Modeling and simulation of batch kinetics of non-edible karanja oil for biodiesel production: A mass transfer study

• Alcoholysis reaction of non edible oil to biodiesel at different temperatures.
• Modeling simulations of mass transfer, pseudo homogenous and equilibrium kinetics.
• Mixing speed and temperature influences the mass transfer resistance.
• Development of overall kinetic model.

Alcoholysis reaction for non-edible karanja vegetable oil is investigated in the presence of potassium hydroxide catalyst. The mass transfer and chemical kinetics studies were conducted in a batch reactor together with the effect of temperature on overall reaction kinetics at optimized molar ratio of oil to methanol (1:6) and 1% catalyst weight at a mixing speed of 600 rpm. The overall karanja alcoholysis reaction is modeled based on three control mechanisms, an initial mass transfer regime followed by irreversible pseudo second order and finally a reversible second order equilibrium reaction. A higher mass transfer resistance was observed as compared to that of edible oils (sunflower and rapeseed) which was attributed to the presence of impurities, especially gums that alter the fundamental physical properties of the oil. At high temperatures equilibrium reaction rate is more dominant than the irreversible pseudo homogeneous reaction, thereby making the alcoholysis reaction initially irreversible reaction controlled. The study establishes that time and temperature are the main parameters influencing the mass transfer and reaction rate, with the volumetric mass transfer coefficients as 51 × 10−3, 135 × 10−3 and 334 × 10−3 min−1 at temperatures of 35 °C, 45 °C and 55 °C respectively. The results are subsequently used to predict the mass transfer effect at lower temperatures and higher scale of operation as a function of mixing speed.

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