Electrochemical reforming of glycerol into hydrogen in a batch-stirred electrochemical tank reactor equipped with stainless steel electrodes: Parametric optimization, total operating cost, and life cycle assessment

Abstract

The electrochemical reforming of glycerol was carried out in a batch-stirred electrochemical tank reactor equipped with stainless steel electrodes. A response surface methodology constituted by a Face-Centered Central Composite Design was performed to establish the optimal operational conditions to produce hydrogen. Studied parameters were glycerol concentration (CG), current intensity (I) and temperature (T), while chosen responses were hydrogen and oxygen concentrations (CH2 and CO2 ). A maximum CH2 (79.18 mg/L) and minimum CO2 (46.24 mg/L) with a global desirability of 67%, were achieved at multi-optimal conditions, including CG, = 3.46 mol/L, I = 5.21 A, and T = 70 ◦C. All studied parameters were significant for both chosen responses (ηCH2 and ηCO2 ) since all values of the sensitivity index were higher than 0.5. The analysis of interaction between parameters suggests than CG and T simultaneous increase will bring a decrease in CH2. The experimental data were fitted to a quadratic polynomial surrogate model, with correlation coefficients of 0.9801 and 0.9967 for ηCH2 and ηCO2 , respectively. The reduced root-mean-square error was 0.065 and 0.054 for ηCH2 and ηCO2 , respectively. This suggests a successful optimization of the BSETR operational parameters. The hydrogen production process assessed in this work, is a promising green energy technology that uses waste glycerol as a carbon-based fuel and a low-cost anode material (7.5 USD¢/kg H2) as stainless steel. The carbon footprint of the hydrogen production by the optimized process is 0.192 kg CO2 eq and this can be reduced 92.1% when using a solar photovoltaic system to energize the electrodes.