Review of biodiesel synthesis from waste oil under elevated pressure and temperature: Phase equilibrium, reaction kinetics, process design and techno-economic study

The synthesis of biodiesel under elevated pressure and temperature could be promising technology which could result in sustainable biodiesel production, from renewable and waste streams like waste oil or used frying oil, thereby having no impact on biodiversity and the environment. This paper is comprehensive review of biodiesel synthesis from waste oil under elevated pressure and temperature: the supercritical or subcritical conditions of alcohol, with or without the use of heterogeneous catalyst. The review compromises the thermodynamic data, phase equilibria, phase composition and distribution during reaction, kinetic parameters and kinetic modeling, are presented. This type of data is necessary for process design and optimization. Process economics is analyzed and the impact of different production parameters (feedstock type, process parameters as temperature, pressure and alcohol to oil ratio, and different technology) is summarized and discussed.