RU2414953C1 - Method of producing composite membranes with fullerene-containing polymer selective layer - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to method of producing composite membranes with fullerene-containing polymer selective layer to extract ethers in alkyl acetate hybrid process. Proposed method consists in forming selective diffusion polymer layer on microporous substrate. Microporous substrate is represented by microfiltration membrane from copolymer of vinylidene fluoride with lavsan-based tetrafluoroethylene. Selective layer is the mix of poly(phenylene oxide) and fullerene C₆₀. Selective layer is formed by applying 2%-solution of aforesaid mix onto surface of said microporous substrate and drying it.

EFFECT: composite membrane with improved transfer properties for extracting ethers.

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Description

The invention relates to the chemistry of macromolecular compounds and is intended to produce composite polymer pervaporation membranes, representing a multilayer product containing at least two layers. Such membranes can be used in chemical, petrochemical, pharmaceutical and other industries where it is necessary to separate mixtures of organic liquids containing aliphatic alcohols, ethers and esters, hydrocarbons (aliphatic, olefins, aromatic, cycloaliphatic and others) [M. Mulder. Introduction to membrane technology. M.: Mir, 1999, 513 p.]. One way to increase the efficiency of polymeric materials is to modify them with nanoparticles (zeolite, graphite, activated carbon, etc.). Fullerenes offer great opportunities for improving the membrane properties of polymeric materials.

Among the first composites studied as membranes was fullerene-containing polystyrene [G.A. Polotskaya et al. Study of solid-phase polystyrene-fullerene compositions. J. Tech. Physicists. 2002.V. 72. Issue 1. S.105-109]. Dispersion in a polystyrene matrix up to 2 wt.% Fullerene C ₆₀ increases the selectivity of the separation of the oxygen / nitrogen mixture with a slight decrease in membrane permeability compared to unmodified polymer. Asymmetric porous polyphenylene oxide membranes containing up to 10% C ₆₀ fullerene proved to be effective in ultrafiltration water purification from estrogenic impurities [X. Jin, JY Ni, ML Tint, SL Ong, Y. Biryulin and G. Polotskaya. Estrogenic compounds removal by fullerene-containing membranes. Desalination. 2007. V.214 (1-3). P. 83-90]. Supplements of fullerene accelerated the absorption of estrogens and ensured their high retention by the membrane during filtration.

In the literature there is a relatively large number of publications relating to the preparation and use of composite membranes. In the patent [US 5723639; 03.03.1998] "Esteriflcation of fermentation-derived acids via pervaporation" two types of membranes based on hydrophilic and hydrophobic polymers are used for pervaporation separation of esterification products of enzymatically obtained acids. As hydrophilic, industrial membranes GFT PerVap 1001 or 1005, GFT PerVap 2001, consisting of a selective layer of polyvinyl alcohol on a porous substrate made of polyester or polyacrylonitrile, as well as a TexSep 1B membrane, consisting of a non-porous layer of polyvinyl alcohol on a porous substrate resistant to organic acids, are used . As hydrophobic, a GFT PerVap 1170 membrane is used, consisting of a selective layer based on organosilicon rubber deposited on a microporous cellulose substrate. Other examples of hydrophobic compounds used as selective layers include styrene copolymers and styrene derivatives, polyetheramides and polytrimethylsilylpropine. The best results in the process of separation of esters from four-component equilibrium mixtures of the esterification reaction were shown by the GFT PerVap 1170 membrane.

A significant disadvantage of this composite membrane, according to the above examples, is the low productivity, which does not allow this process to compete with the already known methods for producing esters. It should be noted that among the polymeric materials used in the composite membranes for this process, polyphenylene oxide was not given.

The closest is the method for producing composite polymer pervaporation membranes [RU 2129910, 03/05/1997], which includes the preparation of an asymmetric microporous substrate with subsequent formation of a selective diffusion polymer layer on the skin of the substrate. In this case, an asymmetric microporous substrate is obtained by wet molding by applying a solution of polyamide in an aprotic polar solvent with a layer on a smooth surface of an inert material, followed by immersion in a precipitation bath. On the surface of the skin layer of the obtained substrate, a diffusion layer of poly-H-N, N, N, N-trimethylmethacryloyloxyethyl ammonium salt is formed by applying an aqueous polymer solution to the skin layer of the microporous substrate, followed by drying.

A significant drawback of this method is the need for an additional step, including the preparation of a microporous substrate, which increases the time and energy costs, and also creates additional environmental problems in connection with the use of harmful chemicals in the preparation of the substrate. The membrane obtained by this method cannot be used to isolate esters, since it is hydrophilic, like most known composite membranes.

The technical task and the technological result of the proposed method is to create a composite membrane with improved transport properties (selectivity and permeability) for the allocation of esters in a hybrid process for the production of alkyl acetates. The developed method for producing a composite membrane will make it possible to make a more technologically advanced procedure for producing membranes, eliminating the use of harmful chemicals for the preparation of the substrate, as well as to obtain membranes that are characterized by high permeability and good selectivity for the separation of esters during pervaporation. In addition, the use of a commercially available membrane from a copolymer of vinylidene fluoride with tetrafluoroethylene on a lavsan basis as a substrate will significantly reduce the cost of the composite membrane.

This is achieved by the development of a method for producing composite membranes with a fullerene-containing polymer selective layer for the separation of esters in a hybrid process for the production of alkyl acetates, including the formation of a selective diffusion polymer layer on a microporous substrate, and a microfiltration membrane from a vinylidene fluoride copolymer with lavsan tetrafluoroethylene is used as a microporous substrate 6-8 microns thick from a mixture of polyphenylene oxide and fullerene C _{60 is} formed by applying 2 wt.% - a solution of this mixture in chloroform on the surface of the microporous substrate, followed by drying.

The method is characterized in that a mixture of polyphenylene oxide and fullerene C _{60 is used} , containing 0.5-2 wt.% C ₆₀ obtained by mixing solutions of polyphenylene oxide in chloroform and fullerene C ₆₀ in toluene, followed by ultrasonic treatment.

The method is illustrated by examples of its implementation.

Example 1. A composite membrane with a surface layer of a thickness of 6-8 μm was obtained by watering a 2 wt.% Mixture of poly-2,6-dimethyl-1,4-phenylene oxide (98 wt.%) And fullerene (2 wt.%) In a solution of chloroform and toluene on a porous fluoroplastic substrate fixed in a metal form. The excess solution was poured, the membrane was dried at 40 ° C to constant weight. A mixture of poly-2,6-dimethyl-1,4-phenylene oxide and fullerene C _{60 was} obtained by mixing a 5% solution of poly-2,6-dimethyl-1,4-phenylene oxide in chloroform and a 0.1% solution of fullerene C ₆₀ in toluene, followed by ultrasonic treatment. The transport properties of the composite membrane, which consisted of a selective layer of a mixture of poly-2,6-dimethyl-1,4-phenylene oxide (98 wt.%) And fullerene (2 wt.%) On a fluoroplastic substrate, were characterized during pervaporation separation of the equilibrium mixture of the esterification reaction : 16.2 wt.% Ethanol 7.8 wt.% Water, 57.1 wt.% Ethyl acetate, 18.8 wt.% Acetic acid. The permeability of the membrane at a temperature of 20 ° C was 0.84 kg / m ² · h, the content of ethyl acetate in the initial mixture and permeate (product passing through the membrane) was 57.1 wt.% And 85.1 wt.%, Respectively (table ., Sample 2).

Example 2. The method of obtaining and characterizing the transport properties is similar to that described in example 1. As a selective layer, a mixture of poly-2,6-dimethyl-1,4-phenylene oxide (99.5 wt.%) And fullerene (0.5 wt.%) Was used. .

The membrane is characterized by a permeability of 0.62 kg / m ² · hour, the content of ethyl acetate in the permeate was 83 wt.%. (tab., sample 1).

Example 3. The method of obtaining and characterizing the transport properties is similar to that described in example 1. As a selective layer, a mixture of poly-2,6-dimethyl-1,4-phenylene oxide (97 wt.%) And fullerene (3 wt.%) Was used.

The membrane is characterized by a permeability of 0.90 kg / m ² · hour, the content of ethyl acetate in the permeate was 71.9 wt.%. (tab., sample 3).

Table Transport properties of composite membranes during the pervaporation of the equilibrium mixture of the esterification reaction: 16.2 wt.% Ethanol, 7.8 wt.% Water, 57.1 wt.% Ethyl acetate, 18.8 wt.% Acetic acid; 20 ° C The composition of the selective layer of the membrane Q, kg / m ² · hour The composition of permeate, wt.% water ethanol ethyl acetate acetic acid PFD (0.5% C ₆₀ ) 0.62 5.3 10,2 83.0 1,5 VFD (2% C ₆₀ ) 0.84 5.5 6.9 85.1 2.5 PFD (3% C ₆₀ ) 0.9 14.1 11.0 71.9 3.0

Going beyond the stated interval parameters (examples 1, 2) leads to a deterioration in the implementation of the claimed invention, which confirms the correctness of the selected operations, modes and parameters. A new method for producing a composite membrane allows one to make a more technologically advanced procedure for producing membranes, eliminating the use of harmful chemicals for the preparation of the substrate. The approach used allows one to obtain membranes that are characterized by high permeability and good selectivity for the ester release during pervaporation. In addition, the use of a commercially available membrane as a substrate, consisting of a copolymer of vinylidene fluoride with lavsan based tetrafluoroethylene, will significantly reduce the cost of the composite membrane.

Thus, the developed method for producing a composite membrane allows one to obtain a new type of membrane with a selective layer of fullerene-polyphenylene oxide nanocomposite on a fluoroplastic substrate, which has good transport (membrane) characteristics.

Claims (1)

A method of producing composite membranes with a fullerene-containing polymer selective layer for separating ethers in a hybrid process for producing alkyl acetates, comprising forming a selective diffusion polymer layer on a microporous substrate, characterized in that a microfiltration membrane from a vinylidene fluoride copolymer with lavsan-based tetrafluoroethylene is used as a microporous substrate 6-8 microns thick from a mixture of polyphenylene oxide and fullerene C _{60 is} formed by applying a 2% solution this mixture onto the surface of the microporous substrate, followed by drying, using a mixture of C ₆₀ polyphenylene oxide and C ₆₀ fullerene containing 0.5-2 wt% C ₆₀ obtained by mixing solutions of polyphenylene oxide in chloroform and C ₆₀ fullerene in toluene, followed by ultrasonic treatment.