Method and device for preparing single-walled carbon nanotubes by converting acetic acid industrial waste liquid

Abstract

The application discloses a method and device for preparing single-walled carbon nanotubes from acetic acid industrial waste liquid. The method comprises the following steps: distilling or rectifying low-ash acetic acid industrial waste liquid to obtain low-boiling fraction and tower bottom heavy component; reacting the low-boiling fraction with alkaline substance to saponify low ester into low alcohol and carboxylic acid salt, and to neutralize low carboxylic acid into carboxylic acid salt; distilling or rectifying the volatile fraction containing low alcohol, acetone and water; mixing the volatile fraction after drying or moisture adjustment with catalyst precursor, and sending the mixture into high-temperature reaction zone under the carrying of carrier gas to prepare single-walled carbon nanotubes through floating catalytic chemical vapor deposition. The obtained product has the RBM characteristic peak of single-walled carbon nanotubes in Raman spectrum. The tower bottom heavy component can be combusted, pyrolyzed or gasified to realize heat recovery or gaseous carbon source utilization. The application realizes materialization high-value utilization of light components of acetic acid industrial waste liquid and energy utilization of heavy components.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, specifically relating to a method and apparatus for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial wastewater. Background Technology

[0002] Organic chemical production involves the preparation, separation, and recovery of various organic chemicals, including alcohols, acids, esters, ketones, and aromatics. A certain amount of organic waste liquid is inevitably generated during reaction conversion, distillation separation, solvent recovery, and equipment cleaning. This type of waste liquid is typically characterized by complex composition, high volatility, a high proportion of oxygen-containing organic matter, and significant differences in calorific value and acid value. For acetic acid, acetate esters, and related carbonylation, esterification, and solvent recovery processes, the byproducts or separated waste liquid may contain multiple components such as lower alcohols, lower esters, formic acid, acetic acid, acetone, toluene, and high-boiling-point organic compounds. Treating this type of waste liquid as hazardous waste for end-of-pipe disposal is not only costly but also makes it difficult to fully utilize its carbon and calorific value components.

[0003] Carbon nanotubes, especially single-walled carbon nanotubes, are one-dimensional carbon nanomaterials formed by rolling up monolayer graphene sheets. They possess high aspect ratio, high electrical conductivity, high specific surface area, excellent mechanical properties, and good chemical stability, showing great potential for applications in conductive additives, transparent conductive films, composite materials, energy storage devices, sensors, and electronic devices. Therefore, converting waste carbon source components in industrial organic wastewater into single-walled carbon nanotubes can not only increase the added value of wastewater resource recovery but also help reduce the dependence on commercial carbon sources for single-walled carbon nanotube preparation.

[0004] Patent document US20190375639A1 discloses a method for preparing carbon nanotubes by converting waste plastics into carbon nanotubes: polymers, plastics and other carbon-containing wastes are mixed with metal catalyst precursors and solvents and then injected into a chemical vapor deposition reactor to prepare carbon nanotubes.

[0005] Patent document with publication number CN111533110A discloses a method for preparing nitrogen, sulfur, and phosphorus co-doped porous carbon nanotubes: using organic dye waste liquid, phosphorus-containing organic acid is added while stirring, the flocculent precipitate obtained after filtering the reaction solution is freeze-dried, and the precursor material is annealed to obtain nitrogen, sulfur, and phosphorus co-doped porous carbon nanotubes.

[0006] The aforementioned existing technologies have all studied the conversion of organic waste liquid into carbon nanotubes, but the raw materials used are mainly concentrated in systems such as waste plastics, waste oil, and dye waste liquid. Therefore, it is of great significance to develop a fractional conversion method suitable for the preparation of single-walled carbon nanotubes from acetic acid industrial waste liquid. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid. This method directionally converts the carbon-containing organic components in acetic acid industrial waste liquid into high-value-added single-walled carbon nanotubes.

[0008] This invention provides a method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid, comprising the following steps: (1) The low-ash acetic acid industrial waste liquid is subjected to a first rectification or distillation to obtain a low-boiling-point fraction and a heavy component in the bottom of the column, wherein the low-boiling-point fraction includes lower alcohols, acetone, lower esters and lower carboxylic acids; (2) Add an alkaline substance to the low-boiling-point fraction in step (1) to carry out a saponification / neutralization reaction to obtain a saponification / neutralization reaction solution, wherein the lower ester reacts with the alkaline substance to undergo a saponification reaction, and the lower carboxylic acid reacts with the alkaline substance to undergo a neutralization reaction. The temperature of the saponification / neutralization reaction is 20-90℃, the reaction time is 0.1-6 h, and the molar amount of the alkaline substance added in the saponification / neutralization reaction is 0.8-20 times the molar amount of the lower ester and lower carboxylic acid in the low-boiling-point fraction. (3) The saponification / neutralization reaction solution in step (2) is subjected to a second distillation or distillation to obtain a volatile fraction containing lower alcohols, acetone and water; (4) The volatile fraction in step (3) is dried to obtain a liquid carbon source, wherein the water content of the liquid carbon source is 0-5 wt%; (5) The liquid carbon source, carrier gas and catalyst precursor in step (4) are mixed to obtain a mixed stream. The mixed stream is reacted at 700-1300℃ to obtain single-walled carbon nanotube aerosol. The single-walled carbon nanotube aerosol is filtered and collected to obtain crude single-walled carbon nanotube product.

[0009] This invention utilizes a saponification / neutralization reaction to react lower esters and lower carboxylic acids in low-boiling-point fractions to form lower alcohols, carboxylates, and water. This avoids the formation of coke or tar from the retention of lower esters and lower carboxylic acids, which would affect the subsequent formation of single-walled carbon nanotubes. Furthermore, by controlling the temperature and time of the saponification / neutralization reaction, as well as the amount of alkaline substance added, this invention minimizes the side reactions between alkaline substances and acetone. The products of these side reactions can severely affect the formation of single-walled carbon nanotubes.

[0010] This invention controls the water content of the liquid carbon source to avoid excessive water content, which would cause catalyst precipitation in the mixed stream. The precipitated catalyst would cause fluctuations in the reaction, easily generate multi-walled carbon nanotubes, and inhibit the synthesis of single-walled carbon nanotubes.

[0011] Preferably, the ash content of the low-ash acetic acid industrial waste liquid is not higher than 5.0 wt%.

[0012] More preferably, the ash content of the low-ash acetic acid industrial waste liquid is not higher than 0.5 wt%.

[0013] Preferably, the top temperature of the first distillation or first rectification column is 45-80°C, and the bottom temperature is 100-190°C.

[0014] More preferably, the top temperature of the first distillation or first rectification column is 50-70°C, and the bottom temperature is 140-180°C.

[0015] Furthermore, the reboiler component contains toluene and / or high-boiling-point organic compounds.

[0016] Preferably, the lower alcohol comprises one or more of methanol, ethanol, n-propanol, and isopropanol; The lower esters mentioned include one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, and propyl acetate; The lower carboxylic acids mentioned above include formic acid and / or acetic acid.

[0017] Preferably, the apparent pH of the low-boiling fraction before the saponification / neutralization reaction is 1-3, and the pH of the volatile fraction or other aqueous phase obtained after saponification / neutralization is 6-7.

[0018] Preferably, the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and potassium carbonate.

[0019] More preferably, the alkaline substance includes sodium hydroxide and / or potassium hydroxide. Sodium hydroxide and potassium hydroxide have high alkalinity and good solubility, which can promote the saponification of lower esters and the neutralization of free carboxylic acids under milder conditions, thereby improving the conversion efficiency of ester components. At the same time, compared with calcium hydroxide or carbonates, they are less likely to introduce solid precipitates or gaseous byproducts, which helps to reduce problems such as pipeline blockage, separation scaling, and impurities carried by subsequent volatile fractions.

[0020] Preferably, the amount of alkaline substance added in the saponification / neutralization reaction is 1.0-1.2 times the molar amount required for the theoretical reaction of lower esters and lower carboxylic acids in the low-boiling-point fraction, thereby retaining acetone in the low-boiling-point fraction and inhibiting its side reactions during alkaline treatment. Using an alkaline substance in a slightly higher amount than the theoretical amount ensures the full conversion of lower esters and free carboxylic acids, while avoiding side reactions such as condensation of acetone caused by excessive strong alkali.

[0021] Preferably, the saponification / neutralization reaction is carried out at a temperature of 30-60°C for 0.5-3 h to suppress side reactions of acetone and retain acetone as an effective component of the liquid carbon source. This temperature and time range ensures sufficient saponification of lower esters and complete neutralization of free carboxylic acids while avoiding side reactions such as alkali-catalyzed condensation of acetone caused by excessively high reaction temperatures or excessively long residence times. This is beneficial for improving the compositional stability of the alcohol / acetone type liquid carbon source and reducing byproducts and residual impurities in the second separation process.

[0022] Preferably, the GC-MS area normalized content of one or more of methyl acetate, ethyl acetate and acetic acid in the volatile fraction is less than 0.1 area.

[0023] Preferably, the mixed stream further contains a sulfur source promoter, the catalyst precursor includes ferrocene, and the sulfur source promoter is one or more of thiophene, carbon disulfide, organic thiol, and sulfur powder.

[0024] Preferably, the water content of the liquid carbon source is 0-1 wt%. This range ensures the solubility stability of ferrocene in alcohol / acetone-type liquid carbon sources, avoids the precipitation of ferrocene during storage and continuous feeding, and reduces the interference of excessive water vapor on iron-based catalyst particles and carbon species, thereby facilitating the selective growth of single-walled carbon nanotubes.

[0025] Preferably, the carrier gas comprises one or more inert gases selected from nitrogen, argon, and helium, and is mixed with 0-10 vol% hydrogen. More preferably, the carrier gas is nitrogen mixed with 0-10 vol% hydrogen.

[0026] Preferably, the temperature of the high-temperature reaction zone is 850-1100℃.

[0027] Preferably, the single-walled carbon nanotubes exhibit RBM characteristic peaks in the Raman spectrum excited by a 532 nm laser, and the I calculated based on the peak area... D / I G Less than 0.1.

[0028] Preferably, the crude single-walled carbon nanotube product is acid-washed, washed and dried to obtain purified single-walled carbon nanotubes, wherein the ash content of the purified single-walled carbon nanotubes is less than 1 wt.

[0029] Preferably, the recombinant components in the tower bottom undergo thermal conversion treatment to obtain one or more of the following: heat, pyrolysis gas, and gasification gas. The thermal conversion treatment is one or more of the following: combustion, pyrolysis, oxygen-deficient gasification, steam gasification, and carbon dioxide gasification.

[0030] Preferably, the pyrolysis gas or gasification gas contains H2 and CO, with a total integral greater than 70 vol.

[0031] More preferably, the total volume fraction of the pyrolysis gas or gasification gas is greater than 80 vol%.

[0032] Preferably, the pyrolysis gas or gasification gas, after being detarted, condensed, dried or filtered, is used as fuel gas, reducing gas, syngas product, carbon source or auxiliary gas for the preparation of single-walled carbon nanotubes; Preferably, the heat generated by the combustion or thermal conversion of the heavy components in the column bottom is used to heat the first distillation, the second distillation, the saponification / neutralization reaction, the raw material preheating, the liquid carbon source preheating, or the floating catalytic chemical vapor deposition reactor.

[0033] The heavy component obtained in the first separation step of this invention has high calorific value, low ash content, and low sulfur content. This heavy component can be used for combustion heating, or it can be oxidized in anoxic conditions to produce gas rich in H2 and CO, enabling energy recovery, syngas product preparation, or optional utilization as a gaseous carbon source from single-walled carbon nanotubes.

[0034] Another aspect of the present invention provides an apparatus for preparing single-walled carbon nanotubes by branching conversion of acetic acid industrial waste liquid, comprising: The first separation tower is used to perform a first rectification or distillation on the obtained low-ash acetic acid industrial waste liquid to obtain a low-boiling-point fraction and a heavy component in the bottom of the tower. The low-boiling-point fraction includes lower alcohols, acetone, lower esters and lower carboxylic acids. A saponification / neutralization reactor, connected to a first separation tower, is used to saponify / neutralize received low-boiling-point fractions and alkaline substances to obtain a saponification / neutralization reaction solution. The lower esters undergo saponification with the alkaline substances, and the lower carboxylic acids undergo neutralization with the alkaline substances. The saponification / neutralization reaction is carried out at a temperature of 20-90°C for 0.1-6 h. The molar amount of alkaline substances added in the saponification / neutralization reaction is 0.8-20 times the molar amount of the lower esters and lower carboxylic acids in the low-boiling-point fraction. The second separation tower, connected to the saponification / neutralization reactor, is used to perform a second rectification or distillation on the received saponification / neutralization reaction liquid to obtain a volatile fraction containing lower alcohols, acetone and water. A dryer, connected to a second separation tower, is used to dry the received volatile fraction to obtain a liquid carbon source, wherein the water content of the liquid carbon source is 0-5 wt%. A mixing / carrier gas carrying unit, which is connected to a dryer, is used to mix a liquid carbon source with a catalyst precursor to obtain a mixed stream; A reaction collector, connected to a mixing / carrier gas carrying unit, is used to react the mixed stream at 700-1300°C to obtain single-walled carbon nanotube aerosols, and to filter and collect the single-walled carbon nanotube aerosols to obtain crude single-walled carbon nanotube products.

[0035] Preferably, the reaction collector includes a floating catalytic chemical vapor deposition reactor and a filtration / collection unit; The floating catalytic chemical vapor deposition reactor is connected to a mixing / carrier gas carrying unit, which is used to react the mixed flow at 700-1300℃ to obtain single-walled carbon nanotube aerosols. A filtration / collection unit, connected to a floating catalytic chemical vapor deposition reactor, is used to filter and collect the obtained single-walled carbon nanotube aerosol to obtain crude single-walled carbon nanotube product.

[0036] Preferably, the apparatus for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid further includes a heavy component thermal conversion unit, which is connected to the first separation tower and is used to perform thermal conversion treatment on the obtained heavy components in the tower bottom to obtain heat, pyrolysis gas, gasification gas or one or more of the following: the thermal conversion treatment is combustion, pyrolysis, oxygen-deficient gasification, water vapor gasification or carbon dioxide gasification or one or more of the following. Preferably, the apparatus for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid further includes a catalyst precursor / auxiliary raw material tank, which is connected to a mixing / carrier gas carrying unit for mixing the catalyst precursor and / or sulfur source auxiliary agent to prepare a high-concentration mother liquor.

[0037] The principle of this invention for preparing single-walled carbon nanotubes using the fractional conversion of acetic acid industrial waste liquid is as follows: This invention, based on the differences in boiling point, reactivity, and high-temperature catalytic cracking behavior of various components in acetic acid industrial wastewater, employs a route of "distillation and fractionation - saponification / neutralization and conditioning - re-separation - floating catalytic chemical vapor deposition" to convert low-boiling-point components in acetic acid industrial wastewater into liquid carbon sources suitable for preparing single-walled carbon nanotubes, while utilizing high-boiling-point heavy components through thermal conversion. The technical principles of this invention are further explained below, but this explanation should not be construed as limiting the scope of protection of this invention.

[0038] Acetic acid industrial waste typically contains various components such as lower alcohols, lower esters, formic acid, acetic acid, acetone, toluene, and high-boiling-point organic compounds. If the entire waste liquid is directly introduced into the high-temperature chemical vapor deposition (CVD) reaction zone, lower esters, free carboxylic acids, and heavy organic compounds are prone to condensation, cracking, polymerization, or incomplete carbonization, leading to the formation of tar, coke, and amorphous carbon. This also affects the formation and catalytic activity of iron-based catalytic particles, hindering the selective growth of single-walled carbon nanotubes. Therefore, this invention first separates the acetic acid industrial waste liquid into a low-boiling-point fraction and a heavy fraction in the bottom of the distillation column through distillation or rectification. This avoids direct coking of all components in the furnace and provides a basis for the differentiated utilization of different fractions.

[0039] In the low-boiling-point fraction obtained from the first separation, lower alcohols and acetone exhibit good volatility and carbon-donating capacity, making them suitable as liquid carbon source components for floating catalytic chemical vapor deposition. While lower esters and free carboxylic acids also possess volatility, they are prone to coking, tar formation, or amorphous carbon under high-temperature reaction conditions. The inventors' experiments show that mixing ethanol and acetone can still generate single-walled carbon nanotubes with RBM characteristic peaks, but mixing ethanol with ethyl acetate or acetic acid makes it difficult to generate single-walled carbon nanotubes and produces significant coking or tar formation. Therefore, for low-boiling-point fractions of acetic acid industrial wastewater, their suitability as effective carbon sources cannot be determined solely by boiling point or volatility; further reaction conditioning of the ester components is also necessary.

[0040] Therefore, in this invention, an alkaline substance is added for saponification and neutralization of the low-boiling-point fraction before it enters the single-walled carbon nanotube reactor. The lower esters are saponified to produce lower alcohols and carboxylates, with the following general reaction formula: in, Indicates a lower ester. Indicates an alkaline substance. Indicates carboxylate salt, This refers to lower alcohols. Through this reaction, lower esters, which are originally unfavorable for the growth of single-walled carbon nanotubes, are converted into non-volatile carboxylates and lower alcohols that can serve as carbon sources, thus realizing the conversion and utilization of ester components.

[0041] Meanwhile, free carboxylic acids such as formic acid and acetic acid in the low-boiling-point fraction undergo a neutralization reaction with alkaline substances to produce non-volatile carboxylates and water. The general reaction formula is: Through neutralization, free acids are converted into salts such as formate and acetate, which are difficult to be carried out with volatile fractions. This reduces the content of acidic components in the subsequent liquid carbon source and reduces the risk of tar, amorphous carbon, or catalyst deactivation caused by acidic components entering the high-temperature reaction zone.

[0042] The reaction liquid after saponification and neutralization undergoes a second distillation or rectification process to separate volatile components such as lower alcohols, acetone, and a small amount of water from the carboxylate residue. The carboxylate mainly remains in the bottoms or salt phase residue, while methanol, ethanol, propanol, acetone, and a small amount of water enter the volatile fraction. This step significantly reduces undesirable components such as ethyl acetate and acetic acid in the volatile fraction, thus transforming the originally complex "alcohol-ester-acid-ketone" mixed light fraction into a liquid carbon source primarily composed of "alcohol-ketone-a small amount of water."

[0043] The obtained liquid carbon source, after drying or moisture adjustment, is mixed with catalyst precursors such as ferrocene and optional sulfur source promoters to form a homogeneous and stable liquid precursor. This liquid precursor is carried into the high-temperature reaction zone by a carrier gas such as nitrogen. Ferrocene decomposes upon heating to form iron-based catalytic particles, while lower alcohols and acetone crack to generate carbon-containing active species, which nucleate and grow under the action of the iron-based catalytic particles to form single-walled carbon nanotubes. The sulfur source promoter can regulate the formation and activity of the catalytic particles, thereby promoting the growth of single-walled carbon nanotubes.

[0044] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention adopts the route of "distillation and fractionation - saponification / neutralization and conditioning - re-separation - floating catalytic chemical vapor deposition" to convert the low-boiling-point components in acetic acid industrial waste liquid into liquid carbon sources suitable for the preparation of single-walled carbon nanotubes. The lower esters are converted into effective alcohol carbon sources through saponification reaction, and the free acid is converted into non-volatile carboxyl salts through neutralization reaction. This reduces the acid and ester components that are not conducive to the growth of single-walled carbon nanotubes from the source, and obtains an alcohol-ketone type liquid carbon source suitable for continuous feeding preparation of single-walled carbon nanotubes.

[0045] (2) This invention converts lower esters and lower carboxylic acids in low-boiling-point components into lower alcohols, carboxylates and water through a saponification / neutralization conditioning process. Among them, the lower alcohols serve as a partial supplement of available carbon sources, and the carboxylates are non-volatile substances, thus solving the problems of coking, tar and amorphous carbon caused by lower esters and free acids.

[0046] (3) By drying the water content in the liquid carbon source, the present invention avoids the precipitation of ferrocene catalyst in the mixed flow and inhibits the conversion of the product from single-walled carbon nanotubes to multi-walled carbon nanotubes. Attached Figure Description

[0047] Figure 1 A schematic diagram of an apparatus for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid; Figure 2 The Raman spectrum of the SWCNT product obtained in Example 1 under 532 nm, 1 mW laser conditions; Figure 3 The HRTEM image of the SWCNT product obtained in Example 1; Figure 4 The images show the HAADF diagram and EDS mapping diagrams of C, O, and Fe for the SWCNT product obtained in Example 1.

[0048] Figure 1 In the middle, T-101 is the first separation tower; R-102 is a saponification / neutralization reactor; R-103 is a heavy component heat conversion unit; T-104 is the second separation tower; D-105 is a dryer; C-106 is a catalyst precursor / auxiliary raw material tank; M-107 is a hybrid / carrier gas carrying unit; R-108 is a floating catalytic chemical vapor deposition reactor; F-109 is a filtration / collection unit. Detailed Implementation

[0049] The present invention will now be described in detail with reference to specific embodiments. These embodiments are merely examples illustrating the implementation of the present invention and do not constitute a limitation thereof. Any modifications and optimizations based on the essence and concept of the present invention fall within the protection scope of the present invention.

[0050] In the following examples, GC-MS area normalization content below 0.1 area% was recorded as not detected; the water content of the waste liquid was determined by Karl Fischer titration using volumetric method; Raman spectroscopy was performed using a 532 nm laser; D / I G The ratio of the D peak intensity to the G peak intensity is calculated based on the peak area; the TGA residual mass is the residual mass obtained after thermogravimetric analysis of the unwashed crude product, which mainly comes from the catalyst and its oxides.

[0051] The apparatus for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid provided in specific embodiments of the present invention, such as... Figure 1 As shown, it includes a first separation tower T-101, a heavy component thermal conversion unit R-103, a saponification / neutralization reactor R-102, a second separation tower T-104, a dryer D-105, a mixing / carrier gas carrying unit M-107, a catalyst precursor / auxiliary raw material tank C-106, a floating catalytic chemical vapor deposition reactor R-108, and a filtration / collection unit F-109.

[0052] The first separation tower T-101 provided in the specific embodiment of the present invention is used to perform a first rectification or distillation on the obtained low-ash acetic acid industrial waste liquid S-01 to obtain a low-boiling-point fraction S-02 and a heavy fraction S-03 in the bottom of the tower. The low-boiling-point fraction S-02 includes lower alcohols, acetone, lower esters and lower carboxylic acids.

[0053] The heavy component thermal conversion unit R-103 provided in the specific embodiment of the present invention is connected to the first separation tower T-101 and is used to perform thermal conversion treatment on the obtained heavy component S-03 in the tower bottom to obtain one or more of heat, pyrolysis gas, and gasification gas S-15. The thermal conversion treatment is one or more of combustion, pyrolysis, oxygen-deficient gasification, water vapor gasification, and carbon dioxide gasification.

[0054] In a specific embodiment of the present invention, a saponification / neutralization reactor R-102 is connected to a first separation tower T-101 to perform a saponification / neutralization reaction on the received low-boiling-point fraction S-02 and alkaline substance S-04 to obtain a saponification / neutralization reaction solution S-05. The lower esters undergo saponification with the alkaline substance S-04, and the lower carboxylic acids undergo neutralization with the alkaline substance S-04. The temperature of the saponification / neutralization reaction is 20-90°C, and the reaction time is 0.1-6 h. The amount of alkaline substance S-04 added in the saponification / neutralization reaction is 0.8-20 times the molar amount of the lower esters and lower carboxylic acids in the low-boiling-point fraction S-02.

[0055] In a specific embodiment of the present invention, the second separation tower T-104 is connected to the saponification / neutralization reactor R-102 and is used to perform a second rectification or distillation on the received saponification / neutralization reaction liquid S-05 to obtain a volatile fraction S-06 containing lower alcohols, acetone and water and a carboxylate solution S-07.

[0056] In a specific embodiment of the present invention, the dryer D-105 is connected to the second separation tower T-104 to dry the received volatile fraction S-06 to obtain a liquid carbon source S-08, wherein the water content of the liquid carbon source S-08 is 0-5 wt%.

[0057] In a specific embodiment of the present invention, the mixing / carrier gas carrying unit M-107 is connected to the dryer D-105 and is used to mix the liquid carbon source S-08, the carrier gas S-09 and the catalyst precursor / auxiliary solution S-10 to obtain a mixed flow S-11.

[0058] In a specific embodiment of the present invention, the catalyst precursor / auxiliary raw material tank C-106 is connected to the mixing / carrier gas carrying unit M-107 for mixing the catalyst precursor and / or sulfur source auxiliary agent to prepare a high-concentration mother liquor S-10.

[0059] The floating catalytic chemical vapor deposition reactor R-108 provided in a specific embodiment of the present invention is connected to a mixing / carrier gas carrying unit M-107, which is used to react the mixed flow S-11 at 700-1300℃ to obtain single-walled carbon nanotube aerosol S-12.

[0060] In a specific embodiment of the present invention, the filtration / collection unit F-109 is connected to the floating catalytic chemical vapor deposition reactor R-108 to filter and collect the obtained single-walled carbon nanotube aerosol S-12, thereby obtaining crude single-walled carbon nanotube product S-13 and tail gas S-14.

[0061] Example 1 In this embodiment, acetic acid industrial waste liquid S-01 with an ash content of 0.41 wt% is used to obtain low-boiling-point fraction S-02 and heavy fraction S-03 from the bottom of the first separation tower T-101. Specifically, the collection temperature of heavy fraction S-03 from the bottom of the tower is controlled at 170°C, and the collection temperature of low-boiling-point fraction S-02 from the top of the tower is controlled at 54~66°C.

[0062] The obtained low-boiling-point fraction S-02 was added to the saponification / neutralization reactor R-102, and an alkaline substance S-04 was added under stirring to obtain the saponification / neutralization reaction solution S-05. Specifically, the reaction temperature was controlled at 50℃, the reaction time was 3 h, and the amount of alkaline substance S-04 added was 1.05 times the molar amount of lower esters and free carboxylic acids in the low-boiling-point fraction S-02.

[0063] The resulting saponification / neutralization reaction solution S-05 is passed into separation tower T-104 for a second distillation or second rectification to obtain volatile fraction S-06 and carboxylate solution S-07.

[0064] The volatile fraction S-06 was passed through a dryer D-105 for drying or moisture adjustment via adsorption using a 3A molecular sieve, yielding the dried liquid carbon source S-08. Specifically, the water content of the liquid carbon source S-08 was 2.25 wt%.

[0065] Liquid carbon source S-08, carrier gas S-09, and catalyst precursor / auxiliary solution S-10 from catalyst precursor / auxiliary feed tank C-106 are mixed in mixing unit M-107 to obtain liquid precursor / carrier gas mixed flow S-11. Specifically, carrier gas S-09 is N2 mixed with 5 vol% H2, and the total carrier gas flow rate is controlled at 1000 sccm; catalyst precursor / auxiliary mother liquor S-10 is a mixed solution of 10 wt% ferrocene and 1 wt% thiophene; the mixing mass ratio of liquid carbon source S-08 and catalyst precursor / auxiliary mother liquor S-10 is 10:1, so that the liquid carbon source feed rate is 1.0 g / min, the ferrocene feed rate is 10.0 mg / min, and the thiophene feed rate is 1.0 mg / min.

[0066] The mixed stream S-11 is fed into the single-walled carbon nanotube reactor R-108 for floating catalytic chemical vapor deposition, yielding a reaction product stream S-12. After cooling, this stream enters the filtration / collection unit F-109, where the crude single-walled carbon nanotube product S-13 is collected, and the exhaust gas S-14 is discharged. Specifically, the reactor is purged with nitrogen before heating and feeding to replace the air inside the reactor. The reaction temperature is set at 900°C, and the liquid carbon source is fed into the reactor at a constant flow rate via a peristaltic pump.

[0067] Raman spectroscopy was performed on the collected crude single-walled carbon nanotube product S-13, and the results are as follows: Figure 2 As shown, when measured with a 532 nm laser, 100-300 cm⁻¹ particles can be observed in the product. -1 The characteristic RBM peaks of single-walled carbon nanotubes are located at the peaks; calculated by peak area, I D / I G The value is approximately 0.027. This result indicates that the liquid carbon source obtained by the present invention can generate single-walled carbon nanotubes with low defect levels under floating catalytic chemical vapor deposition conditions.

[0068] The collected crude single-walled carbon nanotube product S-13 was characterized by high-resolution transmission electron microscopy, and the results are as follows: Figure 3 and Figure 4 As shown, the presence of single-walled carbon nanotube structures in the product is confirmed, and the product mainly contains C, O and Fe elements.

[0069] Thermogravimetric analysis (TGA) of the un-acid-washed crude product S-13 yielded a residual mass of 17.3 wt%. This residual mass primarily originated from iron-based catalyst residues and their oxides. After acid washing (3 mol / L hydrochloric acid for 12 h), washing, and drying, the purified product had an ash content of approximately 2.93 wt%.

[0070] Example 2: Compared to Example 1, the difference is that the obtained low-boiling-point fraction S-02 was added to the saponification / neutralization reactor R-102, and an alkaline substance S-04 was added under stirring conditions to obtain the saponification / neutralization reaction solution S-05. The reaction temperature was controlled at 20°C, and the reaction time was controlled at 6 h. All other conditions remained the same as in Example 1.

[0071] Testing revealed that ethyl acetate was detected at 0.37% of the liquid carbon source S-08. Raman spectroscopy of the collected crude single-walled carbon nanotube product S-13 showed characteristic RBM peaks, but... D / I G The value is approximately 0.053, indicating an increase in amorphous carbon and defects.

[0072] Example 3: Compared with Example 1, the volatile fraction S-06 was passed into dryer D-105 for drying or moisture adjustment to obtain dried liquid carbon source S-08, wherein the water content of liquid carbon source S-08 was 0.97 wt%. All other conditions remained the same as in Example 1.

[0073] Raman spectroscopy was performed on the collected crude single-walled carbon nanotube product S-13, and characteristic peaks of RBM were observed. D / I G The concentration decreased to 0.022, and the residual mass obtained by TGA testing was 15.2 wt%.

[0074] Example 4: Compared to Example 1, the volatile fraction S-06 was passed through a dryer D-105 for drying or moisture adjustment to obtain a dried liquid carbon source S-08. The water content of the liquid carbon source S-08 was not detected by volumetric Karl Fischer titration. All other conditions remained the same as in Example 1.

[0075] Raman spectroscopy was performed on the collected crude single-walled carbon nanotube product S-13, and RBM characteristic peaks were observed, but I D / I G The value decreased to 0.015, and the residual mass obtained by TGA testing was 15.0 wt%.

[0076] Example 5: In this embodiment, another batch of acetic acid industrial waste liquid S-01 was used as raw material. This batch of waste liquid also originated from the production, separation, or solvent recovery process of acetic acid or acetate esters, but its relative contents of lower alcohols, lower esters, free carboxylic acids, acetone, toluene, and high-boiling-point components differed from those in the waste liquid of Example 1. The specific differences are shown in the table below: Compared with Example 1, except that sample B was used as waste liquid material flow S-01, all other conditions were the same as in Example 1.

[0077] The results show that crude single-walled carbon nanotube product S-13 can be collected using sample B in this embodiment. Raman spectroscopy of the obtained crude product S-13 revealed characteristic peaks of RBM. D / I G The value was 0.039, and the residual mass obtained by TGA testing was 20.7 wt%.

[0078] Example 6 This example illustrates that the heavy component S-03 obtained from the first distillation can be used as a high-calorific-value, low-ash thermal conversion feedstock.

[0079] The heavy component S-03 in the reboiler of this embodiment is the same as the heavy component obtained in Example 1. Using Fluent simulation, the heavy component S-03 was introduced into the heavy component thermal conversion unit R-103 for thermal conversion under oxygen-deficient oxidation conditions. The feed rate of the heavy component was 3 kg / s, and the oxygen feed rate was 1.82 kg / s. The resulting gas S-15 contained approximately 33% H2, 56% CO, and 11% CO2, with no detectable CH4 or C2+ hydrocarbons.

[0080] Comparative Example 1 Referring to Example 1, except that the low-boiling-point fraction S-02 obtained in Example 1 was not subjected to saponification / neutralization treatment or second separation to remove carboxylates, but was directly prepared with ferrocene and thiophene as a liquid precursor, the carrier gas, reactor, reaction temperature, feeding method and collection method were kept the same as in Example 1.

[0081] Comparative Example 2 Referring to Example 1, except that the amount of alkaline substance added was reduced to 50% of the required molar amount to make the amount of alkali insufficient, the amounts of other materials, reaction conditions, second separation conditions, drying conditions and floating catalytic chemical vapor deposition conditions were kept the same as in Example 1.

[0082] Comparative Example 3 Referring to Example 1, except for shortening the saponification reaction time to 2 min to make the saponification reaction incomplete, the other material amounts, reaction conditions, second separation conditions, drying conditions, and floating catalytic chemical vapor deposition conditions were kept the same as in Example 1.

[0083] Comparative Example 4 Referring to Example 1, except for increasing the saponification reaction time to 12 h, the other material amounts, reaction conditions, second separation conditions, drying conditions, and floating catalytic chemical vapor deposition conditions remained the same as in Example 1.

[0084] Comparative Example 5 Referring to Example 1, except that the amount of alkaline substance added was increased to 20 times the molar amount of low-boiling-point distillate lower esters and free carboxylic acids, the amounts of other materials, reaction conditions, second separation conditions, drying conditions and floating catalytic chemical vapor deposition conditions were kept the same as in Example 1.

[0085] Comparative Example 6 Referring to Example 1, except for changing the saponification / neutralization reaction temperature to 10°C, the other material amounts, reaction conditions, second separation conditions, drying conditions, and floating catalytic chemical vapor deposition conditions remained the same as in Example 1.

[0086] Comparative Example 7 Referring to Example 1, except for changing the saponification / neutralization reaction temperature to 100°C, the other material amounts, reaction conditions, second separation conditions, drying conditions, and floating catalytic chemical vapor deposition conditions remained the same as in Example 1.

[0087] Comparative Example 8 Referring to Example 1, except that the liquid carbon source was not dried or dehydrated, the amounts of other materials, reaction conditions, second separation conditions, drying conditions, and floating catalytic chemical vapor deposition conditions were kept the same as in Example 1.

[0088] Comparative Example 9 This comparative example is used to illustrate that even if lower esters have lower boiling points and volatility, they are not suitable as effective carbon sources for single-walled carbon nanotubes in the system of this invention.

[0089] Ethanol and ethyl acetate were mixed at a mass ratio of 1:1 to obtain a mixed liquid carbon source of 50 wt% ethanol + 50 wt% ethyl acetate. This mixed liquid carbon source was then formulated with ferrocene and thiophene as a liquid precursor in the same manner as in Example 4, and a floating catalytic chemical vapor deposition reaction was carried out under the same carrier gas, reaction temperature, feed method, and collection method.

[0090] Comparative Example 10 This comparative example illustrates the adverse effects of free carboxylic acids on the growth of single-walled carbon nanotubes.

[0091] Ethanol and acetic acid were mixed at a mass ratio of 1:1 to obtain a mixed liquid carbon source of 50 wt% ethanol + 50 wt% acetic acid. This mixed liquid carbon source was then formulated with ferrocene and thiophene as a liquid precursor in the same manner as in Example 4, and a floating catalytic chemical vapor deposition reaction was carried out under the same carrier gas, reaction temperature, feed method, and collection method.

[0092] Verification Example 1 This verification example illustrates that acetone can be retained as an effective component in the liquid carbon source of this invention.

[0093] Ethanol and acetone were mixed at a mass ratio of 1:1 to obtain a mixed liquid carbon source of 50 wt% ethanol + 50 wt% acetone. This mixed liquid carbon source was then formulated with ferrocene and thiophene as a liquid precursor in the same manner as in Example 1, and a floating catalytic chemical vapor deposition reaction was carried out under the same carrier gas, reaction temperature, feed method, and collection method.

[0094] Verification Example 2 This verification example is used to establish a baseline result for traditional alcohol carbon sources and to compare it with the waste liquid conditioning carbon source obtained in this invention.

[0095] Using pure ethanol as a liquid carbon source, it was prepared into a liquid precursor with ferrocene and thiophene in the same manner as in Example 1, and a floating catalytic chemical vapor deposition reaction was carried out under the same carrier gas, reaction temperature, feed method and collection method.

[0096] Performance Analysis: In Comparative Examples 1-7 and 9-10, significant tar formation was observed at the rear end of the reactor and in the collection area during the reaction process. Raman spectroscopy of the resulting solids or sediments showed that no obvious characteristic peaks of single-walled carbon nanotubes (RBMs) were observed. D / I G More than 0.7, located at 2700 cm -1 The nearby 2D peaks disappeared, and the spectrum was dominated by amorphous carbon-related signals, indicating that no significant single-walled carbon nanotubes were generated.

[0097] In Comparative Example 8, significant condensation of water droplets was observed at the rear end of the reactor and in the collection area during the reaction process. Raman spectroscopy of the resulting solid or sediment showed a decrease in the intensity of the RBM characteristic peak and the 2D peak. D / I G When the value exceeds 0.4, the spectrum is dominated by amorphous carbon-related signals with a small amount of single-walled carbon nanotube signals, indicating that the side reactions are significantly enhanced.

[0098] Verification Examples 1 and 2 yielded carbon nanotube products after the reaction. Raman spectroscopy was performed using a 532 nm 1 mW laser, and the results showed that clear RBM characteristic peaks of single-walled carbon nanotubes could be observed in the products, and the Raman spectral results were highly similar to those of Example 1.

[0099] Analysis of the various embodiments and comparative examples reveals that the composition of the liquid carbon source used in the preparation of single-walled carbon nanotubes by floating catalytic chemical vapor deposition has a significant impact. This invention achieves the separation of light and heavy components from acetic acid industrial wastewater through a first distillation process, converts lower esters into lower alcohols through saponification, converts free carboxylic acids into non-volatile carboxylates through neutralization, and obtains an alcohol / acetone type liquid carbon source capable of stably dissolving ferrocene through a second separation and drying process. This liquid carbon source can successfully prepare single-walled carbon nanotubes. Simultaneously, the heavy components obtained from the first distillation distillation column have high calorific value, low ash content, and low sulfur content, and can be combusted, pyrolyzed, or gasified to obtain heat or gases rich in H2 and CO. Therefore, this invention achieves the high-value material utilization of light components from acetic acid industrial wastewater and the energy or gaseous carbon source utilization of heavy components.

[0100] Furthermore, after reading the above description of the present invention, any applications, additions, modifications, or variations made by those skilled in the art without departing from the meaning and scope of the present invention shall fall within the scope defined by the appended claims.

Claims

1. A method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid, characterized in that, include: (1) The low-ash acetic acid industrial waste liquid is subjected to a first rectification or distillation to obtain a low-boiling-point fraction and a heavy component in the bottom of the column, wherein the low-boiling-point fraction includes lower alcohols, acetone, lower esters and lower carboxylic acids; (2) Add an alkaline substance to the low-boiling-point fraction in step (1) to carry out a saponification / neutralization reaction to obtain a saponification / neutralization reaction solution, wherein the lower ester reacts with the alkaline substance to undergo a saponification reaction, and the lower carboxylic acid reacts with the alkaline substance to undergo a neutralization reaction. The temperature of the saponification / neutralization reaction is 20-90℃, the reaction time is 0.1-6 h, and the molar amount of the alkaline substance added in the saponification / neutralization reaction is 0.8-20 times the molar amount of the lower ester and lower carboxylic acid in the low-boiling-point fraction. (3) The saponification / neutralization reaction solution in step (2) is subjected to a second distillation or distillation to obtain a volatile fraction containing lower alcohols, acetone and water; (4) The volatile fraction in step (3) is dried to obtain a liquid carbon source, wherein the water content of the liquid carbon source is 0-5 wt%; (5) The liquid carbon source, carrier gas and catalyst precursor in step (4) are mixed to obtain a mixed stream. The mixed stream is reacted at 700-1300℃ to obtain single-walled carbon nanotube aerosol. The single-walled carbon nanotube aerosol is filtered and collected to obtain crude single-walled carbon nanotube product.

2. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The saponification / neutralization reaction is carried out at a temperature of 30-60℃ for a time of 0.5-3 h.

3. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The molar amount of alkaline substance added in the saponification / neutralization reaction is 1.0-1.2 times the molar amount of lower esters and lower carboxylic acids in the low-boiling-point fraction.

4. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The liquid carbon source has a water content of 0-1 wt%.

5. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The heavy component in the bottom column contains toluene and / or high-boiling-point organic compounds.

6. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The lower alcohol is one or more of methanol, ethanol, n-propanol, and isopropanol; The lower ester is one or more of methyl formate, ethyl formate, methyl acetate, and propyl acetate; The lower carboxylic acid is formic acid and / or acetic acid.

7. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The alkaline substance is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and potassium carbonate.

8. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, The reclaimed components in the tower undergo thermal conversion treatment to obtain one or more of the following: heat, pyrolysis gas, and gasification gas. The thermal conversion treatment is one or more of the following: combustion, pyrolysis, oxygen-deficient gasification, steam gasification, and carbon dioxide gasification.

9. The method for preparing single-walled carbon nanotubes by fractional conversion of acetic acid industrial waste liquid according to claim 1, characterized in that, In step (5), the mixed stream also includes a sulfur source promoter, wherein the catalyst precursor includes ferrocene, and the sulfur source promoter is one or more of thiophene, carbon disulfide, organic thiol, and sulfur powder.

10. An apparatus for the fractional conversion of acetic acid industrial waste liquid to prepare single-walled carbon nanotubes, characterized in that, include: The first separation tower is used to perform a first rectification or distillation on the obtained low-ash acetic acid industrial waste liquid to obtain a low-boiling-point fraction and a heavy component in the bottom of the tower. The low-boiling-point fraction includes lower alcohols, acetone, lower esters and lower carboxylic acids. A saponification / neutralization reactor, connected to a first separation tower, is used to saponify / neutralize received low-boiling-point fractions and alkaline substances to obtain a saponification / neutralization reaction solution. The lower esters undergo saponification with the alkaline substances, and the lower carboxylic acids undergo neutralization with the alkaline substances. The saponification / neutralization reaction is carried out at a temperature of 20-90°C for 0.1-6 h. The molar amount of alkaline substances added in the saponification / neutralization reaction is 0.8-20 times the molar amount of the lower esters and lower carboxylic acids in the low-boiling-point fraction. The second separation tower, connected to the saponification / neutralization reactor, is used to perform a second rectification or distillation on the received saponification / neutralization reaction liquid to obtain a volatile fraction containing lower alcohols, acetone and water. A dryer, connected to a second separation tower, is used to dry the received volatile fraction to obtain a liquid carbon source, wherein the water content of the liquid carbon source is 0-5 wt%. A mixing / carrier gas carrying unit, which is connected to a dryer, is used to mix a liquid carbon source with a catalyst precursor to obtain a mixed stream; A reaction collector, connected to a mixing / carrier gas carrying unit, is used to react the mixed stream at 700-1300°C to obtain single-walled carbon nanotube aerosols, and to filter and collect the single-walled carbon nanotube aerosols to obtain crude single-walled carbon nanotube products.

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