Polyamide composite membrane, preparation method and method for extracting phenol from coal tar by adopting polyamide composite membrane

Abstract

The invention discloses a polyamide composite membrane, a preparation method and a method for extracting phenol from coal tar by adopting the polyamide composite membrane, the polyamide composite membrane comprises a supporting layer and a separation layer coated on the surface of the supporting layer, the supporting layer is a polytetrafluoroethylene nanofiltration membrane, the separation layer is a polyamide membrane, and the separation layer is a polyamide membrane. Active sites are provided for phenol molecules, so that phenol can be adsorbed on the surface of the polyamide membrane. The polyamide composite membrane prepared by the invention shows excellent nanofiltration performance in both an aqueous solution and an organic solution. The rejection rate of the polyamide composite membrane to phenol can reach about 26.1-51.2%, and the permeability of an organic solvent can reach 20-30 L.m <-2 >. Bar <-1 >. S <-1 >. In addition, the polyamide composite membrane is high in stability, and the interception performance can be kept stable under 10-day continuous operation.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a polyamide composite membrane, a preparation method and a method for extracting phenol from coal tar by using the polyamide composite membrane. Background Art

[0002] Coal tar or coal direct liquefaction oil is a complex mixture of tens of thousands of components. For example, more than 500 single compounds have been separated and identified from coal tar, including 63 acidic components such as phenol, naphthol and alkylphenol. Phenolic substances in coal tar or coal direct liquefaction oil account for about 10% to 30% of its total mass. The presence of these phenolic substances has an adverse effect on their subsequent processing. For example, when coal tar is hydrogenated to produce light oil, the presence of phenolic compounds will increase the consumption of hydrogen, and the water generated by the hydrogenation of phenolic compounds will affect the activity and life of the catalyst, thereby affecting the economy of the entire hydrogenation production process. In addition, the valuable components in phenolic compounds have not been effectively utilized, which not only reduces the added value of coal tar, but also wastes natural resources. Among them, phenol and its related o-, m- and p-cresol isomers, commonly known as hydroxytoluene or methylphenol, are members of the aromatic organic compounds and are used as raw materials for the synthesis of an expanding range of industrial organic chemicals. Therefore, it is valuable to separate them from neutral oils.

[0003] At present, the common coal tar phenol extraction technology can be divided into two categories: one is physical methods such as extraction separation, adsorption separation, crystallization separation; the other is chemical methods such as complexation, hydrocarbonization, and chelation. 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.

[0004] Since coal tar has complex composition, a mixed solution of phenol and toluene was used as model coal tar to reduce the difficulty of analysis. Summary of the invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a polyamide composite membrane, a preparation method and a method for extracting phenol from coal tar using the polyamide composite membrane, prepare the polyamide composite membrane by interfacial polymerization and extract phenol from coal tar, and perform nanofiltration membrane method on phenol and toluene simulated coal tar solution to extract phenol. The present invention uses polyethyleneimine and piperazine complex reaction to prepare polyamide with selective adsorption of phenol, because the molecular surface of the polyamide composite membrane contains high-density π bonds, which can form hydrogen bonds with phenol, so that phenol can be adsorbed on the polyamide composite membrane, thereby achieving the effect of efficient and green phenol extraction.

[0006] To achieve the above purpose, the present invention adopts the following technical solution:

[0007] A polyamide composite membrane, comprising a support layer and a separation layer coated on the surface of the support layer, wherein the support layer is a polytetrafluoroethylene nanofiltration membrane, the molecular weight cutoff of the polytetrafluoroethylene nanofiltration membrane is 200-2000Da, and the thickness of the support layer is 60-120nm; the separation layer is a polyamide membrane, the thickness of the separation layer is 20-200nm, and the area of ​​the separation layer is 5-100cm 2 .

[0008] The method for preparing a polyamide composite membrane is to prepare the polyamide composite membrane by interfacial polymerization, comprising the following steps:

[0009] Step (1): soaking the nanofiltration membrane polytetrafluoroethylene with a mixed amine aqueous solution of polyethyleneimine and piperazine to form a polyamide film on the surface of the nanofiltration membrane polytetrafluoroethylene, thereby obtaining a polyamide composite membrane;

[0010] Step (2): removing the residual droplets on the surface of the polyamide composite membrane, and reacting the polyamide composite membrane with trimesic acid chloride in n-hexane solvent to obtain a defect-free polyamide composite membrane;

[0011] Step (3): placing the defect-free polyamide composite film in an oven for drying;

[0012] Step (4): The prepared polyamide composite membrane is washed with deionized water for multiple times and stored in deionized water to maintain a sterile environment.

[0013] In step (1), 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.

[0014] In step (2), the concentration of trimesic acid chloride in n-hexane solvent is 0.5 g / L. At this concentration, the defect repair of the polyamide composite membrane is the best.

[0015] The method for extracting phenol from coal tar using a polyamide composite membrane, wherein the polyamide composite membrane provides active sites for phenol molecules, and enables phenol to be adsorbed on the surface of the polyamide composite membrane, comprises the following steps:

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

[0017] Step (2): Add phenol and toluene, phenol and n-hexane model oils of prepared concentrations into the stock solution bottle, stir the model oils evenly and stabilize the temperature at 20-30° C. before using them to simulate coal tar. The phenol concentration in the model oils 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 composite membrane at 0.1-4 bar, and start recording the permeation time of the model oil in the stock solution bottle in the polyamide composite membrane as t;

[0019] Step (4): After running for a period of time, turn off the organic solvent resistance nanofiltration membrane evaluation device and the cold trap circulation pump, record the volume of the liquid that permeates the polyamide composite membrane in the permeation cell as V, and the phenol concentration in the permeate 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): analyzing the concentration of phenol in the permeate by gas chromatography, and calculating the permeation flux and retention rate of the polyamide composite membrane;

[0022] The two important parameters for evaluating the adsorption of phenol by polyamide composite membranes are permeation flux and rejection 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 ​​the polyamide composite membrane, m 2

[0029] C p Indicates the phenol concentration in the model oil, g / L

[0030] C f Indicates the concentration of phenol in the permeate, g / L.

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

[0032] The preparation method of the present invention is stable and reliable. The polyamide composite membrane can adsorb phenol in coal tar well and has high stability. The permeation flux of the polyamide composite membrane can reach 20-30L·m -2 bar -1 ·s -1 The interception rate of phenol can reach 26.10-51.16%. The interception performance of phenol can be kept stable under continuous operation for 10 days, which has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the XRD pattern of polyamide composite film.

[0034] Figure 2 It is the FTIR spectrum of polyamide composite membrane.

[0035] Figure 3 It is the long-term stability spectrum of polyamide composite membrane. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] The invention provides a polyamide composite membrane, a preparation method and a method for extracting phenol from coal tar using the polyamide composite membrane. The polyamide 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.

[0038] Example 1

[0039] (1) The preparation method of the polyamide composite film is as follows:

[0040] The nanofiltration membrane polytetrafluoroethylene is soaked in a mixed amine aqueous solution of 12.5 g / L polyethyleneimine and 12.5 g / L piperazine for 2 minutes to form a polyamide film on the surface of the nanofiltration membrane polytetrafluoroethylene, thereby obtaining a polyamide composite membrane; the residual droplets on the surface of the polyamide composite membrane are removed, and the polyamide composite membrane is reacted with 0.5 g / L benzyl chloride in a n-hexane solvent for 1 minute to obtain a defect-free polyamide composite membrane; the polyamide composite membrane is placed in a 50°C oven for drying; the prepared polyamide composite membrane is washed with deionized water for multiple times and stored in deionized water to maintain a sterile environment; before each evaluation of the polyamide composite membrane, all polyamide composite membranes are soaked in isopropanol to exclude air from the polyamide composite membrane.

[0041] (2) Method for extracting phenol from coal tar using polyamide composite membrane

[0042] First, the polyamide composite membrane is soaked in isopropanol to remove the air in the polyamide composite membrane, and then the polyamide composite membrane is placed in a permeation pool of an organic solvent-resistant nanofiltration membrane evaluation device with a cold trap circulation pump, and the effective area of ​​the polyamide composite membrane is recorded as A; phenol and toluene model oils with good concentrations are placed in a stock solution bottle, and the model oils are stirred evenly and the temperature is stabilized at 20°C before being used to simulate coal tar, and the phenol concentration in the model oil is marked as Cp; the stock solution bottle is connected to the permeation pool of the organic solvent-resistant nanofiltration membrane evaluation device and its sealing is checked; the cold trap circulation pump is turned on, the nanofiltration membrane evaluation device is operated to stabilize the permeation pressure of the polyamide composite membrane at 0.1-4bar, and the permeation time of the model oil in the stock solution bottle in the polyamide composite membrane is recorded as tt; 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 composite membrane in the permeation pool, i.e., the permeate, is recorded as V, and the phenol concentration in the permeate is recorded as C f Repeat steps (3) and (4) for multiple times, and take the average value of the obtained data; use gas chromatograph to analyze the phenol concentration in the permeate, and calculate the permeate flux and retention rate of the polyamide composite membrane. The phenol concentration in the phenol and toluene model oil mixture is 100 g / L.

[0043] Example 2

[0044] The difference from Example 1 is that the mass concentration ratio of polyethyleneimine and piperazine in the preparation process of the polyamide composite membrane is 1:0.1, and the retention performance is tested.

[0045] Example 3

[0046] The difference from Example 1 is that during the evaluation process of extracting phenol from coal tar with a polyamide composite membrane, the model oil was evenly stirred and the temperature was stabilized at 25° C. before evaluation to observe the effect of the polyamide composite membrane on the phenol retention performance at different temperatures.

[0047] Example 4

[0048] The difference from Example 1 is that during the evaluation process of extracting phenol from coal tar with a polyamide composite membrane, the model oil was evenly stirred and the temperature was stabilized at 30° C. before evaluation to observe the effect of the polyamide composite membrane on the phenol retention performance at different temperatures.

[0049] Example 5

[0050] The difference from Example 1 is that during the evaluation of the polyamide composite membrane extracting phenol from coal tar, the phenol concentration in the model oil was prepared to be 50 g / L before evaluation, and the effect of the polyamide composite membrane on the phenol retention performance at different phenol concentrations was observed.

[0051] Example 6

[0052] The difference from Example 1 is that during the evaluation of the polyamide composite membrane extracting phenol from coal tar, the phenol concentration in the model oil was prepared to be 100 g / L before evaluation, and the effect of the polyamide composite membrane on the phenol retention performance at different phenol concentrations was observed.

[0053] The performance of the polyamide composite membrane was evaluated according to the above implementation case, and the permeation flux and retention rate of each polyamide composite membrane of Examples 1-6 were measured. The specific results are shown in Table 1:

[0054] Table 1

[0055]

[0056] As can be seen from Table 1, as the ratio of polyethyleneimine to piperazine of the polyamide composite membrane prepared by the present invention increases, its permeation flux becomes lower and its retention rate for phenol becomes higher, and under the conditions of Implementation Case 1, the retention rate for phenol by the nanofiltration membrane of the present invention is the largest, that is, the polytetrafluoroethylene nanofiltration membrane has the best selectivity for phenol.

[0057] like Figure 1 The XRD pattern of the polyamide composite film is shown in Figure 2. Figure 1 It can be seen that the polyamide composite film 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 the polyamide composite membrane is shown. Figure 2 It can be seen that the characteristic peak of the polyamide composite membrane is 3395cm -1 The stretching vibration of hydrogen bond -OH appears, with a characteristic peak at 1550cm -1 The band corresponds to the bending vibration of the NH group, with a characteristic peak at 1625 cm -1 The band corresponds to the stretching vibration of the -CONH- functional group, which indicates that the polyamide layer has been formed on the base film.

[0059] like Figure 3 The long-term stability of polyamide composite membranes is shown in Figure 2. Figure 3 It can be seen that after 10 consecutive days of operation, the permeation flux and the retention rate of phenol of the polyamide composite membrane fluctuated slightly, but remained basically unchanged, which verified that the polyamide composite membrane has good long-term stability.

Claims

1. A polyamide composite film, characterized in that: The polyamide composite membrane comprises a support layer and a separation layer coated on the surface of the support layer. The support layer is a polytetrafluoroethylene nanofiltration membrane with a molecular weight cutoff of 200-2000Da and a thickness of 60-120nm. The separation layer is a polyamide membrane with a thickness of 20-200nm and an area of ​​5-100cm 2 .

2. The method for preparing a polyamide composite film according to claim 1, characterized in that: The method for preparing a polyamide composite membrane by an interfacial polymerization method comprises the following steps: Step (1): soaking the nanofiltration membrane polytetrafluoroethylene with a mixed amine aqueous solution of polyethyleneimine and piperazine to form a polyamide film on the surface of the nanofiltration membrane polytetrafluoroethylene, thereby obtaining a polyamide composite membrane; Step (2): removing the residual droplets on the surface of the polyamide composite membrane, and reacting the polyamide composite membrane with trimesic acid chloride in n-hexane solvent to obtain a defect-free polyamide composite membrane; Step (3): placing the defect-free polyamide composite film in an oven for drying; Step (4): The prepared polyamide composite membrane is washed with deionized water for multiple times and stored in deionized water to maintain a sterile environment.

3. The method for preparing a polyamide composite film according to claim 2, characterized in that: In step (1), the mass concentration ratio of polyethyleneimine to piperazine is 1:0.1-1:

1.

4. The method for preparing a polyamide composite film according to claim 2, characterized in that: In step (2), the concentration of trimesic acid chloride in n-hexane solvent is 0.5 g / L.

5. The method for extracting phenol from coal tar using the polyamide composite membrane according to claim 1, characterized in that: The polyamide composite membrane provides active sites for phenol molecules, so that phenol can be adsorbed on the surface of the polyamide composite membrane, comprising the following steps: Step (1): first, soak the polyamide composite membrane in isopropanol to remove the air in the polyamide composite membrane, and then install the polyamide composite membrane into a permeation cell of an organic solvent-resistant nanofiltration membrane evaluation device equipped with a cold trap circulation pump, and the effective area of ​​the polyamide composite membrane is recorded as A; Step (2): Add phenol and toluene or phenol and n-hexane model oils of a certain concentration into the stock solution bottle, stir the model oils evenly and stabilize the temperature at 20-30° C. before using them to simulate coal tar. The phenol concentration in the model oils is marked as Cp. 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 composite membrane at 0.1-4 bar, and start recording the permeation time of the model oil in the stock solution bottle in the polyamide composite membrane as t; Step (4): After running for a period of time, turn off the organic solvent resistance nanofiltration membrane evaluation device and the cold trap circulation pump, record the volume of the liquid that permeates the polyamide composite membrane in the permeation cell as V, and the phenol concentration in the permeate 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 phenol in the permeate by gas chromatography, and calculating the permeation flux and retention rate of the polyamide composite membrane; The two important parameters for evaluating the adsorption of phenol by polyamide composite membranes are permeation flux and rejection 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 ​​the polyamide composite membrane, m 2 C p Indicates the phenol concentration in the model oil, g / L C f Indicates the concentration of phenol in the permeate, g / L.

6. The method for extracting phenol from coal tar using a polyamide composite membrane as claimed in claim 5, characterized in that: The phenol concentration in the model oil is 50-100 g / L.

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