Adding Value to Waste Minerals in a Circular Economy Framework: Ochre-Derived Layered Double Hydroxide Catalysts in Fatty Acid Ketonisation

Abstract

Transforming waste materials into added-value products is critical for a sustainable and circular economy. Here, Mg/Fe layered double hydroxide (LDH) materials, with a Mg2+:Fe3+ ratio of 2, were successfully synthesized via the co-precipitation method from a dissolved acid mine drainage precipitate waste “ochre”, which is normally put to landfill. The prepared LDH materials were tested as a heterogeneous base catalyst to promote the production of the ketone, 12-tricosanone, from lauric acid, a component of plant oils, through a ketonic decarboxylation reaction, giving a circular economy route to catalysts for sustainable ketone production. The highest yield of the ketone observed was 80%.

Heterogeneous ketonic decarboxylation of dodecanoic acid: studying reaction parameters

“…The studies from Corma, et al14 and Mekhemer et al 30 provided data regarding the effectivity of MgO powder to promote ketonic decarboxylation of carboxylic acids. Our recent studies 15,32 with a different type of material, the layered double hydroxides, also provided good ketone yields, with the catalytic activity being probably promoted by mixed basicity sites on the brucite-like layers. 15,36,37 As mentioned in Section 4.4 and as observed in Fig.…”

“…3(a). Dehydroxylation (loss of the Mg(OH) 2 species) is observed around 270 C, 31,32 followed by decarbonylation, 32,33 causing a mass loss of up to 9%. Fig.…”