CA1250283A - Method and apparatus involving supercritical fluid extraction - Google Patents
Method and apparatus involving supercritical fluid extractionInfo
- Publication number
- CA1250283A CA1250283A CA000540087A CA540087A CA1250283A CA 1250283 A CA1250283 A CA 1250283A CA 000540087 A CA000540087 A CA 000540087A CA 540087 A CA540087 A CA 540087A CA 1250283 A CA1250283 A CA 1250283A
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- Prior art keywords
- lignin
- supercritical fluid
- fluidized bed
- pressure
- super
- Prior art date
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
APPARATUS AND METHOD INVOLVING
SUPERCRITICAL FLUID EXTRACTION
ABSTRACT OF THE DISCLOSURE
An autoclave extraction apparatus using supercritical fluid is used for supercritical fluid extraction of one or several compounds. The supercritical fluid containing the compound(s) may then be processed in a pressurized bed reactor under supercritical conditions.
The bed being a fluidisable catalytic bed to carry out a catalytic reaction of the compound(s).
The method is particularly applicable to recover valuable lignin and other extractable components from kraft black liquor.
SUPERCRITICAL FLUID EXTRACTION
ABSTRACT OF THE DISCLOSURE
An autoclave extraction apparatus using supercritical fluid is used for supercritical fluid extraction of one or several compounds. The supercritical fluid containing the compound(s) may then be processed in a pressurized bed reactor under supercritical conditions.
The bed being a fluidisable catalytic bed to carry out a catalytic reaction of the compound(s).
The method is particularly applicable to recover valuable lignin and other extractable components from kraft black liquor.
Description
; ~25~Z83 I' I [;:LD 0~` Tl{E INVENTIO'`l This invention is directed to a method to recover valuable lignin and other extractable components Erom kraft black liquor using supercritical 1uids and to covert said recovered lignin into chemical products and to apparatuses to carry out reactions of supercritical fluids. By supercritical fluids is meant a gas or a liquid at a temperature above its critical temperature and a pressure above its critical pressure.
PRIOR ART
An extens-ive literature search conducted by the inventor has revealed that no one has published any in~ormation which may have bearing on ap~licant's invention:
The search has revealed that no one has thought of extracting lignin and other components from black liquor using supercritical gases, nor of reacting lignin dissolved in supercritical gaseous product in a fluidized bed catalytic reactor.
The following is a brief review of the current black liquor recovery process in which the polymeric lignin is combusted to CO2 for its fuel value: It is recognized that the Kraft process for pulp production wili be used by the industry for many years to come. The pulping chemicals NaOF~ and ~a2S extract lignin ,rom the wood to produce a pulp and a weak black liquor. The weak ; black liquor contains water, organic lignin derivatives, hydroxy acids and inorganic compounds derived ~rom the sodium. ~n essential criterion for the economic viahility ~æ
læs~3 ~of the ~Craft p~ocess is the recovery o~ inor(3anic cnemicals Eor récycle to ~ulping and tle production of process steam. T`ne original Tomlinson recovery Eurnace was developed in the 1930's. Since that time, several modiEications and design improvements have been carried out, however the ori-~inal concept is still retained and universally practiced throughout the industry. ~eak black liquor is concentrated to about 65~ total solids in multiple effect evaporators and burnt in the recovery furnace at about 9~0C. The organic constituents in the black liquor provide the fuel for combustion. The resultant inorganic Na2CO3 and ~la2SO4 form a smelt (at these high tem~eratures) at the bottom of the furnace and pass throuqh a char bed where the ~a2SO4 is reduced to Na2S. Subsequently, the Na2CO3 is causticized with CaO to regenerate the NaOH required for pulping. The recovery furnace contains boiler tubes in which steam is raised for process purposes.
The two major shortcomings oE this conventional process are the smelt/water explosions and the high capital and operating costs. Periodically, the steam tubes inside the furnace burst causing water to flow on the smelt and explode. These explosions are dangerous and have sometimes caused death. They are extremely costly and the insurance premiums are high. The maintenance costs are also high because of the above.
This new method ofEers many technical and economic advantages over the conventional black liquor recovery furnace technology in which the lignin - 4 ~
derivatives are simply burnt for their fuel value.
BROAD DESCRIPTION OF THE INV~NTION
In the proposed supercritical fluid extraction process, the lignin is recovered and converted, in applicant's invented apparatuses, to higher value added products and the inorganic values are recycled to pulping.
The novel process offers the opportunity to recover the valllable lignin (natural high molecular weight polymer) and convert it to useful chemical products of a very high value-added, instead of burning it for its fuel value and thus to C2 which eventually goes up the stack. In addition, the energy savings in evaporation and chemical recovery make this process very attractivs to the industry.
Broadly stated this invention is directed to a method to extract lignin from black liquor using supercritical fluids. In another embodiment in accordance with the invention, while maintaining said lignin dissolved in the supercritical state, the same is fed in a fluidized bed catalytic reactor to convert said lignin to high value added chemical products and to special apparatuses for carrying out said method. Preferably this method is conducted using supercritical CO2 and the supercritical gas contalning lignon is reacted in a fluidized bed catalytic cracker to produce lower molecular weight higher value added products:
25 - There are many special advantages of supercritical fluid extraction of lignin and subsequent conversion to higher value added chemical products.
For example, with supercritical fluid extraction:
~3 (i) its mutual solubility with water is small and it ean therefore be used as a solvent to extraet organies from aqueous blaek liquor.
(ii) supereritieaL fluid diffuses as a gas (very high dif~-usivity) yet has the solvent earrying eapaeity of a liquid.
(iii) the reaetion rate of lignin dissolved in super-eritieal fluid in a fluidized bed of eatalyst is very high because the supereritieal fluid w-ill have the density of a liquid and yet have the diEfusivity eharaeteristies of a gas.
- (iv) the separation of lignin from the aqueous solution of inoryanie eompounds is faeilitated uith supercritieal flui~.
(v) the e~onomie benefit of this proeess is the reeovery oE lignin and its eonversion to high value added speeialty ehemicals.
This is even more so when CO2 is used, in that ease Eor example:
(vi) supercritieal CO2 has a very hi~h volatility compared with the or~anie extraeted, thus Eacilitating its separation from extract solutions for produet recovery and CO2 recycle.
(vii) The CO2 critical temperature (31.06C) and pressllre (73.3 bar) are readily accessible with well established proeess technology and equii?ment.
Supercritical CO2 is non-toxic, non-flammable, ,`~ not orrosive and readily availat~le at relatively - ~2S~3 low cost.
BRIEF DESCRIPTIO~I OF THE DRAWINGS
Fur~her features, objects and advantages will be evident follo~ing detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings in which Figure 1 is a process flow sheet illustrating one form of the present invention. Figure 2 illustrates another form a pressur-ized fluidized bed in accordance with the present invention, DESCRIPTION OF THE PRE~`ERRED EMBODI~IENTS
As .snoun in ~igure 1, the apparatus to conduct my method consicts of a pressurized autoclave extractor 10 coopt~rating v~ith a pressurized fluidized bed 12.
A CO~ feed line source 14 conveniently at ambient telnperatur2 is provided witn a flow control valve 16 ~ollowed bv a heat exchanger 17 to raise the temperature o~ the CO~ to above the supercritical temperature and a compressor 18 ~or raising the pressure of the CO2 to above the supercri~ical pressure. The compressor is itself joined via lille 20 to the nigh pressure autoclave extractor i0 which is generally thermally insulated and p.ovided wi.h conventional heating means 27, and ini,Ying means schelna~ically represented by ~1.
There .s also connectecl to said autoclave eYtractor 10 via line ~2 a po.sitive displacelnent pump 24 to ~eeti ~la-,k liquor into the autoclave at the autoclave pressure Erom line .26. The autoclave 1() is internally or ext~rnally heated i~y the conventional means schematically ~25~;3;Z83 shown by 27 when necessary. The black liquor source may be fed directly from line ~6 or may be conveniently contained in a reservoir or tank 28 and when needed fed via line 26. The CO2 Source may also originate from a storage tank 30 by maintaining the CO2 in liquid or gaseous Eorm inside the tank at a suibable pressure.
The autoclave extractor is maintained at or above the critical temperature and pressure of the solvent. In the case of CO2 this is above 31.1C and above 73.8 bar.
Any black liquor resulting from the making of pulp whether Erom kraft, sulfite or other methods may be fed into the autoclave as long as in said liquor is present the valuable lignin component or its derivatives produced during pulping.
lS The high pressure autoclave extractor lO has several functions: namely that of mixing or bringing together the supercritical fluid with the black liquor, maintaining the fluid in said supercritical fluid state, transporting the lignin from the black liquor to the supercritical fluid whereby the supercritical fluid dissolves the lignin and immediately thereaEter bringing said supercritical fluid containing said lignin to the fluidized hed 1~ by means of a line 40 joining the upper portion of the autoclave extractor to the lower p~rtion oE
the Eluidized bed 12, while removing the lignin de~leted aqueous liquor outside said autoclave extractor 10. A
pressure regulating valve 41 in line 40 controls the desired pressore in the ~luidized bed re~ctor.
~ ne way to remove said lignin depleted aqueous liquor is to provide the bottom, or the lower portion, of the autoclave where the liquid is present, with a line 42 and a pressure letdown valve 44. Then the aqueous liquor substantially lignin free, may be disposed at 46 as is well known in the art, and such as is disclosed herein-above under the headiny prior art.
While in the supercritical state, the lignin is catalytically reacted in the fluidized bed generally in its lower portion and is allowed to react with the catalyst pre~ent in said bed, to raise above said bed and to escape at the upper portion.
The upper portion of the high pressure fluidized bed ~catalytic reactor is connected to a heat exchanger 48 by means of prGduct lines 49 and 50. Line 50 is itself provided witn a pressure letdown valve 52 connecting line 54 to a product separation tank 56. The product separa-~ion tank wllich is at reduced pressure, has an upper outlet 58 for delivering the gaseous fraction, and a lower outlet 60 for delivering tne liquid and solid fraction of tne lignin deci~tives. Preferably and generally outlet 58 is connected by line fi4 to line 14 and the reservoir 30 is used onl~ to supplement ~or the lost amount o~ super-critical flu-d occuring durin~3 the Qrocess. The line 64 includes a Lil ter 66 to remove any liquid or soltd ?articles esc~ping outLet 58. ~ compression 70 is included in line 64 after the filter 66 to boost the pressure of the supercri~ic~1 fluid to the pressure in line 14.
The catalyst and other reaction conditions in the high pressure fluid bed such as pressure, temperature, .
~2~3~
g flowrate, depend upon the products one wishes to obtain.
The pressure is generally below that found in the auto-clave extractor and can be as low as 2 bars, but always above the supercritical pressure and the temperature may range as hic3h as 50C and is always over and above the supercritical temperature. Catalysts contemplated include acid-treated natural aluminosiLicates, amorphous synthetic silica~alumina combinations, crystalline synthetic silica-alumina catalysts callecl zeolites or molecular sieves, and crystalline mixtures of silica-alumina with a small unifor~nly distributed amount of rare earths contain-ed within the crystalline lattice.
Once the lignin is reacted to products they escape via line 49 and by allowing the temperature to drop lS by heat exchanger 48 as well as a drop in pressure, the supercritica! fluid is allowed to disengage from the lignin derivatives and to escape the tank 56 via the line 58. The solid and liquid particles are trapped by filter o6, while the 3as is recycled via lines 64 and 14. The lignin derivatives, which are generally liquid with ~ossibly some solids, are collected at 60. These derivatives may be separated and purified by conventional means such aS centrifu~ation, filtration, solvent extraction, distillation and crystallization.
If desired, a promoter to enhance the extraction process may be added for instance by means of a reservoir 7~ containing said promoter and joined by line 75 and pump 7 to line ~0.
~ more effi-cient way to remove the lignin ~z~o~
depleted aqueous liquor is to insert in line 42 a heat exchanger ~or raising the temperature of sai~ depleted liquor, a pressure let down valve 44 to reduce the pressure and to connect line 46 to a product separation tank 82, where the solution is allowed to flash and where steam is collected by line 8~ and a concentrated liquor containing itlorganic salts is obtained at 86.
As sho.~n in Figure 2, a pressurized fluidized bed reactor 112 is provided with insulation 114, inlet 116 and 0 partition or impervious 118 provided with outlet conduit 120 itself provided with a pressure reducing valve 122.
Within the lower portion of the fluidized reactor the fluidizable catalytic bed 1.~ is able to react on a compound dissolved in a supercritical fluid entering inlet 116 and raising through the bed 124 up to outlet conduit 120 to a disengaging zone 126 provided with heat exchanger condenser 128. The disengaging zone 1~6 has a lower portion defining a reservoir for liquid and solid products, s~id reservoir being provided with outlet 128.
The 1isengaging ~one is also provided with 9clS outlet 130.
Examples EXA~PLE 1 The Eoll~i~ing will serve only to illustrate particular elnhodiments of the invention. Weak hlack liquor containlng about 1~ solids is continuously fed to the autoclave ln. Carbon dioxide fro~n the storage tank 3n is mixed ~ith recycled CO2 and heated to 60C via heat exchanger 17 and compressed to 150 bar via compressor 18.
The autociave 10 is therrnally insulated and heated by 3Q.
~ 83 conventional means to maintain the temperature of the contents at 60C. The supercritical CO2 containing the liquor derived organic compounds leaves the autoclave via line 40 and the pressure is reduced by the pressure regulating valve 41 to the desired operating pressure of the fluidized bed which in this example i5 5 bar. In this example, the reaction produces carbon (coke) which remains on the catalyst particle and rapidly lowers its activity.
To maintain the catalyst activ;ty, the catalyst is reyenerated by burning orf this carbon using air~
Regeneration may also be carried out by having two similar fluidized beds in parallel and operated in a cyclic fashion such that while one bed is in the reaction mode, the other bed is in the regeneration mode. Another regeneration method is to have a separate regeneration bed and to move the catalyst from the reactor bed to the regeneration bed.
Since the cracking reaction is endothermic and the regeneration reaction is exothermic, the fluidized bed system may be kept in thermal halance at the desired reaction temperature of 500~. The catalyst is a highly reactive zeolite crac~ing catalyst and under tilese conditions produces a product containing benzene, toluene,zylene, phenols and longer chaill aromatic hydro-carbons. The ~roduct is collected in the separating vessel 56 and removed via 60. The product is separated into separate products via conventional technology using for e:~ample disti]iation.
. .
12~83~
- i2 -EX~MPLE 2 Although the above example l illustrates catalytic cracking in the fluidi2ed bed reactor, in E~ample 2, tne reactions carried out were hydrocraclcing that is catalytic cracking with hydrogenation super-imposed. The hydrocracking catalyst consists of a crystalline mixture of silica-alwnina wi~h a small uniformly di~tributed amount o~ rare earths contained within the crystalline lattice. The silica alumina promotes cracking while the rare earth metals encourage hydrogenation. One typical example was a cobalt/
molybdenum mi:sture on activa~ed alumina. The hydro-cracking reac~ions were generally carried out at average catalyst temperacures between 250C and 450C and at lS reactor pressures between 70 bar and 200 bar with a separate ~eed of hydrogen supplied to the fluidized bed in order to carry out the reac~ions. In a preferred emhodi-ment the unreacted hydrogen was separated fromtl1e ~roduct stream leavin~ the fiuidi~ed bed and recycled to the inlet for economic~l purposes. Since the cracking reactions are endot!1ermic and nydrogenation is exothermic, the systeln may be operate.1 in thermal balance with little or no auxil-ary el1ergy required.
Pro~ucts produced were more fully saturated aromatic co~ ounds such as cyclohexanes, cyclopentanes, cyclooctanes anJ their olefinic and aliphatic derivatives, ~nenols and l~en~ene. Further crac]cing produced straight chain m,olecules. In or~er to remove more efficiently the lignin dep~eted aclueous liquor, the system as shown on Fig. 1 was used including a heat exchanger 80 and a product separation tank. The pressurized autoclave extraction 10 operating in the order of 60C. The lignin depleted liquor in line 42 was raised to a temperature of the order of 120C to 300C. During this operation/ it became clear that steam could be obtained at ~4 and a concentrated liquor at 86 which included the sodium carbonate and other sodium salts.
In another example carried out as in Example 1 to the supercritical CO2 fed in line 14, was added a promoter (dimethyl ether) for enhancing the extraction process in au~oclave ln.
Other supercritical fluids suitable for e :t traction of Lignin were used. For instance acetone, tetrahydrofuran, dioxane and toluene. However, these supercritical fluids are generally less practical and therefor less preferred, from an indu~trial viewpoint than ~2 Al~hough they may be preferred if one wished to react the sa~e with the lignin derivatives in some cases.
Modi'ications may be made without departing froln '.he spirit o~ the invention as defined in the appended claims .
PRIOR ART
An extens-ive literature search conducted by the inventor has revealed that no one has published any in~ormation which may have bearing on ap~licant's invention:
The search has revealed that no one has thought of extracting lignin and other components from black liquor using supercritical gases, nor of reacting lignin dissolved in supercritical gaseous product in a fluidized bed catalytic reactor.
The following is a brief review of the current black liquor recovery process in which the polymeric lignin is combusted to CO2 for its fuel value: It is recognized that the Kraft process for pulp production wili be used by the industry for many years to come. The pulping chemicals NaOF~ and ~a2S extract lignin ,rom the wood to produce a pulp and a weak black liquor. The weak ; black liquor contains water, organic lignin derivatives, hydroxy acids and inorganic compounds derived ~rom the sodium. ~n essential criterion for the economic viahility ~æ
læs~3 ~of the ~Craft p~ocess is the recovery o~ inor(3anic cnemicals Eor récycle to ~ulping and tle production of process steam. T`ne original Tomlinson recovery Eurnace was developed in the 1930's. Since that time, several modiEications and design improvements have been carried out, however the ori-~inal concept is still retained and universally practiced throughout the industry. ~eak black liquor is concentrated to about 65~ total solids in multiple effect evaporators and burnt in the recovery furnace at about 9~0C. The organic constituents in the black liquor provide the fuel for combustion. The resultant inorganic Na2CO3 and ~la2SO4 form a smelt (at these high tem~eratures) at the bottom of the furnace and pass throuqh a char bed where the ~a2SO4 is reduced to Na2S. Subsequently, the Na2CO3 is causticized with CaO to regenerate the NaOH required for pulping. The recovery furnace contains boiler tubes in which steam is raised for process purposes.
The two major shortcomings oE this conventional process are the smelt/water explosions and the high capital and operating costs. Periodically, the steam tubes inside the furnace burst causing water to flow on the smelt and explode. These explosions are dangerous and have sometimes caused death. They are extremely costly and the insurance premiums are high. The maintenance costs are also high because of the above.
This new method ofEers many technical and economic advantages over the conventional black liquor recovery furnace technology in which the lignin - 4 ~
derivatives are simply burnt for their fuel value.
BROAD DESCRIPTION OF THE INV~NTION
In the proposed supercritical fluid extraction process, the lignin is recovered and converted, in applicant's invented apparatuses, to higher value added products and the inorganic values are recycled to pulping.
The novel process offers the opportunity to recover the valllable lignin (natural high molecular weight polymer) and convert it to useful chemical products of a very high value-added, instead of burning it for its fuel value and thus to C2 which eventually goes up the stack. In addition, the energy savings in evaporation and chemical recovery make this process very attractivs to the industry.
Broadly stated this invention is directed to a method to extract lignin from black liquor using supercritical fluids. In another embodiment in accordance with the invention, while maintaining said lignin dissolved in the supercritical state, the same is fed in a fluidized bed catalytic reactor to convert said lignin to high value added chemical products and to special apparatuses for carrying out said method. Preferably this method is conducted using supercritical CO2 and the supercritical gas contalning lignon is reacted in a fluidized bed catalytic cracker to produce lower molecular weight higher value added products:
25 - There are many special advantages of supercritical fluid extraction of lignin and subsequent conversion to higher value added chemical products.
For example, with supercritical fluid extraction:
~3 (i) its mutual solubility with water is small and it ean therefore be used as a solvent to extraet organies from aqueous blaek liquor.
(ii) supereritieaL fluid diffuses as a gas (very high dif~-usivity) yet has the solvent earrying eapaeity of a liquid.
(iii) the reaetion rate of lignin dissolved in super-eritieal fluid in a fluidized bed of eatalyst is very high because the supereritieal fluid w-ill have the density of a liquid and yet have the diEfusivity eharaeteristies of a gas.
- (iv) the separation of lignin from the aqueous solution of inoryanie eompounds is faeilitated uith supercritieal flui~.
(v) the e~onomie benefit of this proeess is the reeovery oE lignin and its eonversion to high value added speeialty ehemicals.
This is even more so when CO2 is used, in that ease Eor example:
(vi) supercritieal CO2 has a very hi~h volatility compared with the or~anie extraeted, thus Eacilitating its separation from extract solutions for produet recovery and CO2 recycle.
(vii) The CO2 critical temperature (31.06C) and pressllre (73.3 bar) are readily accessible with well established proeess technology and equii?ment.
Supercritical CO2 is non-toxic, non-flammable, ,`~ not orrosive and readily availat~le at relatively - ~2S~3 low cost.
BRIEF DESCRIPTIO~I OF THE DRAWINGS
Fur~her features, objects and advantages will be evident follo~ing detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings in which Figure 1 is a process flow sheet illustrating one form of the present invention. Figure 2 illustrates another form a pressur-ized fluidized bed in accordance with the present invention, DESCRIPTION OF THE PRE~`ERRED EMBODI~IENTS
As .snoun in ~igure 1, the apparatus to conduct my method consicts of a pressurized autoclave extractor 10 coopt~rating v~ith a pressurized fluidized bed 12.
A CO~ feed line source 14 conveniently at ambient telnperatur2 is provided witn a flow control valve 16 ~ollowed bv a heat exchanger 17 to raise the temperature o~ the CO~ to above the supercritical temperature and a compressor 18 ~or raising the pressure of the CO2 to above the supercri~ical pressure. The compressor is itself joined via lille 20 to the nigh pressure autoclave extractor i0 which is generally thermally insulated and p.ovided wi.h conventional heating means 27, and ini,Ying means schelna~ically represented by ~1.
There .s also connectecl to said autoclave eYtractor 10 via line ~2 a po.sitive displacelnent pump 24 to ~eeti ~la-,k liquor into the autoclave at the autoclave pressure Erom line .26. The autoclave 1() is internally or ext~rnally heated i~y the conventional means schematically ~25~;3;Z83 shown by 27 when necessary. The black liquor source may be fed directly from line ~6 or may be conveniently contained in a reservoir or tank 28 and when needed fed via line 26. The CO2 Source may also originate from a storage tank 30 by maintaining the CO2 in liquid or gaseous Eorm inside the tank at a suibable pressure.
The autoclave extractor is maintained at or above the critical temperature and pressure of the solvent. In the case of CO2 this is above 31.1C and above 73.8 bar.
Any black liquor resulting from the making of pulp whether Erom kraft, sulfite or other methods may be fed into the autoclave as long as in said liquor is present the valuable lignin component or its derivatives produced during pulping.
lS The high pressure autoclave extractor lO has several functions: namely that of mixing or bringing together the supercritical fluid with the black liquor, maintaining the fluid in said supercritical fluid state, transporting the lignin from the black liquor to the supercritical fluid whereby the supercritical fluid dissolves the lignin and immediately thereaEter bringing said supercritical fluid containing said lignin to the fluidized hed 1~ by means of a line 40 joining the upper portion of the autoclave extractor to the lower p~rtion oE
the Eluidized bed 12, while removing the lignin de~leted aqueous liquor outside said autoclave extractor 10. A
pressure regulating valve 41 in line 40 controls the desired pressore in the ~luidized bed re~ctor.
~ ne way to remove said lignin depleted aqueous liquor is to provide the bottom, or the lower portion, of the autoclave where the liquid is present, with a line 42 and a pressure letdown valve 44. Then the aqueous liquor substantially lignin free, may be disposed at 46 as is well known in the art, and such as is disclosed herein-above under the headiny prior art.
While in the supercritical state, the lignin is catalytically reacted in the fluidized bed generally in its lower portion and is allowed to react with the catalyst pre~ent in said bed, to raise above said bed and to escape at the upper portion.
The upper portion of the high pressure fluidized bed ~catalytic reactor is connected to a heat exchanger 48 by means of prGduct lines 49 and 50. Line 50 is itself provided witn a pressure letdown valve 52 connecting line 54 to a product separation tank 56. The product separa-~ion tank wllich is at reduced pressure, has an upper outlet 58 for delivering the gaseous fraction, and a lower outlet 60 for delivering tne liquid and solid fraction of tne lignin deci~tives. Preferably and generally outlet 58 is connected by line fi4 to line 14 and the reservoir 30 is used onl~ to supplement ~or the lost amount o~ super-critical flu-d occuring durin~3 the Qrocess. The line 64 includes a Lil ter 66 to remove any liquid or soltd ?articles esc~ping outLet 58. ~ compression 70 is included in line 64 after the filter 66 to boost the pressure of the supercri~ic~1 fluid to the pressure in line 14.
The catalyst and other reaction conditions in the high pressure fluid bed such as pressure, temperature, .
~2~3~
g flowrate, depend upon the products one wishes to obtain.
The pressure is generally below that found in the auto-clave extractor and can be as low as 2 bars, but always above the supercritical pressure and the temperature may range as hic3h as 50C and is always over and above the supercritical temperature. Catalysts contemplated include acid-treated natural aluminosiLicates, amorphous synthetic silica~alumina combinations, crystalline synthetic silica-alumina catalysts callecl zeolites or molecular sieves, and crystalline mixtures of silica-alumina with a small unifor~nly distributed amount of rare earths contain-ed within the crystalline lattice.
Once the lignin is reacted to products they escape via line 49 and by allowing the temperature to drop lS by heat exchanger 48 as well as a drop in pressure, the supercritica! fluid is allowed to disengage from the lignin derivatives and to escape the tank 56 via the line 58. The solid and liquid particles are trapped by filter o6, while the 3as is recycled via lines 64 and 14. The lignin derivatives, which are generally liquid with ~ossibly some solids, are collected at 60. These derivatives may be separated and purified by conventional means such aS centrifu~ation, filtration, solvent extraction, distillation and crystallization.
If desired, a promoter to enhance the extraction process may be added for instance by means of a reservoir 7~ containing said promoter and joined by line 75 and pump 7 to line ~0.
~ more effi-cient way to remove the lignin ~z~o~
depleted aqueous liquor is to insert in line 42 a heat exchanger ~or raising the temperature of sai~ depleted liquor, a pressure let down valve 44 to reduce the pressure and to connect line 46 to a product separation tank 82, where the solution is allowed to flash and where steam is collected by line 8~ and a concentrated liquor containing itlorganic salts is obtained at 86.
As sho.~n in Figure 2, a pressurized fluidized bed reactor 112 is provided with insulation 114, inlet 116 and 0 partition or impervious 118 provided with outlet conduit 120 itself provided with a pressure reducing valve 122.
Within the lower portion of the fluidized reactor the fluidizable catalytic bed 1.~ is able to react on a compound dissolved in a supercritical fluid entering inlet 116 and raising through the bed 124 up to outlet conduit 120 to a disengaging zone 126 provided with heat exchanger condenser 128. The disengaging zone 1~6 has a lower portion defining a reservoir for liquid and solid products, s~id reservoir being provided with outlet 128.
The 1isengaging ~one is also provided with 9clS outlet 130.
Examples EXA~PLE 1 The Eoll~i~ing will serve only to illustrate particular elnhodiments of the invention. Weak hlack liquor containlng about 1~ solids is continuously fed to the autoclave ln. Carbon dioxide fro~n the storage tank 3n is mixed ~ith recycled CO2 and heated to 60C via heat exchanger 17 and compressed to 150 bar via compressor 18.
The autociave 10 is therrnally insulated and heated by 3Q.
~ 83 conventional means to maintain the temperature of the contents at 60C. The supercritical CO2 containing the liquor derived organic compounds leaves the autoclave via line 40 and the pressure is reduced by the pressure regulating valve 41 to the desired operating pressure of the fluidized bed which in this example i5 5 bar. In this example, the reaction produces carbon (coke) which remains on the catalyst particle and rapidly lowers its activity.
To maintain the catalyst activ;ty, the catalyst is reyenerated by burning orf this carbon using air~
Regeneration may also be carried out by having two similar fluidized beds in parallel and operated in a cyclic fashion such that while one bed is in the reaction mode, the other bed is in the regeneration mode. Another regeneration method is to have a separate regeneration bed and to move the catalyst from the reactor bed to the regeneration bed.
Since the cracking reaction is endothermic and the regeneration reaction is exothermic, the fluidized bed system may be kept in thermal halance at the desired reaction temperature of 500~. The catalyst is a highly reactive zeolite crac~ing catalyst and under tilese conditions produces a product containing benzene, toluene,zylene, phenols and longer chaill aromatic hydro-carbons. The ~roduct is collected in the separating vessel 56 and removed via 60. The product is separated into separate products via conventional technology using for e:~ample disti]iation.
. .
12~83~
- i2 -EX~MPLE 2 Although the above example l illustrates catalytic cracking in the fluidi2ed bed reactor, in E~ample 2, tne reactions carried out were hydrocraclcing that is catalytic cracking with hydrogenation super-imposed. The hydrocracking catalyst consists of a crystalline mixture of silica-alwnina wi~h a small uniformly di~tributed amount o~ rare earths contained within the crystalline lattice. The silica alumina promotes cracking while the rare earth metals encourage hydrogenation. One typical example was a cobalt/
molybdenum mi:sture on activa~ed alumina. The hydro-cracking reac~ions were generally carried out at average catalyst temperacures between 250C and 450C and at lS reactor pressures between 70 bar and 200 bar with a separate ~eed of hydrogen supplied to the fluidized bed in order to carry out the reac~ions. In a preferred emhodi-ment the unreacted hydrogen was separated fromtl1e ~roduct stream leavin~ the fiuidi~ed bed and recycled to the inlet for economic~l purposes. Since the cracking reactions are endot!1ermic and nydrogenation is exothermic, the systeln may be operate.1 in thermal balance with little or no auxil-ary el1ergy required.
Pro~ucts produced were more fully saturated aromatic co~ ounds such as cyclohexanes, cyclopentanes, cyclooctanes anJ their olefinic and aliphatic derivatives, ~nenols and l~en~ene. Further crac]cing produced straight chain m,olecules. In or~er to remove more efficiently the lignin dep~eted aclueous liquor, the system as shown on Fig. 1 was used including a heat exchanger 80 and a product separation tank. The pressurized autoclave extraction 10 operating in the order of 60C. The lignin depleted liquor in line 42 was raised to a temperature of the order of 120C to 300C. During this operation/ it became clear that steam could be obtained at ~4 and a concentrated liquor at 86 which included the sodium carbonate and other sodium salts.
In another example carried out as in Example 1 to the supercritical CO2 fed in line 14, was added a promoter (dimethyl ether) for enhancing the extraction process in au~oclave ln.
Other supercritical fluids suitable for e :t traction of Lignin were used. For instance acetone, tetrahydrofuran, dioxane and toluene. However, these supercritical fluids are generally less practical and therefor less preferred, from an indu~trial viewpoint than ~2 Al~hough they may be preferred if one wished to react the sa~e with the lignin derivatives in some cases.
Modi'ications may be made without departing froln '.he spirit o~ the invention as defined in the appended claims .
Claims (10)
1. A method to extract lignin from a black liquor containing lignin comprising: a) dissolving a black liquor containing lignin in a supercritical fluid, at about or above critical temperature and pressure, b) separating the black liquor depleted from said lignin from the super-critical fluid containing lignin.
2. The method according to claim 1 wherein following step b), the supercritical fluid containing lignin is fed to a fluidized bed catalytic reactor to promote chemical rearrangement of said lignin into lower molecular weight lignin derivatives.
3. The method as defined in claim 2 wherein the lower molecular weight lignin derivatives are carried out from said fluidized bed to a reduced pressure and temperature tank to be disengaged from the supercritical fluid.
4. The method as defined in claim 3 wherein the super-critical fluid so disengaged is recycled.
5. The method as defined in claim 1 wherein the super-critical fluid is a member selected from the class consisting of acetone, tetrahydrofuran, dioxane, toluene.
6. The method as defined in claim 1 wherein the super-critical fluid is carbon dioxide.
7. The method as defined in claim 1 wherein a promoter is added to the supercritical fluid CO2 to accelerate and enhance the extraction process.
8. The method as defined in claim 1 wherein following step b) the supercritical fluid containing lignin is fed to a fluidized bed catalytic cracking reactor having fluidizable zeolite cracking catalyst to produce lignin derivatives including benzene, toluene, xylene, phenold and longer chain aromatic hydrocarbons.
9. The method as defined in claim 8 wherein the reaction temperature of the fluidized bed catalytic reaction is between 200° - 700° and the pressure is between 2-200 bar.
10. The method as defined in claim 8 wherein the super-critical fluid containing lignin is fed with hydrogen at a temperature between 250° - 450° under a pressure of 70-200 bar to a fluidized bed catalytic hydro-cracking reactor having fluidizable crystalline mixture of silica alumina with a small uniformly distributed amount of rare earths contained within the crystalline latice.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000540087A CA1250283A (en) | 1984-08-21 | 1987-06-18 | Method and apparatus involving supercritical fluid extraction |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000461492A CA1239528A (en) | 1983-12-22 | 1984-08-21 | Method and apparatus involving supercritical fluid extraction |
| CA000540087A CA1250283A (en) | 1984-08-21 | 1987-06-18 | Method and apparatus involving supercritical fluid extraction |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000461492A Division CA1239528A (en) | 1983-12-22 | 1984-08-21 | Method and apparatus involving supercritical fluid extraction |
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| Publication Number | Publication Date |
|---|---|
| CA1250283A true CA1250283A (en) | 1989-02-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000540087A Expired CA1250283A (en) | 1984-08-21 | 1987-06-18 | Method and apparatus involving supercritical fluid extraction |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114797967A (en) * | 2022-05-26 | 2022-07-29 | 岳阳长旺化工有限公司 | Regeneration method of deactivated catalyst, regenerated catalyst and application of regenerated catalyst |
-
1987
- 1987-06-18 CA CA000540087A patent/CA1250283A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114797967A (en) * | 2022-05-26 | 2022-07-29 | 岳阳长旺化工有限公司 | Regeneration method of deactivated catalyst, regenerated catalyst and application of regenerated catalyst |
| CN114797967B (en) * | 2022-05-26 | 2024-03-26 | 岳阳长旺化工有限公司 | Regeneration method of deactivated catalyst, regenerated catalyst and application of regenerated catalyst |
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