Oil-in-oil (0/0) emulsions are novel and very rare. In this study, the acetone-in-polydimethylsiloxane emulsion (Ac/PDMS emulsion) was used to microencapsulate the oxalic acid (OA) with acrylonitrile-butadiene-styrene (ABS) via solvent evaporation to delay the NH4Cl-NaNO2 exothermic reaction for the oil extraction. When respectively catalysed by the raw OA (0.6%, w/v) and the microcapsules loading the same amount of OA, the time to reach the temperature peak of the exothermic reaction (NH4Cl and NaNO2 in 2 mol/L) could be beneficially prolonged from 3 min to 34 min. Meanwhile, the OA loading, particle size, morphology, release and catalytic performances of the OA/ABS microcapsules were affected by the Ac/PDMS volume ratio and core/shell mass ratio. The Ac/PDMS emulsion solvent evaporation achieved the embedment of OA into ABS in the absence of an aqueous liquid, and the obtained tiny microcapsules could beneficially delay the NH4CI-NaNO2 exothermic reaction for the oil extraction. (C) 2017 Elsevier B.V. All rights reserved.