U.S. patent application number 15/910142 was filed with the patent office on 2018-07-05 for processing materials with ion beams.
The applicant listed for this patent is XYLECO, INC.. Invention is credited to Marshall Medoff.
Application Number | 20180185811 15/910142 |
Document ID | / |
Family ID | 51904526 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180185811 |
Kind Code |
A1 |
Medoff; Marshall |
July 5, 2018 |
PROCESSING MATERIALS WITH ION BEAMS
Abstract
Materials such as biomass (e.g., plant biomass, animal biomass,
and municipal waste biomass) and hydrocarbon-containing materials
are processed to produce useful products, such as fuels. For
example, systems are described that can use feedstock materials,
such as cellulosic and/or lignocellulosic materials and/or starchy
materials, or oil sands, oil shale, tar sands, bitumen, and coal to
produce altered materials such as fuels (e.g., ethanol and/or
butanol). The processing includes exposing the materials to an ion
beam.
Inventors: |
Medoff; Marshall;
(Wakefield, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XYLECO, INC. |
WAKEFIELD |
MA |
US |
|
|
Family ID: |
51904526 |
Appl. No.: |
15/910142 |
Filed: |
March 2, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15601939 |
May 22, 2017 |
9937478 |
|
|
15910142 |
|
|
|
|
15178958 |
Jun 10, 2016 |
9687810 |
|
|
15601939 |
|
|
|
|
13434701 |
Mar 29, 2012 |
9387454 |
|
|
15178958 |
|
|
|
|
12486436 |
Jun 17, 2009 |
8147655 |
|
|
13434701 |
|
|
|
|
61073680 |
Jun 18, 2008 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 19/081 20130101;
C10L 9/00 20130101; Y02E 50/30 20130101; C12P 3/00 20130101; B01J
19/10 20130101; C10L 2290/36 20130101; C10L 1/02 20130101; B01J
2219/12 20130101; C10L 2290/26 20130101; C12P 7/02 20130101; C10L
5/44 20130101; H01J 37/05 20130101; C10L 2200/0469 20130101; B01J
19/12 20130101; B01J 19/085 20130101; B01J 2219/0879 20130101; H01J
37/04 20130101 |
International
Class: |
B01J 19/08 20060101
B01J019/08; C12P 3/00 20060101 C12P003/00; C10L 1/02 20060101
C10L001/02; C12P 7/02 20060101 C12P007/02 |
Claims
1. A method of making a fuel, the method comprising: irradiating a
cellulosic or lignocellulosic material with an ion beam comprising
a first distribution of ion energies having a full width at half
maximum of W and a second distribution of energies with a full
width at half maximum W2 of more than W; converting the irradiated
material to produce a fuel.
2. The method of claim 1, wherein the second distribution of
energies is produced by adjusting the energies of some of the ions
based on a thickness of the cellulosic or lignocellulosic
material.
3. The method of claim 1, wherein the relative dose of irradiation
is substantially uniform through the thickness of the cellulosic or
lignocellulosic material.
4. The method of claim 1, wherein the cellulosic or lignocellulosic
material has been physically prepared prior to irradiating to
render it more uniform.
5. The method of claim 3, wherein the material has been prepared to
reduce the biomass particle size to an average particle size of
r.
6. The method of claim 5, wherein the second distribution of
energies is produced by adjusting the energy of some of the ions
based on the average particle size r.
7. The method of claim 1, wherein the irradiation reduces the
average molecular weight of the cellulosic or lignocellulosic
material.
8. The method of claim 1, wherein the fuel is an alcohol.
9. The method of claim 1, wherein the fuel is ethanol, butanol or
hydrogen.
10. The method of claim 1, wherein the irradiated material is
converted utilizing a bacteria.
11. The method of claim 1, wherein the irradiated material is
converted utilizing a yeast.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
15/601,939, filed May 22, 2017, which is a continuation of U.S.
Ser. No. 15/178,958, filed Jun. 10, 2016, now U.S. Pat. No.
9,687,810, granted on Jun. 27, 2017, which is a continuation of
U.S. Ser. No. 13/434,701, filed Mar. 29, 2012, now U.S. Pat. No.
9,387,454, granted on Jul. 12, 2016, which is a continuation of
U.S. Ser. No. 12/486,436, filed Jun. 17, 2009, now U.S. Pat. No.
8,147,655 granted on Apr. 3, 2012, which claims priority to U.S.
Provisional Application Ser. No. 61/073,680, filed Jun. 18, 2008.
The complete disclosure of each of these applications is hereby
incorporated by reference herein.
BACKGROUND
[0002] Biomass, particularly biomass waste, and
hydrocarbon-containing materials, such as oil sands, oil shale, tar
sands, bitumen, and coal, are widely available. It would be useful
to derive materials and fuel, such as ethanol, from biomass and
hydrocarbon-containing material.
SUMMARY
[0003] Biomass and hydrocarbon-containing material can be processed
to alter its structure at one or more levels. The processed
materials can then be used as a source of altered materials and/or
fuel.
[0004] Many embodiments of this application use Natural Force.TM.
Chemistry (NFC). Natural Force.TM. Chemistry methods use the
controlled application and manipulation of physical forces, such as
particle beams, gravity, light, etc., to create intended structural
and chemical molecular change.
[0005] Methods for changing a molecular and/or a supramolecular
structure of a material, e.g., any biomass material, can include
treating the material with radiation. In particular, the radiation
can include particles, particularly charged particles (e.g.,
accelerated charged particles). Charged particles include ions,
such as positively charged ions, such as protons, carbon or oxygen
ions. The radiation can be applied in an amount sufficient to
change the molecular structure and/or supramolecular structure of
the material. The radiation can also be applied to produce one or
more products from the material. The material can in some cases
include carbohydrates or materials that include carbohydrates,
e.g., cellulosic materials, lignocellulosic materials, starchy
materials, or mixtures of any biomass materials.
[0006] Particles having a different charge than electrons and/or
particles heavier than electrons can be utilized for the
irradiation. For example, protons, helium nuclei, argon ions,
silicon ions, neon ions, carbon ions, phosphorus ions, oxygen ions
or nitrogen ions can be utilized to modify the structure of the
biomass, e.g., breakdown the molecular weight or increase the
molecular weight of the biomass. In some embodiments, heavier
particles can induce higher amounts of chain scission in comparison
to electrons or photons. In addition, in some instances, positively
charged particles can induce relatively large amounts of chain
scission due to their acidity. In certain instances, negatively
charged particles can induce relatively large amounts of chain
scission due to their alkalinity.
[0007] Accordingly, in one aspect, the invention features a method
of changing a molecular structure of a material, e.g., a biomass
material or a hydrocarbon-containing material, by producing an ion
beam comprising a first distribution of ion energies having a full
width at half maximum of w; adjusting the energies of at least some
of the ions to produce a second distribution of ion energies in the
ion beam having a full width at half maximum of more than w; and
exposing the material to the adjusted ion beam. The energies of at
least some of the ions can be adjusted based on, for example, a
thickness of the material.
[0008] In another aspect, the invention features a method of
changing a molecular structure of a material, e.g., a biomass
material or a hydrocarbon-containing material, by producing an ion
beam comprising a distribution of ion energies having a full width
at half maximum of w; directing the ion beam to pass through a
scattering element configured to increase the full width at half
maximum of the distribution of ion energies to a value larger than
w; and exposing the material to the ion beam after the ion beam has
passed through the scattering element.
[0009] In yet another aspect, the invention features a method of
changing a molecular structure of a material, e.g., a biomass
material or a hydrocarbon-containing material, by producing an ion
beam having a distribution of ion energies, the distribution having
a most probable energy E; filtering the ion beam to remove at least
some ions having an energy less than E from the ion beam; and
exposing the material to the filtered ion beam.
[0010] In a further aspect, the invention features a method of
changing a molecular structure of a material, e.g., a biomass
material or a hydrocarbon-containing material, by producing an ion
beam having a distribution of ion energies; adjusting the
distribution of ion energies based on an expected ion dose profile
in the material; and exposing the material to the adjusted ion
beam.
[0011] The invention also features a method of changing a molecular
structure of a material, e.g., a biomass material or a
hydrocarbon-containing material, by producing an ion beam having a
distribution of ion energies; adjusting the distribution of ion
energies based on a full width at half maximum (FWHM) of a Bragg
peak of an expected ion dose profile in the material; and exposing
the material to the adjusted ion beam, wherein the adjusting
comprises increasing the FWHM to reduce a difference between a
thickness of the biomass material and the FWHM.
[0012] In some cases, following the adjusting, the difference
between the thickness of the material and the FWHM is 0.01 cm or
less.
[0013] In yet another aspect, the invention features a method of
changing a molecular structure of a material by producing a first
ion beam from an ion source, the first ion beam having a first
average ion energy; exposing the material to the first ion beam;
adjusting the ion source to produce a second ion beam having a
second average ion energy different from the first average ion
energy; and exposing the material to the second ion beam.
[0014] In some cases, the method further includes repeating the
adjusting and exposing to expose the material to a plurality of ion
beams having different average ion energies. The composition of the
first and second ion beams can be the same.
[0015] In a further aspect, the invention features a method of
changing a molecular structure of a material by:
[0016] producing a first ion beam from an ion source, the first ion
beam having a first average ion energy corresponding to a first
position of a Bragg peak in an expected ion dose profile of the
material;
[0017] exposing the material to the first ion beam;
[0018] adjusting the ion source to produce a second ion beam having
a second average ion energy corresponding to a second position of
the Bragg peak different from the first position; and
[0019] exposing the material to the second ion beam.
[0020] In some cases, the method further includes repeating the
adjusting and exposing to expose the material to a plurality of ion
beams corresponding to different positions of the Bragg peak. The
composition of the first and second ion beams can be the same.
[0021] In yet another aspect, the invention features a method of
changing a molecular structure of a material by producing an ion
beam from an ion source, the ion beam comprising a first type of
ions and a second type of ions different from the first type of
ions; and exposing the material to the ion beam.
[0022] For example, the first type of ions can comprise hydrogen
ions and the second type of ions can comprise carbon ions, or the
first type of ions can comprise hydrogen ions and the second type
of ions can comprise oxygen ions, or the first and second types of
ions can comprise at least one of protons and hydride ions. In some
cases the first and second types of ions each have ion energies
between 0.01 MeV and 10 MeV.
[0023] In another aspect, the invention features a method of
changing a molecular structure of a material by producing a ion
beam having a divergence angle of 10 degrees or more, e.g., 20
degrees or more, at a surface of the material; and exposing the
biomass material to the ion beam.
[0024] In yet another aspect, the invention features a method of
changing a molecular structure of a material by adjusting an ion
source to produce an ion beam having an average ion current and an
average ion energy; and exposing the material to the ion beam,
wherein the ion source is adjusted based on an expected ion dose
profile in the material and wherein each portion of the material
receives a radiation dose of between 0.01 Mrad and 50 Mrad, e.g.,
between 0.1 Mrad and 20 Mrad, as a result of exposure to the ion
beam.
[0025] In another aspect, changing a molecular structure of a
material includes producing an ion beam including a first
distribution of ion energies having a full width at half maximum of
W, adjusting the energies of at least some of the ions based on a
thickness of a hydrocarbon-containing material to produce a second
distribution of ion energies in the ion beam having a full width at
half maximum of more than W, and exposing the
hydrocarbon-containing material to the adjusted ion beam. The
hydrocarbon-containing material can be selected from the group
consisting of oil sands, oil shale, tar sands, bitumen, and
coal.
[0026] In another aspect, changing a molecular structure of a
material includes producing an ion beam including a first
distribution of ion energies having a full width at half maximum of
W, adjusting the energies of at least some of the ions to produce a
second distribution of ion energies in the ion beam having a full
width at half maximum of more than W, and exposing the material to
the adjusted ion beam.
[0027] In some instances, the material is a biomass material, a
non-biomass material, or any combination thereof. For example, the
material can be a hydrocarbon-containing material such as oil
sands, oil shale, tar sands, bitumen, coal, and other mixtures of
hydrocarbons and non-hydrocarbon material.
[0028] In some cases, the method further includes exposing the
material to a plurality of electrons or to ultrasonic energy
following exposure to the ion beam.
[0029] Some implementations of any of the above-mentioned aspects
of the invention can include one or more of the following features.
Adjusting the energies of at least some of the ions can include
adjusting based on a thickness of the material exposed to the ion
beam. In some cases, adjusting the energies of at least some of the
ions can include adjusting based on an expected ion dose profile in
the material. Adjusting can also include increasing a full width at
half maximum of a Bragg peak of an expected ion dose profile in the
material enough to reduce a difference between a thickness of the
material and the full width at half maximum of the Bragg peak.
Following adjusting, the difference between the thickness of the
material and the full width at half maximum of the Bragg peak can
be 0.01 centimeter or less.
[0030] The full width at half maximum of the second distribution
can be larger than w by a factor of 2.0 or more, e.g., by a factor
of 4.0 or more. Adjusting the energies of at least some of the ions
can include directing the ions to pass through a scattering
element, e.g., a hemispherical analyzer. In some cases, the
adjusted ion beam passes through a fluid prior to being incident on
the material, e.g. through air at a pressure of 0.5 atmospheres or
more. The ion beam can include two or more different types of ions,
e.g., hydrogen ions and carbon ions or hydrogen ions and oxygen
ions. The ion beam can include at least one of protons and hydride
ions. The average energy of the ions in the ion beam can be between
0.01 MeV and 10 MeV.
[0031] Changing a molecular structure of a material, such as a
biomass feedstock or a hydrocarbon-containing material, as used
herein, means changing the chemical bonding arrangement, such as
the type and quantity of functional groups or conformation of the
structure. For example, the change in the molecular structure can
include changing the supramolecular structure of the material,
oxidation of the material, changing an average molecular weight,
changing an average crystallinity, changing a surface area,
changing a degree of polymerization, changing a porosity, changing
a degree of branching, grafting on other materials, changing a
crystalline domain size, or changing an overall domain size.
[0032] Biomass or hydrocarbon-containing material can be exposed to
radiation, for example an ion beam, e.g., a beam according to one
or more of the configurations described herein. The beam and
duration of exposure can be chosen such that the molecular
structure of the material is altered. The material can be treated
prior to and/or after the exposure. The exposed material can be
used in a variety of applications, including fermentation and the
production of composite materials.
[0033] Also featured are systems and devices for treating materials
with radiation as disclosed herein. An exemplary system includes a
reservoir for biomass, a device that produces a particle beam,
e.g., as described herein, and a conveyance device for moving
biomass from the reservoir to the device that produces a particle
beam.
[0034] Implementations may include one or more of any of the
features described herein.
[0035] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, suitable methods and materials are described below. All
publications, patent applications, patents, and other references
mentioned herein are incorporated by reference in their entirety.
In case of conflict, the present specification, including
definitions, will control. In addition, the materials, methods, and
examples are illustrative only and not intended to be limiting.
[0036] This application incorporates by reference herein the entire
contents of International Application No. PCT/US2007/022719, filed
Oct. 26, 2007, and U.S. Provisional Application No. 61/049,406,
filed Apr. 30, 2008.
[0037] Other features and advantages will be apparent from the
following detailed description, and from the claims.
DESCRIPTION OF DRAWINGS
[0038] FIG. 1 is a block diagram illustrating conversion of biomass
into products and co-products.
[0039] FIG. 2 is a schematic diagram showing dose profiles for
ions, electrons, and photons in a condensed-phase material.
[0040] FIG. 3 is a schematic diagram of an ion beam exposure
system.
[0041] FIGS. 4A and 4B are schematic diagrams showing ion beam
energy distributions.
[0042] FIG. 4C is a schematic diagram showing ion dose profiles in
an exposed sample.
[0043] FIG. 5 is a schematic diagram of a scattering element that
includes multiple sub-regions.
[0044] FIG. 6 is a schematic diagram of an ion beam exposure system
that includes an ion filter.
[0045] FIGS. 7A-C are schematic diagrams showing energy
distributions for unfiltered and filtered ion beams.
[0046] FIG. 8 is a schematic diagram showing three ion dose
profiles corresponding to exposure of a sample to ion beams having
different average energies.
[0047] FIG. 9A is a schematic diagram showing a net ion dose
profile for an exposed sample based on the three ion dose profiles
of FIG. 8.
[0048] FIG. 9B is a schematic diagram showing three different ion
dose profiles corresponding to ion beams of different average
energy and ion current.
[0049] FIG. 9C is a schematic diagram showing a net ion dose
profile based on the three ion dose profiles of FIG. 9B.
[0050] FIG. 10A is a schematic diagram showing three different ion
dose profiles corresponding to exposure of a sample to beams of
three different types of ions.
[0051] FIG. 10B is a schematic diagram showing a net ion dose
profile based on the three ion dose profiles of FIG. 10A.
[0052] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0053] Treating biomass with radiation is useful for producing fuel
and products. Generally biomass material is physically prepared
before treatment with radiation. The material can be prepared so as
to render it more uniform, e.g., to reduce particle size, to alter
water content, to control viscosity, and so forth. The material is
treated with radiation to alter the molecular and/or
supra-molecular structure. In addition, the material can be treated
in other ways, for example, with sonication, oxidation, pyrolysis,
and steam explosion. The resulting material can be stored or used
in a variety ways.
[0054] One application is fermentation to produce a combustible
product, such as an alcohol. Microorganisms can be combined with
the resulting material, and, optionally, other ingredients. The
combination is fermented and product is recovered. For example,
alcohols can be recovered by distillation.
[0055] In some embodiments, the radiation is applied on a large
scale, for example to a batch of at least 50 kg, 100 kg, or 500 kg.
The treatment can also be applied in a continuous or
semi-continuous mode, for example, to material that moves under a
radiation beam, e.g., so as to process at least 100, 500, 1000,
5000, or 20000 kg per hour.
[0056] A variety of biomass materials can be used as a starting
material. Examples of biomass include plant biomass, animal
biomass, and municipal waste biomass. Biomass also includes
feedstock materials such as cellulosic and/or lignocellulosic
materials.
[0057] Often biomass is material that includes a carbohydrate, such
as cellulose. Generally, any biomass material that is or includes
carbohydrates composed entirely of one or more saccharide units or
that include one or more saccharide units can be processed by any
of the methods described herein. For example, the biomass material
can be cellulosic or lignocellulosic materials, or starchy
materials, such as kernels of corn, grains of rice or other
foods.
[0058] Additional examples of biomass materials include paper,
paper products, wood, wood-related materials, particle board,
grasses, rice hulls, bagasse, cotton, jute, hemp, flax, bamboo,
sisal, abaca, straw, corn cobs, rice hulls, coconut hair, algae,
seaweed, cotton, synthetic celluloses, or mixtures of any of these.
Still other examples are described in WO 2008/073186, filed Oct.
26, 2007, and U.S. Ser. No. 12/429,045, filed Apr. 23, 2009.
[0059] Various biomass materials are often readily available,
but--unless pretreated--can sometimes be difficult to process,
e.g., by fermentation, or can give sub-optimal yields at a slow
rate. In the methods described herein, feedstock materials can be
first physically prepared for processing, often by size reduction
of raw feedstock materials. Physically prepared feedstock can be
pretreated or processed using one or more of radiation, sonication,
oxidation, pyrolysis, and steam explosion. The various pretreatment
systems and methods can be used in combinations of two, three, or
even four of these technologies. Combinations of various
pretreatment methods are generally disclosed in WO 2008/073186, for
example.
[0060] In some cases, to provide materials that include a
carbohydrate, such as cellulose, that can be converted by a
microorganism to a number of desirable products, such as a
combustible fuels (e.g., ethanol, butanol or hydrogen), feedstocks
that include one or more saccharide units can be treated by any one
or more of multiple processes. Other products and co-products that
can be produced include, for example, human food, animal feed,
pharmaceuticals, and nutriceuticals. Examples of other products are
described in U.S. Ser. Nos. 12/417,900, 12/417,707, 12/417,720, and
12/417,731, all of which were filed Apr. 3, 2009.
[0061] Where the biomass is or includes a carbohydrate it may
include, for example, a material having one or more
.beta.-1,4-linkages and having a number average molecular weight
between about 3,000 and 50,000. Such a carbohydrate is or includes
cellulose (I), which is derived from (.beta.-glucose 1) through
condensation of .beta.(1.fwdarw.4)-glycosidic bonds. This linkage
contrasts itself with that for .alpha.(1.fwdarw.4)-glycosidic bonds
present in starch and other carbohydrates.
[0062] Starchy materials include starch itself, e.g., corn starch,
wheat starch, potato starch or rice starch, a derivative of starch,
or a material that includes starch, such as an edible food product
or a crop. For example, the starchy material can be arracacha,
buckwheat, banana, barley, cassava, kudzu, oca, sago, sorghum,
regular household potatoes, sweet potato, taro, yams, or one or
more beans, such as favas, lentils or peas. Blends of any one or
more starchy material are also starchy materials. In particular
embodiments, the starchy material is derived from corn. Various
corn starches and derivatives are described in "Corn Starch," Corn
Refiners Association (11th Edition, 2006).
[0063] Biomass materials that include low molecular weight sugars
can, e.g., include at least about 0.5 percent by weight of the low
molecular sugar, e.g., at least about 2, 3, 4, 5, 6, 7, 8, 9, 10,
12.5, 25, 35, 50, 60, 70, 80, 90 or even at least about 95 percent
by weight of the low molecular weight sugar. In some instances, the
biomass is composed substantially of the low molecular weight
sugar, e.g., greater than 95 percent by weight, such as 96, 97, 98,
99 or substantially 100 percent by weight of the low molecular
weight sugar.
[0064] Biomass materials that include low molecular weight sugars
can be agricultural products or food products, such as sugarcane
and sugar beets or an extract therefrom, e.g., juice from
sugarcane, or juice from sugar beets. Biomass materials that
include low molecular weight sugars can be substantially pure
extracts, such as raw or crystallized table sugar (sucrose). Low
molecular weight sugars include sugar derivatives. For example, the
low molecular weight sugars can be oligomeric (e.g., equal to or
greater than a 4-mer, 5-mer, 6-mer, 7-mer, 8-mer, 9-mer or 10-mer),
trimeric, dimeric, or monomeric. When the carbohydrates are formed
of more than a single repeat unit, each repeat unit can be the same
or different.
[0065] Specific examples of low molecular weight sugars include
cellobiose, lactose, sucrose, glucose and xylose, along with
derivatives thereof. In some instances, sugar derivatives are more
rapidly dissolved in solution or utilized by microbes to provide a
useful material, such as ethanol or butanol.
[0066] Combinations of any biomass materials described herein
(e.g., combinations of any biomass materials, components, products,
and/or co-products generated using the methods described herein)
can be utilized for making any of the products described herein,
such as ethanol. For example, blends of cellulosic materials and
starchy materials can be utilized for making products.
[0067] Fuels and other products (e.g., ethanol, bioethanol, other
alcohols, and other combustible hydrocarbons) produced via the
methods disclosed herein can be blended with other
hydrocarbon-containing species. For example, ethanol produced using
any of the methods disclosed herein can be blended with gasoline to
produce "gasohol," which can be used as combustible fuel in a wide
variety of applications, including automobile engines.
Biomass Treatment Processes
[0068] FIG. 1 shows a system 100 for converting biomass,
particularly biomass with significant cellulosic and
lignocellulosic components and/or starchy components, into useful
products and co-products. System 100 includes a feed preparation
subsystem 110, a pretreatment subsystem 114, a primary process
subsystem 118, and a post-processing subsystem 122. Feed
preparation subsystem 110 receives biomass in its raw form,
physically prepares the biomass for use as feedstock by downstream
processes (e.g., reduces the size of and homogenizes the biomass),
and stores the biomass both in its raw and feedstock forms.
[0069] Biomass with significant cellulosic and/or lignocellulosic
components, or starchy components can have a high average molecular
weight and crystallinity that be modified by one or more
pretreatments to facilitate use of the material.
[0070] Pretreatment subsystem 114 receives feedstock from the feed
preparation subsystem 110 and prepares the feedstock for use in
primary production processes by, for example, reducing the average
molecular weight and crystallinity of the feedstock and/or
increasing the surface area and/or porosity of the feedstock. In
some cases, the pre-treated biomass material has a low moisture
content, e.g., less than about 7.5, 5, 3, 2.5, 2, 1.5, 1, or 0.5
percent water by weight. Moisture reduction can be achieved, e.g.,
by drying biomass material. Pretreatment processes can avoid the
use of harsh chemicals such as strong acids and bases.
[0071] Primary process subsystem 118 receives pretreated feedstock
from pretreatment subsystem 114 and produces useful products (e.g.,
ethanol, other alcohols, pharmaceuticals, and/or food products).
Primary production processes typically include processes such as
fermentation (e.g., using microorganisms such as yeast and/or
bacteria), chemical treatment (e.g., hydrolysis), and
gasification.
[0072] In some cases, the output of primary process subsystem 118
is directly useful but, in other cases, the output requires further
processing provided by post-processing subsystem 122.
Post-processing subsystem 122 provides further processing to
product streams from primary process system 118 (e.g., distillation
and denaturation of ethanol) as well as treatment for waste streams
from the other subsystems. In some cases, the co-products of
subsystems 114, 118, 122 can also be directly or indirectly useful
as secondary products and/or in increasing the overall efficiency
of system 100. For example, post-processing subsystem 122 can
produce treated water to be recycled for use as process water in
other subsystems and/or can produce burnable waste which can be
used as fuel for boilers producing steam and/or electricity. In
general, post-processing steps can include one or more steps such
as distillation to separate different components, wastewater
treatment (e.g., screening, organic equalization, sludge
conversion), mechanical separation, and/or waste combustion.
Ion Beam Systems for Biomass Pretreatment
[0073] Ion beam pretreatment (e.g., exposure to ions) of biomass
can be a particularly efficient, economical, and high-throughput
treatment method. Ion beam pretreatment generally includes exposing
biomass (mechanically processed, or unprocessed) to one or more
different types of ions generated in one or more ion sources. The
ions can be accelerated in accelerator systems that are coupled to
the ion sources, and can produce ions with varying energies and
velocities. Typically, in ion-based pretreatment, ions are not
accelerated to sufficient energies to cause large amounts of x-ray
radiation to be produced. Accordingly, vaulting and shielding
requirements for ion sources can be considerably relaxed relative
to similar requirements for electron sources.
[0074] When ion beam radiation is utilized, it can be applied to
any sample that is dry or wet, or even dispersed in a liquid, such
as water. For example, ion beam irradiation can be performed on
cellulosic and/or lignocellulosic material in which less than about
25 percent by weight of the cellulosic and/or lignocellulosic
material has surfaces wetted with a liquid, such as water. In some
embodiments, ion beam irradiating is performed on cellulosic and/or
lignocellulosic material in which substantially none of the
cellulosic and/or lignocellulosic material is wetted with a liquid,
such as water.
[0075] When ion beam irradiation is utilized, it can be applied
while the cellulosic and/or lignocellulosic material is exposed to
air, oxygen-enriched air, or even oxygen itself, or blanketed by an
inert gas such as nitrogen, argon, or helium. When oxidation of the
biomass material is desired, an oxidizing environment is utilized,
such as air or oxygen, and the properties of the ion beam source
can be adjusted to induce reactive gas formation, e.g., formation
of ozone and/or oxides of nitrogen. These reactive gases react with
the biomass material, alone or together with incident ions, to
cause degradation of the material. As an example, when ion beam
exposure of biomass is utilized, the biomass can be exposed to ions
under a pressure of one or more gases of greater than about 2.5
atmospheres, such as greater than 5, 10, 15, 20 or even greater
than about 50 atmospheres.
[0076] Ions that are incident on biomass material typically scatter
from and ionize portions of the biomass via Coulomb scattering. The
interaction between the ions and the biomass can also produce
energetic electrons (e.g., secondary electrons) that can further
interact with the biomass (e.g., causing further ionization). Ions
can be positively charged or negatively charged, and can bear a
single positive or negative charge, or multiple charges, e.g., one,
two, three or even four or more charges. In instances in which
chain scission is desired, positively charged particles may be
desirable, in part, due to their acidic nature.
[0077] The ions to which biomass material is exposed can have the
mass of a resting electron, or greater, e.g., 500, 1000, 1500, or
2000 or more, e.g., 10,000 or even 100,000 times the mass of a
resting electron. For example, the ions can have a mass of from
about 1 atomic unit to about 150 atomic units, e.g., from about 1
atomic unit to about 50 atomic units, or from about 1 to about 25,
e.g., 1, 2, 3, 4, 5, 10, 12 or 15 amu. Exemplary ions and ion
accelerators are discussed in Introductory Nuclear Physics, Kenneth
S. Krane, John Wiley & Sons, Inc. (1988), Krsto Prelec, FIZIKA
B 6 (1997) 4, 177-206, Chu, William T., "Overview of Light-Ion Beam
Therapy", Columbus-Ohio, ICRU-IAEA Meeting, 18-20 Mar. 2006, Iwata,
Y. et al., "Alternating-Phase-Focused IH-DTL for Heavy-Ion Medical
Accelerators", Proceedings of EPAC 2006, Edinburgh, Scotland, and
Leitner, C. M. et al., "Status of the Superconducting ECR Ion
Source Venus", Proceedings of EPAC 2000, Vienna, Austria.
[0078] A wide variety of different types of ions can be used to
pretreat biomass material. For example, protons, helium nuclei,
argon ions, silicon ions, neon ions, carbon ions, phosphorus ions,
oxygen ions or nitrogen ions can be utilized. In some embodiments,
the ions can induce higher amounts of chain scission than an
equivalent dose of electrons. In some instances, positively charged
ions can induce higher amounts of chain scission and/or other
processes than negatively charged ions due to their acidity.
Alternatively, in certain embodiments, depending upon the nature of
the biomass, negatively charged ions can be more effective than
positively charged ions at inducing chain scission and/or other
processes, due to their alkaline nature.
[0079] Following generation and/or acceleration, the average energy
of ions in an ion beam can be from about 1.0 MeV/atomic unit to
about 6,000 MeV/atomic unit, e.g., from about 3 MeV/atomic unit to
about 4,800 MeV/atomic unit, or from about 10 MeV/atomic unit to
about 1,000 MeV/atomic unit.
[0080] In general, many different types of ions can be used to
irradiate biomass materials. For example, in some embodiments, ion
beams can include relatively light ions, such as protons and/or
helium ions. In certain embodiments, the ion beams can include
moderately heavier ions, such as carbon ions, nitrogen ions, oxygen
ions, and/or neon ions. In some embodiments, ion beams can include
still heavier ions, such as argon ions, silicon ions, phosphorus
ions, sodium ions, calcium ions, and/or iron ions.
[0081] In certain embodiments, ion beams used to irradiate biomass
materials can include more than one different type of ion. For
example, ion beams can include mixtures of two or more (e.g.,
three, four, five, six or more) different types of ions. Exemplary
mixtures can include carbon ions and protons, carbon ions and
oxygen ions, nitrogen ions and protons, and iron ions and protons.
More generally, mixtures of any of the ions discussed herein (or
any other ions) can be used to form ion beams that are used to
irradiate biomass. In particular, mixtures of relatively light and
relatively heavier ions can be used in a single ion beam, where
each of the different types of ions has different effectiveness in
irradiating different types of biomass materials.
[0082] In some embodiments, ion beams for irradiating biomass
materials include positively-charged ions. The positively charged
ions can include, for example, positively charged hydrogen ions
(e.g., protons), noble gas ions (e.g., helium, neon, argon), carbon
ions, nitrogen ions, oxygen ions, silicon atoms, phosphorus ions,
and metal ions such as sodium ions, calcium ions, and/or iron ions.
Without wishing to be bound by any theory, it is believed that such
positively-charged ions behave chemically as Lewis acid moieties
when exposed to biomass materials, initiating and sustaining
reactions such as cationic ring- and chain-opening scission
reactions in an acidic and/or oxidative environment.
[0083] In certain embodiments, ion beams for irradiating biomass
materials include negatively-charged ions. Negatively charged ions
can include, for example, negatively charged hydrogen ions (e.g.,
hydride ions), and negatively charged ions of various relatively
electronegative nuclei (e.g., oxygen ions, nitrogen ions, carbon
ions, silicon ions, and phosphorus ions). Without wishing to be
bound by any theory, it is believed that such negatively-charged
ions behave chemically as Lewis base moieties when exposed to
biomass materials, causing anionic ring- and chain-opening scission
reactions in a basic and/or reducing environment.
[0084] In some embodiments, beams for irradiating biomass materials
can include neutral atoms. For example, any one or more of hydrogen
atoms, helium atoms, carbon atoms, nitrogen atoms, oxygen atoms,
neon atoms, silicon atoms, phosphorus atoms, argon atoms, and iron
atoms can be included in beams that are used for irradiation of
biomass materials. In general, mixtures of any two or more of the
above types of atoms (e.g., three or more, four or more, or even
more) can be present in the beams.
[0085] The preceding discussion has focused on ion beams that
include mononuclear ions and/or neutral particles (e.g., atomic
ions and neutral atoms). Typically, such particles are the
easiest--in energetic terms--to generate, and parent particles from
which these species are generated may be available in abundant
supply. However, in some embodiments, beams for irradiating biomass
materials can include one or more types of ions or neutral
particles that are polynuclear, e.g., including multiple nuclei,
and even including two or more different types of nuclei. For
example, ion beams can include positive and/or negative ions and/or
neutral particles formed from species such as N.sub.2, O.sub.2,
H.sub.2, CH.sub.4, and other molecular species. Ion beams can also
include ions and/or neutral particles formed from heavier species
that include even more nuclei, such as various hydrocarbon-based
species and/or various inorganic species, including coordination
compounds of various metals.
[0086] In certain embodiments, ion beams used to irradiate biomass
materials include singly-charged ions such as one or more of
H.sup.+, H.sup.-, He.sup.+, Ne.sup.+, Ar.sup.+, C.sup.+, C.sup.-,
O.sup.+, O.sup.-, N.sup.+, N.sup.-, Si.sup.+, Si.sup.-, P.sup.+,
P.sup.-, Na.sup.+, Ca.sup.+, Fe.sup.+, Rh.sup.+, Ir.sup.+,
Pt.sup.+, Re.sup.+, Ru.sup.+, and Os.sup.+. In some embodiments,
ion beams can include multiply-charged ions such as one or more of
C.sup.2+, C.sup.3+, C.sup.4+, N.sup.3+, N.sup.5+, N.sup.3-,
O.sup.2+, O.sup.2-, O.sub.2.sup.2-, Si.sup.2+, Si.sup.4+,
Si.sup.2-, and Si.sup.4-. In general, the ion beams can also
include more complex polynuclear ions that bear multiple positive
or negative charges. In certain embodiments, by virtue of the
structure of the polynuclear ion, the positive or negative charges
can be effectively distributed over substantially the entire
structure of the ion. In some embodiments, the positive or negative
charges can be somewhat localized over portions of the structure of
the ions, by virtue of the electronic structures of the ions.
Generally, ion beams used to irradiate biomass materials can
include ions--both positive and/or negative--of any of the
molecular species disclosed herein, and the ions can generally
include one or multiple charges. The ion beams can also include
other types of ions, positively and/or negatively charged, bearing
one or multiple charges.
[0087] Ions and ion beams can be generated using a wide variety of
methods. For example, hydrogen ions (e.g., both protons and hydride
ions) can be generated by field ionization of hydrogen gas and/or
via thermal heating of hydrogen gas. Noble gas ions can be
generated by field ionization. Ions of carbon, oxygen, and nitrogen
can be generated by field ionization, and can be separated from one
another (when they are co-generated) by a hemispherical analyzer.
Heavier ions such as sodium and iron can be produced via thermionic
emission from a suitable target material. Suitable methods for
generating ion beams are disclosed, for example, in U.S.
Provisional Application Nos. 61/049,406 and 61/073,665, and in U.S.
Ser. No. 12/417,699.
[0088] A wide variety of different particle beam accelerators can
be used to accelerate ions prior to exposing biomass material to
the ions. For example, suitable particle beam accelerators include
Dynamitron.RTM. accelerators, Rhodotron.RTM. accelerators, static
accelerators, dynamic linear accelerators (e.g., LINACs), van de
Graaff accelerators, and folded tandem Pelletron accelerators.
These and other suitable accelerators are discussed, for example,
in U.S. Provisional Application Nos. 61/049,406 and 61/073,665, and
in U.S. Ser. No. 12/417,699.
[0089] In some embodiments, combinations of two or more of the
various types of accelerators can be used to produce ion beams that
are suitable for treating biomass. For example, a folded tandem
accelerator can be used in combination with a linear accelerator, a
Rhodotron.RTM. accelerator, a Dynamitron.RTM. accelerator, a static
accelerator, or any other type of accelerator to produce ion beams.
Accelerators can be used in series, with the output ion beam from
one type of accelerator directed to enter another type of
accelerator for additional acceleration. Alternatively, multiple
accelerators can be used in parallel to generate multiple ion beams
for biomass treatment. In certain embodiments, multiple
accelerators of the same type can be used in parallel and/or in
series to generate accelerated ion beams.
[0090] In some embodiments, multiple similar and/or different
accelerators can be used to generate ion beams having different
compositions. For example, a first accelerator can be used to
generate one type of ion beam, while a second accelerator can be
used to generate a second type of ion beam. The two ion beams can
then each be further accelerated in another accelerator, or can be
used to treat biomass.
[0091] Further, in certain embodiments, a single accelerator can be
used to generate multiple ion beams for treating biomass. For
example, any of the accelerators discussed herein (and other types
of accelerators as well) can be modified to produce multiple output
ion beams by sub-dividing an initial ion current introduced into
the accelerator from an ion source. Alternatively, or in addition,
any ion beam produced by any of the accelerators disclosed herein
can include only a single type of ion, or multiple different types
of ions.
[0092] In general, where multiple different accelerators are used
to produce one or more ion beams for treatment of biomass, the
multiple different accelerators can be positioned in any order with
respect to one another. This provides for great flexibility in
producing one or more ion beams, each of which has carefully
selected properties for treating biomass (e.g., for treating
different components in biomass).
[0093] The ion accelerators disclosed herein can also be used in
combination with any of the other biomass treatment steps. For
example, in some embodiments, electrons and ions can be used in
combination to treat biomass. The electrons and ions can be
produced and/or accelerated separately, and used to treat biomass
sequentially (in any order) and/or simultaneously. In certain
embodiments, electron and ion beams can be produced in a common
accelerator and used to treat biomass. Certain ion accelerators can
be configured to produce electron beams as an alternative to, or in
addition to, ion beams. For example, Dynamitron.RTM. accelerators,
Rhodotron.RTM. accelerators, and LINACs can be configured to
produce electron beams for treatment of biomass.
[0094] Moreover, pretreatment of biomass with ion beams can be
combined with other biomass pretreatment methods such as
sonication, pyrolysis, oxidation, steam explosion, and/or
irradiation with other forms of radiation (e.g., electrons, gamma
radiation, x-rays, ultraviolet radiation). In general, other
pretreatment methods such as sonication-based pretreatment can
occur before, during, or after ion-based biomass pretreatment.
Exposure Conditions and Ion Beam Properties
[0095] In general, when a condensed medium is exposed to a charged
particle beam, the charged particles penetrate the medium and
deposit within the medium at a distribution of depths below the
surface upon which the particles are incident. It has generally
been observed (see, for example, FIG. 1 in Prelec (infra, 1997))
that the dose distribution for ions includes a significantly
sharper maximum (the Bragg peak), and that ions exhibit
significantly less lateral scattering, than other particles such as
electrons and neutrons and other forms of electromagnetic radiation
such as x-rays. Accordingly, due to the relatively well-controlled
dosing profile of accelerated ions, they operate relatively
efficiently to alter the structure of biomass material.
Furthermore, as is apparent from FIG. 6 of Prelec (infra, 1997),
heavier ions (such as carbon ions) have even sharper dosing
profiles than lighter ions such as protons, and so the relative
effectiveness of these heavier ions at treating biomass material is
even greater than for lighter ions.
[0096] In some embodiments, the average energy of the accelerated
ions that are incident on biomass material is 1 MeV/u or more
(e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 30, 50, 100, 300,
500, 600, 800, or even 1000 MeV/u or more).
[0097] In certain embodiments, the average energy of the
accelerated ions is 10 MeV or more (e.g., 20, 30, 50, 100, 200,
300, 400, 500, 600, 800, 1000, 2000, 3000, 4000, or even 5000 MeV
or more).
[0098] In certain embodiments, an average velocity of the
accelerated ions is 0.0005 c or more (e.g., 0.005 c or more, 0.05 c
or more, 0.1 c or more, 0.2 c or more, 0.3 c or more, 0.4 c or
more, 0.5 c or more, 0.6 c or more, 0.7 c or more, 0.8 c or more,
0.9 c or more), where c represents the vacuum velocity of light. In
general, for a given accelerating potential, lighter ions are
accelerated to higher velocities than heavier ions. For example,
for a given accelerating potential, a maximum velocity of a
hydrogen ion may be about 0.05 c, while a maximum velocity of a
carbon ion may be about 0.0005 c. These values are only exemplary;
the velocity of the accelerated ions depends on the accelerating
potential applied, the mode of operation of the accelerator, the
number of passes through the accelerating field, and other such
parameters.
[0099] In some embodiments, an average ion current of the
accelerated ions is 10.sup.5 particles/s or more (e.g., 10.sup.6,
10.sup.7, 10.sup.8, 10.sup.9, 10.sup.10, 10.sup.11, 10.sup.12,
10.sup.13, 10.sup.14, 10.sup.15, or even 10.sup.16 particles/s or
more).
[0100] In some embodiments, a radiation dose delivered to biomass
material from an ion beam is 5 Mrad or more (e.g., 10, 15, 20, 30,
40, 50, 60, 80, or even 100 Mrad or more).
[0101] When a sample is exposed to an ion beam, energy is deposited
in the sample according to an ion dose profile (also sometimes
referred to as a depth-dose distribution). FIG. 2 shows a schematic
diagram of a representative ion dose profile 2010 for a
condensed-phase biomass sample. The vertical axis of ion dose
profile 2010 in FIG. 2 shows the relative ion dose, plotted as a
function of depth below a surface of the sample that is exposed to
the ion beam, on the horizontal axis. FIG. 2 also includes, for
comparative purposes, an electron dose profile 2020, a gamma
radiation dose profile 2030, and an x-ray dose profile 2040.
[0102] As shown in FIG. 2, both gamma radiation and x-ray radiation
(and further, other types of electromagnetic radiation) are
absorbed strongly in a region adjacent to the surface of the
sample, leading to the highest energy doses being deposited near
the sample surface. Gamma and x-ray radiation dose profiles 2030
and 2040 decrease approximately exponentially from the surface of
the sample, as progressively fewer photons are able to penetrate
deeper into the sample to be absorbed.
[0103] Electron dose profile 2020 shows a build-up effect whereby,
due to the penetrating ability of Compton electrons, the deposited
energy dose increases in the vicinity of the exposed surface of the
sample to a maximum deposited dose at a penetration depth of,
typically, about 3-4 cm in condensed media. Thereafter, the
relative dose of deposited energy decreases relatively rapidly with
increasing distance beneath the sample surface.
[0104] Ion beams, in contrast, typically have dose profiles that
are sometimes described as being inverse with respect to the dose
profiles of electrons and photons. As shown in FIG. 2, ion dose
profile 2010 includes a region 2012 in which a relatively constant
energy dose is applied to the sample. Thereafter, ion dose profile
2010 includes a region 2014 referred to as the Bragg peak, which
corresponds to a portion of the sample into which a comparatively
larger fraction of the ion beam's energy is deposited, followed by
a region 2016 in which a much smaller energy dose is deposited. The
Bragg peak, which has a full width at half maximum (FWHM) of
.delta., ensures that the dose profile for ions differs
significantly from the dose profiles for electrons and photons of
various wavelengths. As a result, exposing materials such as
biomass materials to ion beams can yield effects that are different
from the effects produced by photons and electron beams.
[0105] Typically, the width .delta. of Bragg peak 2014 depends upon
a number of factors, including the nature of the sample, the type
of ions, and the average ion energy. One important factor that
influences the width .delta. of Bragg peak 2014 is the distribution
of energies in the incident ion beam. In general, the narrower the
distribution of energies in the incident ion beam, the narrower the
width .delta. of Bragg peak 2014. As an example, Bragg peak 2014
typically has a width of about 3 mm or less for a distribution of
ion energies that has a FWHM of 1 keV or less. The width .delta. of
Bragg peak 2014 can be much less than 3 mm under these conditions
as well, e.g., 2.5 mm or less, 2.0 mm or less, 1.5 mm or less, 1.0
mm or less.
[0106] The position of Bragg peak 2014, indicated by .gamma. in
FIG. 2, depends upon a number of factors including the average
energy of the incident ion beam. In general, for larger average ion
beam energies, Bragg peak 2014 will shift to larger depths in FIG.
2, because higher-energy ions have the ability to penetrate more
deeply into a material before most of the ions' kinetic energy is
lost via scattering events.
[0107] Various properties of one or more incident ion beams can be
adjusted to expose samples (e.g., biomass materials) to ion beam
radiation, which can lead to de-polymerization and other
chain-scission reactions in the samples, reducing the molecular
weight of the samples in a predictable and controlled manner. FIG.
3 shows a schematic diagram of an ion beam exposure system 2100.
System 2100 includes an ion source 2110 that generates an ion beam
2150. Optical elements 2120 (including, for example, lenses,
apertures, deflectors, and/or other electrostatic and/or magnetic
elements for adjusting ion beam 2150) direct ion beam 2150 to be
incident on sample 2130, which has a thickness h in a direction
normal to surface 2135 of sample 2130. In addition to directing ion
beam 2150, optical elements 2120 can be used to control various
properties of ion beam 2150, including collimation and focusing of
ion beam 2150. Sample 2130 typically includes, for example, one or
more of the various types of biomass materials that are discussed
herein. System 2100 also includes an electronic controller 2190 in
electrical communication with the various components of the system
(and with other components not shown in FIG. 3). Electronic
controller 2190 can control and/or adjust any of the system
parameters disclosed herein, either fully automatically or in
response to input from a human operator.
[0108] FIG. 3 also shows the ion dose profile that results from
exposure of sample 2130 to ion beam 2150. The position 2160 of the
Bragg peak within sample 2130 depends upon the average energy of
ion beam 2150, the nature of the ions in ion beam 2150, the
material from which sample 2130 is formed, and other factors.
[0109] In many applications of ion beams, such as ion therapy for
tumor eradication, the relatively small width .delta. of Bragg peak
2014 is advantageous, because it allows reasonably fine targeting
of particular tissues within a patient undergoing therapy, and
helps to reduce damage due to exposure of nearby benign
tissues.
[0110] However, when exposing biomass materials such as sample 2130
to ion beam 2150, the relatively small width .delta. of Bragg peak
2014 can restrict throughput. Typically, for example, the thickness
h of sample 2130 is larger than the width .delta. of Bragg peak
2014. In some embodiments, h can be substantially larger than
.delta. (e.g., larger by a factor of 5 or more, or 10 or more, or
20 or more, or 50 or more, or 100 or more, or even more).
[0111] To increase a thickness of sample 2130 in which a selected
dose can be delivered in a particular time interval, the energy
distribution of ion beam 2150 can be adjusted. Various methods can
be used to adjust the energy distribution of ion beam 2150. One
such method is to employ one or more removable scattering elements
2170 positioned in the path of ion beam 2150, as shown in FIG. 3.
Scattering element 2170 can be, for example, a thin membrane formed
of a metal material such as tungsten, tantalum, copper, and/or a
polymer-based material such as Lucite.RTM. polymer.
[0112] Prior to passing through scattering element 2170, ion beam
2150 has an energy distribution of width w, shown in FIG. 4A. When
ion beam 2150 passes through element(s) 2170, at least some of the
ions in ion beam 2150 undergo scattering events with atoms in
element(s) 2170 transferring a portion of their kinetic energy to
the atoms of element(s) 2170. As a result, the energy distribution
of ion beam 2150 is broadened to a width b larger than w, as shown
in FIG. 4B. In particular, the energy distribution of ion beam 2150
acquires a broader low-energy tail as a result of scattering in
element(s) 2170.
[0113] FIG. 4C shows the effect of broadening the ion energy
distribution of ion beam 2150 on the ion dose profiles in sample
2130. Ion dose profile 2140a is produced by exposing sample 2130 to
ion beam 2150 having the ion energy distribution shown in FIG. 4A.
Ion dose profile 2140a includes a relatively narrow Bragg peak. As
a result, the region of sample 2130 in which a relatively high dose
is deposited is small. In contrast, by broadening the ion energy
distribution of ion beam 2150 to yield the distribution shown in
FIG. 4B, ion dose profile 2140b is obtained in sample 2130 after
exposing the sample to the broadened distribution of ion energies.
As dose profile 2140b shows, by broadening the ion energy
distribution, the region of sample 2130 in which a relatively high
dose is deposited is increased relative to ion dose profile 2140a.
By increasing the region of sample 2130 exposed to a relatively
high dose, the throughput of the exposure process can be
improved.
[0114] In certain embodiments, the width b of the broadened energy
distribution can be larger than w by a factor of 1.1 or more (e.g.,
1.2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, or even 10.0
or more).
[0115] Typically, the ion dose profile in sample 2130 produced by
exposure of the sample to the broadened ion energy distribution
shown in FIG. 4B has a Bragg peak having a full width at half
maximum (FWHM) of .epsilon.. As a result of broadening the ion
energy distribution, .epsilon. can be larger than .delta. by a
factor of 1.1 or more (e.g., 1.2 or more, 1.3 or more, 1.5 or more,
1.7 or more, 2.0 or more, 2.5 or more, 3.0 or more, 4.0 or more,
5.0 or more, 6.0 or more, 7.0 or more, 10.0 or more).
[0116] For sample 2130 of thickness h, after broadening the ion
energy distribution of ion beam 2150 and exposing the sample to the
ion beam, a ratio of .epsilon./h can be 1.times.10.sup.-6 or more
(e.g., 1.times.10.sup.-5, 5.times.10.sup.-5, 1.times.10.sup.-4,
5.times.10.sup.-4, 1.times.10.sup.-3, 5.times.10.sup.-3, 0.01,
0.05, 0.08, 0.1, or even 0.5 or more).
[0117] In certain embodiments, sample 2130 includes a plurality of
particles (e.g., approximately spherical particles, and/or fibers,
and/or filaments, and/or other particle types). In general, the
particles have a distribution of different sizes, with an average
particle size r. The ion energy distribution of ion beam 2150 can
be adjusted (e.g., via broadening) based on the average particle
size r of sample 2130 to improve the efficiency of ion-based
treatment of sample 2130. For example, ion beam 2150 can be
adjusted so that a ratio of dr is 0.001 or more (e.g., 0.005 or
more, 0.01 or more, 0.05 or more, 0.1 or more, 0.5 or more, 1.0 or
more, 1.5 or more, 2.0 or more, 2.5 or more, 3.0 or more, 3.5 or
more, 4.0 or more, 5.0 or more, 6.0 or more, 8.0 or more, 10 or
more, 50 or more, 100 or more, 500 or more, 1000 or more, or even
more).
[0118] In some embodiments, a scattering element 2170 can include
multiple different scattering sub-elements that are configured to
broaden the distribution of ion energies in ion beam 2150 by
different amounts. For example, FIG. 5 shows a multi-sub-element
scattering element 2170 that includes sub-elements 2170a-e. Each of
sub-elements 2170a-e broadens the distribution of ion energies in
ion beam 2150 to a different extent. During operation of system
2100, electronic controller 2190 can be configured to select an
appropriate sub-element of scattering element 2170 based on
information such as the thickness h of sample 2130, the type of
ions in ion beam 2150, and the average ion energy in ion beam 2150.
The selection of an appropriate sub-element can be made in fully
automated fashion, or based at least in part on input from a human
operator. Selection of an appropriate sub-element is made by
translating scattering element 2170 in the direction shown by arrow
2175 to position a selected sub-element in the path of ion beam
2150.
[0119] In certain embodiments, other devices can be used in
addition to, or as an alternative to, scattering element(s) 2170.
For example, in some embodiments, combinations of electric and or
magnetic fields, produced by ion optical elements, can be used to
broaden the ion energy distribution of ion beam 2150. Ion beam 2150
can pass through a first field configured to spatially disperse
ions in the ion beam. Then the spatially dispersed ions can pass
through a second field that is well-localized spatially, and which
selectively retards only a portion of the spatially dispersed ions.
The ions then pass through a third field that spatially
re-assembles all of the ions into a collimated beam, which is then
directed onto the surface of sample 2130. Typically, the ion
optical elements used to generate the fields that adjust the ion
energy distribution are controlled by electronic controller 2190.
By applying spatially localized fields selectively, a high degree
of control over the modified ion energy distribution is possible,
including the generation of ion energy distributions having
complicated profiles (e.g., multiple lobes). For example, in some
embodiments, by applying a localized field that accelerates a
portion of the spatially dispersed ion distribution, the ion energy
distribution shown in FIG. 4A can be broadened on the high-energy
side of the distribution maximum.
[0120] The information used by electronic controller 2190 to adjust
the ion energy distribution of ion beam 2150 can include the
thickness h of sample 2130, as discussed above. In some
embodiments, electronic controller 2190 can use information about
the expected ion dose profile in sample 2130 to adjust the ion
energy distribution of ion beam 2150. Information about the
expected ion dose profile can be obtained from a database, for
example, that includes measurements of ion dose profiles acquired
from literature sources and/or from calibration experiments
performed on representative samples of the material from which
sample 2130 is formed. Alternatively, or in addition, information
about the expected ion dose profile can be determined from a
mathematical model of ion interactions in sample 2130 (e.g., an ion
scattering model).
[0121] In certain embodiments, the information about the expected
ion dose profile can include information about the FWHM of the
Bragg peak in the expected ion dose profile. The FWHM of the Bragg
peak can be determined from measurements of ion dose profiles
and/or from one or more mathematical models of ion scattering in
the sample. Adjustments of the ion energy distribution of ion beam
2150 can be performed to reduce a difference between the thickness
h of sample 2130 and the FWHM of the Bragg peak. In some
embodiments, for example, a difference between h and the full width
at half maximum of the Bragg peak is 20 cm or less (e.g., 18, 16,
14, 12, 10, 8, 6 cm, 5, 4, 3, 2, 1, 0.5, 0.1, 0.05, 0.01, 0.001,
0.0001, or even 0.00001 cm or less, or even zero).
[0122] In some embodiments, the ion beam exposure system can adjust
the distribution of ion energies in ion beam 2150 in other ways.
For example, the ion beam exposure system can be configured to
filter the ion beam by removing ions from ion beam 2150 that have
energies below a selected energy threshold and/or above a selected
energy threshold. FIG. 6 shows an ion beam exposure system 2200
that includes an ion filter 2210 discussed in more detail below.
The other components of system 2200 are similar to the components
of system 2100, and will not be further discussed.
[0123] FIG. 7A shows an ion energy distribution corresponding to
ion beam 2150 produced by ion source 2110. Ion beam 2150, with an
energy distribution as shown in FIG. 7A, enters ion filter 2210
where the energy distribution of ion beam 2150 is adjusted by
filtering out certain ions from the ion beam. For example, in some
embodiments, ion filter 2210 can be configured to remove ions from
ion beam 2150 that have an energy smaller than a selected energy
threshold. In FIG. 7A, the selected energy threshold is the
position E.sub.0 of the peak in the ion energy distribution,
although more generally, any energy threshold can be selected. By
filtering out all (or even just a large fraction of) ions having an
energy less than E.sub.0, the ion energy distribution for ion beam
2150 is as shown in FIG. 7B.
[0124] In contrast, in some embodiments, ion filter 2210 can be
configured to remove ions from ion beam 2150 that have an energy
larger than a selected energy threshold (when ion filter 2210 is
implemented as a hemispherical analyzer, for example). For example,
the selected energy threshold can correspond to the position
E.sub.0 of the peak in the ion energy distribution, although more
generally, any energy threshold can be selected. By removing all
(or even a large fraction of) ions from ion beam 2150 having an
energy more than E.sub.0, the ion energy distribution for ion beam
2150 is as shown in FIG. 7C.
[0125] In certain embodiments, sample 2130 can be exposed directly
to a filtered ion beam 2150. By filtering the ion beam to achieve a
narrower ion energy distribution, for example, the ion dose profile
in sample 2130 is sharper following sample exposure than it would
otherwise have been without filtering ion beam 2150. As a result,
the width of the Bragg peak in sample 2130 is smaller relative to
the Bragg peak width for an unfiltered ion beam. By exposing sample
2130 to a narrower distribution of incident ion energies, more
refined control over the position of ion beam 2150 can be achieved;
this level of ion exposure control can be useful when exposing
various types of delicate sample materials.
[0126] Alternatively, the filtered ion beam can then be passed
through one or more scattering elements and/or other devices to
increase the width of the distribution of ion energies. This
two-step approach to modifying the ion energy distribution--a first
filtering step, followed by a second broadening step--can be used
to produce ion energy distributions that are tailored for specific
applications (e.g., specific to certain ion types and/or certain
materials and/or certain pre-treatment conditions) that may not be
achievable using a simpler one-step energy distribution broadening
procedure.
[0127] As an example, by first filtering ion beam 2150, and then
passing the filtered ion beam through one or more scattering
elements 2170, the shape of the ion energy distribution can be made
more Gaussian than would otherwise be possible using only a
scattering step instead of the two-step procedure.
[0128] Ion filter 2210 can include one or more of a variety of
different devices for removing ions from ion beam 2150. For
example, in some embodiments, ion filter 2210 includes a
hemispherical analyzer and aperture filter. The hemispherical
analyzer includes a magnetic field source that disperses the ions
of ion beam 2150 according to their kinetic energies. The aperture
filter is then positioned in the path of the dispersed ion beam
2150 to permit only ions having a particular range of energies to
pass through the aperture.
[0129] In certain embodiments, other devices can be used to filter
ion beam 2150. For example, absorbing elements (e.g., elements
configured to absorb incident ions having energies smaller than a
selected energy threshold can be used to filter ion beam 2150.
Suitable absorbing elements include metal foils, for example.
[0130] In some embodiments, ion beam 2150 (and in particular, the
Bragg peak in an expected ion dose profile produced following
exposure of sample 2130 to ion beam 2150) can be swept through
sample 2130 to deliver selected radiation doses to various portions
of the sample. In general, the position of the Bragg peak in sample
2130 can be selected by adjusting the average energy of ion beam
2150 (the average energy of ion beam 2150 typically corresponds to
the maximum in the ion energy distribution). Ion source 2110, under
the control of electronic controller 2190, can adjust the average
energy of ion beam 2150 by changing an extraction voltage applied
to accelerate ions in the ion source.
[0131] FIG. 8 is a schematic diagram that shows how the Bragg peak
of an ion dose profile in sample 2130 can be swept through the
sample. As a first step, ion exposure system 2100 is configured to
produce a first ion beam with a selected average ion energy
corresponding to a particular extraction voltage applied in ion
source 2110. When sample 2130 is exposed to the first ion beam, ion
dose profile 2010a results in the sample, with the Bragg peak at
position 2230a. Following exposure, the extraction voltage in ion
source 2110 is adjusted to produce a second ion beam with a
different average ion energy. When sample 2130 is exposed to the
second ion beam, ion dose profile 2010b results in the sample. By
further repeating the adjusting of the extraction voltage in ion
source 2110 to produce additional beams with different average ion
energies (and, therefore, different ion dose profiles, e.g., ion
dose profile 2010c), and exposing sample 2130 to the additional
beams, the Bragg peak of the ion dose profile can be swept through
sample 2130 in the direction shown by arrow 2220, for example. More
generally, however, by changing the extraction voltage in ion
source 2110, the position of the Bragg peak in sample 2130 can be
selected as desired, permitting delivery of large doses to selected
regions of sample 2130 in any sequence.
[0132] In general, other properties of ion beam 2150 can also be
adjusted in addition to, or as an alternative to, adjusting the
average ion energy of the ion beam. For example, in some
embodiments, the divergence angle of ion beam 2150 at the surface
of sample 2130 can be adjusted to control the ion dose profile in
sample 2130. Generally, by increasing the divergence angle of ion
beam 2150 at the surface of sample 2130, the full width at half
maximum of the Bragg peak in sample 2130 can be increased. Thus, in
certain embodiments, the average energy of the ion beam can be
maintained, but the ion dose profile in the material--including the
position of the Bragg peak--can be changed by adjusting the ion
beam's divergence angle.
[0133] The divergence angle can be adjusted automatically or by
operator control by electronic controller 2190. Typically optical
elements 2120 include one or more ion beam steering elements such
as quadrupole and/or octopole deflectors. By adjusting potentials
applied to the various electrodes of such deflectors, the
divergence angle (and the angle of incidence) of ion beam 2150 at
the surface of sample 2130 can be adjusted.
[0134] In some embodiments--unlike in other applications of ion
beams such as surgical intervention--it can be advantageous to use
ion beams with relatively large divergence angles, to ensure that
the Bragg peak positioned in sample 2130 covers a suitable fraction
of the thickness of sample 2130. For example, in certain
embodiments, sample 2130 can be exposed to an ion beam having a
divergence angle of 2 degrees or more (e.g., 5, 10, 15, 20, 30, 40,
or even 50 degrees or more).
[0135] In some embodiments, both an ion beam current of ion beam
2150 and the average ion energy of ion beam 2150 can be adjusted to
deliver a relatively constant dose as a function of thickness h of
sample 2130. For example, if sample 2130 is exposed according to
the sequential ion dose profiles 2010a, 2010b, and 2010c in FIG. 8,
the net ion dose profile in sample 2130 corresponds to the sum of
profiles 2010a-c, which is shown in FIG. 9A. Based on the net ion
dose profile of FIG. 9A, it is evident that certain regions of
sample 2130 receive larger net doses than other regions of sample
2130.
[0136] The differences in net dose can be reduced by adjusting the
ion beam current of ion beam 2150 together with adjustments of the
average ion energy. The ion beam current can be adjusted in ion
source 2110 under the control of electronic controller 2190. For
example, to reduce the difference in the net dose delivered to
sample 2130 when the Bragg peak is swept through sample 2130 in the
direction indicated by arrow 2220 in FIG. 8, the ion beam current
can be successively reduced for each successive reduction in ion
beam energy. Three ion dose profiles, each corresponding to
successive decreases in both average ion energy and ion current in
ion beam 2150, are shown as profiles 2010d-f, respectively, in FIG.
9B. The net ion dose profile in sample 2130 that results from these
three sequential exposures is shown in FIG. 9C. The net ion dose
profile shows significantly reduced variation as a function of
position in sample 2130 relative to the net ion dose profile of
FIG. 9A.
[0137] By carefully controlling the average energy and ion current
of ion beam 2150, variations in net relative ion dose through the
thickness of sample 2130 following exposure of the sample to ion
beam 2150 can be relatively small. For example, a difference
between a maximum net relative ion dose and a minimum net relative
ion dose in sample 2130 following multiple exposures to ion beam
2150 can be 0.2 or less (e.g., 0.15, 0.1, 0.05, 0.04, 0.03, 0.02,
0.01 or even 0.005 or less).
[0138] By controlling the average energy and ion current of ion
beam 2150, each portion of the exposed sample can receive a net
dose of between 0.001 Mrad and 100 Mrad following multiple
exposures to the ion beam (e.g., between 0.005 Mrad and 50 Mrad,
between 0.01 Mrad and 50 Mrad, between 0.05 Mrad and 30 Mrad,
between 0.1 Mrad and 20 Mrad, between 0.5 Mrad and 20 Mrad, or
between 1 Mrad and 10 Mrad).
[0139] In some embodiments, sample 2130 can be exposed to different
types of ions. Sample 2130 can be sequentially exposed to only one
type of ion at a time, or the exposure of sample 2130 can include
exposing sample 2130 to one or more ion beams that include two or
more different types of ions. Different types of ions produce
different ion dose profiles in an exposed material, and, by
exposing a sample to different types of ions, a particular net ion
dose profile in the sample can be realized. FIG. 10A shows a
schematic diagram of three different ion dose profiles 2010g-i that
result from exposing a sample 2130 to three different types of
ions. Ion dose profiles 2010g-i can be produced via sequential
exposure of the sample to each one of the different types of ions,
or via concurrent exposure of the sample to two or even all three
of the different types of ions. The net ion dose profile in sample
2130 that results from exposure to the three different types of
ions is shown in FIG. 10B. Variations in the net ion dose profile
as a function of thickness of the sample are reduced relative to
any one of the individual ion dose profiles shown in FIG. 10A.
[0140] In some embodiments, the different types of ions can include
ions of different atomic composition. For example, the different
types of ions can include protons, carbon ions, oxygen ions,
hydride ions, nitrogen ions, chlorine ions, fluorine ions, argon
ions, neon ions, krypton ions, and various types of metal ions such
as sodium ions, calcium ions, and lithium ions. Generally, any of
these different types of ions can be used to treat sample 2130, and
each will produce a different ion dose profile in a sample. In
certain embodiments, ions can be generated from commonly available
gases such as air. When air is used as a source gas, many different
types of ions can be generated. The various different types of ions
can be separated from one another prior to exposing sample 2130, or
sample 2130 can be exposed to multiple different types of ions
generated from a source gas such as air.
[0141] In some embodiments, the different types of ions can include
ions having different charges. For example, the different types of
ions can include various positive and/or negative ions. Further,
the different types of ions can include ions having single and/or
multiple charges. In general, positive and negative ions of the
same chemical species can produce different ion dose profiles in a
particular sample, and ions of the same chemical species that have
different charge magnitudes (e.g., singly-charged, doubly-charged,
triply-charged, quadruply-charged) can produce different ion dose
profiles in a particular sample. By exposing a sample to multiple
different types of ions, the change in the sample, e.g., sample
breakdown (e.g., depolymerization, chain scission, and/or molecular
weight reduction), functionalization, or other structural change,
can be carefully and selectively controlled.
[0142] In some embodiments, the ion beam exposure system can adjust
the composition of the ion beam based on the sample material. For
example, certain types of sample, such as cellulosic biomass,
include a large concentration of hydroxyl moieties. Accordingly,
the effective penetration depth of certain types of
ions--particularly protons--in such materials can be considerably
larger than would otherwise be expected based on ion energy alone.
Site-to-site proton hopping and other similar atomic excursions can
significantly increase the mobility of such ions in the sample,
effectively increasing the penetration depth of the incident ions.
Further, the increased mobility of the ions in the sample can lead
to a broadening of the Bragg peak. The ion beam exposure system can
be configured to select particular types of ions for exposure of
certain samples, accounting for the chemical and structural
features of the sample. Further, the ion beam exposure system can
be configured to take into account the expected interactions
between the ion beam and the material when determining how to
modify other parameters of the ion beam such as the distribution of
ion energies therein.
[0143] An important aspect of the ion beam systems and methods
disclosed herein is that the disclosed systems and methods enable
exposure of biomass to ions in the presence of one or more
additional fluids (e.g., gases and/or liquids). Typically, for
example, when a material is exposed to an ion beam, the exposure
occurs in a reduced pressure environment such as a vacuum chamber.
The reduced pressure environment is used to reduce or prevent
contamination of the exposed material, and also to reduce or
prevent scattering of the ion beam by gas molecules. Unfortunately,
ion beam exposure of materials in closed environments such as a
vacuum chamber greatly restricts potential throughput for high
volume material processing, however.
[0144] In the systems and methods disclosed herein, it has been
recognized that exposure of biomass to an ion beam in the presence
of one or more additional fluids can increase the efficiency of the
biomass treatment. Additionally, exposure of biomass to an ion beam
in an open environment (e.g., in air at normal atmospheric
pressure) provides for much higher throughput than would otherwise
be possible in a reduced pressure environment.
[0145] As discussed above, in some embodiments, biomass is exposed
to an ion beam in the presence of a fluid such as air. Ions
accelerated in any one or more of the types of accelerators
disclosed herein (or another type of accelerator) are coupled out
of the accelerator via an output port (e.g., a thin membrane such
as a metal foil), pass through a volume of space occupied by the
fluid, and are then incident on the biomass material. In addition
to directly treating the biomass, some of the ions generate
additional chemical species by interacting with fluid particles
(e.g., ions and/or radicals generated from various constituents of
air). These generated chemical species can also interact with the
biomass, and can act as initiators for a variety of different
chemical bond-breaking reactions in the biomass (e.g.,
depolymerization and other chain-scission reactions).
[0146] In certain embodiments, additional fluids can be selectively
introduced into the path of an ion beam before the ion beam is
incident on the biomass. As discussed above, reactions between the
ions and the particles of the introduced fluids can generate
additional chemical species which react with the biomass and can
assist in reducing the molecular weight of the biomass, and/or
otherwise selectively altering certain properties of the biomass.
The one or more additional fluids can be directed into the path of
the ion beam from a supply tube, for example. The direction (i.e.,
fluid vector) and flow rate of the fluid(s) that is/are introduced
can be selected according to a desired exposure rate and/or
direction to control the efficiency of the overall biomass
treatment, including effects that result from both ion-based
treatment and effects that are due to the interaction of
dynamically generated species from the introduced fluid with the
biomass. In addition to air, exemplary fluids that can be
introduced into the ion beam include oxygen, nitrogen, one or more
noble gases, one or more halogens, and hydrogen.
[0147] In some embodiments, ion beams that include more that one
different type of ions can be used to treat biomass. Beams that
include multiple different types of ions can be generated by
combining two or more different beams, each formed of one type of
ion. Alternatively, or in addition, in certain embodiments, ion
beams that include multiple different types of ions can be
generated by introducing a multicomponent supply gas into an ion
source and/or accelerator. For example, a multicomponent gas such
as air can be used to generate an ion beam having different types
of ions, including nitrogen ions, oxygen ions, argon ions, carbon
ions, and other types of ions. Other multicomponent materials
(e.g., gases, liquids, and solids) can be used to generate ion
beams having different compositions. Filtering elements (e.g.,
hemispherical electrostatic filters) can be used to filter out
certain ionic constituents and/or neutral species to selectively
produce an ion beam having a particular composition, which can then
be used to treat biomass. By using air as a source for producing
ion beams for biomass treatment, the operating costs of a treatment
system can be reduced relative to systems that rely on pure
materials, for example.
[0148] Certain types of biomass materials may be particularly
amenable to treatment with multiple different types of ions and/or
multiple different processing methods. For example, cellulosic
materials typically include crystalline polymeric cellulose chains
which are cross-linked by amorphous hemicellulose fraction. The
cellulose and hemicellulose is embedded within an amorphous lignin
matrix. Separation of the cellulose fraction from the lignin and
the hemicellulose using conventional methods is difficult and can
be energy-intensive.
[0149] However, cellulosic biomass can be treated with multiple
different types of ions to break down and separate the various
components therein for further processing. In particular, the
chemical properties of various types of ionic species can be used
to process cellulosic biomass (and other types of biomass) to
selectively degrade and separate the components thereof. For
example, positively charged ions--and in particular, protons--act
as acids when exposed to biomass material. Conversely, negatively
charged ions, particularly hydride ions, act as bases when exposed
to biomass material. As a result, the chemical properties of these
species can be used to target specific components of treated
biomass.
[0150] When treating lignocellulosic biomass, for example, the
lignin matrix typically decomposes in the presence of basic
reagents. Accordingly, by first treating cellulosic biomass with
basic ions such as hydride ions (or electrons) from an ion
(electron) beam, the lignin fraction can be preferentially degraded
and separated from the cellulose and hemicellulose fractions.
Cellulose is relatively unaffected by such an ion treatment, as
cellulose is typically stable in the presence of basic agents.
[0151] In addition to negative ion treatment (or as an alternative
to negative ion treatment), the lignocellulosic biomass can be
treated with one or more basic agents in solution to assist in
separating the lignin. For example, treatment of the
lignocellulosic biomass with a sodium bicarbonate solution can
degrade and/or solubilize the lignin, enabling separation of the
solvated and/or suspended lignin from the cellulose and
hemicellulose fractions.
[0152] Negative ion treatment with an ion beam may also assist in
separating hemicellulose, which is also chemically sensitive to
basic reagents. Depending upon the particular structure of the
cellulosic biomass, more than treatment with negative ions may be
used (and/or may be necessary) to effectively separate the
hemicellulose fraction from the cellulose fraction. In addition,
more that one type of ion can be used to separate the
hemicellulose. For example, a relatively less basic ion beam such
as an oxygen ion beam can be used to treat cellulosic biomass to
degrade and/or remove the lignin fraction. Then, a stronger basic
ion beam such as a hydride ion beam can be used to degrade and
separate the hemicellulose from the cellulose. The cellulosic
fraction remains largely unchanged as a result of exposure to two
different types of basic ions.
[0153] However, the cellulose fraction decomposes in the presence
of acidic agents. Accordingly, a further processing step can
include exposing the cellulose fraction to one or more acidic ions
such as protons from an ion beam, to assist in depolymerizing
and/or degrading the cellulose fraction.
[0154] Each of the ion beam pretreatments and methods disclosed
herein can be used in combination with other processing steps. For
example, separation steps (including introducing a solvent such as
water) can be used to wash away particular fractions of the
cellulosic biomass as they are degraded. Additional chemical agents
can be added to assist in separating the various components. For
example, it has been observed that lignin that is separated from
the cellulose and hemicellulose fractions can be suspended in a
washing solution. However, the lignin can readily re-deposit from
the solution onto the cellulose and hemicellulose fractions. To
avoid re-deposition of the lignin, the suspension can be gently
heated to ensure that the lignin remains below its glass transition
temperature, and therefore remains fluid. By maintaining the lignin
below its glass transition temperature, the lignin can be more
readily washed out of cellulosic biomass. In general, heating of
the suspension is carefully controlled to avoid thermal degradation
of the sugars in the cellulosic fraction.
[0155] In addition, other treatment steps can be used to remove
lignin from cellulose and hemicellulose. For example, in certain
embodiments, lignocellulosic biomass can first be treated with
relatively heavy ions (e.g., carbon ions, oxygen ions) to degrade
lignin, and the cellulose and hemicellulose can then be treated
with relatively light ions (e.g., protons, helium ions) and/or
electrons to cause degradation of the cellulose and/or
hemicellulose.
[0156] In some embodiments, one or more functionalizing agents can
be added to the suspension containing the lignin to enhance the
solubility of lignin in solution, thereby discouraging
re-deposition on the cellulose and hemicellulose fractions. For
example, agents such as ammonia gas and/or various types of
alcohols can be used (to introduce amino and hydroxyl/alkoxy
groups, respectively) to functionalize the lignin.
[0157] In certain embodiments, structural agents can be added to
the lignin suspension to prevent re-deposition of the lignin onto
the cellulose and hemicellulose fractions. Typically, when lignin
forms a matrix surrounding cellulose and/or hemicellulose, the
lignin adopts a heavily folded structure which permits relatively
extensive van der Waals interactions with cellulose and
hemicellulose. In contrast, when lignin is separated from cellulose
and hemicellulose, the lignin adopts a more open, unfolded
structure. By adding one or more agents that assist in preventing
lignin re-folding to the lignin suspension, re-association of the
lignin with cellulose and hemicellulose can be discouraged, and the
lignin can be more effectively removed via washing, for
example.
[0158] In some embodiments, no chemicals, e.g., no swelling agents,
are added to the biomass prior to irradiation. For example,
alkaline substances (such as sodium hydroxide, potassium hydroxide,
lithium hydroxide and ammonium hydroxides), acidifying agents (such
as mineral acids (e.g., sulfuric acid, hydrochloric acid and
phosphoric acid)), salts, such as zinc chloride, calcium carbonate,
sodium carbonate, benzyltrimethylammonium sulfate, or basic organic
amines, such as ethylene diamine, may or may not be added prior to
irradiation or other processing. In some cases, no additional water
is added. For example, the biomass prior to processing can have
less than 0.5 percent by weight added chemicals, e.g., less than
0.4, 0.25, 0.15 or 0.1 percent by weight added chemicals. In some
instances, the biomass has no more than a trace, e.g., less than
0.05 percent by weight added chemicals, prior to irradiation. In
other instances, the biomass prior to irradiation has substantially
no added chemicals or swelling agents. Avoiding the use of such
chemicals can also be extended throughout processing, e.g., at all
times prior to fermentation, or at all times.
[0159] The various ion beam pretreatment methods disclosed herein
can be used cooperatively with other pretreatment techniques such
as sonication, electron beam irradiation, electromagnetic
irradiation, steam explosion, chemical methods, and biological
methods. Ion beam techniques provide significant advantages,
including the ability to perform ion beam exposure of dry samples,
to deliver large radiation doses to samples in short periods of
time for high throughput applications, and to exercise relatively
precise control over exposure conditions.
[0160] Quenching and Controlled Functionalization
[0161] After treatment with ionizing radiation, the materials
described herein become ionized; that is, they include radicals at
levels that are detectable with an electron spin resonance
spectrometer. The current practical limit of detection of the
radicals is about 10.sup.14 spins at room temperature. After
ionization, any material that has been ionized can be quenched to
reduce the level of radicals in the ionized material, e.g., such
that the radicals are no longer detectable with the electron spin
resonance spectrometer. For example, the radicals can be quenched
by the application of a sufficient pressure to the material and/or
by utilizing a fluid in contact with the ionized material, such as
a gas or liquid, that reacts with (quenches) the radicals. The use
of a gas or liquid to at least aid in the quenching of the radicals
also allows the operator to control functionalization of the
ionized material with a desired amount and kind of functional
groups, such as carboxylic acid groups, enol groups, aldehyde
groups, nitro groups, nitrile groups, amino groups, alkyl amino
groups, alkyl groups, chloroalkyl groups or chlorofluoroalkyl
groups. In some instances, such quenching can improve the stability
of some of the ionized materials. For example, quenching can
improve the resistance of the material to oxidation.
Functionalization by quenching can also improve the solubility of
the materials described herein, can improve the thermal stability
of a material, and can improve material utilization by various
microorganisms. For example, the functional groups imparted to a
biomass material by quenching can act as receptor sites for
attachment by microorganisms, e.g., to enhance cellulose hydrolysis
by various microorganisms.
[0162] Thus, a molecular and/or a supramolecular structure of a
feedstock can be changed by pretreating the feedstock with ionizing
radiation, such as with electrons or ions of sufficient energy to
ionize the feedstock, to provide a first level of radicals. If an
ionized feedstock remains in the atmosphere, it will be oxidized,
for example causing carboxylic acid groups to be generated by
reacting with the atmospheric oxygen. In some instances with some
materials, such oxidation is desired because it can aid in further
breakdown in molecular weight, for example of a
carbohydrate-containing biomass, and the oxidation groups, e.g.,
carboxylic acid groups, can be helpful for solubility and
microorganism utilization. However, since the radicals can "live"
for some time after irradiation, e.g., longer than 1 day, 5 days,
30 days, 3 months, 6 months or even longer than 1 year, material
properties can continue to change over time, which in some
instances, can be undesirable. Detecting radicals in irradiated
samples by electron spin resonance spectroscopy and radical
lifetimes in such samples is discussed in Bartolotta et al.,
Physics in Medicine and Biology, 46 (2001), 461-471 and in
Bartolotta et al., Radiation Protection Dosimetry, Vol. 84, Nos.
1-4, pp. 293-296 (1999). The ionized material can be quenched to
functionalize and/or to stabilize it. At any point, e.g., when the
material is "alive", "partially alive" or fully quenched, the
material can be converted into a product, e.g., a fuel, a food, or
a composite.
[0163] In some embodiments, the quenching includes an application
of pressure, such as by mechanically deforming the material, e.g.,
directly mechanically compressing the material in one, two, or
three dimensions, or applying pressure to a fluid in which the
material is immersed, e.g., isostatic pressing. In such instances,
the deformation of the material itself brings radicals, which are
often trapped in crystalline domains, in sufficient proximity so
that the radicals can recombine, or react with another group. In
some instances, the pressure is applied together with the
application of heat, such as a sufficient quantity of heat to
elevate the temperature of the material to above a melting point or
softening point of a component of the material, such as lignin,
cellulose or hemicellulose in the case of a biomass material. Heat
can improve molecular mobility in the material, which can aid in
the quenching of the radicals. When pressure is utilized to quench,
the pressure can be greater than about 1000 psi, such as greater
than about 1250 psi, 1450 psi, 3625 psi, 5075 psi, 7250 psi, 10000
psi or even greater than 15000 psi.
[0164] In some embodiments, quenching includes contacting the
material with a fluid, such as a liquid or gas, e.g., a gas capable
of reacting with the radicals, such as acetylene or a mixture of
acetylene in nitrogen, ethylene, chlorinated ethylenes or
chlorofluoroethylenes, propylene or mixtures of these gases. In
other particular embodiments, quenching includes contacting the
material, e.g., biomass, with a liquid, e.g., a liquid soluble in,
or at least capable of penetrating into the biomass and reacting
with the radicals, such as a diene, such as 1,5-cyclooctadiene. In
some specific embodiments, the quenching includes contacting the
biomass with an antioxidant, such as Vitamin E. If desired, the
feedstock can include an antioxidant dispersed therein, and the
quenching can come from contacting the antioxidant dispersed in the
feedstock with the radicals.
[0165] Other methods for quenching are possible. For example, any
method for quenching radicals in polymeric materials described in
Muratoglu et al., U.S. Patent Application Publication No.
2008/0067724 and Muratoglu et al., U.S. Pat. No. 7,166,650, can be
utilized for quenching any ionized material described herein.
Furthermore any quenching agent (described as a "sensitizing agent"
in the above-noted Muratoglu disclosures) and/or any antioxidant
described in either Muratoglu reference can be utilized to quench
any ionized material.
[0166] Functionalization can be enhanced by utilizing heavy charged
ions, such as any of the heavier ions described herein. For
example, if it is desired to enhance oxidation, charged oxygen ions
can be utilized for the irradiation. If nitrogen functional groups
are desired, nitrogen ions or ions that includes nitrogen can be
utilized. Likewise, if sulfur or phosphorus groups are desired,
sulfur or phosphorus ions can be used in the irradiation.
[0167] In some embodiments, after quenching any of the quenched
materials described herein can be further treated with one or more
of radiation, such as ionizing or non-ionizing radiation,
sonication, pyrolysis, and oxidation for additional molecular
and/or supramolecular structure change.
[0168] In particular embodiments, functionalized materials
described herein are treated with an acid, base, nucleophile or
Lewis acid for additional molecular and/or supramolecular structure
change, such as additional molecular weight breakdown. Examples of
acids include organic acids, such as acetic acid and mineral acids,
such as hydrochloric, sulfuric and/or nitric acid. Examples of
bases include strong mineral bases, such as a source of hydroxide
ion, basic ions, such as fluoride ion, or weaker organic bases,
such as amines. Even water and sodium bicarbonate, e.g., when
dissolved in water, can effect molecular and/or supramolecular
structure change, such as additional molecular weight
breakdown.
[0169] The functionalized materials can be used as substrate
materials to immobilize microorganisms and/or enzymes during
bioprocessing, for example as described in U.S. Provisional
Application Ser. Nos. 61/180,032 and 61/180,019, the disclosures of
which are incorporated herein by reference.
[0170] Other embodiments are within the scope of the following
claims. For example, non-biomass materials and mixtures of biomass
materials and non-biomass materials can be processed using the
methods described herein. Examples of non-biomass materials that
can be processed include hydrocarbon-containing materials such as
oil sands, oil shale, tar sands, bitumen, coal, and other such
mixtures of hydrocarbons and non-hydrocarbon materials. Many other
biomass and non-biomass materials can be processed using the
methods described herein, including peat, lignin, pre-coal, and
petrified and/or carbonized materials.
* * * * *