1²⁺XRD pattern of the complex, as can be seen from FIG. 1, tartrate and Ni²⁺The complex is completely decomposed at the temperature higher than 377.5 ℃, and as can be seen from an XRD (X-ray diffraction) diagram of the decomposition product shown in figure 2, the decomposition product has a good matching degree between the phases of the crystal faces (111), (200) and (220) with the strongest diffraction and Ni (PDF 04-0850), which indicates that the decomposition product is a simple nickel substance and has good crystallinity. Meanwhile, no obvious impurity peak appears in the map, which indicates that no impurity exists in the decomposition product.

Fig. 3 is an SEM image of the spiral filamentous nanocarbon prepared in example 1, and fig. 4 is an original image of the spiral filamentous nanocarbon prepared in example 1, and it can be seen from fig. 3 and 4 that the spiral filamentous form is a tightly wound twist form, and spiral fibers are generally observed in the product, and no straight fibers are observed, and a good spiral degree is obtained. Meanwhile, the product is spread over the whole graphite substrate, and the yield is high

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims

1. A preparation method of spiral carbon nanofibers is characterized in that a prepared sulfur-containing complex catalyst is placed on a graphite substrate, the graphite substrate is placed in a tubular furnace, the temperature is raised to 377.5-650 ℃ under protective gas flow, acetylene is introduced for 30-60 min, and then the temperature is reduced to room temperature, so that the spiral carbon nanofibers are obtained; the heating rate is 1-5 ℃/min; introducing acetylene into the tubular furnace at a rate of 80-300 mL/min;

the sulfur-containing complex catalyst is prepared by adopting the following method:

(1) respectively preparing a potassium sodium tartrate solution and a nickel chloride solution, wherein the molar ratio of potassium sodium tartrate to nickel chloride is 1: 0.95-1, and dropwise adding the prepared potassium sodium tartrate solution into the nickel chloride solution under the condition of stirring; respectively dissolving sodium potassium tartrate and nickel chloride at 40-60 ℃, and ultrasonically dispersing for 5-10 min;

(2) after the dropwise adding is finished, transferring the mixed solution into a reaction kettle for hydrothermal reaction; the hydrothermal reaction temperature is 100-200 ℃, and the reaction time is 12-48 h;

2. The method for preparing a spiral carbon nanofiber as claimed in claim 1, wherein the mixed solution after dropping in step (2) is stirred for 2 to 4 hours.

3. The method for preparing spiral carbon nanofibers according to claim 1, wherein the rotation speed during ball milling is 300 to 500r/min, and the ball milling is carried out for 2 to 4 hours.