J.W. Heim II, R.L. Vander Wal
The Pennsylvania State University,
United States
Keywords: thermo-catalytic decomposition, carbon nanostructure, decarbonization, natural gas, HRTEM
Summary:
TCD, an alternative energy technology produces (turquoise) hydrogen by decarbonizing fossil fuels such as natural gas or coal-derived volatiles or heavy hydrocarbons, providing a bridge to the hydrogen economy. A limitation is the deactivation of the carbon catalyst, more specifically the depositing carbon exhibits lessening activity with reaction duration. Complementing TCD is regeneration. Partial oxidation by CO2 creates new active sites, thereby renewing carbon catalyst activity. Partial gasification of deposited carbon by H2O (generating H2) establishes the baseline for coal gasification. Neither TCD nor carbon oxidation have been tested under an E-field for change in activation energy or mechanism. For both reactions, an imposed electric field offers potential to maintain and potentially increase the reaction rate; occurring either by an increase in active site number or shift in their energy level. (Correspondingly, the associated activation energy for elementary reaction step(s) would also change). Hypothesized is that an applied E-field changes the reaction mechanism, manifested by activation energy and kinetics of deposition and regeneration. Two E-field configurations, low voltage, high current and low current, high voltage are being tested. Active site quantification and kinetic rate measurements are performed across a temperature-time matrix. Analytical techniques include XPS for quantifying active site number via chemisorbed oxygen, resolved by functional group and Raman for comparative defects. Kinetic rates are based upon gravimetric measurement of deposited carbon in TCD, measurement of CO concentration in regeneration by CO2 or H2 concentration in regeneration with H2O. Activation energies are extracted and evaluated for steadiness or change. Active site and kinetic dependence upon reactive gases and their concentrations are mapped parametrically as function of applied E-field strength, polarity, direction and frequency. Therein changes in rates are resolved by active site number or activation energy under E-field action. Carbon catalyst metrics of activity and stability are assessed in TCD, and after regeneration to assess effectiveness.