The present invention relates to a method for the preparation of a type of hydrophobic composite membranes comprising a) a hydrophobic perfluorinated or highly fluorinated polymer b) a microporous filler; to said membranes; to the use of said membranes in separation methods. In particular this invention relates to a method for preparing composite membranes comprising a hydrophobic perfluorinated or highly fluorinated polymer, and microporous fillers characterized by the presence of hydroxyl groups on their outer surface before modification comprising the steps of: preliminary modification of non fluorophilic microporous fillers with a fluorophilic surface modifying agent; mixing the porous filler with a solution of the polymer; forming a homogeneous distribution of the porous filler in the solution of the polymer; casting of the membrane; removing solvent from the composite membrane. Mixed matrix membranes in which the continuous phase is comprised of a hydrophobic perfluorinated or highly fluorinated polymer, and the dispersed phase is comprised of microporous particles which, in origin, contain on their outer surface –OH groups, are obtained through a preliminary surface modification treatment of the porous particles with the stoichiometric amount or a modest excess of a fluorophilic surface modifying agent. The fluorophilic surface modifying agent is a bi- or trifunctional organic compounds of silicon, such that: (a) at least one substituent of silicon must be compatible with the polymer; (b) two or three displaceable radicals of silicon are able to react with the external surface of the porous particles thus enabling silicon to graft on it with two or three bonds, in order to impart hydrolytical stability to the graft. The process for the preparation of such mixed membranes involves the preliminary treatment of non fluorophilic porous particles with a bi- or tri-functional fluorophilic surface modification agent, the uniform dispersion of the fluorophilic porous particles in a solution of the fluoropolymer, and the formation of the structure of the mixed matrix membranes. The membranes of the present invention can be prepared with porous filler of high aspect ratio, in which such porous particles are oriented with their largest dimensions parallel to the external surface of the membrane. The membranes of the present invention can be porous or dense, and can be applied in the separation of gas and liquid mixtures, in the separation of solutes from a solution, or as catalytic membranes. The dense mixed matrix membranes for the separation of gas prepared according to the methods of the present invention yield a better combination of permeability and selectivity with respect to membranes made of sole polymer. The membranes of the present invention which contain high aspect ratio porous fillers oriented with their largest dimensions parallel to the external surface of the membrane enable to obtain better permeability and selectivity combinations with respect to analogous membranes containing low aspect ratio filler. Dense mixed matrix membranes formed by a perfluoropolymer continuous phase and a fluorophilic porous filler dispersed phase, prepared according to the methods disclosed by the present invention, display improved permeability and selectivity combinations for the separation of CO2 from mixtures containing methane.
Method for preparing hydrophobic fluorinated mixed matrix membranes, said membranes, and separation methods using said membranes
GOLEMME, Giovanni;
2012-01-01
Abstract
The present invention relates to a method for the preparation of a type of hydrophobic composite membranes comprising a) a hydrophobic perfluorinated or highly fluorinated polymer b) a microporous filler; to said membranes; to the use of said membranes in separation methods. In particular this invention relates to a method for preparing composite membranes comprising a hydrophobic perfluorinated or highly fluorinated polymer, and microporous fillers characterized by the presence of hydroxyl groups on their outer surface before modification comprising the steps of: preliminary modification of non fluorophilic microporous fillers with a fluorophilic surface modifying agent; mixing the porous filler with a solution of the polymer; forming a homogeneous distribution of the porous filler in the solution of the polymer; casting of the membrane; removing solvent from the composite membrane. Mixed matrix membranes in which the continuous phase is comprised of a hydrophobic perfluorinated or highly fluorinated polymer, and the dispersed phase is comprised of microporous particles which, in origin, contain on their outer surface –OH groups, are obtained through a preliminary surface modification treatment of the porous particles with the stoichiometric amount or a modest excess of a fluorophilic surface modifying agent. The fluorophilic surface modifying agent is a bi- or trifunctional organic compounds of silicon, such that: (a) at least one substituent of silicon must be compatible with the polymer; (b) two or three displaceable radicals of silicon are able to react with the external surface of the porous particles thus enabling silicon to graft on it with two or three bonds, in order to impart hydrolytical stability to the graft. The process for the preparation of such mixed membranes involves the preliminary treatment of non fluorophilic porous particles with a bi- or tri-functional fluorophilic surface modification agent, the uniform dispersion of the fluorophilic porous particles in a solution of the fluoropolymer, and the formation of the structure of the mixed matrix membranes. The membranes of the present invention can be prepared with porous filler of high aspect ratio, in which such porous particles are oriented with their largest dimensions parallel to the external surface of the membrane. The membranes of the present invention can be porous or dense, and can be applied in the separation of gas and liquid mixtures, in the separation of solutes from a solution, or as catalytic membranes. The dense mixed matrix membranes for the separation of gas prepared according to the methods of the present invention yield a better combination of permeability and selectivity with respect to membranes made of sole polymer. The membranes of the present invention which contain high aspect ratio porous fillers oriented with their largest dimensions parallel to the external surface of the membrane enable to obtain better permeability and selectivity combinations with respect to analogous membranes containing low aspect ratio filler. Dense mixed matrix membranes formed by a perfluoropolymer continuous phase and a fluorophilic porous filler dispersed phase, prepared according to the methods disclosed by the present invention, display improved permeability and selectivity combinations for the separation of CO2 from mixtures containing methane.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
