Upgrading catalytic activity of Nio/Cao/Mgo from natural limestone as catalysts for transesterification of coconut oil to biodiesel

• Main Authors: Nuni Widiarti, Nuni Widiarti, Bahruji, Hasliza, Holilah, Holilah, Yatim Lailun Ni’mah, Yatim Lailun Ni’mah, Ratna Ediati, Ratna Ediati, Eko Santoso, Eko Santoso, Abdul Jalil, Aishah, Abdul Hamid, Abdul Hamid, Didik Prasetyoko, Didik Prasetyoko
• Format: Article
• Published: Springer Science and Business Media Deutschland GmbH 2023
• Subjects: TP Chemical technology
• Online Access: http://eprints.utm.my/105502/; http://dx.doi.org/10.1007/s13399-021-01373-5

Limestone was converted to high surface area CaO/MgO catalysts via calcination-hydration-dehydration (CHD) method for transesterification of coconut oil to biodiesel. Thermal decomposition at 900°C transformed dolomite CaMg(CO3)2 to large crystallite and low surface area CaO/MgO. CHD treatment eliminated the large CaO/MgO aggregates and increased the surface area and the activity of CaO/MgO. The addition of polyethylene glycol (PEG) as surfactant during CHD reduced the CaO/MgO crystallite size to ~377 nm and enhanced the surface area (39 m2/g), the pore volume (0.0322 m3/g), and the basicity of the catalysts (7.8 mmol/g). Transesterification of coconut oil showed an increase in oil conversion from 16.45 to 49.27% when CaO/MgO was produced using PEG. Optimization studies at the variation of reaction temperatures, the ratio methanol:oil, and the amount of catalysts produced the optimum biodiesel yield of 81.76%. Impregnation with 5% NiO introduced acid-base functionality for esterification FFA to FAME, further improved biodiesel yield to 90%, and reduced the FFA yield. The kinematic, density, flash point, acid numbe,r and carbon residue of biodiesel from coconut oil were determined at 1.93 mm2/s, 0.86g/cm3, 137°C, 0.27 mg KOH/g, and 0.22% respectively, and were within the ASTM D6751 standard.