Malaysian Journal of Analytical Sciences, Vol 27 No 4 (2023): 716 - 727

SYNTHESIS AND CHARACTERIZATION OF PALM OIL PENTAERYTHRITOL ESTER-BASED BIOLUBRICANT FROM MALAYSIA PALM OIL

(Sintesis dan Pencirian Biopelincir Berasaskan Ester Pentaeritritol Minyak Sawit

daripada Minyak Sawit Malaysia)

Nurazira Mohd Nor^1,2*, and Jumat Salimon³

¹ School of Chemistry and Environment, Faculty of Applied Sciences, Universiti Teknologi MARA, Cawangan Negeri Sembilan Kampus Kuala Pilah, 72000 Kuala Pilah, Negeri Sembilan, Malaysia

² Material, Inorganic and Oleochemistry (MaterOleo) Research Group, Faculty of Applied Sciences, Universiti Teknologi MARA, Cawangan Negeri Sembilan Kampus Kuala Pilah, 72000 Kuala Pilah, Negeri Sembilan, Malaysia

³Department of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

^*Corresponding author: nurazira@uitm.edu.my

Received: 24 March 2023; Accepted: 30 May 2023; Published: 22 August 2023

Abstract

Palm oil is one of the potential renewable resources in biolubricant production. However, the direct application of palm oil as biolubricant is restricted because of its low oxidative stability. It is due to the presence of oxidation active sites β- hydrogen in a glycerol backbone structure. This oxidative drawback can be overcome by molecule structural redesign through a chemical modification process such as esterification with polyhydric alcohol. The esterification of palm oil fatty acids (POFAs) with pentaerythritol (PE) was carried out in a mole ratio of 4.5:1, 1% of sulphuric acid, reaction temperature of 165 °C and reaction time of 7.2 hours. Gas Chromatography equipped with a Flame Ionization Detector (GC-FID) was used to determine the percentage of ester composition in palm oil pentaerythritol (POPE) ester. The structure of the POPE ester was confirmed by Fourier Transformation Infra-Red (FTIR) and proton and carbon Nuclear Magnetic Resonance (¹H-NMR and ¹³C-NMR) spectroscopy. Results showed that POPE ester has been successfully synthesized with 85% of yield and 97.4% composition of tetraesters. The existence of the ester functional group is evidenced by FTIR at 1740 cm^-1, the chemical shift of ¹H NMR at 2.29-2.33 ppm and ¹³C NMR at 173.24 ppm. Physicochemical properties analysis showed that POPE ester has oxidative stability at 189 °C, pour point at 17 °C, flash point at 300 °C and 147 viscosity index which makes POPE ester suitable to be used in many industrial lubrication applications.

Keywords: Esterification, oxidative stability, palm oil fatty acid, pentaerythritol

Abstrak

Minyak sawit merupakan salah satu sumber boleh diperbaharui yang berpotensi dalam penghasilan biopelincir. Walau bagaimanapun, penggunaan minyak sawit secara terus sebagai biopelincir adalah terhad kerana kestabilan oksidatifnya yang rendah. Ini disebabkan oleh kehadiran tapak aktif pengoksidaan β- hidrogen dalam struktur tulang belakang gliserol. Kelemahan oksidatif ini boleh diatasi dengan reka bentuk semula struktur molekul melalui proses pengubahsuaian kimia seperti pengesteran dengan alkohol polihidrik. Pengesteran asid lemak minyak sawit (POFAs) dengan pentaeritritol (PE) dijalankan dalam nisbah mol 4.5:1, 1% asid sulfurik, suhu tindak balas 165 °C dan masa tindak balas 7.2 jam. Kromatografi Gas yang dilengkapi dengan Pengesan Pengionan Nyala (GC-FID) digunakan untuk menentukan peratus komposisi ester dalam ester pentaeritritol minyak sawit (POPE). Struktur ester POPE telah disahkan oleh spektroskopi transformasi Fourier infra-merah (FTIR) dan spektroskopi resonan magnetik nukleus proton dan karbon (NMR) (¹H-NMR dan ¹³C-NMR). Keputusan menunjukkan bahawa ester POPE telah berjaya disintesis dengan 85% hasil dan 97.4% komposisi tetraester. Kewujudan kumpulan berfungsi ester dibuktikan melalui FTIR pada 1740 cm^-1, anjakan kimia ¹H NMR pada 2.29-2.33 ppm dan ¹³C NMR pada 173.24 ppm. Analisis sifat fizikokimia menunjukkan bahawa ester POPE mempunyai kestabilan oksidatif pada 189 °C, takat tuang pada 17 °C, takat kilat pada 300 °C dan indeks kelikatan 147 yang menjadikan ester POPE sesuai digunakan dalam pelbagai kegunaan pelinciran industri.

Kata kunci: Pengesteran, kestabilan oksidatif, asid lemak minyak sawit, pentaeritritol

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