废弃油脂甘油酯化降酸过程中的甘油聚合研究

基于甘油酯化降酸的优势和降酸过程甘油聚合的问题,开展了废弃油脂甘油酯化降酸过程中甘油聚合的研究。考察了反应温度、甘油用量、催化剂种类、催化剂用量对甘油聚合的影响,并分析了聚甘油的聚合度。结果表明:反应温度越高、甘油与脂肪酸摩尔比越大,降酸速率越快,甘油聚合率越高,在反应温度220℃、甘油与脂肪酸摩尔比1∶1时甘油聚合率约为33.8%;聚甘油主要为二聚甘油;甘油酯化过程引入锌基催化剂,不仅提高降酸速率,缩短反应时间,还能降低反应温度、减少甘油的聚合,从而提高副产物甘油的回收率;与催化剂Zn Cl_2、Zn(Ac)_2相比,催化剂Zn O效果最好,在Zn O用量0.3%、反应温度180℃、甘油与脂肪酸摩尔比1∶1时甘油聚合率可降至约13%。研究结果将有助于进一步优化甘油酯化降酸工艺,为甘油酯化耦合碱催化酯交换法制备生物柴油技术的设计提供参考。     

废弃油脂甘油酯化降酸及制备生物柴油

甘油酯化是高酸值油脂降酸值的有效方法。以地沟油为原料进行甘油酯化反应,考察了反应温度、甘油用量对甘油酯化反应的影响,并将甘油酯化后的地沟油与甲醇进行酯交换反应,回收粗甘油纯化后重新用于甘油酯化反应,考察了回收甘油的利用效果。结果表明,甘油酯化过程的最佳工艺条件为反应温度240℃,搅拌速率500 r/min,甘油与脂肪酸摩尔比1.1∶1,反应时间3 h。在最佳条件下,地沟油酸值(KOH)可降至0.5 mg/g以下,纯化后的甘油重复利用效果与新鲜甘油相当。     

高酸值油酯化反应的研究

以高酸值棕榈油和麻疯果油为原料,初步研究了不同酸值原料油在不同甲醇用量条件下的硫酸催化酯化情况及甲醇与原料油中游离脂肪酸摩尔比值(醇酸比值)对酯化反应的影响。结果表明:醇酸比值影响反应的主要原因是整个酯化反应受传质扩散影响明显,催化酯化过程中甲醇的最佳用量取决于原料油酸值的大小,其与酸值大小的关系为y=3.488x0.174(y为甲醇与游离脂肪酸的摩尔比值,x为原料油酸值)。     

填充床反应器制备富含甘油二酯米糠油

以高酸值米糠油为原料,采用填充床反应器酶法制备富合甘油二酯米糠油。考察了脂肪酶种类、分子筛添加量、底物摩尔比、进料流速、反应温度对甘油二酯含量和游离脂肪酸含量的影响。得到较优的反应条件为:固定化脂肪酶Lipozyme RM IM为实验用酶,甘油为酯化剂,甘油与高酸值米糠油摩尔比5∶1,进料流速0.2 m L/min,反应温度65℃,固定化脂肪酶添加量10 g,分子筛添加量10 g。在较优条件下,产物中甘油二酯含量和游离脂肪酸含量分别为37.67%和3.10%。     

FeCl_3改性蒙脱土催化合成油酸甲酯的研究

用氯化铁改性蒙脱土制备了改性催化剂FeCl_3–蒙脱土,并以此为催化剂催化油酸与甲醇酯化合成油酸甲酯。通过XRD、FT–IR等方法对催化剂进行了表征。考察了催化剂用量、油醇摩尔比、反应温度、反应时间等因素对转化率的影响。研究结果表明:在催化剂用量5 wt%、油醇摩尔比1∶10、反应温度70℃的条件下反应3 h,油酸转化率为71.5%,且该催化剂适用于各种游离脂肪酸酯化反应及高酸值油脂酯化降酸反应。     

高酸值非粮植物油酯化降酸工艺研究

对甲苯磺酸作为酸催化剂,催化高酸值非粮植物油与甲醇进行预酯化反应。研究油醇摩尔比、催化剂用量、反应时间和反应温度对酯化降酸的影响,优化了工艺条件。结果表明,在油醇摩尔比1∶30、催化剂用量8 mg、70oC条件下反应50 min,高酸值麻疯树油、千金子油预酯化率分别为96.0%、96.2%,表明原料降酸效果较好,可满足后期生物柴油的制备。     

制备生物柴油用高FFA花椒籽油的酸催化降酸

以花椒籽油为原料,采用硫酸为酸催化剂,探讨了醇油摩尔比、反应时间及降酸工艺对降酸效果的影响。当催化剂H2SO4为油重的2％,反应温度60℃,反应时间1h,试验结果表明,随着醇油比的增加,酸值逐渐降低。当摩尔比为20～35：1时,一次酸酯化降酸后,体系最终酸值均小于2mgKOH／g,可以满足制备生物柴油的要求。当醇油摩尔比为25：1,催化剂H2SO4为油重的2％,反应温度60℃,试验结果表明,反应初期酸值下降较快,反应1h后酸值降为1．35mgKOH／g。试验结果还证实,二次降酸能有效将花椒籽油酸值降至2mgKOH／g以下。     

米糠油酯化脱酸

乙米糠油中含有较高的游离脂肪酸,而且含有较一般毛油高的甘油一酸酯和甘油二酸酯。毛米糠油经过脱胶和脱蜡以后,在高温和真空条件下,利用米糠油中原有的甘油一酸酯和甘油二酸酯,或加入甘油,与游离脂肪酸发生酯化反应,可以有效地降低米糠油的酸值,并增加中性油的数量。酯化脱酸能量消耗较高,可适用于米糠油的脱酸。     

胰脂肪酶催化樟树籽仁油和甘油合成中碳链单甘油酯

采用胰脂肪酶催化樟树籽仁油与甘油反应合成中碳链单甘油酯,通过单因素试验和正交试验,研究了反应时间、加酶量、醇油摩尔比、反应初始加水量、反应温度对产物中中碳链单甘油酯含量的影响。结果表明,胰脂肪酶催化樟树籽仁油(10 mL)与甘油反应合成中碳链单甘油酯的适宜条件为:反应温度47℃,加酶量220 mg,醇油摩尔比4.3∶1,反应初始加水量35μL,反应时间30 h。在此反应条件下,产物中中碳链单甘油酯的含量为53.42%±0.05%。     

菊粉酸降解动力学研究

通过考察温度、溶液pH值及水分含量对菊粉酸降解的影响,探索菊粉酸水解规律。结果表明:菊粉水溶液在pH 5.0～7.0、温度低于100℃时具有良好的稳定性;但当pH值低于4.0时,菊粉出现明显的水解反应。菊粉溶液在不同温度和pH值下的酸降解动力学表明,其水解反应遵循一级反应动力学方程。利用菊粉凝胶特性考察水分含量与菊粉酸降解的关系,发现相同pH值(pH=3)条件下,水分含量越高,菊粉降解速率越快,凝胶中菊粉降解速率低于菊粉水溶液降解速率。     

偏甘油酯脂肪酶Lipase G50催化酯化法制备甘油二酯

利用偏甘油酯脂肪酶Lipase G50催化甘油和脂肪酸酯化反应合成甘油二酯.探讨了酶加量、底物摩尔比、反应温度及加水量对酯化反应的影响.结果表明最佳反应条件为:脂肪酶Lipase G50加量为350 U/g,甘油和脂肪酸的摩尔比5∶1,加水量为底物总质量的5％,反应温度30℃,反应时间24h.在最佳反应条件下脂肪酸的酯化率为75.02％,甘油二酯的含量达到44.74％,产物中没有甘油三酯生成.     

均匀设计在酯化樟树籽油制备单甘酯中的应用

以樟树籽油为原料、对甲基苯磺酸为催化剂,通过酯化将樟树籽油中的游离脂肪酸转化为单甘酯。采用均匀设计和偏最小二乘回归法,以酯化率(Y1)和单甘酯的含量(Y2)的最大值为优化目标,考察反应温度、催化剂的用量、醇油物质的量配比、反应时间对樟树籽油酯化反应的影响。对两个试验指标进行回归建模,模型拟合的决定系数分别为0.9801、0.9739。最优目标函数值Y1、Y2 分别为98.2%、12.2%,实测值分别为95.6%、14.4%,最佳酯化反应条件为反应温度132℃、催化剂的用量3.5%(油重)、醇油物质的量配比1.8:1、反应时间2h。     

Optimisation of enzymatic esterification of soybean oil deodoriser distillate

The enzymatic esterification of free fatty acids from soybean oil deodoriser distillate with ethanol, catalysed by immobilised fungal lipase, was studied. The extent of conversion of free fatty acids to ethyl esters was optimised using a response surface methodology obtained through a second‐order factorial experimental design. The variables studied were reaction temperature (30–70 °C), enzyme concentration (7–23%) and ethanol/free fatty acid molar ratio (0.3–3.7:1). The optimal reaction conditions achieved were temperature from 46.4 to 53.6 °C, enzyme concentration from 13.6 to 16.5% and ethanol/free fatty acid molar ratio from 1.7 to 2.3:1, with conversions above 88%. No significant tocopherol losses were observed during the process. In conclusion, enzymatic fatty acid esterification was shown to be a technically viable process. © 2001 Society of Chemical Industry     

Change in glyceride composition of olive pomace oil during enzymatic esterification

Enzymatic esterification of free fatty acids of olive pomace oil with glycerol was investigated. The esterification reaction was carried out in the absence and presence of glycerol (glycerol to free fatty acids (FFA) molar ratio of 1/3 and 1/6). In the absence of glycerol, the FFA concentration decreased from 32 to 21% while the triglyceride concentration increased from 33 to 40% after of 8 h of reaction time. The most significant decrease in FFAs and increase in triglycerides was observed at the limiting concentration of glycerol (glycerol to FFA molar ratio of 1/3). The FFA concentration decreased to 2.5% and the triglyceride concentration increased up to 78%. The change in both FFA and triglyceride concentrations was found to be statistically significant (P < 0.05).     

生物柴油的双脂酶催化生产工艺研究

以菜籽酸化油为原料,研究两种脂酶顺序催化制备生物柴油的生产工艺。结果表明,固相化细菌A007脂酶催化甘油三酯(TAG)水解的最适条件为:含水量40%、脂酶用量100 U/g、反应温度30℃、反应时间12 h,此时TAG水解率和游离脂肪酸(FFA)含量分别为93.3%和90.1%;在催化FFA甲酯化过程中,固相化Candida antarctica脂酶在FFA与甲醇摩尔比为1∶5时可达到最佳效果;在第二次甲酯化时,加入甘油有利于提高FFA酯化率,经过24 h反应,可将总酯化率从无甘油时的96.9%提高到98.6%。该工艺可操作性强,具有较好的应用价值。     

Optimisation of Novozym‐435‐catalysed esterification of fatty acid mixture for the preparation of medium‐ and long‐chain triglycerides (MLCT) in solvent‐free medium

Novozym‐435‐catalysed esterification of caprylic acid, capric acid and oleic acid with glycerol for the synthesis of medium‐ and long‐chain triglycerides (MLCT) in vacuum and solvent‐free system was investigated in this study. Response surface methodology with a three‐level, four‐factorial design was applied to optimise the enzymatic esterification for the synthesis of MLCT. The optimum conditions were as follows: reaction temperature 90 °C, 4.80 wt% enzyme load (relative to the weight of total substrates) and substrate molar ratio (fatty acids/glycerol) of 3:1 and 12.37 h. Under above‐mentioned conditions, Triglycerides (TG) yield, MLCT and the residual free fatty acids (FFA) content in the product were 93.54%, 72.19% and 4.21%, respectively. The content of caprylic acid, capric acid and long‐chain fatty acids of TG was 24%, 10% and 66%, respectively. Novozym 435 in the study showed no selectivity for the different fatty acids and also could be used 14 times without obvious loss of enzyme activity.     

响应面优化脂肪酶催化合成中长碳链甘三酯

采用响应面设计对脂肪酶Novozym 435在无溶剂体系中催化甘油和中长碳链脂肪酸(辛酸、癸酸和油酸混合物)酯化反应合成中长碳链甘三酯进行了研究.研究发现:反应温度、加酶量和反应时间对中长碳链甘三酯得率具有显著性影响(P＜0.05),而底物摩尔比(脂肪酸与甘油摩尔比)对中长碳链甘三酯得率不具有显著性影响.优化得到的最佳条件为:反应温度90℃,加酶量6.5％(以脂肪酸和甘油的总质量计),底物摩尔比3.5∶1,反应时间12.97 h.在此条件下,平均甘三酯得率为78.5％;产品中甘三酯、甘二酯、甘一酯和游离脂肪酸含量分别为85.6％、0.3％、0.1％和14.0％;产品甘三酯中辛酸、癸酸和长碳链脂肪酸含量分别为25.4％、10.7％和63.9％,与目标中长碳链甘三酯产品指标基本一致.     

酶法全酯化合成富含EPA/DHA甘油酯工艺研究

以富含EPA/DHA的脂肪酸为底物,采用两步酶法合成富含EPA和DHA的甘油酯。首先,以T1脂肪酶为催化剂催化富含EPA/DHA的脂肪酸和甘油反应;在最优条件为:反应温度40℃,水分添加量为底物混合物的3%、甘油与脂肪酸摩尔比3∶1和酶添加量50 U/g底物混合物时,富含EPA/DHA的脂肪酸的转化率达到62%以上,此时产物中甘油三酯、甘油二酯、甘油单酯的质量分数分别为10.52%、38.15%、25.64%。将游离酶催化酯化反应产物中的油相回收,利用自制的固定化CALB(LipozymeCALB L固定于环氧树脂ECR8285上)为催化剂,在真空条件下继续催化未反应的脂肪酸与偏甘油酯(甘油单酯和甘油二酯)继续酯化反应12 h,此时产物中甘油三酯、甘油二酯和甘油单酯的质量分数分别达到38.34%、51.02%、10.63%,没有检测到脂肪酸的存在。     

Lipase-catalyzed process in an anhydrous medium with enzyme reutilization to produce biodiesel with low acid value

One major problem in the lipase-catalyzed production of biodiesel or fatty acid methyl esters (FAME) is the high acidity of the product, mainly caused by water presence, which produces parallel hydrolysis and esterification reactions instead of transesterification to FAME. Therefore, the use of reaction medium in absence of water (anhydrous medium) was investigated in a lipase-catalyzed process to improve FAME yield and final product quality. FAME production catalyzed by Novozym 435 was carried out using waste frying oil (WFO) as raw material, methanol as acyl acceptor, and 3 Å molecular sieves to extract the water. The anhydrous conditions allowed the esterification of free fatty acids (FFA) from feedstock at the initial reaction time. However, after the initial esterification process, water absence avoided the consecutives reactions of hydrolysis and esterification, producing FAME mainly by transesterification. Using this anhydrous medium, a decreasing in both the acid value and the diglycerides content in the product were observed, simultaneously improving FAME yield. Enzyme reuse in the anhydrous medium was also studied. The use of the moderate polar solvent tert-butanol as a co-solvent led to a stable catalysis using Novozym 435 even after 17 successive cycles of FAME production under anhydrous conditions. These results indicate that a lipase-catalyzed process in an anhydrous medium coupled with enzyme reuse would be suitable for biodiesel production, promoting the use of oils of different origin as raw materials.     

酶法合成共轭亚油酸单甘酯的研究

采用脂肪酶G50(来源于Penicillium camembertii)作为生物催化剂,催化共轭亚油酸(CLA)和甘油酯化生成共轭亚油酸单甘酯(MAG)。研究了在无溶剂体系中,底物摩尔比、酶加量、体系含水量、反应温度和反应时间对产物中MAG含量和CLA酯化率的影响。结果表明,最佳反应条件为:底物摩尔比n(甘油)∶n(CLA)=4∶1,加酶量300U/g(基于反应底物总质量),体系含水量1%,反应温度15℃,反应时间24h。在最佳反应条件下,CLA的酯化率达到84.98%,MAG的含量为68.40%,共轭亚油酸双甘酯(DAG)含量为16.58%。通过分析产物的脂肪酸组成,发现Penicillium脂肪酶G50对CLA异构体没有拆分效果。