Synthesis of solid catalyst from natural calcite for biodiesel production: Case study of palm kernel oil in an optimization study using definitive screening design

Abstract

A highly-active catalyst for biodiesel production was developed from calcite rock by calcination at different temperatures of 800°C (CCT800) and 900°C (CCT900). The calcination was to transform the metal carbonate in the calcite to metal oxides. The catalyst performance was evaluated through transesterification of palm kernel oil to palm kernel biodiesel (PKB), in an optimization study using a definitive screening design (DSD). The process conditions for the DSD were Methanol: oil molar ratio, reaction temperature, catalyst quantity, reaction time and calcite calcined temperature (CCT). Catalyst’s extent of reusability was investigated. The elemental composition for calcite catalyst calcined at 800°C (CCC800) and 900°C (CCC900) showed percentage composition of carbon, 21.11 and 22.84, oxygen, 40.37 and 38.78, magnesium, 15.17 and 13.34, silicon, 3.61 and 3.23, and calcium, 17.39 and 21.48, respectively which is an indication that the calcination temperature might not have affected the composition of the catalyst. The results showed that the catalyst is rich in essential ingredients (CaO and MgO) for biodiesel production. Its performance for biodiesel production gave an optimum yield of 97% PKB at optimal conditions of 6:1 (w/w) Methanol: oil molar ratio, reaction temperature 55°C, catalyst quantity 8% (w/w), reaction time 2 hours and CCT800. The catalyst was reused for eight cycles with greater activity of not <5% for PKB production. The PKB showed high-quality biodiesel as compared with the standard. Therefore, the calcite is a potential rock as a catalyst for biodiesel production.