Method for preparing thin regenerated cellulose membranes of high flux and selectivity for organic liquids separations

Claim 3

The method of claim 1 wherein the cellulose material of step A has a molecular degree of polymerization (DP) of 1,000 or more.

Claim 4

The method of claim 2 wherein the cellulose material is dissolved in cuene, the cellulose concentration in the solution being about 2% or greater.

Claim 5

The method of claim 1, 2 or 3 wherein the alcoholic alkali solution of step C contains about 5% to about 20% alkali.

Claim 6

The method of claim 4 wherein the alkali in the alcoholic alkali solution is KOH, or NaOH.

Claim 7

The method of claim 5 wherein the alcohol of the alcoholic alkali solution is a C 1 -C 3 alcohol and mixtures thereof.

Claim 8

The method of claim 6 wherein the alcoholic alkali solution contains up to 25% water.

Claim 9

The method of claim 1, 2 or 3 wherein the alcohol used in the washing step D is a C 1 -C 3 alcohol and mixtures thereof.

Claim 10

The method of claim 8 wherein the alcohol contains up to 10% water.

Claim 11

The method of claim 7 wherein the alcohol used in the washing step D is a C 1 -C 3 alcohol and mixtures thereof containing up to 10% water.

Claim 12

The method of claim 1, 2 or 3 wherein the alcoholic acid solution used in regenerating step E is made up of mineral acids in C 1 -C 3 alcohols and mixtures thereof.

Claim 13

The method of claim 11 wherein the acid concentration in the alcoholic acid solution ranges from between about 5% to 10% by weight.

Claim 14

The method of claim 12 wherein the alcoholic acid solution contains up to 25% water.

Claim 15

The method of claim 10 wherein the alcoholic acid solution used in regenerating step E uses a mineral acid at a concentration of 5%-10% by weight in a C 1 -C 3 alcohol and mixtures thereof which alcohol contains up to 25% water.

Claim 16

The method of claim 1, 2 or 3 wherein the alcohol used in the alcohol washing step D is a C 1 -C 3 alcohol and mixtures thereof.

Claim 17

The method of claim 15 wherein the alcohol used in the alcohol washing step F contains up to 10% water.

Claim 18

The method of claim 14 wherein the alcohol used in the alcohol washing step F is a C 1 -C 3 alcohol and mixtures thereof containing up to 10% water.

Claim 19

The method of claim 1 further comprising drying step G conducted at a temperature of up to 60° C. in a non-degenerative atmosphere.

Claim 20

The method of claim 1 wherein the regenerated cellulose membrane is from <5 to about 200 μm thick.

Claim 21

The method of claim 1 or 19 wherein the regenerated cellulose membrane is in the form of sheets, tubes or fibers.

Claim 24

The method of claim 21 further comprising the step of: F. drying the regenerated cellulose at a temperature of 60° C. in a non-degenerative atmosphere.

Claim 25

The method of claim 21 or 22 wherein the regenerated cellulose membrane is from <5 to about 200 μm thick.

Claim 26

The method of claim 23 wherein the regenerated cellulose membrane is in the form of sheet, tubes or fibers.

Claim 27

A regenerated cellulose membrane prepared by the method of: A. dissolving a cellulose material to form a solution; B. casting the solution into the form of a film; C. coagulating the cellulose solution film using an alcoholic alkali solution; D. washing the coagulated cellulose film in an alcohol; E. regenerating the washed, coagulated cellulose film using an alcoholic acid solution; F. washing the regenerated cellulose film in an alcohol.

Claim 28

A regenerated cellulose membrane prepared by the method of: A. dissolving a cellulose material to form a solution; B. casting the solution into the form of a film; C. coagulating the cellulose solution film using an alcoholic alkali solution; D. washing the coagulated cellulose film in an alcohol; E. regenerating the washed, coagulated cellulose film using an alcoholic acid solution; F. washing the regenerated cellulose film in an alcohol.

Claim 29

The regenerated cellulose membrane of claim 25 wherein: A. the cellulose material of step A has a molecular degree of polymerization of 1,000 or more and is dissolved in cuene to yield a cellulose solution having a cellulose concentration of about 2% or greater; B. the coagulation step C practiced on the cellulose film of step B employs an alcoholic alkali solution wherein the alkali is KOH or NaOH in a C 1 -C 3 alcohol or mixture thereof at a concentration of 5%-20%, the alcohol containing up to 25% water; C. the washing step D employs a C 1 -C 3 alcohol or mixture thereof containing up to 10% water; D. the regeneration step employing an alcoholic acid solution using mineral or organic acid present at a concentration of 5%-10% by weight in a C 1 -C 3 alcohol or mixture thereof which contains up to 25% water; E. the washing of the regenerated cellulose membrane employs a C 1 -C 3 alcohol or mixture thereof containing up to 10% water.

Claim 30

The regenerated cellulose membrane of claim 25 further prepared by the step comprising: G. drying the membrane at a temperature of up to 60° C. in a non-degenerative atmosphere.

Claim 31

In a process for the dewaxing of waxy hydrocarbon oils comprising: (a) solvent dewaxing the waxy hydrocarbon oil by combining the waxy oil with a dewaxing solvent selected from C 3 -C 6 ketones and mixtures thereof, and mixtures of C 3 -C 6 ketones and C 6 -C 10 aromatic hydrocarbons for a mixture and chilling said waxy oil-solvent mixture to form a slurry comprising solid particles of wax and a mixture of dewaxed oil and dewaxing solvent; (b) passing said slurry to solid-liquid separation means to separate the solid particles of wax from the dewaxed oil/solvent mixture; and (c) contacting at least a portion of said dewaxed oil/solvent mixture, under pressure, with one side of at least one semipermeable membrane made from regenerated cellulose to form a permeate richer in said solvent than said mixture and a retentate leaner in said solvent than said mixture, wherein said membrane is prepared from a hydrophilic regenerated cellulose membrane by sequentially permeating through the membrane, under a differential pressure across the membrane, a series of solvents of decreasing polarity wherein adjacent solvents in the series exhibit bulk liquid-liquid miscibility with each other and wherein the last solvent exhibits bulk liquid-liquid miscibility with the dewaxing solvent to be permeated through the membrane, the improvement comprising using as the membrane a regenerated cellulose membrane prepared by the method of: (i) dissolving a cellulose material to form a solution; (ii) casting the cellulose material into a film; (iii) coagulating the cellulose solution film using an alcoholic alkali solution; (iv) washing the coagulated cellulose film in an alcohol; (v) regenerating the washed, coagulated cellulose film using an alcoholic acid solution; (vi) washing the regenerated cellulose film in an alcohol.

Claim 32

In a process for the dewaxing of waxy hydrocarbon oils comprising: (a) solvent dewaxing the waxy hydrocarbon oil by combining the waxy oil with a dewaxing solvent selected from C 3 -C 6 ketones and mixtures thereof, and mixtures of C 3 -C 6 ketones and C 6 -C 10 aromatic hydrocarbons for a mixture and chilling said waxy oil-solvent mixture to form a slurry comprising solid particles of wax and a mixture of dewaxed oil and dewaxing solvent; (b) passing said slurry to solid-liquid separation means to separate the solid particles of wax from the dewaxed oil/solvent mixture; and (c) contacting at least a portion of said dewaxed oil/solvent mixture, under pressure, with one side of at least one semipermeable membrane made from regenerated cellulose to form a permeate richer in said solvent than said mixture and a retentate leaner in said solvent than said mixture, wherein said membrane is prepared from a hydrophilic regenerated cellulose membrane by sequentially permeating through the membrane, under a differential pressure across the membrane, a series of solvents of decreasing polarity wherein adjacent solvents in the series exhibit bulk liquid-liquid miscibility with each other and wherein the last solvent exhibits bulk liquid-liquid miscibility with the dewaxing solvent to be permeated through the membrane, the improvement comprising using as the membrane a regenerated cellulose membrane prepared by the method of: (i) dissolving a cellulose material to form a solution; (ii) casting the cellulose material into a film; (iii) coagulating the cellulose solution film using an alcoholic alkali solution; (iv) washing the coagulated cellulose film in an alcohol; (v) regenerating the washed, coagulated cellulose film using an alcoholic acid solution; (vi) washing the regenerated cellulose film in an alcohol.

Claim 33

The process of claim 28 wherein the regenerated cellulose membrane synthesis procedure is marked by the following characteristics: (a) the cellulose material of step (i) has a molecular degree of polymerization of 1,000 or more and is dissolved in cuene to yield a cellulose solution having a cellulose concentration of about 2% or greater; (b) the coagulation step of step (iii) practiced on the cellulose film of step (ii) employs an alcoholic alkali solution wherein the alkali is KOH or NaOH in a C 1 -C 3 alcohol or mixture thereof at a concentration of 5%-20%, the alcohol containing up to 25% water; (c) the washing step (iv) employs a C 1 -C 3 alcohol or mixture thereof containing up to 10% water; (d) the regeneration step employs an alcoholic acid solution using mineral or organic acid present at a concentration of 5%-10% by weight in a C 1 -C 3 alcohol or mixture thereof which contains up to 25% water; (e) the washing of the regenerated cellulose membrane employs a C 1 -C 3 alcohol or mixture thereof containing up to 10% water.

Claim 34

The process of claim 28 wherein the regenerated cellulose membrane synthesis procedure is further marked by the preparative step comprising: (vii) drying the membrane at a temperature of up to 60° C. in a non-degenerative atmosphere in the absence of softeners.