CN103304672B - Method and device for preparing cellulose acetate in super (sub) critical CO2 - Google Patents
Method and device for preparing cellulose acetate in super (sub) critical CO2 Download PDFInfo
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Abstract
The invention relates to a preparation method of cellulose acetate, and particularly relates to a method and a device for preparing cellulose acetate in super (sub) critical CO2, and a device of the same. The method comprises the following steps of: generating primary cellulose acetate ester under the action of an acid catalyst by using super (sub) critical CO2 as a medium, and cotton linter and acetic anhydride as a raw material, performing super (sub) critical CO2 extraction, hydrolysis and aftertreatment on the primary cellulose acetate ester to get the cellulose acetate. In the method, high pressure CO2 is used as the medium for cellulose acetylation, the acetylation is accelerated, the acetylation in the method is solid-phase reaction, hydrolysis side reaction of the cellulose in acetylation process is limited effectively, so that the cellulose acetate product with high intrinsic viscosity can be prepared, and the production cost of cellulose acetate is lowered remarkably.
Description
Technical field
The present invention relates to the preparation method of cellulose acetate, be specifically related to a kind of super (Asia) critical CO
2middle method and the device thereof preparing cellulose acetate.
Background technology
Cellulose acetate is a kind of important cellulose organic ester, and can be widely used as the raw materials for production of cigarette filter, plastics, film, regenerated fiber, liquid crystal protective film and coating etc., be also one of kind that in derivatived cellulose, output is maximum.Usually cellulose acetate degree of substitution with acetyl group being greater than 2.8 is called cellulosetri-acetate (TCA), and substitution value is called Cellulose diacetate (DCA) between 2.0 ~ 2.7.
The industrial process mainly solvent method of cellulose acetate, be namely acetylizing agent with acetic anhydride, sulfuric acid is catalyzer, and in Glacial acetic acid or methylene dichloride equal solvent, direct esterification obtains cellulose acetate.The process manufacturing cellulose acetate generally includes:
(1) cellulosic material is carried out activating pretreatment, to improve acetylizad reactive behavior;
(2) Mierocrystalline cellulose after activation makes cellulosetri-acetate with acetic anhydride generation acetylization reaction in glacial acetic acid;
(3) again TCA is hydrolyzed, reduces its degree of acetylation, to obtain the DCA more having industrial value that can be dissolved in acetone;
(4) add water by DCA from reaction system precipitating out, then through final synthesizing and purifying DCA of operation such as bleaching, precipitating, boiling, dryings.
Such as, United States Patent (USP) 3767642 discloses one and carries out pre-treatment by dilute acetic acid aqueous solution to wooden oar, then acetic anhydride and the acetic acid synthesized Mierocrystalline cellulose of sulfuric acid catalysis is used, obtained cellulosetri-acetate saponification and slaking at 125-170 DEG C again, obtains the cellulose acetate with good transparency, filtrability and spinning property.
United States Patent (USP) 4306060 discloses a kind of acetic acid synthesized cellulosic method.The method at high temperature utilizes a small amount of sulfuric acid for catalyzer, realizes acetylize within the shorter reaction times, then neutralisation of sulphuric acid, and saponification and slaking at 110-120 DEG C, obtained cellulose acetate product.
It is the method that cellulose acetate prepared by raw material with the rudimentary wooden oar containing alpha-cellulose less (85-93%) that Chinese patent ZL93106682.4 discloses a kind of.The wooden oar of 100 weight parts is used the acetic acid of 400-17000 weight part and acylating agent pre-treatment 0.5-4 hour at 20-80 DEG C of 0.1-10 weight part by the method after crushed, with optionally depolymerization hemicellulose and grape mannosans; Then sulfuric acid is catalyzer, carries out 3-20 minute acidylate with the aceticanhydride of 150-800 weight part at 50-85 DEG C, and hydrolysis obtains acetyl cellulose.
Chinese patent ZL93108766.X provides a kind of method of combining activation acetylize and preparing cellulose acetate.The method be first by Mierocrystalline cellulose under amides swelling agent, fatty alcohol polyethenoxy ether class permeate agent and part glacialacetic acid and catalyst action; activation treatment more than 1 hour at 28-35 DEG C; then at 80-115 DEG C, carry out acetylize with aceticanhydride, and prepare acetyl cellulose through hydrolysis.The method can Appropriate application heat energy, has catalyst levels low, the feature that by product is few.
Chinese patent ZL99117070.9 discloses a kind of acetic ester method of gas-solid phase reaction synthetic cellulose.The method utilizes acetic anhydride steam can the inner feature of infiltrated fiber element, realize producing cellulose acetate at relatively high temperatures, can without Glacial acetic acid as reaction medium in reaction system, but reaction requires to carry out under vacuum conditions, is difficult to the acetyl cellulose preparing high-polymerization degree.
The remarkable shortcoming that solvent method in the past produces cellulose acetate existence is that production process has a large amount of light acetums to need recycling.The cellulose acetate of methylcellulose Acetylated rear formation and after being transformed by acetic anhydride the acetic acid of by-product and solvent form a uniform solution, for make cellulose acetate therefrom precipitating out, need the water of 3 ~ 4 times adding reaction mother liquor in reaction system.In addition, in cellulose acetate production process, in order to ensure that acetylization reaction carries out thoroughly, need to add excessive acetic anhydride.Like this, when adding water precipitating, not only causing excess acetic anhydride to recycle, also can form a large amount of dilute acetic acid solutions.Precipitating thick cellulose acetate product out, because needing to do boiling process further containing a large amount of free acetic acid, to remove free acid, causes so again a large amount of dilute acetic acid solutions.The boiling point of acetic acid is higher than water, no matter be adopt straight run distillation recovery of acetic acid, or adopts extractive distillation to reclaim, all can considerably increase steam output, significantly improve the production cost of cellulose acetate.
Summary of the invention
The object of this invention is to provide a kind of super (Asia) critical CO
2the middle method preparing cellulose acetate; the method employing high-pressure carbon dioxide is the medium of methylcellulose Acetylated reaction; accelerate the carrying out of acetylization reaction; acetylization reaction in the method is solid state reaction; effectively limit the hydrolytic side reactions of Mierocrystalline cellulose in acetylization reaction process; thus produce the cellulose acetate product with high inherent viscosity, significantly reduce the production cost of cellulose acetate, invention also provides the device that the method uses.
Super (Asia) critical CO of the present invention
2the middle method preparing cellulose acetate is with super (Asia) critical CO
2for medium, with linters and acetic anhydride for raw material, under an acidic catalyst effect, prepare cellulose acetate.
Specifically comprise the following steps:
(1) activating pretreatment: first pre-treatment is carried out to the activation solution of linters containing an acidic catalyst;
First the linters being not less than 90% containing alpha-cellulose carries out activation treatment.Activation method is very simple, only needs the acetum Direct Uniform of an acidic catalyst containing acetylize to be sprayed on the surface of linters, and keeps certain hour.An acidic catalyst is one or both the mixture in trifluoromethanesulfonic acid, sulfuric acid, and the mass ratio of an acidic catalyst, linters and acetic acid is 0.01-0.05:1:0.5-2.
(2) primary cellulose acetate is synthesized: pretreated linters is at super (Asia) critical CO
2with acetic anhydride generation acetylization reaction in medium, obtain primary cellulose acetate;
Be placed in by pretreated linters in autoclave and react with acetic anhydride, suitable temperature of reaction is 30-90 DEG C, and suitable working pressure is 5-30MPa, and the suitable reaction times is 0.5-5 hour.
(3) extract: (Asia) critical CO is surpassed to primary cellulose acetate
2extraction, reclaim unreacted acetic anhydride and acetic acid be extracted after primary cellulose acetate; Extraction temperature 40-80 DEG C, extracting pressure 10-30MPa.
Primary cellulose acetate directly utilizes dynamically super (Asia) critical CO
2extract by the unreacted aceticanhydride that remains in product and acetic acid extraction out, and the primary cellulose acetate after being extracted in still.
The acetic anhydride extracted and acetic acid are through decompression and CO
2be separated, reclaim and recycle.
(4) be hydrolyzed, neutralization: the primary cellulose acetate after extraction again through hydrolysis, in and an acidic catalyst obtain secondary cellulose acetate;
Described hydrolysis, neutralization: be by extraction after cellulose acetate be crushed to diameter particle and be less than 0.2mm, first at 40-90 DEG C, stir hydrolysis, then with in the mol ratio 1-2 being equivalent to an acidic catalyst sodium-acetate doubly and removing an acidic catalyst.
(5) boiling: secondary cellulose acetate through boiling removing catalyzer and free acetic acid, more after filtration, dry the cellulose acetate product that obtained substitution value is 2.0-2.95.
Described boiling: be scattered in aqueous systems by secondary cellulose acetate, stirs at being heated to 90-100 DEG C, until boiling terminates when the pH value of the aqueous solution is greater than 6.
The present invention realizes surpassing (Asia) critical CO
2the middle device preparing cellulose acetate method, comprises autoclave, autoclave and separator, compressor, CO
2basin, high pressure CO
2transferpump forms loop line, wherein between autoclave and separator, sets gradually stopping valve and back pressure regulating valve.
The structure of autoclave is as follows: autoclave outer setting heating jacket, heating jacket top sets out the mouth of a river, hot water inlet is offered in bottom, autoclave internal space is separated by silk screen dividing plate and is divided into linters rest area, top and acetic anhydride rest area, bottom, the bottom of acetic anhydride rest area, bottom arranges magnetic rotor, the magnet that autoclave outer setting adapts with it, magnet is connected with motor, and high pressure CO is offered in the side, bottom of acetic anhydride rest area, bottom
2entrance.
Compared with prior art, the present invention has following beneficial effect:
The present invention is directed to the technical problem existed in cellulose acetate preparation method in the past, propose super (Asia) critical CO innovatively
2the acetic acid synthesized cellulosic method of middle Mierocrystalline cellulose one-step acylation.The present invention adopts high-pressure carbon dioxide to be the reaction medium of methylcellulose Acetylated reaction; substitute the organic solvents such as the conventional acetic acid of previous methods or methylene dichloride; thus make acetylization reaction according to the difference of temperature of reaction and pressure carbon dioxide; can supercritical co when pressure is greater than 7.34MPa (temperature higher than 31.4 DEG C and) or subcritical carbon dioxide (comprise temperature lower than 31.4 DEG C and pressure is greater than 7.34MPa time liquid carbon dioxide, and temperature lower than 31.4 DEG C and pressure is greater than 7.34MPa time dense gaseous carbon dioxide) carry out under condition.Employing carbonic acid gas is one of advantage of reaction medium: carbonic acid gas is not only cheap and easy to get, wide material sources, and is green non-poisonous chemical.The more important thing is, the carbonic acid gas Dichlorodiphenyl Acetate Mierocrystalline cellulose under high pressure and Mierocrystalline cellulose have good Swelling Capacity, can accelerate the carrying out of acetylization reaction.Particularly importantly, super (Asia) critical CO
2acetylization reaction under condition is a kind of solid state reaction, effectively can limit the hydrolytic side reactions of Mierocrystalline cellulose in acetylization reaction process like this, thus can produce the cellulose acetate product with high inherent viscosity.
At cellulosic acetylation, the DeR of invariably accompany acetylization reaction and cellulose chain, thus the cellulosic polymerization degree of Dichlorodiphenyl Acetate can make a significant impact, shows as the cellulose acetate product being difficult to produce high inherent viscosity.In order to accelerate the speed of acetylization reaction and make acetyl react to carry out thoroughly, avoid cellulosic excessive degradation, usually can adopt excessive acetic anhydride, namely in acetic anhydride and Mierocrystalline cellulose, the mol ratio of glucose unit is greater than the 3:1 of theoretical value.But the consequence brought like this is: the precipitating that after reaction, cellulose acetate added water from reaction mother liquor out time, excessive acetic anhydride can react with water and be converted into acetic acid, cannot reclaim, add production cost.In addition, when taking acetic anhydride as acetylizing agent, the acetic acid of 1mol aceticanhydride meeting by-product 1mol is often consumed.Dilture acid is produced always unavoidable during the precipitating that adds water.Because the boiling point of acetic acid is higher than water, thus the cost of Distillation recovery acetic acid is very high.
Another outstanding advantages of method preparing cellulose acetate provided by the invention is: after acetylization reaction, and excessive or unreacted acetic anhydride and association acetic acid, can utilize supercritical CO
2to its excellent dissolution power, by the method for extraction, it is separated with cellulose acetate, thus is easy to recovery and reuse, reduce the consumption of acetic anhydride, avoid the generation of a large amount of dilture acid in conventional art, significantly reduce cost recovery.The apparatus structure that the present invention uses is simple, processing ease.
Accompanying drawing explanation
Fig. 1 is autoclave structural representation of the present invention;
Fig. 2 is the structural representation of apparatus of the present invention;
Fig. 3 is present invention process schematic flow sheet;
In figure: 1, CO
2outlet; 2, autoclave; 3, heating jacket; 4, silk screen dividing plate; 5, hot water inlet; 6, magnetic rotor; 7, magnet; 8, motor; 9, high pressure CO
2entrance; 10, bottom acetic anhydride rest area; 11, top linters rest area; 12, water outlet; 13, stopping valve; 14, back pressure regulating valve; 15, the valve between separator and compressor; 16, separator; 17, separator bottom valve; 18, high pressure CO
2valve between transferpump and reactor; 19, high pressure CO
2transferpump; 20, high pressure CO
2transferpump and CO
2valve between basin; 21, CO
2basin; 22, compressor.
Embodiment
Below in conjunction with embodiment, the present invention is described further.
The present invention prepares the device of cellulose acetate use as Figure 1-3:
Fig. 1 is autoclave 2 structural representation that the present invention uses, and the acetylization reaction of cellulose acetate carries out in the high pressure stainless steel cauldron shown in accompanying drawing 1.The centre of this autoclave 2 arranges a silk screen dividing plate 4, is divided into by autoclave 2, two portions.Upper part is for placing cellulosic material linters, and lower part, for placing acetic anhydride, can effectively avoid acetic anhydride directly to contact with cellulosic like this.Meanwhile, magnetic rotor 6 can be placed in lower part, to strengthen the mass transfer of still and acetic anhydride to the dissolving in carbonic acid gas and diffusion.The shell of autoclave 2 is provided with heating jacket 3, to control the temperature of autoclave 2 by water bath with thermostatic control system.Certainly, acetylization reaction also can carry out without under agitation condition, just can because there is resistance to mass transfer, and cause acetylization reaction speed to decrease, thus extend the reaction times.
Fig. 2 is the apparatus structure schematic diagram carrying out acetylization reaction and extraction under super (Asia) critical condition.Wherein, autoclave 2 and separator 16, compressor 22, CO
2basin 21, high pressure CO
2transferpump 19 forms loop line, wherein between autoclave 2 and separator 16, sets gradually stopping valve 13 and back pressure regulating valve 14.
High pressure CO
2transferpump 19 is for continus convergence carbonic acid gas in autoclave 2; Back pressure regulating valve 14 is for the pressure of Controlling System; When separator 16 is for supercritical extraction, carry out CO
2with the gas-liquid separation of the solute extracted (acetic anhydride and acetic acid); Compressor 22 is for the CO by decompression
2again CO is sent in pressurization back to
2basin 21, to recycle.Carry out acetylization reaction, first cellulosic material linters is positioned on the silk screen dividing plate 4 of autoclave 2, on linters, then evenly spray the acetum containing an acidic catalyst, and activate certain hour.Certainly, reactivation process also can complete outside still.After activation, by autoclave 2 good seal, first fall by the air displacement of carbonic acid gas by autoclave 2, then heat up and pass into CO
2to autoclave 2, reach the temperature and pressure of setting, start stirring, keep temperature and pressure to carry out acetylization reaction.After completion of the reaction, CO is opened
2outlet shutoff valve 13 and CO
2inlet valve 18, starts high pressure CO
2transferpump 19, makes CO
2continuous Flow is through Mierocrystalline cellulose rest area.Regulate back pressure valve 14, make pressure-stabilisation to set(ting)value, carry out dynamic continuous extraction, make unreacted acetic anhydride and acetate dissolution in CO
2middle extraction.From the CO that autoclave 2 flows out
2separator 16 is entered, now CO after decompression
2the dissolving power of Dichlorodiphenyl Acetate acid anhydride and acetic acid declines, and releases out, in separator, complete CO
2the gas-liquid separation of gas and solute.The bottom of separator 16 stayed by acetic anhydride and acetic acid, and CO
2then flow out separator 16, and flow back to CO after compressed supercharging
2basin 21.
The hydrolysis object of cellulose acetate produces the cellulose acetate product with suitable degree of substitution with acetyl group, the neutralization of catalyzer, the boiling of cellulose acetate product be all the professional of cellulose acetate preparation process know knowledge.
Accompanying drawing 3 is whole process flow diagrams preparing cellulose acetate provided by the present invention.
Embodiment 1
The activation of linters: the glacial acetic acid solution containing the trifluoromethanesulfonic acid of 2% at 8.2g refined cotton linter (amount of about amounting to glucose unit meter in alpha-cellulose is 50mmol, lower same) the even 10mL of sprinkling, and at room temperature activate 2 hours.
The preparation of cellulose acetate: the bottom of the reactor shown in accompanying drawing 1 adds 25.5g acetic anhydride (about 250mmol); Linters after above-mentioned activation is placed in above silk screen dividing plate, after good seal reactor, uses CO
2cyclostrophic changes the air in still, then heats up and passes into CO
2to 50 DEG C and 20MPa, start magnetic agitation, stirring velocity 600 turns/min, insulation reaction 3 hours.React complete, open the CO on reactor
2outlet valve, sends constantly into CO by high-pressure pump simultaneously
2, under 40 DEG C and 20MPa, carry out extracting operation.The CO discharged
2enter separator through reducing valve, collect aceticanhydride and the acetic acid of extraction, the carbonic acid gas flowed out from separator can be recycled after compressor pressurization again; Be extracted to and no longer include aceticanhydride and acetic acid and extracted when, stop extracting operation; Then reactor is decompressed to normal pressure, take out the primary cellulose acetate product in still, be crushed to particle diameter and be less than 0.2mm, and be scattered in 50ml water at 40 DEG C, stir hydrolysis 1 hour, then add 0.3g sodium-acetate and neutralize catalyzer, again at 90-100 DEG C of boiling more than five times (each 50ml deionized water), to be fully hydrolyzed the free acetic acid removing a small amount of cellulose iii fluorofomates and residue in surface of cellulose acetate on a small quantity, refilter and dry obtained cellulose acetate product.Record degree of substitution with acetyl group 2.65 in product by analysis; Take acetone as solvent, through the limiting viscosity 1.8 of capillary viscosity at 25 DEG C.
Embodiment 2
The activation of linters: 8.2g Mierocrystalline cellulose evenly spray 10mL containing 4% the glacial acetic acid solution of sulfuric acid, and 40 DEG C of activation 2 hours.
The preparation of cellulose acetate: the bottom of reactor adds 30.6g acetic anhydride (about 300mmol), is placed in by the linters of activation above silk screen dividing plate, after good seal reactor, uses CO
2cyclostrophic changes the air in still, passes through CO
2to certain pressure, and be warmed up to 40 DEG C, after temperature-stable, continue to pass into CO
2to 30MPa, start magnetic agitation, stirring velocity 600 turns/min, insulation reaction 5 hours.React complete, open CO
2outlet valve, and constantly supplement fresh CO simultaneously
2, extract at 60 DEG C and 30MPa.The CO discharged
2enter separator through reducing valve, collect aceticanhydride and the acetic acid of extraction, extracted when until no longer include aceticanhydride and acetic acid, stop extracting operation; Then normal pressure is decompressed to, take out the cellulose acetate product in still, be crushed to particle diameter and be less than 0.3mm, and be scattered in 50ml water at 60 DEG C, stir hydrolysis 2 hours, then add 0.5g sodium-acetate and neutralize catalyzer, again at 90-100 DEG C of boiling more than five times (each 50ml deionized water), to be fully hydrolyzed remove portion cellulose sulfuric acid ester and to residue in the free acetic acid of surface of cellulose acetate on a small quantity, refilter and dry obtained cellulose acetate product.Record degree of substitution with acetyl group 2.76 in product by analysis; Take acetone as solvent, through the limiting viscosity 1.3 of capillary viscosity at 25 DEG C.
Embodiment 3
The activation of linters: evenly spray 10mL containing the acetum of trifluoromethanesulfonic acid of 0.8% at 8.2g Mierocrystalline cellulose, and activate 3 hours at 60 DEG C.
The preparation of cellulose acetate: add 40.8g acetic anhydride (about 400mmol) in the bottom of reactor, is then placed in above silk screen dividing plate by the linters of activation, after good seal reactor, uses CO
2cyclostrophic changes the air in still, passes through CO
2to certain pressure, and be warmed up to 90 DEG C, after temperature-stable, continue to pass into CO
2to 30MPa, start magnetic agitation, stirring velocity 600 turns/min, insulation reaction 4 hours.React complete, open CO
2outlet valve, and constantly supplement fresh CO simultaneously
2, extract at 50 DEG C and 30MPa, until no longer include aceticanhydride and acetic acid is extracted.Then normal pressure is decompressed to, take out the cellulose acetate product in still, be crushed to particle diameter and be less than 0.2mm, and be scattered in 50ml water at 80 DEG C, stir hydrolysis 1 hour, then add 0.5g sodium-acetate and neutralize catalyzer, again at 90-100 DEG C of boiling more than five times (each 50ml deionized water), to be fully hydrolyzed the free acetic acid removing a small amount of cellulosic triflate and residue in surface of cellulose acetate on a small quantity, refilter and dry obtained cellulose acetate product.Obtain cellulose acetate product after drying, record degree of substitution with acetyl group 2.33 in product by analysis; Take acetone as solvent, through the limiting viscosity 1.1 of capillary viscosity at 25 DEG C.
Embodiment 4
The activation of linters: evenly spray the acetum of 5mL containing 3% sulfuric acid at 8.2g Mierocrystalline cellulose, and activate 0.5 hour at 20 DEG C.
The preparation of cellulose acetate: add 30.6g acetic anhydride (about 300mmol) in the bottom of reactor, is then placed in above silk screen dividing plate by the linters of activation, after good seal reactor, uses CO
2cyclostrophic changes the air in still, passes through CO
2to certain pressure, and be warmed up to 30 DEG C, after temperature-stable, continue to pass into CO
2to 5MPa, start magnetic agitation, stirring velocity 600 turns/min, insulation reaction 4 hours.React complete, open CO
2outlet valve, and constantly supplement fresh CO simultaneously
2, extract at 40 DEG C and 10MPa.The CO discharged
2enter separator through reducing valve, collect aceticanhydride and the acetic acid of extraction, extracted when until no longer include aceticanhydride and acetic acid, stop extracting operation; Then normal pressure is decompressed to, take out the cellulose acetate product in still, be crushed to particle diameter and be less than 0.2mm, and be scattered in 50ml water at 90 DEG C, stir hydrolysis 3 hours, then add 0.4g sodium-acetate and neutralize catalyzer, again at 90-100 DEG C of boiling more than five times (each 50ml deionized water), to be fully hydrolyzed the free acetic acid removing a small amount of cellulosic sulfuric ester and residue in surface of cellulose acetate on a small quantity, refilter and dry obtained cellulose acetate product.Cellulose acetate product obtained after drying, records degree of substitution with acetyl group 2.62 in product by analysis; Take acetone as solvent, through the limiting viscosity 1.5 of capillary viscosity at 25 DEG C.
Embodiment 5
The activation of linters: evenly spray at 8.2g Mierocrystalline cellulose the glacial acetic acid solution that 5mL sulfur acid and trifluoromethanesulfonic acid are respectively 2%, and at room temperature activate 1 hour.
The preparation of cellulose acetate: add 30.6g acetic anhydride (about 300mmol) in the bottom of reactor, is then placed in above silk screen dividing plate by the linters of activation, after good seal reactor, uses CO
2cyclostrophic changes the air in still, passes through CO
2to certain pressure, and be warmed up to 90 DEG C, after temperature-stable, continue to pass into CO
2to 25MPa, start magnetic agitation, stirring velocity 600 turns/min, insulation reaction 3 hours.React complete, open CO
2outlet valve, and constantly supplement fresh CO simultaneously
2, extract at 80 DEG C and 20MPa.The CO discharged
2enter separator through reducing valve, collect aceticanhydride and the acetic acid of extraction, extracted when until no longer include aceticanhydride and acetic acid, stop extracting operation; Then normal pressure is decompressed to, cellulose acetate product in still will be taken out, then normal pressure is decompressed to, take out the cellulose acetate product in still, be crushed to particle diameter and be less than 0.2mm, and be scattered in 50ml water at 70 DEG C, stir hydrolysis 1 hour, then add 0.5g sodium-acetate and neutralize catalyzer, again at 90-100 DEG C of boiling more than five times (each 50ml deionized water), to be fully hydrolyzed remove portion triflate and to residue in the free acetic acid of surface of cellulose acetate on a small quantity, refilter and dry obtained cellulose acetate product.Dry obtained cellulose acetate product, record degree of substitution with acetyl group 2.82 in product by analysis; Take acetone as solvent, through the limiting viscosity 1.2 of capillary viscosity at 25 DEG C.
Claims (9)
1. super (Asia) critical CO
2the middle method preparing cellulose acetate, is characterized in that: be with super (Asia) critical CO
2for medium, with linters and acetic anhydride for raw material, under an acidic catalyst effect, prepare cellulose acetate;
First carry out activating pretreatment to the activation solution of linters containing an acidic catalyst before reaction, the activation solution containing an acidic catalyst is the acetic acid containing an acidic catalyst, and the mass ratio of an acidic catalyst, linters and acetic acid is 0.01-0.05:1:0.5-2.
2. super (Asia) critical CO according to claim 1
2the middle method preparing cellulose acetate, is characterized in that: described an acidic catalyst is trifluoromethanesulfonic acid and/or sulfuric acid.
3. super (Asia) critical CO according to claim 1
2the middle method preparing cellulose acetate, is characterized in that: the linters after activating pretreatment is at super (Asia) critical CO
2with acetic anhydride generation acetylization reaction in medium, obtain primary cellulose acetate; Acetylization reaction temperature is 30-90 DEG C, and reaction pressure is 5-30MPa, and the reaction times is 0.5-5 hour.
4. super (Asia) critical CO according to claim 3
2the middle method preparing cellulose acetate, is characterized in that: surpass (Asia) critical CO to primary cellulose acetate
2extraction, reclaim unreacted acetic anhydride and acetic acid be extracted after primary cellulose acetate; Extraction temperature 40-80 DEG C, extracting pressure 10-30 MPa.
5. super (Asia) critical CO according to claim 4
2the middle method preparing cellulose acetate, is characterized in that: the acetic anhydride extracted and acetic acid are through decompression and CO
2be separated, reclaim and recycle.
6. super (Asia) critical CO according to claim 4
2the middle method preparing cellulose acetate, is characterized in that: the primary cellulose acetate after extraction again through hydrolysis, in and an acidic catalyst obtain secondary cellulose acetate.
7. super (Asia) critical CO according to claim 6
2the middle method preparing cellulose acetate, is characterized in that: secondary cellulose acetate through boiling removing catalyzer and free acetic acid, more after filtration, dry the cellulose acetate product that obtained substitution value is 2.0-2.95.
8. super (Asia) critical CO according to claim 1
2the middle method preparing cellulose acetate, is characterized in that: realize super (Asia) critical CO
2the middle device preparing cellulose acetate method comprises autoclave (2), autoclave (2) and separator (16), compressor (22), CO
2basin (21), high pressure CO
2transferpump (19) forms loop line, wherein between autoclave (2) and separator (16), sets gradually stopping valve (13) and back pressure regulating valve (14).
9. super (Asia) critical CO according to claim 8
2the middle method preparing cellulose acetate, it is characterized in that: autoclave (2) outer setting heating jacket (3), heating jacket (3) top sets out the mouth of a river (12), hot water inlet (5) is offered in bottom, autoclave (2) internal space is separated by silk screen dividing plate (4) and is divided into linters rest area, top (11) and acetic anhydride rest area, bottom (10), the bottom of acetic anhydride rest area, bottom (10) arranges magnetic rotor (6), the magnet (7) that autoclave (2) outer setting adapts with it, magnet (7) is connected with motor (8), high pressure CO is offered in the side, bottom of acetic anhydride rest area, bottom (10)
2entrance (9).
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| CN105686075B (en) * | 2016-03-08 | 2019-08-09 | 云南中烟工业有限责任公司 | A kind of preparation method of cellulose acetate aperture microcellular foam material filter tip adsorbing bar |
| CN111574635B (en) * | 2019-02-18 | 2022-05-20 | 四川普什醋酸纤维素有限责任公司 | Stabilization treatment system for cellulose acetate and derivatives thereof |
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