Abstract
Methane is the primary industrial H2 source, with the vast majority produced by steam reforming of methane—a highly CO2- and water-intensive process. Alternatives to steam reforming, such as microwave-driven plasma-mediated methane decomposition, offer benefits of no water consumption and zero CO2 process emissions while also producing solid carbon formed by pyrolytic reactions and aided by a plasma reactive environment. The economic viability of pyrolytic methane decomposition as a hydrogen source will depend upon the commercial applications of the solid carbon product—which, in turn, will depend upon its physical and chemical characteristics. This study focuses on material characterization of the solid carbon (secondary) product. Characterization by high-resolution transmission electron microscopy reveals forms ranging from graphitic to amorphous. Thermogravimetric analyses reveal three forms by their differing oxidative reactivity, while X-ray diffraction analyses support the different crystalline forms as suggested by Thermogravimetric analysis. Plasma perturbation of the radical pool, elevating radical temperatures and boosting concentrations, is proposed as altering the reaction paths towards solid carbon formation, resulting in the different sp2 forms.
Highlights
This study focuses on the carbon produced by plasma-mediated methane decomposition
Steam reforming of methane (SMR), the present industrial practice produces 13.7 kg CO2/kg of net hydrogen [3], and consumes 19.8 L
Muradov et al proposed that the lower degree of structural order in the plasma-generated carbon accounted for its higher catalytic activity in thermal decomposition of methane (TDM)—which they ascribed to a high concentration of reactive edge atoms [33]
Summary
This study focuses on the carbon produced by plasma-mediated methane decomposition. As background, while hydrogen is envisioned as the energy carrier (fuel) of the future, at present-day, it is a crucial feedstock for various manufacturing industries and petroleum refining. Steam reforming of methane (SMR), the present industrial practice produces 13.7 kg CO2 (equiv)/kg of net hydrogen [3], and consumes 19.8 L of water per kg of hydrogen [4] Recognizing both present day H2 consumption and costs of present production processes, attention has focused on more sustainable methods, such as thermal decomposition [5]. Muradov et al reported on the thermal decomposition of natural gas and methane using plasma-generated carbon aerosols [19]. In non-thermal plasmas, the plasma characteristics, such as electron concentration and energy distribution, are far more important as these drive radical formation and ensuing reactions [24] The former process is akin to soot formation in flames, wherein combustion reactions drive the pyrolysis reactions, with additional contributions from oxidative reactions and intermediates. This is the motivation for the this carbon characterization study the carbon produced by MW pyrolysis of methane, reported here
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
