VOCs eutectic absorbent, preparation method and application thereof, and method for removing VOCs in waste gas

Abstract

The invention relates to the field of volatile organic compound absorption treatment, and discloses a VOCs eutectic absorbent, a preparation method and application thereof, and a method for removing VOCs in waste gas. The absorbent contains a hydrogen bond acceptor, a hydrogen bond donor and a composite component, the hydrogen bond acceptor is composed of menthol and a substance A, the substance A is selected from one of tetraalkyl quaternary ammonium bromide and thymol, and the hydrogen bond donor is selected from at least one of C9-12 saturated fatty acid and C18 monounsaturated fatty acid; the composite component is composed of a substance B and a substance C. The absorbent has extremely low saturated vapor pressure and is not easy to volatilize, meanwhile, the freezing point of the absorbent can be adjusted through the composite components, and the dynamic absorption rate of the mixed VOCs and the stability of the absorbent can be improved, so that the bottleneck that a conventional absorption method cannot be used as a VOCs tail end treatment process is broken, and deep recovery of the mixed VOCs is realized.

Description

Technical Field

[0001] The present invention relates to the field of volatile organic compound absorption treatment, and particularly relates to a VOCs eutectic absorbent, a preparation method and application thereof, and a method for removing VOCs from waste gas. Background Art

[0002] Volatile pollutants VOCs are important precursors for the formation of fine particulate pollutants PM2.5 and ozone. To achieve the coordinated control of PM2.5 and ozone pollution and the coordinated treatment of pollution reduction and carbon emission reduction, VOCs have been included in the binding indicators of ambient air quality instead of sulfur dioxide, and the prevention and control of VOCs pollution has become the focus and key of air pollution control. While the VOCs recovery technology reduces the emission of VOCs, the recovered organic matter can also be recycled, which is more energy-saving and environmentally friendly.

[0003] The processes of petrochemical industry, coal chemical industry, and the use of organic solvents are the main sources of VOCs generation. In most cases, the VOCs generated are mixtures of multiple VOCs, such as alkanes, alkenes, benzene series, etc. The commonly used VOCs recovery processes mainly include condensation, adsorption, membrane separation, and absorption. Among them, the absorption method has a mature process, simple operation and maintenance; in industry, multi-component absorbents are often used for the recovery of mixed VOCs, and the commonly used absorbents include gasoline, diesel, mineral oil, or organic solvents, etc.

[0004] However, the above-mentioned absorbents have relatively high volatility, which limits the physical absorption method to only be suitable as a pretreatment process and cannot achieve the deep recovery of VOCs. Ionic liquids have the advantages of low volatility and functional designability, but they are expensive, have a complex synthesis process, and have certain toxicity, thus limiting their industrial applications.

[0005] Therefore, there is an urgent need to provide a VOCs eutectic absorbent with low volatility and high dynamic absorption rate. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of relatively high volatility, low dynamic absorption rate, and inability to achieve deep recovery of VOCs of the existing mixed VOCs absorbents.

[0007] To achieve the above purpose, the first aspect of the present invention provides a VOCs eutectic absorbent, which contains a hydrogen bond acceptor, a hydrogen bond donor, and a composite component;

[0008] The hydrogen bond acceptor is composed of menthol and substance A, and substance A is selected from one of tetraalkylammonium bromide and thymol; the molar ratio of menthol to substance A is 0.2 - 5:1;

[0009] The hydrogen bond donor is selected from saturated fatty acids with C 9-12 and saturated fatty acids with C 18at least one of the monounsaturated fatty acids;

[0010] The composite component is composed of substance B and substance C; substance B is selected from at least one of isooctane, cyclohexane, and petroleum ether; substance C is selected from at least one of cyclohexanone and butyl acetate;

[0011] The molar ratio of the hydrogen bond acceptor, hydrogen bond donor, and composite component is 1:1 - 5:0.01 - 0.2;

[0012] The absorbent has a saturated vapor pressure of less than 100 Pa at 25°C, a saturated water content of less than 2 mol%, and a freezing point of less than 10°C.

[0013] The second aspect of the present invention provides a method for preparing a VOCs eutectic absorbent, which includes the following steps:

[0014] Perform a first mixing of the hydrogen bond acceptor, hydrogen bond donor, and composite component to obtain a VOCs eutectic absorbent;

[0015] The molar ratio of the hydrogen bond acceptor, hydrogen bond donor, and composite component is 1:1 - 5:0.01 - 0.2;

[0016] Among them, the definitions of the hydrogen bond acceptor, hydrogen bond donor, and composite component correspond to the same definitions as those in the first aspect.

[0017] The third aspect of the present invention provides a VOCs eutectic absorbent prepared by the method described in the second aspect.

[0018] The fourth aspect of the present invention provides that the VOCs eutectic absorbent described in the first aspect and / or the third aspect is used to absorb at least two types of volatile organic compounds among alkane VOCs, benzene series VOCs, and olefin VOCs.

[0019] The fifth aspect of the present invention provides a method for removing VOCs from waste gas, which includes: performing a second mixing of the waste gas containing VOCs and the absorbent to obtain a mixture containing VOCs;

[0020] The absorbent is the VOCs eutectic absorbent described in the first aspect and / or the third aspect.

[0021] The present invention provides a VOCs eutectic absorbent containing a hydrogen bond acceptor, a hydrogen bond donor, and a composite component with a molar ratio of 1:1 - 5:0.01 - 0.2. This absorbent has an extremely low saturated vapor pressure and is not easily volatile. At the same time, the composite component can adjust the freezing point and mass transfer performance of the absorbent, improve the dynamic absorption rate of mixed VOCs and the low-temperature stability of the absorbent, thereby breaking through the bottleneck that the conventional absorption method cannot be used as a VOCs end-treatment process and realizing the deep recovery of mixed VOCs. Detailed implementation mode

[0022] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0023] As described above, the first aspect of the present invention provides a VOCs eutectic absorbent, and the absorbent contains a hydrogen bond acceptor, a hydrogen bond donor, and a composite component;

[0024] The hydrogen bond acceptor is composed of menthol and substance A, and substance A is selected from one of tetraalkylammonium bromide and thymol; the molar ratio of menthol to substance A is 0.2 - 5:1;

[0025] The hydrogen bond donor is selected from at least one of saturated fatty acids with C 9-12 and monounsaturated fatty acids with C 18 ;

[0026] The composite component is composed of substance B and substance C; substance B is selected from at least one of isooctane, cyclohexane, and petroleum ether; substance C is selected from at least one of cyclohexanone and butyl acetate;

[0027] The molar ratio of the contents of the hydrogen bond acceptor, the hydrogen bond donor, and the composite component is 1:1 - 5:0.01 - 0.2;

[0028] The saturated vapor pressure of the absorbent at 25°C is less than 100 Pa, the saturated water content is less than 2 mol%, and the freezing point is less than 10°C.

[0029] Preferably, the viscosity of the absorbent at 25°C is less than 30 mPa·s. The inventor found that in this preferred case, the obtained absorbent has a better absorption effect on mixed volatile organic compounds.

[0030] In the present invention, the saturated vapor pressure of the absorbent is measured by thermogravimetric analysis, the saturated water content is measured according to the Karl Fischer titration method, and the saturated water content x w of the absorbent is calculated as follows:

[0031] x w = n w / (n w + S) × 100%

[0032] where n w is the amount of substance of water, and S is the total molar amount of the absorbent components.

[0033] Preferably, the quaternary ammonium bromide is tetraoctylammonium bromide. The inventors found that in this preferred case, the obtained absorbent has a better absorption effect on the mixed volatile organic compounds.

[0034] Preferably, the 9-12 saturated fatty acid of C 18 is n-decanoic acid, and the

[0035] Preferably, in the composite component, the molar ratio of substance B to substance C is 1-10:1. The inventors found that under this preferred condition, the obtained absorbent has a lower freezing point and a better absorption effect on the mixed volatile organic compounds.

[0036] Preferably, the hydrogen bond acceptor consists of menthol and thymol, and the molar ratio of menthol to thymol is 1-5:1.

[0037] According to a preferred specific embodiment, the hydrogen bond acceptor is menthol and thymol, the hydrogen bond donor is oleic acid, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor and the composite component is 1:1.5-4:0.01-0.1.

[0038] Preferably, the hydrogen bond acceptor is menthol and thymol, the hydrogen bond donor is oleic acid, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor and the composite component is 1:1.5-4:0.01-0.1; and the molar ratio of menthol to thymol is 1-5:1. The inventors found that in this preferred case, the obtained absorbent has a higher absorption capacity for the mixed VOCs.

[0039] According to another preferred specific embodiment, the hydrogen bond acceptor is menthol and tetraoctylammonium bromide, the hydrogen bond donors are n-decanoic acid and oleic acid; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donors and the composite component is 1:2-4:0.01-0.1; the molar ratio of menthol to tetraoctylammonium bromide is 0.2-5:1; the molar ratio of oleic acid to n-decanoic acid is 5-20:1. The inventors found that in this preferred case, the obtained absorbent has a higher absorption capacity for the mixed VOCs.

[0040] As described above, the second aspect of the present invention provides a method for preparing a VOCs eutectic absorbent, which includes the following steps:

[0041] Perform a first mixing of the hydrogen bond acceptor, the hydrogen bond donor, and the composite component to obtain a VOCs eutectic absorbent;

[0042] The molar ratio of the hydrogen bond acceptor, the hydrogen bond donor, and the composite component is 1:1-5:0.01-0.2;

[0043] Among them, the definitions of the hydrogen bond acceptor, the hydrogen bond donor, and the composite component are the same as those corresponding to the definitions described in the first aspect.

[0044] The amounts and types of the respective components involved in the second aspect of the present invention are the same as the contents and types of the corresponding components described in the first aspect of the present invention, and will not be elaborated here. Those skilled in the art should not understand this as a limitation to the present invention.

[0045] Preferably, the manner of the first mixing is selected from at least one of ultrasonic oscillation and stirring.

[0046] Preferably, the first mixing is carried out under stirring conditions, and the conditions of the first mixing at least satisfy: the temperature is 30 - 80 °C, and the stirring time is 30 - 90 min. More preferably, the conditions of the first mixing at least satisfy: the temperature is 50 - 70 °C, and the stirring time is 40 - 80 min.

[0047] It should be noted that the present invention has no special limitation on the rotation speed of the stirring, and those skilled in the art can select according to needs. For example, the stirring rotation speed is 200 - 500 rpm.

[0048] Preferably, the first mixing is carried out under ultrasonic oscillation conditions, and the conditions of the first mixing at least satisfy: the ultrasonic oscillation time is 20 - 80 min, and the temperature is 30 - 80 °C. Preferably, the conditions of the first mixing at least satisfy: the ultrasonic oscillation time is 40 - 70 min, and the temperature is 50 - 70 °C. The present invention has no special requirement for the frequency of the ultrasonic oscillation, and those skilled in the art can select according to needs.

[0049] As described above, the third aspect of the present invention provides a VOCs eutectic absorbent prepared by the method described in the second aspect.

[0050] As described above, the fourth aspect of the present invention provides the VOCs eutectic absorbent described in the first aspect and / or the third aspect for absorbing at least two types of volatile organic compounds among alkane VOCs, benzene - series VOCs, and olefin VOCs.

[0051] Preferably, the alkane VOCs are alkanes with C 2-8 ; the benzene - series VOCs are selected from at least one of benzene, toluene, xylene, and ethylbenzene; the olefin VOCs are selected from at least one of styrene, propylene, and butadiene.

[0052] In the present invention, the alkanes with C 2-8 refer to alkanes with a total number of carbon atoms of 2 - 8, such as ethane, n - butane, isobutane, n - pentane, etc.

[0053] Preferably, the absorbent has an absorption capacity for VOCs > 80 g / kg at 25°C. More preferably, the absorbent has an absorption capacity for VOCs > 100 g / kg at 25°C.

[0054] In the present invention, the absorption capacity is determined by the saturated solubility measurement method.

[0055] As described above, the fifth aspect of the present invention provides a method for removing VOCs from waste gas, which includes: secondarily mixing the waste gas containing VOCs with an absorbent to obtain a mixture containing VOCs;

[0056] The absorbent is the VOCs eutectic absorbent described in the first aspect and / or the third aspect.

[0057] Preferably, the feed volume ratio of the VOCs eutectic absorbent to the waste gas is 1:2 - 30. More preferably, the feed volume ratio of the VOCs eutectic absorbent to the waste gas is 1:2 - 20. The inventors found that in this preferred case, the VOCs eutectic absorbent and the waste gas can better contact, improving the removal rate of volatile organic compounds.

[0058] Under preferred conditions, the conditions for the secondary mixing include: temperature of 10 - 40°C, pressure of 0.1 - 0.5 MPa, and time of 0.2 - 2 min.

[0059] The present invention will be described in detail below through examples. In the following examples, the instruments, reagents, materials, etc. involved, unless otherwise specified, are all conventional instruments, reagents, materials, etc. in the prior art and can be obtained through regular commercial channels.

[0060] Example 1

[0061] This example is used to illustrate the preparation of the VOCs eutectic absorbent according to the formula and process parameters in Table 1 and the method described below for the VOCs eutectic absorbent of the present invention.

[0062] The method for preparing the VOCs eutectic absorbent includes the following steps:

[0063] Primarily mix a hydrogen bond acceptor, a hydrogen bond donor, and a composite component to obtain a VOCs eutectic absorbent;

[0064] The conditions for the primary mixing: stirring speed of 300 rpm, temperature of 70°C, and time of 40 min;

[0065] In this example, the hydrogen bond acceptor consists of 1 mol of menthol and 0.2 mol of thymol, the hydrogen bond donor is 4 mol of oleic acid; the composite component consists of 0.024 mol of isooctane and 0.012 mol of cyclohexanone;

[0066] That is, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor and the composite component is 1:3.33:0.03.

[0067] Unless otherwise specified, the remaining examples are carried out using a method similar to that of Example 1, except that the formulations and process parameters are different. See Table 1 for details.

[0068] Table 1

[0069]

[0070]

[0071] (Continued Table 1)

[0072]

[0073] Comparative Example 1

[0074] In this comparative example, a VOCs eutectic absorbent was prepared using a method similar to that of Example 1. The difference is that 0.2 mol of menthol was used to replace 0.2 mol of thymol in this comparative example; the remaining steps were the same as those of Example 1.

[0075] Comparative Example 2

[0076] In this comparative example, a VOCs eutectic absorbent was prepared using a method similar to that of Example 1. The difference is that 0.012 mol of isooctane was used to replace 0.012 mol of cyclohexanone in this comparative example; the remaining steps were the same as those of Example 1.

[0077] Comparative Example 3

[0078] In this comparative example, a VOCs eutectic absorbent was prepared using a method similar to that of Example 1. The difference is that the amount of oleic acid used in this comparative example was 7 mol; the remaining steps were the same as those of Example 1.

[0079] Comparative Example 4

[0080] In this comparative example, a VOCs eutectic absorbent was prepared using a method similar to that of Example 6. The difference is that the amount of isooctane used in this comparative example was 0.24 mol and the amount of cyclohexanone used was 0.12 mol; the remaining steps were the same as those of Example 6.

[0081] Test Example 1

[0082] Absorption Capacity Test

[0083] Under the conditions of 25 °C and 101.3 kPa, the mixed VOCs (25% vol of n-butane, 60% vol of toluene, 15% vol of propylene) were continuously introduced into the VOCs eutectic absorbent prepared in the above example. When the VOCs content in the absorbent could no longer increase, it was considered to reach absorption saturation, and the absorption amount of the VOCs eutectic absorbent at this time was measured as the absorption capacity of the alkane volatile organic compound absorbent.

[0084] Test Example 2

[0085] Test on the Removal Effect of Volatile Organic Compounds in Exhaust Gas

[0086] The removal of volatile organic compounds in the exhaust gas was completed in a packed absorption tower. The exhaust gas contained 90% vol of nitrogen, 2.5% vol of n-butane, 6% vol of toluene, and 1.5% vol of propylene. The packing was φ3 mm Raschig rings, and the theoretical number of stages was 20. The exhaust gas and the VOCs eutectic absorbent flowed into the packed absorption tower from the lower end and the upper end respectively, and the feed volume ratio of the exhaust gas to the VOCs eutectic absorbent was 12:1.

[0087] The exhaust gas and the absorbent were in countercurrent contact in the absorption tower. The contact temperature was 20 °C, the contact pressure was 0.1 MPa, and the contact time was 1 min.

[0088] After absorption, the absorbent liquid was discharged from the bottom of the packed absorption tower; the purified gas was discharged from the top of the packed absorption tower. A detection device equipped with a flame ionization detector or a photoionization detector was used to detect the content of volatile organic compounds, and the removal rates R of n-butane, toluene, and propylene were calculated.

[0089] R 正丁烷 =(x in,正丁烷 -x out,正丁烷 ) / x in,正丁烷 ×100%

[0090] R 甲苯 =(x in,甲苯 -x out,甲苯 ) / x in,甲苯 ×100%

[0091] R 丙烯 =(x in,丙烯 -x out,丙烯 ) / x in,丙烯 ×100%

[0092] Among them, x in represents the volume of olefin volatile organic compounds in the exhaust gas per unit time, and x out represents the volume of olefin volatile organic compounds in the purified gas per unit time. For example, x in,甲苯 represents the volume of toluene in the exhaust gas per unit time.

[0093] The specific test data are shown in Table 2 below.

[0094] Table 2

[0095]

[0096] From the results in the above table, it can be seen that the VOCs eutectic absorbent provided by the present invention has the characteristics of low saturated vapor pressure, not easy to volatilize, and excellent absorption effect.

[0097] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A VOCs eutectic absorbent, characterized in that, The absorbent contains a hydrogen bond acceptor, a hydrogen bond donor, and a composite component; The hydrogen bond acceptor consists of menthol and substance A, and substance A is selected from one of tetraalkylammonium bromides and thymol; the molar ratio of menthol to substance A is 0.2 - 5:1; The hydrogen bond donor is selected from C 9-12 Saturated fatty acids, C 18 At least one of the monounsaturated fatty acids; The composite component consists of substance B and substance C; substance B is selected from at least one of isooctane, cyclohexane, and petroleum ether; substance C is selected from at least one of cyclohexanone and butyl acetate; The molar ratio of the hydrogen bond acceptor, hydrogen bond donor, and composite component is 1:1 - 5:0.01 - 0.2; The saturated vapor pressure of the absorbent at 25°C is less than 100 Pa, the saturated water content is less than 2 mol%, and the freezing point is less than 10°C.

2. The VOCs eutectic absorbent according to claim 1, wherein, The tetraalkylammonium bromide is tetraoctylammonium bromide.

3. The VOCs eutectic absorbent according to claim 1 or 2, wherein, The C 9-12 's saturated fatty acid is n-decanoic acid, and the C 18 's monounsaturated fatty acid is oleic acid.

4. The VOCs eutectic absorbent according to any one of claims 1-3, wherein, In the composite component, the molar ratio of substance B to substance C is 1 - 10:

1.

5. The VOCs eutectic absorbent according to any one of claims 1-4, wherein, The hydrogen bond acceptor consists of menthol and thymol, and the molar ratio of menthol to thymol is 1 - 5:

1.

6. The VOCs eutectic absorbent according to claim 5, wherein, The hydrogen bond acceptor is menthol and thymol, and the hydrogen bond donor is oleic acid, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor and the composite component is 1:1.5 - 4:0.01 - 0.

1.

7. The VOCs eutectic absorbent according to any one of claims 1-4, wherein, The hydrogen bond acceptor is menthol and tetraoctylammonium bromide, and the hydrogen bond donors are capric acid and oleic acid; The molar ratio of the hydrogen bond acceptor to the hydrogen bond donors and the composite component is 1:2 - 4:0.01 - 0.1; the molar ratio of menthol to tetraoctylammonium bromide is 0.2 - 5:1; the molar ratio of oleic acid to capric acid is 5 - 20:

1.

8. A preparation method of a VOCs deep eutectic absorbent, characterized in that, The method includes the following steps: Perform a first mixing on the hydrogen bond acceptor, hydrogen bond donor, and composite component to obtain a VOCs eutectic absorbent; The molar ratio of the hydrogen bond acceptor, hydrogen bond donor, and composite component is 1:1 - 5:0.01 - 0.2; Among them, the definitions of the hydrogen bond acceptor, hydrogen bond donor, and composite component correspond to the definitions described in any one of claims 1 - 7.

9. The method according to claim 8, wherein The way of the first mixing is stirring; the conditions of the first mixing at least satisfy: the temperature is 30 - 80°C, and the stirring time is 30 - 90 min.

10. The method according to claim 8, wherein, The way of the first mixing is ultrasonic oscillation, and the conditions of the first mixing at least satisfy: the time of ultrasonic oscillation is 20 - 80 min, and the temperature is 30 - 80°C.

11. A VOCs eutectic absorbent prepared by the method according to any one of claims 8 - 10.

12. The VOCs eutectic absorbent according to any one of claims 1 - 7, 11 is used to absorb at least two types of volatile organic compounds among alkane VOCs, benzene - series VOCs, and olefin VOCs; Preferably, the alkane VOCs are alkanes with C 2-8 ; the benzene series VOCs are selected from at least one of benzene, toluene, xylene, and ethylbenzene; the olefin VOCs are selected from at least one of styrene, propylene, and butadiene.

13. The application according to claim 12, wherein, The absorption capacity of the absorbent for VOCs at 25°C > 80 g / kg; Preferably, the absorption capacity of the absorbent for VOCs at 25°C > 100 g / kg.

14. A method for removing VOCs from waste gas, characterized in that, The method includes: performing a second mixing on the waste gas containing VOCs and the absorbent to obtain a mixture containing VOCs; The absorbent is the VOCs eutectic absorbent according to any one of claims 1 - 7, 11.

15. The method according to claim 14, wherein The feed volume ratio of the VOCs eutectic absorbent to the waste gas is 1:2 - 30; Preferably, the conditions for the second mixing include: temperature is 10 - 40 °C, pressure is 0.1 - 0.5 MPa, and time is 0.2 - 2 min.

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