Microplasma production of methyl radicals for catalytic conversion of methane*

A combination of microreactor technology and dielectric barrier discharge (DBD) plasmas enable investigation of alternate chemical pathways for generation of plasma activated liquids [1]. This work focuses on an efficient method for generating methyl radicals from methane using low temperature microplasmas for in-liquid synthesis of methylated organometallic complexes.  This technique addresses the need for conversion of methane to higher value products.  The microreactor consists of a 500 μm channel etched on a Si substrate and covered with borosilicate glass as the dielectric. Nanosecond high voltage pulses of 10 kV operating at frequencies of 1-10 kHz were used to generate atmospheric pressure plasmas in an Ar/CH₄ feed gas. nonPDPSIM, a 2D plasma hydrodynamics model, was used to simulate the generation of methyl radicals and their transport to a bounding liquid containing organometallic catalysts.  nonPDPSIM solves Poisson’s equation and transport equations for charged and neutral particles in the plasma. The spatial and temporal evolution of CH₃ radicals, and their interaction with organic solvents are discussed for geometries having different plasma-liquid interfaces, including flowing films and droplets.

[1] Y. Liu et al., Journal Phys. D: Appl. Phys. 54, 194003 (2021).