Aqueous-phase biphasic dehydroaromatization of bio-derived limonene into p-cymene by soluble Pd nanocluster catalysts

A biphasic approach to the dehydroaromatization of bioderived limonene into water-insoluble p-cymene using soluble Pd nanoparticle catalysts in an aqueous phase (⩾150 °C, 2 bar H2) was successfully achieved with a conversion of 93% and a selectivity of 82%. The Pd nanoparticles, operating under forcing conditions (180 °C, 2 bar H2), can be recycled at least four times without noticeable degradation. The effects of temperature, pressure, reaction time, pH, catalyst concentration, metal type, the type and amount of polymer stabilizer, and the preparation method were systematically investigated to optimize the process and provide insight into the mechanisms involved.