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Abstract
Biodiesel was produced from mustard oil utilizing transesterification with methanol, ethanol, propanol, and butanol to evaluate the characteristics of mustard biodiesel as an additive to regular diesel. Mustard oil was transesterified with alcohol at 6:1 alcohol to oil molar ratio, using KOH as a catalyst at 1 wt%. The maximum ester content achieved by this method was only 66%. Distillation was then used to purify the ester, raising the ester content to 99.8%. Alternatively, mustard oil methyl ester (MME) can be mixed with esters derived from canola oil or soybean oil to achieve an ASTM quality biodiesel. Biodiesel derived from mustard showed great potential as lubricity additive for regular diesel fuel. With an addition of 1% MME, lubricity of diesel fuel was improved by 43.7%. It is also found that methyl ester is the best lubricity additive among all esters (methyl-, ethyl-, propyl-, and butyl-ester). MME can be used at -16 °C without freezing whereas monounsaturated compounds (oleic, eicosenoic, and erucic esters) largely present in esters derived from mustard oil can tolerate -42 to -58 °C. Monounsaturated esters derived from higher alcohols such as butyl alcohol demonstrated a superior low temperature tolerance (-58 °C) as compared to that derived from lower alcohol such as methyl alcohol (-42 °C).
Keywords Biodiesel * Transesterification * Mustard oil * Diesel additives
Introduction
Conventional fossil-based fuels are not renewable and are destined to become exhausted. Furthermore, the price of these fuels tends to rise every year, which inspires the use of alternative renewable fuels. Biodiesel, commonly produced from vegetable oils such as canola oil and soybean oil [1,2], is one of the most promising renewable fuels and use of this fuel is a shift towards sustainable energy. Transesterification, a series of consecutive, reversible reactions as shown in Fig. 1 [3], is commonly used to produce biodiesel from vegetable oils. With rising concerns regarding the use of food crops as feedstock for fuel production, non-food grade oils are gaining tremendous attention from researchers around the world. High erucic acid rapeseed (HEAR) oil or mustard oil is an interesting feedstock for biodiesel production.
Mustard oil can be extracted from Brassica nigra (Black Mustard), Brassica cannata (Abyssinian Mustard), Brassica juncea (Brown, Oriental, and Leaf Mustard), Sinapis arvensis (Wild Mustard),...