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The lubricating efficiency is an important property of diesel fuel since several diesel engine parts, such as pumps and injectors, are lubricated by the fuel itself only. The evolution of oxidation products during oxidative deterioration may as well affect the lubricating properties of the biodiesel fuel blends and thus the proper functioning of a diesel engine. In this study Fatty Acid Methyl Esters were produced from various types of feedstock that significantly differentiate in their fatty acid profile. Each methyl ester was blended with an Ultra Low Sulphur Automotive Diesel (ULSD) at a concentration of 7% v/v which is currently the maximum acceptable FAME content according to the European Standard EN590. The B7 biodiesel blends were evaluated regarding fundamental physicochemical properties as well as their lubricating efficiency. Oxidation stability was examined on a Rancimat apparatus according to EN 15751 standard.

The introduction to the European market of higher levels of biodiesel blends focuses the research interest on the compatibility problems of the diesel fuel distribution system. The influence of metals in the oxidation stability and lubricity of two different types of commercially available FAMEs (without antioxidant additive) was investigated. Zinc (Zn), Copper (Cu) and Tin (Sn), were added in the form of solid metals (heterogeneous catalysis in liquid phase oxidation) and examined for their impact on the oxidation stability of biodiesel fuel. Oxidation stability was determined by Rancimat accelerated oxidation method, according to European Standard EN14214. Additionally, in order to examine the effect of the above mentioned metals in the presence of antioxidant additive, BHT was added in both biodiesel samples and oxidation stability determinations were carried out, as well.

FAME is the most common renewable component of conventional automotive diesel. Despite the advantages, biodiesel is more susceptible to oxidative deterioration and due to its chemical composition as well as its higher affinity to water, is considered to be a favorable substrate for microorganisms. On the other hand, apart from biodiesel, alcohols are considered to be promising substitutes to conventional diesel fuel because they can offer higher oxygen concentration leading to better combustion characteristics and lower exhaust emissions. More specifically, n-butanol is a renewable alcohol demonstrating better blending capabilities and properties when it is added to diesel fuel, as its composition is closer to conventional fuel, when compared ethanol to for example. Taking into consideration the alleged disinfectant properties of alcohols, it would be interesting to examine also the microbial stability of blends containing n-butanol in various concentrations.

The ability of a catalyst to enhance the performance of synthesized biobased lubricant basestock was investigated in this study. Pomace olive oil, cottonseed oil, used frying oil and methyl oleate were utilized as starting materials for the production of the biobased lubricants and a two stages transesterification methodology was followed. Initially the oils were converted to their corresponding fatty acid methyl esters via methanolysis. The resulting methylesters were subsequently transesterified with TMP producing the desired oleochemical ester. These syntheses were carried out in the presence of either sodium methoxide or Ca/TEA alkoxide as catalysts. Following the purification phase, the synthesized esters were evaluated as potential biolubricants regarding their physicochemical properties such as viscosity index, pour point and acid value.

This study investigates the effectiveness of seven phenolic compounds, including pyrogallol (PY), butylated hydroxytoluene (BHT), 2,5-di-tert-butylhydroquinone (DTBHQ), 4-tert-Butylcatechol (TBC), 2,5-bis(dimethylaminomethyl) hydroquinone, 2,5-bis(piperidinomethyl) hydroquinone and 2,5-bis(morpholinomethyl) hydroquinone on the oxidation stability of sunflower and soybean oil methyl esters. The seven phenolic compounds were dissolved in the base fuels at the same concentration levels, i.e., 200, 600, 800, 1000 and 1200 ppm. The oxidation stability measurements were carried out by employing a Rancimat accelerated oxidation unit according to EN 14214. Additionally, the antioxidant activity of the above mentioned compounds was also determined in a RSSOT apparatus (Rapid Small Scale Oxidation Test) according to ASTM D7545.

Additives that enhance properties, such as cetane number or cold flow, are introduced in diesel-biodiesel blends in order to upgrade its performance as well as to aid its handling and distribution. Furthermore, in order to protect the engine and fuel operating system equipment, diesel fuel may be treated with corrosion inhibitors and detergents. However, additives could also have an impact on other parameters beyond those that they are intended to boost. In the present study the effect of diesel fuel improvers on fuel’s microbial stability is examined. An additive-free ultra low sulfur diesel (ULSD) was blended with Soybean Fatty Acid Methyl Esters (FAME) and the resulting blend was treated separately with a series of commercially available diesel fuel additives.

One of the concerns for biolubricants is the improvement of their oxidation resistance. In this paper the oxidative behavior of seven different types of biobased lubricants basestocks is examined. The aim was to study their relative oxidation stability and also to investigate their response to various antioxidants. The renewable lubricants were treated with four antioxidant additives at a concentration of 0.5% wt. and a comparative assessments of the latters' effectiveness in suppressing the oxidation rate was carried out. Alterations in the acid value were examined as well as relative changes of the oxidized samples by FTIR spectroscopy. The oxidation stability was assessed by employing a Rapid Small Scale Oxidation Test (RSSOT) apparatus according to the accelerated oxidation stability standard method ASTM D7545/EN16091. RSSOT is a relatively new method and thus the behaviour of biobased lubricants and antioxidant agents in this accelerated method has not been thoroughly examined.

For many years Rancimat was the only standardized method for measuring the oxidation stability of FAME and FAME/diesel blends. However this method is not applicable to pure conventional petroleum products and so the effect of FAME on diesel fuel stability could not be evaluated directly. Recently a Rapid Small Scale Oxidation Test (RSSOT) that covers the determination of the stability of biofuels and petroleum products was developed and standardized. In this study the oxidation stability of seven different types of FAMEs was assessed, either neat or blended with three types of ULSD fuel, by employing both the Rancimat and the RSSOT accelerated oxidation methods. The determinations from either test were analyzed and a comparative assessment of these two method was carried out.