GENERAL PROCEDURE: All catalytic activity testing experiments were carried out in Schlenk tubes (50 mL) equipped with a condenser. 8-Hydroxycaprylic acid (HCA) was prepared by HDO oxidation reaction in alkaline aqueous medium using H2O2 as oxidant. The typical reaction procedure was as follows: first, the aliphatic diol (0.5 mmol) was weighed and dispersed with catalyst (25 mg) in deionized water (3.5 mL) in a Schlenk tube. Subsequently, 30% H2O2 (0.75 mL) and 0.5 M NaOH (0.75 mL) were added to the above mixture. The Schlenk tubes were placed in an oil bath preheated to 353 K and reacted for different time intervals under continuous magnetic stirring (500 rpm). After completion of the reaction, a portion of the reaction solution was taken and diluted 20-fold with 10 mM aqueous H2SO4 and the catalyst was removed by passing it through a 0.20 μm filter (Milex-LG). The resulting filtrate was analyzed by high performance liquid chromatography (HPLC, WATERS 600) on an Aminex HPX-87H column (Bio-Rad Laboratories, Inc.) with a refractive index detector. An aqueous solution of 10 mM H2SO4 was used as the eluent at a flow rate of 0.5 mL/min, and the column temperature was maintained at 323 K. The conversion and yield were determined by the calibration curve method for commercial products.
