两步法催化高酸价微藻油脂制备生物柴油

研究了两步法催化高酸价微藻油脂制备生物柴油的工艺条件。测定从产油栅藻培养物中提取的油脂的化学成分,发现油脂的游离脂肪酸含量分布在10%~32%,极性脂含量分布在21%~46%。以此高酸价、高极性脂含量油脂,经过酸预酯化-碱催化转酯化两步法制备生物柴油。其最优反应条件为:30%的醇加入量,1%油质量的硫酸催化反应2 h,其油脂酸价可从初始酸值的17~46 mg/g降低至2 mg/g以下;随后,在醇油物质的量之比为12:1,催化剂氢氧化钾用量为油质量的2%,65℃条件下反应30min,制备所得生物柴油中脂肪酸甲酯的质量分数可达96.6%,甘油三酯的转化效率接近100%。根据《柴油机燃料调合用生物柴油》国家标准,测定了微藻生物柴油产品的品质指标,发现其密度、运动黏度、酸价、氧化安定性等各项指标均符合国家标准(GB/T 20828-2007);热值为39.76 MJ/kg,符合欧盟生物柴油标准(EN 14214)。

Preparation of Biodiesel from High Acid Value Microalgae Lipids by a Two-step Catalyzed Process

The process conditions for biodiesel product from microalgae lipids by a two-step catalyzed process was investigated. The chemical compositions of Scenedesmus sp's lipids were analyzed. The result shows that the free fatty acid of extracts from microalgae was accounted to 10%-32%, and total polar lipid accounted to 21%-46%. The biodiesel was prepared using high acid value and high polar lipid content oil feedstock by a two-step esterification/transesterification catalyzed process. The reaction conditions were optimized and illustrated as follows: methanol dosage of 30%,sulfuric acid of 1%, reaction time for 2h, the acid value of oil can be reduced from the initial acid value of 17-46mg/g to less than 2mg/g; then molar ratio of alcohol to oil 12:1, catalyst KOH of 2% to oil weight, and reaction at a temperature of 65℃ for 30min. The content of fatty acid methyl ester reached 96.6%, and the conversion of triglyceride was near 100%. The properties of biodiesel product, such as density, kinematic viscosity, acid value, oxidation stability, etc., were analyzed with accordance to the test method Biodiesel Blend Stock for Diesel Engine Fuels. Most of properties of this product could meet specifications of the standard GB/T 20828-2007. Heat value (39.76MJ/kg) of the biodiesel could also meet EN biodiesel standards (EN 14214).