U.S. patent application number 15/609836 was filed with the patent office on 2017-11-23 for processes for producing lignin-coated hydrophobic cellulose, and compositions and products produced therefrom.
The applicant listed for this patent is API Intellectual Property Holdings, LLC. Invention is credited to Kimberly NELSON, Ryan O'CONNOR, Vesa PYLKKANEN, Theodora RETSINA.
Application Number | 20170335138 15/609836 |
Document ID | / |
Family ID | 53797533 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170335138 |
Kind Code |
A1 |
NELSON; Kimberly ; et
al. |
November 23, 2017 |
PROCESSES FOR PRODUCING LIGNIN-COATED HYDROPHOBIC CELLULOSE, AND
COMPOSITIONS AND PRODUCTS PRODUCED THEREFROM
Abstract
Processes disclosed are capable of converting biomass into
high-crystallinity, hydrophobic cellulose. In some variations, the
process includes fractionating biomass with an acid (such as sulfur
dioxide), a solvent (such as ethanol), and water, to generate
cellulose-rich solids and a liquid containing hemicellulose and
lignin; and depositing lignin onto cellulose fibers to produce
lignin-coated cellulose materials (such as dissolving pulp). The
crystallinity of the cellulose material may be 80% or higher,
translating into good reinforcing properties for composites.
Optionally, sugars derived from amorphous cellulose and
hemicellulose may be separately fermented, such as to monomers for
various polymers. These polymers may be combined with the
hydrophobic cellulose to form completely renewable composites.
Inventors: |
NELSON; Kimberly; (Atlanta,
GA) ; RETSINA; Theodora; (Atlanta, GA) ;
PYLKKANEN; Vesa; (Atlanta, GA) ; O'CONNOR; Ryan;
(Minnetrista, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
API Intellectual Property Holdings, LLC |
Minnetrista |
MN |
US |
|
|
Family ID: |
53797533 |
Appl. No.: |
15/609836 |
Filed: |
May 31, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14606200 |
Jan 27, 2015 |
|
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|
15609836 |
|
|
|
|
61941241 |
Feb 18, 2014 |
|
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61980996 |
Apr 17, 2014 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 97/02 20130101;
C12P 19/14 20130101; C09D 197/005 20130101; C12P 2203/00 20130101;
C13K 1/02 20130101; D21H 17/25 20130101; Y02E 50/10 20130101; Y02E
50/16 20130101; C08L 5/14 20130101; Y10T 428/2991 20150115; D21H
19/34 20130101; C12P 19/02 20130101; C08H 6/00 20130101; C08H 8/00
20130101; C09K 2208/08 20130101; C12P 7/10 20130101; C08B 37/0057
20130101; C09K 8/035 20130101; D21H 19/52 20130101; D21H 17/23
20130101; C04B 16/02 20130101; C08L 97/005 20130101; C08L 1/02
20130101; C08L 1/02 20130101; C08L 97/02 20130101; C08L 97/02
20130101; C08L 1/02 20130101; C04B 16/02 20130101; C04B 20/1029
20130101 |
International
Class: |
C09D 197/00 20060101
C09D197/00; C08B 37/00 20060101 C08B037/00; C08H 7/00 20110101
C08H007/00; C08H 8/00 20100101 C08H008/00; C08L 1/02 20060101
C08L001/02; C08L 5/14 20060101 C08L005/14; C08L 97/02 20060101
C08L097/02; C12P 19/14 20060101 C12P019/14; C12P 19/02 20060101
C12P019/02; C12P 7/10 20060101 C12P007/10; C13K 1/02 20060101
C13K001/02; C09K 8/035 20060101 C09K008/035; C08L 97/00 20060101
C08L097/00; C04B 16/02 20060101 C04B016/02 |
Claims
1. A process for producing a lignin-coated cellulose material, said
process comprising: (a) providing a lignocellulosic biomass
feedstock; (b) fractionating said feedstock in the presence of an
acid, a solvent for lignin, and water, to generate cellulose-rich
solids and a liquid containing hemicellulose and lignin; (c)
depositing at least some of said lignin, from said liquid, onto a
surface of said cellulose-rich solids to generate a lignin-coated
cellulose material; (d) optionally mechanically treating said
lignin-coated cellulose material; and (e) recovering said
lignin-coated cellulose material, wherein cellulose crystallinity
of said lignin-coated cellulose material is at least 60%, and
wherein said lignin-coated cellulose material is at least partially
hydrophobic.
2. The process of claim 1, wherein said acid is selected from the
group consisting of sulfur dioxide, sulfurous acid, sulfur
trioxide, sulfuric acid, lignosulfonic acid, and combinations
thereof.
3. The process of claim 2, wherein said acid is sulfur dioxide.
4. The process of claim 3, wherein sulfur dioxide concentration in
step (b) is from about 12 wt % to about 30 wt %.
5. The process of claim 1, wherein fractionation temperature in
step (b) is from about 140.degree. C. to about 170.degree. C.
6. The process of claim 1, wherein fractionation time in step (b)
is from about 1 hour to about 2 hours.
7. The process of claim 1, wherein step (d) is performed and
wherein steps (c) and (d) are integrated.
8. The process of claim 1, wherein step (d) is performed and
wherein said lignin-coated cellulose material is treated with a
total mechanical energy of less than about 500 kilowatt-hours per
ton of said lignin-coated cellulose material.
9. The process of claim 1, wherein said process further comprises
treatment of said lignin-coated cellulose material with one or more
enzymes.
10. The process of claim 1, wherein said process further comprises
treatment of said lignin-coated cellulose material with one or more
acids.
11. The process of claim 10, wherein said one or more acids are
selected from the group consisting of sulfur dioxide, sulfurous
acid, lignosulfonic acid, acetic acid, formic acid, and
combinations thereof.
12. The process of claim 1, wherein said process further comprises
treatment of said lignin-coated cellulose material with heat.
13. The process of claim 1, wherein said cellulose crystallinity of
said lignin-coated cellulose material is at least 70%.
14. The process of claim 13, wherein said cellulose crystallinity
of said lignin-coated cellulose material is at least 80%.
15. The process of claim 1, wherein said lignin-coated cellulose
material includes, or is characterized as, lignin-coated dissolving
pulp.
16. The process of claim 1, wherein said lignin-coated cellulose
material includes, or is characterized as, lignin-coated
fibrillated cellulose.
17. The process of claim 1, wherein said lignin-coated cellulose
material includes, or is characterized as, lignin-coated
microcrystalline cellulose.
18. The process of claim 1, wherein said lignin-coated cellulose
material includes, or is characterized as, lignin-coated
nanocellulose.
19. The process of claim 1, said process further comprising
chemically converting said lignin-coated cellulose material to one
or more lignin-coated cellulose derivatives.
20. The process of claim 19, wherein said lignin-coated cellulose
derivatives are selected from the group consisting of cellulose
esters, cellulose ethers, cellulose ether esters, alkylated
cellulose compounds, cross-linked cellulose compounds,
acid-functionalized cellulose compounds, base-functionalized
cellulose compounds, and combinations thereof.
Description
PRIORITY DATA
[0001] This patent application is a continuation application of
U.S. patent application Ser. No. 14/606,200, filed Jan. 27, 2015,
which claims priority to U.S. Provisional Patent App. No.
61/941,241, filed Feb. 18, 2014 and to U.S. Provisional Patent App.
No. 61/980,996, filed Apr. 17, 2014, each of which is hereby
incorporated by reference herein.
FIELD
[0002] The present invention generally relates to cellulose and
related materials produced by fractionating lignocellulosic biomass
and further processing the cellulose fraction.
BACKGROUND
[0003] Biomass refining (or biorefining) has become more prevalent
in industry. Cellulose fibers and sugars, hemicellulose sugars,
lignin, syngas, and derivatives of these intermediates are being
utilized for chemical and fuel production. Indeed, we now are
observing the commercialization of integrated biorefineries that
are capable of processing incoming biomass much the same as
petroleum refineries now process crude oil. Underutilized
lignocellulosic biomass feedstocks have the potential to be much
cheaper than petroleum, on a carbon basis, as well as much better
from an environmental life-cycle standpoint.
[0004] Lignocellulosic biomass is the most abundant renewable
material on the planet and has long been recognized as a potential
feedstock for producing chemicals, fuels, and materials.
Lignocellulosic biomass normally comprises primarily cellulose,
hemicellulose, and lignin. Cellulose and hemicellulose are natural
polymers of sugars, and lignin is an aromatic/aliphatic hydrocarbon
polymer reinforcing the entire biomass network. Some forms of
biomass (e.g., recycled materials) do not contain
hemicellulose.
[0005] Cellulose or cellulose derivatives can be used in a wide
variety of applications such as polymer reinforcement,
anti-microbial films, biodegradable food packaging, printing
papers, pigments and inks, paper and board packaging, barrier
films, adhesives, biocomposites, wound healing, pharmaceuticals and
drug delivery, textiles, water-soluble polymers, construction
materials, recyclable interior and structural components for the
transportation industry, rheology modifiers, low-calorie food
additives, cosmetics thickeners, pharmaceutical tablet binders,
bioactive paper, pickering stabilizers for emulsion and particle
stabilized foams, paint formulations, films for optical switching,
and detergents.
[0006] For some cellulose applications, it would be beneficial to
increase the hydrophobicity of the cellulose. Therefore, improved
processes are needed in the art.
SUMMARY
[0007] In some variations, the present invention provides a process
for producing a lignin-coated cellulose material, the process
comprising: [0008] (a) providing a lignocellulosic biomass
feedstock; [0009] (b) fractionating the feedstock in the presence
of an acid, a solvent for lignin, and water, to generate
cellulose-rich solids and a liquid containing hemicellulose and
lignin; [0010] (c) depositing at least some of the lignin, from the
liquid, onto a surface of the cellulose-rich solids to generate a
lignin-coated cellulose material; [0011] (d) optionally
mechanically treating the lignin-coated cellulose material; and
[0012] (e) recovering the lignin-coated cellulose material, [0013]
wherein the cellulose crystallinity of the lignin-coated cellulose
material is at least 60%, and wherein the lignin-coated cellulose
material is at least partially hydrophobic.
[0014] In some embodiments, the acid is selected from the group
consisting of sulfur dioxide, sulfurous acid, sulfur trioxide,
sulfuric acid, lignosulfonic acid, and combinations thereof. In
certain embodiments, the acid is sulfur dioxide. In step (b),
exemplary conditions include SO.sub.2 concentration from about 12
wt % to about 30 wt %, fractionation temperature from about
140.degree. C. to about 170.degree. C., and fractionation time is
from about 1 hour to about 2 hours.
[0015] Step (c) is performed either in the same unit as step (b),
such as a digestor, or in another unit. Step (c) may occur
sequentially following step (b), or simultaneously with step (b),
or some combination thereof. Conditions may be selected or
optimized to promote deposition of lignin onto the cellulose. For
example, longer time, higher temperature, lower pH, and/or lower
concentration of the solvent for lignin may be utilized to cause or
promote lignin deposition during step (c). In some embodiments,
conditions of step (c) are different than those of step (b), and
physically separate units are employed (or employed in one unit in
a batch-wise process). In other embodiments, a single set of
conditions for steps (b) and (c) are selected, and steps (b) and
(c) are combined into a single reactor.
[0016] When step (d) is performed, steps (c) and (d) may be
integrated so that some lignin is physically deposited onto
cellulose during mechanical treatment. In some embodiments, the
lignin-coated cellulose material is treated with a total mechanical
energy of less than about 1000 kilowatt-hours per ton of the
lignin-coated cellulose material, such as less than about 500
kilowatt-hours per ton of the lignin-coated cellulose material. In
certain embodiments, the total mechanical energy is from about 100
kilowatt-hours to about 400 kilowatt-hours per ton of the
lignin-coated cellulose material.
[0017] The process may further include treatment of the
lignin-coated cellulose material with one or more enzymes or with
one or more acids. Such acids may be selected from the group
consisting of sulfur dioxide, sulfurous acid, lignosulfonic acid,
acetic acid, formic acid, and combinations thereof. Alternatively
or additionally, the process may further include treatment of the
lignin-coated cellulose material with heat.
[0018] In some embodiments, the cellulose crystallinity of the
lignin-coated cellulose material is at least 70%, such as at least
80% or 85%.
[0019] The lignin-coated cellulose material may include or consist
essentially of lignin-coated dissolving pulp, lignin-coated
fibrillated cellulose, lignin-coated microcrystalline cellulose,
lignin-coated nanocellulose, or other forms of lignin-coated
pulp.
[0020] The lignin-coated cellulose material may be characterized by
an average degree of polymerization from about 100 to about 1500,
such as from about 300 to about 700 or from about 150 to about
250.
[0021] Optionally, the process further comprises hydrolyzing
amorphous cellulose, contained in the lignocellulosic biomass
feedstock, into glucose, and optionally fermenting the glucose to a
fermentation product. Also optionally, the process further
comprises recovering, fermenting, or further treating
hemicellulosic sugars derived from the hemicellulose.
[0022] In certain embodiments, the process comprises fermenting the
hemicellulosic sugars to produce a monomer or precursor thereof;
polymerizing the monomer to produce a polymer; and combining the
polymer and the lignin-coated cellulose material to form a
polymer-cellulose composite.
[0023] In some embodiments, the process further comprises
recovering, combusting, or further treating the lignin that does
not deposit onto the cellulose-rich solids during step (c). The
process may further comprise chemically converting the
lignin-coated cellulose material to one or more lignin-coated
cellulose derivatives such as cellulose esters, cellulose ethers,
cellulose ether esters, alkylated cellulose compounds, cross-linked
cellulose compounds, acid-functionalized cellulose compounds,
base-functionalized cellulose compounds, or combinations
thereof.
[0024] Some variations provide a process for producing a
hydrophobic cellulose material, the process comprising: [0025] (a)
providing a lignocellulosic biomass feedstock; [0026] (b)
fractionating the feedstock in the presence of an acid, a solvent
for lignin, and water, to generate cellulose-rich solids and a
liquid containing hemicellulose and lignin, wherein a portion of
the lignin deposits onto a surface of the cellulose-rich solids,
thereby rendering the cellulose-rich solids at least partially
hydrophobic; [0027] (c) optionally mechanically treating the
cellulose-rich solids to form cellulose fibrils and/or cellulose
crystals, having a crystallinity of at least 60%; and [0028] (d)
recovering the hydrophobic cellulose material.
[0029] In some embodiments, the acid is selected from the group
consisting of sulfur dioxide, sulfurous acid, sulfur trioxide,
sulfuric acid, lignosulfonic acid, and combinations thereof.
[0030] The crystallinity of the hydrophobic cellulose material may
at least 70% or at least 80%. The hydrophobic cellulose material
may be characterized by an average degree of polymerization from
about 100 to about 1500, such as about 300 to about 700 or about
150 to about 250.
[0031] Optionally, the process further comprises chemically
modifying the lignin to increase hydrophobicity of the hydrophobic
cellulose material. Such modification to lignin could be done in
solution or after the lignin is deposited onto cellulose.
[0032] Variations provide a process for producing a
cellulose-containing product, the process comprising providing a
lignin-coated cellulose material or a hydrophobic cellulose
material, and then incorporating at least a portion of the
lignin-coated cellulose material or the hydrophobic cellulose
material into a cellulose-containing product.
[0033] In some embodiments, the process comprises forming a
structural object that includes the cellulose material, or a
derivative thereof. In certain embodiments, the process comprises
forming a foam or aerogel that includes the cellulose material, or
a derivative thereof.
[0034] In some embodiments, the process comprises combining the
cellulose material, or a derivative thereof, with one or more other
materials to form a composite. The one or more other materials may
include a polymer selected from polyolefins, polyesters,
polyurethanes, polyamides, or combinations thereof. The one or more
other materials may include carbon.
[0035] In some embodiments, the process comprises forming a film
(such as a flexible film) comprising the cellulose material, or a
derivative thereof. In some embodiments, the process comprises
forming a coating or coating precursor comprising the cellulose
material, or a derivative thereof.
[0036] In some embodiments, the cellulose-containing product is
configured electrochemically for carrying or storing an electrical
current or voltage.
[0037] In some embodiments, the cellulose-containing product is
incorporated into a filter, membrane, or other separation
device.
[0038] In some embodiments, the cellulose-containing product is
incorporated as an additive into a coating, paint, or adhesive.
[0039] In some embodiments, the cellulose-containing product is
configured as a catalyst, catalyst substrate, or co-catalyst.
[0040] In some embodiments, the cellulose-containing product is
incorporated as a cement additive.
[0041] In some embodiments, the cellulose-containing product is a
paper coating.
[0042] In some embodiments, the cellulose-containing product is a
moisture-barrier pressed pulp product.
[0043] In some embodiments, the cellulose-containing product is
incorporated as a thickening agent or rheological modifier.
[0044] In some embodiments, the cellulose-containing product is
incorporated as an additive in a drilling fluid, such as an oil
recovery fluid and/or a gas recovery fluid.
[0045] A hydrophobic cellulose composition is disclosed with a
cellulose crystallinity of about 70% or greater, wherein the
hydrophobic cellulose composition contains cellulose particles
having a surface concentration of lignin that is greater than a
bulk concentration of lignin.
[0046] In some embodiments, the cellulose crystallinity is about
75% or greater, such as about 80% or 80% or greater.
[0047] In some embodiments, the hydrophobic cellulose composition
further comprises sulfur. The sulfur may be derived from the
process to produce the hydrophobic cellulose, or otherwise
incorporated into the composition.
[0048] In some embodiments, the hydrophobic cellulose composition
is characterized by an average cellulose degree of polymerization
from about 100 to about 1500, such as about 300 to about 700 or
about 150 to about 250. The composition may be characterized by a
cellulose degree of polymerization distribution having a single
peak or two peaks, for example.
[0049] In various embodiments, the cellulose-containing product is
selected from the group consisting of a structural object, a foam,
an aerogel, a polymer composite, a carbon composite, a film, a
coating, a coating precursor, a current or voltage carrier, a
filter, a membrane, a catalyst, a catalyst substrate, a coating
additive, a paint additive, an adhesive additive, a cement
additive, a paper coating, a moisture-barrier pressed pulp product,
a thickening agent, a rheological modifier, an additive for a
drilling fluid, and combinations or derivatives thereof.
BRIEF DESCRIPTION OF THE FIGURES
[0050] FIG. 1 depicts the production of lignin-coated cellulose
materials from biomass, according to some embodiments of the
invention. Mechanical treatment is optional.
[0051] FIG. 2 depicts the production of lignin-coated cellulose
materials from biomass, according to some embodiments of the
invention. Mechanical treatment and bleaching are both
optional.
[0052] FIG. 3 depicts the production of lignin-coated cellulose
materials from biomass, according to some embodiments of the
invention.
[0053] FIG. 4 depicts the production of lignin-coated cellulose
materials from biomass, according to some embodiments of the
invention. Mechanical treatment is optional.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0054] This description will enable one skilled in the art to make
and use the invention, and it describes several embodiments,
adaptations, variations, alternatives, and uses of the invention.
These and other embodiments, features, and advantages of the
present invention will become more apparent to those skilled in the
art when taken with reference to the following detailed description
of the invention in conjunction with any accompanying drawings.
[0055] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the context clearly indicates otherwise. Unless defined otherwise,
all technical and scientific terms used herein have the same
meaning as is commonly understood by one of ordinary skill in the
art to which this invention belongs. All composition numbers and
ranges based on percentages are weight percentages, unless
indicated otherwise. All ranges of numbers or conditions are meant
to encompass any specific value contained within the range, rounded
to any suitable decimal point.
[0056] Unless otherwise indicated, all numbers expressing
parameters, reaction conditions, concentrations of components, and
so forth used in the specification and claims are to be understood
as being modified in all instances by the term "about."
Accordingly, unless indicated to the contrary, the numerical
parameters set forth in the following specification and attached
claims are approximations that may vary depending at least upon a
specific analytical technique.
[0057] The term "comprising," which is synonymous with "including,"
"containing," or "characterized by" is inclusive or open-ended and
does not exclude additional, unrecited elements or method steps.
"Comprising" is a term of art used in claim language which means
that the named claim elements are essential, but other claim
elements may be added and still form a construct within the scope
of the claim.
[0058] As used herein, the phrase "consisting of" excludes any
element, step, or ingredient not specified in the claim. When the
phrase "consists of" (or variations thereof) appears in a clause of
the body of a claim, rather than immediately following the
preamble, it limits only the element set forth in that clause;
other elements are not excluded from the claim as a whole. As used
herein, the phrase "consisting essentially of" limits the scope of
a claim to the specified elements or method steps, plus those that
do not materially affect the basis and novel characteristic(s) of
the claimed subject matter.
[0059] With respect to the terms "comprising," "consisting of," and
"consisting essentially of," where one of these three terms is used
herein, the presently disclosed and claimed subject matter may
include the use of either of the other two terms. Thus in some
embodiments not otherwise explicitly recited, any instance of
"comprising" may be replaced by "consisting of" or, alternatively,
by "consisting essentially of."
[0060] Generally it is beneficial to process biomass in a way that
effectively separates the major fractions (cellulose,
hemicellulose, and lignin) from each other. Fractionation of
lignocellulosics leads to release of cellulosic fibers and opens
the cell wall structure by dissolution of lignin and hemicellulose
between the cellulose microfibrils. The fibers become more
accessible for conversion to fibrils or crystals. Hemicellulose
sugars can be fermented to a variety of products, such as ethanol,
or converted to other chemicals. Lignin from biomass has value as a
solid fuel and also as an energy feedstock to produce liquid fuels,
synthesis gas, or hydrogen; and as an intermediate to make a
variety of polymeric compounds. Additionally, minor components such
as proteins or rare sugars can be extracted and purified for
specialty applications.
[0061] This disclosure describes processes and apparatus to
efficiently fractionate any lignocellulosic-based biomass into its
primary major components (cellulose, lignin, and if present,
hemicellulose) so that each can be used in potentially distinct
processes. An advantage of the process is that it produces
cellulose-rich solids while concurrently producing a liquid phase
containing a high yield of both hemicellulose sugars and lignin,
and low quantities of lignin and hemicellulose degradation
products. The flexible fractionation technique enables multiple
uses for the products. The cellulose is an advantaged precursor for
producing lignin-coated cellulose, as will be described herein.
[0062] The present invention, in some variations, is premised on
the discovery that lignin-coated cellulose and related materials
can be produced under certain conditions including process
conditions and steps associated with the AVAP.RTM. process. It has
been found, surprisingly, that very high crystallinity can be
produced and maintained, without the need for an enzymatic or
separate acid treatment step to hydrolyze amorphous cellulose. High
crystallinity can translate to mechanically strong fibers or good
physical reinforcing properties, which are advantageous for
composites, reinforced polymers, and high-strength spun fibers and
textiles, for example.
[0063] Using sulfur dioxide (SO.sub.2) and ethanol (or other
solvent), the pretreatment disclosed herein effectively removes not
only hemicelluloses and lignin from biomass but also the amorphous
regions of cellulose, giving a unique, highly crystalline cellulose
material that requires minimal mechanical energy for reduction of
fiber size. The low mechanical energy requirement results from the
fibrillated cellulose network formed during chemical pretreatment
upon removal of the amorphous regions of cellulose.
[0064] As intended herein, cellulose products may include a range
of cellulosic materials, including but not limited to market pulp,
dissolving pulp, particulated cellulose, fibrillated cellulose,
microfibrillated cellulose, nanofibrillated cellulose,
microcrystalline cellulose, and nanocrystalline cellulose.
[0065] "Nanofibrillated cellulose" or equivalently "cellulose
nanofibrils" means cellulose fibers or regions that contain
nanometer-sized particles or fibers, or both micron-sized and
nanometer-sized particles or fibers. "Nanocrystalline cellulose" or
equivalently "cellulose nanocrystals" means cellulose particles,
regions, or crystals that contain nanometer-sized domains, or both
micron-sized and nanometer-sized domains. "Micron-sized" includes
from 1 .mu.m to 100 .mu.m and "nanometer-sized" includes from 0.01
nm to 1000 nm (1 .mu.m). Larger domains (including long fibers) may
also be present in these materials.
[0066] As used herein, "lignin-coated cellulose" means cellulose
particles or fibers which contain lignin on or near the surface of
the particles or fibers. Lignin may also be present in the bulk
(internal) portion of the cellulose particles or fibers, but the
concentration of lignin at the surface is higher than the
concentration of lignin in the internal portion. Lignin-coated
cellulose may be produced according to the processes disclosed
herein, comprising depositing lignin that has been first
solubilized by delignification and then undergoes precipitation
onto the cellulose. There may be some chemical changes that take
place upon lignin precipitation (e.g., condensation chemistry) to
alter hydrophobicity, molecular weight, sulfur content, oxygen
content, --OH group content, and so on. The surface coating is not
necessarily continuous or uniform in chemical composition,
hydrophobicity, or thickness.
[0067] Certain exemplary embodiments of the invention will now be
described. These embodiments are not intended to limit the scope of
the invention as claimed. The order of steps may be varied, some
steps may be omitted, and/or other steps may be added. Reference
herein to first step, second step, etc. is for purposes of
illustrating some embodiments only.
[0068] In some variations, the present invention provides a process
for producing a lignin-coated cellulose material, the process
comprising: [0069] (a) providing a lignocellulosic biomass
feedstock; [0070] (b) fractionating the feedstock in the presence
of an acid, a solvent for lignin, and water, to generate
cellulose-rich solids and a liquid containing hemicellulose and
lignin; [0071] (c) depositing at least some of the lignin, from the
liquid, onto a surface of the cellulose-rich solids to generate a
lignin-coated cellulose material; [0072] (d) optionally
mechanically treating the lignin-coated cellulose material; and
[0073] (e) recovering the lignin-coated cellulose material, wherein
the lignin-coated cellulose material is at least partially
hydrophobic.
[0074] In some embodiments, the acid is selected from the group
consisting of sulfur dioxide, sulfurous acid, sulfur trioxide,
sulfuric acid, lignosulfonic acid, and combinations thereof. In
certain embodiments, the acid is sulfur dioxide. In step (b),
exemplary conditions include SO.sub.2 concentration from about 12
wt % to about 30 wt %, fractionation temperature from about
140.degree. C. to about 170.degree. C., and fractionation time is
from about 1 hour to about 2 hours.
[0075] Step (c) is performed either in the same unit as step (b),
such as a digestor, or in another unit. Step (c) may occur
sequentially following step (b), or simultaneously with step (b),
or some combination thereof. Conditions may be selected or
optimized to promote deposition of lignin onto the cellulose. For
example, longer time, higher temperature, lower pH, and/or lower
concentration of the solvent for lignin may be utilized to cause or
promote lignin deposition during step (c). In some embodiments,
conditions of step (c) are different than those of step (b), and
physically separate units are employed (or employed in one unit in
a batch-wise process). In other embodiments, a single set of
conditions for steps (b) and (c) are selected, and steps (b) and
(c) are combined into a single reactor.
[0076] Conditions to promote deposition of lignin onto the
cellulose may be selected according to the Examples and other
disclosure in U.S. Patent App. No. 61/941,215, which is commonly
assigned and which has been filed of even date herewith (Feb. 18,
2014). U.S. Patent App. No. 61/941,215 is hereby incorporated by
reference herein in its entirety.
[0077] When step (d) is performed, steps (c) and (d) may be
integrated so that some lignin is physically deposited onto
cellulose during mechanical treatment. In some embodiments, the
lignin-coated cellulose material is treated with a total mechanical
energy of less than about 1000 kilowatt-hours per ton of the
lignin-coated cellulose material, such as less than about 500
kilowatt-hours per ton of the lignin-coated cellulose material. In
certain embodiments, the total mechanical energy is from about 100
kilowatt-hours to about 400 kilowatt-hours per ton of the
lignin-coated cellulose material.
[0078] The process may further include treatment of the
lignin-coated cellulose material with one or more enzymes or with
one or more acids. Such acids may be selected from the group
consisting of sulfur dioxide, sulfurous acid, lignosulfonic acid,
acetic acid, formic acid, and combinations thereof. Alternatively
or additionally, the process may further include treatment of the
lignin-coated cellulose material with heat.
[0079] In some embodiments, the crystallinity of the lignin-coated
cellulose material is at least 70%, such as at least 80% or
85%.
[0080] The lignin-coated cellulose material may include or consist
essentially of lignin-coated dissolving pulp, lignin-coated
fibrillated cellulose, lignin-coated microcrystalline cellulose,
lignin-coated nanocellulose, or other forms of lignin-coated
pulp.
[0081] The lignin-coated cellulose material may be characterized by
an average degree of polymerization from about 100 to about 1500,
such as from about 300 to about 700 or from about 150 to about
250.
[0082] Optionally, the process further comprises hydrolyzing
amorphous cellulose, contained in the lignocellulosic biomass
feedstock, into glucose, and optionally fermenting the glucose to a
fermentation product. Also optionally, the process further
comprises recovering, fermenting, or further treating
hemicellulosic sugars derived from the hemicellulose.
[0083] In certain embodiments, the process comprises fermenting the
hemicellulosic sugars to produce a monomer or precursor thereof;
polymerizing the monomer to produce a polymer; and combining the
polymer and the lignin-coated cellulose material to form a
polymer-cellulose composite.
[0084] In some embodiments, the process further comprises
recovering, combusting, or further treating the lignin that does
not deposit onto the cellulose-rich solids during step (c). The
process may further comprise chemically converting the
lignin-coated cellulose material to one or more lignin-coated
cellulose derivatives such as cellulose esters, cellulose ethers,
cellulose ether esters, alkylated cellulose compounds, cross-linked
cellulose compounds, acid-functionalized cellulose compounds,
base-functionalized cellulose compounds, or combinations
thereof.
[0085] The biomass feedstock may be selected from hardwoods,
softwoods, forest residues, eucalyptus, industrial wastes, pulp and
paper wastes, consumer wastes, or combinations thereof. Some
embodiments utilize agricultural residues, which include
lignocellulosic biomass associated with food crops, annual grasses,
energy crops, or other annually renewable feedstocks. Exemplary
agricultural residues include, but are not limited to, corn stover,
corn fiber, wheat straw, sugarcane bagasse, sugarcane straw, rice
straw, oat straw, barley straw, miscanthus, energy cane
straw/residue, or combinations thereof. The process disclosed
herein benefits from feedstock flexibility; it is effective for a
wide variety of cellulose-containing feedstocks.
[0086] As used herein, "lignocellulosic biomass" means any material
containing cellulose and lignin. Lignocellulosic biomass may also
contain hemicellulose. Mixtures of one or more types of biomass can
be used. In some embodiments, the biomass feedstock comprises both
a lignocellulosic component (such as one described above) in
addition to a sucrose-containing component (e.g., sugarcane or
energy cane) and/or a starch component (e.g., corn, wheat, rice,
etc.). Various moisture levels may be associated with the starting
biomass. The biomass feedstock need not be, but may be, relatively
dry. In general, the biomass is in the form of a particulate or
chip, but particle size is not critical in this invention.
[0087] Some variations provide a process for producing a
hydrophobic cellulose material, the process comprising: [0088] (a)
providing a lignocellulosic biomass feedstock; [0089] (b)
fractionating the feedstock in the presence of an acid, a solvent
for lignin, and water, to generate cellulose-rich solids and a
liquid containing hemicellulose and lignin, wherein a portion of
the lignin deposits onto a surface of the cellulose-rich solids,
thereby rendering the cellulose-rich solids at least partially
hydrophobic; [0090] (c) optionally mechanically treating the
cellulose-rich solids to form cellulose fibrils and/or cellulose
crystals, having a crystallinity of at least 60%; and [0091] (d)
recovering the hydrophobic cellulose material.
[0092] In some embodiments, the acid is selected from the group
consisting of sulfur dioxide, sulfurous acid, sulfur trioxide,
sulfuric acid, lignosulfonic acid, and combinations thereof.
[0093] The crystallinity of the hydrophobic cellulose material may
at least 70% or at least 80%. The hydrophobic cellulose material
may be characterized by an average degree of polymerization from
about 100 to about 1500, such as about 300 to about 700 or about
150 to about 250.
[0094] Optionally, the process further comprises chemically
modifying the lignin to increase hydrophobicity of the hydrophobic
cellulose material. Such modification to lignin could be done in
solution or after the lignin is deposited onto cellulose.
[0095] Variations provide a process for producing a
cellulose-containing product, the process comprising providing a
lignin-coated cellulose material or a hydrophobic cellulose
material, and then incorporating at least a portion of the
lignin-coated cellulose material or the hydrophobic cellulose
material into a cellulose-containing product.
[0096] In some embodiments, the process comprises forming a
structural object that includes the cellulose material, or a
derivative thereof. In certain embodiments, the process comprises
forming a foam or aerogel that includes the cellulose material, or
a derivative thereof.
[0097] In some embodiments, the process comprises combining the
cellulose material, or a derivative thereof, with one or more other
materials to form a composite. The one or more other materials may
include a polymer selected from polyolefins, polyesters,
polyurethanes, polyamides, or combinations thereof. The one or more
other materials may include carbon.
[0098] In some embodiments, the process comprises forming a film
(such as a flexible film) comprising the cellulose material, or a
derivative thereof. In some embodiments, the process comprises
forming a coating or coating precursor comprising the cellulose
material, or a derivative thereof.
[0099] In some embodiments, the cellulose-containing product is
configured electrochemically for carrying or storing an electrical
current or voltage.
[0100] In some embodiments, the cellulose-containing product is
incorporated into a filter, membrane, or other separation
device.
[0101] In some embodiments, the cellulose-containing product is
incorporated as an additive into a coating, paint, or adhesive.
[0102] In some embodiments, the cellulose-containing product is
configured as a catalyst, catalyst substrate, or co-catalyst.
[0103] In some embodiments, the cellulose-containing product is
incorporated as a cement additive.
[0104] In some embodiments, the cellulose-containing product is a
paper coating.
[0105] In some embodiments, the cellulose-containing product is
incorporated as a thickening agent or rheological modifier.
[0106] In some embodiments, the cellulose-containing product is
incorporated as an additive in a drilling fluid, such as an oil
recovery fluid and/or a gas recovery fluid.
[0107] A hydrophobic cellulose composition is disclosed with a
cellulose crystallinity of about 70% or greater, wherein the
hydrophobic cellulose composition contains cellulose particles
having a surface concentration of lignin that is greater than a
bulk concentration of lignin.
[0108] In some embodiments, the cellulose crystallinity is about
75% or greater, such as about 80% or 80% or greater.
[0109] In some embodiments, the hydrophobic cellulose composition
further comprises sulfur. The sulfur may be derived from the
process to produce the hydrophobic cellulose, or otherwise
incorporated into the composition.
[0110] In some embodiments, the hydrophobic cellulose composition
is characterized by an average cellulose degree of polymerization
from about 100 to about 1500, such as about 300 to about 700 or
about 150 to about 250. The composition may be characterized by a
cellulose degree of polymerization distribution having a single
peak or two peaks, for example.
[0111] In various embodiments, the cellulose-containing product is
selected from the group consisting of a structural object, a foam,
an aerogel, a polymer composite, a carbon composite, a film, a
coating, a coating precursor, a current or voltage carrier, a
filter, a membrane, a catalyst, a catalyst substrate, a coating
additive, a paint additive, an adhesive additive, a cement
additive, a paper coating, a thickening agent, a rheological
modifier, an additive for a drilling fluid, and combinations or
derivatives thereof.
[0112] In some embodiments, the cellulose-rich solids are treated
with a total mechanical energy of less than about 1000
kilowatt-hours per ton of the cellulose-rich solids, such as less
than about 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450,
400, 350, 300, or 250 kilowatt-hours per ton of the cellulose-rich
solids. In certain embodiments, the total mechanical energy is from
about 100 kilowatt-hours to about 400 kilowatt-hours per ton of the
cellulose-rich solids. Energy consumption may be measured in any
other suitable units. An ammeter measuring current drawn by a motor
driving the mechanical treatment device is one way to obtain an
estimate of the total mechanical energy.
[0113] Mechanically treating (when conducted) may employ one or
more known techniques such as, but by no means limited to, milling,
grinding, beating, sonicating, or any other means to form or
release fibrils and/or crystals in the cellulose. Essentially, any
type of mill or device that physically separates fibers may be
utilized. Such mills are well-known in the industry and include,
without limitation, Valley beaters, single disk refiners, double
disk refiners, conical refiners, including both wide angle and
narrow angle, cylindrical refiners, homogenizers, microfluidizers,
and other similar milling or grinding apparatus. See, for example,
Smook, Handbook for Pulp & Paper Technologists, Tappi Press,
1992.
[0114] The extent of mechanical treatment may be monitored during
the process by any of several means. Certain optical instruments
can provide continuous data relating to the fiber length
distributions and % fines, either of which may be used to define
endpoints for the mechanical treatment step. The time, temperature,
and pressure may vary during mechanical treatment. For example, in
some embodiments, sonication for a time from about 5 minutes to 2
hours, at ambient temperature and pressure, may be utilized.
[0115] Following mechanical treatment, the cellulose material may
be classified by particle size. A portion of material may be
subjected to a separate process, such as enzymatic hydrolysis to
produce glucose. Such material may have good crystallinity, for
example, but may not have desirable particle size or degree of
polymerization.
[0116] Some embodiments may further comprise treatment of the
cellulose-rich solids with one or more enzymes or with one or more
acids. When acids are employed, they may be selected from the group
consisting of sulfur dioxide, sulfurous acid, lignosulfonic acid,
acetic acid, formic acid, and combinations thereof. Acids
associated with hemicellulose, such as acetic acid or uronic acids,
may be employed, alone or in conjunction with other acids. Also,
the process may include treatment of the cellulose-rich solids with
heat.
[0117] When an acid is employed, the acid may be a strong acid such
as sulfuric acid, nitric acid, or phosphoric acid, for example.
Weaker acids may be employed, under more severe temperature and/or
time. Enzymes that hydrolyze cellulose (i.e., cellulases) and
possibly hemicellulose (i.e., with hemicellulase activity) may be
employed in step (c), either instead of acids, or potentially in a
sequential configuration before or after acidic hydrolysis.
[0118] In some embodiments, the process comprises enzymatically
treating the cellulose-rich solids to hydrolyze amorphous
cellulose. In other embodiments, or sequentially prior to or after
enzymatic treatment, the process may comprise acid-treating the
cellulose-rich solids to hydrolyze amorphous cellulose.
[0119] In some embodiments, the process further comprises
enzymatically treating the crystalline cellulose. In other
embodiments, or sequentially prior to or after enzymatic treatment,
the process further comprises acid-treating treating the
crystalline cellulose.
[0120] If desired, an enzymatic treatment may be employed prior to,
or possibly simultaneously with, mechanical treatment. However, in
preferred embodiments, no enzyme treatment is necessary to
hydrolyze amorphous cellulose or weaken the structure of the fiber
walls before isolation of fibers.
[0121] In some embodiments, the crystallinity of the cellulose-rich
solids is at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%,
69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%,
82%, 83%, 84%, 85%, 86% or higher. In these or other embodiments,
the crystallinity of the cellulose material is at least 60%, 61%,
62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%,
75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86% or
higher. The crystallinity may be measured using any known
techniques. For example, X-ray diffraction and solid-state .sup.13C
nuclear magnetic resonance may be utilized.
[0122] In some embodiments, the cellulose material is characterized
by an average degree of polymerization from about 100 to about
1500, such as about 125, 150, 175, 200, 225, 250, 300, 400, 500,
600, 700, 800, 900, 1000, 1100, 1200, 1300, or 1400. For example,
the cellulose material may be characterized by an average degree of
polymerization from about 300 to about 700, or from about 150 to
about 250. The cellulose material, when in the form of crystals,
may have a degree of polymerization less than 100, such as about
75, 50, 25, or 10. Portions of the material may have a degree of
polymerization that is higher than 1500, such as about 2000, 3000,
4000, or 5000.
[0123] In some embodiments, the cellulose material is characterized
by a degree of polymerization distribution having a single peak. In
other embodiments, the cellulose material is characterized by a
degree of polymerization distribution having two peaks, such as one
centered in the range of 150-250 and another peak centered in the
range of 300-700.
[0124] In some embodiments, the cellulose material is characterized
by an average length-to-width aspect ratio of particles from about
10 to about 1000, such as about 15, 20, 25, 35, 50, 75, 100, 150,
200, 250, 300, 400, or 500. Fibrils are generally associated with
higher aspect ratios than crystals. Nanocrystals, for example, may
have a length range of about 100 nm to 500 nm and a diameter of
about 4 nm, translating to an aspect ratio of 25 to 125.
Nanofibrils may have a length of about 2000 nm and diameter range
of 5 to 50 nm, translating to an aspect ratio of 40 to 400. In some
embodiments, the aspect ratio is less than 50, less than 45, less
than 40, less than 35, less than 30, less than 25, less than 20,
less than 15, or less than 10.
[0125] Optionally, the process further comprises hydrolyzing
amorphous cellulose into glucose in, and fermenting the glucose to
a fermentation product. Optionally, the process further comprises
recovering, fermenting, or further treating hemicellulosic sugars
derived from the hemicellulose. Optionally, the process further
comprises recovering, combusting, or further treating the lignin
(i.e., the lignin that did not deposit onto the cellulose).
[0126] Glucose that is generated from hydrolysis of amorphous
cellulose may be integrated into an overall process to produce
ethanol, or another fermentation co-product. Thus in some
embodiments, the process further comprises hydrolyzing amorphous
cellulose into glucose, and recovering the glucose. The glucose may
be purified and sold. Or the glucose may be fermented to a
fermentation product, such as but not limited to ethanol. The
glucose or a fermentation product may be recycled to the front end,
such as to hemicellulose sugar processing, if desired.
[0127] When hemicellulosic sugars are recovered and fermented, they
may be fermented to produce a monomer or precursor thereof. The
monomer may be polymerized to produce a polymer, which may then be
combined with the cellulose material to form a polymer-cellulose
composite.
[0128] In some embodiments, the process further comprises
chemically converting the cellulose material to one or more
cellulose derivatives. For example, cellulose derivatives may be
selected from the group consisting of esters, ethers, ether esters,
alkylated compounds, cross-linked compounds, acid-functionalized
compounds, base-functionalized compounds, and combinations
thereof.
[0129] Various types of cellulose functionalization or
derivatization may be employed, such as functionalization using
polymers, chemical surface modification, functionalization using
nanoparticles, modification with inorganics or surfactants, or
biochemical modification.
[0130] In some embodiments, the SO.sub.2 concentration is from
about 12 wt % to about 30 wt %. In some embodiments, the
fractionation temperature is from about 140.degree. C. to about
170.degree. C. In some embodiments, the fractionation time is from
about 1 hour to about 2 hours. The process is controlled such that
a portion of the solubilized lignin (or another source of lignin)
intentionally deposits back onto a surface of the cellulose-rich
solids, thereby rendering the cellulose-rich solids at least
partially hydrophobic.
[0131] A significant factor limiting the application of
strength-enhancing, lightweight cellulose in composites is
cellulose's inherent hydrophilicity. Surface modification of the
cellulose surface to impart hydrophobicity to enable uniform
dispersion in a hydrophobic polymer matrix is an active area of
study. It has been discovered that when preparing cellulose using
the processes described herein, lignin may condense on pulp under
certain conditions, giving a rise in Kappa number and production of
a brown or black material. The lignin increases the hydrophobicity
of the cellulose precursor material, and that hydrophobicity is
retained provided that there is not removal of the lignin through
bleaching or other steps. (Some bleaching may still be performed,
either to adjust lignin content or to attack a certain type of
lignin, for example.)
[0132] Process conditions may be varied to accomplish the desire
degree of lignin deposition. Conditions which tend to promote
lignin deposition onto fibers are extended time and/or temperature,
reduced pH, and reduced concentration of solvent for lignin (e.g.,
about 40 wt %, 35 wt %, 30 wt %, 25 wt %, 20 wt %, or less
ethanol). Alternatively, or additionally, the process may include
one or more washing steps that are adapted to deposit at least some
of the lignin that was solubilized during the initial
fractionation. One approach is to wash with water rather than a
solution of water and solvent. Because lignin is generally not
soluble in water, it will begin to precipitate. Optionally, other
conditions may be varied, such as pH and temperature, during
fractionation, washing, or other steps, to optimize the amount of
lignin deposited on surfaces. It is noted that in order for the
lignin surface concentration to be higher than the bulk
concentration, the lignin needs to be first pulled into solution
and then redeposited; internal lignin (within particles of
cellulose) does not enhance hydrophobicity in the same way.
[0133] Optionally, the process for producing a hydrophobic
cellulose material may further include chemically modifying the
lignin to increase hydrophobicity of the cellulose material. The
chemical modification of lignin may be conducted during
fractionation, during deposition, following deposition, or some
combination thereof.
[0134] High loading rates of lignin have been achieved in
thermoplastics. Even higher loading levels are obtained with
well-known modifications of lignin. The preparation of useful
polymeric materials containing a substantial amount of lignin has
been the subject of investigations for more than thirty years.
Typically, lignin may be blended into polyolefins or polyesters by
extrusion up to 25-40 wt % while satisfying mechanical
characteristics. In order to increase the compatibility between
lignin and other hydrophobic polymers, different approaches have
been used. For example, chemical modification of lignin may be
accomplished through esterification with long-chain fatty
acids.
[0135] Any known chemical modifications may be carried out on the
lignin, to further increase the hydrophobic nature of the
lignin-coated cellulose material provided by embodiments of this
invention.
[0136] The cellulose material may further contain some sulfonated
lignin that is derived from sulfonation reactions with SO.sub.2
(when used as the acid in fractionation) during the biomass
digestion. The amount of sulfonated lignin may be about 0.1 wt %
(or less), 0.2 wt %, 0.5 wt %, 0.8 wt %, 1 wt %, or more. Also,
without being limited by any theory, it is speculated that a small
amount of sulfur may chemically react with cellulose itself, in
some embodiments.
[0137] A cellulose-containing product may include any of the
disclosed hydrophobic, lignin-coated cellulose compositions. Many
cellulose-containing products are possible. For example, a
cellulose-containing product may be selected from the group
consisting of a structural object, a foam, an aerogel, a polymer
composite, a carbon composite, a film, a coating, a coating
precursor, a current or voltage carrier, a filter, a membrane, a
catalyst, a catalyst substrate, a coating additive, a paint
additive, an adhesive additive, a cement additive, a paper coating,
a thickening agent, a rheological modifier, an additive for a
drilling fluid, and combinations or derivatives thereof.
[0138] In some embodiments, the cellulose-containing product is a
moisture-barrier pressed pulp product. In numerous applications
including packaging, moisture may be present. In a moisture content
situation, a moisture barrier is desirable to prevent, or at least
slow, the leakage of any moisture. Currently, a pulp product may be
treated to produce an end product having a moisture barrier.
Conventional methods of creating moisture barrier products include
coating linerboard with a polymeric water-repellant laminate, or
coating linerboard with wax or a wax-like substance. However, each
of these methods adds significant production costs to the
fabrication process. Beyond production costs, these processes
produce a resultant moisture barrier product that is not completely
repulpable and, in fact, is often rejected by recycling plants only
to end up in a landfill. Moreover, the resultant moisture barrier
product has a surface coating that can affect production. For
instance, the surface coating is often difficult to print on
thereby requiring a special ink. The surface coating may also
create problems in gluing portions of the corrugated to form a
container, the glue not adhering well to the surface coating. The
surface coating is easily scratched reducing the effectiveness of
the moisture barrier protection.
[0139] In some embodiments of the invention, a moisture-barrier
pulp product is provided by lignin-coated, hydrophobic material.
The moisture-barrier pulp product may be incorporated into a
variety of final products and geometries, including coatings,
structural objects (e.g., containers), and so on. In some
embodiments, the moisture-barrier pulp product is a
moisture-barrier pressed pulp product. In some embodiments, the
moisture-barrier pulp product is a moisture-barrier molded pulp
product. In some embodiments, the moisture-barrier pulp product is
a moisture-barrier extruded pulp product.
[0140] Some process variations may be understood with reference to
FIGS. 1-4. Dotted lines denote optional streams. Various
embodiments will now be further described, without limitation as to
the scope of the invention. These embodiments are exemplary in
nature.
[0141] In some embodiments, a first process step is "cooking"
(equivalently, "digesting") which fractionates the three
lignocellulosic material components (cellulose, hemicellulose, and
lignin) to allow easy downstream removal. Specifically,
hemicelluloses are dissolved and over 50% are completely
hydrolyzed; cellulose is separated but remains resistant to
hydrolysis; and part of the lignin is sulfonated into water-soluble
lignosulfonates.
[0142] The lignocellulosic material is processed in a solution
(cooking liquor) of aliphatic alcohol, water, and sulfur dioxide.
The cooking liquor preferably contains at least 10 wt %, such as at
least 20 wt %, 30 wt %, 40 wt %, or 50 wt % of a solvent for
lignin. For example, the cooking liquor may contain about 30-70 wt
% solvent, such as about 50 wt % solvent. The solvent for lignin
may be an aliphatic alcohol, such as methanol, ethanol, 1-propanol,
2-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol,
1-hexanol, or cyclohexanol. The solvent for lignin may be an
aromatic alcohol, such as phenol or cresol. Other lignin solvents
are possible, such as (but not limited to) glycerol, methyl ethyl
ketone, or diethyl ether. Combinations of more than one solvent may
be employed.
[0143] Preferably, enough solvent is included in the extractant
mixture to dissolve the lignin present in the starting material.
The solvent for lignin may be completely miscible, partially
miscible, or immiscible with water, so that there may be more than
one liquid phase. Potential process advantages arise when the
solvent is miscible with water, and also when the solvent is
immiscible with water. When the solvent is water-miscible, a single
liquid phase forms, so mass transfer of lignin and hemicellulose
extraction is enhanced, and the downstream process must only deal
with one liquid stream. When the solvent is immiscible in water,
the extractant mixture readily separates to form liquid phases, so
a distinct separation step can be avoided or simplified. This can
be advantageous if one liquid phase contains most of the lignin and
the other contains most of the hemicellulose sugars, as this
facilitates recovering the lignin from the hemicellulose
sugars.
[0144] The cooking liquor preferably contains sulfur dioxide and/or
sulfurous acid (H.sub.2SO.sub.3). The cooking liquor preferably
contains SO.sub.2, in dissolved or reacted form, in a concentration
of at least 3 wt %, preferably at least 6 wt %, more preferably at
least 8 wt %, such as about 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13
wt %, 14 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt % or higher. The
cooking liquor may also contain one or more species, separately
from SO.sub.2, to adjust the pH. The pH of the cooking liquor is
typically about 4 or less.
[0145] Sulfur dioxide is a preferred acid catalyst, because it can
be recovered easily from solution after hydrolysis. The majority of
the SO.sub.2 from the hydrolysate may be stripped and recycled back
to the reactor. Recovery and recycling translates to less lime
required compared to neutralization of comparable sulfuric acid,
less solids to dispose of, and less separation equipment. The
increased efficiency owing to the inherent properties of sulfur
dioxide mean that less total acid or other catalysts may be
required. This has cost advantages, since sulfuric acid can be
expensive. Additionally, and quite significantly, less acid usage
also will translate into lower costs for a base (e.g., lime) to
increase the pH following hydrolysis, for downstream operations.
Furthermore, less acid and less base will also mean substantially
less generation of waste salts (e.g., gypsum) that may otherwise
require disposal.
[0146] In some embodiments, an additive may be included in amounts
of about 0.1 wt % to 10 wt % or more to increase cellulose
viscosity. Exemplary additives include ammonia, ammonia hydroxide,
urea, anthraquinone, magnesium oxide, magnesium hydroxide, sodium
hydroxide, and their derivatives.
[0147] The cooking is performed in one or more stages using batch
or continuous digestors. Solid and liquid may flow cocurrently or
countercurrently, or in any other flow pattern that achieves the
desired fractionation. The cooking reactor may be internally
agitated, if desired.
[0148] Depending on the lignocellulosic material to be processed,
the cooking conditions are varied, with temperatures from about
65.degree. C. to 190.degree. C., for example 75.degree. C.,
85.degree. C., 95.degree. C., 105.degree. C., 115.degree. C.,
125.degree. C., 130.degree. C., 135.degree. C., 140.degree. C.,
145.degree. C., 150.degree. C., 155.degree. C., 165.degree. C. or
170.degree. C., and corresponding pressures from about 1 atmosphere
to about 15 atmospheres in the liquid or vapor phase. The cooking
time of one or more stages may be selected from about 15 minutes to
about 720 minutes, such as about 30, 45, 60, 90, 120, 140, 160,
180, 250, 300, 360, 450, 550, 600, or 700 minutes. Generally, there
is an inverse relationship between the temperature used during the
digestion step and the time needed to obtain good fractionation of
the biomass into its constituent parts.
[0149] The cooking liquor to lignocellulosic material ratio may be
selected from about 1 to about 10, such as about 2, 3, 4, 5, or 6.
In some embodiments, biomass is digested in a pressurized vessel
with low liquor volume (low ratio of cooking liquor to
lignocellulosic material), so that the cooking space is filled with
ethanol and sulfur dioxide vapor in equilibrium with moisture. The
cooked biomass is washed in alcohol-rich solution to recover lignin
and dissolved hemicelluloses, while the remaining pulp is further
processed. In some embodiments, the process of fractionating
lignocellulosic material comprises vapor-phase cooking of
lignocellulosic material with aliphatic alcohol (or other solvent
for lignin), water, and sulfur dioxide. See, for example, U.S. Pat.
Nos. 8,038,842 and 8,268,125 which are incorporated by reference
herein.
[0150] A portion or all of the sulfur dioxide may be present as
sulfurous acid in the extract liquor. In certain embodiments,
sulfur dioxide is generated in situ by introducing sulfurous acid,
sulfite ions, bisulfite ions, combinations thereof, or a salt of
any of the foregoing. Excess sulfur dioxide, following hydrolysis,
may be recovered and reused. In some embodiments, sulfur dioxide is
saturated in water (or aqueous solution, optionally with an
alcohol) at a first temperature, and the hydrolysis is then carried
out at a second, generally higher, temperature. In some
embodiments, sulfur dioxide is sub-saturated. In some embodiments,
sulfur dioxide is super-saturated. In some embodiments, sulfur
dioxide concentration is selected to achieve a certain degree of
lignin sulfonation, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or
10% sulfur content. SO.sub.2 reacts chemically with lignin to form
stable lignosulfonic acids which may be present both in the solid
and liquid phases.
[0151] The concentration of sulfur dioxide, additives, and
aliphatic alcohol (or other solvent) in the solution and the time
of cook may be varied to control the yield of cellulose and
hemicellulose in the pulp. The concentration of sulfur dioxide and
the time of cook may be varied to control the yield of lignin
versus lignosulfonates in the hydrolysate. In some embodiments, the
concentration of sulfur dioxide, temperature, and the time of cook
may be varied to control the yield of fermentable sugars.
[0152] Once the desired amount of fractionation of both
hemicellulose and lignin from the solid phase is achieved, the
liquid and solid phases are separated. Conditions for the
separation may be selected to minimize or enhance the
reprecipitation of the extracted lignin on the solid phase.
Minimizing lignin reprecipitation is favored by conducting
separation or washing at a temperature of at least the
glass-transition temperature of lignin (about 120.degree. C.);
conversely, enhancing lignin reprecipitation is favored by
conducting separation or washing at a temperature less than the
glass-transition temperature of lignin.
[0153] The physical separation can be accomplished either by
transferring the entire mixture to a device that can carry out the
separation and washing, or by removing only one of the phases from
the reactor while keeping the other phase in place. The solid phase
can be physically retained by appropriately sized screens through
which liquid can pass. The solid is retained on the screens and can
be kept there for successive solid-wash cycles. Alternately, the
liquid may be retained and solid phase forced out of the reaction
zone, with centrifugal or other forces that can effectively
transfer the solids out of the slurry. In a continuous system,
countercurrent flow of solids and liquid can accomplish the
physical separation.
[0154] The recovered solids normally will contain a quantity of
lignin and sugars, some of which can be removed easily by washing.
The washing-liquid composition can be the same as or different than
the liquor composition used during fractionation. Multiple washes
may be performed to increase effectiveness. Preferably, one or more
washes are performed with a composition including a solvent for
lignin, to remove additional lignin from the solids, followed by
one or more washes with water to displace residual solvent and
sugars from the solids. Recycle streams, such as from
solvent-recovery operations, may be used to wash the solids.
[0155] After separation and washing as described, a solid phase and
at least one liquid phase are obtained. The solid phase contains
substantially undigested cellulose. A single liquid phase is
usually obtained when the solvent and the water are miscible in the
relative proportions that are present. In that case, the liquid
phase contains, in dissolved form, most of the lignin originally in
the starting lignocellulosic material, as well as soluble monomeric
and oligomeric sugars formed in the hydrolysis of any hemicellulose
that may have been present. Multiple liquid phases tend to form
when the solvent and water are wholly or partially immiscible. The
lignin tends to be contained in the liquid phase that contains most
of the solvent. Hemicellulose hydrolysis products tend to be
present in the liquid phase that contains most of the water.
[0156] In some embodiments, hydrolysate from the cooking step is
subjected to pressure reduction. Pressure reduction may be done at
the end of a cook in a batch digestor, or in an external flash tank
after extraction from a continuous digestor, for example. The flash
vapor from the pressure reduction may be collected into a cooking
liquor make-up vessel. The flash vapor contains substantially all
the unreacted sulfur dioxide which may be directly dissolved into
new cooking liquor. The cellulose is then removed to be washed and
further treated as desired.
[0157] A process washing step recovers the hydrolysate from the
cellulose. The washed cellulose is pulp that may be used for
various purposes (e.g., paper or nanocellulose production). The
weak hydrolysate from the washer continues to the final reaction
step; in a continuous digestor this weak hydrolysate may be
combined with the extracted hydrolysate from the external flash
tank. In some embodiments, washing and/or separation of hydrolysate
and cellulose-rich solids is conducted at a temperature of at least
about 100.degree. C., 110.degree. C., or 120.degree. C. The washed
cellulose may also be used for glucose production via cellulose
hydrolysis with enzymes or acids.
[0158] In another reaction step, the hydrolysate may be further
treated in one or multiple steps to hydrolyze the oligomers into
monomers. This step may be conducted before, during, or after the
removal of solvent and sulfur dioxide. The solution may or may not
contain residual solvent (e.g. alcohol). In some embodiments,
sulfur dioxide is added or allowed to pass through to this step, to
assist hydrolysis. In these or other embodiments, an acid such as
sulfurous acid or sulfuric acid is introduced to assist with
hydrolysis. In some embodiments, the hydrolysate is autohydrolyzed
by heating under pressure. In some embodiments, no additional acid
is introduced, but lignosulfonic acids produced during the initial
cooking are effective to catalyze hydrolysis of hemicellulose
oligomers to monomers. In various embodiments, this step utilizes
sulfur dioxide, sulfurous acid, sulfuric acid at a concentration of
about 0.01 wt % to 30 wt %, such as about 0.05 wt %, 0.1 wt %, 0.2
wt %, 0.5 wt %, 1 wt %, 2 wt %, 5 wt %, 10 wt %, or 20 wt %. This
step may be carried out at a temperature from about 100.degree. C.
to 220.degree. C., such as about 110.degree. C., 120.degree. C.,
130.degree. C., 140.degree. C., 150.degree. C., 160.degree. C.,
170.degree. C., 180.degree. C., 190.degree. C., 200.degree. C., or
210.degree. C. Heating may be direct or indirect to reach the
selected temperature.
[0159] The reaction step produces fermentable sugars which can then
be concentrated by evaporation to a fermentation feedstock.
Concentration by evaporation may be accomplished before, during, or
after the treatment to hydrolyze oligomers. The final reaction step
may optionally be followed by steam stripping of the resulting
hydrolysate to remove and recover sulfur dioxide and alcohol, and
for removal of potential fermentation-inhibiting side products. The
evaporation process may be under vacuum or pressure, from about
-0.1 atmospheres to about 10 atmospheres, such as about 0.1 atm,
0.3 atm, 0.5 atm, 1.0 atm, 1.5 atm, 2 atm, 4 atm, 6 atm, or 8
atm.
[0160] Recovering and recycling the sulfur dioxide may utilize
separations such as, but not limited to, vapor-liquid disengagement
(e.g. flashing), steam stripping, extraction, or combinations or
multiple stages thereof. Various recycle ratios may be practiced,
such as about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or
more. In some embodiments, about 90-99% of initially charged
SO.sub.2 is readily recovered by distillation from the liquid
phase, with the remaining 1-10% (e.g., about 3-5%) of the SO.sub.2
primarily bound to dissolved lignin in the form of
lignosulfonates.
[0161] In a preferred embodiment, the evaporation step utilizes an
integrated alcohol stripper and evaporator. Evaporated vapor
streams may be segregated so as to have different concentrations of
organic compounds in different streams. Evaporator condensate
streams may be segregated so as to have different concentrations of
organic compounds in different streams. Alcohol may be recovered
from the evaporation process by condensing the exhaust vapor and
returning to the cooking liquor make-up vessel in the cooking step.
Clean condensate from the evaporation process may be used in the
washing step.
[0162] In some embodiments, an integrated alcohol stripper and
evaporator system is employed, wherein aliphatic alcohol is removed
by vapor stripping, the resulting stripper product stream is
concentrated by evaporating water from the stream, and evaporated
vapor is compressed using vapor compression and is reused to
provide thermal energy.
[0163] The hydrolysate from the evaporation and final reaction step
contains mainly fermentable sugars but may also contain lignin
depending on the location of lignin separation in the overall
process configuration. The hydrolysate may be concentrated to a
concentration of about 5 wt % to about 60 wt % solids, such as
about 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt %, 35 wt %, 40 wt
%, 45 wt %, 50 wt % or 55 wt % solids. The hydrolysate contains
fermentable sugars.
[0164] Fermentable sugars are defined as hydrolysis products of
cellulose, galactoglucomannan, glucomannan, arabinoglucuronoxylans,
arabinogalactan, and glucuronoxylans into their respective
short-chained oligomers and monomer products, i.e., glucose,
mannose, galactose, xylose, and arabinose. The fermentable sugars
may be recovered in purified form, as a sugar slurry or dry sugar
solids, for example. Any known technique may be employed to recover
a slurry of sugars or to dry the solution to produce dry sugar
solids.
[0165] In some embodiments, the fermentable sugars are fermented to
produce biochemicals or biofuels such as (but by no means limited
to) ethanol, isopropanol, acetone, 1-butanol, isobutanol, lactic
acid, succinic acid, or any other fermentation products. Some
amount of the fermentation product may be a microorganism or
enzymes, which may be recovered if desired.
[0166] When the fermentation will employ bacteria, such as
Clostridia bacteria, it is preferable to further process and
condition the hydrolysate to raise pH and remove residual SO.sub.2
and other fermentation inhibitors. The residual SO.sub.2 (i.e.,
following removal of most of it by stripping) may be catalytically
oxidized to convert residual sulfite ions to sulfate ions by
oxidation. This oxidation may be accomplished by adding an
oxidation catalyst, such as FeSO.sub.4.7H.sub.2O, that oxidizes
sulfite ions to sulfate ions. Preferably, the residual SO.sub.2 is
reduced to less than about 100 ppm, 50 ppm, 25 ppm, 10 ppm, 5 ppm,
or 1 ppm.
[0167] In some embodiments, the process further comprises
recovering the lignin as a co-product. The sulfonated lignin may
also be recovered as a co-product. In certain embodiments, the
process further comprises combusting or gasifying the sulfonated
lignin, recovering sulfur contained in the sulfonated lignin in a
gas stream comprising reclaimed sulfur dioxide, and then recycling
the reclaimed sulfur dioxide for reuse.
[0168] The process lignin separation step is for the separation of
lignin from the hydrolysate and can be located before or after the
final reaction step and evaporation. If located after, then lignin
will precipitate from the hydrolysate since alcohol has been
removed in the evaporation step. The remaining water-soluble
lignosulfonates may be precipitated by converting the hydrolysate
to an alkaline condition (pH higher than 7) using, for example, an
alkaline earth oxide, preferably calcium oxide (lime). The combined
lignin and lignosulfonate precipitate may be filtered. The lignin
and lignosulfonate filter cake may be dried as a co-product or
burned or gasified for energy production. The hydrolysate from
filtering may be recovered and sold as a concentrated sugar
solution product or further processed in a subsequent fermentation
or other reaction step.
[0169] Native (non-sulfonated) lignin is hydrophobic, while
lignosulfonates are hydrophilic. Hydrophilic lignosulfonates may
have less propensity to clump, agglomerate, and stick to surfaces.
Even lignosulfonates that do undergo some condensation and increase
of molecular weight, will still have an HSO.sub.3 group that will
contribute some solubility (hydrophilic).
[0170] In some embodiments, the soluble lignin precipitates from
the hydrolysate after solvent has been removed in the evaporation
step. In some embodiments, reactive lignosulfonates are selectively
precipitated from hydrolysate using excess lime (or other base,
such as ammonia) in the presence of aliphatic alcohol. In some
embodiments, hydrated lime is used to precipitate lignosulfonates.
In some embodiments, part of the lignin is precipitated in reactive
form and the remaining lignin is sulfonated in water-soluble
form.
[0171] The process fermentation and distillation steps are intended
for the production of fermentation products, such as alcohols or
organic acids. After removal of cooking chemicals and lignin, and
further treatment (oligomer hydrolysis), the hydrolysate contains
mainly fermentable sugars in water solution from which any
fermentation inhibitors have been preferably removed or
neutralized. The hydrolysate is fermented to produce dilute alcohol
or organic acids, from 1 wt % to 20 wt % concentration. The dilute
product is distilled or otherwise purified as is known in the
art.
[0172] When alcohol is produced, such as ethanol, some of it may be
used for cooking liquor makeup in the process cooking step. Also,
in some embodiments, a distillation column stream, such as the
bottoms, with or without evaporator condensate, may be reused to
wash cellulose. In some embodiments, lime may be used to dehydrate
product alcohol. Side products may be removed and recovered from
the hydrolysate. These side products may be isolated by processing
the vent from the final reaction step and/or the condensate from
the evaporation step. Side products include furfural, hydroxymethyl
furfural (HMF), methanol, acetic acid, and lignin-derived
compounds, for example.
[0173] The glucose may be fermented to an alcohol, an organic acid,
or another fermentation product. The glucose may be used as a
sweetener or isomerized to enrich its fructose content. The glucose
may be used to produce baker's yeast. The glucose may be
catalytically or thermally converted to various organic acids and
other materials.
[0174] When hemicellulose is present in the starting biomass, all
or a portion of the liquid phase contains hemicellulose sugars and
soluble oligomers. It is preferred to remove most of the lignin
from the liquid, as described above, to produce a fermentation
broth which will contain water, possibly some of the solvent for
lignin, hemicellulose sugars, and various minor components from the
digestion process. This fermentation broth can be used directly,
combined with one or more other fermentation streams, or further
treated. Further treatment can include sugar concentration by
evaporation; addition of glucose or other sugars (optionally as
obtained from cellulose saccharification); addition of various
nutrients such as salts, vitamins, or trace elements; pH
adjustment; and removal of fermentation inhibitors such as acetic
acid and phenolic compounds. The choice of conditioning steps
should be specific to the target product(s) and microorganism(s)
employed.
[0175] In some embodiments, hemicellulose sugars are not fermented
but rather are recovered and purified, stored, sold, or converted
to a specialty product. Xylose, for example, can be converted into
xylitol.
[0176] A lignin product can be readily obtained from a liquid phase
using one or more of several methods. One simple technique is to
evaporate off all liquid, resulting in a solid lignin-rich residue.
This technique would be especially advantageous if the solvent for
lignin is water-immiscible. Another method is to cause the lignin
to precipitate out of solution. Some of the ways to precipitate the
lignin include (1) removing the solvent for lignin from the liquid
phase, but not the water, such as by selectively evaporating the
solvent from the liquid phase until the lignin is no longer
soluble; (2) diluting the liquid phase with water until the lignin
is no longer soluble; and (3) adjusting the temperature and/or pH
of the liquid phase. Methods such as centrifugation can then be
utilized to capture the lignin. Yet another technique for removing
the lignin is continuous liquid-liquid extraction to selectively
remove the lignin from the liquid phase, followed by removal of the
extraction solvent to recover relatively pure lignin.
[0177] Lignin produced in accordance with the invention can be used
as a fuel. As a solid fuel, lignin is similar in energy content to
coal. Lignin can act as an oxygenated component in liquid fuels, to
enhance octane while meeting standards as a renewable fuel. The
lignin produced herein can also be used as polymeric material, and
as a chemical precursor for producing lignin derivatives. The
sulfonated lignin may be sold as a lignosulfonate product, or
burned for fuel value.
[0178] The present invention also provides systems configured for
carrying out the disclosed processes, and compositions produced
therefrom. Any stream generated by the disclosed processes may be
partially or completed recovered, purified or further treated,
and/or marketed or sold.
[0179] Certain cellulose-containing products provide high
transparency, good mechanical strength, and/or enhanced gas (e.g.,
O.sub.2 or CO.sub.2) barrier properties, for example. Certain
cellulose-containing products containing hydrophobic cellulose
materials provided herein may be useful as anti-wetting and
anti-icing coatings, for example.
[0180] Some embodiments provide cellulose-containing products with
applications for sensors, catalysts, antimicrobial materials,
current carrying and energy storage capabilities. Cellulose
crystals have the capacity to assist in the synthesis of metallic
and semiconducting nanoparticle chains.
[0181] Some embodiments provide composites containing cellulose and
a carbon-containing material, such as (but not limited to) lignin,
graphite, graphene, or carbon aerogels.
[0182] Cellulose may be coupled with the stabilizing properties of
surfactants and exploited for the fabrication of nanoarchitectures
of various semiconducting materials.
[0183] The reactive surface of --OH side groups in cellulose
facilitates grafting chemical species to achieve different surface
properties. Surface functionalization allows the tailoring of
particle surface chemistry to facilitate self-assembly, controlled
dispersion within a wide range of matrix polymers, and control of
both the particle-particle and particle-matrix bond strength.
Composites may be transparent, have tensile strengths greater than
cast iron, and have very low coefficient of thermal expansion.
Potential applications include, but are not limited to, barrier
films, antimicrobial films, transparent films, flexible displays,
reinforcing fillers for polymers, biomedical implants,
pharmaceuticals, drug delivery, fibers and textiles, templates for
electronic components, separation membranes, batteries,
supercapacitors, electroactive polymers, and many others.
[0184] Other cellulose applications suitable to the present
invention include reinforced polymers, high-strength spun fibers
and textiles, advanced composite materials, films for barrier and
other properties, additives for coatings, paints, lacquers and
adhesives, switchable optical devices, pharmaceuticals and drug
delivery systems, bone replacement and tooth repair, improved
paper, packaging and building products, additives for foods and
cosmetics, catalysts, and hydrogels.
[0185] Aerospace and transportation composites may benefit from
high crystallinity. Automotive applications include cellulose
composites with polypropylene, polyamide (e.g. Nylons), or
polyesters (e.g. PBT).
[0186] Cellulose materials provided herein are suitable as
strength-enhancing additives for renewable and biodegradable
composites. The cellulosic fibrillar structures may function as a
binder between two organic phases for improved fracture toughness
and prevention of crack formation for application in packaging,
construction materials, appliances, and renewable fibers.
[0187] Cellulose materials provided herein are suitable as
transparent and dimensional stable strength-enhancing additives and
substrates for application in flexible displays, flexible circuits,
printable electronics, and flexible solar panels. Cellulose is
incorporated into the substrate-sheets are formed by vacuum
filtration, dried under pressure and calandered, for example. In a
sheet structure, cellulose acts as a glue between the filler
aggregates. The formed calandered sheets are smooth and
flexible.
[0188] Cellulose materials provided herein are suitable for
composite and cement additives allowing for crack reduction and
increased toughness and strength. Foamed, cellular
cellulose-concrete hybrid materials allow for lightweight
structures with increased crack reduction and strength.
[0189] Strength enhancement with cellulose increases both the
binding area and binding strength for application in high strength,
high bulk, high filler content paper and board with enhanced
moisture and oxygen barrier properties.
[0190] Fibrillated cellulose nanopaper has a higher density and
higher tensile mechanical properties than conventional paper. It
can also be optically transparent and flexible, with low thermal
expansion and excellent oxygen barrier characteristics. The
functionality of the nanopaper can be further broadened by
incorporating other entities such as carbon nanotubes, nanoclay or
a conductive polymer coating.
[0191] Porous cellulose may be used for cellular bioplastics,
insulation and plastics and bioactive membranes and filters. Highly
porous cellulose materials are generally of high interest in the
manufacturing of filtration media as well as for biomedical
applications, e.g., in dialysis membranes.
[0192] Cellulose materials provided herein are suitable as coating
materials as they are expected to have a high oxygen barrier and
affinity to wood fibers for application in food packaging and
printing papers.
[0193] Cellulose materials provided herein are suitable as
additives to improve the durability of paint, protecting paints and
varnishes from attrition caused by UV radiation.
[0194] Cellulose materials provided herein are suitable as
thickening agents in food and cosmetics products. Cellulose can be
used as thixotropic, biodegradable, dimensionally stable thickener
(stable against temperature and salt addition). Cellulose materials
provided herein are suitable as a Pickering stabilizer for
emulsions and particle stabilized foam.
[0195] The large surface area of these cellulose materials in
combination with their biodegradability makes them attractive
materials for highly porous, mechanically stable aerogels.
Cellulose aerogels display a porosity of 95% or higher, and they
are ductile and flexible.
[0196] Drilling fluids are fluids used in drilling in the natural
gas and oil industries, as well as other industries that use large
drilling equipment. The drilling fluids are used to lubricate,
provide hydrostatic pressure, and to keep the drill cool, and the
hole as clean as possible of drill cuttings. Cellulose materials
provided herein are suitable as additives to these drilling
fluids.
[0197] In this detailed description, reference has been made to
multiple embodiments of the invention and non-limiting examples
relating to how the invention can be understood and practiced.
Other embodiments that do not provide all of the features and
advantages set forth herein may be utilized, without departing from
the spirit and scope of the present invention. This invention
incorporates routine experimentation and optimization of the
methods and systems described herein. Such modifications and
variations are considered to be within the scope of the invention
defined by the claims.
[0198] All publications, patents, and patent applications cited in
this specification are herein incorporated by reference in their
entirety as if each publication, patent, or patent application were
specifically and individually put forth herein.
[0199] Where methods and steps described above indicate certain
events occurring in certain order, those of ordinary skill in the
art will recognize that the ordering of certain steps may be
modified and that such modifications are in accordance with the
variations of the invention. Additionally, certain of the steps may
be performed concurrently in a parallel process when possible, as
well as performed sequentially.
[0200] Therefore, to the extent there are variations of the
invention, which are within the spirit of the disclosure or
equivalent to the inventions found in the appended claims, it is
the intent that this patent will cover those variations as well.
The present invention shall only be limited by what is claimed.
* * * * *