The European oil rerefining industry is comprised of 28 plants treating waste oil, which represent one‐third in volume of the total European market for lubricants. The biggest European rerefineries with capacity greater than 40 000 tons/year apply various technologies for recycling of used oils from different sources. Used oil recycling technology has undergone significant changes over the past decade. With the newly developed rerefining technologies it is possible to produce higher quality base oil compared with the traditional and old acid clay methods. Currently in Europe the following re‐refining methods are widely used: solvent extraction (N‐methyl‐2‐pyrrolidone (Germany), Interline process (United Kingdom, Spain)); combined vacuum distillation and solvent extraction (Vaxon process (Denmark, Spain); hydroprocessing (Hylube process (Germany)); combined thin film evaporation and hydrofinishing (CEP process (Finland)); combined thermal de‐asphalting and hydrofinishing (Revivoil process (Italy, Poland, and Spain)). The majority of applied technologies in Europe is appropriate for rerefining of synthetic lubricating oils, which currently are replacing the conventional mineral lube oils due to their enhanced performance characteristics. However, for the rerefining technologies applying alkaline treatment (CEP, Vaxon) and hydrofinishing step (Cyclon, Snamprogetti, Revivoil) the amount of synthetic or semi‐synthetic oils based on esters in the feedstock should be eliminated, since these oils are less stable under alkali and hydrofinishing conditions. © 2013 Society of Chemical Industry
In this paper, estimation of the chemical composition of used oils collected from several European locations was performed on the basis of a comparative analysis of chemical composition of commercially available fresh and used motor oils. Although the motor oil undergoes a range of chemical and physical transformations during routine engine operations, information about the structure of hydrocarbons in the fresh oil allows for an estimation of the approximate ratio of different types of hydrocarbons in the same oil after its use. As an example, a particular type of fresh oil was used in the engine and then reanalyzed by the same analytical techniques. Gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis (CHNS/O analysis) were used to characterize the chemical composition of the oil samples. A comparison of the obtained results showed correlations between chemical properties of the fresh oil and the collected used oil. Both oil FTIR spectra exhibited the bands that are related to the presence of carbonyl groups and amine-containing compounds, respectively. Opposite from the fresh oil, phenols were not found in the used oil. According to the obtained 1H NMR spectra, the paraffinic hydrocarbons of the fresh oil are more linear and have longer chains than those in the used oil.
BACKGROUND: Nowadays, different automotive sources generate globally large amounts of used oils. To achieve maximum energy conservation and environmental benefits, re-refining of used oil is preferable. Since removal of silicon and its chemical species is of great interest in the oil recycling industry, the aim of this study was to improve understanding of the behaviour of silicon-containing compounds at industrially relevant alkali treatment conditions. RESULTS: At industrially relevant alkali treatment conditions transformations of the model hydrogen-terminated tetramethyldisiloxane (TMDS)resulted in the formation of solid siloxanolate salts. The activation energy for TMDS transformation in the presence of 33 wt% aqueous KOH was found to be 37 kJ mol −1 , which is almost two-fold lower than that for NaOH. The experimental data demonstrated that the formation of solid products undesired from an industrial point of view can be diminished by an addition of either an alcoholic solvent or dimethyl carbonate. CONCLUSIONS:The experimental results obtained can be utilized for optimization of silicon-containing used oil recycling. In particular KOH as an alkali agent is more efficient than NaOH; addition of methanol dramatically increases the reaction rate, while dimethyl carbonate introduced into the reaction mixture enhances selectivity to the liquid products. Industry 7 145 ml Dodecane, 3.72 mmol TMDS, 12.5 mmol NaOH, 55.5 mmol H 2 O, 3.72 mmol DMC 8 145 ml Dodecane, 3.72 mmol TMDS, 12.5 mmol NaOH, 55.5 mmol H 2 O, 3.72 mmol DMC, 11 mmol CH 3 OH J Chem Technol Biotechnol 2015; 90: 34-43
The behavior of the simplest linear siloxane under base-catalyzed conditions was investigated in the temperature range of 60−110 °C for different concentrations of linear siloxane (0.05−0.5 wt %) in dodecane as the solvent with an aqueous solution of sodium hydroxide added as the alkali agent. Samples were taken regularly and analyzed by GC−MS. The activation energy for the studied conditions was found to be equal to 68 kJ/mol. The reaction rate decreased with increasing sodium hydroxide concentration as a result of the formation of dibasic siloxanolates, which are less reactive than single siloxanolates. The proposed reaction mechanism includes stages of polycondensation and siloxane cyclization. The composition of the final reaction mixture (i.e., the ratio between the solid and liquid products) was found to depend strongly on the reaction parameters. Analysis of the solid products by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of sodium siloxanolates. Thermogravimetric analysis (TGA) and temperature-programmed oxidation−mass spectrometry (TPO−MS) results demonstrated that the water content in the solid products decreased with increasing relative concentration of alkali agent in the reaction mixture.
BACKGROUND The behavior of silicon species in the recycling processes of waste lube oils is of great interest because of the negative effect of silicon compounds on the performance of hydrotreating catalysts and the formation of undesired solid deposits at various locations in the re‐refining units. To operate alkali treatment of silicon‐containing used oils efficiently in the recycling industry prediction of silicon species behavior is required. To this end kinetic modeling of the base catalyzed transformation of a model siloxane compound was done. RESULTS A kinetic model was developed for tetramethyldisiloxane (TMDS) transformation reactions under industrially relevant alkali treatment conditions in dodecane with sodium hydroxide as alkali agent. A reaction scheme describing the main pathways of TMDS transformation was proposed considering experimental and literature data. The studied model compound underwent hydrolysis, condensation and disproportionation reactions with formation of different molecular weight linear siloxanes. The latter were transformed to cyclic siloxanes through sodium silanolates generation. The data obtained experimentally were validated with the advanced kinetic model. CONCLUSIONS The proposed model fitted experimental data adequately, indicating that it can be used in the design and control of the caustic treatment of used oil containing silicon species. © 2015 Society of Chemical Industry
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