a review of jatropha curcas

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  • 8/3/2019 A Review of Jatropha Curcas

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    A review of Jatropha curcas: an oil plant of unfulfilled promise

    -The oil from jatropha is regarded as a potential fuel substitute. Diesel is a hydrocarbon with 810 carbon atoms per

    molecule, but jatropha oil has 1618. Thus, the nut oil is much more viscous than diesel and has a lower ignition

    quality (cetane number). For these reasons, using the oil directly in engines has not been fully tested over long

    periods. In Europe, plant oils are usually trans-esterised (with alcohol and hydroxide) to bio-diesels with properties

    similar to mineral diesel. This reduces their viscosity and increases their cetane number. However, this requires

    considerable investment and currently it is not cost-effective. Experiments have also been undertaken in Nicaragua.

    ReddyJN,RameshA.Parametricstudiesforimprovingthe performance ofa Jatropha oil-fuelled

    compressionignition engine.RenewableEnergy2006;31:19942016.

    -Retarding the injection timing with enhanced injection rate of a single cylinder, constant speed, direct injection

    diesel engine, operating on neat JCL oil, showed to improve the engine performance and emission level

    significantly

    -The measured emissions were even lower than fossil diesel. At full output HC emission level was observed to be

    532ppm against 798ppm for fossil diesel, NO level was 1163ppm against 1760ppm and smoke was reduced to 2.0

    BSU against 2.7 BSU. However, the achieved BTE with JCL oil (28.9%) was lower than with fossil diesel (32.1%)

    Biology and genetic improvement of Jatropha curcas L.: A review

    The objectives for genetic upgradation of the crop should aim at more number of female flowers or pistillate plants,

    high seed yield with high oil content, early maturity, resistance to pests and diseases, drought tolerance/resistance,

    reduced plant height and high natural ramification of branches.

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    A review on biodiesel production using catalyzed transesterification

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    When the catalyst, alcohol, and oil are mixed and agitated in a reaction vessel, a transesterification reaction will start.

    A stirred reactor is usually used as the reaction vessel for continuous alkali - catalyzed biodiesel production. Recently,

    there is an increased interest in new technologies related to mass transfer enhancement. Maeda et al. [110] and

    Thanh et al. [111] produced biodiesel from vegetable oils assisted by ultrasound which is a useful tool for

    strengthening the mass transfer of immiscible liquids. Ultrasonic irradiation causes cavitation of bubbles near the

    phase boundary between immiscible liquid phases. The asymmetric collapse of the cavitation bubbles disrupts the

    phase boundary and starts emulsification instantly. Micro jets, formed by impinging one liquid to another, lead to

    intensive mixing of the system near the phase boundary. With the use of ultrasound biodiesel can be produced

    without heating because the cavitation may lead to a localized increase in temperature at the phase boundary and

    enhance the reaction [110112]. Moreover, Wen et al. [113] fabricated a new reaction vessel Zigzag micro-channel

    reactor in recent years and found that less energy consumption for biodiesel synthesis can be achieved by using this

    reactor. Leung and Guo [28] studied the effect of operating conditions on the product yield and pointed out that

    heating the oil prior to the mixing can increase the reaction rate and hence shorten the reaction time. During this step,

    in order to speed up the reaction, mixing brings the oil, the catalyst, and the alcohol into intimate contact while the

    temperature is kept just below the boiling point of the alcohol (i.e. 64.5 _C for methanol). Normally, the reaction

    pressure is close to the atmospheric pressure to prevent the loss of alcohol, and excess alcohol is used to ensure

    total conversion of the oil to its esters. As previously mentioned, if the free fatty acid level or water level is too high, it

    may cause problems downstream with the saponification and the separation of the glycerol by-product. Therefore, the

    amount of water and free fatty acids in the feedstock oil should be monitored during the reaction. Once the

    transesterification reaction is completed, two major products exist: esters (biodiesel) and glycerol. The glycerol phase

    is much denser than the biodiesel phase and settles at the bottom of the reaction vessel, allowing it to be separated

    from the biodiesel phase. Phase separation can be observed within 10 min and can be completed within several

    hours of settling. The reaction mixture is allowed to settle in the reaction vessel in order to allow the initial separation

    of biodiesel and glycerol, or the mixture is pumped into a settling vessel. In some cases, a centrifuge may be used to

    separate the two phases [86]. Both the biodiesel and glycerol are contaminated with an unreacted catalyst, alcohol,

    and oil during the transesterification step. Soap that may be generated during the process also contaminates the

    biodiesel and glycerol phase. Schumacher [114] suggested that although the glycerol phase tends to contain a higher

    percentage of contaminants than the biodiesel, a significant amount of contaminants is also present in the biodiesel.

    Therefore, crude biodiesel needs to be purified before use..

    Biodiesel production from Jatropha curcas: a criticalreview

    Read More:http://informahealthcare.com/doi/abs/10.3109/07388551.2010.487185For example,

    oil is extracted by using a manual ram press and electric screw press in Tanzania (Eijck and Romijn, 2008). The

    main drawback of mechanical pressing is that only a small amount of oil can be extracted from the seeds. In other

    words, huge quantities of seeds would be required to obtain the desired volumes of oil. For example, 3 kg of seeds

    are needed to obtain 1 L of oil using the Sayari oil expeller of German design (Eijck and Romijn, 2008).The

    theoretical maximum amount of oil inJatropha seed is 44% (44 g oil per 100 g kernels) (Shah et al., 2005

    http://informahealthcare.com/doi/abs/10.3109/07388551.2010.487185http://informahealthcare.com/doi/abs/10.3109/07388551.2010.487185http://informahealthcare.com/doi/abs/10.3109/07388551.2010.487185http://informahealthcare.com/doi/abs/10.3109/07388551.2010.487185
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    Recently, aqueous oil extraction has emerged as a promisingtool for oil extraction from plants (Rosenthal et

    al.,2001). Aqueous oil extraction has been reported to be anenvironment-friendly oil extraction technique that has

    satisfactorilygiven higher oil yields. Ultrasonication for 5 minfollowed by aqueous enzymatic oil extraction has

    givena maximum yield of 74% oil (Shah et al., 2005). Since this method is environment-friendly, he reaction does

    not produce harmful volatile organic compounds that could lead to atmospheric pollution. However, the main

    drawback is the long process time required for the enzymes to liberate the oil bodies. Lack of commercial

    availability of particular enzymes used by the researchers is also noted as another disadvantage of this extraction

    process (Shah et al., 2005). In another method, referred to as the enzyme-assisted TPP method, a combination with

    sonication and enzyme treatment with a commercial fungal protease resulted in a yield of 97% after 2 h of reaction

    time (Shah et al., 2004). The advantages of this method include easy performance and scale up and lower reaction

    times. However, the high cost of the enzyme and high-energy input for sonication can pose economic obstacles.

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