Role of silica on stability of mesoporous rice husk based catalyst and its activity in synthesis of biolubricant stock
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Role of silica on stability of mesoporous rice husk based catalyst and its activity in synthesis of biolubricant stock Hong Khanh Dieu Nguyen1 · Hung Van Vo1 · Ngo Thi Dinh1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This report aimed to publish a novel study on thermal and hydrothermal behaviors of ordered mesoporous carbon based catalysts derived from rice husk. Two types of the catalysts used in the study were the ones prepared with and without the silica content in the rice husk, assigned as MRCO and MRCS catalysts, respectively. The catalysts were prepared by condensation-evaporation method where water solvent was slowly and gradually evaporated from the reaction media leaving a gel-like mixture product at the end of the process. The hydrothermal and thermal stabilities of these catalysts were tested based of the stability of their ordered mesoporous structure under heating conditions. The results showed that the MRCO catalyst had lower hydrothermal stability (500 °C), but had higher thermal stability (the (110) peak could stand at 140 °C), compared to the MRCS catalyst (400 °C and the (110) peak could stand at 120 °C, respectively). The catalyst activity was tested in synthesis of biolubricant stock from castor oil at the temperature, time and stirring speed of 130 °C, 6 h and 400 rpm, respectively, and the biolubricant yield reached over 90% with the high purity of the product (no trace of –OH and epoxides). Some major characterizations were applied in this study including XRD and TG-DSC coupled with MS detector for determining the compounds in the gas products. Keywords Mesoporous materials · Rice husk · Thermal stability · Hydrothermal stability · Carbon based catalyst
1 Introduction Vegetable oil based lubricants, or also being called as biolubricants, were highly attractive substitute resources to petroleum based lubricants because of their environmentally friendly, renewable, non-toxic and biodegradable properties. Otherwise, the vegetable oil based lubricants were also of excellent lubricating characteristics, i.e. they had high viscosity index, good viscosity, very safe flash point, low volatility and easy to combine with many performanceimproved additives [1–3]. One of the most popular oil for producing biolubricant stock was castor oil because of its high viscosity, unsaturated carbon chains and good viscosity index [4–7]. The reason for these good properties was that the castor oil contained a large amount of ricinoleic acid esters (could be over 90% by weight) which possessed hydroxyl group in the middle position of the carbon chain * Hong Khanh Dieu Nguyen [email protected] 1
Hanoi University of Science and Technology, Hanoi, Vietnam
[5, 6]. Generally, conversion of castor oil to biolubricant stock required some steps: epoxidation of unsaturated C=C bonds; opening of the epoxy rings by nucleophile reagent; and esterification of the free hydroxyl groups [5, 7]. Therefore, in common, the first step of this process was to established the epo
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