A kind of organic silicon composite membrane for aromatic hydrocarbon / alkane organic solvent system separation and its preparation method and application
By preparing organosilicon composite membranes, the problems of insufficient selectivity and permeability of polymer membranes are solved by utilizing the π-π interaction and pore-filling effect of aryl groups, thus achieving efficient and stable separation of aromatics and alkanes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2023-01-18
- Publication Date
- 2026-07-14
AI Technical Summary
Existing polymer membranes suffer from low selectivity and poor permeability in the separation of aromatics and alkanes. Furthermore, hybrid membranes are prone to filler loss and interface defects during long-term service, making it difficult to achieve efficient separation.
Organosilicon composite membranes were prepared by co-condensation of organosilicon composite gels and loaded onto an alumina support. By utilizing the π-π interaction and pore-filling effect of different aryl groups, organosilicon composite membranes with stable structure and adjustable pore size were prepared.
It achieves efficient separation of aromatics and alkanes, increases permeate flux, improves separation factor, and enhances membrane structure stability, avoiding the defects of traditional membrane materials.
Smart Images
Figure QLYQS_1 
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane technology for separating organic solvents, and specifically relates to an organosilicon composite membrane for separating aromatic / alkane organic solvent systems, its preparation method, and its application. Background Technology
[0002] For a long time, my country's ethylene production capacity has grown slowly, resulting in a significant supply-demand gap and a high dependence on imports for downstream ethylene derivatives. Naphtha is the main raw material for ethylene production in my country, accounting for over 60%. It is generally believed that only when the alkane content in naphtha exceeds 65% can the requirements for steam cracking to produce ethylene be met; at the same time, significantly reducing the proportion of aromatics in naphtha can effectively avoid problems such as coking in the cracking furnace and low ethylene conversion rate. However, aromatics and alkanes have diverse molecular structures, extremely similar physical properties, and easily form azeotropes, making separation difficult. To date, traditional aromatic / alkane separation technologies (such as azeotropic distillation and extractive distillation) have dominated, but they often face problems such as low selectivity and high energy consumption in aromatic / alkane separation.
[0003] Membrane separation is a highly efficient, low-energy-consumption, and environmentally friendly separation method with promising applications. Currently, reported aromatic / alkane separation membranes are mainly polymer membranes and hybrid membranes. Given that aromatic molecules possess delocalized π electrons, polymer membranes are primarily made from polymer membrane materials containing strongly polar groups or benzene ring structures, utilizing their strong π electron accepting ability to enhance the dissolution of aromatic molecules within the membrane. However, polymer membranes are typically dense, have poor permeability, and exhibit a trade-off between selectivity and permeability in their separation characteristics. Furthermore, the chain segment movement phenomenon in organic solvent environments, and the resulting swelling and loss of selectivity, are difficult to avoid, limiting their practical application. In contrast, hybrid membranes introduce fillers with strong aromatic affinity into polymer membrane materials, which can enhance the dissolution capacity of aromatic molecules while constructing a multi-microchannel system conducive to the rapid transport of aromatic molecules, synergistically improving their diffusion capacity. However, due to the significant differences in physicochemical properties and structural morphology between the filler and the polymer membrane substrate, the bonding force between the filler and the polymer is weak, and the microstructure of hybrid membranes often exhibits phenomena such as filler agglomeration and interfacial defects. Furthermore, hybrid membranes are prone to filler loss during long-term service, posing a significant challenge to the preparation of stable hybrid membranes. Therefore, the design and controllable construction of novel membrane materials with high aromatic / alkane selectivity and high permeation flux are key tasks for achieving membrane-based aromatic / alkane separation. Summary of the Invention
[0004] The purpose of this invention is to provide an organosilicon composite membrane for the separation of aromatic / alkane organic solvent systems and its preparation method, thereby overcoming the limitations of existing polymer membrane materials to achieve efficient separation of aromatics / alkanes.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0006] An organosilicon composite membrane for the separation of aromatic / alkane organic solvent systems is obtained by the following method: using compounds of formula I and formula II as organosilicon precursors, the organosilicon composite membrane is prepared by co-condensation.
[0007]
[0008] Preferably, the mass ratio of compound BTESBP of formula I to compound PhTES of formula II is 10-50:1.
[0009] First, the compound of formula I and the compound of formula II are made into an organosilicon composite gel, which is then loaded onto a support and subsequently calcined.
[0010] Furthermore, in the preparation of organosilicon composite gel, the compounds of formula I and formula II are first dissolved in ethanol, N-methylpyrrolidone or tetrahydrofuran and mixed thoroughly, and then water and acid are added in sequence to carry out the reaction.
[0011] The total concentration of organosilicon precursor in the organosilicon composite gel is preferably 0.1-0.5 wt%.
[0012] In the aforementioned organosilicon composite gel, the molar ratio of organosilicon precursor: acid: water is 1:0.1:60-240, and the reaction is carried out at 30-50℃ for 1-3 hours.
[0013] The acid required for the preparation of the organosilicon composite gel can be one of hydrochloric acid, nitric acid, or phosphoric acid.
[0014] Furthermore, using alumina as a carrier, a gel intermediate layer is first coated on it, and then calcined in air at a temperature of 600-800℃ for 10-30 minutes.
[0015] The alumina membrane carrier is tubular or sheet-like, with a gel interlayer pre-coated on it. This interlayer can be silica gel, zirconium dioxide gel, or a mixture of both. Preferably, it is a mixture of silica and zirconium dioxide in an equimolar ratio.
[0016] The organosilicon composite gel was then loaded onto the carrier with the intermediate layer, and then calcined at 300-600℃ for 1-3 hours under inert gas protection.
[0017] The inert protective gas can be any one of nitrogen, helium, or argon.
[0018] Specifically, the preparation of the aforementioned organosilicon composite film includes the following steps:
[0019] (1) Preparation of organosilicon composite gel: Dissolve BTESBP and PhTES organosilicon precursors simultaneously in anhydrous ethanol. Stir magnetically at room temperature for 5-10 min, then add water and acid dropwise. Transfer the mixture to a water bath and react at 30-50℃ for 1-3 h. Finally, continue to add anhydrous ethanol to dilute the concentration of organosilicon precursor to 0.1-0.5 wt%.
[0020] (2) Pretreatment of alumina carrier: A gel intermediate layer is coated on the alumina carrier and calcined in air at a temperature of 600-800℃ for 10-30 minutes.
[0021] (3) Preparation of organosilicon composite membrane: The organosilicon composite gel obtained in (1) is coated on the alumina carrier pretreated in (2) and quickly transferred to a tube furnace for calcination. Under inert gas protection, it is calcined for 1-3 hours.
[0022] The obtained organosilicon composite membrane has excellent applications in the separation of aromatic / alkane organic solvent systems.
[0023] This invention employs two organosilicon precursors containing different aryl groups and with different spatial configurations to prepare the organosilicon composite membrane through a co-condensation strategy. This invention also proposes for the first time the use of organosilicon composite membranes to separate aromatic / alkane systems. First, an organosilicon composite solution is prepared via a sol-gel process, then coated onto an alumina support, and subsequently, a calcination crosslinking process is performed to prepare a structurally stable organosilicon composite membrane with adjustable pore size. Choosing the aryl-containing organosilicon precursor of this invention for aromatic / alkanes separation offers multiple advantages: the strong π-π interaction between aryl groups and aromatic molecules effectively enhances the dissolution of aromatic molecules within the membrane; simultaneously, the π-π interaction between different aryl groups contributes to improving the overall membrane stability, effectively suppressing structural shrinkage and swelling of the membrane in organic solvent systems; assembling PhTES molecules into the BTESBP-derived organosilicon network allows for precise control of the membrane microstructure, utilizing the unique pore-filling effect of the benzene ring end groups on the PhTES molecule to effectively adjust the macropore size and optimize the pore size distribution within the membrane; furthermore, the steric hindrance effect of the benzene ring end groups helps break the short-range ordered π-π stacking units within the membrane, increasing the overall porosity and free volume of the membrane. In summary, the organosilicon composite membrane prepared by this invention improves the accessibility between aromatic molecules and the aryl groups within the membrane pores, while simultaneously enhancing the sieving characteristics of the membrane pores, thereby achieving highly efficient separation of aromatics and alkanes. In addition, the preparation process of organosilicon composite gel is simple and fast, the conditions are mild, the cost is low, the required solvent has low toxicity, and the film formation has high repeatability. Attached Figure Description
[0024] Figure 1 This is a test graph showing the long-term separation performance of the organosilicon composite membrane obtained in Example 1 of the present invention.
[0025] Figure 2 This is a SEM image of the cross-section of the organosilicon composite film obtained in Example 2 of the present invention. Detailed Implementation
[0026] The technical solution of the present invention is illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto:
[0027] Example 1
[0028] A method for preparing an organosilicon composite membrane for separating aromatic / alkane organic solvent systems, comprising the following steps:
[0029] 1) Weigh 0.196 g of BTESBP and 0.004 g of PhTES, respectively, and dissolve them simultaneously in 7.858 g of anhydrous ethanol (99.5% by volume). Stir magnetically at room temperature for 5 min, adding 1.896 g of deionized water and 0.045 g of dilute hydrochloric acid solution dropwise during stirring. Transfer the mixture to a water bath and continue stirring at 50 °C for 1 h. After the reaction is complete, add anhydrous ethanol to dilute the concentration of the organosilicon precursor to 0.25 wt% to obtain the BTESBP / PhTES organosilicon composite gel. In this example and in the following examples, dilute hydrochloric acid refers to a solution obtained by diluting commercially available concentrated hydrochloric acid 100 times with anhydrous ethanol.
[0030] 2) Coat a tubular alumina carrier with a mixed aqueous solution of silica and zirconium dioxide (molar ratio 1:1), calcine at 600°C for 10 min in air atmosphere, and then cool to room temperature.
[0031] 3) The alumina support was placed in an oven at 200℃ for 30 min, then coated with BTESBP / PhTES silicone composite gel, and quickly transferred to a tube furnace. It was calcined at 450℃ for 1 h under a nitrogen atmosphere, and then cooled to room temperature. The resulting silicone composite film was labeled BTESBP / PhTES-1.
[0032] Example 2
[0033] A method for preparing an organosilicon composite membrane for separating aromatic / alkane organic solvent systems, comprising the following steps:
[0034] 1) Weigh 0.190 g of BTESBP and 0.010 g of PhTES, respectively, and dissolve them simultaneously in 8.806 g of anhydrous ethanol. Stir magnetically for 5 min at room temperature, then add 0.948 g of deionized water and 0.045 g of dilute hydrochloric acid solution dropwise while stirring. Transfer the mixture to a water bath and continue stirring at 50 °C for 1 h. After the reaction is complete, add anhydrous ethanol to dilute the concentration of the organosilicon precursor to 0.25 wt%.
[0035] 2) Coat a tubular alumina carrier with a 0.5 wt% aqueous solution of silica and zirconium dioxide in a molar ratio of 1:1, and calcine at 600°C for 30 min in an air atmosphere, and then cool to room temperature.
[0036] 3) The alumina support was placed in an oven at 200℃ for 30 min, then coated with BTESBP / PhTES silicone composite gel, and quickly transferred to a tube furnace. It was calcined at 450℃ for 1 h under a nitrogen atmosphere, and then cooled to room temperature. The resulting silicone composite film was labeled BTESBP / PhTES-2.
[0037] Example 3
[0038] A method for preparing an organosilicon composite membrane for separating aromatic / alkane organic solvent systems includes the following specific steps:
[0039] 1) Weigh 0.184 g of BTESBP and 0.016 g of PhTES, respectively, and dissolve them simultaneously in 7.858 g of anhydrous ethanol. Stir magnetically for 5 min at room temperature, then add 1.896 g of deionized water and 0.045 g of dilute hydrochloric acid solution dropwise while stirring. Transfer the mixture to a water bath and continue stirring at 50 °C for 1 h. After the reaction is complete, add anhydrous ethanol to dilute the concentration of the organosilicon precursor to 0.25 wt%.
[0040] 2) Same as step 2 in Example 2).
[0041] 3) The alumina support was placed in an oven at 200℃ for 30 min, then coated with BTESBP / PhTES silicone composite gel, and quickly transferred to a tube furnace. It was calcined at 450℃ for 1 h under a nitrogen atmosphere, and then cooled to room temperature. The resulting silicone composite film was labeled BTESBP / PhTES-3.
[0042] Comparative Example 1
[0043] The preparation steps of pure-phase BTESBP silicone membrane are as follows:
[0044] 1) Weigh 0.2 g of BTESBP and dissolve it in 7.858 g of anhydrous ethanol. Stir magnetically for 5 min at room temperature, then add 1.896 g of deionized water and 0.045 g of dilute hydrochloric acid solution dropwise during stirring. Transfer the mixture to a water bath and continue stirring at 50 °C for 1 h. After the reaction is complete, add anhydrous ethanol to dilute the organosilicon precursor concentration to 0.25 wt%.
[0045] 2) Same as step 2 in Example 1.
[0046] 3) The alumina support was placed in an oven at 200℃ for 30 min, then coated with BTESBP silicone gel and quickly transferred to a tube furnace. It was calcined at 300℃ for 1 h under a nitrogen atmosphere and then cooled to room temperature. The resulting silicone film was labeled BTESBP-1.
[0047] Comparative Example 2
[0048] The preparation steps of pure-phase BTESBP silicone membrane are as follows:
[0049] 1) Same as Comparative Example 1, Step 1).
[0050] 2) Same as step 2 in Example 1.
[0051] 3) The alumina support was placed in an oven at 200℃ for 30 min, then coated with BTESBP silicone gel and quickly transferred to a tube furnace. It was calcined at 450℃ for 1 h under a nitrogen atmosphere and then cooled to room temperature. The resulting silicone film was labeled BTESBP-2.
[0052] Comparative Example 3
[0053] The preparation steps of pure-phase BTESBP silicone membrane are as follows:
[0054] 1) Same as Comparative Example 1, Step 1).
[0055] 2) Same as step 2 in Example 2).
[0056] 3) The alumina support was placed in an oven at 200℃ for 30 min, then coated with BTESBP silicone gel and quickly transferred to a tube furnace. It was calcined at 450℃ for 1 h under a nitrogen atmosphere and then cooled to room temperature. The resulting silicone film was labeled BTESBP-3.
[0057] Table 1 shows the pervaporation flux, separation factor, and selectivity of the BTESBP / PhTES silicone composite membranes prepared in Examples 1-3 and the pure-phase BTESBP silicone membranes prepared in Comparative Examples 1-3 for the pervaporation separation of the toluene / n-heptane system.
[0058]
[0059]
[0060] As can be seen from Table 1, compared with the commercial PEBA2533 polymer membrane (Arkema, France) and the reported hybrid membrane (PVA-GO, prepared according to J.Membr.Sci.455(2014)113-120);
[0061] MOP-OH / BoltonW3000 was prepared according to AIChEJ.62(10)(2016)3706-3716; PEO360OHMA was prepared according to J.Membr.Sci.234(1)(2004)55-65; PVC / TiO2 was prepared according to PolymerBulletin 88,(2023)643-666). The organosilicon membrane maintains a high toluene / n-heptane separation capacity while also exhibiting advantages in permeation flux. The composite membrane prepared by condensing BTESBP and PhTES organosilicon precursors showed significantly improved separation characteristics; the permeation flux in Example 1 could be increased to 1.986 kg m³. -2 h -1 It is approximately 13 times that of Comparative Example 1, while the separation factor is comparable.
Claims
1. A method for preparing an organosilicon composite membrane for separating aromatic / alkane organic solvent systems, characterized in that, The organosilicon composite film was prepared by co-condensation using compounds of formula I and formula II as organosilicon precursors. ； The mass ratio of compound BTESBP of formula I to compound PhTES of formula II is 10-50:1; In this process, compound I and compound II are first dissolved in ethanol, N-methylpyrrolidone or tetrahydrofuran and mixed thoroughly. Then, water and acid are added sequentially to react and prepare organosilicon composite gel. The gel is then loaded onto a support and calcined. The total concentration of organosilicon precursor in the organosilicon composite gel is 0.1-0.5 wt%; the molar ratio of organosilicon precursor: acid: water is 1:0.1:60-240, and the reaction is carried out at 30-50℃ for 1-3 h. Using alumina as a carrier, the calcination is carried out at 300-600℃ for 1-3 hours under inert gas protection.
2. The method for preparing the organosilicon composite membrane for separating aromatic / alkane organic solvent systems as described in claim 1, characterized in that, First, coat the intermediate layer of gel onto the carrier and calcine it in air at a temperature of 600-800℃ for 10-30 minutes.
3. The organosilicon composite membrane for separating aromatic / alkane organic solvent systems obtained by the preparation method of claim 1 or 2.
4. The application of the organosilicon composite membrane according to claim 3 in the separation of aromatic / alkane organic solvent systems.