Metal-Catalyzed Thermo-Catalytic Decomposition and Continuous Catalyst Generation

Metal dusting affords a way to generate metal catalysts in situ from cheap metal sources and a high density of catalyst particles is created, anchored to a metal support. The metal dusting-catalyzed carbon magnifies the second-stage TCD rate and yield by virtue of its greater active surface area. Complementary microscopic, spectroscopic, and thermo-gravimetric characterizations highlight the structural differences between the first (TCD)-stage metal-catalyzed carbon and the second (TCD)-stage carbon-catalyzed carbon. Using model carbons, the TCD carbon’s nanostructure did not appear to depend on the nanostructure of the nascent carbon catalyst. Highlights: In this study, metal dusting is utilized to initiate a two-stage thermo-catalytic decomposition (TCD) process. Stage 1 starts with metal-catalyzed TCD, and in stage 2 the metal-catalyzed carbon catalyzes additional TCD. TEM is presented of the early- versus late-stage TCD to qualitatively illustrate the second-stage TCD by the metal-catalyzed carbons. Corresponding SEM illustrates differences in growth type and surface density between early versus late reaction times, with backscattered imaging differentiating the first- versus second-stage TCD. TGA supports the microscopic inference of a second carbon phase by the presence of an early (low-temperature) reaction peak, characteristic of low-structure or disordered carbon as the second-stage TCD carbon. Raman analysis confirms that the second-stage carbon deposit is more disordered and unstructured, especially at 1000 °C, supported by the I_D/I_G and La value changes from 0.068 to 0.936 and 65 nm to 4.7 nm, respectively. To further confirm second-stage TCD occurrence upon pre-catalyzed carbons, two carbon blacks are tested. Exposing a combination of edge and basal or exclusively basal sites for the graphitized form, they afford a direct comparison of TCD carbon nanostructure dependence upon the initial carbon catalyst nanostructure. Pre-oxidation of the stainless-steel wool (SSW) prior to TCD is advantageous, accelerating TCD rates and increasing carbon yield relative to the nascent SSW for an equivalent reaction duration.