Bio-jet fuel produced from non-edible oilseeds can be an alternative to fossil fuels with the benefits of increasing national energy security, reducing environmental impact, and fostering rural economic growth. Efficient oil extraction from oilseeds is critical for economic production of bio-jet fuels. Oil extractions from camelina (sativa) and canola ( Brassica napus) seeds were conducted using a cold press method. The effect of the frequency controlling the screw rotation speed on the oil recovery and quality was discussed. Characterization of the produced raw vegetable oils, such as heating value, elemental content and main chemical compositions, was carried out. The results showed that the oil recovery increased when the frequency decreased. The highest oil recoveries for camelina and canola seeds were 88.2% and 84.1% respectively, both at 15 Hz. The cold press frequency and processing temperature (97.2 °C - 106.0 °C) had a minor influence on the qualities and recovery of both camelina and canola oils. In addition, camelina and canola oils produced at 15 Hz underwent catalytic cracking to examine potential hydrocarbon fuels production. It was observed that some of oil physicochemical properties were improved after catalytic cracking. Although more study is needed for further improvement of oil recovery and qualities, cold press could be an efficient method for oil extraction from non-edible oilseeds. Additionally, the preliminary results of upgrading the oils produced show very promising for future bio-jet fuels production.
As a result of concerning food vs. fuel debates, current biofuel development has focused on non-edible feedstock sources. Presently, a large number of non-edible vegetable oils are available, which do not compete with the food industry, so they can provide a source for bio-jet fuel production. In general, non-edible vegetable oil sources are classified into three categories: non-edible plant oils (e.g. Camelina sativa, Jatropha curcas, Nicotiana tabacum and tamanu), recycled oils derived from edible oilseed processing waste, and waste cooking oils. For example, genetically modified canola grown on margin lands has been identified as a sustainable biofuel source because it doesn’t occupy arable land. These margin lands are largely unproductive, or located in degraded forests and poverty-stricken areas. However, the canola plants are well adapted to arid and semi-arid conditions as they can grow on lands with low fertility and moisture, such as fallow lands, cultivators’ field boundaries and old mining lands [
Oilseeds produce oils that may be subsequently upgraded into saturated, unbranched and long-chain hydrocarbon fuels, which are suitable for bio-jet fuel production [
Vegetable oil extraction from oilseeds is a key step for bio-jet fuel production. Vegetable oil properties, specifically fatty acid profiles (FAPs) of oils, are dependent on oilseed species, oil extraction techniques and pro- cessing conditions. FAP is the quantitative composition of fatty acids in a vegetable oil. C16 and C18 fatty acids are the most common fatty acids in the vegetable oil. Fatty acids could affect the characteristics of vegetable oil, such as viscosity, oxidative stability, boiling point and combustion energy, so vegetable oil with good FAP is easily upgraded into a desired hydrocarbon fuel at high efficiency and low cost [
Rombaut et al. have used screw pressing method to extract oils from grape seeds. They found that screw pressing was an efficient process for extracting grape seed oils with a high oil recovery [
The goal of this study is to explore a sustainable pathway to produce bio-jet fuel from non-edible vegetable seeds. In the present work, oil extraction from non-edible camelina and canola seeds will be performed using the cold press method. The vegetable oils produced will be characterized. The effects of screw rotation speed frequency on the oil recovery and properties, such as moisture content, pH value, density, dynamic viscosity, elemental content and chemical composition will be discussed. In addition, a preliminary catalytic cracking test of camelina and canola oils produced at 15 Hz will be conducted to examine their potential for upgrading to hydrocarbon fuels.
Camelina (sativa) seeds were purchased from Hancock Seed Company, Dade, Florida, USA. Canola (Brassica napus) seeds were purchased from Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada. These oilseeds, shown in
Oil extraction from camelina and canola seeds was carried out at different frequencies using the M70 Oil Press
Oilseeds | Length (mm) | Width (mm) | Shape | Bulk Density (g/mL) | Moisture (wt%) |
---|---|---|---|---|---|
Camelina | 1.6 - 1.9 | 0.7 - 1.0 | Oval | 0.76 ± 0 | 4.92 ± 0.04 |
Canola | 1.1 - 1.8 | 1.1 - 1.8 | Tiny round | 0.72 ± 0.02 | 5.36 ± 0.04 |
to discover the highest recovery of vegetable oils. The M70 Oil Press, as shown in
After screw pressing the oilseeds, some oils remained in the meals. The meals were then ground using a mill (Thomas-Wiley Laboratory Mill, Model 4, Thomas Scientific , USA) and sieved through a 10 mesh screen. The meal flours were processed using a solvent extraction method to determine the residual oil content. An Accelerated Solvent Extractor (Dionex ASE 350, Thermo Scientific Company) was utilized to test the residual oil content in meals.
Camelina and canola oils cold pressed at 15 Hz were subjected to catalytic cracking in a fixed-bed reactor at 500˚C at a liquid hourly space velocity (LHSV) of 1.0 h−1. Nitrogen was used as the carrier gas in the reactor with a pressure of 1.38 × 105 Pa (20 psi). A preheater was used to vaporize oils for improved contact with the catalyst. ZSM-5 doped with 10 wt% of Zn was used as the catalyst, which was placed in a reactor. The reactor, fixed coaxially in a furnace, was a 508 mm long stainless steel tube with a 25.4 mm internal diameter. When oil vapors came in contact with the catalyst, cracking reactions took place. A condenser system setting at −10˚C was used to cool the produced oil gases into liquid, considered as upgraded oils. Non-condensable gases, including H2, CO, CO2 and light hydrocarbons, were sampled for the composition analysis.
Upgraded camelina oils (UCMO) and upgraded canola oils (UCNO) were a mixture mainly containing hydrocarbons, acids and other oxygenates. They were distilled at 230˚C in order to separate small molecules with lower boiling points. During distillation, small molecules with boiling point lower than 230˚C became vapors. These vapors flowed into an overhead condenser system and were cooled back into liquid, considered as mixed hydrocarbons. Large molecules with boiling point higher than 230˚C were too heavy to vaporize and they were remained as distillation residues in the distillation flask.
The obtained vegetable oils, upgraded oils, mixed hydrocarbons and distillation residues were characterized by testing their dynamic viscosity, pH value, moisture content, density, main chemical compositions, elemental content, heating value and yield.
Dynamic viscosity of samples was tested using a Visco Analyzer (REOLOGICA Instruments AB Company) at
20˚C. The moisture content of samples was measured using a Karl Fischer Titrator V20 (Mettler Toledo Company) at 25˚C, which is within ASTM E1064 standard. PH values were determined using a pH meter (Accumet BASIC AB15, Fisher Scientific) at 25˚C and pH testing papers. The density of samples was measured by the ratio of mass to volume of the samples at room temperature [
The major chemical compositions of samples were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) (Agilent GC -7890A and MSD -5975C ), that uses hydrogen as a carrier gas with a flow rate of 1.0 mL/min. The capillary columns are 30 m × 0.25 mm × 0.25 µm DB-5MS. The samples were prepared following the derivatization procedure. About 30 mg sample was mixed with 4 mL hexane. The mixture was shaken for 2 min, and then 2 mL BF3-methanol, 12% w/w, and 2 mL CH3OH were added into the mixture. The mixture was heated at 60˚C for 10 min to carry out the simultaneous hydrolysis and methylation. Then, the mixture was cooled down to room temperature and 1 mL distilled water and 2 mL hexane were added in order to remove the excess reagents. The organic phase of the mixture was separated by centrifugation at 2500 g and 25˚C for 10 min. The organic layer was carefully removed and dried over anhydrous sodium sulfate. Finally, the dry organic phase was injected into the GC-MS equipment. The GC-MS test parameters were as follows. One µL of the dry organic phase was introduced through the injection port operated in a splitless mode at 260˚C. The original column temperature was 175˚C and the holding time was 6 min. Then, the column temperature became 260˚C after 5.67 min at a rate of 15˚C/min. The holding time at 260˚C was 15.68 min. The splitless time was 30 s and the total run time was 27.35 min. The major components were identified through the NIST Mass Spectral library [
Carbon (C), hydrogen (H), nitrogen (N), and oxygen (O) content analysis of samples was determined using a CE-440 Elemental Analyzer (Exeter Analytical. Inc.) according to ASTM D4057 standard. Acetanilide was used for calibration. For CHN content analysis, the combustion and reduction temperatures were 980˚C and 650˚C, respectively. The oxygen and helium pressure were 1.51 × 105 Pa (22 psi) and 1.17 × 105 Pa (17 psi), respectively. The fill time was between 20 and 50 s. The combustion and purge time were both 20 s. Samples were sealed in a tin capsule and placed in a nickel sleeve. For O content analysis, the combustion and reduction temperature were 960˚C and 770˚C, respectively. Only helium was used as the carried gas at 1.17 × 105 Pa (17 psi). The combustion and purge time were 40 s and 50 s, respectively. The sample was sealed in a silver capsule and placed inside a nickel sleeve [
The heating value was tested using a C 2000 Calorimeter System (IKA-Works, Inc.) according to the temperature change of water inside the measuring cell, based on ASTM D 4809 standard. About 0.5 g sample was added in a crucible and placed in a bomb. The sample was ignited with a cotton twist.
The Accelerated Solvent Extractor was used to determine the residual oil content inside the vegetable oilseed meals. About 12 g meal flours were used in this test and hexane was used as the solvent. The oven temperature was 105˚C and the static time was 10 min. The rinse volume was 50% and the purge time was 60 s. The meal flours were mixed with hexane and the oil inside was dissolved. After the oil was dissolved, the mixture of oil and hexane was separated from the solid materials of the meal flours. Then, the oil was separated from hexane by using a distillation system and the oil content remaining in meals was calculated. The oil extraction was completed with three static cycles. The tests for oil content in each residual meal sample were carried out three times [
The oil content of oilseeds depends on many factors such as variety, fertilization, growth environment and agricultural production technologies [
The yields of products were defined by the following equations:
Yield of upgraded oils = (mass of upgraded oils/mass of oils feed) × 100% (1)
Yield of mixed hydrocarbons = (mass of mixed hydrocarbons/mass of upgraded oils feed) × 100% (2)
Yield of distillation residues = (mass of distillation residues/mass of upgraded oils feed) × 100% (3)
In this study, all treatments were conducted in duplicate. The determination of the mean and standard deviation of each parameter was carried out using Microsoft Excel 2013 (Microsoft Corp., Redmond, WA).
For both camelina and canola oils, they mainly contained fatty acids. Fatty acid profile is one of the important factors that affect the upgrading of vegetable oils for future jet fuel production. Furthermore, unsaturated fatty acids occupied most of the fatty acids in camelina and canola oils. These unsaturated fatty acids varied in the extent of unsaturation and in the carbon chain length. However, the main unsaturated fatty acid in both camelina and canola oils contained the same carbon chain length, C18.
Camelina | Canola | |||
---|---|---|---|---|
Component | Area (%) | Component | Area (%) | |
25 Hz | Hexadecanoic acid (C16H32O2) | 0.23 | Hexadecanoic acid (C16H32O2) | 0.18 |
9,12-Octadecadienoic acid (Z,Z)- (C18H32O2) | 0.15 | Oleic acid (C18H34O2) | 98.6 | |
9,12,15-Octadecatrienoic acid, (Z,Z,Z)- (C18H30O2) | 82.4 | Octadecanoic acid (C18H36O2) | 1.05 | |
Octadecanoic acid (C18H36O2) | 1.11 | 9-Octadecenamide, (Z)- (C18H35NO) | 0.20 | |
cis-11-eicosenoic acid (C20H38O2) | 14.5 | |||
Methyl 18-methylnonadecanoate (C21H42O2) | 0.22 | |||
9-Octadecenamide (C18H35NO) | 0.12 | |||
13-Docosenoic acid, (Z)- (C22H42O2) | 1.27 | |||
20 Hz | Pentadecanoic acid, 14-methyl- (C16H32O2) | 0.14 | Hexadecanoic acid (C16H32O2) | 0.89 |
9,12,15-Octadecatrienoic acid, (Z,Z,Z)- (C18H30O2) | 84.5 | Oleic acid (C18H34O2) | 92.5 | |
Octadecanoic acid (C18H36O2) | 0.80 | Octadecanoic acid (C18H36O2) | 5.61 | |
cis-11-eicosenoic acid (C20H38O2) | 13.7 | cis-11-Eicosenoic acid (C20H38O2) | 0.62 | |
Methyl 18-methylnonadecanoate (C21H42O2) | 0.23 | 9-Octadecenamide, (Z)- (C18H35NO) | 0.44 | |
13-Docosenoic acid (C22H42O2) | 0.62 | |||
15 Hz | Tridecanoic acid, 12-methyl- (C14H28O2) | 2.96 | Hexadecanoic acid (C16H32O2) | 0.40 |
9,12-Octadecadienoic acid, (E,E)- (C18H32O2) | 3.06 | 9,15-Octadecadienoic acid (C18H32O2) | 0.71 | |
9,12,15-Octadecatrienoic acid, (Z,Z,Z)- (C18H30O2) | 78.7 | Oleic acid (C18H34O2) | 97.2 | |
Oleic acid (C18H34O2) | 1.47 | 6-Nonynoic acid (C9H14O2) | 0.28 | |
cis-11-eicosenoic acid (C20H38O2) | 5.00 | |||
8,11,14-Eicosatrienoic acid (C20H34O2) | 1.61 |
of 9.078 min, 9.066 min, and 9.083 min for camelina oils produced at 25 Hz, 20 Hz, and 15 Hz, respectively. The second highest peak was assigned as cis-11-eicosenoic acid at about 10.65 min. Similarly, all canola oils had a same high peak, which was assigned as oleic acid. For canola oils produced at 25 Hz, 20 Hz and 15 Hz, oleic acid was assigned at the peak eluting of 9.106 min, 9.141 min, and 9.106 min, respectively. The properties of the fatty acids, such as branching of the chain, chain length and degree of unsaturation, could influence the bio-fuel quality. Both 9,12,15-Octadecatrienoic acid, (Z,Z,Z)- and oleic acid were found suitable for hydrocarbon fuel production [
Vegetable oils contain oxygen atoms in the structure of hydrocarbons. The oxygen content influences the specific energy and the combustion [
The densities of camelina oils produced at different frequencies, shown in
The pH values of camelina and canola oils produced at different frequencies are shown in
Oils | Frequency (Hz) | C (wt%) | H (wt%) | N (wt%) | O (wt%) |
---|---|---|---|---|---|
Camelina | 25 | 78.4 ± 0.05 | 11.9 ± 0.01 | 0.40 ± 0.25 | 12.6 ± 0.17 |
Camelina | 20 | 78.4 ± 0.04 | 11.9 ± 0.01 | 0.29 ± 0 .07 | 12.4 ± 0.78 |
Camelina | 15 | 78.4 ± 0.01 | 11.8 ± 0.04 | 0.71 ± 0.21 | 11.7 ± 0.76 |
Canola | 25 | 77.7 ± 0.07 | 12.1 ± 0.01 | 0.57 ± 0.07 | 12.1 ± 0.79 |
Canola | 20 | 77.4 ± 0.06 | 12.0 ± 0.04 | 0.55 ± 0.42 | 11.2 ± 0.47 |
Canola | 15 | 77.6 ± 0.59 | 12.1 ± 0.16 | 0.51 ± 0.35 | 12.5 ± 0.62 |
Oils | Frequency (Hz) | Density (g/mL) | pH Value | Moisture (%) | Viscosity (cP) | Heating Value (MJ/Kg) |
---|---|---|---|---|---|---|
Camelina | 25 | 0.88 ± 0.04 | 5.14 ± 0.13 | 0.06 ± 0.01 | 58.9 ± 0.06 | 39.7 ± 0.06 |
Camelina | 20 | 0.89 ± 0.02 | 5.44 ± 0.38 | 0.08 ± 0.01 | 59.4 ± 0.11 | 39.4 ± 0 |
Camelina | 15 | 0.89 ± 0.01 | 5.14 ± 0.25 | 0.06 ± 0 | 59.7 ± 0.04 | 39.6 ± 0.05 |
Canola | 25 | 0.87 ± 0.02 | 3.80 ± 0.63 | 0.11 ± 0 | 76.2 ± 0.09 | 39.7 ± 0.02 |
Canola | 20 | 0.90 ± 0.01 | 3.75 ± 0.39 | 0.11 ± 0 | 76.5 ± 0.06 | 39.7 ± 0.06 |
Canola | 15 | 0.89 ± 0.01 | 4.09 ± 0.86 | 0.10 ± 0 | 77.9 ± 0.04 | 39.7 ± 0 |
of fatty acids from canola oils, there was a big difference between the pH values of these two types of oils.
The moisture content of oil samples at different frequencies is represented in
The dynamic viscosity of oils is shown in
The heating values of oils are shown in
seeds at these three frequencies, the meal yield was between 61.8% and 62.7%. For canola seeds extracted at these three frequencies, the meal yield was in a range of 61.1% - 61.5%. The oilseed meals with high yields have potential as food for animals, such as fish and cattle.
This is a preliminary study investigating the upgrading of camelina and canola oils, which were cold pressed at 15 Hz. In the present study, it is aimed to find out an effective cold press for oil extraction from camelina and canola seeds. Comparing the oil extraction from these two feed stocks using the cold press machine at the three different frequencies, the highest oil recovery was obtained for both feed stocks when the cold press ran at 15 Hz. In addition, the cold press running frequencies had slight influence on the oil properties. Therefore, the frequency of 15 Hz during the cold press processing of oilseeds was identified as the optimal processing parameter.
Oilseeds | Oil Content of Residual Meal (%) |
---|---|
Camelina | 4.90 ± 1.55 |
Canola | 7.07 ± 1.21 |
Camelina | Canola | |||
---|---|---|---|---|
Component | Area (%) | Component | Area (%) | |
Upgraded oils | 5,8,11,14-Eicosatetranoic acid (C20H24O2) | 7.28 | Hexadecanoic acid (C16H32O2) | 7.66 |
Linoleic acid ethyl ester (C20H36O2) | 24.5 | Oleic acid (C18H34O2) | 58.4 | |
10,12,14-Nonacosatriynoic acid (C29H46O2) | 7.06 | 16-Octadecenoic acid (C18H34O2) | 8.01 | |
cis-11-Eicosenoic acid (C20H38O2) | 34.3 | Methyl 11-eicosenoate (C21H42O2) | 2.07 | |
Eicosanoic acid (C20H40O2) | 11.2 | Eicosanoic acid (C20H40O2) | 2.78 | |
2,6,10,14,18,22-Tetracosahexaene, 2,6,10,15,19,23-hexamethyl-, (all-E)-, didehydro deriv. (C30H48) | 4.44 | 9-Octadecenamide, (Z)- (C18H35NO) | 17.2 | |
13-Hexacosyne (C26H50) | 2.02 | |||
Ergosta-4,22-dien-3-one (C28H44O) | 1.93 | |||
Mixed hydrocarbons | Hexadecanoic acid (C16H32O2) | 3.87 | Hexadecanoic acid (C16H32O2) | 9.08 |
Octadecanoic acid (C18H36O2) | 2.43 | Cyclododecene, (Z)- (C12H22) | 1.07 | |
2-Methyl-Z,Z-3,13-octadecadienol (C19H36O) | 0.80 | Oleic acid (C18H34O2) | 7.90 | |
Oleic acid (C18H34O2) | 17.5 | Octadecanoic acid (C18H36O2) | 3.82 | |
9-Octadecenamide, (Z)- (C18H35NO) | 1.07 | 6-Octen-1-ol, 3,7-dimethyl- (C10H20O) | 1.54 | |
9-Hexadecenoic acid, (Z)- (C16H30O2) | 3.73 | 9-Octadecenamide, (Z)- (C18H35NO) | 3.00 | |
1,5,9,13-Tetradecatetraene (C14H22) | 0.83 | Hexane, 2,3-dimethyl- (C8H18) | 73.6 | |
Hexane, 2,3-dimethyl- (C8H18) | 69.7 | |||
Distillation residues | 5,8,11,14-Eicosatetranoic acid (C20H24O2) | 5.48 | Hexadecanoic acid (C16H32O2) | 1.81 |
α-N-Nomethadol (C20H27NO) | 1.74 | Oleic acid (C18H34O2) | 91.2 | |
Linoleic acid ethyl ester (C20H36O2) | 28.8 | Octadecanoic acid (C18H36O2) | 1.60 | |
10,12,14-Nonacosatriynoic acid (C29H46O2) | 5.20 | 1,15-Hexadecadiene (C16H30) | 1.64 | |
Phorbol (C20H28O6) | 2.80 | Oleyl Alcohol (C18H36O) | 3.77 | |
cis-11-Eicosenoic acid (C20H38O2) | 16.2 | |||
Eicosanoic acid (C20H40O2) | 9.03 | |||
2,6,10,14,18,22-Tetracosahexaene, 2,6,10,15,19,23-hexamethyl-, (all-E)-, didehydro deriv. (C30H48) | 7.53 | |||
i-Propyl 5,9,17-hexacosatrenoate (C29H52O2) | 0.86 |
were cold pressed at 15 Hz. Raw camelina and canola oils were upgraded in order to improve their undesirable properties. After upgrading, there was a small decrease in density. The larger molecules were broken into smaller ones during the catalytic cracking process, which may result in the lower density. The viscosities of upgraded oils decreased greatly than raw oils. The lower viscosity made the oil easier for subsequent operating and pumping. In addition, the heating values of upgraded oils increased. However, the moisture content increased due to the water production during the upgrading process. After a treatment of distillation, the densities and viscosities of mixed hydrocarbons decreased further. Also, the moisture content of mixed hydrocarbons became
Sample | Density (g/mL) | pH Value | Moisture (%) | Viscosity (cP) | Heating Value (MJ/Kg) |
---|---|---|---|---|---|
UCMO | 0.86 ± 0 | 5.72 ± 0.06 | 0.42 ± 0.04 | 2.75 ± 0.04 | 42.6 ± 0.14 |
CMMH | 0.79 ± 0.02 | 5.25 ± 0.07 | 0.08 ± 0.01 | 0.97 ± 0 | 42.6 ± 0.03 |
CMDR | 0.87 ± 0.01 | 3.80 ± 0.17 | 0.24 ± 0.01 | 53.2 ± 0.71 | 42.8 ± 0.01 |
UCNO | 0.85 ± 0 | 3.79 ± 0.12 | 0.33 ± 0.01 | 1.34 ± 0.01 | 41.7 ± 0.25 |
CNMH | 0.82 ± 0.01 | 5.30 ± 0.14 | 0.10 ± 0.01 | 1.05 ± 0.01 | 41.9 ± 0.21 |
CNDR | 0.89 ± 0 | 3.49 ± 0.09 | 0.11 ± 0.02 | 116.5 ± 0.71 | 41.0 ± 0.04 |
lower than upgraded oils. These three properties were considered as good signs. The density, viscosity and moisture content of camelina mixed hydrocarbons have met the requirements of bio-jet fuel. The viscosity and moisture content of canola mixed hydrocarbons have met the requirements of bio-jet fuel. It indicates that the catalytic cracking method is effective to convert vegetable oils to mixed hydrocarbons, which have the potential for future bio-jet fuel production. For distillation residues, they had lower pH values and moisture content, and higher densities and viscosities than upgraded oils. In the future, the distillation residues could be treated further, such as a second catalytic cracking, for bio-fuels production.
Atypical GC analysis for the non-condensable gases produced from catalytically cracking camelina and canola oils at 500˚C is shown in
During the catalytic cracking of camelina and canola oils, the non-condensable gases contained CH4, C2H6, C2H4, C3H8, C3H6, C4H10, C5H12, H2, CO2 and CO. The production of CH4 indicated that ZSM-5-Zn-10% was able to crack and convert fatty acids into the smallest fraction of hydrocarbons. The production of H2 resulted from the dehydrogenation reaction. However, some H2 was attracted to unstable species to produce more stable products. The production of CO and CO2 were contributed to some light olefins, such as C3H6 and C2H4.
During the catalytic cracking of camelina oils, the total organic compositions, C1 to C5, occupied an area content of 12.14%. The area contents of H2, CO2, and CO were 5.25%. During the catalytic cracking of canola oils, the total organic compositions occupied an area content of 21.50%. The area contents of H2, CO2, and CO were 11.76%. It indicated that there were more decarboxylation and decarbonylation occurring during the catalytic cracking of canola oils at 500˚C. The H2 and CO generated during the catalytic cracking of camelina and canola oils have the potential for future syngas application.
The highest oil recovery for camelina and canola seeds using the cold press method is 88.2% and 84.1%, respectively. Also, more than 60% of meals are obtained during the cold press processing of these two seeds. The meals could be analyzed and treated in the future as food for animals. The density, pH value, moisture, heating value and oxygen content of both camelina and canola oils, produced at different frequencies, have no significant difference because of the relative low processing temperature during screw pressing. During the cold press of camelina and canola oilseeds, the frequency of 15 Hz is identified as the optimal processing parameter.
Camelina oils produced at three different frequencies all contain 9,12,15-Octadecatrienoic acid, (Z,Z,Z)-, which is the main component. All canola oils produced at the three different frequencies also contain the same main component, oleic acid. However, other minor compositions in camelina oils and canola oils produced at
the three different frequencies are different.
The undesired properties of camelina and canola oils are improved after the catalytic cracking to some extent. After catalytic cracking, the density and viscosity of upgraded oils decrease, and the heating value increases. After the distillation treatment, the densities and viscosities of mixed hydrocarbons decrease further. The mixed hydrocarbons, which have met the moisture and viscosity requirements of bio-jet fuel, have the potential for future bio-jet fuel production. However, more work needs to be done for the effective upgrading of non-edible vegetable oils for future bio-jet fuel production. For example, several important parameters, such as catalyst activity, reaction temperature and liquid hourly space velocity during the catalytic cracking of vegetable oils, could be considered. In addition, recycling catalysts that have been used during the oil upgrading could reduce the processing cost of converting vegetable oils to bio-jet fuels.
This study was funded by the U.S. Department of Transportation through NC Sun Grant Initiative under Grant No. SA0700149. The authors would like to thank the Chemical Analytic Lab in the Chemistry Department of South Dakota State University for the GC-MS analysis of the oil samples. All the support is gratefully acknow- ledged. However, only the authors are responsible for the opinions expressed in this paper and for any possible error.