CA1147105A - Process for depolymerization and extraction of lignin - Google Patents
Process for depolymerization and extraction of ligninInfo
- Publication number
- CA1147105A CA1147105A CA000350566A CA350566A CA1147105A CA 1147105 A CA1147105 A CA 1147105A CA 000350566 A CA000350566 A CA 000350566A CA 350566 A CA350566 A CA 350566A CA 1147105 A CA1147105 A CA 1147105A
- Authority
- CA
- Canada
- Prior art keywords
- lignin
- cooking
- temperature
- time
- hardwood
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C1/00—Pretreatment of the finely-divided materials before digesting
- D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/20—Pulping cellulose-containing materials with organic solvents or in solvent environment
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- Paper (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Lignin is obtained in a depolymerized, soluble form from various hardwoods such as aspen by a process in which the hardwood in divided form is cooked with steam at carefully selected combinations of temperature and time, within the range 170-240°C and 2-80 minutes, and then solvent extracting the cooked wood material. It has been found that lignin undergoes a depolymerization reaction in situ in the hardwood on steam cooking, followed by a condensation and possible repolymerization reaction. The process of the present invention conducts the depolymerization reaction but substantially prevents the subsequent condensation reactions, by careful choice of time and temperature cooking conditions. The lignin so obtained in depolymerized form is useful as a chemical raw material.
Lignin is obtained in a depolymerized, soluble form from various hardwoods such as aspen by a process in which the hardwood in divided form is cooked with steam at carefully selected combinations of temperature and time, within the range 170-240°C and 2-80 minutes, and then solvent extracting the cooked wood material. It has been found that lignin undergoes a depolymerization reaction in situ in the hardwood on steam cooking, followed by a condensation and possible repolymerization reaction. The process of the present invention conducts the depolymerization reaction but substantially prevents the subsequent condensation reactions, by careful choice of time and temperature cooking conditions. The lignin so obtained in depolymerized form is useful as a chemical raw material.
Description
7:~LVS
This invention relates to lignin treatment, and moxe particularly to a process whereby lignin, a naturally occurring polymeric material, may be modified and reduced in molecular weight and thereby rendered into a form more suited to further utilization~ The invention also relates to separation methods for separating such modified lignin from other components of the initial woody material in which the lignin naturally occurs.
The production of chemicals from wood feed stock is currently substantially restricted either to the production and isolation of special fractions such as extractives, furfural etc., or to by-products of other operations conducted on the wood, such as pulping by chemical means, which are directed to wood fiber utilization. In the first type nf processes, very inefficient use is made of the wood resource.
In the second type of processes, the process conditions and yields are optimizPd with respect to fiber quality. The lignin fraction, whi-ch comprises fully 20-25% of the raw material, is degraded in such processes in a manner not conducive to further use thereof. The major chemical pulping processes employed today produce vast quantities of "lignins"
of which only a miniscule fraction finds uses other than fuel.
When one considers the enormous scale upon which wood pulping ,.. ~,._ : , ,, :
s is conducted commercially, in the manufacture of wood pulp for paper, textiles and the like, the amount of lignin which is wasted, as an essentially useless by-product of such processes, is enormous and represents a tremendous waste of a potentially valuable natural resource.
There is an increasing interest in wood/woody materials as a chemical feed st~ck, since they are a renewable resource.
When the primary object of the wood treatment is to obtain and separate chemical raw materials therefrom, many of the previously accepted and adopted considerations and constraints of conventional pulping, directed towards fiber quality and production, do not apply. The present invention is of interest in connection with the use of wood/woody materials as a chemical feed stock, and esp~cially in the obtaining of useful lignin products therefro~.
Lignin is a potentially valuable source of chemical raw materials. As a natural constituent of wood~ it is a renewable natural resource. Whilst their full constitutio~
has not been clarified with certainty in all cases, lignins are known to be complex non-polysaccharides, containing in their structure various substituted phenol structural units. On degradation, lignins of dlfferent types, from different sources, yield different substituted phenols, of significant interest as chemical raw materials. The difficulty, however, is to deuise an economically satisfactory process for separating the lignins _ 2 .
.' , : ~ ~
~'7~S
from other constituents of wood, without at the same time degrading the lignins or otherwise chemically treating them to convert them to non-useful chemical products.
The present invention is based upon our discovery that the lignin of hardwood species ~such as aspe", birch, etc.
undergoes a depolymerization reaction at high temperature, but that this reaction is closely followed by a second, condensation reaction. Unless time and temperature conditions are closely controlled, the second reaction masks and cannot effectively be separated from the first reaction, with the result that a condensed, cross-linked and possibly repolymerized lignin residue of no practical value is obtained. According to the process of our invention, however, we are able effectively to depolymerize the lignin in situ in the hardwood starting material, without permitting the condensation reaction to occur to any significant extent. This is accomplished by a careful selecti~n of cooking conditions. The result is a depolymeri.7ed form of lignin which is very readily separated from the other components of the wood, e.g. by simple so]vent extraction, and which is highly useful as a chemical raw material.
Thus according to one aspect o~ the present invention, there is provided a process for rendering ~he lignin content of natural hardwood materials substantially soluble in solvents such as dioxane-water mixtures so as to permit ready solvent .' ~7~
extractions thereo to separate at least a substantial proportion of said lignin content from the remainder of said hardwood material, which comprises cooking said hardwo~d material in divided form in the presence of steam at a pre~
selected temperature and for a preselected time chosen in combination with one another within the temperature range 170-240C, and within the time range of 2-80 minutes, 50 as to produce a steam digested hardwood residue which, after subsequent treatment with a 90/10 v/v mixture of dioxane/water under reflux, contains not more than 10% lignin residue.
The process of the present invention depolymerizes the lignin portion of the hardwood starting material in situ, thereby rendering it readily soluble in common solvents such as dioxane, alcohols, ketones, glycols, ethers, mi.xtures thereof and with water, and dilute (0.1-10%) aqueous alkalis. As such, it is readily extractable with such solvents, to separate it from the woody residues, and recoverable as a useful chemical product. The solubiliky of the lignin product in such .
. substantial amounts aemonstrates that~ by the process of the invention, it has been depolymerized but that the subsequent condensation reaction has not been allowed to proceed to any significant extent.
The process of the present invPntion may be carried out simply and effectively by heating hardwood chips, or other 7~i~35 similarly divided forms of hardwood such as shavings, sawdust etc., in ~ pressure ~essel by mea~s of direct exposure to saturated steam. As is well known, in such processes the steam pressures determine the cooking temperatures, and can be used for monitoring cooking conditions. After an appropriate time, preselected and chosen in combination with the selected il temperature of cooking, the woody material is removed from the 'i vessel~ By means of the process of the present invention, the ¦
lignin fraction thereof has been renaered soluble, and m~y in a second stage be extracted under mild conditions as described below. The process of the invention may be carried out batch- , wise, but it is most advantageous to carry out the process ~1 continuouc:ly in a suitably equipped vec;sel which permits li continuous feeding of the material thereto and discharge of ¦~
material therefrom, without loss of steam pressure, for l;
economic reasons.
In practicing the present invention, the woody material should initially contain its original moisture content, or alternatively, it should be rewet prior to entering the process.
The precise amount of water is not critical, but it is preferred that the material be fiber saturated with water at the commencement o~ the process, 50 as substantially to avoid overcooking of portions of the lignin therein.
The process of the present invention i~ preferably carried out in the absence of other added chemical digestion .
'.
reagents than water. This reduces the risk that side chemical reactions of the liqnin content may occur which will reduce the solubility of the final treated lignin. In addition, of course, it is of economic advantage to avoid the use of added chemical reagents, not only in terms of their cost of consumption, but also in terms of the effluent by-products which tend to be produced from chemical reagents, which cause expenses of disposal.
Features of the process of the present invention are graphically illustrated in the accompanying drawings in which:
FIGU~E 1 is a graph o~ temperature against time, depicting the preferred cooking conditions for use in the process of the present inVentiQn;
FIGURE 2 is a series of graphs of percenta~e lignin remaining in a cooked wood sample after treatment by the process of the invention, including solvent extraction thereof, agai.nst time of cooking, at a selection of fixed temperatures.
The process of the present .invention is eminently useful for a production both of lignin for use in subsequent
This invention relates to lignin treatment, and moxe particularly to a process whereby lignin, a naturally occurring polymeric material, may be modified and reduced in molecular weight and thereby rendered into a form more suited to further utilization~ The invention also relates to separation methods for separating such modified lignin from other components of the initial woody material in which the lignin naturally occurs.
The production of chemicals from wood feed stock is currently substantially restricted either to the production and isolation of special fractions such as extractives, furfural etc., or to by-products of other operations conducted on the wood, such as pulping by chemical means, which are directed to wood fiber utilization. In the first type nf processes, very inefficient use is made of the wood resource.
In the second type of processes, the process conditions and yields are optimizPd with respect to fiber quality. The lignin fraction, whi-ch comprises fully 20-25% of the raw material, is degraded in such processes in a manner not conducive to further use thereof. The major chemical pulping processes employed today produce vast quantities of "lignins"
of which only a miniscule fraction finds uses other than fuel.
When one considers the enormous scale upon which wood pulping ,.. ~,._ : , ,, :
s is conducted commercially, in the manufacture of wood pulp for paper, textiles and the like, the amount of lignin which is wasted, as an essentially useless by-product of such processes, is enormous and represents a tremendous waste of a potentially valuable natural resource.
There is an increasing interest in wood/woody materials as a chemical feed st~ck, since they are a renewable resource.
When the primary object of the wood treatment is to obtain and separate chemical raw materials therefrom, many of the previously accepted and adopted considerations and constraints of conventional pulping, directed towards fiber quality and production, do not apply. The present invention is of interest in connection with the use of wood/woody materials as a chemical feed stock, and esp~cially in the obtaining of useful lignin products therefro~.
Lignin is a potentially valuable source of chemical raw materials. As a natural constituent of wood~ it is a renewable natural resource. Whilst their full constitutio~
has not been clarified with certainty in all cases, lignins are known to be complex non-polysaccharides, containing in their structure various substituted phenol structural units. On degradation, lignins of dlfferent types, from different sources, yield different substituted phenols, of significant interest as chemical raw materials. The difficulty, however, is to deuise an economically satisfactory process for separating the lignins _ 2 .
.' , : ~ ~
~'7~S
from other constituents of wood, without at the same time degrading the lignins or otherwise chemically treating them to convert them to non-useful chemical products.
The present invention is based upon our discovery that the lignin of hardwood species ~such as aspe", birch, etc.
undergoes a depolymerization reaction at high temperature, but that this reaction is closely followed by a second, condensation reaction. Unless time and temperature conditions are closely controlled, the second reaction masks and cannot effectively be separated from the first reaction, with the result that a condensed, cross-linked and possibly repolymerized lignin residue of no practical value is obtained. According to the process of our invention, however, we are able effectively to depolymerize the lignin in situ in the hardwood starting material, without permitting the condensation reaction to occur to any significant extent. This is accomplished by a careful selecti~n of cooking conditions. The result is a depolymeri.7ed form of lignin which is very readily separated from the other components of the wood, e.g. by simple so]vent extraction, and which is highly useful as a chemical raw material.
Thus according to one aspect o~ the present invention, there is provided a process for rendering ~he lignin content of natural hardwood materials substantially soluble in solvents such as dioxane-water mixtures so as to permit ready solvent .' ~7~
extractions thereo to separate at least a substantial proportion of said lignin content from the remainder of said hardwood material, which comprises cooking said hardwo~d material in divided form in the presence of steam at a pre~
selected temperature and for a preselected time chosen in combination with one another within the temperature range 170-240C, and within the time range of 2-80 minutes, 50 as to produce a steam digested hardwood residue which, after subsequent treatment with a 90/10 v/v mixture of dioxane/water under reflux, contains not more than 10% lignin residue.
The process of the present invention depolymerizes the lignin portion of the hardwood starting material in situ, thereby rendering it readily soluble in common solvents such as dioxane, alcohols, ketones, glycols, ethers, mi.xtures thereof and with water, and dilute (0.1-10%) aqueous alkalis. As such, it is readily extractable with such solvents, to separate it from the woody residues, and recoverable as a useful chemical product. The solubiliky of the lignin product in such .
. substantial amounts aemonstrates that~ by the process of the invention, it has been depolymerized but that the subsequent condensation reaction has not been allowed to proceed to any significant extent.
The process of the present invPntion may be carried out simply and effectively by heating hardwood chips, or other 7~i~35 similarly divided forms of hardwood such as shavings, sawdust etc., in ~ pressure ~essel by mea~s of direct exposure to saturated steam. As is well known, in such processes the steam pressures determine the cooking temperatures, and can be used for monitoring cooking conditions. After an appropriate time, preselected and chosen in combination with the selected il temperature of cooking, the woody material is removed from the 'i vessel~ By means of the process of the present invention, the ¦
lignin fraction thereof has been renaered soluble, and m~y in a second stage be extracted under mild conditions as described below. The process of the invention may be carried out batch- , wise, but it is most advantageous to carry out the process ~1 continuouc:ly in a suitably equipped vec;sel which permits li continuous feeding of the material thereto and discharge of ¦~
material therefrom, without loss of steam pressure, for l;
economic reasons.
In practicing the present invention, the woody material should initially contain its original moisture content, or alternatively, it should be rewet prior to entering the process.
The precise amount of water is not critical, but it is preferred that the material be fiber saturated with water at the commencement o~ the process, 50 as substantially to avoid overcooking of portions of the lignin therein.
The process of the present invention i~ preferably carried out in the absence of other added chemical digestion .
'.
reagents than water. This reduces the risk that side chemical reactions of the liqnin content may occur which will reduce the solubility of the final treated lignin. In addition, of course, it is of economic advantage to avoid the use of added chemical reagents, not only in terms of their cost of consumption, but also in terms of the effluent by-products which tend to be produced from chemical reagents, which cause expenses of disposal.
Features of the process of the present invention are graphically illustrated in the accompanying drawings in which:
FIGU~E 1 is a graph o~ temperature against time, depicting the preferred cooking conditions for use in the process of the present inVentiQn;
FIGURE 2 is a series of graphs of percenta~e lignin remaining in a cooked wood sample after treatment by the process of the invention, including solvent extraction thereof, agai.nst time of cooking, at a selection of fixed temperatures.
The process of the present .invention is eminently useful for a production both of lignin for use in subsequent
2~ chemical synthesis as a source of chemical raw materials, such as vanilli.n, and also in the production of pulps from hardwoo~, in a simple, economical manner. Thus, both the lignin residues which are formed, and the cooked woody material, are usefult commercial products. The woody product after cooking is effect-ively a hardwood pulp, which is useful ~or adding in small s amount~ to other cellulose pulps for the making of various types of paper. The original hardwoods which can be used in the process of the invention, including aspen, poplar, eucalyptus, birch and the like, are very fast growing materials, thereby enhancing the general economics o~ the process.
Fig. 1 of the accompanying drawings shows the extent of combinations of temperatures and times for cooking, for use in the process of the present invention, to obtain a readily soluble lignin fraction. Within the overall area designated A, substantially any combination of temperature and time can be chosen for cooking, so as to yield a cooked woody product, the lignin content of which is substantially extractable with 90/10 dioxane/water mixtures under reflux or a dilute aqueous alkali at about 60C, to leave a woody material of less than about - 10~ of lignin residue. Within the smaller area B designated on Fig. 1, i.e. the shorter time range of area A, temperature and time condition combinations are found which are preferred, because of the lower energy requ,irements thereby leaaing to enhanced economics of the process, and also reducing the risk of over cooking the material so as to increase the non-soluble portion of the lignin. Within this area, temperature and time conditions are found which, when employed, lead to the production of cooked hardwood residues which after the aforesaid solvent extraction have less than about 7% lignin residues.
.
.
7~5 Fig. 2 depicts the extractability of the liqnin depol~meriæation products resulting from treatment according to the process of the present invention. As can be seen, the exact time and temperature conditions are critical, and this `
relationship is a key element of the process according to the invention. It is evident that, at each temperature, there is a cooking time at which depolymerization (extractabi-ity) of l the lignin is maximized. It is further evident that the ii extent of desired reaction increases with temperature, but there is a decrease in the difference between results of successive increases of given temperature towards the upper end of the range. This is in accordance with the believed mechanism of the successive first order reactions.
The followinq table illustrates oPtimum time/
temperature values for aspen wood. In the table, L values indicatP percent residual liqnin after extraction with a solvent comprising 90~ dioxanP, and 10~ water by weight.
Temp C Time (opti~al) L
175 80 7.1 185 60 4.3 195 25 2.4 205 ~ 16 1.8 215 4 1.7 The invention and conditions for carrying the process into practice are further described in the followinq specific examples:
~'7~
30G (dry weight) of chips of aspen (Populus tremuloides), apProximately 1/8 inch thick, 5/8 inch long and 1/4 to 3/4 inch wide, containing 50~ moisture were placed i~
an autoclave and heated to 205C. After 1~ minutes at this temperature, the vessel was rapidly cooled and opened. The chips were found to be completely softened and readily disintegrated, e.g. between the fingers or by the action of a small laboratory stirrer. The resulting wood pulp was essentially free from lumps and undisintegrated wood.
Extraction with 0.5~ sodium hydroxide solution solubilized approximately half of the sample. The residual lignin in the solid, woody material was 4.7%, as compared to approxlmately 20% in the starting material. Accordingly, ~8%
of the initial lignin had been rendered solublel i.e. de-polymerized, without subsequent condensation by the process of the example.
Example 2. The aspen woodpulp of example 1 was extracted in a Soxhlet extractor with boiling 90% dioxane -10~ water, which dissolved most of the lignin present. The woodpulp, after washing and drying, was found to weigh 14.6g, for a yield o 49 percent on the original wood. The fibers were light brown in colour, and contained 3.7 percent lignin and 1.4 percent xylan. The starting wood had contained 17.1 percent lignin and 14.9 percent xylan.
When the woodpulp of Example 1 was extracted with .
g _ :
~7~
pure ioxane, or with dioxane diluted with water to 50% dioxane, higher yields of woodpulp were obtained, 51.5 and 52~5 percent respectively. These woodpulps contained higher lignin concentrations, 5.8 and 5.0 percent respectively, but the same xylan content, 1.4 percent.
Example 3. 30 g tOD) of chipped eucalyptus (Eucalypt~ls saligna~
containing 50~ moisture were placed in an autoclave and heated to 200C. After 30 minutes the autoclave was rapidly cooled and opened. The chips were found to be softened and readily 10 aisintegrated.
Extraction of the treated chips with boiling 90%
dioxane - 10% water solubilized 43% of the raw material and the residue contained 10% lignin. Accordingly as the raw material had a lignin content of 24~, 76% of the lignin was solublized by our process.
Example 4. Aspen chips at 50~ moisture were fed at the rate of 280 pounds per hour into a horizontal continuous digestor equipped with an internal screw conveyor. Steam at 265 psig ~as admitted near the entrance to the digestor to raise the temperature of the chips to 208C. The screw conveyor rate was adjusted to give a residence time in the digestor of 10 minutes. The cooled chips were disintegrated after release from the digestor~ The resulting woodpulp was filtered and washed on conventional equipment. The yield of fiber was calculated to be 70 percent based on the starting wood. It _ 10 _ ' .
~7~
was brown in color~ The woodpulp was then extracted with 0.2~
hot sodium hydroxide solution in an open vessel. The resulting woodpulp was 1ight brown in color. The yield based on wood was 45% and the lignin content thereof was about 4.5%, as compared to a starting lignin content in the wood of about 20%.
Example 5. Chips of fast-growing poplar Clone No. 1 45/51 were analyzed and found to have a lignin content of 21.5%.
This poplar is notable in that in the cold climate of Canada it grows rapidly, the measured rate of wood production being 11 metric tons per hectare each year. Upon heating rapidly to 200C, and maintaining at that temperature for 30 minutes, brown woodpulp was obtained in 73~ yield. After extraction with 0.5% hot sodium hydroxide solution for 90 minutes in an open vessel, the yield was reduced to 47%. The light brown woodpulp had a lignin content of 13.9%.
It should be noted that in the example cited above, a substantially greater percentage of the wood than that accounted for by the lignin is in fact solublized. This is a consequence of the degradation of the pentasans and other components comprising the hemicelluloses. These reactions are well known and form the basis for certain established silvichemical production processes .
~ . ~
Fig. 1 of the accompanying drawings shows the extent of combinations of temperatures and times for cooking, for use in the process of the present invention, to obtain a readily soluble lignin fraction. Within the overall area designated A, substantially any combination of temperature and time can be chosen for cooking, so as to yield a cooked woody product, the lignin content of which is substantially extractable with 90/10 dioxane/water mixtures under reflux or a dilute aqueous alkali at about 60C, to leave a woody material of less than about - 10~ of lignin residue. Within the smaller area B designated on Fig. 1, i.e. the shorter time range of area A, temperature and time condition combinations are found which are preferred, because of the lower energy requ,irements thereby leaaing to enhanced economics of the process, and also reducing the risk of over cooking the material so as to increase the non-soluble portion of the lignin. Within this area, temperature and time conditions are found which, when employed, lead to the production of cooked hardwood residues which after the aforesaid solvent extraction have less than about 7% lignin residues.
.
.
7~5 Fig. 2 depicts the extractability of the liqnin depol~meriæation products resulting from treatment according to the process of the present invention. As can be seen, the exact time and temperature conditions are critical, and this `
relationship is a key element of the process according to the invention. It is evident that, at each temperature, there is a cooking time at which depolymerization (extractabi-ity) of l the lignin is maximized. It is further evident that the ii extent of desired reaction increases with temperature, but there is a decrease in the difference between results of successive increases of given temperature towards the upper end of the range. This is in accordance with the believed mechanism of the successive first order reactions.
The followinq table illustrates oPtimum time/
temperature values for aspen wood. In the table, L values indicatP percent residual liqnin after extraction with a solvent comprising 90~ dioxanP, and 10~ water by weight.
Temp C Time (opti~al) L
175 80 7.1 185 60 4.3 195 25 2.4 205 ~ 16 1.8 215 4 1.7 The invention and conditions for carrying the process into practice are further described in the followinq specific examples:
~'7~
30G (dry weight) of chips of aspen (Populus tremuloides), apProximately 1/8 inch thick, 5/8 inch long and 1/4 to 3/4 inch wide, containing 50~ moisture were placed i~
an autoclave and heated to 205C. After 1~ minutes at this temperature, the vessel was rapidly cooled and opened. The chips were found to be completely softened and readily disintegrated, e.g. between the fingers or by the action of a small laboratory stirrer. The resulting wood pulp was essentially free from lumps and undisintegrated wood.
Extraction with 0.5~ sodium hydroxide solution solubilized approximately half of the sample. The residual lignin in the solid, woody material was 4.7%, as compared to approxlmately 20% in the starting material. Accordingly, ~8%
of the initial lignin had been rendered solublel i.e. de-polymerized, without subsequent condensation by the process of the example.
Example 2. The aspen woodpulp of example 1 was extracted in a Soxhlet extractor with boiling 90% dioxane -10~ water, which dissolved most of the lignin present. The woodpulp, after washing and drying, was found to weigh 14.6g, for a yield o 49 percent on the original wood. The fibers were light brown in colour, and contained 3.7 percent lignin and 1.4 percent xylan. The starting wood had contained 17.1 percent lignin and 14.9 percent xylan.
When the woodpulp of Example 1 was extracted with .
g _ :
~7~
pure ioxane, or with dioxane diluted with water to 50% dioxane, higher yields of woodpulp were obtained, 51.5 and 52~5 percent respectively. These woodpulps contained higher lignin concentrations, 5.8 and 5.0 percent respectively, but the same xylan content, 1.4 percent.
Example 3. 30 g tOD) of chipped eucalyptus (Eucalypt~ls saligna~
containing 50~ moisture were placed in an autoclave and heated to 200C. After 30 minutes the autoclave was rapidly cooled and opened. The chips were found to be softened and readily 10 aisintegrated.
Extraction of the treated chips with boiling 90%
dioxane - 10% water solubilized 43% of the raw material and the residue contained 10% lignin. Accordingly as the raw material had a lignin content of 24~, 76% of the lignin was solublized by our process.
Example 4. Aspen chips at 50~ moisture were fed at the rate of 280 pounds per hour into a horizontal continuous digestor equipped with an internal screw conveyor. Steam at 265 psig ~as admitted near the entrance to the digestor to raise the temperature of the chips to 208C. The screw conveyor rate was adjusted to give a residence time in the digestor of 10 minutes. The cooled chips were disintegrated after release from the digestor~ The resulting woodpulp was filtered and washed on conventional equipment. The yield of fiber was calculated to be 70 percent based on the starting wood. It _ 10 _ ' .
~7~
was brown in color~ The woodpulp was then extracted with 0.2~
hot sodium hydroxide solution in an open vessel. The resulting woodpulp was 1ight brown in color. The yield based on wood was 45% and the lignin content thereof was about 4.5%, as compared to a starting lignin content in the wood of about 20%.
Example 5. Chips of fast-growing poplar Clone No. 1 45/51 were analyzed and found to have a lignin content of 21.5%.
This poplar is notable in that in the cold climate of Canada it grows rapidly, the measured rate of wood production being 11 metric tons per hectare each year. Upon heating rapidly to 200C, and maintaining at that temperature for 30 minutes, brown woodpulp was obtained in 73~ yield. After extraction with 0.5% hot sodium hydroxide solution for 90 minutes in an open vessel, the yield was reduced to 47%. The light brown woodpulp had a lignin content of 13.9%.
It should be noted that in the example cited above, a substantially greater percentage of the wood than that accounted for by the lignin is in fact solublized. This is a consequence of the degradation of the pentasans and other components comprising the hemicelluloses. These reactions are well known and form the basis for certain established silvichemical production processes .
~ . ~
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for depolymerizing the lignin content of natural hardwood material and rendering it substantially soluble in dioxane-water mixtures so as to permit ready solvent extraction thereof to separate at least a substantial proportion of said lignin content from the remainder of said hardwood material, which comprises cooking said hardwood material in divided form in the presence of steam at a pre-selected temperature and for a preselected time chosen in combination with one another within the temperature range 170°C to 240°C, and within the time range of 2 minutes to 80 minutes, with lower temperatures being chosen in combination with longer times within the range/ and vice versa, so as to produce a steam digested hardwood residue which, after subsequent treatment with a 90/10 v/v dioxane/water mixture under reflux contains not more than 10% lignin residue.
2. The process of claim 1 wherein the cooking of said hardwood material is conducted in the absence of effective amounts of added digestor chemicals other than water.
3. The process of claim 2 wherein the temperaure of cooking is from about 175-225°C and the time and temperature of cooking are selected in combination within the range defined by area A shown on the graph constituting Fig. 1 attached hereto.
4. The process of claim 3 wherein the time and temperature of cooking are select d in combination within the range defined by area B shown on the graph constituting Fig. 1 attached hereto, the time of cooking being not greater than 30 minutes.
5. The process of claim 2, claim 3 or claim 4 wherein the hardwood material is selected from aspen, poplar, birch and eucalyptus.
6. A process of extracting from hardwood material a substantial proportion of the lignin thereof in a form which is depolymerized and substantially soluble in dilute aqueous alkali, which comprises the steps of cooking the hardwood material with steam and in the substantial absence of other added wood-digesting chemicals for a time and temperature preselected in combination with one another within the range 2-80 minutes and 170-240°C, with the proviso that when the time is selected to be greater than 30 minutes the temperature is selected to be less than 220°C, so as to render at least 70% of the lignin content of the hardwood soluble in dilute aqueous alkali;
treating the cooked hardwood material with a solvent for the depolymerized lignin so formed to extract at least a substantial proportion of the lignin as a solution in said solvent;
and recovering the depolymerized lignin from solution in said solvent.
treating the cooked hardwood material with a solvent for the depolymerized lignin so formed to extract at least a substantial proportion of the lignin as a solution in said solvent;
and recovering the depolymerized lignin from solution in said solvent.
7. The process of claim 6 wherein the solvent is selected from dilute aqueous alkali, water, and dioxane/water mixtures.
8. The process of claim 6 wherein the cooking takes place under steam pressure in a closed digestor vessel.
9. The process of claim 8 wherein the time of cooking is from 4-30 minutes and the temperature of cooking is from 175-225°C.
10. The process of claim 8 wherein the temperature of cooking is from about 175-225°C, and the time and temperature are selected in combination within the range defined by area A
shown on the graph constituting Fig. 1 attached hereto.
shown on the graph constituting Fig. 1 attached hereto.
11. The process of claim 7, claim 9 or claim 10 wherein the hardwood material is selected from aspen, poplar, birch and eucalyptus.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000350566A CA1147105A (en) | 1980-04-24 | 1980-04-24 | Process for depolymerization and extraction of lignin |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000350566A CA1147105A (en) | 1980-04-24 | 1980-04-24 | Process for depolymerization and extraction of lignin |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1147105A true CA1147105A (en) | 1983-05-31 |
Family
ID=4116772
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000350566A Expired CA1147105A (en) | 1980-04-24 | 1980-04-24 | Process for depolymerization and extraction of lignin |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1147105A (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0472820A2 (en) * | 1990-08-17 | 1992-03-04 | Alcell Technologies Inc. | Continuous solvent pulping and washing processes and apparatus |
| US5728265A (en) * | 1995-06-12 | 1998-03-17 | Henkel Corporation | Process for enhancing white liquor penetration into wood chips by contacting the chips with a mixture of the white liquor and a polymethylalkyl siloxane |
| US5788812A (en) * | 1985-11-05 | 1998-08-04 | Agar; Richard C. | Method of recovering furfural from organic pulping liquor |
| US8449680B2 (en) | 2008-07-24 | 2013-05-28 | Mascoma Canada Inc. | Method and apparatus for treating a cellulosic feedstock |
| US8545633B2 (en) | 2009-08-24 | 2013-10-01 | Abengoa Bioenergy New Technologies, Inc. | Method for producing ethanol and co-products from cellulosic biomass |
| US8778084B2 (en) | 2008-07-24 | 2014-07-15 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for treating a cellulosic feedstock |
| US8900370B2 (en) | 2008-07-24 | 2014-12-02 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US8911557B2 (en) | 2008-07-24 | 2014-12-16 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US8915644B2 (en) | 2008-07-24 | 2014-12-23 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US9004742B2 (en) | 2009-01-23 | 2015-04-14 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US9010522B2 (en) | 2008-07-24 | 2015-04-21 | Abengoa Bioenergy New Technologies, Llc | Method and apparatus for conveying a cellulosic feedstock |
| CN114426678A (en) * | 2020-10-10 | 2022-05-03 | 中国石油化工股份有限公司 | Lignin-based flame-retardant char-forming agent and synthesis method and application thereof |
-
1980
- 1980-04-24 CA CA000350566A patent/CA1147105A/en not_active Expired
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5788812A (en) * | 1985-11-05 | 1998-08-04 | Agar; Richard C. | Method of recovering furfural from organic pulping liquor |
| EP0472820A2 (en) * | 1990-08-17 | 1992-03-04 | Alcell Technologies Inc. | Continuous solvent pulping and washing processes and apparatus |
| EP0472820A3 (en) * | 1990-08-17 | 1992-12-23 | Kamyr, Inc. | Continuous solvent pulping and washing processes and apparatus |
| EP0763622A3 (en) * | 1990-08-17 | 1999-08-25 | Alcell Technologies Inc. | Continuous solvent pulping and washing processes and apparatus |
| US5728265A (en) * | 1995-06-12 | 1998-03-17 | Henkel Corporation | Process for enhancing white liquor penetration into wood chips by contacting the chips with a mixture of the white liquor and a polymethylalkyl siloxane |
| US8911557B2 (en) | 2008-07-24 | 2014-12-16 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US8778084B2 (en) | 2008-07-24 | 2014-07-15 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for treating a cellulosic feedstock |
| US8900370B2 (en) | 2008-07-24 | 2014-12-02 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US8449680B2 (en) | 2008-07-24 | 2013-05-28 | Mascoma Canada Inc. | Method and apparatus for treating a cellulosic feedstock |
| US8915644B2 (en) | 2008-07-24 | 2014-12-23 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US9010522B2 (en) | 2008-07-24 | 2015-04-21 | Abengoa Bioenergy New Technologies, Llc | Method and apparatus for conveying a cellulosic feedstock |
| US9004742B2 (en) | 2009-01-23 | 2015-04-14 | Abengoa Bioenergy New Technologies, Llc. | Method and apparatus for conveying a cellulosic feedstock |
| US8545633B2 (en) | 2009-08-24 | 2013-10-01 | Abengoa Bioenergy New Technologies, Inc. | Method for producing ethanol and co-products from cellulosic biomass |
| US9335043B2 (en) | 2009-08-24 | 2016-05-10 | Abengoa Bioenergy New Technologies, Inc. | Method for producing ethanol and co-products from cellulosic biomass |
| CN114426678A (en) * | 2020-10-10 | 2022-05-03 | 中国石油化工股份有限公司 | Lignin-based flame-retardant char-forming agent and synthesis method and application thereof |
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