Stainless steel ball milling for hydrogen generation and its application for reduction

Abstract

Hydrogen (H2) is an environmentally friendly energy source that produces only water through combustion and is a useful reducing agent in organic chemistry. However, according to the law, it needs to be strictly stored, transported, and managed in pressure vessels. Although H2 is mainly produced industrially by the steam reforming of methane (CH4), this is not environmentally friendly owing to the emissions of carbon dioxide (CO2) as well as the energy input from the endothermic reaction. Herein, hydrogen generation is achieved from water (H2O and D2O), alkane, and diethyl ether (Et2O) without CO2 emissions through the mechanochemical collision of stainless-steel balls using a planetary ball mill machine. Furthermore, in situ generated H2 can be directly utilized as a reductant for various reducible functionalities, such as alkynes, alkenes, ketones, nitro groups, and aromatic halides. In addition, D2 derived from D2O promotes a reductive deuteration to provide the corresponding deuterated products. When using Et2O as a hydrogen source, a reduction of arene can be achieved. In this paper, the hydrogen generation from water, alkanes, and Et2O, subsequent hydrogenation, and the role of stainless-steel balls are summarized.