Absorbent for removing volatile hydrocarbon compounds and use thereof

Abstract

The application discloses an absorbent for absorbing and removing volatile hydrocarbon compounds and application thereof, and relates to the technical field of volatile organic compound waste gas treatment, which is characterized in that the main functional component of the absorbent is long-chain fatty ether compounds, which can be used alone or in combination with high-boiling-point alcohol, high-boiling-point ester, silicone oil, mineral oil or amide solvent.The general structure of the long-chain fatty ether compounds is R1--O--R2; R1 and R2 are C6-C12 straight-chain or branched alkyl groups, and the total carbon number of R1 and R2 is 12-20. The absorbent can effectively absorb and remove volatile hydrocarbon compounds such as n-hexane, heptane, cyclohexane, benzene, toluene, ethylbenzene, dimethylbenzene and volatile components of naphtha, and can be regenerated by desorption through heating, pressure reduction or inert gas stripping.

Description

Technical Field

[0001] This invention relates to the field of volatile organic compound (VOC) waste gas treatment technology, and more specifically, to an absorbent for the absorption and removal of volatile hydrocarbons and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are a common class of gaseous pollutants in the production and use processes of industries such as petrochemicals, oil storage and transportation, coating, printing, pharmaceuticals, and fine chemicals. They typically include multiple components such as alkanes, cycloalkanes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, and esters. VOC emissions from different processes vary in composition, concentration, and emission methods, and are generally characterized by complex composition, large concentration fluctuations, strong hydrophobicity of some components, and noticeable odors. Direct emission without effective treatment not only wastes resources but may also participate in atmospheric photochemical reactions, promoting the formation of ozone and secondary organic aerosols, adversely affecting ambient air quality and human health. Therefore, developing efficient removal technologies suitable for complex VOC emissions is of great significance.

[0003] Currently, VOCs waste gas treatment methods mainly include adsorption, combustion, condensation, membrane separation, and absorption. Among these, adsorption is suitable for enriching low-concentration VOCs, but the adsorbent is easily affected by humidity and complex components, and the regeneration process increases operating costs. Combustion has high treatment efficiency, but consumes a lot of energy, and usually requires supplemental fuel for low-concentration waste gases. Condensation is suitable for recovering and treating high-concentration, easily condensable organic waste gases, but its effect on low-boiling-point or low-concentration components is limited. Membrane separation has advantages such as compact equipment and simple operation, but the stability, flux, and selectivity of membrane materials still limit its engineering applications. Absorption transfers VOCs to a liquid absorbent through gas-liquid contact, featuring simple process, large processing capacity, suitability for continuous operation, and strong adaptability to multi-component waste gases. It is particularly suitable for treating medium-to-high concentration, complex-composition, or resource-recovery-value VOCs waste gases.

[0004] Existing VOCs absorbents mainly include water, mineral oil, diesel oil, organic alcohols, ester solvents, and some high-boiling-point organic absorbents. Water has limited solubility for hydrophobic VOCs, making it difficult to effectively absorb non-polar or weakly polar components such as alkanes, cycloalkanes, and aromatics. While some organic absorbents have some solubility for VOCs, they still suffer from insufficient absorption capacity, high energy consumption during regeneration, incomplete desorption, or significant volatilization losses. For complex, multi-component VOCs waste gases generated in petrochemical, oil storage and transportation, and refining processes, traditional absorbents often struggle to simultaneously achieve absorption capacity, low volatilization loss, and recyclability. Therefore, there is still a need to develop a low-volatility, regenerable organic absorbent suitable for the absorption and removal of hydrophobic VOCs. Summary of the Invention

[0005] The purpose of this invention is to provide an absorbent for the absorption and removal of volatile hydrocarbons and its application. This invention utilizes long-chain aliphatic ether compounds for VOCs absorption and removal. These compounds contain both ether bonds and long-chain hydrophobic alkyl structures. The ether bonds provide molecular polarity, which enhances the interaction between the absorbent and some oxygen-containing, aromatic, or weakly polar VOCs. The long-chain alkyl structures improve their compatibility and solubility for hydrocarbon VOCs such as alkanes, cycloalkanes, and aromatics. Simultaneously, long-chain aliphatic ether compounds typically have high boiling points and low vapor pressures, minimizing significant volatilization loss during absorption and reducing absorbent consumption and the risk of secondary pollution. Therefore, these compounds hold promise as a VOCs absorption and removal solvent with combined absorption capacity, low volatilization loss, and regeneration potential for the treatment of complex, multi-component organic waste gases.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: an absorbent for the absorption and removal of volatile hydrocarbon compounds, wherein the main functional component of the absorbent is a long-chain aliphatic ether compound, and the long-chain aliphatic ether compound has the following general structural formula:

[0007] R1—O—R2

[0008] In the formula, R1 and R2 are independently straight-chain or branched alkyl groups of C6 to C12, and the total number of carbons in R1 and R2 is 12 to 20.

[0009] The present invention is further configured such that the long-chain aliphatic ether compound is selected from one or more of dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, hexyloctyl ether, heptyloctyl ether, octylnonyl ether, octyldodecyl ether, and di(2-ethylhexyl) ether;

[0010] The long-chain aliphatic ether compound is liquid at the absorption temperature and has a saturated vapor pressure of no more than 40 Pa at 25 °C.

[0011] The mass fraction of long-chain aliphatic ether compounds in the absorbent is 50% to 100%.

[0012] The present invention is further configured such that the long-chain aliphatic ether compound is one or more of dioctyl ether, dinonyl ether, octyl dodecyl ether, and di(2-ethylhexyl) ether;

[0013] The absorbent contains 70% to 100% by mass of long-chain aliphatic ether compounds.

[0014] This invention further provides an application method for the above-mentioned absorbent, which is used for the absorption and removal of volatile hydrocarbon waste gas. The volatile hydrocarbon waste gas originates from petrochemical, oil storage and transportation, oil refining, coating, printing, fine chemical, or organic solvent use processes. The volatile hydrocarbons include one or more of alkanes, cycloalkanes, aromatic hydrocarbons, or naphtha volatile components. Specifically, the alkanes are n-hexane or heptane, the cycloalkanes are cyclohexane, and the aromatic hydrocarbons are benzene, toluene, ethylbenzene, or xylene. The absorption and removal process employs bubbling absorption, packed tower absorption, spray absorption, plate tower absorption, or rotating packed bed absorption. Two specific application methods are as follows:

[0015] The first method involves the long-chain aliphatic ether compounds in the absorbent acting alone as functional components on volatile hydrocarbon compounds.

[0016] The second method: The absorbent uses long-chain aliphatic ether compounds as the main functional component and is used in combination with other high-boiling-point organic solvents; the high-boiling-point organic solvents are selected from one or more of high-boiling-point alcohols, high-boiling-point esters, silicone oils, mineral oils, and amide solvents; the mass ratio of the long-chain aliphatic ether compound to the high-boiling-point organic solvent is 50:50 to 99:1.

[0017] The preferred mass ratio of the long-chain aliphatic ether compound to the high-boiling-point organic solvent is 70:30 to 99:1.

[0018] The present invention further provides a method for absorbing and removing volatile hydrocarbons using the above-mentioned absorbent, wherein the waste gas containing volatile hydrocarbons is brought into gas-liquid contact with the absorbent, and the volatile hydrocarbons are transferred from the gas phase to the absorbent to obtain purified gas and rich absorbent; the rich absorbent is treated by heating, depressurizing, inert gas stripping or a combination thereof to regenerate the absorbent and recycle it for the absorption and removal of volatile hydrocarbons.

[0019] In summary, the present invention has the following beneficial effects: The absorbent of the present invention uses long-chain aliphatic ether compounds as the main functional components, and the molecule simultaneously possesses ether bonds and long-chain alkyl structures, which can enhance the compatibility between the absorbent and volatile hydrocarbons such as alkanes, cycloalkanes, aromatic hydrocarbons, and naphtha volatile components, while reducing the self-volatilization loss of the absorbent during the absorption process. The rich absorbent after absorbing volatile hydrocarbons can be desorbed and regenerated by heating, depressurizing, inert gas stripping, or a combination thereof, and is suitable for continuous absorption-desorption-regeneration processes. Under the conditions of the embodiments of the present invention, the removal rate of n-hexane by the long-chain aliphatic ether absorbent reaches over 87%, and the removal rate of total VOCs from naphtha volatile components reaches over 93%, with a maximum of over 98%, demonstrating good absorption and removal effects of hydrocarbon VOCs and promising prospects for industrial application. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the n-hexane absorption and desorption experiment process in Examples 1-4 of this invention;

[0021] Figure 2 This is a schematic diagram of the experimental process for the gas absorption of naphtha components in 5-8 of this invention.

[0022] In the diagram: 1. Hexane gas generator; 2. Packed absorption tower; 3. Heat exchanger at the top of the absorption tower; 4. Lean and rich liquid heat exchanger; 5. Packed desorption tower; 6. Heat exchanger at the bottom of the desorption tower; 7. Naphtha component gas generator. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1-2 Using dioctyl ether, dinonyl ether, octyl dodecyl ether, and di(2-ethylhexyl) ether as representative long-chain aliphatic ether absorbents, the application effect of the absorbents described in this invention in the absorption and removal of hydrocarbon VOCs is illustrated.

[0024] The saturated vapor pressure of long-chain aliphatic ether compounds was calculated using the COSMO-RS method. For the calculation, the structures of each long-chain aliphatic ether molecule were first optimized and COSMO files were generated. Then, the saturated vapor pressure at different temperatures was calculated using COSMOtherm software.

[0025] Calculations show that the saturated vapor pressure of dioctyl ether is 0.127 Pa at 25 °C, 0.347 Pa at 35 °C, 43.303 Pa at 95 °C, and 60.012 Pa at 100 °C; the saturated vapor pressure of dinonyl ether is 0.028 Pa at 25 °C, 0.082 Pa at 35 °C, 15.337 Pa at 95 °C, and 21.842 Pa at 100 °C; the saturated vapor pressure of octyl dodecyl ether is 0.001 Pa at 25 °C, 0.004 Pa at 35 °C, 1.539 Pa at 95 °C, and 2.296 Pa at 100 °C; and the saturated vapor pressure of di(2-ethylhexyl) ether is... The saturated vapor pressure at ℃ is 0.318 Pa, at 35 ℃ it is 0.836 Pa, at 95 ℃ it is 85.360 Pa, and at 100 ℃ it is 116.703 Pa.

[0026] Example 1

[0027] Dioctyl ether was used for the absorption and desorption of n-hexane. The experimental setup included a n-hexane gas generator, a packed absorption tower, a packed desorption tower, a peristaltic pump, a heat exchanger, and a constant-temperature circulating water bath. The absorption tower had an inner diameter of 41 mm and a packing height of 600 mm; the desorption tower had an inner diameter of 30 mm and a packing height of 500 mm; the packing consisted of 6 mm θ-rings; the absorption temperature was 35 ℃; the desorption temperature was 95 ℃; the gas flow rate was 100 mL / min; the absorbent flow rate or circulation flow rate was 1 mL / min; and the stabilization time for the absorption and desorption experiments was approximately 5 h.

[0028] Before the experiment, 500 mL of dioctyl ether was added to the bottom of the desorption tower, and the peristaltic pump was started to circulate the dioctyl ether between the absorption tower and the desorption tower. The temperature of the absorption tower was controlled at 35 ℃, and the temperature of the desorption tower was controlled at 95 ℃. Nitrogen gas was bubbled into a washing bottle containing n-hexane to obtain simulated waste gas containing n-hexane, which was continuously introduced into the absorption tower from the bottom at a flow rate of 100 mL / min. Dioctyl ether entered from the top of the absorption tower at a flow rate of 1 mL / min, and came into countercurrent contact with the simulated waste gas containing n-hexane. The rich liquid after absorbing n-hexane flowed out from the bottom of the absorption tower and was sent to the desorption tower for desorption regeneration by the peristaltic pump; the regenerated dioctyl ether was cooled by a heat exchanger and returned to the top of the absorption tower for recycling. After the system ran continuously for 5 hours, gas samples were taken from the inlet and outlet of the absorption tower, and the concentration of n-hexane was determined by gas chromatography.

[0029] Experimental results show that the concentration of n-hexane at the inlet of the absorption tower is 3.19 g / m³. 3The concentration of n-hexane at the outlet is 0.38 g / m³. 3 The hexane removal rate was 88.01%.

[0030] Example 2

[0031] The absorption and desorption of n-hexane was performed using dinonyl ether. The experimental setup and method were the same as in Example 1, except that the absorbent was replaced with dinonyl ether instead of dioctyl ether.

[0032] Experimental results show that the concentration of n-hexane at the inlet of the absorption tower is 4.337 g / m³. 3 The concentration of n-hexane at the outlet is 0.475 g / m³. 3 The hexane removal rate was 89.06%.

[0033] Example 3

[0034] Octyl dodecyl ether was used for the absorption and desorption of n-hexane. The experimental setup and method were the same as in Example 1, except that the absorbent was replaced with octyl dodecyl ether instead of dioctyl ether.

[0035] Experimental results show that the concentration of n-hexane at the inlet of the absorption tower is 2.184 g / m³. 3 The concentration of n-hexane at the outlet is 0.267 g / m³. 3 The hexane removal rate was 87.77%.

[0036] Example 4

[0037] The absorption and desorption of n-hexane was carried out using di(2-ethylhexyl) ether. The experimental setup and method were the same as in Example 1, except that the absorbent was replaced with di(2-ethylhexyl) ether instead of dioctyl ether.

[0038] Experimental results show that the concentration of n-hexane at the inlet of the absorption tower is 3.209 g / m³. 3 The concentration of n-hexane at the outlet is 0.380 g / m³. 3 The hexane removal rate was 88.17%.

[0039] Comparative Example 1

[0040] Hexane absorption and desorption experiments were conducted using diisooctyl adipate, a high-boiling-point organic absorbent reported in the literature. The experimental method was the same as in Example 1, except that the absorbent was replaced with diisooctyl adipate instead of dioctyl ether.

[0041] Experimental results show that the concentration of n-hexane at the inlet of the absorption tower is 3.48 g / m³. 3 The concentration of n-hexane at the outlet is 0.70 g / m³. 3 The hexane removal rate was 79.97%.

[0042] Example 5

[0043] A continuous absorption experiment of naphtha component gas was conducted using dioctyl ether. The experimental setup included a naphtha component gas generator, a packed absorption tower, a peristaltic pump, an absorbent storage tank, and a constant-temperature circulating water bath.

[0044] In the experiment, naphtha was added to a bubble column, and nitrogen gas was introduced from the bottom of the bubble column, continuously contacting the naphtha in a countercurrent flow to obtain a simulated naphtha component gas containing VOCs. The naphtha flow rate was 0.5 mL / min, and the nitrogen flow rate was 100 mL / min. Dioctyl ether was added to the absorbent storage tank, and a peristaltic pump was used to send the dioctyl ether to the top of the absorber column at a flow rate of 1 mL / min. The simulated naphtha component gas entered from the bottom of the absorber column at a flow rate of 100 mL / min, and the gas and liquid phases contacted countercurrently within the packing layer. The absorption temperature was controlled at 35 ℃. After the system ran for 1 hour, gas samples were taken from the inlet and outlet of the absorber column, and the total VOCs and the concentrations of each major component were determined by gas chromatography.

[0045] Experimental results show that the total VOCs concentration at the inlet of the absorption tower is 1637 g / m³. 3 The total VOCs concentration at the outlet was 82.11 g / m³. 3 The total VOCs removal rate was 94.98%.

[0046] Example 6

[0047] A continuous absorption experiment of naphtha component gases was conducted using dinonyl ether. The experimental setup and method were the same as in Example 5, except that the absorbent was replaced with dinonyl ether instead of dioctyl ether.

[0048] Experimental results show that the total VOCs concentration at the inlet of the absorption tower is 1630 g / m³. 3 The total VOCs concentration at the outlet was 39.87 g / m³. 3 The total VOCs removal rate was 97.55%.

[0049] Example 7

[0050] Continuous absorption experiments of naphtha component gases were conducted using octyl dodecyl ether. The experimental setup and method were the same as in Example 5, except that the absorbent was replaced with octyl dodecyl ether instead of dioctyl ether.

[0051] Experimental results show that the total VOCs concentration at the inlet of the absorption tower is 1758 g / m³. 3 The total VOCs concentration at the outlet was 30.50 g / m³. 3 The total VOCs removal rate was 98.26%.

[0052] Example 8

[0053] A continuous absorption experiment of naphtha component gases was conducted using di(2-ethylhexyl) ether. The experimental setup and method were the same as in Example 5, except that the absorbent was replaced with di(2-ethylhexyl) ether instead of dioctyl ether.

[0054] Experimental results show that the total VOCs concentration at the inlet of the absorption tower is 1610 g / m³. 3 The total VOCs concentration at the outlet was 100.57 g / m³. 3 The total VOCs removal rate was 93.76%.

[0055] Comparative Example 2

[0056] The absorption of naphtha components by gas was carried out using diisooctyl adipate, a high-boiling-point organic absorbent reported in the literature. The experimental method was the same as in Example 5, except that the absorbent was replaced by diisooctyl adipate instead of dioctyl ether.

[0057] Experimental results show that the total VOCs concentration at the inlet of the absorption tower is 1550 g / m³. 3 The total VOCs concentration at the outlet was 516.2 g / m³. 3 The total VOCs removal rate was 64.89%.

[0058] As shown in the examples and comparative examples, dioctyl ether, dinonyl ether, octyl dodecyl ether, and di(2-ethylhexyl) ether can all effectively absorb and remove hydrocarbon VOCs. Specifically, under hexane absorption and desorption conditions, the removal rates of hexane by dioctyl ether, dinonyl ether, octyl dodecyl ether, and di(2-ethylhexyl) ether were 88.01%, 89.06%, 87.77%, and 88.17%, respectively, all higher than that of diisooctyl adipate. Under continuous absorption conditions of naphtha components, the removal rates of total VOCs by dioctyl ether, dinonyl ether, octyl dodecyl ether, and di(2-ethylhexyl) ether were 94.98%, 97.55%, 98.26%, and 93.76%, respectively, all significantly higher than that of diisooctyl adipate. The above results indicate that the long-chain aliphatic ether compounds of the present invention have good absorption and removal effects on n-hexane and multi-component naphtha VOCs, and can be used as effective absorbents for the absorption and removal of hydrocarbon VOCs.

[0059] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. An absorbent for the absorption and removal of volatile hydrocarbon compounds, characterized in that: The main functional component of the absorbent is a long-chain aliphatic ether compound, which has the following general structural formula: R1—O—R2 In the formula, R1 and R2 are independently straight-chain or branched alkyl groups of C6 to C12, and the total number of carbons in R1 and R2 is 12 to 20.

2. The absorbent for the absorption and removal of volatile hydrocarbon compounds according to claim 1, characterized in that: The long-chain aliphatic ether compound is selected from one or more of dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, hexyloctyl ether, heptyloctyl ether, octylnonyl ether, octyldodecyl ether, and di(2-ethylhexyl) ether; The long-chain aliphatic ether compound is liquid at the absorption temperature and has a saturated vapor pressure of no more than 40 Pa at 25 °C. The mass fraction of long-chain aliphatic ether compounds in the absorbent is 50% to 100%.

3. The absorbent for the absorption and removal of volatile hydrocarbon compounds according to claim 2, characterized in that: The long-chain aliphatic ether compound is one or more of dioctyl ether, dinonyl ether, octyl dodecyl ether, and di(2-ethylhexyl) ether; The absorbent contains 70% to 100% by mass of long-chain aliphatic ether compounds.

4. The application of the absorbent for the absorption and removal of volatile hydrocarbon compounds according to any one of claims 1-3, characterized in that: The long-chain aliphatic ether compounds in the absorbent act as functional components on volatile hydrocarbon compounds.

5. The application of an absorbent for the absorption and removal of volatile hydrocarbon compounds according to any one of claims 1-3, characterized in that: The absorbent uses long-chain aliphatic ether compounds as the main functional component and is used in combination with other high-boiling-point organic solvents; the high-boiling-point organic solvents are selected from one or more of high-boiling-point alcohols, high-boiling-point esters, silicone oils, mineral oils, and amide solvents; the mass ratio of the long-chain aliphatic ether compound to the high-boiling-point organic solvent is 50:50 to 99:

1.

6. The application of the absorbent for the absorption and removal of volatile hydrocarbon compounds according to claim 5, characterized in that: The mass ratio of the long-chain aliphatic ether compound to the high-boiling-point organic solvent is 70:30 to 99:

1.

7. The application of an absorbent for the absorption and removal of volatile hydrocarbon compounds according to any one of claims 1-3, characterized in that: The absorbent is used for the absorption and removal of volatile hydrocarbon waste gas, which originates from petrochemical, oil storage and transportation, oil refining, coating, printing, fine chemical or organic solvent use processes. The volatile hydrocarbons include one or more of alkanes, cycloalkanes, aromatics or naphtha volatile components.

8. The application of the absorbent for the absorption and removal of volatile hydrocarbons according to claim 7, characterized in that: The alkane is n-hexane or heptane, the cycloalkanes are cyclohexane, and the aromatic hydrocarbons are benzene, toluene, ethylbenzene, or xylene.

9. The application of the absorbent for the absorption and removal of volatile hydrocarbons according to claim 7, characterized in that: The absorption and removal process is carried out by bubbling absorption, packed tower absorption, spray absorption, plate tower absorption, or rotating packed bed absorption.

10. A method for the absorption and removal of volatile hydrocarbon compounds, characterized in that: Waste gas containing volatile hydrocarbons is brought into gas-liquid contact with the absorbent described in any one of claims 1-3, wherein the volatile hydrocarbons are transferred from the gas phase to the absorbent, resulting in purified gas and a rich absorbent; the rich absorbent is treated by heating, depressurizing, inert gas stripping, or a combination thereof, to regenerate the absorbent and recycle it for the absorption and removal of volatile hydrocarbons.

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