CN109607513B - A method for the controllable preparation of single-walled carbon nanotubes without sulfur impurities by a growth promoter - Google Patents

Abstract

The invention relates to the field of controllable preparation of high-quality single-walled carbon nanotubes with low catalyst content and no sulfur impurities, in particular to a method for controllably preparing single-walled carbon nanotubes without sulfur impurities by using a growth promoter. Selenophen is used as a precursor of a growth promoter, ferrocene is used as a precursor of a catalyst, the selenophen and the ferrocene are dissolved in a toluene solvent, the solution is converted into aerosol through an ultrasonic spray head, and the aerosol is carried into a high-temperature zone through a carrier gas to catalyze ethylene decomposition nucleation growth with high quality and high purity (I)_G/I_DUp to 180, catalyst content<4.5 wt.%), sulfur-free impurities. The invention uses selenium to replace sulfur as a growth promoter to realize the preparation of the high-quality single-walled carbon nanotube with low catalyst residue and no sulfur impurity; meanwhile, the tail gas for growing the carbon nano tube is prevented from containing hydrogen sulfide gas which is difficult to separate, the treatment and the cyclic utilization of the tail gas are convenient, and the macro preparation of the high-quality single-walled carbon nano tube with low catalyst content is realized.

Description

A method for the controllable preparation of single-walled carbon nanotubes without sulfur impurities by a growth promoter

technical field

The invention relates to the field of controllable preparation of high-quality, high-purity single-walled carbon nanotubes without sulfur impurities, in particular to a method for controllably preparing single-walled carbon nanotubes with low catalyst content by using a novel growth promoter selenium. The high-quality, high-purity, and sulfur-free single-walled carbon nanotubes also realize that the exhaust gas does not contain hydrogen sulfide gas, which is beneficial to exhaust gas treatment and recycling.

Background technique

Carbon nanotubes have chirality-dependent electrical conductivity, ballistic transport properties, excellent mechanical properties, excellent flexibility and low density, etc., so they are expected to be obtained in high-precision technical fields such as nanoelectronic devices, aviation, and aerospace. widely used. The preparation of carbon nanotubes is inseparable from the catalyst, but the catalyst remaining in the carbon nanotube samples will bring many negative effects. For example, it affects the intrinsic properties of carbon nanotubes such as thermal stability and chemical stability, metal nanoparticles are incompatible with organisms in biological applications, and catalyst residues affect light transmission properties in transparent conductive film applications. However, the general pickling method for removing catalysts in carbon nanotubes will destroy the structure of carbon nanotubes, affect their physical and chemical properties, and also bring about environmental pollution problems. Therefore, it is of great significance to control the preparation of carbon nanotubes with high quality and low catalyst residue.

Currently, floating catalyst chemical vapor deposition is one of the most effective methods to prepare high-quality, high-purity single-walled carbon nanotubes. In addition to the necessary catalysts, the preparation of carbon nanotubes by this method requires the assistance of growth promoters, otherwise the growth efficiency is extremely low, and the most commonly used growth promoter is sulfur (Document 1: A.H.Windle et al.Faraday Discuss., 2014, 173, 47-65; Literature 2: Lili Zhang et al. J. Phys. Chem. Lett. 2014, 5, 8, 1427-1432). The addition of sulfur growth promoters will lead to the presence of sulfur impurities in the prepared SWCNT samples, which will cause poisoning and deactivation of nanocatalysts supported on carbon nanotubes (Reference 3: Bartholomew, C.H. Applied Catalysis A: General , 2001, 212 (1-2), 17-60), or reduce the stability of the catalyst, and release hydrogen sulfide gas under acidic conditions. Therefore, the presence of sulfur impurities limits the application of carbon nanotubes in the field of catalysis. In addition, traditional sulfur growth promoters are easy to form hydrogen sulfide gas with hydrogen in the reaction atmosphere. If hydrogen sulfide gas is discharged into the atmosphere, it will pollute the environment. If the exhaust gas is recycled, the cost of removing hydrogen sulfide is high, and it is difficult to completely remove it. On the other hand, the current temperature for growing high-quality single-walled carbon nanotubes by the floating catalyst chemical vapor deposition method is generally higher than 1100 °C, which requires high material for the reaction furnace tube and increases the difficulty of large-scale preparation.

Therefore, the key problem that needs to be solved urgently at present is: how to realize the large-scale preparation of high-quality and high-purity single-walled carbon nanotubes without using sulfur.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for the controllable preparation of high-purity, high-quality, and sulfur-free single-walled carbon nanotubes with a novel growth promoter, that is, using selenium of the same family as sulfur as the growth promoter, so that selenium and iron are The high-temperature zone of the chemical vapor deposition furnace forms a low-melting iron-selenium compound, which efficiently catalyzes the growth of single-walled carbon nanotubes, thereby preparing high-purity, high-quality, and sulfur-free single-walled carbon nanotubes. The first technical problem solved by the present invention is to realize the efficient catalytic growth of carbon nanotubes with iron-selenium compounds, and to prepare high-quality single-walled carbon nanotubes with high purity and no sulfur impurities; the second technical problem solved by the present invention is to use The melting point (965° C.) of iron selenide is lower than the melting point (1194° C.) of iron sulfide, which is an intrinsic property, so that the floating catalyst chemical vapor deposition method can grow high-quality single-walled carbon nanotubes at a lower temperature. The third technical problem is to overcome the problem that the exhaust gas of single-walled carbon nanotubes prepared by the existing floating catalyst chemical vapor deposition method contains hydrogen sulfide gas which is difficult to remove.

The technical scheme of the present invention is:

A method for the controllable preparation of single-walled carbon nanotubes without sulfur impurities by a growth promoter, using selenium instead of traditional sulfur as a growth promoter, using selenophene as a growth promoter precursor, and using ferrocene as a catalyst precursor, The two are dissolved in a liquid-phase carbon source to form a solution, and the solution is converted into an aerosol by an ultrasonic atomization device, and then the carrier gas and the gas-phase carbon source are brought into the high-temperature zone of the chemical vapor deposition furnace. The selenium atoms are decomposed and form a low-melting iron-selenium compound with iron, which promotes the decomposition and nucleation of the carbon source to grow single-walled carbon nanotubes, thereby preparing high-quality single-walled carbon nanotubes with low catalyst content and no sulfur impurities.

The growth accelerator can controllably prepare single-walled carbon nanotubes without sulfur impurities, and a very small amount of selenophene is added: 0.01-0.09g selenophene/10g liquid-phase carbon source, so as to realize the efficient growth of carbon nanotubes.

The growth promoter can controllably prepare single-walled carbon nanotubes without sulfur impurities, and the content of catalyst impurities in the single-walled carbon nanotubes by thermogravimetric analysis is less than 4.5 wt. Negative effects caused by catalyst residues; the concentrated anti-oxidation temperature of the sample is higher than 780 ℃, and the _IG / _ID value of single-walled carbon nanotubes is greater than 150, indicating that the carbon nanotubes have high crystallinity.

The growth promoter can controllably prepare the single-walled carbon nanotubes without sulfur impurities, and the single-walled carbon nanotubes do not contain sulfur impurities, thereby broadening the practical application range of the single-walled carbon nanotubes.

The growth promoter is a method for controllably preparing single-walled carbon nanotubes without sulfur impurities, the diameters of the single-walled carbon nanotubes are distributed in a narrow range of 1.9-2.3 nm, and the average diameter is 2.1 nm.

The growth promoter can controllably prepare single-walled carbon nanotubes without sulfur impurities, and the tail gas does not contain hydrogen sulfide gas that is difficult to separate, which is beneficial to tail gas treatment and recycling.

The growth promoter can controllably prepare single-walled carbon nanotubes without sulfur impurities. temperature and reduce energy consumption.

The method for the controllable preparation of single-walled carbon nanotubes without sulfur impurities by the growth promoter, using a syringe pump and an ultrasonic atomization device to introduce a solution of a liquid-phase carbon source, a catalyst precursor and a growth promoter precursor into chemical vapor deposition Furnace, the mass ratio of liquid-phase carbon source, catalyst precursor and growth promoter precursor is (9～11g):(0.2～0.4g):(0.01～0.09g), with 0.1ml/hour～0.5ml/hour speed into the chemical vapor deposition furnace.

The growth promoter is used for the controllable preparation of single-walled carbon nanotubes without sulfur impurities, the liquid-phase carbon source is used as a catalyst precursor and a solvent for the growth promoter precursor at the same time, specifically toluene is used, the gas-phase carbon source is ethylene, and the carrier is ethylene. The gas is hydrogen, argon or nitrogen.

In the method for the controllable preparation of single-walled carbon nanotubes without sulfur impurities by the growth promoter, the flow rate of the carrier gas is 2000-8000 ml/min, and the flow rate of the gas-phase carbon source is 2-15 ml/min; Under the protective gas, the flow rate of the protective gas is 100-300 ml/min.

The design idea of the present invention is:

The present invention proposes for the first time that selenium is used as a growth promoter to prepare large-scale single-walled carbon nanotubes with high quality, high purity and no sulfur impurities. provide a new method of preparation. Using selenium-substituted sulfur as a growth promoter for single-walled carbon nanotubes grown by floating catalyst chemical vapor deposition, solving the problem that sulfur impurities remain in carbon nanotube samples and the exhaust gas contains hydrogen sulfide gas that is difficult to separate, and floating catalyst chemical vapor deposition It is difficult to grow high-quality single-walled carbon nanotubes at low temperature by using these two scientific and technical problems. Furthermore, a method for macro-scale preparation of clean, non-polluting, high-purity, high-quality single-walled carbon nanotubes is proposed.

The advantages and beneficial effects of the present invention are:

1. The present invention uses selenium instead of sulfur as a growth promoter, realizes the macro-production of single-wall carbon nanotubes without sulfur impurities for the first time, and solves the problem that sulfur impurities usually exist in single-wall carbon nanotube samples prepared by floating catalyst chemical vapor deposition method. A key issue, thereby broadening the application scope of single-walled carbon nanotubes in catalysis and other fields.

2. The method of the present invention avoids the problem of difficult to separate and highly toxic hydrogen sulfide gas in the tail gas, and is beneficial to the treatment and recycling of the tail gas.

3. The method of the present invention reduces the suitable temperature for growing single-walled carbon nanotubes by the floating catalyst chemical vapor deposition method to 900-1100°C, greatly reduces the energy consumption in the preparation process of single-walled carbon nanotubes, and reduces the floating effect of single-walled carbon nanotubes. The large-scale preparation of catalysts by chemical vapor deposition is of great significance.

4. The present invention achieves the controllable preparation of high-quality, high-purity single-walled carbon nanotubes by using selenium as a growth promoter, and avoids a series of problems such as sulfur impurities and hydrogen sulfide emissions caused by the use of sulfur growth promoters. , which is of great significance to promote and popularize the practical application of single-walled carbon nanotubes.

Description of drawings

Figure 1. Schematic diagram of the preparation system for single-walled carbon nanotubes. In the figure, 1 argon bottle; 2 ethylene bottle; 3 hydrogen bottle; 4 chemical vapor deposition furnace; 5 ultrasonic nozzle; 6 precision injection pump.

Figure 2.1# Sample Raman spectrum characterization results: (a), (b), (c) are the Raman spectral breathing modes excited by 532nm, 633nm, 785nm lasers respectively; (d) are G mode and D mode (633nm laser ), I _G / _ID =180 is obtained by calculation; in the figure, the abscissa Raman Shift is the Raman shift (cm ⁻¹ ), and the ordinate Intensity is the relative intensity (au).

Fig. 3. SEM photos of sample #1: (a) and (b) are the high and low magnification SEM photos of the sample, respectively.

Figure 4.1# Sample TEM characterization results: (a) and (b) are the high and low magnification TEM photos of the sample, respectively; (c) is the result of the diameter distribution of 100 carbon nanotubes.

Figure 5. The results of thermogravimetric analysis of the 1# sample. In the figure, the right ordinate DSC represents the power flow per gram of sample (mW/mg).

Figure 6. (a) and (b) are the X-ray electron spectroscopy characterization results of 1# and 2# samples, respectively.

Detailed ways

As shown in Figure 1, the preparation system of single-walled carbon nanotubes includes: argon cylinder 1, ethylene cylinder 2, hydrogen cylinder 3, chemical vapor deposition furnace 4, ultrasonic nozzle 5, precision syringe pump 6, etc. The specific structure is as follows: The gas cylinder 1, ethylene bottle 2, and hydrogen cylinder 3 are respectively equipped with argon, ethylene, and hydrogen. The outlets of the argon cylinder 1, ethylene cylinder 2, and hydrogen cylinder 3 are collected to the ultrasonic nozzle 5 through pipelines. The output pipeline is collected to the ultrasonic nozzle 5, and the outlet of the ultrasonic nozzle 5 is communicated with the chemical vapor deposition furnace 4. After the toluene, selenophene, and ferrocene in the precision injection pump 6 are mixed with hydrogen and ethylene, the ultrasonic nozzle 5 is sprayed to the chemical vapor deposition furnace 4. In the vapor deposition furnace 4, single-walled carbon nanotubes are grown.

In the specific implementation process, the present invention adopts the injection floating catalyst chemical vapor deposition method to control the preparation of single-wall carbon nanotubes with high quality and low catalyst content. Using volatile metal organic compound ferrocene as catalyst precursor, selenium-containing organic selenophene as growth promoter precursor, hydrocarbons ethylene and toluene as carbon source, and hydrogen as carrier gas, growth at 900-1100 ℃ Single-walled carbon nanotubes.

The specific steps of this method are as follows:

(1) Under argon protection, first raise the temperature of the chemical vapor deposition furnace to the carbon tube growth temperature (such as 1100 ° C), connect the syringe containing the toluene solution to the ultrasonic atomization device (ultrasonic nozzle), and then introduce the carrier gas Hydrogen and carbon source ethylene;

(2) After the solution supplied by the syringe pump (containing auxiliary carbon source toluene, catalyst precursor ferrocene and growth promoter precursor selenophene) is atomized into aerosol, it enters the high temperature zone under the carrier gas; ferrocene and Selenphene is cracked to form catalyst particles. Under the action of high temperature and catalyst, ethylene and toluene decompose carbon atoms and nucleate and grow single-walled carbon nanotubes on the catalyst particles;

(3) The generated carbon nanotubes flow to the tail end of the reactor with the carrier gas, and are finally collected by the porous filter membrane placed at the tail end to form a carbon nanotube film.

(4) At the end of the preparation, the chemical vapor deposition furnace is cooled down naturally, the supply of solution, hydrogen and ethylene is stopped, and argon gas is introduced as a protective gas.

Wherein, the argon flow before and after the preparation is 200 ml/min, the hydrogen flow in the preparation is 2000～8000 ml/min, the ethylene flow is 2～15 ml/min, and the supply speed of the solution is 0.1～0.5 ml/hour, The solution formula is toluene:ferrocene:selenophene=(9-11g):(0.2-0.4g):(0.01-0.09g).

In the product obtained by the method of the present invention, the single-walled carbon nanotubes are characterized by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and other characterization methods to analyze their structural characteristics.

Hereinafter, the present invention will be further described in detail through the embodiments and the accompanying drawings.

Example 1.

In this example, under the protection of argon at 200 ml/min, the temperature of the chemical vapor deposition furnace was first raised to 1100 °C, and then 5000 ml/min of hydrogen and 5 ml/min of ethylene were introduced, containing catalyst precursor two The toluene solution of ferrocene and the growth promoter precursor selenophene was injected into the ultrasonic nozzle at a rate of 0.2 ml/hour, and the grown carbon nanotubes flowed to the tail of the tube with the gas flow, and finally formed carbon nanotubes on the porous filter placed at the tail. tube film.

Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were performed on the single-walled carbon nanotube thin film samples prepared above (marked as 1#).

As shown in Fig. 2(a, b, c), the Raman spectra of the SWNT thin films have concentrated breathing mode peaks, indicating that the diameter distribution of SWNTs is narrow. As shown in Figure 2(d), SWCNTs have extremely high strength _G mode and extremely low strength _D mode ( _IG /ID is 180, and the _IG /ID reported in the literature is usually less than 50), This shows that the crystallinity of the single-walled carbon nanotubes in the film is very high; as shown in Figure 3, the surface of the carbon nanotubes is found to be very clean by scanning electron microscopy, and there are few catalyst residues. As shown in Fig. 4(a,b), the high-magnification TEM images show that the obtained material is single-walled carbon nanotubes and in the shape of tube bundles, and the low-magnification images show that there is little catalyst attached to the carbon nanotubes. As shown in Figure 4(c), by counting the diameters of 100 single-walled carbon nanotubes, it is found that the diameters are concentrated between 1.9 and 2.3 nm, and the average diameter is about 2.1 nm. As shown in Figure 5, thermogravimetric analysis shows that the concentrated anti-oxidation temperature of this sample is about 780 °C, and the residual amount of catalyst obtained by calculation is less than 4.5%, indicating that the carbon nanotubes have good crystallinity and high purity. As shown in Fig. 6(a), no peak of sulfur was observed by X-ray photoelectron spectroscopy (XPS) analysis, indicating that the carbon nanotube samples did not contain sulfur impurities.

Example 2.

In this example, under the protection of 200 ml/min of argon gas, the temperature of the chemical vapor deposition furnace was first raised to 900 ° C, and then 2000 ml/min of hydrogen and 15 ml/min of ethylene were introduced, containing catalyst precursor two The toluene solution of ferrocene and the growth promoter precursor selenophene was injected into the ultrasonic nozzle at a speed of 0.5 ml/hour, and the grown carbon nanotubes flowed to the tail of the tube with the gas flow, and finally formed carbon nanotubes on the porous filter placed at the tail end. tube film.

The sharp peak shape of the breathing mode of the Raman spectrum of the single-walled carbon nanotube film indicates that the diameter distribution of the single-walled carbon nanotube is narrow, and the _IG / _ID is 170, indicating that the crystallinity of the single-walled carbon nanotube in the film is very high; scan Electron microscope observation found that the surface of the carbon nanotubes was very clean, and there was very little catalyst residue. High-magnification TEM images show that the resulting material is single-walled carbon nanotubes and in the form of tube bundles, and low-magnification images show that few catalysts are attached to the carbon nanotubes. By counting the diameters of 100 single-walled carbon nanotubes, it is found that the diameters are concentrated between 1.8 and 2.2 nm, and the average diameter is about 2.0 nm. Thermogravimetric analysis showed that the concentrated anti-oxidation temperature of the sample was about 760°C, and the residual amount of catalyst was less than 4.2 wt.%, indicating that the carbon nanotubes had high crystallinity and high purity. As shown in Figure 6(a), no sulfur peak was observed in X-ray photoelectron spectroscopy (XPS) analysis, indicating that the carbon nanotube samples did not contain sulfur impurities.

Comparative example.

In this comparative example, under the protection of argon gas of 200 ml/min, the temperature of the chemical vapor deposition furnace was first raised to 1100 ° C, and then 5000 ml/min of hydrogen and 5 ml/min of ethylene were introduced. The selenophene was replaced with an equivalent amount of thiophene and dissolved in the toluene solution, and then the toluene solution containing ferrocene and thiophene was injected into the ultrasonic nozzle at a speed of 0.2 ml/hour. The grown carbon nanotubes flow to the tail of the tube with the air flow, and finally a carbon nanotube film is formed on the porous filter membrane placed at the tail end, which is denoted as 2# for the above single-walled carbon nanotube film sample.

The peak shape of the Raman spectrum of the single-walled carbon nanotube film is sharp, indicating that the diameter distribution of the single-walled carbon nanotube is narrow, and the _IG / _ID is 170, indicating that the crystallinity of the single-walled carbon nanotube in the film is very high; Scanning electron microscope observation showed that the surface of carbon nanotubes was very clean, and there was very little catalyst residue. High-magnification TEM images show that the resulting material is single-walled carbon nanotubes and in the form of tube bundles, and low-magnification images show that few catalysts are attached to the carbon nanotubes. By counting the diameters of 100 single-walled carbon nanotubes, it is found that the diameters are concentrated between 1.7 and 2.3 nm, and the average diameter is about 2.0 nm. Thermogravimetric analysis showed that the concentrated anti-oxidation temperature of the sample was about 780°C, and the residual amount of catalyst was less than 5.0 wt.%, indicating that the carbon nanotubes had high crystallinity and high purity. As shown in Fig. 6(b), in the X-ray photoelectron spectroscopy analysis, the 2p peak of sulfur was detected, indicating that sulfur impurities are contained in the carbon nanotubes.

The results of the examples and comparative examples show that, by selecting selenium, which is the same family as sulfur, as the growth promoter, the macro growth of high-quality, high-purity single-walled carbon nanotubes at a lower temperature (900-1100° C.) can be achieved. There is no residual sulfur impurity in the tube sample, and no difficult-to-remove and highly toxic hydrogen sulfide gas in the chemical vapor deposition tail gas, which is of great significance for the large-scale preparation of single-walled carbon nanotubes by floating catalyst chemical vapor deposition and its application.

Claims (7)

1. A method for preparing a single-walled carbon nanotube without sulfur impurities by using a growth promoter in a controllable manner is characterized in that selenium is used for replacing traditional sulfur as the growth promoter, selenophene is used as a precursor of the growth promoter, ferrocene is used as a precursor of a catalyst, the selenophene and the ferrocene are dissolved in a liquid-phase carbon source to form a solution, the solution is converted into aerosol through an ultrasonic atomization device, carrier gas and a gas-phase carbon source are brought into a high-temperature area of a chemical vapor deposition furnace together, selenium atoms are separated by the selenophene at the high-temperature area, a low-melting-point iron selenium compound is formed by the selenophene and iron, the carbon source is promoted to be decomposed to form nuclei for growing the single-walled carbon nanotube, and thus the high-quality single-walled carbon nanotube with low catalyst content and without sulfur impurities is prepared;

addition of very small amounts of selenophene: 0.01-0.09 g of selenophene/10 g of liquid-phase carbon source to realize the high-efficiency growth of the carbon nano tube;

the diameter of the single-walled carbon nanotube is distributed in a narrow range of 1.9-2.3 nm, and the average diameter is 2.1 nm;

the growth temperature of the single-walled carbon nanotube is 900-1100 ℃, the temperature required by the floating catalyst chemical vapor deposition method for growing the single-walled carbon nanotube is reduced, and the energy consumption is reduced.

2. The method for controllably preparing the single-walled carbon nanotube without the sulfur impurity by the growth promoter according to claim 1, wherein the content of the catalyst impurity in the single-walled carbon nanotube is less than 4.5 wt.% by thermogravimetric analysis, so that the negative effect caused by the catalyst residue in the practical application of the single-walled carbon nanotube is reduced; the concentrated oxidation resistance temperature of the sample is higher than 780 ℃, and the temperature of the single-walled carbon nano tube is I_G/I_DValues greater than 150 indicate high crystallinity of the carbon nanotubes.

3. The method for controllably preparing single-walled carbon nanotubes free of sulfur impurities with the growth promoter as claimed in claim 1, wherein the single-walled carbon nanotubes are free of sulfur impurities, thereby widening the practical application range of the single-walled carbon nanotubes.

4. The method for controllably preparing the single-walled carbon nanotube free of sulfur impurities by using the growth promoter as claimed in claim 1, wherein the tail gas does not contain hydrogen sulfide gas which is difficult to separate, thereby facilitating the treatment and recycling of the tail gas.

5. The method for preparing the single-walled carbon nanotube without sulfur impurities by controlling the growth promoter according to claim 1, wherein the solution of the liquid-phase carbon source, the catalyst precursor and the growth promoter precursor is introduced into the chemical vapor deposition furnace by using an injection pump and an ultrasonic atomization device, and the liquid-phase carbon source, the catalyst precursor and the growth promoter precursor are injected into the chemical vapor deposition furnace at a rate of 0.1 ml/h to 0.5 ml/h, wherein the mass ratio of the liquid-phase carbon source, the catalyst precursor and the growth promoter precursor is (9-11 g): 0.2-0.4 g): 0.01-0.09 g.

6. The method for preparing single-walled carbon nanotubes free of sulfur impurities under control of growth promoter as claimed in claim 1, wherein liquid carbon source is used as solvent for both catalyst precursor and growth promoter precursor, specifically toluene, gas carbon source is ethylene, and carrier gas is hydrogen, argon or nitrogen.

7. The method for controllably preparing the single-walled carbon nanotube free of sulfur impurities by using the growth promoter as claimed in claim 1, wherein the flow rate of the carrier gas is 2000-8000 ml/min, and the flow rate of the gas-phase carbon source is 2-15 ml/min; the chemical vapor deposition is carried out under the protective gas, and the flow rate of the protective gas is 100-300 ml/min.

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