TEPA与[MI][C6H2(OH)3COO]复配对小桐子生物柴油抗氧化性的影响

将四乙烯五胺（TEPA）抗氧化剂与[MI][C₆H₂(OH)₃COO]离子液体抗氧化剂进行不同比例复配,旨在研究其抑制金属设备对生物柴油的催化氧化作用以及减轻生物柴油对金属的腐蚀。本文利用Rancimat测定法检测添加复配抗氧化剂前后小桐子生物柴油氧化安定诱导期的变化,研究复配抗氧化剂对小桐子生物柴油的抗氧化性、铜片腐蚀性及铁片腐蚀性、油溶性能的影响。结果表明,复配抗氧化剂可以有效地提高生物柴油的氧化稳定性能,在1∶1复配抗氧化剂添加量为0.01%时,小桐子生物柴油诱导期为11.63h,超过了国家标准（6h）,比小桐子生物柴油的诱导期提高了473%。复配抗氧化剂对生物柴油的铜片腐蚀、铁片腐蚀都有良好的抑制作用,对生物柴油中的Cu²⁺、Fe³⁺的催化氧化也有良好的抑制效果。在TEPA与[MI][C₆H₂(OH)₃COO]复配比例为1∶1、3∶1、5∶1时,5∶1的油溶性能最佳。     

没食子酸酯类抗氧化剂对生物柴油氧化稳定性能的比较分析

以没食子酸及醇类物质为原料制备了7种不同酯基结构的没食子酸酯类抗氧化剂并进行了红外光谱表征，同时研究了7种抗氧化剂对22种生物柴油的抗氧化效果。研究结果表明：22种生物柴油的氧化稳定性能差别较大，7种不同酯基结构的没食子酸酯类抗氧化剂对22种生物柴油的抗氧化效果提升明显，其中酯基不同，对生物柴油的抗氧化效果差别较大，如添加没食子酸甲酯（a）后，小桐子生物柴油的诱导期从0.96h提高到9.79h，而添加没食子酸异丁酯（f），诱导期则从0.96h提高到5.92h，两者相差3.87h。a对生物柴油的抗氧化效果最好，在添加a后，22种生物柴油的诱导期均要大于其余6种没食子酸酯类抗氧化剂添加后的诱导期。同一种没食子酸酯类抗氧化剂对不同生物柴油的抗氧化效果有所不同，差别也较大，如a对香薷籽油生物柴油的抗氧化效果最好，使其诱导期时间从0.79 h提高到9.07 h，抗氧化效果提高了10.48倍；对棕榈油生物柴油的抗氧化效果最差，但也使其诱导期时间从7.82 h提高到55.68 h，其抗氧化效果也提高了6.12倍。支链酯基的没食子酸酯类抗氧化剂与直链酯基的没食子酸酯类抗氧化剂对生物柴油的抗氧化效果相差不大。     

TEPA/TBHQ复配对生物柴油氧化安定-腐蚀性的影响

生物柴油作为一种绿色低碳液体燃料,由于其氧化安定性差,易腐蚀金属,限制了其大规模应用。本文以小桐子生物柴油为研究对象,复配了四乙烯五胺（TEPA）/叔丁基对苯二酚（TBHQ）高效抗氧化-缓蚀剂;采用Rancimat法、扫描电子显微镜等技术探究复配抗氧化-缓蚀剂对生物柴油氧化安定性与腐蚀性能的影响规律及机制。结果表明,添加0.1‰（质量分数）比例为4∶1的复配抗氧化-缓蚀剂时可使生物柴油诱导期从4.24h提升到7.83h。同时其也有很好的缓蚀性能,使生物柴油的铜片腐蚀等级从3a降到1a;铜片表面碳元素质量分数从10.5%降为8.5%,氧元素质量分数由10%降为0。TEPA螯合铜离子,TBHQ中断生物柴油链式反应,TEPA能提供H自由基还原再生作用后的TBHQ,两者复配有良好的协同作用,可改善生物柴油氧化安定性与腐蚀性能。可为生物柴油大规模应用提供理论支撑。     

生物柴油对氟橡胶影响的研究

实验通过静态浸渍法,浸渍60天,研究菜籽油生物柴油(RME)、棉籽油生物柴油(CSME)及其与0#柴油(0PD)的调合油以及添加抗氧化剂后的生物柴油对氟橡胶腐蚀性的作用。结果表明:生物柴油与0#柴油的调合以及添加抗氧化剂都可以改善生物柴油对橡胶的腐蚀性,两者对氟橡胶的影响具有加和作用。     

生物柴油新型抗氧化剂的制备及动力学分析

以没食子酸和异丙醇为原料,吡啶硫酸氢盐离子液体为催化剂制备新型生物柴油抗氧化剂没食子酸异丙酯,通过单因素试验得到没食子酸与异丙醇催化酯化反应的最佳反应条件：反应温度85℃,反应时间4 h,醇酸物质的量比35:1,催化剂用量12%,该条件下酯化反应的转化率为89.1%。在此基础上对该催化酯化反应进行动力学分析,得出反应的表观活化能（E_a）为60.942 kJ/mol,频率因子（A）为7 060 313.404。在地沟油生物柴油中添加0.05%没食子酸异丙酯后,其氧化稳定性明显提升,诱导期从0.61 h增至6.34 h,已达到我国生物柴油国家标准（诱导期6 h）,表明没食子酸异丙酯是一种抗氧化效果很好的新型生物柴油抗氧化剂。     

固体碱法制备生物柴油及其性能

用共沉淀法制备了水滑石,焙烧后得到Mg-Al复合氧化物,以此为催化剂进行菜籽油的酯交换反应,正交实验表明该酯交换反应的小试最佳工艺条件为： 反应温度65 ℃、醇油摩尔比6∶1、反应时间为3 h,催化剂加入量为菜籽油质量的2%,脂肪酸甲酯（生物柴油）含量为95.7%.得到的生物柴油低温流动性能好,闪点高达170 ℃,氧化安定性好,主要性能指标符合0#柴油标准,可以和0#柴油以任何比例调和.     

生物柴油的抗氧化性研究

不饱和双键含量较多的生物柴油受到环境因素的影响,容易被氧化。试验中以BHA、BHT和TBHQ为抗氧化剂,分别在30℃和60℃且不通入加压空气的条件下,检测了抗氧化剂添加量分别为0.1‰、0.2‰和0.3‰时的过氧化值变化;结果表明,三种抗氧化剂对棕榈油生产的生物柴油的抗氧化效果为TBHQ>BHT>BHA。     

TBHQ、V_C、邻苯二胺复配抗氧化剂对地沟油制生物柴油抗氧化性能及抗氧化机理研究

利用TBHQ(特丁基对苯二酚)、VC(维生素C)及邻苯二胺复配,对地沟油制生物柴油的抗氧化性能进行了研究。结果表明,TBHQ、VC和邻苯二胺的复配对地沟油制生物柴油的抗氧化时间的延长具有明显的促进作用。TBHQ、VC和邻苯二胺三种抗氧化剂之间存在着很强的协同抗氧化效应。同时,在试验的基础上,还探讨了三种抗氧化剂协同抗氧化的作用机理。     

生物柴油流动性能研究

总结了生物柴油流动性能的改善方式方法。不同原料生物柴油与0#、-10#柴油复配以及添加降凝剂对生物柴油流动性能的影响。生物柴油经过超声波、磁处理、无水乙醇的掺混均等,降低粘度可以改善流动性能。     

麻疯树籽油生物柴油-0#柴油混合燃料与橡胶、塑料的兼容性

麻疯树籽油是制备生物柴油的优良原料油,由其制得的生物柴油具有良好的应用前景。为了分析和评价在运输、储存和使用过程中麻疯树籽油生物柴油与材料的相互影响,本文主要考察了4种橡胶和4种塑料分别与麻疯树籽油生物柴油-0#柴油混合燃料的相互作用及影响。试验结果表明：生物柴油混合燃料与材料接触28～56天后,其酸值和运动黏度仍满足国家标准要求;氟橡胶质量、硬度变化小,厚度的变化率小于18.00%,拉伸强度变化率小于?22.00%,有较好的耐甲酯性,而氯丁橡胶、三元乙丙橡胶及丁腈橡胶不能长期使用;生物柴油混合燃料对4种塑料厚度、质量的影响较小,其稳定性较好。     

The Effect of Natural and Synthetic Antioxidants on the Oxidative Stability of Biodiesel

A significant problem associated with the commercial acceptance of biodiesel is poor oxidative stability. This study investigates the effectiveness of various natural and synthetic antioxidants [α-tocopherol (α-T), butylated hydroxyanisole (BHA), butyl-4-methylphenol (BHT), tert-butylhydroquinone (TBHQ), 2, 5-di-tert-butyl-hydroquinone (DTBHQ), ionol BF200 (IB), propylgallate (PG), and pyrogallol (PY)] to improve the oxidative stability of soybean oil (SBO-), cottonseed oil (CSO-), poultry fat (PF-), and yellow grease (YG-) based biodiesel at the varying concentrations between 250 and 1,000 ppm. Results indicate that different types of biodiesel have different natural levels of oxidative stability, indicating that natural antioxidants play a significant role in determining oxidative stability. Moreover, PG, PY, TBHQ, BHA, BHT, DTBHQ, and IB can enhance the oxidative stability for these different types of biodiesel. Antioxidant activity increased with increasing concentration. The induction period of SBO-, CSO-, YG-, and distilled SBO-based biodiesel could be improved significantly with PY, PG and TBHQ, while PY, BHA, and BHT show the best results for PF-based biodiesel. This indicates that the effect of each antioxidant on biodiesel differs depending on different feedstock. Moreover, the effect of antioxidants on B20 and B100 was similar; suggesting that improving the oxidative stability of biodiesel can effectively increase that of biodiesel blends. The oxidative stability of untreated SBO-based biodiesel decreased with the increasing indoor and outdoor storage time, while the induction period values with adding TBHQ to SBO-based biodiesel remained constant for up to 9 months.     

The oxidative stability of biodiesel: Effects of FAME composition and antioxidant

A significant problem associated with the commercial acceptance of biodiesel is poor oxidative stability. This study investigated the effectiveness of individual and binary antioxidants to improve the oxidative stability of different types of biodiesel and distilled biodiesel. Results indicate that different types of biodiesel have different levels of oxidative stability, and that natural antioxidants and FAME composition play significant roles in determining oxidative stability. Synthetic antioxidants can enhance the oxidative stability of different types of biodiesel, and antioxidant activity increases as a function of its concentration. However, the effective activity level of antioxidant is dependent on biodiesel feedstock. Binary antioxidant formulations (TBHQ and PY) have a synergistic effect on oxidative stability of biodiesel. After long‐term storage at room temperature, the oxidative stability of untreated SBO‐based biodiesel significantly decreases as a function of time, while the addition of the antioxidant TBHQ can improve and maintain oxidative stability of biodiesel over an 18‐month period. However, the effectiveness of PY significantly decreases even after 2‐months.     

The influence of antioxidants on the oxidation stability of biodiesel

Oxidation stability of bodiesel is an important issue because FA derivatives are more sensitive to oxidative degradation than mineral fuel. Therefore, in the most recent European Specifications for biodiesel, a minimum value of 6 h for the induction period at 110°C, measured with a Rancimat instrument, is specified. To guarantee this value at the filling station, the use of additional antioxidants will be necessary. In this paper we show the influence of different synthetic and natural antioxidants on the oxidation stability, using the specified test method. Biodiesel produced from rapeseed oil, sunflower oil, used frying oil, and beef tallow, both undistilled and distilled, was investigated. The four synthetic antioxidants pyrogallol (PY), propylgallate (PG), TBHQ, and BHA produced the greatest enhancement of the induction period. These four compounds and the widely used BHT were selected for further studies at concentrations from 100 to 1000 mg/kg. The induction periods of methyl esters from rapeseed, oil, used frying oil, and tallow could be improved significantly with PY, PG, and TBHQ, whereas BHT was not very effective. A good correlation was found between the improvement of the oxidation stability and the FA composition.     

Effects of Temperature,Antioxidants, and High-Vacuum Distillation on the Oxidation of Biodiesel Derived from Waste Vegetable Oil

Biodiesel offers several environmental benefits and improvements to some fuel performance properties, but its poor oxidative stability has been a major concern. Currently, the accepted practice to improve biodiesel oxidative stability is the addition of antioxidants; numerous antioxidants have been studied but their effectiveness in inhibiting biodiesel oxidation is difficult to predict due to variation with resonance stability, solubility, reactivity, and volatility. To improve prediction efforts, this study explored the Rapid Small-Scale Oxidation Test (RSSOT) as a means to investigate how biodiesel oxidation is affected by antioxidant concentration and temperature, and compared its results with the oxidative stability index test. A weak correlation was identified due to antioxidant variation. A kinetic model expressed in temperature and induction period was developed for biodiesel before high-vacuum distillation (HVD), after HVD and also after HVD with three concentrations of propyl gallate (PG) and tert-butylhydroquinone (TBHQ) antioxidants. The approach was validated by comparing collected data on the oxidation of methyl oleate with kinetic parameters found in the literature. Antioxidant concentrations from 130–930 ppm were tested, and the results revealed that the apparent activation energy of biodiesel oxidation increases with increasing concentration of primary antioxidants and decreases during vacuum distillation. When treated with an increasing concentration (130–930 ppm) of PG and TBHQ, the apparent activation energies of a vacuum distilled biodiesel changed from 108.46 ± 4.45 to 112.72 ± 1.46 kJ·mol⁻¹ and from 77.14 ± 2.25 to 89.91 ± 2.29 kJ·mol⁻¹, respectively. These observed trends agree with both the accepted mechanism of primary oxidation of fuels and mode of action of primary antioxidants.     

Protection of biodiesel against oxidation

The importance of using synthetic antioxidants to improve oxidation stability and shelf life of biodiesel is today generally accepted. In our investigations which started early with the development of biodiesel we have looked at the course of stability, ageing of biodiesel, and the use of synthetic antioxidants. We have shown for the first time that oxidative stability of biodiesel is lower than that of the rape seed oil from which it was produced. The natural stability of biodiesel relates mainly to the content of tocopherols which survive the transesterification process. Biodiesel freed from tocopherols has no stability and will be destroyed immediately in air. Synthetic antioxidants like BHT and the newly developed stronger “Bis‐BHT” dramatically improve oxidative stability and prolong shelf life. Biodiesel rich in polyunsaturated fatty acid methyl ester needs strong antioxidants to be sufficiently protected. The class of hindered phenolic antioxidants from which the BHT and “Bis‐BHT” derive are well suited as industrial biodiesel stabilizer because of their ready availability, sufficient effectiveness and proven safety in diesel fuel. Surprisingly, none of the approved international biodiesel and biodiesel blend specifications refer to shelf life as a quality parameter. There is no definition of shelf life available, although it is well understood that biodiesel ages and loses its oxidative stability over time. We propose to consider the time span from production until the biodiesel reaches zero oxidative stability and becomes rancid and detrimental for the engine as the “shelf life” of biodiesel. From the perspective of a customer running their car on biodiesel blends, shelf life should become a more important issue.     

Experimental Design Applied for Cost and Efficiency of Antioxidants in Biodiesel

Oxidation stability is a parameter of great importance for biodiesel quality control to both producers and subsequent consumers. To maintain the quality of biodiesel, currently the most effective and economical method is the addition of antioxidants that prevent or retard the biofuel oxidation reaction. In this study, efficiency and cost of synthetic antioxidants added to B100 biodiesel from soybean oil and pork fat were evaluated, using butylhydroxyanisole (BHA), butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), in pure form or in mixtures, according to a simplex-centroid mixture experimental design. Results demonstrate an increased induction period (IP) in all trials when compared to the control sample, and TBHQ was the only antioxidant alone that met all the specification standards, while BHT and BHA alone met only the American standard specifications. The antioxidant mixture that presented the highest synergistic effect was that of TBHQ and BHA. Multi-response optimization indicated an optimum formulation containing 75 % TBHQ and 25 % BHA with an IP of 7.27 h at 110 °C and the antioxidant mixture cost of 31.31 USD, to be added for a ton of biodiesel. This simplex-centroid mixture experimental design shows an ability to be applied in the biodiesel, oils and fats industry to evaluate the oxidation stability and the occurrence of synergism between different mixtures of synthetic or natural antioxidants and their costs.     

Oxidation stability of blends of Jatropha biodiesel with diesel

Biodiesel, an ecofriendly and renewable fuel substitute for diesel has been receiving the attention of researchers around the world. Due to heavy import of edible oil, the production of biodiesel from edible oil resources in India is not advisable. Therefore it is necessary to explore non-edible seed oils, like Jatropha curcas (J. curcas) and Pongamia for biodiesel production. The oxidation stability of biodiesel from J. curcas oil (JCO) is very poor and therefore an idea is given to increase the oxidation stability of biodiesel by blending it with petro-diesel. J. curcas biodiesel (JCB), when blended with petro diesel leads to a composition having efficient and improved oxidation stability. The results have shown that blending of JCB with diesel with less than 20% (v/v) would not need any antioxidants but at the same time, need large storage space. Similarly, if the amount of diesel is decreased in the blend, it will require the addition of antioxidant but in lesser amount compared to pure JCB. For the purpose five antioxidants were used namely butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), propyl gallate (PG), and pyrogallol (PY). A B₃₀ blend (30% JCB in the blend of JCB and petro-diesel) has been tested for the same purpose. PY is found to be the best antioxidant among all five antioxidants used. The optimum amount of antioxidant (PY) for pure biodiesel tested for the present experiment is around 100 ppm while it is around 50 ppm for B₃₀ blend to maintain the international specification of oxidation stability.     

Evaluation of the Oxidative Stability of Diacylglycerol-Enriched Soybean Oil and Palm Olein Under Rancimat-Accelerated Oxidation Conditions

The oxidative stability of diacylglycerol (DAG)-enriched soybean oil and palm olein produced by partial hydrolysis using phospholipase A1 (Lecitase Ultra) and molecular distillation was investigated at 110 °C by the Rancimat method with and without addition of synthetic antioxidants. Compared with triacylglycerol oils, the DAG-enriched oils displayed lower oxidative stability due to a higher content of unsaturated fatty acids and a lower level of tocopherols. With the addition (50–200 mg/kg) of tert-butylhydroquinone (TBHQ) or ascorbyl palmitate (AP), the oxidative stability indicated by induction period (IP) of these DAG-enriched oils under the Rancimat conditions was improved. The IP of the diacylglycerol-enriched soybean oil increased from 4.21 ± 0.09 to 12.64 ± 0.42 h when 200 mg/kg of TBHQ was added, whereas the IP of the diacylglycerol-enriched palm olein increased from 5.35 ± 0.21 to 16.24 ± 0.55 h when the same level of AP was added. Addition of TBHQ, alone and in combination with AP resulted in a significant (p ≤ 0.05) increase in oxidative stability of diacylglycerol-enriched soybean oil. AP had a positive synergistic effect when used with TBHQ.