Hydrogen production from methane via liquid phase microwave plasma: A deoxidation strategy

• Effect of dissolved oxygen (DO) on CH 4 reforming was studied by liquid discharge. • Reducing DO can improve the discharge stability. • DO can affect the relative intensity of radicals generated in the discharge. • Reducing DO can increase the hydrogen yield and hydrogen production efficiency. In this paper, in order to improve hydrogen production, the effect of dissolved oxygen (DO) on methane (CH 4 ) reforming was studied by liquid phase microwave discharge firstly. DO was reduced by deducing pressure and gas replacement, and the reaction mechanism was researched by radical detection. It was revealed that reducing DO can improve hydrogen (H 2 ) yield and H 2 selectivity and energy efficiency of hydrogen production. When microwave power was 900 W and the DO was decreased from 4.82 mg/L to 0.65 mg/L, the production and selectivity of H 2 increased by 21.3 % and 22.6 % respectively, and the energy efficiency of hydrogen production increased by 33.1 %. Through the study on the characteristics of discharge radicals, it was concluded that ∙H extraction and ∙H coupling reaction and ∙OH oxidation ∙CH X are the main ways to produce hydrogen. The existence of DO affects the formation of H 2 by limiting the decomposition of water molecules. In addition, the reduction of DO can improve the stability of discharge. These results indicate that reducing the DO can be a simple, effective and energy conservation method to increase the selectivity of target products in the liquid phase discharge reforming of CH 4 .