Solar Energy, Vol.113, 303-312, 2015
Towards efficient solar STEP synthesis of benzoic acid: Role of graphite electrode
Solar Thermal Electrochemical Process (STEP) synthesis of benzoic acid from toluene using a platinum anode has been developed as high yield and selectivity using the full spectrum of sunlight. STEP organic is an efficient process for organic synthesis based upon its use of a platinum electrode. This is a significant drawback as it is not cost effective. In this paper, the use of an active, inexpensive, graphite anode is introduced. The functionalized (aged) graphite anode was found to have a high reactivity for the oxidative conversion of toluene into benzoic acid. The yield of benzoic acid synthesized rises to 15.1% at 30 degrees C to 44.6% at 90 degrees C for the functionalized graphite anode, compared to only 12.4% and 32% respectively at a Pt anode. High conversion rate and chemical selectivity were achieved by balancing and controlling the rate of solar-to-thermal and solar-to-electric conversions. The factors influencing the efficiency and selectivity of the reaction are discussed, experimental results demonstrate the beneficial effect of increasing temperature on the yield for the process. The role of the functionalized graphite anode is considered and analyzed by SEM, FTIR and EDS. Graphite anode activity is enhanced by C-OH, C=O, and COOH generated on the graphite surface. (C) 2015 Elsevier Ltd. All rights reserved.