Production of Biodiesel from Cottonseed Oil over Aminated Flax Fibres Catalyst: Kinetic and Thermodynamic Behaviour and Biodiesel Properties

The transesterification of cottonseed oil in the presence of methanol to fatty acid methyl ester (FAME) using flax-based fibres catalyst modified with an alkaline moiety was studied. The catalyst was prepared by radiation induced grafting (RIG) of glycidyl methacrylate (GMA) onto dignified flax fibres followed by amination with diethylamine (DEA) and treatment with NaOH solution. A maximum FAME conversion of 88.6% was obtained at 60°;C with a catalyst dosage of 2.5 wt%, an oil/methanol ratio of 1:33 and a time of 2 h. The biodiesel quality was verified by nuclear magnetic resonance (1H NMR). Kinetic analysis showed a reaction activation energy of 69.33 kJ·molˉ1 and a rate constant of 0.00349 minˉ1 indicating that the catalytic reaction was kinetically controlled. Thermodynamic analyses revealed that the reaction was reversible, non-spontaneous and endothermic with an enthalpy of 66.62 kJ·molˉ1. The obtained biodiesel showed physical and chemical characteristics complying with ASTM D6751. It can be concluded that the alkaline biopolymer catalyst prepared in the present study is a promising green candidate for biodiesel production.