The impact of antioxidants on biodiesel oxidation stability

The potential of 11 different synthetic phenolic antioxidants to improve the oxidation stability of biodiesel prepared from different feedstocks was investigated. Measurements of oxidation stability were carried out according to the European biodiesel specifications with a Rancimat instrument at 110 °C. At antioxidant concentrations of 1000 mg/kg, an improvement in oxidation stability could be achieved with all antioxidants tested. Especially the antioxidants DTBHQ, IONOX 220, Vulkanox ZKF, Vulkanox BKF, and Baynox were able to significantly improve the oxidation stability, leading to stabilization factors between 1.89 and 13.07. Variation of antioxidant concentrations between 100 and 1000 mg/kg showed that the efficiency of the antioxidants varied depending on the different types of biodiesel. When used as additives, Baynox showed good effects on rapeseed oil methyl ester (RME) stability, DBHQ on recycled cooking oil methyl ester (RCOME) stability, Vulkanox BKF on distilled RCOME (DRCOME) stability, and IONOX 220 on tallow methyl ester (TME) stability. Evaluation of the influence of the antioxidants on critical biodiesel fuel parameters showed no negative impacts on viscosities, densities, carbon residues, CFPP, and sulphated ash contents of the different biodiesel samples. However, in terms of acid values, a noticeable increase could be observed at antioxidant levels of 1000 mg/kg. At lower antioxidant concentrations, this increase was much lower and the values remained within the required limits.     

Effects of oxidized biodiesel on formation of particulate matter and NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> from diesel engine

A test was conducted to investigate the effect of pure biodiesel without additives on formation of particulate matter (PM) and nitrogen oxide (NOx) in the exhaust gas of a diesel engine. Pure biodiesel from waste cooking oil without adding any additive was used. The biodiesel was oxidized at 110 °C for 10 days and blended with commercial automobile diesel oil distributed in the market as a testing fuel. Blended fuels were produced by adding 10% of oxidized biodiesel and un-oxidized biodiesel to automobile diesel oil, respectively. Material properties such as density, kinematic viscosity, oxidation stability, and cetane number were tested. Emission tests were conducted using a large diesel engine of direct injection type, inline six-cylinder, 4 stroke, turbocharger and intercooler. The oxidized and unoxidized biodiesel blends did not show any difference in density and kinematic viscosity. The oxidation stability of the oxidized biodiesel blends was lower than that of the unoxidized biodiesel blends. In the emission test, the two blends showed almost no difference in the total number of concentration of the micro-particles, and also showed almost no difference in particle size distribution such as nucleation mode and accumulation mode. On the other hand, the oxidized biodiesel blends showed less PM and NOx emission than the unoxidized biodiesel blends.     

Antagonism between cloud point and cold filter plugging point depressants in a diesel fuel

Differential scanning calorimetry (d.s.c.) and thermomicroscopy were used to provide a better understanding of the antagonistic effect on cold filter plugging point (CFPP) when cloud point depressants (CPD) and CFPP additives are mixed into a diesel fuel. It is shown that the CFPP achieved by using only CFPP additive can be attained in the presence of CPD if a small, homogeneous size of crystals of paraffins is again obtained. Two ways are proposed to obtain this result: modification of the chemical structure of the CPD, and optimization of the concentration of each component of the blend. In either case a decrease in efficiency of the CPD is observed, but the antagonism disappears. It is possible to predict the efficiency of CFPP additives in a diesel fuel containing CPD by evaluation of T_g of the hydrocarbon matrix and determination of the percentage of light n-alkanes by d.s.c.     

Engine performance, exhaust emissions and combustion characteristics of a CI engine fuelled with croton megalocarpus methyl ester with antioxidant

The use of biodiesel as a substitute for petroleum-based diesel has become of great interest for the reasons of combating the destruction of the environment, the price of petroleum-based diesel and dependency on foreign energy sources. But for practical feasibility of biodiesel, antioxidants are added to increase the oxidation stability during long term storage. It is quite possible that these additives may affect the clean burning characteristics of biodiesel. This study investigated the experimental effects of antioxidants on the oxidation stability, engine performance, exhaust emissions and combustion characteristics of a four cylinder turbocharged direct injection (TDI) diesel engine fuelled with biodiesel from croton megalocarpus oil. The three synthetic antioxidants evaluated its effectiveness on oxidation stability of croton oil methyl ester (COME) were 1, 2, 3 tri-hydroxy benzene (Pyrogallol, PY), 3, 4, 5-tri hydroxy benzoic acid (Propyl Gallate, PG) and 2-tert butyl-4-methoxy phenol (Butylated Hydroxyanisole, BHA). The fuel sample tested in TDI diesel engine include pure croton biodiesel (B100), croton biodiesel dosed with 1000 ppm of an effective antioxidant (B100 + PY1000), B20 (20% croton biodiesel and 80% mineral diesel) and diesel fuel which was used as base fuel. The result showed that the effectiveness of the antioxidants was in the order of PY > PG > BHA. The brake specific fuel consumption (BSFC) of biodiesel fuel with antioxidants decreased more than that of biodiesel fuel without antioxidants, but both were higher than that of diesel. Antioxidants had few effects on the exhaust emissions of a diesel engine running on biodiesel. Combustion characteristics in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends PY and PG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage. Overall, the biodiesel derived from croton megalocarpus oil can be utilized as partial substitute for mineral diesel.     

Evaluation of the oxidation stability of diesel/biodiesel blends

Biodiesel is an alternative fuel derived from vegetable oils, animal fats and used frying oils. Due to its chemical structure, it is more susceptible to oxidation or autoxidation during long-term storage compared to petroleum diesel fuel. One of the major technical issues regarding the biodiesel blends with diesel fuel is the oxidation stability of the final blend, which is, nowadays, of particularly high concern due to the introduction of ultra low sulphur diesel, in most parts of the EU. This study examined the factors influencing the stability of several biodiesel blends with low and ultra low sulphur automotive diesel fuels. The aim of this paper was to evaluate the impact of biodiesel source material and biodiesel concentration in diesel fuel, on the stability of the final blend. Moreover, the effects of certain characteristics of the base diesels, such as sulphur content and the presence of cracked stocks, on the oxidation stability are discussed.     

Improving the cold flow properties of biodiesel from waste cooking oil by ternary blending with bio-based alcohols and diesel from direct coal liquefaction

The utilization and popularization of biodiesel are always limited by its poor cold flow properties. Both bio-based alcohol and diesel from direct coal liquefaction (DDCL) has potential to enhance the cold flow properties of biodiesel. In this study, ternary blends of waste cooking oil biodiesel (BWCO) with DDCL and bio-based ethanol (ET) or 1-butanol (BT) were conducted to improve the cold flow properties of biodiesel. The pour point (PP), cold filter plugging point (CFPP), and cloud point (CP) of BWCO-ET, BWCO-BT, and BWCO-DDCL binary blends, and BWCO-ET-DDCL and BWCO-BT-DDCL ternary blends were comparatively assessed. Ternary phase diagrams were also applied to analyze the blending effect of the three components on the cold flow properties of biodiesel. Results showed that both DDCL, ET, and BT can remarkably enhance the cold flow properties of BWCO. When the ternary blends contain 20 vol.% BWCO and less than 40 vol.% ET or BT, DDCL together with ET or BT exerted positive effects on enhancing the low-temperature flow properties of BWCO, especially on the CP and CFPP. For ternary blends in 20:10:70 blending ratio, BWCO-BT-DDCL exhibited the lowest PP, CFPP, and CP of −23, −19, and −17°C, respectively. The crystallization behavior and crystal morphology of blended fuels are also observed via a polarizing optical microscope, and find that DDCL together with BT in biodiesel can effectively retard the aggregation of large crystals and inhibit crystals growth.     

On maximizing biodiesel mixing ratio based on final product specifications

A model predicting 12 properties of diesel-biodiesel mixtures was developed. This was based on existing correlations capable of providing quality characteristics for the mixtures. The model was also used to maximize the biodiesel fraction in the diesel-biodiesel mixtures, while taking into consideration all product quality specifications as they are defined by Greek Legislation. The properties examined were density, viscosity, cloud point, pour point, volatility at temperatures 250 °C, 350 °C and 360 °C, cetane index, cetane number, sulfur, water, higher heating value, flash point and cold filter plugging point (CFPP). The model was evaluated for mixtures between two diesel types (normal diesel and Shell extra diesel) and four biodiesel types (i.e. biodiesel produced from different vegetable oils). The model was developed in MATLAB and the corresponding biodiesel optimization studies were carried out with the MATLAB's optimization toolbox.     

Influence of waste cooking oil biodiesel on the nanostructure and volatility of particles emitted by a direct-injection diesel engine

To reduce air pollution and the reliance on fossil fuel, biodiesel has been widely investigated as an alternative fuel for diesel engines. The purpose of this study is to investigate the influence of waste cooking oil (WCO) biodiesel on the physical properties and the oxidation reactivity of the particles emitted by a diesel engine operating on WCO biodiesel as the main fuel. Experiments were conducted on a direct-injection diesel engine fueled with biodiesel, B75 (75% biodiesel and 25% diesel on volume basis, v/v), B50, B20, and diesel fuel, at five engine loads and at an engine speed of 1920 rev/min. Particulate samples were collected to analyze the particulate nanostructure, volatility, and oxidation characteristics. Biodiesel or low-load operation leads to smaller primary particles and more disordered nanostructures having shorter and more curved graphene layers. It can be found that particles from biodiesel, blended fuels, or low-load operation have higher volatile mass fractions and faster oxidation reaction rates than particles from diesel or heavy-load operation. The higher oxidation reaction rates are due mainly to the smaller particle size, the more disordered nanostructure, and the higher volatile mass fraction. It is also found that changes in primary particle size and particulate nanostructure are not directly proportional to the biodiesel content, while changes in particulate volatility and particulate oxidation reactivity are proportional to the biodiesel content. The use of biodiesel can enhance particulate oxidation reactivity and the regeneration of soot particles in an after-treatment device.

Copyright © 2016 American Association for Aerosol Research     

生物柴油低温流动改进剂的制备及其降滤效果评价

为降低大豆油生物柴油的冷滤点,合成了马来酸酐-丙烯酰胺-苯乙烯醇解衍生物（AAS）以及助剂环己醇脂肪酸酯（CF）,并对其进行红外表征。通过正交实验,优化了三元共聚物（AAS）的工艺条件,同时考察了自制AAS分别与助剂CF以及德国蜡晶分散剂的复配效果。实验结果表明,合成AAS的最佳工艺条件为：单体配比2：1.5：0.75,引发剂（BPO）用量1.5%,催化剂加量1.0%,共聚温度75℃,共聚时间5 h,醇解时间3 h,酐醇比7：12。当AAS添加量为0.3%时,可使大豆油生物柴油冷滤点降低4℃。与助剂CF以1：1质量配比复配可使大豆油生物柴油冷滤点降低6℃,并可使菜籽油生物柴油降低5℃。     

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.     

Development of multifunctional additives based on vegetable oils for high quality diesel and biodiesel

The increasing qualitative requirements of the modern diesel fuels can be satisfied by applying environmental friendly blending components and additive-packages having high performance level.The aim of our experimental work was to produce multifunctional additives based on rapeseed oil methyl ester by applying radical initiation. This process is more environmental friendly and energy economic respect to the widely used thermal synthesis method for the production of polyisobutylene (PIB)-succinimide type additives. Beside, our aim was to use raw materials originated from partly renewable source to meet the biodegradability requirements. These synthesized additives showed same or even better detergent–dispersant properties compared to the traditional PIB-succinimides and also provided corrosion inhibiting and lubricity improving effects when applied in diesel fuel, 5% biodiesel containing diesel fuel and 100% biodiesel.     

An optimum biodiesel combination: Jatropha and soapnut oil biodiesel blends

Jatropha (Jatropha curcas) and soapnut (Sapindus mukorossi) oils are considered potential non-edible oil feedstocks for biodiesel production and present complementary fuel properties. Apparently, the poor oxidation stability of jatropha oil biodiesel and the high cold filter plugging point of soapnut oil biodiesel can be successfully improved to satisfy all biodiesel specifications at an optimum blending ratio. The optimum biodiesel combination was further blended with diesel at various volumetric percentages to evaluate the variations of fuel properties. The biodiesel–diesel blends up to B40 would show the satisfactory fuel properties.     

Thermal analysis of alternative diesel fuels from vegetable oils

The relatively poor cold-flow properties of monoalkyl esters of vegetable oils and animal fats (biodiesel) present a major obstacle to their development as alternative fuels and extenders for combustion in direct injection compressionignition (diesel) engines. In this work, differential scanning calorimetry (DSC) heating and cooling curves of methyl soyate (SME), methyl tallowate (TME), SME/TME admixtures, and winterized SME were analyzed. Completion of melt, crystallization onset (Onset), and other temperatures corresponding to melting and freezing peaks were correlated to predict cloud point (CP), pour point (PP), cold filter plugging point (CFPP), and low-temperature flow test (LTFT) data. Effects of treating methyl esters with cold-flow improvers were examined. Low-temperature flow properties of biodiesel may be accurately inferred from subambient DSC analyses of high-melting or freezing (β-form) peaks. The temperature of maximal heat flow for freezing peaks gave the best accuracy for predicting CP, PP, and CFPP, while freezing point gave the best accuracy for predicting LTFT. Onset also gave good correlations with respect to predicting PP, CFPP, and LTFT. Cooling scan parameters were more reliable than heating scan parameters. Presented at the 88th American Oil Chemists’ Society’s Annual Meeting & Expo, Seattle, Washington, May 11–14, 1997.     

Some aspects of biodiesel oxidative stability

Biodiesel, an “alternative” diesel fuel derived from vegetable oils, animals fats or used frying oils, largely consists of the mono-alkyl esters of the fatty acids comprising these feedstocks. One of the major technical issue facing biodiesel is its susceptibility to oxidation upon exposure to oxygen in ambient air. This susceptibility is due to its content of unsaturated fatty acid chains, especially those with bis-allylic methylene moieties. Oxidation of fatty acid chains is a complex process that proceeds by a variety of mechanisms. Besides the presence of air, various other factors influence the oxidation process of biodiesel including presence of light, elevated temperature, extraneous materials such as metals which may be even present in the container material, peroxides, and antioxidants, as well as the size of the surface area between biodiesel and air. Approaches to improving biodiesel oxidative stability include the deliberate addition of antioxidants or modification of the fatty ester profile. This article discusses some factors influencing biodiesel oxidative stability and their interaction. Resulting approaches to improving this property of biodiesel are related to these factors and the corresponding mechanisms.     

Improving the low-temperature properties of alternative diesel fuels: Vegetable oil-derived methyl esters

This work explores near-term approaches for improving the low-temperature properties of triglyceride oil-derived fuels for direct-injection compression-ignition (diesel) engines. Methyl esters from transesterified soybean oil were evaluated as a neat fuel and in blends with petroleum middle distillates. Winterization showed that the cloud point (CP) of methyl soyate may be reduced to −16°C. Twelve cold-flow additives marketed for distillates were tested by standard petroleum methodologies, including CP, pour point (PP), kinematic viscosity, cold filter plugging point (CFPP), and low-temperature flow test (LTFT). Results showed that additive treatment significantly improves the PP of distillate/methyl ester blends; however, additives do not greatly affect CP or viscosity. Both CFPP and LTFT were nearly linear functions of CP, a result that compares well with earlier studies with untreated distillate/methyl ester blends. In particular, additives proved capable of reducing LTFT of neart methyl esters by 5–6°C. This work supports earlier research on the low-temperature properties; that is, approaches for improving the cold flow of methyl ester-based diesel fuels should continue to focus on reducing CP.     

EsMOVS柴油降凝剂的研制

对柴油降凝剂ＥｓＭＯＶＳ的合成、用途、使用条件、影响因素等作了阐述。此降凝剂对抚顺石油二厂－１０＃柴油的纯降凝度是１８℃，冷滤点纯降低度是９℃。对其它柴油也有一定的降凝助滤效果。     

AMSV-a柴油低温流动改进剂的研制

介绍了柴油低温流动改进剂AMSV-a的合成和降凝助滤性能。该剂是以丙烯酸酯、马来酸酐、苯乙烯、醋酸乙烯酯(量比为4∶1∶0 5∶1)为原料,以甲苯为溶剂,以过氧化苯甲酰(用量5 0g/mol共聚单体)为引发剂,恒温80℃聚合6h,得四元共聚物(AMSV),再以对甲苯磺酸为催化剂(用量20g/mol共聚单体),用高碳胺〔n(酐)∶n(胺)=1∶1 5〕进行胺解制得。该剂对大庆-10#柴油的纯降凝度可达25℃,冷滤点降低可达16℃;对胜利0#柴油的纯降凝度可达23℃,冷滤点降低可达14℃;对东明5#柴油的纯降凝度可达20℃,冷滤点降低可达11℃;对濮阳10#柴油的纯降凝度可达17℃,冷滤点降低可达9℃。     

生物柴油低温流动性能研究进展

生物柴油是清洁可再生燃料,越来越多的国家开始研究和使用生物柴油替代石化柴油。然而生物柴油凝点和冷滤点很高,低温情况下容易结晶析出,堵塞发动机的管道和过滤器而无法正常使用。如何降低生物柴油凝点和冷滤点成为生物柴油研究的一个十分重要的课题,本文综述了目前国内外改进生物柴油低温流动性能的研究进展,生物柴油降凝剂及其降凝机理研究。     

Rapid Models for Predicting the Low‐Temperature Behavior of Diesel

The cold filtration plugging point (CFPP) is the method most commonly applied to characterize the low‐temperature behavior of diesel and its components. However, this method is time‐consuming and does not have good repeatability, especially for samples with very low CFPP values like kerosene, light cycle oil, etc. Three new models for CFPP prediction were developed and compared: a combined density and distillation curve, differential scanning calorimetry, and near‐infrared. A set of 133 samples of diesel components were used to create the models, containing streams from different sources and levels of treatment. A further 28 diesel samples were used to validate and compare the models. All three models not only were faster than the standard method but also were found to be in good agreement with CFPP values. Each model has its own particular advantages suiting it to a particular type of diesel sample and stage of the diesel production process.     

Mitigation of NOx emissions from a jatropha biodiesel fuelled DI diesel engine using antioxidant additives

Biodiesel offers cleaner combustion over conventional diesel fuel including reduced particulate matter, carbon monoxide and unburned hydrocarbon emissions. However, several studies point to slight increase in NO_x emissions (about 10%) for biodiesel fuel compared with conventional diesel fuel. Use of antioxidant additives is one of the most cost-effective ways to mitigate the formation of prompt NO_x. In this study, the effect of antioxidant additives on NO_x emissions in a jatropha methyl ester fuelled direct injection diesel engine have been investigated experimentally and compared. A survey of literature regarding the causes of biodiesel NO_x effect and control strategies is presented. The antioxidant additives L-ascorbic acid, α tocopherol acetate, butylated hydroxytoluene, p-phenylenediamine and ethylenediamine were tested on computerised Kirloskar-make 4 stroke water cooled single cylinder diesel engine of 4.4 kW rated power. Results showed that antioxidants considered in the present study are effective in controlling the NO_x emissions of biodiesel fuelled diesel engines. A 0.025%-m concentration of p-phenylenediamine additive was optimal as NO_x levels were substantially reduced in the whole load range in comparison with neat biodiesel. However, hydrocarbon and CO emissions were found to have increased by the addition of antioxidants.