Preparation Of Biodiesel From Pistacia Chinese Bunge Seed Oil And Recovery Technology Of Glycerol As By-product

In this paper, preparation of biodiesel from Piatacia chinesis Bunge seed oil with transesterification was researched, and then the recovery and refining technology of glycerol from the by-product of transesterification was studied. The main parts of this paper were as follows:(1) The national standard methods were used to analyze the physical and chemical index of Piatacia chinesis Bunge seed oil, the results showed that, the contents of moisture and volatile matter were lower than 0.02%, acid value was lower than 2mgKOH/g oil, so Piatacia chinesis Bunge seed oil can be directly used to prepare biodiesel from transesterification.(2) Through orthogonal experiments, the optimum conditions of preparation of biodissel catalyzed by KOH were obtained as follows: based on 0.01mol Piatacia chinesis Bunge seed oil, methanol/oil molar ratio was 8:1, the amount of KOH was 1.5%, reaction time was 1.5h, reaction temperature was 65℃. Under these optimum conditions, the yield of biodiesel reached 90.20%.(3) Several solid acid and base catalysts were prepared by impregnation method, admixture method, co-precipitation method, solid base K₂CO₃/Mg(Al)O was chosen as the object catalyst by comparison of their catalytic activities. And then established the appreciate preparation conditions were as follows: 30% K₂CO₃ was loaded on Mg(Al)O by admixture method, calcined at 700℃for 4h. The fresh catalyst was characterized by BET, XRD and IR. The results showed that the specific surface area, pore volume and pore diameter of K₂CO₃/Mg(Al)O were 60.06m²/g, 0.1637 cm³/g and 5.45nm respectively, there existed Mg-Al-O, CO₃^2-, et al, and the active component of K₂CO₃ was in the highly dispersed state.(4) Solid base K₂CO₃/Mg(Al)O had high catalytic activities and selectivity in preparation of biodiesel from transesterification of Piatacia chinesis Bunge seed oil. Through orthogonal experiments, the proper conditions of transesterification were got as follows: based on 0.1 mol Piatacia chinesis Bunge seed oil, methanol/oil molar ratio was 12:1, catalyst amount was 4.0%, reaction time was 2.5h, and reaction temperature was 68℃. Under these optimum conditions, the yield of biodiesel reached 99.11%. The product was characterized by IR and ¹H-NMR, the spectral graphs were verified that there existed saturated fatty acid methyl esters and unsaturated fatty acid methyl esters. The catalyst could be reused for 4 times and the yield of biodiesel was still above 96% by soxhlet extraction with ethanol (95%), dried overnight at 80℃, calcined at 700℃for 4h.(5) The recovery of glycerol from the by-product was researched, the separating and refining technology was obtained as follows: the bottom layer was first diluted with H₂O, whose usage amount of 50% based on the total amount of bottom layer, then was neutralized to pH = 4.0～5.0 by adding 50% H_SO₄, separated by centrifugal after reacted 40min at 60℃, removed H₂O, crude glycerol was obtained, crude glycerol was crystallized by ethanol [V (ethanol):W(crude glycerol)=1.5:1] at 20℃for 30min, after removed ethanol, added activated charcoal whose usage amount of 1.5% based on crude glycerol and stirred for 20min at 60℃, colorless transparent semifinished glycerol was obtained. Under the distillation temperature of 150℃and the vacuum pressure of 0.092MPa, the glutinous fluid with colorless and transparent appearance product glycerol was obtained. The purity of glycerol in the end-product was 96.19%. By detection and control, the glycerol sample was achieved the levels of the second class glycerol quality standard. By this technology the total recovery of glycerol was 77.74%.