Coke burning intrinsic kinetics

To couple the intrinsic coke burning kinetics described in Section II.B with gas and solid flow models, the simplest approach is provided by the one-dimensional solid dispersion model based on following assumptions ... 

Experimental Conditions. As the aim of the present study is to understand the intrinsic coke-burning behavior of FCC catalysts, extreme care has been taken in selecting experimental conditions so that no transport resistances influence the results. Minimizing the oxygen axial concentration gradient and obtaining sufficient kinetic data are the two... 

To understand and to model coke burn-off within a single particle the intrinsic kinetics (without any resistance by diffusion), mass transfer by pore diffusion and external diffusion, and structural parameters of the catalyst have to be taken into account. 

Intrinsic Kinetics of Coke Burn-Off The intrinsic kinetics of deactivation and regeneration of a reforming catalyst have been studied by Kern et al. (Kern, 2003 Kem and Jess, 2005 Ren et al., 2002). The main results are ... 

The calculated influence of pore diffusion on the coke bum-off (Fig. 4) is also reflected by the measured carbon distribution over the particle cross section for catalyst samples, which were regenerated at different temperatures up to a defined bum-off degree of about 55%. Fig. 5 shows that a pronounced gradient of the carbon load over the particle cross section for a bum-off temperature of 530°C is developed. For a temperature of430°C no gradient is determined. The rate of the oxygen conversion is then so slow, that the diffusion in the pores has no influence and the coke is uniformly burned within the particle according to the (intrinsic) rate of the chemical reaction. Both results are consistent with the kinetic measurements und calculations (see Fig. 4). 

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