Calcium-carbide residue: A precursor for the synthesis of CaO–Al 2 O 3 –SiO 2 –CaSO 4 solid acid catalyst for biodiesel production using waste lard

Ajala, E. O. and Ajala, M. A. and Ajao, A. O. and Saka, H. B. and Oladipo, A. C. (2020) Calcium-carbide residue: A precursor for the synthesis of CaO–Al 2 O 3 –SiO 2 –CaSO 4 solid acid catalyst for biodiesel production using waste lard. Chemical Engineering Journal Advances, 4.

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Abstract

Calcium-carbide residue (CCR) was used as a precursor to synthesise CaO–Al 2 O 3 –SiO 2 –CaSO 4 heterogeneous acid catalyst for biodiesel production. The synthesis was through a two-step process of thermal treatment of the CCR at 500, 700, and 900 °C and sulphonation, to produce anhydrite-based solid-acid catalysts (ASACs) as ASAC 500 , ASAC 700, and ASAC 900 respectively. The CCR and ASACs were characterised using X-ray Diffraction (XRD), Scan- ning Electron Microscopy (SEM) and Brunauer–Emmet–Teller (BET). The ASACs were tested for biodiesel pro- duction using high free fatty acid waste lard. The XRD analyses show that the three catalysts consist of CaSO 4 in addition to each containing Ca 2 .62Al 9 .8Si 26 .2O 72 H 4 . 56 (ASAC 500 ), carbon atom and Ca 2 .62Al 9 .8Si 26 .2O 72 H 4 . 56 (ASAC 700 ), Ca 2 .62Al 9 .8Si 26 .2O 72 H 4 . 56 and Ca 2 Al 4 Si14O 36 •14H 2 O (ASAC 900 ). The SEM images of the ASACs show the formation of different surface morphology with active sites and improved porosity based on calcination temperatures. The BET analysis presents a surface area of 94.48 (ASAC 500 ), 90.28 (ASAC 700 ), and 98.22 m 2 /g (ASAC 900 ). The biodiesel yields obtained using 5% (w/w) catalyst, 12:1 of MeOH: Lard molar ratio, 120 min reaction time and 60 °C reaction temperature are 94.8% (ASAC 500 ), 89.2% (ASAC 700 ) and 98.9% (ASAC 900 ). The excellent performance of CaO–Al 2 O 3 –SiO 2 –CaSO 4 catalyst with the high yields of biodiesel and recyclability of seven cycles are attributed to the synergy among the calcium, aluminium, and silicon. Therefore, the CCR is a suitable precursor to synthesise a novel heterogeneous acid catalyst that is highly effective for biodiesel produc- tion.

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