超声波辅助离子液体组合物直接制备微藻生物柴油

微藻生物柴油能够解决目前植物原料生物柴油面临的耕地不足、气候变化影响产量并引起农作物价格上涨等突出问题,但传统微藻生物柴油生产过程能源与化学品消耗大,将微藻油脂的提取-酯交换耦合成一个单元,具有较大应用潜力.该研究采用小球藻、甲醇为原料,离子液体组合物作为提取剂、催化剂,超声波辅助催化微藻直接提取-酯交换制备生物柴油.考察超声波频率、超声波功率、离子液体类型、离子液体用量、反应温度、反应时间、醇油摩尔比等因素对酯交换率的影响,并与传统水浴加热机械搅拌法比较,结果表明,超声波和离子液体对生物柴油的制备有协同促进作用,离子液体具有催化、提取与增溶的作用,能较好地消除醇油界面接触,超声波的引入强化了传质传热过程,与传统加热方式水浴加热机械搅拌法相比,可以缩短酯交换反应的时间,降低反应温度,减少离子液体、甲醇的用量.离子液体BMIM]HCOO]为提取剂,微藻油脂提取率最高;酸性离子液体催化效果明显高于碱性离子液体,离子液体SO3H-BMIM]HSO4]为催化剂,微藻油脂转化率最高.当超声波功率240W,频率28kHz,甲醇用量和藻粉质量比为61:,离子液体组合物和藻粉质量比为51:,离子液体BMIM]HCOO]与SO3H-BMIM]HSO4]体积比为12:1,反应温度为50℃,超声反应时间50min条件下,生物柴油的转化率可达69.6%.该方法将离子液体溶解提取性能、催化性能及超声波的空化效应相结合,将油脂的提取与油脂的转酯化合二为一,不需先从微藻粉中提取油脂,缩短了工艺,能够实现含油微藻到生物柴油的一步转化.

Preparation of biodiesel from microalgae by direct transesterification under ultrasonic-assisted ionic liquid composite conditions

Microalgae biodiesel can solve these problems of plants materials, such as shortage of arable land, impact of climate change on production and high crop prices. But the production of microalgae biodiesel traditionally involves multiple stages, including oil extraction, purification and subsequent esterification or transesterification, and so on, which cost large quantities of energy and chemicals. The extraction of microalgae oil and the grease ester exchange in the preparation of biodiesel were coupled to a single unit, which was a biodiesel preparation method with great application potential. In this paper, biodiesel from Chlorella was prepared via in-situ ultrasonic assisted transesterification method using ionic liquids as extraction agent and catalyst. The effects of mass ratio of methanol to microalgae powder, reaction temperature, reaction time, ionic liquid type, ionic liquid dosage, ultrasonic power and frequency on the transesterification were investigated, and at the same time, this method was compared with traditional water bath heating mechanical agitation method. The results showed that ultrasonic wave and ionic liquid had synergetic effect on transesterification. Ionic liquid had the effects of catalysis, extraction and solubilization, which could eliminate the interface of methanol and oil, and also could reduce the saponification. The introduction of ultrasound enhanced the transfer process of mass transfer, which could shorten the time of the reaction of esters, decrease the reaction temperature and the dosage of ionic liquid and methanol. When the extractant was ionic liquid BMIM] HCOO], the extraction rate of microalgae was the highest. The catalytic effect of acidic ionic liquid was significantly higher than that of alkaline ionic liquids. When the catalyst was ionic liquid SO3H-BMIM]HSO4], the conversion rate of microalgae was the highest. Under the conditions of mass ratio of methanol to microalgae powder of 6:1, mass ratio of ionic liquid to microalgae powder of 5:1, ultrasonic power of 240 W, ultrasonic frequency of 28 k Hz, reaction temperature of 50 ℃ and reaction time of 50 min, the yield of fatty aid methyl ester reached 69.6%. Preparation of biodiesel from microalgae by direct transesterification under ultrasonic assisted ionic liquid conditions does not need to extract oil from microalgae powder, thus reducing the process cost, and shortening the process, which can make oil-containing microalgae transformed into biodiesel directly by esterification.