Sains Malaysiana 43(5)(2014): 783–790

Effect of Calcination Temperatures of CaO/Nb₂O₅ Mixed Oxides Catalysts on

Biodiesel Production

(Kesan Suhu Pengkalsinan Oksida Campuran CaO/Nb₂O₅ ke atas Penghasilan Biodiesel)

Y.C. WONG¹, Y.P. TAN*², Y.H. TAUFIQ-YAP²& I. RAMLI¹

¹Centre of Excellence for Catalysis Science and Technology, Universiti Putra Malaysia

43400 Serdang, Selangor Darul Ehsan, Malaysia

²Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor Darul Ehsan, Malaysia

Received: 27 December 2012/Accepted: 26 August 2013

ABSTRACT

Calcination temperature greatly influences the total basicity and surface area of catalysts. Investigations were conducted on calcium and niobium (CaO-Nb₂O₅) mixed oxides catalysts prepared via conventional solid state method (oxides were mixed and ground in agate mortar) and calcined at different temperatures ranging from 300-800^oC for 5 h. The catalysts were then characterized by using X-ray diffraction (XRD), CO₂ temperature-programmed desorption (TPD-CO₂), Brunauer-Emmett-Teller (BET) surface area analyzer and scanning electron microscope (SEM). The formation of Ca(OH)₂ and CaCO₃ at lower calcination temperatures (< 600^oC) reduced the surface area of the catalyst and masked the basic active sites, hence lowered the total basicity of the catalyst. Besides, low surface area and total basicity were observed at higher calcination temperatures (> 600^oC), due to sintering of the fine crystals, which promotes cluster agglomeration. Thus, the optimum calcination temperature for CaO/Nb₂O₅ mixed oxides was 600^oC, which produced the largest surface area (7 m2/g) and total basicity (1301 μmol/g). The biodiesel was produced via transesterification of palm oil, methanol and the catalysts calcined at various temperatures. CaO/Nb₂O₅ mixed oxide calcined at 600^oC showed the highest biodiesel conversion (98%) with methanol/oil molar ratio of 12, 3 wt.% of catalyst, a reaction temperature of 65^oC and reaction time of 2 h.

Keywords: Biodiesel; calcium oxide; niobium oxide; palm oil; transesterification

ABSTRAK

Suhu pengkalsinan mempengaruhi jumlah luas permukaan dan jumlah kebesan pemangkin. Kajian ini telah dilakukan ke atas campuran oksida CaO/Nb₂O₅ yang disediakan dengan menggunakan kaedah konvensional keadaan pepejal (oksida dicampur dan dikisar dalam mortar batu akik) dan dikalsin pada julat suhu daripada 300-800oC selama 5 jam. Pencirian pemangkin telah dilakukan dengan menggunakan kaedah pembelauan sinar-X (XRD), mikroskop imbasan elekron (SEM), TPD-CO₂ dan analisis Brunauer-Emmett-Teller (BET). Pada suhu pengkalsinan yang lebih rendah (< 600^oC), pembentukan Ca(OH)₂ dan CaCO₃ akan menyebabkan jumlah luas permukaan pemangkin berkurang. Selain itu, suhu pengkalsinan yang lebih tinggi (> 600^oC) menyebabkan kekurangan dalam jumlah luas permukaan dan jumlah kebesan pemangkin kerana suhu pengkalsinan yang tinggi akan menyebabkan taburan pemangkin halus menjadi kelompok. Suhu pengkalsinan optimum bagi campuran oksida CaO/Nb₂O₅ adalah 600^oC dengan jumlah luas permukaan (7 m²/g) dan jumlah kebesan (1301 μmol/g). Biodiesel dihasilkan melalui transesterifikasi minyak sawit, metanol dan pemangkin yang dikalsin pada pelbagai suhu. Campuran oksida CaO/Nb₂O₅ yang dikalsin pada suhu 600^oC menunjukkan hasil biodiesel yang paling tinggi, 98% dengan nisbah metanol/ minyak kelapa sawit 12, pemangkin 3 %bt, suhu tindak balas 65^oC dan masa tindak balas selama 2 jam.

Kata kunci: Biodiesel; kalsium oksida; minyak sawit; niobium oksida; transesterifikasi

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*Corresponding author; email: yptan@upm.edu.my