Filamentous carbon formation

R.T.K. Baker, D.J.C. Yates, and J.A. Dumesic, Filamentous Carbon Formation over Iron Surfaces, in Coke Formation on Metal Surfaces, in Coke Formation on Metal Surfaces, eds. L.G. Albright and R.T.K. Baker, American Chemical Society, Washington D.C., 1982, p. 1. D.J. Dwyer, Iron Fischer-Tropsch Catalysts Surface Synthesis at High Pressure, Prep. ACS Div. Pet. Chem. 29 (1984) 715. 

Filamentous Carbon Formation over Iron Surfaces... 

The remainier of the specimens were pretreated In 5 Torr O2 at 600°C for 1 hour, conditions where the metal Is expected to form Fe20j. When these specimens were exposed to 2 Torr acetylene, filamentous carbon formation was not detected until 700°C. Even at this temperature, reaction was restricted to only... 

Atomic carbon, encapsulating and filamentous carbon are the most important types of carbon formed. It is generally accepted that filament carbon formation (13) involves the formation of adsorbed surface carbon, dissolution and segregation of surface carbon, diffusion of carbon through Ni particles and precipitation of filaments. The mechanism of carbon formation (12,13) is illustrated in Fig. 1. CNi,f is the concentration of carbon dissolved in nickel at the front of the particle, just below the selvedge, and CNi.r is the concentration of carbon dissolved in nickel at the rear of the particle (support side). The properties of the carbon on the front side and the filamentous carbon on the rear side are rather different. The different... 

Li et reported a novel method of obtaining nickel oxide particles with controlled crystalline size and fibrous shape, highly dispersed on in situ produced carbon, inhibiting further growth of Ni particles. On the other hand, Ni/CFC (filamentous carbon) catalysts were shown to have sufficient efficiency in low-temperature methane decomposition. Thus, the use of CFG, whose textural properties can be modified by their activation with Hg or COg, opens up the possibility of its application as a support in heterogeneous catalysis. Methane decomposition over Ni-loaded activated carbon (AC) was also investigated. XRD results showed absence of NiO with only Ni metal crystallites formed in the catalyst even if calcined in Ar, which eliminates the inevitable reduction step with other supports. However, the formation of NisC during the process leads to deactivation of the catalysts. Filamentous carbon formation is... 

Baker RTK, Alonzo JR, Dumesic JA, Yates DJC. Effect of the surface-state of iron on filamentous carbon formation. J Catal 1982 77 74-84. 

As is visible in Figure 4.14, a usage of 20 h is enough to produce an evident porosity of the dense layer also, an effect of superficial corrosion, due to the filamentous carbon, can be seen from the scanning electron microscopy (SEM) analysis (Galuszka et al., 1998). All the experimental evidence showed that these kinds of membranes are useful for the separation of methane and carbon monoxide-free streams, because while the swelling, due to hydrogen, can be controlled in a certain way, the same cannot be said for filamentous carbon formation. 

Snoeck, J., Froment, G. and Fowles, M. (1997). Filamentous carbon formation and gasification Thermodynamics, driving force, nucleation, and steady-state growth, J. CataL, 169, pp. 240-249. 

---