(688a) Conversion of Natural Gas to Value-Added Carbon Materials Via Microwave Plasma Technology

Advanced microwave plasma technology practically and cost-effectively converts natural gas to value-added chemicals and premium carbon materials such as graphene and conductive carbon black analogues (CCBA) with no CO₂ emissions and low capital and infrastructure expenditures. In this work a microwave driven plasma drives hydrocarbon decomposition – producing a variety of carbon nanostructures without the use of catalyst. Primary products include nanographene and graphitic carbon particles with structure analogous to conductive carbon blacks. Analytical techniques including high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy and electrical conductivity measurements are utilized to study the form and quality of these valued carbon materials. With lower-energy requirements than conventional thermal plasmas, reactions in microwave plasmas are driven by electron kinetics rather than thermodynamics, and their non-equilibrium energy distribution opens reaction pathways that are unavailable with conventional chemical or thermal plasma processes.

Whereas pyrolytic decomposition of hydrocarbons typically produces unstructured carbon, the nanoplatelets are characterized by dimensions of 200 – 500 nm, occurring in stack of 2-6 with morphology resembling mildly crumpled paper. Methane conversion can reach 90% with selectivity to products determined by the effluent stream’s temperature regime. Accompanying spectral diagnostics are used to characterize the reacting flow. The complement CCBA material has structure analogous to that of commercial high-value conductive carbon blacks, with high electrical conductivity higher than that of some commercially available conductive carbon blacks. These results highlight the importance of advanced plasma technology for the economic utilization of natural gas by producing premium carbon materials.

The co-production of hydrogen and high-value carbon materials from natural gas offers opportunities to reduce the costs associated with large-scale production of industrial or fuel hydrogen or platform chemicals while also producing synthetic, high-value carbon products such as the graphene nanoplatelets. H Quest Vanguard Inc. is developing microwave plasma processing of natural gas as a modular, compact and portable technology for production of hydrogen and premium carbon products.

Figure 1 Nanocarbons formed in the microwave plasma.