Rape oil transesterification by methanol and ethanol on extruded hydrotalcite catalyst

• Published in: Reaction kinetics, mechanisms and catalysis mechanisms and catalysis, 2021-02, Vol.132 (1), p.203-218
• Main Authors: Kašpárek, Aleš, Kocík, Jaroslav, Tokarová, Věnceslava
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Physical Chemistry
• ISSN: 1878-5190; 1878-5204
• DOI: 10.1007/s11144-020-01915-4

This article is devoted to rape oil transesterification by methanol and ethanol on powder and extruded Mg/Al hydrotalcite catalyst in a stirred reactor under atmospheric pressure close to boiling point of alcohol with inserted perforated basket with extrudates. With 15 wt% of catalyst in relation to rape oil and molar ratio methanol/ester group of oil 13:1, the yield of monomethylester reached 99.5% within 48 h in the case of fresh catalyst. After recalcination, the same catalyst enabled the same yield of monomethylester within 72 h and third cycle of this catalyst after two recalcinations led to 98.5% of monomethylester yield also within 72 h. Extrudates enabled the same monoester yield as hydrotalcite powder within 24 (60–61%) up to 48 h (99%). Moreover, several experiments were done in the autoclave to assume temperature effect to reaction time. Enhanced temperature 140 °C provided nearly 99% monoester yield within 12 h. A new arrangement with extrudates in a perforated basket makes transesterification with heterogeneous hydrotalcite catalyst easily feasible. Differently from rather promising results in rape oil transesterification with methanol, ethanol worked in this reaction much more slowly. Not surprisingly water inhibits transesterification, as the reaction with 96% ethanol shows. Using 99.8% ethanol nearly without water makes transesterification significantly faster, but 51% monoester yield after 120 h reaction time is still insufficient. Nevertheless, ethanol remains a promising raw material for oil transesterification, as it can be prepared by a bioprocess, which makes the whole technology based on renewable sources.