Sintesis Biopelumas Ester dari Minyak Goreng Bekas dan Pentaeritritol Menggunakan Green Catalyst/Solvent dan Optimasinya dengan Desain Box-Behnken

Abstract

Ester biolubricant has been synthesized from waste cooking oil (WCO) and pentaerythritol by using catalyst and solvent Deep Eutectic Solvents (DESs) and homogenizer. WCO refinery was by addition of 0.05% (v/v) H3PO4 and 2% (m/v) bleaching earth. The refined WCO was hydrolyzed by saponified it using ethanolic NaOH 12% followed by hydrolysis the WCO with H2SO4 25% to separate fatty acid and glycerol. Optimization of ester biolubricant synthesis has been done by using Box-Behnken Design (BBD) with fatty acid and pentaerythritol mol ratio 4:1, DESs percentage based on fatty acid weight (45%, 60%, and 75%), reaction time (30 mins, 45 mins, and 60 mins), and homogenizer stirrer velocity (3,000 rpm; 5,000 rpm; and 7,000 rpm). AV and FFA were determined by alkalimetry titration, %H2O by KF Titrino Plus instrument, composition of WCO fatty acid by GC, the change of functional group from WCO fatty acid to ester biolubricant by FT-IR Spectrophotometer, molecular weight determination of ester biolubricant by LC-MS/MS, viscosity by Viscometer Ostwald, viscosity index by SVM 3001 Viscometer, and flash point by Pensky-Martens Flash Point. Average value of AV, FFA, and %H2O were 22.49, 11.30%, and 0.08%. The WCO fatty acid average AV was 152.27. Total composition saturated fatty acid was 42.514%, unsaturated fatty acid was 55.912%, and unknown was 1.572%. The range conversion percentage of 15 ester biolubricant variation based on Box-Behnken Design were 31.90%-62.42% and the ester biolubricant conversion percentage for optimum parameter (DESs 55%, reaction time 60 mins, and stirrer velocity 3000 rpm) was 63.17%. Ester biolubricant from optimized parameter was characterized by FT-IR Spectrophotometer. The indicators for ester existence were the stretching vibration of carbonyl (C=O) absorption at 1715 cm-1 and absorption at 1170 cm-1 which originate from C-O-C ester stretching vibration. The molecular weights determination of esters was depicted as monoester pentaerythritol oleic (C18:1), monoester pentaerythritol palmitic (C16), and diester pentaerythritol caprylic-palmitic (C8-C16) by LC-MS/MS. Furthermore, the viscosity and viscosity index of ester biolubricant were 5.009 cP and 98.57, while the flash point was 91.7oC.