Transformation of tetramethyldisiloxane in used oil alkali treatment conditions: mechanism and kinetic modeling

Abstract

AbstractBACKGROUNDThe 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.RESULTSA 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.CONCLUSIONSThe 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