US20100223839A1

US20100223839A1 - Systems and processes for producing bio-fuels from lignocellulosic materials

Info

Publication number: US20100223839A1
Application number: US12/717,833
Authority: US
Inventors: Manuel Garcia-Perez; Robert L. Johnson; Shi-Shen Liaw; Shulin Chen; Jieni Lian; Shuai Zhou; Oisik Das; Zhouhong Wang
Original assignee: Washington State University WSU
Current assignee: Washington State University WSU
Priority date: 2009-03-04
Filing date: 2010-03-04
Publication date: 2010-09-09
Also published as: WO2010102145A1

Abstract

A selective pyrolysis process for the production of bio-oils enriched in pyrolytic sugars and phenols and conversion of these compounds into second generation bio-fuels is disclosed herein. One embodiment of the process comprises pre-treating a biomass with superheated steam or gases in a selected range of temperatures, followed by fast pyrolysis using synthesis gas as a carrier, and a two-step condensation operation. The aqueous phase from the second condenser can then be reformed to produce hydrogen or can be gasified together with the charcoal to produce syngas.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 61/157,338, filed on Mar. 4, 2009, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to systems and processes for producing liquid fuels from lignocellulosic materials (e.g., agricultural and forestry residues and energy crops).

BACKGROUND

Biomass is an attractive feedstock to offset fossil fuels because it is carbon neutral (or negative), renewable, and may be domestically produced. One conversion platform uses a thermo-chemical process (commonly referred to as “pyrolysis”) to convert biomass into bio-oil. Bio-oils are similar in appearance and color as crude oil though bio-oil contains considerably more oxygenated and functional compounds.
Although bio-oil can be used directly for stationary diesel engines, bio-oil may be too corrosive and viscous as a transport fuel. There is however great potential to use bio-oil as a feedstock for centralized refineries to produce chemical products and/or transportation fuels. However, several technical challenges exist for the utilization of bio-oil as a feedstock. First, bio-oils are highly acidic and may be corrosive to pipes and storage vessels. Secondly, bio-oils can be unstable when stored for prolonged periods of time. Third, bio-oils typically contain a wide variety of molecules including a substantial amount of small molecules, which are difficult to upgrade. Accordingly, several improvements in converting biomass to bio-oils are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram illustrating a system for converting biomass into bio-oils in accordance with embodiments of the technology.

FIG. 2 is a schematic diagram illustrating a system for performing bio-oil refining in accordance with embodiments of the technology.

FIGS. 3A and 3B are schematic diagrams illustrating a reactor in accordance with embodiments of the technology.

FIG. 4 is a graph showing ratios of peaks in Py-GC/MS chromatogram assigned to levoglucosan and to hydroxyacetaldehyde in accordance with embodiments of the technology.

FIG. 5 shows the changes of levoglucosan/furfural ratios as a function of pyrolysis temperature in accordance with embodiments of the technology.

FIGS. 6 and 7 show the ratio of levoglucosan and other products of oxidation reactions in accordance with embodiments of the technology.

FIG. 8 shows levoglucosan/2-methoxy phenol ratios as a function of pretreatment temperature in accordance with embodiments of the technology.

FIG. 9 shows levoglucosan/hydroxyacetaldehyde ratios as a function of pyrolysis temperature in accordance with embodiments of the technology.

FIG. 10 shows a glucose content as a function of fermentation time in accordance with embodiments of the technology.

FIG. 11 shows a rate of microbial growth in solutions derived from bio-oils and in control solutions produced with glucose in accordance with embodiments of the technology.

FIG. 12 shows ethanol concentration as a function of fermentation time in accordance with embodiments of the technology.

FIG. 13 shows sugar consumption and production of fatty acids as a function of fermentation time in accordance with embodiments of the technology.

DETAILED DESCRIPTION

Specific details of several embodiments of the disclosure are described below with reference to systems and processes to selectively convert lignocellulosic materials into a bio-oil that is rich in anhydrosugars (e.g., levoglucosan and cellobiosan) and phenols as well as the further conversion of the anhydrosugars to ethanol and/or lipids. The term “lignocellulosic materials” generally refers to materials containing cellulose, hemicelluloses, and lignin. Examples of lignocellulosic materials include wood chips, straws, grasses, corn stover, corn husks, weeds, aquatic plants, hay, paper, paper products, recycled paper and/or paper products, and other cellulose containing biological materials or materials of biological origin. Several embodiments can have configurations, components, or procedures different than those described in this section, and other embodiments may eliminate particular components or procedures. A person of ordinary skill in the relevant art, therefore, may understand that the technology may have other embodiments with additional elements, and/or may have other embodiments without several of the features shown and described below with reference to FIGS. 1-13.
FIG. 1 is a schematic flow diagram illustrating a system 100 for converting biomass into bio-oils in accordance with embodiments of the disclosure. As shown in FIG. 1, the system 100 includes a drier 102, a torrefaction unit (with an optional grinder) 104, a pyrolysis reactor 106, a first condenser 108, a second condenser 110, and a combustor 112 operatively coupled in series. The system 100 also includes an evaporator 114, a steam reformer 116, and a gasification reactor 118 operatively coupled to one another as well as to the pyrolysis reactor 106 and the second condenser 110. Even though only particular components are shown in FIG. 1, other embodiments of the system 100 can also include washers, decanters, filters, and/or other suitable components in addition to or in lieu of the foregoing components of the system 100.
The dryer 102 can include a direct-contact dryer, an indirect-contact dryer, and/or other suitable types of dryer. In the illustrated embodiment, the dryer 102 includes a direct-contact dryer configured to receive and contact the biomass 1 with a hot combustion gas 6 from the combustor 112. The exhaust from the dryer 102 is vented to atmosphere. In other embodiments, the dryer 102 can also be coupled to an optional hot gas source (e.g., hot air, not shown) for start-up, supplementing the hot combustion gas 6, and/or other suitable purposes. After drying, the dryer 102 provides a dried biomass 2 to the torrefaction unit 104. In further embodiments, the dryer 102 and the torrefaction unit 104 can be integrated in a single unit (not shown).
The torrefaction unit 104 can be configured to pre-treat the dried biomass 2 before subjecting the dried biomass 2 to pyrolysis. The torrefaction unit 104 can include any vessel capable of controllably heating the dried biomass 2 to a desired temperature. Optionally, the torrefaction unit 104 can also include a grinder and/or other suitable components to reduce the size of the dried biomass 2. For example, in one embodiment, the torrefaction unit 104 can include an auger reactor configured to controllably heat the dried biomass 2 while reducing the size of the dried biomass 2, as described in more detail below with reference to FIG. 4. In other embodiments, the torrefaction unit 104 may also use a synthesis gas 16 from the reformer 116 as a carrier gas for the pretreatment reactions.
The pyrolysis reactor 106 can include a fluidized bed, a fixed bed, an ablative reactor, vacuum pyrolysis reactor, auger pyrolysis reactor, and/or other suitable types of pyrolysis reactors. In one embodiment, the pyrolysis reactor 106 can include embodiments of the auger reactor shown in FIG. 3. In other embodiments, the pyrolysis reactor 106 can include other types of reaction vessels. Even though the torrefaction unit 104 and the pyrolysis reactor 106 are shown as separate components in FIG. 1, in certain embodiments, the torrefaction unit 104 and the pyrolysis reactor 106 can be combined into a single component. In further embodiments, a single component (e.g., the reactor of FIG. 3) may perform the function of both the torrefaction unit 104 and the pyrolysis reactor 106. As a result, the torrefaction unit 104 and the pyrolysis reactor 106 may be integrated into a single unit.
The first and second condensers 108 and 110, the boiler 114, and the reformer 116 can individually include a plate-and-frame, tube-and-shell, brazed aluminum, and/or other types of heat exchanger. In one embodiment, the first condenser 108 can be an empty scrubber. In other embodiments, the first condenser 108 can operate in other suitable fashion. Even though the first and second condensers 108 and 110 are shown as separate components in FIG. 1, in certain embodiments, the first and second condensers 108 and 110 may be combined into a single heat exchanger. In further embodiments, one of the first and second heat exchangers 108 and 110 may be omitted.
The combustor 112 can be configured to react a combustible gas with air and/or oxygen to produce electrical, heat, and/or other forms of energy. In the illustrated embodiment, the combustor 112 includes a gas turbine coupled to an electrical generator. In other embodiments, the combustor 112 can also include a gasoline engine, a diesel engine, a ramjet, and/or other suitable combustion components. In further embodiments, the combustor 112 may be omitted.
The gasification reactor 118 can be configured to convert a carbonaceous material into a combination of hydrogen, carbon monoxide, carbon dioxide, and/or other suitable gaseous components. The gasification reactor 118 can include a counter-current fixed bed gasifier, a co-current fixed bed gasifier, a fluidized bed reactor, an entrained flow gasifier, and/or other suitable types of gasifier.
In operation, the biomass 1 is provided to drier 102. The drier 102 dries the biomass 1 with, for example, the combustion gas 6 from the combustor 112. The dried biomass 2 then enters the torrefaction unit 104 to be pre-treated prior to pyrolysis. In certain embodiments, the torrefaction unit 104 heats the dried biomass 2 to a desired temperature (e.g., about 200° C. to about 300° C.) for a treatment period (e.g., 3 min to about 10 hours) with a portion of the synthetic gas 15 from the reformer 116 as a carrier gas.
The pre-treatment temperature and time may depend on each other. For example, a high pre-treatment temperature may require a short treatment time and vice versa. Without being bound by theory, it is believed that pre-treating the biomass 1 in the torrefaction unit 104 can (1) remove at least part of the hemicellulose and acetic acid from the solid matrix; (2) reduce the degree of polymerization of cellulose and increase crystallinity of the cellulose; (3) de-polymerize at least part of the lignin; and (4) weaken biomass fibrous structure for ease of grinding.
The pre-treated biomass is then provided to the pyrolysis reactor 106 in which the biomass is thermally converted at temperatures between 400 and 500° C. into a vapor phase pyrolysis product 3 and bio-char 8. In certain embodiments, the pre-treated biomass provided to the pyrolysis reactor 106 may contain additives (e.g., H₂SO₄, (NH₄)₂HPO₄and (NH₄)₂SO₄) at concentrations of about 0.1 mass % or other suitable concentration values. The additional of such additives are believed to enhance the production of anhydrosugars from biomass. In other embodiments, the pyrolysis reactor 106 may contain other suitable compositions.
In the illustrated embodiment, the first and second condensers 108 and 110 may then condense the pyrolysis product 3 with ambient air 17 (and/or other suitable coolant) to separate and collect different fractions from the pyrolysis product 3 and produce heated air streams 18 and 19, which is provided to the combustor 112. In other embodiments, the first and second condensers 108 and 110 may both cool the pyrolysis product 3 with ambient air.
The temperature in the first condenser 108 can be controlled to separate heavier compounds (e.g., phenols and sugars) from light compounds (e.g., acetic and formic acid). A bio-oil 9 can be separated via solvent extraction (e.g., with ethyl acetate) and/or other suitable techniques to produce a stream rich in phenols and pyrolytic sugars. A first fraction of the bio-oil 9, which is rich in sugar can then be hydrolyzed, detoxified and fermented to produce ethanol and/or can be subject to other types of suitable processing to produce other hydrocarbons. A second fraction of the bio-oil 9, which is rich in phenols can be converted into green gasoline via hydro-treatment and/or other suitable processes, as described in more detail below with reference to FIG. 2.
The second condenser 110 can then receive an output stream 4 from the first condenser 106 and collect an aqueous stream 10 from the pyrolysis product 3. The aqueous stream 10 is then supplied to the reformer 116 via the boiler 114 to produce a synthetic gas 20. The synthetic gas 20 is then provided to the combustor 112 for conversion into electricity and/or other forms of energy. Optionally, the aqueous stream 10 can be gasified with the bio-char 8. The gasification reactor 118 can convert at least a portion of the bio-char 8 into a synthetic gas 14 provided to the reformer 116 and output the rest of the bio-char 8 as char and ash. In other embodiments, the bio-char 8 may be provided to the combustor 112 and/or otherwise processed. In further embodiments, the bio-char 8 may form a final product of the process.
Several embodiments of the technology utilize pretreatment with specific temperatures to produce the bio-oil 9 that is more enriched in sugars, less corrosive, more stable than conventional bio-oils. Without being bound by theory, it is believed that biomass degradation via pyrolysis may be classified into three general categories: de-polymerization, fragmentation, and polycondensation. Depolymerization reactions are believed to yield primarily monomers that are greater than five carbons. Such monomers may be either carbohydrodrate (from cellulose/hemicellulose) or aromatic (from lignin). Fragmentation reactions are believed to lead to the formation of small molecules that are typically smaller than five carbons. Poly-condensation reactions are believed to result in the formation of charcoal. Pyrolysis reactors can reduce the formation of char by having very high heating rates which may reduce the time the material is in the temperature range of 270-350° C. in which dehydratation and crosslinking reactions are favored.
Several embodiments of the system 100 can alter the structural properties of the biomass 1 for improving the selectivity to favor depolymerization reactions and improve the bio-oil quality produced during pyrolysis. Several factors are believed to influence whether degradation proceeds via fragmentation or de-polymerization reactions. The presence of alkaline is believed to strongly catalyze fragmentation reactions. Other factors such as degree of polymerization, crystallinity, and the interactions lignin/cellulose are also factors that can be adjusted to improve reaction selectivity toward de-polymerization (formation of precursors of transportation fuels). Thus, by increasing the crystallinity and reducing the degree of polymerization via heating in the temperature range of about 200° C. to about 300° C. (in the presence or absence of steam), the reaction selectivity to de-polymerization may be improved.
Several embodiments of the systems and processes can also have substantial energy savings as a result of pretreatment for grinding operations. The pretreatment not only removes components of the material, it may also attenuate the physical integrity and reduce the energy required to reduce particle sizes to what is required for the pyrolysis reactor. It should be noted that grinding can contribute to as much as 10% of the total energy in the biomass.
FIG. 2 is a schematic diagram illustrating a process 200 for performing bio-oil refining in accordance with embodiments of the disclosure. As shown in FIG. 2, the process 200 can include separating a phenolic fraction from an aqueous fraction in the bio-oil 9. Techniques suitable for this separation can include liquid-liquid extraction with water, an organic solvent, and/or other suitable materials. The phenolic fraction can then be hydro-treated with hydrogen to produce green gasoline. The aqueous fraction can be (1) hydro-treated under high pressure to produce green diesel; (2) hydrolyzed, neutralized, and detoxified to produce lipids; and/or (3) hydrolyzed, neutralized, detoxified, and fermented to produce alcohol.
FIG. 3A is a schematic diagram illustrating an reactor 300 in accordance with embodiments of the technology. As shown in FIG. 3A, the reactor 300 includes a feeder 302 coupled to a treatment zone 304 having a first end 303 a and a second end 303 b. The feeder 302 can include a screw pump and/or other suitable material moving components. The treatment zone 30 can include a generally helical auger (or screw) 307 and/or other suitable structures inside a housing 305 and a motor 320 operatively coupled to the auger 320.
The reactor 300 also includes a heat exchanger 306 and a furnace 308 on the housing 305 and a power supply/controller 310 operatively coupled to the furnace 308. The reactor 300 further includes a solid container 312 and a condenser 314 proximate to the second end 303 b of the treatment zone 304. Optionally, the reactor 300 includes a plurality of cooling traps 316 coupled to the condenser 314 for collecting condensed materials.
In operation, the feeder 302 forces biomass (shown as separate spheres in FIG. 3A for illustration purposes) to enter the treatment zone 304 via the first end 303 a along with an optional carrier gas. The heat exchanger 306 and the furnace 308 then heats the biomass to a desired temperature while the auger 307 moves the biomass toward the second end 303 b and reduces the size of the biomass. Solid portions of the biomass are then collected at the solid container 312 while volatile portions are collected at the condenser 314 and/or the cooling traps 316.
A single reactor 300 may be used for both pre-treating and pyrolysis of the biomass. For example, the biomass may be processed in the reactor 300 at a first temperature (e.g., about 200° C. to about 300° C.). The collected solid portions may then be returned to the feeder 302 to be provided to the auger 304 and processed at a second temperature (e.g., about 500° C. to about 600° C.).
In other embodiments, as shown in FIG. 3B, the reactor 300 may include more than one treatment zones (e.g., by having more than one furnaces) such that the pre-treatment and pyrolysis operations may be performed in a continuous fashion. Several components shown in FIG. 3B are generally similar in structure and function as those shown in FIG. 3A. As a result, common acts and structures are identified by the same reference numbers.
As shown in FIG. 3B, the reactor 300 can include a first treatment zone 304 a coupled to a second treatment zone 304 b. The first treatment zone 304 a can include a first auger (or screw) 307 a inside a first housing 305 a having a first end 303 a and a second end 303 b. The first auger 307 a can be operatively coupled to a first motor 320 a. The first treatment zone 304 a also includes a first furnace 308 a proximate to the first housing 305 a and operatively coupled to a first power supply/controller 310 a. The first treatment zone 304 a also includes a carrier gas inlet 324 a and a carrier gas outlet 324 b in fluid communication with the auger 307 a.
Optionally, the first treatment zone 304 a can also include a grinder 322 and/or other suitable components configured to reduce a physical size of the biomass in the first treatment zone 304 a. In the illustrated embodiment, the grinder 322 is proximate to the second end 303 b of the first treatment zone. In other embodiments, the grinder 322 may be at other locations of the first treatment zone or may be omitted.
The second treatment zone 304 b can have generally similar components as the first treatment zone 304 a. For example, the second treatment zone 304 b can include a second auger 307 b in a second housing 305 b and operatively coupled to a second motor 320 b. The second treatment zone 304 b can also include a second furnace 308 b proximate to the second housing 305 b and operatively coupled to a second power supply/controller 310 b.
In operation, the feeder 302 forces biomass to enter the first treatment zone 304 a via the first end 303 a along with an optional carrier gas via the carrier inlet 324 a. The heat exchanger 306 and the first furnace 308 a then heats the biomass to a first temperature (e.g., about 200° C. to about 300° C.) while the auger 307 moves the biomass toward the second end 303 b. The optional grinder 322 can then reduce the biomass from the first treatment zone 304 a to particle sizes less than about 2 mm before the biomass is provided to the second treatment zone 304 b. The second furnace 308 b can then heat the biomass to a second temperature (e.g., about 500° C. to about 600° C.) to thermally convert the biomass via pyrolysis. Solid portions of the biomass are then collected at the solid container 312 while volatile portions are collected at the condenser 314 and/or the cooling traps 316.
Even though embodiments of the reactor 300 are shown in FIGS. 3A and 3B as being carried by a cart, in other embodiments, various components of the reactor 300 may be separately and/or fixedly installed. In other embodiments, the reactor 300 may utilize other components for conveying and/or reducing size of the biomass. For example, in certain embodiments, at least one of the first and second augers 307 a and 307 b may be omitted in the reactor 300 shown in FIG. 3B. Instead, the reactor 300 may carry the biomass through the treatment zones 304 a and 304 b pneumatically, hydraulically, and/or via other suitable means. In further embodiments, the biomass may be treated in at least one of the first and second treatment zones 304 a and 304 b in a batch mode. In yet further embodiments, the reactor 300 can include three, four, and/or other suitable number of treatment zones with similar or different configurations.

EXAMPLES

Tests were conducted to understand the effect of torrefaction conditions (temperature and presence of oxygen) and pyrolysis temperatures on the selectivity of pyrolysis reactions towards the production of anhydrosugars were carried out in our Py-GC/MS. The pretreatment was performed at temperatures ranging from 200 to 320° C. Pyrolysis tests were conducted at temperatures between 350 and 550° C. The tests were carried out with Avicel (crystalline cellulose with low degree of polymerization), α-cellulose (a blend of cellulose and hemicellulose), wheat straw and the woody fraction of Douglas Fir (containing cellulose, hemicelluloses and lignin). Before conducting the Py-GC/MS studies, the alkalines in all the samples were removed with hot water (at 120° C.).
The Py-GC/MS tests were carried using a CDS pyro-probe 5000 connected in-line to an Agilent GC/MS. Samples were loaded into a quartz tube and gently packed with quartz wool prior to pyrolysis. The samples were kept for 3 minutes at the pretreatment temperature before the oven temperature was reduced to 210° C. The samples were kept in these conditions for 1 minute. Samples were pyrolysed by near instantaneous heating to the final temperature and held at this temperature for 3 minutes.
The GC/MS inlet temperature was maintained at 250° C. and the resulting pyrolysis vapors were separated by means of a 30 m×0.25 μm inner diameter column. The column was heated at 3° C./min from 40 to 280° C. The gas was then sent into a mass spectrometer and the spectra of the most important peaks were compared to an NBS mass spectra library to establish the identity of each compound.
FIG. 4 shows the ratio of the area of the peaks in the Py-GC/MS chromatogram assigned to levoglucosan (a product of cellulose depolymerization reactions) and to hydroxyacetaldehyde (a product of cellulose fragmentation reactions). This ratio can be used as an index of the selectivity of thermochemical reactions towards the production of anhydrosugars. FIG. 4 shows that a mild torrefaction in the range of temperature between 200 and 320° C. can enhance the production of levoglucosan for α-cellulose, wheat straw and the wood fraction of Douglas Fir.
The presence of oxygen during torrefaction had a positive effect on wheat straw. For all the other biomasses, the presence of oxygen during pretreatment is detrimental to the yield of sugar obtained. In the case of Wheat Straw the highest selectivity towards the production of anhydrosugars was obtained for samples pretreated at temperature over 270° C. in the presence of oxygen. For Douglas Fir the best results were achieved for samples pretreated in the absence of oxygen at temperatures over 230° C. It is noteworthy that a drastic increase in the selectivity towards the production of levoglucosan was also observed when the Douglas Fir wood was heated in the presence of oxygen at temperatures over 310° C.
FIG. 5 shows the changes of levoglucosan/furfural ratios as a function of pyrolysis temperature in accordance with embodiments of the technology. The pretreatment temperature does not have any effect on the Levoglucosan/furfural ratios for the Avicel. This result suggests that Avicel was not dehydrated in the pretreatment conditions tested. In the case of α-cellulose, an increase in the levoglucosan/furfural ratio was observed as the pretreatment temperature increases. The presence of oxygen during pretreatment of α-cellulose and Avicel causes a reduction in the levogluocan/Furfural ratio for most of the materials but not for the wheat straw. The conditions improving the ratio levoglucosan/furfural are very similar to those improving the ratio levoglucosan/hydroxyacetaldehyde.
FIGS. 6 and 7 show the ratio of levoglucosan and other products of oxidation reactions in accordance with embodiments of the technology. With the exception of wheat straw, the shapes of the curves describing the evolution of the levoglucosan/carbon dioxide and levoglucosan/acetic acid ratio are similar to those shown in FIGS. 4 and 5. For the wheat straw there is a maximum for samples pretreated in the presence of oxygen. This maximum could indicate the temperature at which oxidation reactions responsible for the formation of CO₂and acetic acid accelerate.
FIG. 8 shows levoglucosan/2-methoxy phenol ratios as a function of pretreatment temperature. The conditions improving this ratio were similar to those improving the levoglucosan/CO2 and levoglucosan/acetic acid ratios. But, pre-treating biomass in the presence of oxygen considerably increases the production of mono-phenols due to the oxidation of lignin linkages. According to our results the levoglucosan/2-methoxy phenol ratio can be improved if the wheat straw is pretreated at a 270° C. in the presence of oxygen. The presence of oxygen was detrimental for the Douglas Fir.
The effect of pyrolysis temperatures on the selectivity of thermochemical reactions towards the production of levoglucosan in unpretreated samples is shown in FIG. 9. The results indicate that as the pyrolysis temperature increases the fragmentation reactions responsible for the formation of hydroxyacetaldehyde are favored over the depolymerization reactions responsible for the formation of anhydrosugars. Although this behavior was observed for all the samples, the effect of temperature was more pronounced for the Avicel and for the α-cellulose. Materials containing lignin show a much less pronounced effect.
Tests on auger pyrolysis were also conducted. Douglas Fir wood was pre-treated at select conditions identified by Py-GC/MS and was subject to pyrolysis in the Auger Pyrolysis reactor built at Washington State University (generally similar to that shown in FIG. 3A). During testing, 200 g of Douglas Fir samples were added into 3 L of deionized water. The biomass and the water were heated in an autoclave (Consolidated Stills & Sterilizers) at 120° C. for 20 min.
The water and the solid were separated by filtration. The solid was dried overnight at 105° C. For every 200 g of biomass 175 g of pre-treated samples were obtained (87.5 mass %). These samples were further subject to a mild torrefaction in the same Auger reactor but using lower wall temperatures (e.g., 270° C.). The reactor was operated under a nitrogen atmosphere (flow rate of nitrogen: 3 l/min) and the biomass particles were conveyed through the Auger at 5.2 rpm (Pretreatment time: 2.5 minutes).
Pyrolysis tests on the pre-treated samples were carried out in the same Auger Pyrolysis reactor. The reaction conditions were the following: Auger speed: 13 rpm (residence time of particles in the reactor: 1 minute), hopper feeding rate: 43.6 rpm, pressure inside the reactor: 1 atm., carrier gas: N2, flow rate: 10 l/min, temperature in the wall of the reactor: 500° C., post-oven temperature 420° C.; estimated heating rate: (4-7° C./s or 240-420° C./min). Although the heating rates achieved are lower than the 10-1000° C./s needed for fast pyrolysis reactors it is still faster than the 10° C./min typically reported for slow pyrolysis. The yield of products obtained with Douglas Fir as received and after hot water and thermal pretreatment at 270° C. for 3 minutes are shown in Table 1. The oil produced in our system is a single phase oil very similar to those produced in fast pyrolysis reactors.

TABLE 1

	Hot Water	Hot Water + Oven
Original Douglas Fir	Pretreatment	Pretreatment

Bio-oil	55.4 ± 4.6	57.1 ± 1.1	56.8 ± 3.6
Char	22.7 ± 5.0	17.4 ± 0.5	19.5 ± 4.8
Gas	21.7 ± 0.6	25.5 ± 1.6	23.7 ± 1.3

Production of ethanol from pyrolytic sugars was also investigated. Two bio-oils were used to produce ethanol. The first bio-oil produced from a hardwood provided by Dynamotive. The second bio-oil studied was produced in a fast pyrolysis reactor at Monash University (Australia) using as a feedstock a softwood bark. The name and the content of each of the species quantified by GC/MS and by Karl Fischer Titration are listed in Table 2.

TABLE 2

	Softwood Bark	Dynamotive
Compound	Oil (Monash)	Oil

1	Water	13.92	29.35
2	Glycolaldehyde	1.41	1.62
3	Acetic Acid	1.17	3.30
4	Acetol	1.56	2.67
5	Toluene	0.003	0.001
6	Cyclopentanone	0	0.002
7	2-Furaldehyde	0	0.52
8	2-Cyclopenten-1-one, 2-methyl-	0	0.04
9	2(5H)-Furanone	0	0.36
10	2-Furanethanol, b-methoxy-(S)-	0.35	0.83
11	Phenol	0.58	0.29
12	O-Cresol	0.28	0.14
13	p-Cresol and m-Cresol	0.55	0.18
14	Phenol, 2-methoxy-	1.81	1.07
15	Phenol, 2,4-dimethyl- and	0.31	0.12
	Phenol, 2,5-dimethyl-
16	Phenol, 4-ethyl-	0.26	0.08
17	Phenol, 3,4-dimethyl-	0.22	0
18	Phenol, 2-methoxy-4-methyl-	0.80	0.29
19	Pyrotechol	1.14	0.67
20	1,2-Benzenediol, 3-methyl-	0.71	0
21	Phenol, 4-ethyl-2-methoxy-	0.43	0.17
22	1,2-Benzenediol, 4-methyl-	1.56	0
23	Syringol	0	1.11
24	Eugenol	0.31	0.13
25	Phenol, 2-methoxy-4-propyl-	0.21	0.09
26	4-Ethylcatechol	0.16	0
27	Vanillin	0.45	0.30
28	Phenol, 2-methoxy-4-(1-	0.76	0.05
	propenyl)-, (E)-
29	1,6-Anhydro-b-D-Glucose	3.61	4.07
30	2-Propanone, 1-(4-hydroxy-3-	0.52	0
	methoxyphenyl)-
31	Syringaldehyde	0	0.50
32	Phenanthrene, 1-methyl-7-	0.003	0
	(1-methylethyl)-

Total	33.09	47.9

As shown in Table 2, the softwood bark derived oil produced at Monash contains significantly less water than the oil provided by Dynamotive. The content of phenols in the softwood bark derived oil is higher than in the oil provided by Dynamotive.
Table 3 shows the content of sugars in the oil produced by Dynamotive. The glucose quantified in this oil was derived from the hydrolysis of levoglucosan, cellobiosan and other oligo-anhydrosugars. The content of glucose (a fermentable sugar) in these oils is approximately 5.02 mass %. This concentration of sugar is suitable for fermentation. The other sugars derived from hemicelluloses (fucose, arabinose, galactose, mannose/xylose, fructose, ribose) accounted for 1.08 mass % of this oil.

	TABLE 3

	Sugars	Content (mass %)

	Fucose	0.058
	Arabinose	0.105
	Galactose	0.197
	Glucose	5.028
	Mannose/Xylose	0.586
	Fructose	0.115
	Ribose	0.019
	Total sugars	6.108

Although the bulk of the phenolic compounds from bio-oil can be extracted with the ethyl acetate, small concentrations of these toxic compounds remain in the aqueous phase together with most of the sugars. The nature and the range of lethal concentrations of many of these toxic compounds was not well known. Thus, we carried out tests with model compounds to identify which of them were toxic to yeasts.
The toxic effects of selected bio-oil compounds (acetic acid, propanoic acid, cyclopentanone, 2-furaldehyde, furfuryl alcohol, phenol, eugenol, acetol, 2-(5H)-furanone, stilbene, vanillin, syringaldehyde, o-cresol) on Saccharomyces cerevisiae were studied. The concentration of each of the compounds tested was 25, 50, 75 and 100% of the concentration found in bio-oils (CFBO) for a fast pyrolysis oil derived from Mallee which was produced at a pyrolysis temperature of 500° C. The inhibition rate estimated for the compounds studies is shown in Table 4.

TABLE 4

		25% of	50% of	75% of	100% of
N^o	Compound	CFBO	CFBO	CFBO	CFBO

1	Acetic acid	97.75	97.75	97.96	98.24
2	Propanoic acid	97.01	97.54	97.82	98.00
3	Cyclopentanone	−22.07	−5.26	−4.41	21.73
4	2-furaldehyde	7.81	7.98	11.03	95.89
5	Furfuryl alcohol	5.94	6.90	7.81	7.81
6	Phenol	76.95	96.95	97.45	97.67
7	Eugenol	97.04	97.22	96.64	97.04
8	Acetol	44.17	77.80	78.93	80.07
9	2-(5H)-Furanone	3.057	5.89	8.83	10.42
10	Stilbene	9.17	32.62	37.89	45.07
11	Vanillin	81.54	82.45	81.77	81.88
12	Syringaldehyde	71.68	79.95	81.54	81.99
13	O-cresol	2.61	14.16	23.38	31.22
14	O-xylol	5.01	5.23	5.33	5.44
15	Pyrocatechol	84.53	90.48	91.67	92.10
16	Palmitic acid	2.63	0.36	−2.02	−4.19
17	Toluene	−0.72	1.00	1.66	2.09
18	Tetradecane	1.11	4.68	10.53	10.64
19	Petadecane	4.68	7.39	8.90	9.78

As shown in Table 4, the carboxylic acids (acetic acid and propanoic acid) and the phenols (phenol, eugenol, vanillin, syringaldehyde, pyrocatechol) are the most lethal compounds inhibiting yeast growth. The furans (furaldehyde, furfuryl alcohol, 2-(5H)-furanone) and the alkanes (tetradecane, pentadecane) are also inhibitors but their inhibition rate is much lower.
Extraction of phenols, hydrolysis, detoxification and fermentation of pyrolytic sugars were also tested. Ethyl-acetate was the solvent used for the extraction of compounds from the bio-oil. The method employed to separate the phenols is similar to the one patented by NREL for the production of resins. Briefly, blends of ethyl acetate/bio-oil with mass ratio of 1:1 were prepared. The blends were shaken for 10 minutes at 30° C. and were left to equilibrate for over 6 hours. The organic phase rich in ethyl acetate which contains most of the phenols was separated by decantation and the ethyl acetate solubilised in the aqueous phase removed with a rotary evaporator at 80° C.
The sugars in the aqueous phase (levoglucosan, cellobionsan) were hydrolysed using H₂SO₄as catalyst to produce glucose. The phenols remaining in the aqueous phase were removed by adsorption on activated carbon. An activated carbon/aqueous solution volume ratio of 1:1 was employed. The aqueous solution was left overnight at 4° C. in the refrigerator and the slurry formed was filtrated to obtain a colorless liquid. The aqueous solution containing the sugars was then neutralized to pH 7 with solid barium hydroxide. Under these conditions the free sulfuric acid and the acetic acid present in the aqueous phase are removed as precipitated salts.
The content of sugars in the detoxified solution was quantified by Ion Exchange Chromatography and the detoxified aqueous phase rich in sugars was then fermented. Briefly, YPD media was prepared by taking 25 ml of the detoxified solution obtained in the previous step, 2 mass % yeast extract and 1% mass peptone. 10 vol of Saccharomyces cerevisiae seed culture media was then inoculated in the YPD media. The media was cultured at 30° C. and the micro-organism growth, sugar consumption and ethanol production were monitored by UV-Vis, ion exchange chromatography, and GC-FID. The initial content of glucose in the detoxified aqueous phases from the Dynamotive oil and from the oil produced in Monash University were 2.6 and 2.0 mass % respectively. Clearly the solvent extraction method should be further improved. Control solutions containing the same concentrations of glucose were also fermented.
FIG. 10 shows a glucose content as a function of fermentation time. Based on the consumption of glucose it appears that the fermentation process happened mainly during the first 5 hours. No major difference was observed between the behavior of the control and the solutions derived from pyrolysis oils.
FIG. 11 shows a rate of microbial growth in solutions derived from bio-oils and in control solutions produced with glucose. As shown in FIG. 11, most of the growth happened in the first 5 hours and that the growth in the solution derived from bio-oil was comparable with the growth obtained with the control solution prepared with glucose. Very little microbial growth was observed after the first 5 hours.
FIG. 12 shows ethanol concentration as a function of fermentation time. High concentrations of ethanol were produced (12-16 g/L) during the first 5 hours. The production of ethanol slowed down after almost the same time that the content of glucose in the solution was depleted. The production of ethanol from the solutions derived from bio-oils was comparable to the production of ethanol from the control. The effect of any inhibitor remaining in the solution was negligible.
Fatty acids were produced from glucose using oleaginous yeasts (Cryptococcus curvatus and Rhodotorula glutinis yeasts). These yeasts were cultured for periods varying between 24 and 144 hours on a mixture rich in xylose and glucose which were derived from pyrolysis oils. The initial content of glucose in the solution was 6.8 mass %.
FIG. 13 shows sugar consumption and production of fatty acids as a function of fermentation time in accordance with embodiments of the technology. Microorganisms with fat content ranging from 28 to 68 mass % were obtained with the Cryptococcus curvatus. Lower fat contents (between 13 and 45 mass %) were obtained with Rhodotorula glutinis. The most important fatty acids found in Cryptococcus curvatus were: palmitic (C16:O) (20 mass %), stearic (C18:O) (20 mass %) and oleic (48 mass %) acids. A slightly different fatty acid profile was observed for the Rhodotorula glutinis: palmitic (15 mass %), stearic (20 mass %) and oleoic: (51 mass %).
From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Many of the elements of one embodiment may be combined with other embodiments in addition to or in lieu of the elements of the other embodiments. Accordingly, the technology is not limited except as by the appended claims.

Claims

1. A process for processing a biomass, comprising:

treating a biomass by heating the biomass at a first temperature;

thermally converting the treated biomass into a product having an oil portion and an aqueous portion via pyrolysis at a second temperature, the first temperature being lower than the second temperature; and

selecting the first temperature based on a correlation between the first temperature and a desired anhydrosugar content in the oil portion of the product.

2. The process of claim 1 wherein thermally converting includes using a synthesis gas as a carrier gas in a pyrolysis reactor.

3. The process of claim 1, further comprising producing an oil phase in a first condenser and producing an aqueous phase in a second condenser, the first and second condensers are in a series.

4. The process of claim 1, further comprising separating sugars from phenols in the oil phase via liquid-liquid extraction with a solvent.

5. The process of claim 1, further comprising converting at least a fraction of sugars in the oil phase to ethanol.

6. The process of claim 1 wherein the oil phase contains sugars, and wherein the process further comprising converting at least a fraction of the sugars into lipids.

7. The process of claim 1 wherein treating a biomass includes treating a biomass by heating the biomass at a first temperature of about 200° C. to about 300° C.

8. The process of claim 1 wherein treating a biomass includes treating a biomass by heating the biomass at a first temperature of about 200° C. to about 300° C. for a period of time of about 3 minutes to about 10 hours.

9. The process of claim 1 wherein treating a biomass includes treating a biomass by heating the biomass at a first temperature of about 200° C. to about 300° C. for a period of time of about 1 minutes to about 10 hours, and wherein the first temperature is inversely related to the period of time.

10. A process for processing a biomass, comprising:

providing a biomass having a first crystallinity;

modifying a structure of cellulose in the biomass to have a second crystallinity higher than the first crystallinity; and

thermally converting the biomass with the increased crystallinity into a pyrolysis product containing anhydrosugar via pyrolysis.

11. The process of claim 10 wherein:

the first crystallinity of the biomass corresponds to a first anhydrosugar content of the pyrolysis product; and

modifying the structure of cellulose includes modifying the structure of cellulose to have a second crystallinity and/or a degree of polymerization corresponding to a second anhydrosugar content higher than the first anhydrosugar content of the pyrolysis product.

12. The process of claim 10 wherein:

the first crystallinity of the biomass corresponds to an anhydrosugar content of the pyrolysis product; and

modifying the structure of cellulose includes enhancing the anhydrosugar content of the pyrolysis product.

13. The process of claim 10 wherein modifying the structure of cellulose includes heating the biomass at a first temperature of about 200° C. to about 300° C.

14. The process of claim 10 wherein modifying the structure of cellulose includes heating the biomass at a first temperature of about 200° C. to about 300° C. for a period of time of about 1 minute to about 10 hours.

15. The process of claim 10 wherein modifying the structure of cellulose includes heating the biomass at a first temperature of about 200° C. to about 300° C. for a period of time of about 3 minutes to about 10 hours, and wherein the first temperature is inversely related to the period of time.

16. A process for processing a biomass, comprising:

heating a biomass at a first temperature;

thermally converting the heated biomass into a product via pyrolysis at a second temperature, the first temperature being lower than the second temperature; and

wherein the first temperature is selected to enhance an anhydrosugar content in the product from thermally converting the heated biomass.

17. The process of claim 16 wherein the first temperature is selected to be about 200° C. to about 300° C.

18. The process of claim 16 wherein the first temperature is selected to be about 200° C. to about 300° C., and wherein a heating period of time is also selected to enhance the anhydrosugar content in the product from thermally converting the heated biomass.

19. The process of claim 16 wherein the first temperature is selected to be about 200° C. to about 300° C., and wherein a heating period of time is also selected to enhance the anhydrosugar content in the product from thermally converting the heated biomass, the heating period of time being about 1 minute to about 10 hours.

20. The process of claim 16 wherein the first temperature is selected to be about 200° C. to about 300° C., and wherein a heating period of time is also selected to enhance the anhydrosugar content in the product from thermally converting the heated biomass, the heating period of time being about 1 minutes to about 10 hours and inversely related to the first temperature.