Hydrophobic deep eutectic solvent and preparation method and application thereof

Abstract

The application provides a hydrophobic deep eutectic solvent, a preparation method and application thereof, and belongs to the field of analytical chemistry. The hydrophobic deep eutectic solvent is selected from one of capric acid and lauric acid and 2-hexyl-1-decanol in a molar ratio of 1:1-2:1, and the preparation method comprises the following steps: mixing the one of capric acid and lauric acid and 2-hexyl-1-decanol in a molar ratio of 1:1-2:1, stirring at 90-100 DEG C until a homogeneous liquid is formed, and obtaining the hydrophobic deep eutectic solvent. The hydrophobic deep eutectic solvent, the preparation method and the application thereof can solve the problems of low absorption efficiency, poor regeneration performance, poor environmental protection and insufficient industrial adaptability of the existing absorbent for treating alkanes VOCs.

Description

Technical Field

[0001] This application relates to the field of analytical chemistry, and in particular to a hydrophobic eutectic solvent, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) of alkanes, such as n-pentane, n-hexane, and n-heptane, are typical air pollutants generated during the production processes of industries such as petrochemicals, paint printing, rubber processing, and fine chemicals. These substances are highly volatile and toxic, not only polluting the atmospheric environment but also harming human physiological functions such as the respiratory and nervous systems. They are also important precursors to secondary pollutants such as ozone and fine particulate matter (PM2.5), making them a key target for air pollution control in my country. Furthermore, n-pentane, n-hexane, and n-heptane are important industrial solvents and chemical raw materials with high resource recovery value. Therefore, developing efficient, environmentally friendly, and recyclable VOCs treatment technologies to achieve compliant emissions and resource recovery has become an urgent need for industry development.

[0003] Currently, industrial methods for treating alkane VOCs mainly include absorption, adsorption, and catalytic combustion. Among these, absorption has become the mainstream technology for treating low-concentration, high-flow-rate alkane VOCs waste gas due to its advantages such as simple process, convenient operation, low treatment cost, and resource recovery. The core of absorption lies in the selection of the absorbent. Commonly used absorbents in the absorption treatment of alkane VOCs include silicone oil solvents, traditional organic solvents, ionic eutectic solvents, and activated carbon. Eutectic solvents, in particular, have become a research hotspot in recent years due to their low melting point, strong thermal stability, and high design flexibility. For non-polar alkane VOCs, existing technologies often prepare hydrophobic eutectic solvents by screening hydrophobic components to improve compatibility with alkanes. Corresponding solvent preparation and absorption regeneration processes have also been developed to address the inherent shortcomings of traditional absorbents.

[0004] However, existing alkane-based VOCs absorbents and their associated preparation and application processes still suffer from numerous technical defects, making it difficult to meet the needs of practical industrial applications. Specifically, these defects include: insufficient absorption efficiency; traditional absorbents such as silicone oil and short-chain solvents have low polarity matching with non-polar alkane VOCs, resulting in high gas-liquid partition coefficients and low solubility and absorption capacity for alkanes; some ionic eutectic solvents, due to their strong polarity, also exhibit poor absorption capacity for non-polar alkanes, failing to achieve efficient treatment. Poor regeneration performance and cycle stability; silicone oil-based absorbents experience rapid performance degradation and low regeneration rates after multiple desorption-absorption cycles; ionic eutectic solvents have excessively strong hydrogen bond networks, requiring high-temperature and high-pressure conditions during regeneration, which can easily damage the solvent's structure, rendering it unusable and necessitating frequent replacement, significantly increasing industrial operating costs. The environmental friendliness and safety of some traditional organic solvents, such as halogenated hydrocarbons, are poor. These solvents are toxic and volatile, easily causing secondary air pollution during use and are difficult to biodegrade, potentially leading to water and soil pollution. Furthermore, the raw materials for synthesizing some ionic eutectic solvents are toxic and harmful, contradicting the concept of green and environmentally friendly production. Industrial adaptability is also insufficient. Some absorbents crystallize easily at room temperature, have excessively high viscosity, and poor flowability, resulting in high mass transfer resistance in conventional absorption devices such as industrial spraying, bubbling, and packed towers, leading to poor adaptability. Simultaneously, the temperature of existing absorption processes does not match the conventional emission temperature of industrial waste gas, and the regeneration process has high energy consumption, further reducing the industrial application value of the technology. Raw material and preparation costs are high. The raw materials for synthesizing ionic eutectic solvents are mostly specialized reagents, expensive and with limited sources. The low atom utilization rate in the preparation process leads to high overall solvent costs, hindering large-scale promotion. Therefore, there is an urgent need for an alkane VOCs absorbent with high absorption efficiency, good regeneration stability, environmental friendliness, readily available raw materials, simple preparation process, and application parameters suitable for industrial production to solve the current problems in the alkane VOCs treatment industry. Summary of the Invention

[0005] In view of this, this application provides a hydrophobic eutectic solvent, its preparation method and application, to solve the technical problems of low absorption efficiency, poor regeneration performance, poor environmental performance and insufficient industrial adaptability of existing absorbents for treating alkane VOCs such as n-pentane, n-hexane and n-heptane.

[0006] Specifically, this application is implemented through the following technical solution:

[0007] The first aspect of this application provides a hydrophobic eutectic solvent, wherein the hydrophobic eutectic solvent is composed of one selected from decanoic acid and lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 to 2:1.

[0008] A second aspect of this application provides a method for preparing a hydrophobic eutectic solvent, the method comprising:

[0009] The hydrophobic eutectic solvent is obtained by mixing one of the following, selected from decanoic acid and lauric acid, with 2-hexyl-1-decyl alcohol at a molar ratio of 1:1 to 2:1 and stirring at 90 to 100 °C until a homogeneous liquid is formed.

[0010] A third aspect of this application provides an application of a hydrophobic eutectic solvent, wherein the hydrophobic eutectic solvent is used as an absorbent to absorb n-pentane, n-hexane, and n-heptane in waste gas.

[0011] The hydrophobic eutectic solvent, its preparation method, and its application provided in this application have the following beneficial effects:

[0012] 1. High absorption efficiency and good selectivity: The solvent is designed based on the principle of similar solubility, which is highly matched with the polarity of the target alkanes (n-pentane, n-hexane, n-heptane). By using one of the decanoic acid and lauric acid with 2-hexyl-1-decanol, a non-polar solvent environment is constructed, which reduces the free energy of dissolution of alkanes in the solvent. This enables high-capacity and rapid absorption of low-concentration alkanes in waste gas, and its gas-liquid partition coefficient is much lower than that of traditional absorbents such as silicone oil.

[0013] 2. Excellent regeneration performance and strong cycle stability: The hydrogen bond network of this solvent remains stable during the regeneration process. Simply using vacuum heating, the absorbed alkanes can be efficiently desorbed, achieving solvent regeneration. After 10 consecutive absorption-desorption cycles, the solvent's absorption capacity for alkanes retains over 99%, reducing solvent consumption and replacement frequency in industrial operations.

[0014] 3. Green and environmentally friendly with high safety: The selected 2-hexyl-1-decyl alcohol, decanoic acid, and lauric acid are all non-ionic, low-toxicity, and biodegradable compounds. The entire preparation and application process does not produce toxic or harmful byproducts or emissions, avoiding the secondary pollution problems that may be caused by traditional halogenated hydrocarbon solvents or some ionic eutectic solvents, and meeting the requirements of green chemistry and clean production.

[0015] 4. The preparation process is simple, low-cost, and easy to industrialize: The preparation method only requires mixing and stirring the two raw materials in proportion at 90~100℃ until homogeneous, without the need for high pressure, ultrasonic assistance, or complex purification steps. The process is simple, energy-efficient, and has a short production cycle. The raw materials are all industrially available bulk chemicals or natural product derivatives, widely sourced and inexpensive, possessing the potential for large-scale industrial production and application.

[0016] 5. Mild application conditions and strong adaptability: The solvent absorption operation is carried out at a normal temperature of 20~40℃, which matches the normal temperature of industrial waste gas, requiring no additional energy consumption for preheating or cooling. The solvent itself is a homogeneous liquid at room temperature with moderate viscosity and good fluidity, and can be directly used in conventional industrial absorption devices such as spray towers and bubble towers. It has high mass transfer efficiency, low requirements for retrofitting existing waste gas treatment facilities, and excellent industrial adaptability. Attached Figure Description

[0017] Figure 1 A comparison chart of gas-DES partition coefficients of hydrophobic eutectic solvents and silicone oils for n-pentane, n-hexane, and n-heptane provided in this application;

[0018] Figure 2 A comparison of ATR-IR infrared spectra before and after synthesis using the hydrophobic eutectic solvent provided in this application;

[0019] Figure 3 The graph shows the change in absorption capacity retention rate of the hydrophobic eutectic solvent provided in this application after 10 desorption-absorption cycles. Detailed Implementation

[0020] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0021] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0022] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0023] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0024] Example 1

[0025] This embodiment provides a hydrophobic eutectic solvent, which is composed of one selected from decanoic acid and lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 to 2:1.

[0026] It should be noted that hydrophobic eutectic solvents (HDES) refer to eutectic mixtures formed by two or more nonionic long-chain organic compounds in a specific stoichiometric ratio through intermolecular hydrogen bonding. Their freezing point is significantly lower than the melting point of each individual component. They are homogeneous liquids at room temperature, insoluble in water, and can stably separate into layers upon contact with water. They also have the characteristics of being non-volatile, thermally stable, and biocompatible, which is different from ionic eutectic solvents. In this application, intermolecular hydrogen bonds are formed between the carboxyl groups of long-chain saturated fatty acids (decanoic acid, lauric acid) and the hydroxyl groups of long-chain branched fatty alcohols (2-hexyl-1-decanol), thereby constituting a stable eutectic system.

[0027] Specifically, the solvent in this application is a nonionic, hydrophobic, eutectic system, and the core components include 2-hexyl-1-decyl alcohol and decanoic acid / lauric acid, both of which are long-chain organic compounds. The molecular formula of 2-hexyl-1-decyl alcohol is C2. 16 H 34 O is a long-chain branched primary alcohol, with a molecular structure containing a 16-carbon nonpolar long-chain alkyl group and one polar primary hydroxyl group. From the perspective of alkane absorption compatibility, the nonpolar long-chain alkyl group is highly polarly matched with nonpolar alkane VOCs such as n-pentane, n-hexane, and n-heptane. According to the principle of "like dissolves like," this can significantly reduce the dissolution free energy of alkane molecules in solvents, increasing the solubility of alkanes and overcoming the technical deficiency of low absorption capacity of existing short-chain or ionic solvents for nonpolar alkanes. From the perspective of phase formation stability, the hydroxyl group of 2-hexyl-1-decyl alcohol can form intermolecular hydrogen bonds with the carboxyl group of decanoic acid / lauric acid, and the hydrogen bond strength is moderate, ensuring both phase formation stability and phase stability. It forms a homogeneous and stable eutectic system, and the strong hydrogen bonds do not affect the subsequent alkane desorption and solvent regeneration. From the perspective of industrial application suitability, compared with straight-chain alcohols with the same number of carbon atoms, the branched structure of 2-hexyl-1-decanol results in moderate molecular steric hindrance, avoiding the problems of easy crystallization and excessive viscosity of straight-chain alcohols. It ensures that the solvent is liquid at room temperature, with good fluidity, which facilitates mixing and mass transfer in industrial equipment. At the same time, this alcohol is a commonly used fatty alcohol in industry, with readily available raw materials, low preparation cost, and is non-toxic and biodegradable, which is in line with the development concept of green chemistry.

[0028] Decanoic acid (C 10 H 20 O2), lauric acid (C 12 H 24Both decanoic acid and lauric acid are long-chain saturated fatty acids with molecular structures containing polar carboxyl groups and nonpolar long-chain alkyl groups. Their melting points are approximately 31°C and 44°C, respectively. They are solid or semi-solid at room temperature. When mixed with 2-hexyl-1-decol, they can form a low-melting-point homogeneous liquid through hydrogen bonding. Both decanoic acid and lauric acid can form a dense and stable hydrogen bond network with the hydroxyl groups of 2-hexyl-1-decol, providing the core force for the formation of the eutectic system. Moreover, the hydrogen bond activity is moderate, and they will not form a strong hydrogen bond system that is difficult to resolve, ensuring the regeneration performance of the subsequent solvent. In addition, decanoic acid and lauric acid are both natural fatty acids, widely found in animal and vegetable oils. They have extremely low toxicity, good biocompatibility, and moderate melting points. When mixed with 2-hexyl-1-decol, they can form a phase without high temperature and high pressure, greatly reducing the preparation difficulty. This is different from the toxic, difficult-to-degrade, and complex ionic eutectic solvents in existing technologies.

[0029] In this embodiment, the molar ratio of decanoic acid, lauric acid, and 2-hexyl-1-decyl alcohol is limited to 1:1 to 2:1. Specifically, when the molar ratio is within the range of 1:1 to 2:1, the carboxyl groups of decanoic acid and lauric acid and the hydroxyl groups of 2-hexyl-1-decyl alcohol can fully contact each other in proportion to form a dense and uniform hydrogen bond network. This hydrogen bond network can effectively destroy the intermolecular forces of each individual component, causing the freezing point of the mixture to drop below room temperature, ensuring that it is a homogeneous liquid at room temperature. At the same time, the solvent viscosity within this ratio range is moderate, the fluidity is good, and there is no layering or precipitation, which can meet the mass transfer requirements of industrial absorption processes.

[0030] If the molar ratio is less than 1:1 (2-hexyl-1-decyl alcohol in excess), the carboxyl sites of decanoic acid and lauric acid are insufficient, and they cannot form a complete hydrogen bond network with the excess hydroxyl groups. The mixture is difficult to form a stable homogeneous system and is prone to stratification. The physical properties and absorption performance of the solvent are greatly reduced. If the molar ratio is greater than 2:1 (decanoic acid and lauric acid in excess), the excess fatty acids cannot participate in hydrogen bond formation and will exist in the system in a free state. This leads to increased solvent viscosity, poorer fluidity, and increased mass transfer resistance in the industrial absorption process. At the same time, the free fatty acids will adsorb some alkanes, making subsequent desorption difficult and reducing regeneration efficiency.

[0031] In addition, this ratio range also has the advantage of high tolerance for industrial process errors. In industrial production, there is no need to control the molar ratio to multiple decimal places. When the ratio fluctuates within ±0.1, the phase formation and absorption performance of the solvent do not change significantly, which is convenient for large-scale production.

[0032] Preferably, when the decanoic acid is used, the molar ratio of decanoic acid to 2-hexyl-1-decyl alcohol is 1:1, or the molar ratio of decanoic acid to 2-hexyl-1-decyl alcohol is 2:1. When the lauric acid is used, the molar ratio of lauric acid to 2-hexyl-1-decyl alcohol is 1:1, or the molar ratio of lauric acid to 2-hexyl-1-decyl alcohol is 2:1.

[0033] Based on the above component screening and molar ratio design, the hydrophobic eutectic solvent of this embodiment has the following advantages over existing alkane VOCs absorbents: First, it has high absorption efficiency. Its nonpolar long-chain structure is highly compatible with alkanes, and its gas-DES partition coefficient is low, resulting in an absorption capacity far superior to existing absorbents such as silicone oil and activated carbon. Second, it has excellent physical properties. It is a homogeneous liquid at room temperature with moderate viscosity and good fluidity, without crystallization or stratification, making it suitable for various industrial absorption devices. Third, it is green and environmentally friendly. All components are non-ionic organic compounds, non-toxic, and biodegradable, causing no secondary pollution during use and meeting environmental protection requirements. In addition, it is phase-stable and easily regenerated. The stable hydrogen bond network ensures that the solvent structure is not easily destroyed, and the moderate hydrogen bond strength facilitates subsequent vacuum heating to desorb alkanes and achieve solvent regeneration. Finally, the raw materials are readily available and low-cost. The core components are all commonly used industrial or natural compounds, and the preparation process does not involve complex purification steps. The industrial production cost is lower than that of ionic eutectic solvents and halogenated hydrocarbon solvents.

[0034] Example 2

[0035] This embodiment provides a method for preparing a hydrophobic eutectic solvent, the method comprising:

[0036] The hydrophobic eutectic solvent is obtained by mixing one of the following, selected from decanoic acid and lauric acid, with 2-hexyl-1-decyl alcohol at a molar ratio of 1:1 to 2:1 and stirring at 90 to 100 °C until a homogeneous liquid is formed.

[0037] It should be noted that at room temperature, decanoic acid and lauric acid are solid or semi-solid, while 2-hexyl-1-decol is liquid. Accurately weighing the two in proportion and mixing them in a reaction vessel allows the solid / semi-solid decanoic acid and lauric acid to initially contact the liquid 2-hexyl-1-decol, forming a homogeneous solid-liquid mixture. This lays the foundation for the rapid formation of hydrogen bonds during subsequent heating and stirring, effectively shortening the phase formation time. At the same time, mixing before heating avoids the volatilization loss caused by heating a single component, ensuring that the molar ratio of decanoic acid / lauric acid to 2-hexyl-1-decol is within the optimal range of 1:1 to 2:1, thereby guaranteeing the phase formation quality and absorption performance of the solvent.

[0038] The heating temperature is limited to 90-100℃ because, from the perspective of phase formation efficiency, decanoic acid has a melting point of approximately 31℃, lauric acid approximately 44℃, and 2-hexyl-1-decol approximately -7℃. At 90-100℃, all components are in a liquid state, significantly increasing the molecular motion rate. The hydroxyl groups of 2-hexyl-1-decol can quickly and fully contact the carboxyl groups of decanoic acid and lauric acid, thereby rapidly forming a stable hydrogen bond network and resulting in a fast phase formation time. If the temperature is below 90℃, the fluidity of components such as lauric acid is insufficient, molecular contact is inadequate, the hydrogen bond formation rate is slow, the phase formation time will be prolonged, and the production efficiency will be reduced. If the temperature is above 100℃, 2-hexyl-1-decol will undergo slight volatilization, leading to an imbalance in the solvent component ratio. At the same time, excessively high temperatures will increase energy consumption and operational risks in industrial production, which does not meet the requirements of low-cost industrialization. From the perspective of component stability, 90~100℃ is far below the thermal decomposition temperatures of all components (decanoic acid decomposition temperature is about 360℃, lauric acid about 390℃, and 2-hexyl-1-decanol about 280℃). Within this temperature range, component decomposition and deterioration will not occur, ensuring high purity and no impurities in the prepared solvent, thus avoiding the impact of impurities on alkane absorption performance. From the perspective of industrial applicability, 90~100℃ is a conventional medium-low temperature, which can be achieved through commonly used industrial heating methods such as electric heating and steam heating. No special high-temperature heating equipment is required, resulting in low equipment investment costs and simple operation, making it suitable for large-scale production.

[0039] It should be noted that stirring during heating can break the liquid-liquid interfacial tension, promote uniform mixing of components, and accelerate the uniform formation of hydrogen bond networks. Stirring allows for sufficient flow of components in the reaction vessel, preventing localized concentration imbalances and ensuring uniform contact between 2-hexyl-1-decyl alcohol, decanoic acid, and lauric acid throughout the system. This results in a dense and uniform hydrogen bond network, thus guaranteeing the uniformity of the prepared solvent in terms of viscosity, density, and absorption performance, avoiding fluctuations in industrial absorption efficiency due to localized property differences. Simultaneously, stirring effectively shortens the phase formation time and improves production efficiency. This application does not specify a particular stirring rate; conventional mechanical or magnetic stirring is sufficient.

[0040] It should be noted that the formation of a homogeneous liquid is used as the criterion for judging the completion of phase formation in this preparation method. Specifically, by visual observation, the reaction system should be a transparent, non-layered, and non-precipitated homogeneous liquid with no solid-liquid separation or phase separation. From a process perspective, the formation of a homogeneous liquid is a direct indication that decanoic acid / lauric acid and 2-hexyl-1-decyl alcohol have formed a complete hydrogen bond network. Only the formation of a homogeneous liquid indicates that the solvent structure is stable and possesses the absorption properties described in this application. If the system does not form a homogeneous liquid (e.g., turbidity, layering, or precipitation), it indicates that the hydrogen bonding is insufficient and the hydrogen bond network is incomplete. The physical properties and absorption performance of the solvent will decrease significantly, failing to meet the application requirements of this application.

[0041] The preparation method in this embodiment is simple and efficient, involving only two steps: mixing and heating / stirring. It eliminates the need for purification and separation, resulting in short phase formation time and high production efficiency. Energy consumption and cost are low, as the heating temperature is conventionally low to medium, eliminating the need for high-temperature and high-pressure equipment. Product quality is stable; precise ratio control and intuitive phase formation judgment standards ensure good solvent homogeneity, minimal fluctuations in physical properties and absorption performance, and high batch-to-batch stability. It has strong industrial adaptability, as all operations can be performed using conventional chemical equipment without special technical modifications, resulting in high process tolerance. Furthermore, it is environmentally friendly, generating no byproducts and producing no wastewater, waste gas, or waste residue, aligning with the industry trend of green production.

[0042] Example 3

[0043] This embodiment provides an application of a hydrophobic eutectic solvent. Specifically, the hydrophobic eutectic solvent is used as an absorbent to absorb n-pentane, n-hexane, and n-heptane in waste gas.

[0044] The absorption process involves contacting the hydrophobic eutectic solvent at a temperature of 20-40°C, directly mixing and contacting it with waste gas containing n-pentane, n-hexane, and n-heptane. After absorbing the alkanes, the hydrophobic eutectic solvent is regenerated through vacuum heating. The regenerated solvent is then used to absorb n-pentane, n-hexane, and n-heptane from the waste gas again. After 10 consecutive desorption-absorption cycles, the hydrophobic eutectic solvent retains over 99% of the absorption capacity for n-pentane, n-hexane, and n-heptane compared to the fresh solvent.

[0045] It should be noted that this application applies the solvent to the absorption and treatment of n-pentane, n-hexane, and n-heptane in waste gas. Among them, n-pentane, n-hexane, and n-heptane are common VOCs in industries such as petrochemicals, coatings, printing, and rubber. They are characterized by high volatility, high toxicity, and poor water solubility, and are key targets for air pollution control. At the same time, these alkanes are also important industrial solvents and chemical raw materials, and have high resource recovery value.

[0046] It should be noted that the absorption contact temperature is a core parameter affecting the absorption efficiency of alkane. This application limits it to 20~40℃. The selection of this temperature range is based on Henry's Law and the actual needs of industrial applications, achieving a balance between alkane solubility and mass transfer efficiency. According to Henry's Law, the solubility of nonpolar gases in liquid solvents decreases with increasing temperature. n-Pentane, n-Hexane, and n-Heptane are all volatile nonpolar gases. At 20~40℃, their solubility in the solvent of this application is at a relatively high level, which can ensure efficient absorption capacity. If the temperature is higher than 40℃, the volatility of alkane increases, the solubility decreases, and the absorption efficiency decreases. If the temperature is lower than 20℃, although the solubility of alkane increases slightly, the viscosity of the solvent will increase significantly, the mass transfer resistance will increase, the absorption rate will decrease, and additional refrigeration equipment will be required in industrial production, significantly increasing operating costs. Meanwhile, 20~40℃ is the normal emission temperature range for industrial waste gas. There is no need to preheat or cool the waste gas. The waste gas can be directly connected to the absorption system, which simplifies the process, reduces equipment investment and operating costs, and improves the industrial adaptability of the solution.

[0047] This application employs an absorption method involving direct mixing and contact between the solvent and waste gas, including conventional gas-liquid contact methods such as spray absorption, bubbling absorption, and packed tower absorption. The aim is to maximize the contact area between the gas and liquid phases and shorten the mass transfer distance of alkane molecules from the gas phase to the liquid phase. This contact method offers high mass transfer efficiency; direct mixing and contact allow for sufficient contact between the solvent and waste gas, forming a large gas-liquid interface, enabling alkane molecules to rapidly diffuse from the gas phase to the liquid phase. Furthermore, this process is simple and has low equipment costs, requiring no complex membrane separation or catalytic reaction devices. Only conventional industrial absorption towers and spray devices are needed, resulting in low equipment investment and easy operation and maintenance. Moreover, there is no secondary pollution. The solvent used in this application is highly hydrophobic and immiscible with water, preventing secondary water pollution during absorption due to solvent dissolution. Simultaneously, the solvent has a high boiling point and is not easily volatile, preventing secondary atmospheric pollution due to solvent evaporation, thus meeting environmental protection requirements.

[0048] It should also be noted that a vacuum heating regeneration process was designed for the solvent after absorbing alkanes, achieving solvent recycling and significantly reducing industrial operating costs. The boiling points of n-pentane, n-hexane, and n-heptane are approximately 36.1℃, 69℃, and 98.4℃, respectively, while the boiling point of the hydrophobic eutectic solvent in this application is above 250℃, indicating a significant difference in volatility. Furthermore, there are only weak van der Waals forces between alkanes and the solvent, with no strong chemical bonds. Therefore, heating the solvent after absorbing alkanes under vacuum conditions lowers the boiling point of the alkanes, causing the dissolved alkanes to rapidly vaporize and escape from the solvent system. The solvent itself, due to its high boiling point and strong thermal stability, does not vaporize or decompose, achieving efficient separation of the solvent and alkanes and realizing solvent regeneration.

[0049] The vacuum heating regeneration process has the following advantages: First, it has high regeneration efficiency and thorough regeneration. Under vacuum conditions, the boiling point of alkanes is significantly reduced, and they can be rapidly vaporized at a heating temperature of 80~120℃. The absorption performance of the regenerated solvent is basically unaffected. Second, it has good solvent stability. The regeneration heating temperature is much lower than the thermal decomposition temperature and hydrogen bond network destruction temperature of the solvent. During the regeneration process, only the weak van der Waals forces between the alkanes and the solvent are destroyed, without destroying the solvent's own hydrogen bond network, ensuring the stability of the solvent's structure and performance, and allowing for multiple cycles of use. Third, it has low energy consumption. The energy consumption of vacuum heating is much lower than that of traditional atmospheric pressure distillation regeneration, and no regenerator needs to be added, which can further reduce industrial operating costs. Fourth, it balances resource recovery and environmental protection. The vaporized alkane vapors during the regeneration process can be recovered through a condensation device and reused as an industrial solvent or chemical raw material, realizing the resource recovery of alkane VOCs. Moreover, there is no wastewater or waste residue discharge during the regeneration process.

[0050] It should also be noted that after 10 consecutive desorption-absorption cycles, the hydrophobic eutectic solvent of this application still maintains an absorption capacity of over 99% of that of the fresh hydrophobic eutectic solvent for n-pentane, n-hexane, and n-heptane. Specifically, the solvent is formed by nonionic components through hydrogen bonds of moderate strength. During the regeneration process, only alkanes are desorbed, without disrupting the hydrogen bond network of the solvent. Therefore, the structure and properties of the solvent can remain stable over a long period.

[0051] With over 99% absorption capacity retention after 10 consecutive cycles, the frequency of solvent replacement can be significantly reduced, thus decreasing solvent consumption in industrial production and lowering operating costs. Simultaneously, it enhances the continuous operation capability of the absorption system, eliminating the need for frequent shutdowns to replace solvents and ensuring the continuity of industrial production. Furthermore, it reduces the generation of waste solvents, lowering the cost and environmental risks associated with waste solvent treatment.

[0052] To accurately and systematically evaluate the alkane absorption performance and regeneration stability of the solvent in this application, the following formulas (I)-(IV) are used for quantitative calculation. Specifically, gas chromatography is used to evaluate the absorption effect of the eutectic solvent provided in this application as an absorbent on the absorption of n-pentane, n-hexane, and n-heptane in the gas. The specific method is as follows:

[0053] Add the same amount of one of the following: n-pentane, n-hexane, or n-heptane to several headspace vials of the same volume containing different amounts of water. Seal the headspace vials and shake them at a certain temperature for a period of time until they reach partition equilibrium. Use gas chromatography to determine the content of n-pentane, n-hexane, or n-heptane in the gas phase at the partition equilibrium.

[0054] The relationship after the allocation is balanced is shown in equation (I):

[0055] ;

[0056] Where A represents the peak area measured by gas chromatography;

[0057] V L The volume of the liquid phase is expressed in mL.

[0058] α is a constant containing multiple parameters;

[0059] V G The volume of the gas phase is expressed in mL.

[0060] K represents the gas-water partition coefficient.

[0061] This relationship allows us to determine the gas-water partition coefficient K values ​​of n-pentane, n-hexane, and n-heptane in water when they are in gas-water distribution equilibrium.

[0062] Different amounts of one of n-pentane, n-hexane, and n-heptane were added to several headspace vials containing the same amount of water. The gas-water partition coefficients K of n-pentane, n-hexane, and n-heptane in water were used.

[0063] The formula for calculating the concentration of VOCs in the gas phase is shown in equation (II):

[0064] ;

[0065] Among them, C G This indicates the concentration of VOCs in the gas phase, in g•mL. -1 ;

[0066] n VOC This indicates the amount of VOC added, expressed in mol.

[0067] Plot the gas phase VOC concentration C G The calibration curve between the peak area A measured by gas chromatography and the peak area A.

[0068] After the eutectic solvent reaches absorption equilibrium with one of the samples (n-pentane, n-hexane, or n-heptane), the gas phase is extracted and analyzed using a gas chromatograph.

[0069] The formula for calculating the concentration of VOCs in the DES phase is shown in equation (Ⅲ):

[0070] ;

[0071] Among them, C DES This indicates the concentration of VOCs in the DES phase, in g•mL. -1 ;

[0072] V DES The volume of the DES phase is expressed in mL.

[0073] The formula for calculating the gas-DES distribution coefficient is shown in equation (Ⅳ):

[0074] ;

[0075] Among them, K DES Indicates the gas-DES distribution coefficient;

[0076] For absorbing n-pentane, n-hexane, and n-heptane from waste gas, the choice of absorbent is crucial. The absorption capacity of the absorbent depends on its physical properties such as polarity, viscosity, and solubility. A good absorbent is characterized by: polarity close to that of n-pentane, n-hexane, and n-heptane; low viscosity for easy mass transfer; and high solubility for n-pentane, n-hexane, and n-heptane.

[0077] The application and regeneration scheme of this embodiment has high absorption efficiency. The solvent has a large absorption capacity and fast mass transfer rate for n-pentane, n-hexane, and n-heptane, which can effectively treat high-flow-rate, low-concentration industrial alkane waste gas and ensure that the waste gas meets emission standards. Secondly, the operating conditions are mild, with an absorption temperature of 20~40℃ and a regeneration temperature of 60~90℃, neither of which requires high-temperature and high-pressure equipment. In addition, the regeneration performance is excellent. The vacuum heating regeneration process is simple and efficient. The solvent retains more than 99% of its absorption capacity after 10 cycles and can be reused for a long time, which greatly reduces industrial operating costs. Moreover, the solvent does not cause secondary pollution, and alkane resources can be recovered during the regeneration process.

[0078] To further verify the feasibility of preparing the hydrophobic eutectic solvent, its absorption performance, and regeneration stability, this application conducts experimental verification through the following specific examples 1-19: Specific Implementation Example 1

[0080] Preparation steps of 2-hexyl-1-decyl alcohol-decanoic acid DES: Dry 2-hexyl-1-decyl alcohol and decanoic acid in a vacuum drying oven. Weigh an appropriate amount of decanoic acid into a 50 mL Erlenmeyer flask, and then slowly add 2-hexyl-1-decyl alcohol (2-hexyl-1-decyl alcohol / decanoic acid molar ratio of 1:1). After the addition is complete, place the mixture in a constant temperature magnetic heating mantle at approximately 90°C and heat with stirring for 4 hours. A homogeneous and transparent solution forms in the flask, thus obtaining 2-hexyl-1-decyl alcohol:decanoic acid DES (DES-1). Specific Implementation Example 2

[0082] Preparation steps of 2-hexyl-1-decyl alcohol-decanoic acid DES: 2-hexyl-1-decyl alcohol and decanoic acid are dried in a vacuum drying oven. An appropriate amount of decanoic acid is then weighed into a 50 mL Erlenmeyer flask, and 2-hexyl-1-decyl alcohol is slowly added dropwise (decanoic acid / 2-hexyl-1-decyl alcohol molar ratio is 2:1). After the addition is complete, the mixture is placed in a constant-temperature magnetic heating mantle at approximately 90°C and heated with stirring for 4 hours. A homogeneous and transparent solution is formed in the flask, thus obtaining 2-hexyl-1-decyl alcohol:decanoic acid DES (DES-2). Specific Implementation Example 3

[0084] Preparation steps of 2-hexyl-1-decyl alcohol-lauric acid DES: Dry 2-hexyl-1-decyl alcohol and lauric acid in a vacuum drying oven. Weigh an appropriate amount of lauric acid into a 50 mL Erlenmeyer flask, and then slowly add 2-hexyl-1-decyl alcohol dropwise (lauric acid / 2-hexyl-1-decyl alcohol molar ratio of 1:1). After the addition is complete, place the mixture in a constant temperature magnetic heating mantle at approximately 90°C and heat with stirring for 4 hours. A homogeneous and transparent solution forms in the flask, thus obtaining 2-hexyl-1-decyl alcohol:lauric acid DES (DES-3). Specific Implementation Example 4

[0086] Preparation steps of 2-hexyl-1-decyl alcohol-lauric acid DES: Dry 2-hexyl-1-decyl alcohol and lauric acid in a vacuum drying oven. Weigh an appropriate amount of lauric acid into a 50 mL Erlenmeyer flask, and then slowly add 2-hexyl-1-decyl alcohol dropwise (lauric acid / 2-hexyl-1-decyl alcohol molar ratio is 2:1). After the addition is complete, place the mixture in a constant temperature magnetic heating mantle at approximately 90°C and heat with stirring for 4 hours. A homogeneous and transparent solution forms in the flask, thus obtaining 2-hexyl-1-decyl alcohol:lauric acid DES (DES-4). Specific Implementation Example 5

[0088] 3.5 g of the eutectic solvent (DES-1) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-pentane sample. The vial was sealed and incubated at 30 °C in a shaker until equilibrium was reached. After a certain time, the molar mass of absorbed n-pentane was calculated by gas chromatography. The partition coefficient of n-pentane in the eutectic solvent composed of decanoic acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 at a certain temperature was 0.01085. Specific Implementation Example 6

[0090] 3.5 g of the eutectic solvent (DES-1) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-hexane. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-hexane was calculated by gas chromatography. The partition coefficient of n-hexane in the eutectic solvent composed of decanoic acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 at a certain temperature was 0.00344. Specific Implementation Example 7

[0092] 3.5 g of eutectic solvent (DES-1) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-heptane sample. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-heptane was calculated by gas chromatography. The partition coefficient of n-heptane in a eutectic solvent composed of decanoic acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 at a certain temperature was 0.00116. Specific Implementation Example 8

[0094] Take 3.5 g of the eutectic solvent (DES-2) into a 20 mL headspace vial, add 0.5 μL of n-pentane sample, seal the vial, and incubate at 30 °C in a shaker until equilibration. After a certain time, measure the molar mass of absorbed n-pentane by gas chromatography. The partition coefficient of n-pentane in the eutectic solvent composed of decanoic acid and 2-hexyl-1-decyl alcohol in a molar ratio of 2:1 at a certain temperature is 0.01013. Specific Implementation Example 9

[0096] 3.5 g of the eutectic solvent (DES-2) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-hexane. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-hexane was calculated by gas chromatography. The partition coefficient of n-hexane in the eutectic solvent composed of decanoic acid and 2-hexyl-1-decyl alcohol in a molar ratio of 2:1 at a certain temperature was 0.00338. Specific Implementation Example 10

[0098] 3.5 g of the eutectic solvent (DES-2) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-heptane. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-heptane was calculated by gas chromatography. The partition coefficient of n-heptane in the eutectic solvent composed of decanoic acid and 2-hexyl-1-decyl alcohol in a molar ratio of 2:1 was 0.00116 at a certain temperature. Specific Implementation Example 11

[0100] Take 3.5 g of the eutectic solvent (DES-3) into a 20 mL headspace vial, add 0.5 μL of n-pentane sample, seal the vial, and incubate at 30 °C in a shaker until equilibration. After a certain time, measure the molar mass of absorbed n-pentane by gas chromatography. The partition coefficient of n-pentane in the eutectic solvent composed of lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 at a certain temperature is 0.01102. Specific Implementation Example 12

[0102] 3.5 g of the eutectic solvent (DES-3) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-hexane. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-hexane was calculated by gas chromatography. The partition coefficient of n-hexane in the eutectic solvent composed of lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 at a certain temperature was 0.00356. Specific Implementation Example 13

[0104] 3.5 g of eutectic solvent (DES-3) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-heptane sample. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-heptane was calculated by gas chromatography. The partition coefficient of n-heptane in a eutectic solvent composed of lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 at a certain temperature was 0.00122. Specific Implementation Example 14

[0106] 3.5 g of eutectic solvent (DES-4) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-pentane sample. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-pentane was calculated by gas chromatography. The partition coefficient of n-pentane in the eutectic solvent composed of lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 2:1 at a certain temperature was 0.01151. Specific Implementation Example 15

[0108] 3.5 g of the eutectic solvent (DES-4) was placed in a 20 mL headspace vial, followed by the addition of 0.5 μL of n-hexane. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-hexane was calculated by gas chromatography. The partition coefficient of n-hexane in the eutectic solvent composed of lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 2:1 at a certain temperature was 0.00344. Specific Implementation Example 16

[0110] 3.5 g of eutectic solvent (DES-4) was placed in a 20 mL headspace vial, and 0.5 μL of n-heptane was added. The vial was sealed and incubated at 30 °C in a shaker. After a certain time, the molar mass of absorbed n-heptane was calculated by gas chromatography. The partition coefficient of n-heptane in the eutectic solvent composed of lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 2:1 was 0.00122 at a certain temperature. Specific Implementation Example 17

[0112] After adding 0.5 μL of n-pentane to the regenerated DES-4, the sample was sealed and shaken to equilibrate at 30°C. After a certain period, the molar mass of absorbed n-pentane was measured by gas chromatography and calculated. Compared with fresh DES-4, the absorption capacity reached 99%. This absorption and desorption process was performed 10 times, and the absorption capacity of DES-4 after each regeneration was 99% of that of fresh DES-4. Specific Implementation Example 18

[0114] After adding 0.5 μL of n-hexane to the regenerated DES-4, the sample was sealed and equilibrated by shaking in a shaker at 30°C. After a certain period of time, the molar mass of absorbed n-hexane was calculated by gas chromatography. Compared with fresh DES-4, the absorption capacity reached 99%. This absorption and desorption process was performed 10 times, and the absorption capacity of DES-4 after each regeneration was 99% of that of fresh DES-4. Specific Implementation Example 19

[0116] After adding 0.5 μL of n-heptane to the regenerated DES-4, the sample was sealed and equilibrated by shaking in a shaker at 30°C. After a certain period of time, the molar mass of absorbed n-heptane was calculated by gas chromatography. Compared with fresh DES-4, the absorption capacity reached 99%. This absorption and desorption process was performed 10 times, and the absorption capacity of DES-4 after each regeneration was consistently 99% of that of fresh DES-4.

[0117] To further highlight the technical advantages of the hydrophobic eutectic solvent in this application, comparative examples 1-4 are provided:

[0118] Comparative Example 1

[0119] Take 3.5 g of silicone oil into a 20 mL headspace vial, add 0.5 μL of n-pentane, seal the vial, and incubate at 30 °C in a shaker until equilibrium is reached. After a certain time, measure the molar mass of absorbed n-pentane by gas chromatography and calculate the result. The partition coefficient of n-pentane in silicone oil at a certain temperature is 0.01239.

[0120] Comparative Example 2

[0121] Take 3.5 g of silicone oil in a 20 mL headspace vial, add 0.5 μL of n-hexane, seal the vial, and incubate at 30 °C in a shaker until equilibrium is reached. After a certain time, measure the molar mass of absorbed n-hexane by gas chromatography and calculate the result. The partition coefficient of silicone oil with n-hexane at a given temperature is 0.00417.

[0122] Comparative Example 3

[0123] 3.5 g of silicone oil was placed in a 20 mL headspace vial, and 0.5 μL of n-heptane was added. The vial was sealed and incubated in a shaker at 30 °C for a certain period of time. The molar mass of absorbed n-heptane was then calculated by gas chromatography. The partition coefficient of n-heptane in silicone oil at a certain temperature was 0.00171.

[0124] Comparative Example 4

[0125] Take 3.5g of the "dodecyl alcohol-lauric acid (1:1) hydrophobic eutectic solvent" disclosed in the prior art (from the paper: Kiszkiel-Taudul, I.; Stankiewicz, P., Microextraction of Tigecycline Using Deep Eutectic Solvents and Its Determination in Milk by LC-MS / MS Method. J.Agric. Food. Chem. 2023, 71, (30), 11716-11725.) into a 20mL headspace vial, add 0.5μL of n-hexane, seal, and equilibrate by shaking in a shaker at 30℃. After a certain period of time, measure and calculate the partition coefficient by gas chromatography. The gas-DES partition coefficient of this solvent to n-hexane is 0.00445. This value is much higher than the partition coefficient of all hydrophobic eutectic solvents to n-hexane in Examples 5-16 of this application, confirming that the 2-hexyl-1-decyl alcohol branched long-chain structure used in this application can significantly improve the compatibility of solvents with alkanes compared to traditional straight-chain dodecanol, thereby improving the alkanes absorption efficiency.

[0126] Figure 1 The comparison chart of gas-DES partition coefficients of the hydrophobic eutectic solvent and silicone oil for n-pentane, n-hexane, and n-heptane provided in this application, combined with the experimental data of specific examples 5-16 and comparative examples 1-3, shows that the gas-DES partition coefficients of the hydrophobic eutectic solvent prepared in this application for the three alkanes are significantly lower than those of existing silicone oil absorbents. Moreover, the longer the carbon chain of the alkane, the more obvious the difference in partition coefficients. This directly confirms that the solvent of this application has a much better ability to dissolve and absorb alkane VOCs than existing conventional absorbents. This is highly consistent with the technical characteristics of the solvent of this application described in Example 1, which has a high degree of matching with alkanes due to its non-polar long-chain structure and has high-efficiency absorption performance.

[0127] To further verify the synthesis mechanism of the hydrophobic eutectic solvent described in this application and to confirm that 2-hexyl-1-decanol, decanoic acid, and lauric acid successfully form a homogeneous eutectic system through intermolecular hydrogen bonds, this application conducted attenuated total reflectance infrared spectroscopy (ATR-IR) tests on 2-hexyl-1-decanol, decanoic acid, lauric acid, and the four hydrophobic eutectic solvents prepared in specific Examples 1-4. The synthesis effect of the eutectic solvent was verified by chemical structure characterization.

[0128] The above-mentioned raw materials and the prepared hydrophobic eutectic solvent were tested using ATR-IR. Figure 2 The ATR-IR infrared spectra before and after synthesis using the hydrophobic eutectic solvent provided in this application are shown in the following figures. Figure 2 As shown, the infrared spectrum of unsynthesized 2-hexyl-1-decyl alcohol is at 3321, 2920, 2852, 1466, 1035, and 722 cm⁻¹. -1 A characteristic peak is observed at [value missing]. These peaks are attributed to the stretching vibrations of the OH group, the asymmetric stretching vibrations of the -CH2 and -CH3 groups, the symmetric stretching vibrations of the -CH2 and -CH3 groups, the bending vibration of -CH2, the stretching vibration of CO, and the bending vibration of the -CH2 group in long-chain aliphatic chains, respectively. The infrared spectra of unsynthesized decanoic acid and lauric acid are at 2915, 2847, 1692, 1472-1409, 1302-1193, 938, 721-681 cm⁻¹. -1 A characteristic peak is displayed at 3321 cm⁻¹, which are attributed to the asymmetric stretching vibrations of -CH₂ and -CH₃ groups, the symmetric stretching vibrations of -CH₂ and -CH₃ groups, the C=O stretching vibration, the -CH₂ bending vibration, the CO stretching vibration, the out-of-plane stretching vibration of the OH group, and the -CH₂ bending vibration of the long-chain aliphatic chain, respectively. After synthesizing a hydrophobic eutectic solvent, 2-hexyl-1-decyl alcohol exhibits a characteristic peak at 3321 cm⁻¹. -1 The characteristic peaks of the OH group at 938 cm⁻¹ showed a weakening and broadening, with decanoic acid and lauric acid exhibiting this phenomenon at 938 cm⁻¹. -1 The characteristic peaks of the OH group at 1692 cm⁻¹ also weakened and broadened simultaneously, while the characteristic peaks of decanoic acid and lauric acid at 1692 cm⁻¹ also showed a similar trend. -1 The C=O stretching vibration peak at the specified position exhibits a blue shift. These spectral changes are typical characteristics of intermolecular hydrogen bond formation, directly confirming that this application successfully formed a hydrophobic eutectic solvent through intermolecular hydrogen bonding via a combination of 2-hexyl-1-decyl alcohol and decanoic acid / lauric acid. This characterization result further corroborates the formation mechanism of the eutectic solvent described in this application. The stable formation of hydrogen bonds is the core structural basis for this solvent's ability to significantly lower the freezing point, form a homogeneous liquid at room temperature, and possess moderate hydrogen bond strength, facilitating subsequent vacuum heating regeneration.

[0129] It should also be noted that the above specific embodiments 1-19 are gradient verification experiments, which verify the technical effect of the hydrophobic eutectic solvent of this application from three dimensions: solvent preparation feasibility, alkane absorption performance, and cycle regeneration stability. Comparative examples 1-3 highlight the technical advantages of the solvent of this application by comparing it with existing conventional absorbents.

[0130] Specific Examples 1-4 are verification experiments for the preparation of hydrophobic eutectic solvents. Decanoic acid, lauric acid, and 2-hexyl-1-decyl alcohol were combined in molar ratios of 1:1 and 2:1, and the solvent was prepared under the process conditions of 90-100℃ specified in this application. The experimental results show that all four combinations can form a homogeneous and transparent liquid eutectic solvent under mild conditions, and there is no layering or crystallization at room temperature. This confirms that the component combinations, molar ratio range, and preparation process specified in this application have good feasibility and repeatability. It also verifies that the molar ratio of 1:1 to 2:1 described in Example 1 is the optimal ratio range for phase formation, providing qualified experimental samples for subsequent absorption and regeneration performance tests.

[0131] Specific Examples 5-16 are verification experiments on the absorption performance of alkane in hydrophobic eutectic solvents. Using four solvents prepared in Examples 1-4 as test objects, the absorption of VOCs from three typical alkanes—n-pentane, n-hexane, and n-heptane—was tested. Gas chromatography was used to detect and calculate the gas-DES partition coefficient, quantitatively evaluating the solvent's absorption capacity. The experimental results show that all solvents prepared in this application exhibit excellent absorption performance for the three alkanes, with extremely low gas-DES partition coefficients. Furthermore, the longer the carbon chain of the alkane, the lower the partition coefficient and the higher the absorption capacity. Simultaneously, for the same decanoic acid and lauric acid, the solvent absorption performance at a 1:1 molar ratio is slightly better than that at a 2:1 molar ratio, and the solvent absorption performance of decanoic acid is slightly better than that of lauric acid. This provides a specific reference for solvent selection in industrial applications and directly confirms the conclusion in Example 1 that the solvents of this application, due to their non-polar long-chain structure, are highly compatible with alkanes and possess efficient absorption performance.

[0132] Specific examples 17-19 are verification experiments on the cyclic regeneration stability of hydrophobic eutectic solvents. DES-4, which has better absorption performance, was selected as the test sample. Ten consecutive desorption-absorption cycles were performed on n-pentane, n-hexane, and n-heptane to verify the regeneration performance and long-term stability of the solvent. Figure 3 Please refer to the graph showing the change in absorption capacity retention after 10 desorption-absorption cycles for the hydrophobic eutectic solvent provided in this application. Figure 3Experimental results show that after 10 cycles, the solvent's absorption capacity for the three alkanes can remain at more than 99% of that of the fresh solvent, with no significant decay. This confirms that the hydrogen bond network structure of the solvent in this application is stable. The vacuum heating regeneration process can only destroy the weak van der Waals forces between the solvent and the alkanes, without destroying the solvent's own hydrogen bond system. This is consistent with the technical characteristics of the solvent in this application, which has excellent regeneration performance and can be recycled for a long time, as described in Example 3.

[0133] Comparative Examples 1-3 selected silicone oil, a conventional absorbent used in existing industries for treating alkane VOCs, and tested its absorption performance on n-pentane, n-hexane, and n-heptane under the same experimental conditions as in the specific examples, serving as a reference for the solvent in this application. The comparative experimental data show that the gas-liquid partition coefficient of silicone oil for the three alkanes is significantly higher than that of the hydrophobic eutectic solvent in this application, while its absorption capacity is much lower. Furthermore, based on existing technical knowledge, silicone oil has a low regeneration rate and poor recycling performance, in stark contrast to the over 99% regeneration rate of the solvent in this application after 10 cycles. This comparative experiment strongly demonstrates that the hydrophobic eutectic solvent in this application has significant technical advantages over existing conventional absorbents in terms of alkane VOCs absorption performance, effectively solving the problems of low absorption efficiency and poor regeneration performance of existing absorbents.

[0134] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An application of a hydrophobic eutectic solvent, characterized in that, The hydrophobic eutectic solvent is used as an absorbent to absorb n-pentane, n-hexane, and n-heptane in the waste gas; the hydrophobic eutectic solvent is composed of one selected from decanoic acid and lauric acid and 2-hexyl-1-decyl alcohol in a molar ratio of 1:1 to 2:

1.

2. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, The molar ratio of decanoic acid to 2-hexyl-1-decyl alcohol is 1:

1.

3. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, The molar ratio of decanoic acid to 2-hexyl-1-decyl alcohol is 2:

1.

4. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, The molar ratio of lauric acid to 2-hexyl-1-decyl alcohol is 1:

1.

5. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, The molar ratio of lauric acid to 2-hexyl-1-decyl alcohol is 2:

1.

6. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, The contact temperature during the absorption process is 20~40℃, and the hydrophobic eutectic solvent is directly mixed and contacted with the waste gas containing n-pentane, n-hexane and n-heptane.

7. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, The hydrophobic eutectic solvent, after absorbing alkanes, is regenerated by vacuum heating. The regenerated hydrophobic eutectic solvent is then used to absorb n-pentane, n-hexane, and n-heptane from the waste gas again.

8. The application of the hydrophobic eutectic solvent according to claim 1, characterized in that, After 10 consecutive desorption-absorption cycles, the hydrophobic eutectic solvent still maintains more than 99% of the absorption capacity of the fresh hydrophobic eutectic solvent for n-pentane, n-hexane, and n-heptane.

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