Abstract
The synthesis of biodiesel from Jatropha curcas by transesterification is kinetically controlled. It depends on the molar ratio, reaction time, and temperature, as well as the catalyst nature and quantity. The aim of this study was to explore the transesterification of low-cost, inedible J. curcas seed oil utilizing both homogenous (potassium hydroxide; KOH) and heterogenous (calcium oxide; CaO) catalysis. In this effort, two steps were used. First, free fatty acids in J. curcas oil were reduced from 12.4 to less than 1 wt.% with sulfuric acid-catalyzed pretreatment. Transesterification subsequently converted the oil to biodiesel. The yield of fatty acid methyl esters was optimized by varying the reaction time, catalyst load, and methanol-to-oil molar ratio. A maximum yield of 96% was obtained from CaO nanoparticles at a reaction time of 5.5 h with 4 wt.% of the catalyst and an 18:1 methanol-to-oil molar ratio. The optimum conditions for KOH were a molar ratio of methanol to oil of 9:1, 5 wt.% of the catalyst, and a reaction time of 3.5 h, and this returned a yield of 92%. The fuel properties of the optimized biodiesel were within the limits specified in ASTM D6751, the American biodiesel standard. In addition, the 5% blends in petroleum diesel were within the ranges prescribed in ASTM D975, the American diesel fuel standard.
Highlights
We investigated the alkaline catalysts calcium oxide (CaO) and potassium hydroxide (KOH) for transesterification of low-cost, inedible jatropha oil and compared their catalytic performances under various conditions
The heterogeneous CaO nano-catalyst was prepared by calcination, while the homogenous KOH catalyst was pretreated under high temperature but below its melting point
The lower yield of KOH was attributed to the increased basicity that promoted unwanted hydrolysis and saponification reactions
Summary
Energy demands have been consistently increasing worldwide alongside the increasing human population and industrialization. Petroleum, and coal (fossil fuels) are the traditional and common non-renewable sources of energy, and these sources are depleting rapidly due to huge energy consumption. The potential shortage of energy in the future and rising prices of non-renewable fuels have prompted interest in alternative renewable energy sources and energy security [1,2,3,4]. Fossil fuels have many environmental issues, cause atmospheric pollution, and are a major contributor to anthropogenic greenhouse gas emissions. Combustion of fossil fuels emits COx , SOx , NOx , hydrocarbons, and many carcinogenic compounds into the atmosphere that may lead
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