【作者】 朱丽苹；

【导师】 战风涛；

【作者基本信息】 中国石油大学 ， 有机化学， 2008， 硕士

【摘要】 对以植物油脂和甲醇等为原料进行酯交换反应制备生物柴油进行了初步研究,并研究了副产物甘油的纯化和维生素E类化合物的分析。酯交换反应采用了碱催化酯交换反应体系和酸催化酯交换反应体系,较高酸值的油脂的碱催化酯交换反应前需要进行预酯化反应以降低油脂中的游离脂肪酸含量,以保证碱催化酯交换反应的高收率及粗甘油的分离与纯化,而酸催化的酯交换反应可以免去预酯化反应过程。研究结果表明,在棕榈油的预酯化反应过程中,当催化剂硫酸的用量为棕榈油的质量的0.5%,醇油脂摩尔比为8:1,反应时间为60min,反应温度为65℃时,棕榈油的酸值由原来的22mg KOH/g降到1mg KOH/g,游离脂肪酸的转化率达到95.5%,达到了碱催化酯交换反应的要求。在碱催化酯交换反应过程中,当催化剂氢氧化钠的用量为油脂质量的0.5%,醇油脂摩尔比为8:1,反应温度为65℃,反应时间为30min,脂肪酸甲酯的产率达到96.0%(相对油脂质量)以上。碱催化酯交换反应中油脂中的水或催化剂中的水对脂肪酸甲酯的收率有较大影响,当水量达到油脂质量的1.5%(相对油脂质量)时,脂肪酸甲酯的收率在90.0%以下,这是碱催化酯水解的结果。为了进一步降低催化剂用量及醇油脂比,采用反应过程中分离粗甘油,未反应完全的油脂再次酯交换(两次酯交换)的方法,结果表明当总催化剂用量为1.0%,醇油脂摩尔比20:1,反应时间为4h,反应温度为150℃,脂肪酸甲酯的收率可达到95.3%。研究了硫酸催化酯交换反应过程中油脂的酸值对脂肪酸甲酯收率的影响,结果表明,当油脂的酸值为120mg KOH/g,两次酯交换反应,在总催化剂用量为1.0%,醇油脂摩尔比20:1,反应时间为4h,反应温度为150℃,脂肪酸甲酯的收率可达到98.4 %,这说明硫酸催化制备生物柴油可以采用价廉的较高酸值的油脂。初步研究了硫酸催化酯交换反应中的钢片腐蚀问题,在125℃时,硫酸含量0.35%的丁醇溶液(400mL)中,304不锈钢的腐蚀速率为1.1mm/a。采用GC/MS技术分析了由棉籽油和棕榈油为原料得到的脂肪酸甲酯,结果表明,精棉籽油脂肪酸甲酯主要为棕榈酸甲酯、亚油酸甲酯和油酸甲酯,含量分别为22.23%、50.18%和18.09%。棕榈油脂肪酸甲酯主要为棕榈酸甲酯、油酸甲酯和硬脂酸甲酯,含量分别为40.30%、50.07%和7.02%。采用GC/MS技术分析了两种来自植物油的商品维生素E,其中来自天津亿能化工试剂开发中心的维生素E主要是生育酚类占71.80%,生育三烯酚类占7.81%,角鲨烯占2.97%;而来自棕榈油(马来西亚)的维生素E主要是生育烯酚/生育三烯酚类占53.27%,生育酚类占15.86%,角鲨烯占9.56%,因此来自棕榈油的维生素E具有更好的清除生物体内自由基的作用。更多还原

【Abstract】 The preparation of biodiesel from vegetable oil by transesterification with methanol, the purification of the glycerin and the identification of vitamin E homologues were studied. Transesterification were carried out by the acid catalysis and alkali catalysis. Vegetable oil with higher acid number should be esterified before the transesterification by alkali catalysis to reduce the content of free fatty acids, which is favorable to achieve high yield of fatty acid methyl ester and for purification of glycerin. The esterification and transesterification could be carried out simultaneously in the preparation of biodiesel by acid catalysis with higher vegetable oils. The results showed that the conversion rate of free fatty acids is 95.5% in the esterification of palm oil when the quantity of catalyst (H2SO4), the mol ratio of methanol to the oil, reaction time and reaction temperature were 0.5% (based on the oil), 8:1, 60 minutes and 65℃, respectively, and the acid number of the palm oil was reduced from 22mg KOH/g to 1mg KOH/g, which is appropriate for transesterification by alkali catalysis.For the transesterification of vegetable oils, the yield of fatty acid methyl ester could be achieved to more than 96.0% when the quantity of catalyst (NaOH), the mol ratio of methanol to the oil, reaction time and reaction temperature were 0.5% (based on the oil), 8:1, 30 minutes and 65℃, respectively. The content of water in the transesterification by alkali catalysis influenced the yield of fatty acid methyl ester seriously, and the yield of fatty acid methyl ester was reduced to 90.0% below when the content of water in the oils or the catalyst is 1.5%(based on the oils), which is the causation of hydrolysis of esters by the alkali catalysis.For reducing the quantity of catalyst and the mol ratio of methanol to the oil remarkably, the glycerin was separated and the oils were transesterified continuously, which was called di-transesterification. The results showed that the yield of fatty acid methyl ester could be achieved to 95.3% when the total quantity of catalyst (H2SO4), the total mol ratio of methanol to the oil, reaction time and reaction temperature were 1.0% (based on the oil), 20:1, 4 hours and 150℃, respectively.The effect of acid number of the oils to the yield of fatty acid methyl ester was studied. The results showed that the yield of fatty acid methyl ester of the di-transesterification was achieved to 98.4 %, in which the acid number of the oil, total quantity of catalyst (H2SO4), the total mol ratio of methanol to the oil, reaction time and reaction temperature were120mg KOH/g, 1.0% (based on the oil), 20:1, 4 hours and 150℃, respectively. And this showed that the inexpensive vegetable oils with higher acid number could be used to prepare biodiesel by H2SO4 catalysis. The corrosion was studied preparatively in the transesterification by H2SO4 catalysis and the results showed that the corrosion rate was 1.1mm per year for 304# stainless steel in 0.35% H2SO4- butanol solution at 125℃and 12 hours.The GC/MS technology was used to identify the compositions of the biodiesels from palm oil and cottonseed oil. The results indicated that the compositions of the biodiesel from cottonseed oil were mainly methyl cetylate, methyl linoleate and methyl oleate, which the percentages were 22.23%, 50.18% and 18.09%, respectively. And the main compositions of the biodiesel from palm oil were methyl cetylate, methyl oleate and methyl stearate, which the percentages were 40.3%, 50.07% and 7.02%, respectively.Two kinds of commercial vitamin E were analyzed by GC/MS technology. The compositions of the vitamin E (Tianjin) were mainly tocopherols, tocotrienol and squalene, which the percentages were 71.80%, 7.81% and 2.97%, respectvely. Otherwise the compositions of the vitamin E from palm oils (Malaysia) were mainly tocoenol/tocopherols, tocopherols and squalene, which the percentages were 53.27%, 5.86% and 9.56%, respectively. And so the vitamin E from palm oils was more effective to eliminate the radicals in bodys.更多还原