EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Methane pyrolysis is a process that produces hydrogen and solid carbon through the thermal decomposition of methane or natural gas (CH4 => 2 H2 + C). This process has the potential of enabling a sustainable hydrogen production with low to zero CO2 emission. In 2016, roughly 60 million tons of hydrogen were produced worldwide. If current production processes like steam methane reforming were to be replaced by methane pyrolysis, 180 million tons of carbon would be produced as a complementary product. This carbon material must be utilized to achieve an efficient use of resources and to allow methane pyrolysis to be economically competitive to steam methane reforming. Within this work, carbons obtained from three different methane pyrolysis process routes were investigated, i.e. fixed bed-, plasma-, and metal bath processes. The structure of the carbons derived was investigated using advanced characterization techniques. X-ray diffraction and Raman spectroscopy showed either graphite-like carbon (fixed bed process) or turbostratic carbon (plasma-, metal bath processes). Carbon purities of up to 99 wt% were detected based on thermogravimetric analysis in oxidizing atmosphere (synthetic air). Scanning electron microscopy revealed that carbons from different process routes displayed different morphologies, ranging from flake-like and spherical particles to irregularly shaped particles with a bimodal particle size distribution. Carbons derived from the plasma process displayed a reasonably large specific surface area (~200 m²/g), as deduced by gas sorption measurements (N2 at 77 K), along with a sufficient carbon content (~70 wt% based on thermogravimetric analysis). These carbons may have the potential to replace biochars by serving as supplements in agriculture, thus enabling a large-scale industrial hydrogen production using a sustainable methane pyrolysis process.