Patent Application
20080271364
The present invention relates to the production of biodiesel fuel from Balanites aegyptiaca.
Biodiesel is a biofuel consisting of a mixture of methyl or ethyl esters of long chain fatty acids produced through transesterification of oils from a biological source such as plant oils, animal fats, waste vegetable oils, or microalgae oils. It is a renewable fuel that provides a viable alternative to the petroleum-based diesel fuel. Biodiesel has been produced from a variety of vegetable oils by well-established processes starting from seeds for extraction of the oil followed by transesterification with methanol or ethanol to produce methyl or ethyl ester mixtures. Pretreatment and purification steps have been applied depending on the type and quality of the oil and the quality of the biodiesel product.
The following properties show the distinct potential of biodiesel: (i) the higher cetane number of biodiesel compared to petro-diesel indicates its potential for higher engine performance; tests have shown that biodiesel has similar or better fuel consumption, horsepower, and torque and haulage rates as conventional diesel; (ii) the superior lubricating properties of biodiesel increases functional engine efficiency; (iii) the higher flash point of biodiesel makes them safer to store; (iv) the biodiesel molecules are simple hydrocarbon chains, that contain no sulfur or aromatic substances associated with fossil fuels; (v) biodiesel contains higher amount (up to 10%) of oxygen that ensures more complete combustion of hydrocarbons; and (vi) biodiesel almost completely eliminates lifecycle carbon dioxide emissions. When compared to petro-diesel, it reduces emission of particulate matter by 40%, unburned hydrocarbons by 68%, carbon monoxide by 44%, sulphates by 100%, polycyclic aromatic hydrocarbons (PAHs) by 80%, and the carcinogenic nitrated PAHs by 90% on an average.
The biodiesel can be blended with conventional diesel fuel or used as neat fuel (100% biodiesel).
One of the disadvantages of the biodiesel is the fact that its use in cars requires some modification in the car, although many car brands are currently marketed ready for use of biodiesel. Another disadvantage is the high CFPP (cold filter plugging point) values and hence solidification and clogging of the system at low temperatures, a problem that occurs in places where the temperature decreases to around 0° C. This problem is currently solved by the addition of suitable additives.
The vegetable oil for preparation of biodiesel is obtained by extraction from seeds, usually conducted in developing countries by pressing methods, Prior to extraction, pre-treatment of the fruits is required. This procedure depends on the type of fruits yielding seeds to be fed to the crusher. The material from the crusher that contains the crushed hulls and the seeds is fed to the press extruder. The by-product meal from the extruder contains 10-20% weight of the total oil, depending on the type of extruder. Solvent extraction is applied in certain processes to improve the oil yield. The oil is normally filtered to remove fines that may be detrimental to the downstream processes for the production of the biodiesel. Additional treatment of the oil prior to its transformation to biodiesel depends on the type of oil.
The vegetable oils are triglycerides of C16 and C18 straight-chain saturated and unsaturated carboxylic acids. The specific composition of some of the oils frequently used for production of biodiesel is listed in Table 1 (14:0, lauric acid; 16:0, palmitic acid; 18:0, stearic acid; 18:1, oleic acid; 18:2, linoleic acid; 18:3, linolenic acid).
While all processes prior to transesterification are mechanical and physical processes, the transesterification reaction required to produce biodiesel is a chemical catalytic process. The reaction is reversible as illustrated schematically in Scheme 1, in which R represents the various fatty acids of the specific oil as shown in Table 1. The alcohol used for the transesterification, methanol or ethanol, and the oil, reacted in close to stoichiometric ratio, are essentially insoluble, and therefore, it is vital that proper mixing is provided to enable the reaction of the two reactants.
The free fatty acids and water, left in the oily phase after extraction, have a detrimental effect on the transesterification process. A pre-treatment of crude oil includes degumming (elimination of phospho- and glyco-lipids) with phosphoric acid and subsequent neutralization of acidity. Methanol is mostly used in current processes and its concentration in the mixture varies from 12 to 16% weight. KOH is the most efficient catalyst operating at 25-60° C. at 0.5-1.5% weight. Since the process is reversible, separation of glycerol during the process drives the reaction to completion at a high yield. Therefore, multi-stage processes with intermittent glycerol separation have been developed, and continuous separation of glycerol has also been proposed.
Several patents deal with the transesterification of vegetable oils to produce biodiesel. All of them propose various engineering solutions for efficient design of the process. WO 2004/035396 describes a very small container (a hand held device) to produce small amounts of biodiesel by a transesterification process. WO 03/087279/US 20030229238 discloses a continuous transesterification process for converting at least one triglyceride feedstock to at least one fatty-acid methyl ester product, wherein converting is carried out in a continuous, plug-flow environment at a temperature of 80-180° C. WO 2004/085579 describes a method and apparatus for producing biodiesel fuel wherein the transesterification catalyst is prepared by spraying alkyl alcohol under pressure through jets at metal hydroxide pellets until full reaction of the pellets with the alcohol. WO 03/022961 describes a batch reaction process for esterifying waste oil. WO 03/066567 discloses a continuous process for preparing an alkyl ester of fatty acids with high purity by reacting vegetable oil with a lower alcohol in the presence of alkali catalyst using a tubular reactor. U.S. Pat. No. 6,440,057 describes the reaction under dynamic turbulence in the reaction section and the transesterification is performed under pressure, wherein the pressure is reduced during transesterification.
Most of the publications disclose the transesterification of the glycerides present in vegetal oils and animal fats with methanol. Limited information on the transesterification with ethanol has been published. Bikou et al., 1999, summarized the data with various oils and presented a kinetic model for the transesterification of cotton seed oil with ethanol. Water was found to have a detrimental effect on the yield of biodiesel production. This means that anhydrous ethanol is needed, a factor that may have a negative impact on the economics of the process. A later study of transesterification of the Cynara cardunculus L. oil with ethanol demonstrated the feasibility of the process with KOH and NaOH (Encinar et al., 2002).
Recently, the oil of Balacnites roxburghii has been disclosed as suitable for the production of biodiesel (Current Science, Vol. 188, No. 9, 10 May 2005—A report on the National Seminar on Herbal Technology conducted at the M.S. University of Baroda, Vadodara, India).
It has now been found, in accordance with the present invention, that the oil or nuts of the desert Balanites aegyptiaca Del. plants is an excellent feedstock for the production of biodiesel.
Thus, in one embodiment the present invention relates to a process for producing biodiesel from Balanites aegyptiaca oil comprising reaction of the oil with a C1-C4 alkanol at a molar ratio of oil:alkanol from 1:12 to 1:3, preferably 1:8: or 1:6, at a temperature within the range of 25-100° C., preferably 25-80° C., more preferably 25-60° C., under intensive mixture conditions, in the presence of a transesterification catalyst, and allowing the transesterification to occur while removing the glycerol formed during the reaction. The biodiesel product thus obtained, comprising a mixture of C1-C4 alkyl esters of the fatty acids present in the Balanites aegyptiaca oil that may contain Balanites aegyptiaca saponins, is washed with water to remove the catalyst, and the Balanites aegyptiaca biodiesel is recovered.
In another embodiment, the present invention relates to a process for producing biodiesel from Balanites aegyptiaca crushed nuts, comprising the following steps: (i) homogenizing Balanites aegyptiaca crushed nuts with a C1-C4 alkanol, at a temperature within the range of 25-100° C., preferably 25-80° C., more preferably 25-60° C.; (ii) reacting the homogenate obtained in step (i) with a transesterification catalyst; (iii) filtering the reaction mixture product obtained in step (ii); (iv) extracting Balanites aegyptiaca biodiesel comprising a mixture of C1-C4 alkyl esters of fatty acids and optionally Balanites aegyptiaca saponins from the filtrate obtained in step (iii); (v) neutralizing the mixture product obtained in step (iv) and removing C1-C4 alkanol; (vi) drying and filtering the product obtained in step (v); (vii) recovering the Balanites aegyptiaca biodiesel; and (viii) drying the filter-cake obtained in step (iii) and extracting the dried filter-cake to recover additional Balanites aegyptiaca biodiesel left in said dried filter-cake.
In preferred embodiments, the C1-C4 alkanol is methanol or ethanol.
The present invention also relates to a method for production of the B. aegyptiaca oil from B. aegyptiaca seeds and to the biodiesel obtained from B. aegyptiaca oil or crushed nuts.
The biodiesel of the present invention can be used either alone or in blends with conventional diesel or other types of biodiesel.
The Balanites are plants of the Zygophyllaceae family, comprising 9 species and 11 intraspecific taxa. The plants used in the present invention are the species Balanites aegyptiaca Del., also known as thorn tree, Egyptian balsam and Zachum oil tree, which is one of the most common species of the genus Balanites and widely grown desert tree with a multitude of potential uses. It is found throughout the Sudano-Sahelian region of Africa and in other arid and semi arid regions of Africa, the Middle East, India and Burma. It is one of the most drought-resistance tree species in these arid regions. In Israel, B. aegyptiaca plants are found in various locations, mainly along the Jordan Valley and the Arava, where it is grown with industrial sewage water containing high salinity (˜5 dS/m) and relatively high level of heavy metals contamination.
Plant tissues from B. aegyptiaca have been used in a variety of folk medicines in Africa and Asia. Extracts from several parts of this tree have been intensively used in Africa and India for various ethnobotanical purposes. For example, Balanites extracts were shown to exhibit antifeedant, antidiabetic, molluscicide, anthelmintic and contraceptive activities. Earlier studies have shown that B. aegyptiaca contains saponins, which are amphiphilic molecules consisting of a hydrophobic sterolic aglycone linked to one or more hydrophilic glycoside chains, and most of these studies have reported that the presence of saponins is the main cause behind these activities. Besides its medicinal uses, Balanites trees are widely used as fodder, and for timber purposes.
B. aegyptiaca fruits contain a glycoside pulp (35%/fresh weight), nut (45%/fresh weight) and kernel (25%/fresh weight). The kernel contains about 45% oil. B. aegyptiaca trees usually live and remain productive for dozen of years. Recent studies carried out in Israel, clearly showed that the productivity of low quality partially purified waste saline water irrigated B. aegyptiaca trees of various origins were significantly increased to about 15,000 kg per hectare (420 trees planted in one hectare).
From the economic and ecologic points of view, it is very important that B. aegyptiaca can be cultivated and be productive in marginal and contaminated environments. This approach may support large world desertification combating campaign and produce significant amounts of green raw material for low cost alternative biofuel. Furthermore, it would support a world initiative of reclamation of industrial contaminated soil and water resources.
The B. aegyptiaca oil for use in the present invention may be produced from B. aegyptiaca seeds. The extraction process comprises the following steps: (i) washing the B. aegyptiaca fruits with water in a large rotating pan to dissolve and to remove the glycosides from the seed coats; (ii) overnight oven drying of the washed B. aegyptiaca seeds plus its heavy coat; (iii) crushing the seeds plus its heavy coats by a metal hammer crusher to a relatively homogenous powder; (iv) extruding the powder, draining the B. aegyptiaca oil out of the mixture (extraction of the oil may also be done using an organic solvent such as hexane or tetrachloroethane); and optionally (v) decantation of the oil for about least two weeks and/or centrifugation followed by vacuum filtering the B. aegyptiaca oil through a 0.4 micron membrane, if it is desired to remove the amphiphilic emulsifying particles.
The B. aegyptiaca oil extracted from fruits collected in the Ben-Gurion Balanites genetic material collection plot located in Arava rift valley has a composition of triglycerides of mainly C16:0 and C18:0 saturated and unsaturated fatty acids, with a very high content of C18:2 linoleic acid and of C18:1 oleic acid, similar to soybean, corn and cottonseed oils (see Table 1 hereinabove). Moreover, the very low free fatty acid (<0.04 meq/g) and water content (0.16-0.9%) are an excellent basis for the transesterification and no pre-treatment is needed.
The transesterification step in the processes of the present invention may be carried out in the presence of any transesterification catalyst known in the art. The catalyst may be a homogeneous catalyst such as, but not limited to, potassium hydroxide or methoxide or sodium hydroxide or methoxide, or a heterogeneous solid basic catalyst such as zeolite ETS-10. In a preferred embodiment, the transesterification catalyst is potassium hydroxide.
The alcohol used for the transesterification is a C1-C4 alkanol such as methanol, ethanol, propanol or butanol. In one preferred embodiment, the alcohol is methanol. In another preferred embodiment, the alcohol is ethanol. The ethanol may be obtained from any suitable source. For example, one of said sources may be the ethanol produced by fermentation of free sugars obtained from the glycosides removed from the Balanites seed coats (mesocarp), after extraction of the oil.
The alcohol is used in excess, for example, at a molar ratio oil:alcohol from 1:12 to 1:3, preferably 1:8: or 1:6.
The temperature of the reactions is in the range of about 25-100° C., preferably about 25-80° C., and more preferably about 25-60° C. In one embodiment, the transesterification reaction is carried out at room temperature (25° C.). In another embodiment, it is carried out at about 60° C., for example, at 63° C.
Other important factors of the process in which biodiesel is produced from B. aegyptiaca oil are the mixing of the transesterification mixture and the separation of the formed glycerol. The reaction can be carried out in a batch or tubular reactor, with proper mixing. A static mixer as known in the art may be suitable. The process is conducted in two stages with interim separation of glycerol. The biodiesel product, namely, the mixture of alkyl esters, is washed with water to remove the esterification catalyst and any other non-desired residues.
With regard to the process in which biodiesel is produced directly from B. aegyptiaca crushed nuts, the extraction of the B. aegyptiaca biodiesel from the filtrate and from the filter-cake obtained in step (iii) may be performed using any suitable organic solvent. In preferred embodiments, the extraction of the filtrate is performed using petroleum ether or ether, and the extraction of the filter-cake is performed using hexane, dichloromethane or tetrachloroethane.
Both B. aegyptiaca oil and the biodiesel of the present invention were analyzed for their fatty acid profiles and the results are shown in Table 2 below.
B. aegyptiaca
B. aegyptiaca
The diesel characteristics which are important for potential applications are: (i) Cetane number (CN), that rates the ignition quality of diesel fuels; (ii) Density, normally expressed as specific gravity, which defines the ratio of the mass of a volume of the fuel to the mass of the same volume of water; (iii) Viscosity, that measures the fluid resistance to flow; (iv) Heat of combustion (HC), which measures the available energy in the fuel; (v) Carbon residue, that correlates with the amount of carbonaceous deposits in the combustion chamber; (vi) Ash, which refers to extraneous solids that reside after combustion; (vii) Sulfur; (viii) Lubricity, that can be defined as “the property of a lubricant that causes a difference in friction under conditions of boundary lubrication when all the known factors except the lubricant itself are the same”. The lower the friction, the higher the lubricity; (ix) Iodine Value, which measures the number of double bonds in a fatty acid; (x) Distillation Curve, which is characterized by the initial temperature at which the first drop of liquid leaves the condenser and subsequent temperatures at each 10% of the liquid; (xi) Flash point (FP), which is the lowest temperature at which a combustible mixture can be formed above the liquid fuel; and (xii) Cloud point, (CP) which measures the first appearance of wax.
The biodiesel of the present invention was analyzed according to European biodiesel standard EN14214 and the results are summarized in Table 3 below, showing that all its properties met corresponding standard specifications. Furthermore, as illustrated in Example 3 hereinafter, various blends of diesel fuel containing either 5, 10 or 25% biodiesel of the present invention as well as a pure sample of this biodiesel were tested for engine performance, namely, fuel consumption, moment yield and emission profile, and the results were compared with those obtained from a pure conventional diesel fuel. As illustrated in detail in Example 3, the biodiesel of the present invention keeps the same moment of the engine as conventional diesel and reduces toxic emission gases such as CO, CO2 and hydrocarbons. In addition, fuel consumption was also slightly increased in comparison with conventional diesel, as also known for other biodiesel sources.
The industry demands amphipathic surfactant compounds to be added to fuels for improving the performance of the engine. In general saponins can reduce fuel drop size by increasing and improving atomization due to reduction of surface tension, thus improving the combustion of the fuel and maximizing the caloric value obtained. As disclosed in applicant's U.S. Provisional Applications Nos. 60/692,661, filed Jun. 22, 2005, and 60/781,332, filed Mar. 13, 2006, herewith incorporated by reference in their entirety as if fully described herein, B. aegyptiaca oil contains relatively high amount of saponins, which are expected to be found in the produced biodiesel. In particular, B. aegyptiaca saponins were found to be assembled in nanovesicles shape and are able to encapsulate hydrophilic materials. These properties further enable B. aegyptiaca saponins to trap and encapsulate water residues available in the bottom of the fuel tank, acting as a detergent and reducing the rate of corrosion. Furthermore, since these saponins are able to encapsulate toxic metals highly available in conventional diesel, adding the biodiesel of the present invention to any other diesel and/or biodiesel source will add an additional adjuvant (surfactant) highly important to the fuel efficiency and to the engine, enabling a smoother operation and improving the engine performance. It should be noted that no other biodiesel source having a high saponin content has been reported yet.
The level of B. aegyptiaca saponins expected to be found in the biodiesel of the present invention is in the range of 0.01-0.05%, and might be sufficient to improve the fuel and contribute to the engine operation and maintenance. However, in some cases there may be a need to enrich this level up to 0.1%, for example, by supplementing saponins washed from the B. aegyptiaca pulp in the very beginning of the fruit processing, as described in detail in the U.S. Provisional Applications No. 60/692,661 and No. 60/781,332 mentioned above. Since the content of saponins in B. aegyptiaca crushed nuts, containing both kernel and fibers, is relatively high, it is expected that supplement of saponins may be mainly required, if at all, in biodiesel produced from B. aegyptiaca oil. However, if needed, higher level of saponins may be obtained also in the biodiesel produced from crushed nuts by less intensive fiber separation prior to the production process.
As mentioned in the background section hereinabove, the oil of Balanites roxburghii, another common species of the genus Balanites distributed in the semi-arid regions of northern and southern India, has been recently disclosed as suitable for the production of biodiesel (Current Science, Vol. 188, No. 9, 10 May 2005—A report on the National Seminar on Herbal Technology conducted at the M.S. University of Baroda, Vadodara, India). However, as illustrated in detail in Example 4 hereinafter, although both B. aegyptiaca and B. roxburghii belong to the same genus, they are clearly genetically different. Their fruits have different morphological parameters and significantly different oil profile and composition.
In particular, the iodine number of the B. roxburghii oil is significantly lower compared to the B. aegyptiaca oil, indicating a higher degree of saturated fatty acids which is further supported by the higher viscosity of this oil. The refractive index of the B. roxburghii oil is also somewhat lower, indicating a lower degree of glycosides, which may be correlated with a higher amount of free sterols. In addition, the B. roxburghii oil contains significantly lower content of unsaponifiable matter such as saponins. Furthermore, whereas the main fatty acid in the B. aegyptiaca oil is linoleic acid followed by oleic acid, the main fatty acid in the B. roxburghii oil is oleic acid followed by linoleic acid. The relatively high level of saponins found in the B. aegyptiaca oil and expected to be found in the produced biodiesel as well seems to be of great importance, as will be explained hereinafter.
The present invention also provides a relatively fast and efficient process for the preparation of B. aegyptiaca crushed nuts, containing more than 89% of the overall oil potential, that can be used for oil extraction or directly for biodiesel production, as described in Examples 5-6 hereinafter.
The invention will now be illustrated by the following non-limiting Examples.
A mixture of 233 g of Balanites aegyptiaca oil (0.27 mol), 99.4 g (2.16 mol) absolute ethanol and 2.3 g KOH (1 wt % with respect to the Balanites aegyptiaca oil) was mechanically stirred at room temperature (25° C.) in a batch reactor for 3 h, and the two phases obtained were separated. The upper phase was washed with 50 ml of a saturated solution of NaCl and then dried over magnesium sulfate, filtered and evaporated to yield 215.8 g of the Balanites aegyptiaca biodiesel (ethyl esters) with a purity of 97%. The lower phase (51.8 g) yielded, after ethanol evaporation and extraction with hexane, an additional amount of ethyl esters (11.2 g). Hence, the overall yield of the biodiesel was 94%. The properties of the biodiesel (ethyl esters) obtained are listed in Table 4.
A mixture of 153 g (0.176 mol) of the Balanites aegyptiaca oil, 50 g absolute ethanol (1.08 mol) and 1.5 g KOH (1 wt % with respect to the Balanites aegyptiaca oil) was stirred at 63° C. for 40 min. The reaction mixture was allowed to stand for about two days, but no phase separation could be detected. After the addition of 20 ml of water, a phase separation was observed. The upper organic phase was separated and washed with 20 ml of a saturated solution of NaCl and then dried over magnesium sulfate, filtered and evaporated to yield the Balanites aegyptiaca biodiesel (ethyl esters) in 82% with a purity of 93%. The lower glycerol phase contained 33.2 g and gave, after ethanol evaporation and extraction with hexane, an additional amount of ethyl esters (7.2 g). Hence, the overall yield of the biodiesel was 86.7%.
The fuel properties of the biodiesel obtained were determined with the help of standard tests and found to be very close to diesel fuel specifications according to the biodiesel European standard, EN-14212
Methanol (6:1 molar ratio to oil) and 1.7% w/w KOH were added to 0.5 kg oil and were allowed to mix for 1 hour at room temperature. After phase separation, the lower glycerol phase was removed and the upper metlhanolic phase was washed several times with diluted phosphoric acid (pH=4.0) for neutralization of the alkali catalyst. Methanol was removed under reduced pressure to yield the B. aegyptiaca biodiesel (methyl esters).
The fatty acid profile of the B. aegyptiaca biodiesel obtained was analyzed by a GC/MS and compared to the fatty acid profiles of B. aegyptiaca oil and soy biodiesel. As shown in Table 5, four main fatty acids, namely, palmitic, linoleic, oleic (9) and stearic acids account for 98.39%, 98.85% and 97.25% of the total fatty acids found in B. aegyptiaca oil, B. aegyptiaca biodiesel and soy biodiesel, respectively. In Table 5, oleic acid (10) stands for 10-octadecenoic acid, usually present in minor quantities in almost all oils and not detected by less sensitive methods than the one used here.
B. aegyptiaca
B. aegyptiaca oil
A pure sample of the obtained biodiesel was analyzed according to European EN14214 biodiesel standard, at the official Fuel Chemical Testing Laboratory of the Technion (Israel), and as shown in Table 6, all the properties met corresponding standard specifications.
Four samples of diesel blends containing either 5%, 10%, 25% or 100% B. aegyptiaca biodiesel were tested for engine performance using a 2.5 L Ford™ diesel engine, and the results were compared with the performance of said engine consuming a pure conventional diesel. The tests were conducted at the Mechanical Engineering Department of Ben-Gurion University, Israel, and the parameters examined were fuel consumption, moment yield and emission profile (Table 7).
As expected based on the literature and shown in Table 7, B. aegyptiaca biodiesel kept the same moment of the engine as diesel, reducing toxic emission gases as CO, CO2 and hydrocarbons (HC). The only emission gas which was slightly increased, as already reported for all biodiesel sources, is NO. In addition, fuel consumption was also slightly increased in comparison with diesel, as also well reported for all biodiesel sources.
B. aegyptiaca biodiesel
B. aegyptiaca in
B. aegyptiaca and B. roxburghii are the two most common species of the genus Balanites, which belongs to the family Zygpophyllaceae and consists of 9 species and 11 intraspecific taxa. However, whereas B. aegyptiaca is found mainly throughout the Sudano-Sahelian region of Africa and in other arid and semi-arid regions of Africa and the Middle-East, the B. roxburghii is distributed in the semi-arid regions of northern and southern India.
The purpose of this study was to compare morphological parameters of the fruits of these two species, the properties and profile of the oil obtained from the fruits of each of the species, and their saponin content and composition. For the purpose of this study, B. aegyptiaca fruits were collected from the Balanites plant grown in Kibutz Samar, Arava valley, Israel, and B. roxburghii fruits were collected from Jodhpur, Rajasthan State of India. The results of this comparative study are summarized in Tables 8-14 hereinafter.
In general, the fruit yield produced by B. aegyptiaca is significantly higher than the yield of B. roxburghii trees. Moreover, recent domestication studies carried out in Ben-Gurion University (Israel) clearly showed that the productivity of low quality partially purified waste saline water irrigated B. aegyptiaca trees of various origins were significantly increased to about 15 tons per hectare (420 trees planted in one hectare), that is 2-3 times more than the productivity of non domesticated rainfed B. aegyptiaca trees. Rainfed B. roxburghii produce about 2 ton/hectare and they are not yet domesticated.
As shown in Tables 8-9, the fruits of B. roxburghii are much bigger and about 4-5 times heavier than the fruits of B. aegyptiaca, and the same for the kernels of each of the fruits, from which the majority of the oil may be obtained. In addition, the oil content in the B. roxburghii kernel is about 8-10% higher than in the B. aegyptiaca kernel.
Table 10 shows that the physical properties of the oils obtained from the kernel of these two species are significantly different. The iodine number of the B. roxburghii oil is significantly lower, indicating a lower degree of unsaturated fatty acids and a higher degree of saturated acids, and this finding is further supported by the higher oil viscosity. The refractive index of the B. roxburghii oil is also somewhat lower, indicating a lower degree of glycosides. An additional significant difference relates to the saponification value and unsaponifiable matter percent, indicating a significantly higher content of unsaponifiable matter, such as saponins, in the B. aegyptiaca oil.
Table 11 shows the considerably different fatty acid profile in each oil, indicating that although both species belong to the same genus, they are clearly genetically different. In particular, whereas the main fatty acid in B. aegyptiaca oil is linoleic acid (45.19%) followed by oleic acid (22.03%), the main fatty acid in B. roxburghii oil is oleic acid (37.49%) followed by linoleic acid (29.37%). In addition, there are clear differences between these oils in terms of minor fatty acids. The free sterol composition of these two oil is different and the overall amount of free sterol in B. aegyptiaca oil is about 25% less in comparison to B. roxburghii oil (Table 12). Since sterols in nature are components highly conjugated with glycosides, the lower amount of free sterols in the B. aegyptiaca oil may be correlated with the higher degree of glycosides in this oil, as indicated by the refractive index.
The B. roxburghii pulp (mesocarp) contains more saponins than the B. aegyptiaca pulp. However, as shown in Tables 13-14, the saponin composition of the oil obtained from each of these species is significantly different and the overall saponin content in B. aegyptiaca kernel is about 50% higher than in B. roxburghii kernel. Hence, significantly higher levels of saponin residues are expected to be found in the oil obtained from the B. aegyptiaca kernel as well as in the biodiesel produced from this oil. These saponins can reduce fuel drop size by increasing and improving atomization due to reduction of surface tension, thus improving the combustion of the fuel and maximizing the caloric value obtained. As mentioned above, B. aegyptiaca saponins were found to be assembled in nanovesicles shape and are able to trap and encapsulate hydrophilic materials. These properties further enable B. aegyptiaca saponins to trap and encapsulate water residues available in the bottom of the fuel tank, acting as a detergent, and reduce the rate of corrosion. Furthermore, since these saponins are able to encapsulate toxic metals highly available in conventional diesel, adding the biodiesel of the present invention to any other diesel and/or biodiesel source will add an additional adjuvant (surfactant) highly important to the fuel efficiency and to the engine, enabling a smoother operation and improving the engine performance
B. aegyptiaca and B. roxburghii fruit morphological parameters*
B. aegyptiaca
B. roxburghii
B. aegyptiaca and B. roxburghii percent oil content in the kernel*
B. augyptiaca
B. roxburghii
B. aegyptiaca and B. roxburghii physical properties of the oil
B. aegyptiaca
B. roxburghii
B. aegyptiaca and B. roxburghii oils fatty acid profile (%)
B. aegyptiaca
B. roxburghii
B. aegyptiaca and B. roxburghii oils sterols composition (mg/kg)
B. aegyptiaca
B. roxburghii
B. aegyptiaca and B. roxburghii oil total sapogenin content*
B. aegyptiaca
B. roxburghii
B. aegyptiaca and B. roxburghii oils major saponins composition
B. aegyptiaca
B. roxburghii
Balanites aegyptiaca fruits were processed for the extraction of oil using two different methods as described hereinbelow. Known amounts of B. aegyptiaca fruit and water were loaded onto an electrical mixer and were allowed to mix for several hours. After mesocarp washing was completed, the liquid saponin-rich extract formed was unloaded and filtered to remove exocarp particles and nuts. The nuts were washed off the saponin extract, left overnight for water drainage, and then dried for several days in a 70° C. oven. Table 15 shows the amounts of dry stone obtained in each one of the experiments performed and the mean percentage of dry stone weight out of the whole fruit weight. As shown, after removal of the pulp, about 41.5% (mean) of the whole fruit weight remained as dry matter for the next stages of oil extraction.
B. aegyptiaca fruit washing to remove the glycosidic pulp
The dry nuts were subsequently crushed using a roll-crusher to produce a crushed material with differences in particle size distribution between kernel and outer stone. This fact enabled use of different hole-size sieves in order to separate the oil-rich kernel from the outer stone. 4 mm- and 10 mm-mesh sieves were chosen, and crushed material was prepared to three degrees of purity: unsieved crushed material, 4 mm-mesh-sieved crushed material and 10 mm-mesh-sieved crushed material.
Oil was extracted from each one of the crushed materials utilizing either mechanical oil extraction or hexane solvent extraction using the Soxhlet system. The Horiba oil content analyzer (OC 350) was used in order to set a reference value for oil content in the various samples investigated. As shown in Table 16, oil percentages of 10 mm-mesh-sieved crushed material were the highest in both methods, while oil percentages for 4 mm-mesh sieved crushed material and unsieved material were second high and lowest, respectively. Furthermore, oil percentages obtained through the Soxhlet system were very close to the reference values of the Horiba oil content analyzer, while oil percentages obtained through the extrusion method tended to be significantly lower than the reference values, indicating that quiet a considerable amount of oil remains inside the press cake without being extracted.
Extraction of each Soxhlet sample was carried out twice, and the residual matter of 4 mm-mesh-sieved samples was extracted in order to determine the oil content left in the residue. The average oil percentages obtained after first and second Soxhlet extractions were 91.22±3.82% and 6.44±0.96%, respectively, and the average oil percentage obtained from 4-mesh-sieved samples residual matter was 2.40±1.06%. These data indicate that two successive Soxhlet extractions take out as nearly as 98% of the oil in these samples which accounts for the close proximity to the values received in the Horiba oil content analyzer.
In addition to the separation process described hereinabove, physical properties of B. aegyptiaca nuts were studied at the Ben-Gurion University (Israel) pilot plant in order to improve nut kernel and outer stone separation process. Dry nuts were crushed using either a hammer mill or a disk mill and were then subjected to various degrees of sieves: 8, 6.3 and 4 mm. As a result, 4 fractions were subsequently obtained, containing (i) >8 mm-mesh-sieved crushed material; (ii) >6.3 mm-mesh-sieved crushed material; (iii) >4 mm-mesh-sieved crushed material; and (iv) ≦4 mm-mesh-sieved crushed material. The latter was farther separated in an air-classifier to obtain a heavy function, containing small pieces of the kernel, and a light fraction containing the left over fine fibers.
Kernel percentage of dry nuts used for this experiment was found to be approximately 21% (w/w), and the percentage of the various crushed fractions obtained is given in Table 17.
Each one of the fractions obtained was analyzed for oil percentage and the results relating to the fractions obtained using a disk mill at the fasted feed rate are shown in Table 18. As can be clearly observed, the ≦4 mm-mesh-sieved fraction (heavy and light) that is 20.1% (w/w) of the separated B. aegyptiaca nuts material accounts for ˜89.5% of the oil potential, among them ˜77% in the heavy fraction. However, due to a relatively high cost, it was decided not to deal with the recovery of the oil of the light fraction. Furthermore, it has been unexpectedly found that a small amount of fine fibers, as exist in the light fraction, may even increase the extruder extraction efficiency and is not limiting the efficiency of biodiesel production from crushed nuts, described in Example 6 hereinafter.
Little research had been done so far to investigate transesterification of oily seeds. This Example describe two experiments in which transesterification reaction has been directly performed on B. aegyptiaca kernel-rich crushed material of fraction ≦4 mm-mesh (heavy and light) as described in Example 5 hereinabove.
In the first experiment, 2000 ml of 1% w/v methanolic NaOH solution was added to 1 kg of B. aegyptiaca crushed nuts and the mixture was allowed to react for several hours. The reaction mixture was then filtered to remove solid residues and distilled for methanol recovery. After the reaction mixture was allowed to stand overnight for phase separation, the lower glycerol phase was removed and washed with 200 ml of petroleum ether in order to extract any present methyl esters. Glycerol was removed and the petroleum ether solution was combined with the upper phase containing mainly methyl esters and NaOH. The combined solution was then washed with saturated NaCl solution, dried over magnesium sulfate and filtered to remove water and NaOH. Remaining solvent was evaporated under reduced pressure to give biodiesel methyl esters.
In the second series of experiment, the reactions were carried out in five batches designated ISEE2-6. The alcohol of choice was ethanol since it dissolves oil better than methanol. Oil percentage of fractions ISEE2-4 was found to be 28.38% and oil percentage of fractions ISEE5-6 was found to be 29.49%.
Material was grinded using a Hsiangtai electric grinder (A3), added with 200% (v/w) ethanol, homogenized at 11,000 rpm in a Polytron PT 3100 homogenizer and left for several hours incubation in room conditions. Homogenate was transferred to a 5000 ml round-bottom flask and added with 2% (w/w) KOIH. The reaction mixture was shaken at the reflux temperature in a MRC TS 400 orbital shaker for 6 hours, and then cooled and filtered. The filtrate was transferred to a separatory funnel and was added with equal volume of petroleum ether. The petroleum ether layer was washed 4 times with diluted phosphoric acid-NaCl solution for pH neutralization and ethanol removal. The petroleum ether layer was dried over sodium sulfate and filtered. Solvent was removed under reduced pressure to yield the ethyl esters. The filter cake was dried and a sample was extracted with hexane.
Samples of ethyl ester products and filter cake extractions were analyzed by gas chromatography (GC) and it was found that both reaction product and filter cake sample were turned into esters. Table 19 shows the percentage of ethyl ester yield in the reaction product and filter cake of each batch. The fatty acid ethyl ester profile of both reaction product and filter cake of each batch are shown in Table 20.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IL2006/000622 | 5/25/2006 | WO | 00 | 6/20/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60684516 | May 2005 | US |
