Separation of Free Fatty Acid (FFA) from High-FFA Crude Palm Oil Using Vacuum Distillation and Production of Glycerides from the FFA Distillate by Lipase-catalyzed Reaction

Abstract

This research aimed to study separation of free fatty acid (FFA) from high free fatty acid crude palm oil (HFFA-CPO) by heating under vacuum condition in a 40-liter reactor and then use the obtained FFA to produce glycerides using lipase catalyzed esterification. There were two types of HFFA-CPO used in this research, the mesocarp oil from palm oil wet milling process (called crude palm oil, CPO) and the mixed oil between mesocarp oil and kernel oil from dry milling process (called mixed crude palm oil, MCPO). Experimental separations of FFA from CPO obtained from wet milling process had 4 batches, called CPO1, CPO2, CPO3 and CPO4. Each batch had 28 liter working volume. The main fatty acid components in this CPO were palmitic (42.07%), oleic (38.86%), linoleic (7.98%) and stearic (3.95%). The average times used for each batch were 7.2 h for CPO1-CPO3 and 15 h for CPO4. Initial temperatures and setting temperatures for each batch were 27.4 °C & 230 °C, 29.5 °C & 250 °C, 30.5 °C & 250°C and 27.6 °C & 250 °C. Vacuum pressure for each batch were 20, 160, 30 and 40 mmHg, respectively. FFA in the CPO before and after separation process for each batch were 25.70% & 14.34%, 14.95% & 10.60%, 10.29% & 5.22% and 20.61% & 10.43%, respectively. The product FFAs obtained from separation for each batch were 73.37%, 76.70%, 89.28% and 51.62% %, respectively. Separations of FFA from MCPO obtained from dry milling process had 7 batches, called MCPO1, MCPO2, MCPO3, MCPO4, MCPO5, MCPO6 and MCPO7, respectively. The main fatty acid components in MCPO were oleic (40.41%), palmitic (38.63%), linoleic (10.18%) and stearic (4.27%). The average time used for each batch was 6.62 h. Initial and setting temperatures were 31.4 °C & 220°C, 27.1 °C & 240°C, 29.6 °C & 250 °C, 31.2 °C & 220 °C, 29.3 °C & 230 °C, 27.8 °C & 240 °C and 29.0 °C & 250 °C, respectively. Vacuum pressures were 20 mmHg (for MCPO1-MCPO3) and 30 mmHg (for MCPO4- MCPO7). FFA in the MCPO before and after separation process for each batch were 12.57% & 7.36%, 16.20% & 12.11%, 10.36% & 8.79%, 14.06% & 10.80%, 14.19% & 11.76%, 14.05% & 11.49% and 19.57% & 11.49%, respectively. The product FFAs obtained from separation for each batch were 98.88%, 98.87%, 79.90%, 100.00%, 99.50%, 98.21% and 99.94%, respectively. The highest percentage reduction of FFA content was obtained at distillation pressure and temperature of 20 mmHg and 220°C, respectively. Four configurations of the reactor as shown in Figure 3.1 were tasted they used the same evaporator. Thus, the heating rate and the evaporation area were the same due to the same electric heater and the same dimeter of the evaporation tank, respectively. The vacuum pressures made by both the smaller (0.75 kW) and bigger (2.20 kW) vacuum pumps were not difference. Therefore, the evaporation rate depends on vacuum pressure used and type and quality of the oil. It could be concluded configuration D is the best due to it has no heavy condenser on the top of the evaporator, easy operation. In addition, the vacuum pump of configuration D can be replaced by the smaller one to reduce energy consumption. Production of glycerides [monoglycerides (MG), diglyceride (DG) and triglycerides (TG)] using the separated FFA and crude glycerol as substrates by means of lipase catalized esterification was investigated. Beginning with screening of lipase producing bacteria for using as catalyst in glyceride production. Three bacterial strains were chosen, Bacillus subtilis, Bacillus coagulans and Psuedomonas sp. The bacterial cultivations were performed in the FFA-added nutrient broth. The lipase activities of three strains were found 0.08, 0.07, 0.07 U/ml, respectively, which were very low. To save the amount of the FFA distillate from strain cultivation for further using in glyceride production, the study of glyceride esterification began with using commercial lipase from Camlicla lipolytica, oleic acid and glycerol as catalyst and substrates, respectively. Optimization of FFA to glycerol molar ratio (1:4, 1:3, 1:2, 1:1, 2:1, 3:1 and 4:1) was firstly investigated, each ratio were done at 45°C for 24 h with lipase concentration of 300 U/g FA and shaking of 200 rpm. The ratio of 1:3 gave the best result (10.28% MG, 24.34% DG and 6.41% TG, respectively). Then the FFA to glycerol molar ratio of 1:3 was used for finding the optimal temperature. Seven temperatures (40, 45, 50, 55, 60, 65 and 70 °C) were studied and found that the temperature of 50°C gave the best result (15.51% MG, 28.51% DG and 9.16% TG, respectively). After that, the FFA to glycerol ration of 1:3 and the temperature of 50°C were used to find the optimal enzyme concentration. Five lipase concentrations (50, 100, 300, 500 and 700 U/g FA) were studied and found that at 100 U/g FA the esterification gave the best result (17.71% MG, 26.02% DG and 4.83% TG, respectively). Effect of reaction time was studied using FFA to glycerol ration of 1:3, temperature of 50°C and lipase concentration of 100 U/g FA. Four reaction times (12, 24, 36 and 48) were chosen and found that 24 h gave the best result (25.72% MG, 34.74% DG and 5.52%, respectively). Finally, the synthesis of glycerides was investigated using all above obtained optimum conditions with 4 cases of substrates for comparison: case 1 (commercial oleic & commercial glycerol), case 2 (commercial oleic & crude glycerol), case 3 (FFA distillate & commercial glycerol) and case 4 (FFA distillate & crude glycerol). Noting that the crude glycerol was from biodiesel plant. Considering DG, it was found that case 3 gave amount of DG (19.54%) higher than case 2 (1.99%) and 4 (4.68%) whereas case 1 showed the highest amount of DG (33.45%). These results represented effect of glycerol purity.