(180d) Reaction Pathway Analysis for Electrolysis of Alcohols and Sugars in Sub-Critical Water

Electrolysis in sub-critical water could degrade harmful and thermally stable organic compounds into harmless ones such as hydrogen, carbon dioxide and water. In this research, we tried to investigate electrochemical reactions of alcohols and sugars in sub-critical water to evaluate possibility for selective production of hydrogen and added-value chemicals. Electrochemical reactions were carried out in sub-critical water using both a 500 mL batch autoclave and a flow-type reactor made of SS316. Once the reactor was heated up to a desired temperature, constant electrical current (for alcohols) or constant voltage (for sugars) was applied to carry out the electrolysis reaction for 30-120 min. For comparison, we conducted thermal degradation experiments of alcohols and sugars without any DC current loading at identical conditions. Here we employed glycerol, butanol, glucose and fructose as model compounds of alcohols or sugars. After the electrolysis reactions, the current was cut off and the system was cooled to terminate further reaction. Then, gaseous products obtained were analyzed by GC-TCD to quantify the amount of hydrogen, carbon dioxide and oxygen produced and liquid products were analyzed by HPLC and GC-FID. The amount of total organic carbon in every aqueous product solutions was determined by using a TOC analyzer. After the reactions, formic acid, glycolic acid, L- and D-lactic acids were mainly formed from the hydrothermal electrolysis of glycerol, especially lactic acids could be obtained as main products. In contrast, formic acid could be produced from the thermal degradation of glycerol at the same condition. In the case of electrolysis of sugars, liquid products obtained by this reaction at 30 V were similar to those obtained by thermal degradation in sub-critical water. However, product distributions including gaseous products were quite different between the two treatments. Detailed findings will be introduced at the conference.

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