Polyamide-PTFE composite nanofiltration membrane, preparation method and method for extracting o-methylphenol from coal tar

Abstract

The invention discloses a polyamide-PTFE composite nanofiltration membrane, a preparation method and a method for extracting o-methylphenol from coal tar, the polyamide-PTFE composite nanofiltration membrane comprises a separation layer and a support layer, and the separation layer is a polyamide membrane prepared by adopting a reverse interfacial polymerization method. And the supporting layer is a polytetrafluoroethylene nanofiltration membrane. According to the separation layer, a polyamide membrane contains a large number of amide groups which can form hydrogen bonds with hydroxyl groups in o-methylphenol in coal tar, so that the o-methylphenol is adsorbed on the surface of the polyamide membrane. The polyamide-PTFE composite nanofiltration membrane prepared by the preparation method disclosed by the invention shows excellent nanofiltration performance in an organic solution. The rejection rate of the polyamide-PTFE composite nanofiltration membrane to o-methylphenol can reach 26.1-60.6%, and the permeation flux of an organic solvent can reach 15-30 L.m <-2 >. Bar <-1 >. S <-1 >. In addition, the polyamide-PTFE composite nanofiltration membrane is relatively high in stability, can keep stable interception performance under 15-day continuous operation, and has a very good industrial application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a polyamide-PTFE composite nanofiltration membrane, a preparation method and a method for extracting o-methylphenol from coal tar. Background Art

[0002] In the field of chemical industry, o-cresol is an important organic chemical raw material with wide application value. It is mainly used in the synthesis of various fine chemicals such as pesticides, medicines, fragrances, dyes, etc. With the continuous development of related industries, the demand for o-cresol is also growing.

[0003] Coal tar is an important byproduct of coal processing. It has a complex composition and contains a large amount of aromatic compounds. Extracting o-cresol from coal tar has important practical significance. On the one hand, coal tar has a large output, which provides a rich source of raw materials for the extraction of o-cresol; on the other hand, deep processing of coal tar to extract high value-added products such as o-cresol can improve the comprehensive utilization level of coal tar and achieve efficient utilization of resources.

[0004] At present, the technology of extracting o-methylphenol from coal tar still faces some challenges. For example, the composition of coal tar is complex, and the content of o-methylphenol is relatively low, so efficient separation and purification technology is needed; economic factors such as energy consumption and equipment investment need to be considered during the extraction process; at the same time, it is also necessary to ensure the environmental protection of the extraction process to avoid secondary pollution. Therefore, the development of more efficient, economical and environmentally friendly technology for extracting o-methylphenol from coal tar has become an important research direction in the current chemical industry. Compared with traditional phenol extraction technology, nanofiltration membrane phenol extraction technology has the advantages of green and high efficiency, small production scale, low investment and no pollution, and is favored by many researchers. Nanofiltration membrane separation technology is also widely used in seawater desalination, oil-water separation, organic solution purification and other fields. Summary of the invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, the object of the present invention is to provide a polyamide-PTFE composite nanofiltration membrane, a preparation method and a method for extracting o-methylphenol from coal tar. For the mixed model coal tar of o-methylphenol and toluene, the present invention aims to realize the extraction of o-methylphenol by constructing a composite membrane resistant to organic solvents. The molecular surface of the polyamide membrane contains a large number of amide groups that form hydrogen bonds with the hydroxyl groups in the o-methylphenol, so that the o-methylphenol can be adsorbed on the surface layer of the polyamide membrane, thereby achieving the effect of efficient and green phenol extraction. The method has a certain interception effect on o-methylphenol.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A polyamide-PTFE composite nanofiltration membrane, comprising a separation layer and a support layer, wherein the separation layer is a polyamide membrane prepared on the support layer by reverse interfacial polymerization of polyethyleneimine, piperazine, trimesic acid chloride, and n-hexane solution. The mass concentration ratio of polyethyleneimine to piperazine is 1:0.2-1:1, the thickness of the separation layer is 20-200 nm, and the area of ​​the separation layer is 5-100 cm 2 The supporting layer is a polytetrafluoroethylene nanofiltration membrane with a molecular weight cutoff of 200-2000 Da1. The function of the supporting layer is to prevent the separation layer from being pressed through and not to hinder the passage of the permeate.

[0008] The method for preparing a polyamide-PTFE composite nanofiltration membrane comprises the following steps:

[0009] Step (1): soaking the nanofiltration membrane polytetrafluoroethylene in a hexane solution dissolved with trimesoyl chloride;

[0010] Step (2): pouring a mixed amine aqueous solution of polyethyleneimine and piperazine onto the surface of the soaked nanofiltration membrane polytetrafluoroethylene to initiate an interfacial polymerization reaction, thereby forming a polyamide film on the nanofiltration membrane polytetrafluoroethylene, thereby obtaining a polyamide-PTFE composite nanofiltration membrane;

[0011] Step (3): drying the obtained polyamide-PTFE composite nanofiltration membrane in an oven;

[0012] Step (4): After the dried polyamide-PTFE composite nanofiltration membrane is washed with deionized water for multiple times, it is stored in deionized water to maintain a sterile environment.

[0013] In step (1), the concentration of trimesoyl chloride in n-hexane solvent is 0.6 g / L. At this concentration, the defect repair of the polyamide composite membrane is the best.

[0014] In step (2), the mass concentration ratio of polyethyleneimine to piperazine is 1:0.1-1:1. Within this mass concentration ratio range, the defect degree of the prepared polyamide composite membrane is minimal.

[0015] The method for extracting o-methylphenol from coal tar using a polyamide-PTFE composite nanofiltration membrane comprises the following steps:

[0016] Step (1): First, the polyamide-PTFE composite nanofiltration membrane is soaked in an isopropanol solution to remove the air in the membrane; then the polyamide-PTFE composite nanofiltration membrane is placed in a permeation tank of an organic solvent-resistant nanofiltration membrane evaluation device equipped with a cold trap circulation pump, and the effective area of ​​the polyamide-PTFE composite nanofiltration membrane is recorded as A;

[0017] Step (2): Add the prepared concentration of o-cresol and toluene model oil into the stock solution bottle, stir the model oil evenly and stabilize the temperature at 20-30° C. before using it to simulate coal tar. The o-cresol concentration in the model oil is marked as Cp;

[0018] Step (3): connect the stock solution bottle to the permeation pool of the organic solvent-resistant nanofiltration membrane evaluation device and check its sealing; turn on the cold trap circulation pump, operate the nanofiltration membrane evaluation device to stabilize the permeation pressure of the polyamide-PTFE composite nanofiltration membrane at 0.1-4 bar, start timing and record the permeation time of the model oil in the stock solution bottle in the polyamide-PTFE composite nanofiltration membrane as t;

[0019] Step (4): After running for a period of time, the nanofiltration membrane evaluation device and the cold trap circulation pump are turned off, and the volume of the liquid that permeates through the polyamide-PTFE composite nanofiltration membrane in the permeation pool is recorded as V, and the concentration of o-methylphenol in the permeate is recorded as C f ;

[0020] Step (5): Repeat steps (3) and (4) for multiple times, and take the average value of the obtained data;

[0021] Step (6): Analyze the concentration of o-methylphenol in the permeate using a gas chromatograph, and calculate the permeation flux and retention rate of the polyamide-PTFE composite nanofiltration membrane.

[0022] The two important parameters for evaluating the adsorption of o-methylphenol by polyamide-PTFE composite nanofiltration membrane are permeation flux and retention rate, and the calculation formula is:

[0023] Permeation flux: P = V / (A × Δp × t)

[0024] Retention rate: R = (1-C P / C f )×100%

[0025] V is the volume of permeate, L

[0026] ΔP represents the osmotic pressure, bar

[0027] T is the penetration time, s

[0028] A represents the effective area of ​​polyamide-PTFE composite nanofiltration membrane, m 2

[0029] C p Indicates the concentration of o-cresol in the model oil, g / L

[0030] C f It represents the concentration of o-cresol in the permeate, g / L.

[0031] The concentration of o-methylphenol in the model coal tar is 50-100 g / L. Within this concentration range, the polyamide composite membrane has the highest retention rate for phenol and the lowest permeation flux.

[0032] The invention discloses a polyamide-PTFE composite nanofiltration membrane prepared by reverse interfacial polymerization and provides a method for extracting phenol from the nanofiltration membrane. The method utilizes the selective adsorption of o-methylphenol by the polyamide-PTFE composite nanofiltration membrane to achieve the purpose of extracting phenol.

[0033] The polyamide-PTFE composite membrane obtained by the above method was tested under the conditions of a mass concentration ratio of polyethyleneimine to piperazine of 1:0.1, a test temperature of 25°C, an o-cresol concentration of 100 g / L in a mixed solution of o-cresol and toluene, and a pressure of 0.11 bar after the membrane. The permeation flux of the polyamide-PTFE composite nanofiltration membrane was 18.9 m -2 bar -1 ·s -1 , the retention rate of o-cresol was 60.6%.

[0034] The polyamide-PTFE composite nanofiltration membrane prepared by the present invention exhibits excellent nanofiltration performance in organic solutions. The retention rate of the polyamide-PTFE composite nanofiltration membrane for o-cresol can reach 26.1-60.6%, and the permeation flux of organic solvents can reach 15-30 L·m -2 bar -1 ·s -1 In addition, the polyamide-PTFE composite nanofiltration membrane has high stability and can maintain stable interception performance under 15 days of continuous operation, which has good industrial application prospects.

[0035] The preparation method is stable and reliable. The preparation method of the invention improves the interception rate of the composite membrane prepared by the traditional interfacial polymerization method, is also suitable for the preparation of other types of organic solvent-resistant membranes, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is the XRD pattern of polyamide-PTFE composite membrane.

[0037] Figure 2 It is the FTIR spectrum of polyamide-PTFE composite membrane.

[0038] Figure 3 It is the long-term stability spectrum of polyamide-PTFE composite membrane. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and some specific embodiments.

[0040] The present invention provides a polyamide-PTFE composite membrane, a preparation method and a method for extracting o-methylphenol from coal tar. The polyamide-PTFE composite membrane comprises a separation layer and a support layer, wherein the separation layer is a polyamide membrane and the support layer is a polytetrafluoroethylene nanofiltration membrane.

[0041] Implementation Cases

[0042] Example 1

[0043] (1) The preparation method of polyamide-PTFE composite nanofiltration membrane is as follows:

[0044] The nanofiltration membrane polytetrafluoroethylene is soaked in a n-hexane solution containing 0.6 g / L benzyl chloride for 2 minutes; a mixed amine aqueous solution of 12.5 g / L polyethyleneimine and 12.5 g / L piperazine is poured onto the surface of the soaked nanofiltration membrane polytetrafluoroethylene to initiate an interfacial polymerization reaction for 5 minutes, so that a layer of polyamide film can be formed on the surface of the nanofiltration membrane polytetrafluoroethylene, thereby obtaining a polyamide-PTFE composite nanofiltration membrane; the obtained polyamide-PTFE composite nanofiltration membrane is placed in a 50°C oven for drying for 5 minutes; the dried polyamide-PTFE composite nanofiltration membrane is washed with deionized water for multiple times and stored in deionized water to maintain a sterile environment.

[0045] (2) Method for extracting o-methylphenol from coal tar using polyamide-PTFE composite nanofiltration membrane

[0046] First, the polyamide-PTFE composite nanofiltration membrane was soaked in isopropanol solution to remove the air in the membrane; the polyamide-PTFE composite nanofiltration membrane was placed in the permeation pool of the organic solvent-resistant nanofiltration membrane evaluation device with a cold trap circulation pump, and the effective area of ​​the polyamide-PTFE composite nanofiltration membrane was recorded as A: o-cresol and toluene model oils with good concentrations were added to the stock solution bottle, and the model oil was stirred evenly and the temperature was stabilized at 25°C before being used to simulate coal tar. The o-cresol concentration in the model oil was marked as Cp; the stock solution bottle and the nanofiltration were placed in a permeation pool, and the effective area of ​​the polyamide-PTFE composite nanofiltration membrane was recorded as A. The permeation pool of the membrane evaluation device is connected and its sealing is checked; the cold trap circulation pump is turned on, and the nanofiltration membrane evaluation device is operated to stabilize the permeation pressure of the polyamide-PTFE composite nanofiltration membrane at 0.1-4 bar, and the permeation time of the model oil in the stock solution bottle in the polyamide-PTFE composite nanofiltration membrane is recorded as t; after running for a period of time, the nanofiltration membrane evaluation device and the cold trap circulation pump are turned off, and the volume of the liquid that permeates through the polyamide-PTFE composite nanofiltration membrane in the permeation pool is recorded as V, and the concentration of o-methylphenol in the permeate is recorded as C fRepeat steps (3) and (4) for multiple times, and take the average value of the obtained data; use gas chromatograph to analyze the concentration of o-methylphenol in the permeate, and calculate the permeation flux and retention rate of the polyamide-PTFE composite nanofiltration membrane. The retention rate of p-methylphenol was measured to be 54.23%, and the permeation flux was 19.1m -2 bar -1 ·s -1 The concentration of o-cresol in the o-cresol and toluene model coal tar mixed solution is 100 g / L.

[0047] Example 2

[0048] The difference from Example 1 is that the mass concentration ratio of polyethyleneimine to piperazine in the preparation process of the polyamide-PTFE composite nanofiltration membrane is 1:0.1, and the retention rate of o-cresol is 60.6%, and the permeation flux is 18.9 m -2 bar -1 ·s -1 .

[0049] Example 3

[0050] The difference from Example 1 is that the raw material liquid temperature was stabilized at 20°C during the evaluation of the polyamide-PTFE composite nanofiltration membrane, and the retention rate of o-cresol was 55.61%, and the permeation flux was 19.1 m -2 bar -1 ·s -1 .

[0051] Example 4

[0052] The difference from Example 1 is that the raw material liquid temperature was stabilized at 30°C during the evaluation of the polyamide-PTFE composite nanofiltration membrane, and the retention rate of o-cresol was 55.98%, and the permeation flux was 18.2 m -2 bar -1 ·s -1 .

[0053] Example 5

[0054] The difference from Example 1 is that during the evaluation of the polyamide-PTFE composite nanofiltration membrane, the concentration of o-cresol in the raw material liquid was prepared to 50 g / L for evaluation, and the retention rate of o-cresol was measured to be 54.34%, and the permeation flux was 17.28 m -2 bar -1 ·s -1 .

[0055] Example 6

[0056] The difference from Example 1 is that during the evaluation of the polyamide-PTFE composite nanofiltration membrane, the concentration of o-cresol in the raw material liquid was prepared to 80 g / L for evaluation, and the retention rate of o-cresol was measured to be 58.48%, and the permeation flux was 18.1 m -2 bar -1 ·s -1 .

[0057] like Figure 1 The XRD pattern of polyamide-PTFE composite nanofiltration membrane is shown in Figure 2. Figure 1 It can be seen that the polyamide-PTFE composite nanofiltration membrane has high strength, so it has high crystallinity, and there is no obvious difference in the diffraction peaks, which verifies that the formation of the polyamide layer has no effect on the crystal structure of polytetrafluoroethylene.

[0058] like Figure 2 The FTIR spectrum of polyamide-PTFE composite nanofiltration membrane is shown. Figure 2 It can be seen that the characteristic peak of polyamide-PTFE composite nanofiltration membrane is 3395cm -1 The stretching vibration of hydrogen bond -OH and C=O amide group appears, with the characteristic peak at 1625cm -1 The bands correspond to the stretching vibration of the -CONH- functional group, which indicates that the polyamide layer has been formed on the nanofiltration membrane polytetrafluoroethylene.

[0059] like Figure 3 The long-term stability spectrum of polyamide-PTFE composite nanofiltration membrane is shown. Figure 3 It can be seen that after 15 consecutive days of operation, the permeation flux and the retention rate of o-cresol of the polyamide-PTFE composite nanofiltration membrane fluctuated slightly, but remained basically unchanged, which verified that the polyamide-PTFE composite nanofiltration membrane has good long-term stability.

Claims

1. A polyamide-PTFE composite nanofiltration membrane, Features: The polyamide-PTFE composite nanofiltration membrane includes a separation layer and a support layer. The separation layer is a polyamide membrane prepared on the support layer by mixing polyethyleneimine, piperazine, trimesic acid chloride and n-hexane solution by reverse interfacial polymerization. The mass concentration ratio of polyethyleneimine to piperazine is 1:0.2-1:1, the thickness of the separation layer is 20-200nm, and the area of ​​the separation layer is 5-100cm 2 ; The supporting layer is a polytetrafluoroethylene nanofiltration membrane, and the molecular weight cutoff of the polytetrafluoroethylene nanofiltration membrane is 200-2000Dal.

2. A method for preparing a polyamide-PTFE composite nanofiltration membrane according to claim 1, It is characterized in that The following steps are involved: Step (1): soaking the nanofiltration membrane polytetrafluoroethylene in a hexane solution dissolved with trimesoyl chloride; Step (2): pouring a mixed amine aqueous solution of polyethyleneimine and piperazine onto the surface of the soaked nanofiltration membrane polytetrafluoroethylene to initiate an interfacial polymerization reaction, thereby forming a polyamide film on the nanofiltration membrane polytetrafluoroethylene, thereby obtaining a polyamide-PTFE composite nanofiltration membrane; Step (3): drying the obtained polyamide-PTFE composite nanofiltration membrane in an oven; Step (4): After the dried polyamide-PTFE composite nanofiltration membrane is washed with deionized water for multiple times, it is stored in deionized water to maintain a sterile environment.

3. A method for preparing a polyamide-PTFE composite nanofiltration membrane as claimed in claim 2, Features: In step (1), the concentration of trimesic acid chloride in the n-hexane solution is 0.6 g / L.

4. A method for preparing a polyamide-PTFE composite nanofiltration membrane as claimed in claim 2, Features: In step (2), the mass concentration ratio of polyethyleneimine to piperazine is 1:0.1-1:

1.

5. The method for extracting o-methylphenol from coal tar using a polyamide-PTFE composite nanofiltration membrane according to claim 1, Features: The following steps are involved: Step (1): first, soak the polyamide-PTFE composite nanofiltration membrane with isopropanol to remove the air in the membrane; then install the polyamide-PTFE composite nanofiltration membrane into a permeation tank of an organic solvent-resistant nanofiltration membrane evaluation device equipped with a cold trap circulation pump, and the effective area of ​​the polyamide-PTFE composite nanofiltration membrane is recorded as A; Step (2): Add the prepared concentration of o-cresol and toluene model oil into the stock solution bottle, stir the model oil evenly and stabilize the temperature at 20-30° C. before using it to simulate coal tar. The o-cresol concentration in the model oil is marked as Cp; Step (3): connecting the stock solution bottle to the permeation cell of the organic solvent-resistant nanofiltration membrane evaluation device and checking its sealing; Turn on the cold trap circulation pump, operate the nanofiltration membrane evaluation device to stabilize the permeation pressure of the polyamide-PTFE composite nanofiltration membrane at 0.1-4 bar, start timing and record the permeation time of the model oil in the stock solution bottle in the polyamide-PTFE composite nanofiltration membrane as t; Step (4): After running for a period of time, the nanofiltration membrane evaluation device and the cold trap circulation pump are turned off, and the volume of the liquid that permeates through the polyamide-PTFE composite nanofiltration membrane in the permeation pool is recorded as V, and the concentration of o-methylphenol in the permeate is recorded as C f ; Step (5): Repeat steps (3) and (4) for multiple times, and take the average value of the obtained data; Step (6): analyzing the concentration of o-methylphenol in the permeate by gas chromatography, and calculating the permeation flux and retention rate of the polyamide-PTFE composite nanofiltration membrane; The two important parameters for evaluating the adsorption of o-methylphenol by polyamide-PTFE composite nanofiltration membrane are permeation flux and retention rate, and the calculation formula is: Permeation flux: P = V / (A × Δp × t) Retention rate: R = (1-C P / C f )×100% V is the volume of permeate, L ΔP represents the osmotic pressure, bar T is the penetration time, s A represents the effective area of ​​polyamide-PTFE composite nanofiltration membrane, m 2 C p Indicates the concentration of o-cresol in the model oil, g / L C f It represents the concentration of o-cresol in the permeate, g / L.

6. A method for extracting o-methylphenol from coal tar using a polyamide-PTFE composite nanofiltration membrane as claimed in claim 5, Features: The concentration of o-cresol in the model oil is 50-100 g / L.

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