Biodiesel oxidation

Lacoste, F., and Lagardere, L. 2003. Quality Parameters Evolution During Biodiesel Oxidation Using Rancimat Test. Eur. J. Lipid Sci. Technol., 105,145-155. 

Falk, O. R. Meyer-Pittroff. The effect of fatty acid composition on biodiesel oxidative stability. Eur. J. Lipid Sci. TechnoL 2004, 106, 837-843. 

Lacoste, E L. Lagardere. quality parameters evolution during biodiesel oxidation using rancimat test. Eur. J. LipidSci. Technol. 2003,105, 149-155. 

Monyem, A. J.H. Van Gerpen. The effect of biodiesel oxidation on engine performance and emissions. Biomass Bioenergy 2QQ1, 20, 317-325. 

J. A. Waynick, Characterisation of biodiesel oxidation and oxidation products. The Coordinated Research Council, Southwest Research Institute Project N° 08-10721, San Antonio, Texas (2005)... 

Knothe, G., 2007. Some aspects of biodiesel oxidative stabiUty. Fuel Proc. Technol. 88,669-677. 

Wazilewski, W.T., Bariccatti, R.A., Martins, G.I., Secco, D., Melegari de Souza, S.N., Rosa, H.A., Chaves, L.I., 2013. Study of the methyl crambe (Crambe abyssinica Hochst) and soybean biodiesel oxidative stability. Ind. Crops Prod. 43, 207-212. 

Biodiesel does not present any special safety concerns. Pure biodiesel or biodiesel and petroleum diesel blends have a higher flash point than conventional diesel, making them safer to store and handle. Problems can occur with biodiesels in cold weather due to their high viscosity. Biodiesel has a higher degree of unsaturation in the fuel, which can make it vulnerable to oxidation during storage. 

This prompted us to investigate the possibility of selectively hydrogenate highly unsaturated oils, unsuitable for the production of Biodiesel, in order to improve their oxidative stability while keeping the cold properties. 

Hydrotreating has been proposed by Arbokem Inc. in Canada as a means of converting Grade Tall Oil into biofuels and fuel additives. However, this process is a hydrogenation process which produces hydrocarbons rather than biodiesel. Recently a process for making biodiesel from crude tall oil has been proposed. It relies on the use of an acid catalysts or of an acyl halide for the esterification reaction, but no information is given on the properties of this fuel, particularly concerning the oxidative stability. 

Biodiesel is a mixture of methyl esters of fatty acids and is produced from vegetable oils by transesterification with methanol (Fig. 10.1). For every three moles of methyl esters one mole of glycerol is produced as a by-product, which is roughly 10 wt.% of the total product. Transesterification is usually catalyzed with base catalysts but there are also processes with acid catalysts. The base catalysts are the hydroxides and alkoxides of alkaline and alkaline earth metals. The acid catalysts are hydrochloride, sulfuric or sulfonic acid. Some metal-based catalysts can also be exploited, such as titanium alcoholates or oxides of tin, magnesium and zinc. All these catalyst acts as homogeneous catalysts and need to be removed from the product [16, 17]. The advantages of biodiesel as fuel are transportability, heat content (80% of diesel fuel), ready availability and renewability. The... 

Oxidation to CO of biodiesel results in the formation of hydroperoxides. The formation of a hydroperoxide follows a well-known peroxidation chain mechanism. Oxidative lipid modifications occur through lipid peroxidation mechanisms in which free radicals and reactive oxygen species abstract a methylene hydrogen atom from polyunsaturated fatty acids, producing a carbon-centered lipid radical. Spontaneous rearrangement of the 1,4-pentadiene yields a conjugated diene, which reacts with molecular oxygen to form a lipid peroxyl radical. 

The main unit is the catalytic primaiy process reactor for gross production, based on the ATR of biodiesel. After the primary step, secondary units for both the CO clean-up process and the simultaneous increase of the concentration are employed the content from the reformated gas can be increased through the water-gas shift (WGS) reaction by converting the CO with steam to CO and H. The high thermal shift (HTS) reactor is operating at 575-625 K followed by a low thermal shift (LTS) reactor operating at 475-535 K (Ruettinger et al., 2003). A preferential oxidation (PROX) step is required to completely remove the CO by oxidation to COj on a noble metal catalyst. The PROX reaction is assumed to take place in an isothermal bed reactor at 425 K after the last shift step (Rosso et al., 2004). 

The benefits of using biodiesel as renewable fuel and the difficulties associated with its manufacturing are outlined. The synthesis via fatty acid esterification using solid acid catalysts is investigated. The major challenge is finding a suitable catalyst that is active, selective, water-tolerant and stable under the process conditions. The most promising candidates are sulfated metal oxides that can be used to develop a sustainable esterification process based on continuous catalytic reactive distillation. 

Very poor biodiesel and biodiesel blends do not shed water as effectively as conventional diesel fuel fuel haze, gelling, and low-temperature handling problems can develop if biodiesel is contaminated with water in storage and transport. Poor double bonds present in the methyl ester compounds are active sites for oxidation and condensation reactions peroxide values can increase fuel darkening and deposit formation in storage systems can occur the addition of oxidation inhibitors to biodiesel helps improve storage stability. 

On the other hand, the storage stability of biodiesel is adversely affected by the presence of unsaturated alkyl components. The olefinic moieties in biodiesel fuel can undergo oxidative degradation via exposure to air with deleterious results, including formation of solids and gums. The degree of oxidative degradation has been shown to increase with fuel unsaturation. 

Alkaline earth metal oxides and hydroxides have also been tested in transesterification reactions. Ca(OH)2 did not show significant catalytic activity in the transesterification of rapeseed oil with methanol at conditions normally used to prepare biodiesel.Peterson et al. reported relative alcoholysis activities of a series of supported CaO catalysts under near reflux conditions of methanol-rapeseed oil mixtures at 6 1 molar ratios.Among the catalysts tested, the most active was CaO (9.2 wt% CaO) on MgO. For instance, in a 12 h reaction the total oil conversion using this catalyst was over 95%, similar to... 

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