Obtaining high-added value products from the technical cashew-nut shell liquid using electrochemical oxidation with BDD anodes

Abstract

The electro-organic synthesis is currently experiencing a renaissance due to the tremendous contributions of various electrocatalytic materials as well as the use of electric current as an inexpensive and suitable reagent to drive the electrosynthetic transformations, avoiding conventional chemical oxidizers or reducing agents. Consequently, electrosynthesis has a significant technical impact due to its advantages such as versatility, environmental compatibility (possibility of recovering and recycling non-converted substrates), automation (switching on or off electric current), inherent safety and potential cost effectiveness among others. Although many novel electrode materials have been developed and established in electro-organic synthesis, diamond films (as boron doped diamond (BDD) electrodes) emerge as a novel and sustainable solution in selective electrochemical transformations for value-added organic products. For this reason, in this work, the use of BDD to treat technical cashew-nut shell liquid (t-CNSL) was proposed to favor its conversion on high-added value products such as carboxylic acids. The evolution of five carboxylic acids was followed over time for the experiments of the three different current densities using 0.1% of t-CNSL in 1.00 mol L−1 NaOH. At 40 mA cm−2, the most notorious increase in the organic acids concentrations took place during the two last hours achieving electrochemical conversions of about 144, 120, and 75 mg L−1 for the acetic, formic and oxalic acids, respectively. The results are discussed in light of the existing literature.