Recyclable catalyst in the production of dehydrated castor oil

Researchers have evaluated KHSO4 as a recyclable catalyst in the production of dehydrated castor oil to be applied in alkyd resins – and found that it can be re-used with a low decrease in activity.

Castor bean fruits on the plant as a symbolic image.
Bio-based resins from castor oil employed as precursors in bio-based polyurethane coatings exhibit enhanced/excellent properties.  Image source: DEZALB - Pixabay (symbol image).

Drying castor oil was obtained using KHSO4 at 230 °C and 190 min. KHSO4 catalyst can be re-used in the dehydration of castor oil with a low decrease in activity, i.e., a conversion of 81% was achieved after the 5th re-use. This activity loss can be compensated with a small addition of fresh catalyst. This slow deactivation of the catalyst was due to a decrease in its acidity, because KHSO4 was partially and slowly transformed into K2SO4 and K2S2O7 during the reaction, releasing water, SO3, and SO2.

Good properties

An alkyd resin was obtained from dehydrated castor oil, with an acid index lower than 10 mg KOH/g. This resin exhibits properties, such as Gardner colour, nonvolatile compounds, and Garner viscosity, similar to a commercial resin. The film obtained from the dehydrated castor oil resin showed the same properties as those of a commercial resin.

The study has been published in Progress in Organic Coatings, Volume 161, December 2021.

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