Green Synthesis of Methyl Formate via Electrolysis of Pure Methanol
Ryoji Kishi, Hitoshi Ogihara, Miru Yoshida-Hirahara, Kazuya Shibanuma, Ichiro Yamanaka, H. Kurokawa
Abstract
Methyl formate (MF) is an important intermediate in the production of essential chemicals such as formic acid in the chemical industry. Although MF is currently synthesized via liquid-phase carbonylation of methanol, this carbonylation process has certain problems (e.g., catalyst deactivation). In this regard, alternative processes for MF production have been extensively examined, and MF formation with a high selectivity and high production rate at mild reaction conditions remains a critical goal in research. Here, we demonstrated MF synthesis via direct electrolysis of methanol at room temperature and atmospheric pressure. A membrane electrode assembly (MEA) consisting of Pt/C electrocatalysts and proton-exchange membranes (PEMs) played an important role in this process. In the electrolysis of the methanol/water solution, CO2 formation was suppressed as the water content decreased. Consequently, we found that the electrolysis of pure methanol produced MF without the formation of CO2. MF was produced through the electrolysis of pure methanol for 24 h with an average formation rate of 930 mmolMF h–1 gcat–1 and a turnover frequency of 468 h–1. The formation rate of MF via pure-methanol electrolysis using the MEA was comparable to previously reported systems. After the electrosynthesis of MF, the MEA could be reused. On the basis of cyclic voltammetry, transmission electron microscopy, and scanning electron microscopy measurements and electrolysis results, a reaction pathway for the oxidation of pure methanol to MF was proposed.