Biofuels Research
Personnel:
Dr. Ananda Amarasekara, Group Lead and Co-PI, Department of Chemistry
Dr. Paul Biney, Co-PI and Technical Coordinator, Department of Mechanical Engineering
Dr. Michael Gyamerah, Department of Chemical Engineering
Objectives and Tasks:
The principal objectives of the biofuels research are to: (1) make in-depth fundamental studies to
understand the reaction pathways of fast pyrolysis and how they affect the final composition of biooil and other by-products as process variables are varied in an effort to improve yields and quality of
specific chemical species present in the bio-oil.; (2) develop an environmentally benign and
industrially feasible lignocellulosic biomass hydrolysis method using ionic liquid catalyst for
cellulosic-ethanol production, and (3) develop catalytic conversion strategies for upgrading bio-oil to
useful fuels.
A. Current Research
1. Moisture Content of Biomass
The drying procedure used in determining the moisture content was based on NREL LAP on
“Preparation of Samples for Compositional Analysis”. The arundo biomass from TAMU had the
highest as received moisture content of 20.8%. The alfalfa biomass from the Noble Foundation in
Oklahoma had the lowest as received moisture content of 6.4%.


The high moisture content of arundo and the other biomass make it necessary to dry the biomass
in order to reduce the amount of water in the bio-oil produced from these biomass.
That the moisture content of biomass is highly dependent on the source of the biomass as
evidenced by the 11.5% moisture content of the switch grass from Texas A&M and 6.9% moisture
content of the switch grass from the Noble Foundation in Oklahoma
2. Soluble Extractives in Biomass
The soluble extractive procedure was based on NREL LAP on “Determination of Extractives in
Biomass”, NREL/TP-510-42619 . Three solvent s (water, ethanol, and hexane) were used to extract
soluble compounds in the various biomass.
The water soluble extractives include: (1) non-structural carbohydrates such glucose, fructose,
sucrose, galactose, mannose, arabinose and xylose, (2) alditols such as sorbitol, mannitol and
xylitol, (3) organic acids including acetic, lactic, fumaric, malic, citric, hydroxybenzoic and vanillic
acid and (4) inorganic ions including Na+, K+, NH4+, Mg2+, Ca2+, Cl-, NO3- and SO42- .
Ethanol soluble extractives include: (1) waxes that consist of fatty acids, fatty alcohols, alkanes,
sterols, hydroxyl-beta-diketones and beta-diketones with long carbon chain molecules from 12 up to
38 carbon atoms, (2) fats, (3) tannings, the phenolic class of secondary metabolites in plants, and
(4) pigments such as chlorophyll.
Hexane soluble extractives include (1) highly non-polar waxes, sterol esters, ferulic acid esters,
terpenes, furfural alpha- and beta-pinene, and limonene that are not effectively extracted by ethanol.
The results indicate that: There are more water soluble extractives in the biomass followed by
ethanol soluble extractives. There is very little hexane extractives in the biomass as it followed the
ethanol extraction. Switch grass has the highest water soluble extractives (9.1%) and corn stover
had the least water soluble extractives (1.3%). Alfalfa has the highest ethanol soluble extracts
(5.2%). The highest ethane soluble extracts (0.4%) were in switch grass and Arundo.
3. Weight (%) Cations in Biomass
The objective of this activity was to perform a compositional analysis on the water-soluble extracts of
samples of the five biomass types. The first step was to determine the amounts of cations and
anions present in these samples. The knowledge of these ions present will be of utmost importance
in the characterization of biomass as they influence the yields of biofuels during the pyrolysis
process.
Ion Chromatograph, ICS-5000, for determination of ions in the extracts using the standard operating
procedures for using ICS-5000 ion chromatograph for determining anion and cations was used in
this work. Three samples were run for each test and the average of the three results used to
determine the concentration of ions in the water extracts of the biomass samples using a previously
prepared calibration curve with known concentrations of ions as standards. From the volume of
extracts and concentration obtained the amounts of ions in the biomass and the composition of
cations and anions in each biomass were calculated. Results are shown graphically here.
4. Weight (%) Anions in Biomass
The weight % anions in the biomass obtained from ICS-5000 analysis of the water soluble extractive
is shown in the Table below for switch grass an corn stover. This analysis is still in progress for the
other biomass.
Biomass
Wt %
Acetate ion
Wt %
( Cl-
Wt %
( Br- )
Wt %
( NO3- )
Wt %
( PO4- )
Wt %
( SO4- )
Switch Grass
0.143
0.504
0.019
0.045
0.199
0.113
Corn Stover
0.021
0.024
0
0
0.068
0.025
5. CHNSO Elemental Composition of Biomass
The objective of this section of the research is to determine the elemental composition, specifically,
carbon, hydrogen, nitrogen, sulphur, and oxygen in switch grass, alfalfa, arundo, corn stover and
sawdust. The procedure described in the standard operation procedure for determining CHNS & O
composition using the Flash2000 was used in running the tests. The tabulated and graphical results
are shown These results are comparable to what are reported in the literature.
6. Biomass Decomposition Kinetics Study Using High Resolution, TA Modulated Q500 TGA
Decomposition kinetics study of the six biomass (alfalfa, switch grass, red oak, corn stover, arundo,
and sawdust) have been made using the TA Q500 TGA. The analysis was based on four constant
heating rates (2.5, 5, 10 and 20 oC/min) using the conventional TGA approach and analy
whereα= fraction of decomposition, t = time (seconds), Z = pre-exponential factor (1/seconds), Ea =
activation energy (J/mole), R = gas constant (8.314 J/mole K), and n = reaction order
(dimensionless). Flynn and Wall rearranged this equation to get
Using a point of equivalent weight loss (decomposition), a plot of ln( b) vs. 1000/T is constructed as
shown graphically here for alfalfa at different conversion points. The slopes of these straight line
plots are then used to calculate activation energy (Ea) at each conversion, and the pre-exponential
factors (Z) are calculated by the interactive method of Zsako and Zsako to generate the kinetic data
in the table for alfalfa. This approach was used to generate similar plots and kinetic data table for the
other biomass.
7. Research on Development of Brönsted acidic ionic liquids as green catalysts for
hydrolysis of lignocellulosic biomass in the cellulosic-ethanol process
Lignocellulosic biomass is composed of cellulose, hemicellulose, and lignin, and the typical
percentage composition by dry weight is 35–50% cellulose, 20–35% hemicellulose, and 5–30%
lignin. These carbohydrate polymers (cellulose and hemicelluloses) are tightly bound to the lignin,
invariably encapsulated in lignin structure.
In 2009 our research group introduced the use of sulfonic acid group functionalized Brönsted acidic
ionic liquids (figure 1) for concurrent dissolution and hydrolysis of cellulose under mild conditions. In
these experiments cellulose (DP ~ 450) was found to dissolve up to 20% w/w in 1-(1-propylsulfonic)3-methylimidazolium chloride and could be hydrolyzed into glucose and other reducing sugars at 70
°C and atmospheric pressure in excellent yields by treatment with controlled small amount of water
(Ind. & Eng. Chem. Res., 2009, 48(22), 10152). The mechanism proposed for the acidic ionic liquid
catalyzed hydrolysis of cellulose is shown in figure 2.
As these neat ionic liquid based cellulose depolymerization methods require large volumes of ionic
liquids as solvents and complete recovery and reuse of the ionic liquid is essential in any large scale
industrial process. This is quite challenging since both the resulting sugars and these ionic liquids
are highly soluble in water. Therefore, in the second stage of our investigations we concentrated our
efforts in the direction of using acidic ionic liquid as a glycosidic bond hydrolysis catalyst in aqueous
medium. This is a highly attractive proposition and can be seen as an attempt to develop an “artificial
cellulase” type green catalyst for the long awaited cellulosic-ethanol process.
Our preliminary efforts in the use of dilute aqueous solutions of acidic ionic liquids in water has
shown promising results and some of these results have been published recently (Ind. & Eng. Chem.
Res., 2011, 50). In these experiments, we have found that dilute aqueous solutions of 1-(1propylsulfonic)-3-methylimidazolium chloride and p-toluenesulfonic acid are better catalysts than
aqueous sulfuric acid of the same H+ ion concentration for the degradation of cellulose at moderate
temperatures and pressures. For example, Sigmacell cellulose (DP ~ 450) in aqueous solutions of 1(1-propylsulfonic)-3-methylimidazolium chloride, p-toluenesulfonic acid, and sulfuric acid of the same
acid strength (0.0321mole H+ ion /L) produced total reducing sugar (TRS) yields of 28.5, 32.6, and
22.0 % respectively, after heating at 170 °C for 3.0 hr. A typical set of TRS % yields versus
temperature plots for acidic ionic liquid (1), p-toluenesulfonic acid and sulfuric acid mediums are
shown in figure 3.
The changes in % yields of total reducing sugar (TRS) produced during the hydrolysis of Sigmacell
cellulose (DP ~ 450) in aq.1-(1-propylsulfonic)-3-methylimidazolium chloride, aq. sulfuric acid and
aq. p- toluenesulfonic acid at different temperatures. All acid solutions are 0.0321 mol H+/L, reaction
time: 3.0 hr., 0.030 g of Sigmacell cellulose in 2.00 mL of aq. acid was used in all experiments.
Averages of duplicate experiments. We are continuing these efforts to develop an aqueous phase
cellulose hydrolysis catalyst based on ionic liquid core structures, and to produce an artificial
cellulase type catalysts for biomass processing. In pursuing this goal we are studying quantitative
structure activity relationships (QSAR) in order to understand the mechanisms of interaction of ionic
liquid structures like imidazolium cation, and their counter-ions with cellulose in aqueous medium.
B. Research Planned for the Near Future
A number of research activities described below are planned for summer and Fall 2013.
1. Fabrication, Testing and Use of High Conversion Fixed Bed Pyrolysis Reactor
The research team has designed a new fixed bed reactor capable of increasing the conversion rate
of biomass to bio-oil. The unique features of this new rector design are the way the career nitrogen
gas is introduced and dispersed in the reactor and the way the reaction gases are collected and
carried away from the reactor in a way that decreases the residence time in contact with the reactant
biomass or residual char. Parts for building the reactor are currently being ordered. The system will
be constructed, tested and used to study the effects of processing parameters on biofuel yields with
and without catalysts.
2. Determination of structural carbohydrates and Lignin in Biomass
The water, ethanol and hexane extracted biomass will be dried to constant weight and 0.30 g added
to a tarred pressure tube. A 3.0 ml of 72% w/w sulfuric acid will be added to the biomass in the
pressure tube and the contents thoroughly mixed, placed in a water bath at 30 oC and incubated for
60 min to hydrolyze the biomass. The acid will be diluted 4% w/w and the tube placed in an
autoclave safe rack and autoclaved for 1 hour at 121oC. The hydrolyzate will be allowed to cool
slowly after autoclaving and the hydrolysis solution vacuum filtered through a previously weighed
filtering crucible. 50 ml of the filtrate will be collected and stored for determination of hydrolyzed
structural carbohydrates and acid soluble lignin using the ICS 5000 and a UV-Vis spectrophotometer
at 198nm respectively. The acid insoluble lignin will be found by difference after drying the filtered
insoluble residue to constant weight.
3. Bio-oil Upgrading into Transportation
The initial step in this task to be initiated this summer will involve screening of catalysts including
sulfided Co-Mo-P catalysts, zeolites and commercial ReUSY containing Re2O3 in catalytic
conversions of bio-oil by hydro treatment, and simultaneous dehydration and decarboxylation
Determining the kinetics and evaluating the yields and selectivity of each catalyst for hydrocarbons
and optimizing efficiency of bio-oil conversion is also planned for this Fall.
8. Fermentation of ionic liquids hydrolyzed lignocellulosic biomass fermentable sugars
Determination of the maximum non-inhibitory level of ionic liquid catalysts in fermentable sugars
from hydrolysis of lignocellulosic biomass for ethanol fermentation will be conducted using the
formulated acidic ionic liquids..
Following this, batch fermentations by recombinant yeast (Saccharomyces cerevisiae TMB3665)
expressing pentose utilization pathway and recombinant pentose-fermenting
bacterium Zymomonas mobilis AX101 of the fermentable sugars from ionic liquids hydrolyzed
lignocellulosic biomass will be conducted.