Isobutane Cracking over Y-Zeolites

Reaction pathway analysis in thermal cracking of waste cooking oil to hydrocarbons based on monomolecular lumped kinetics

“…While, the experimental measurements of these entropy changes for thermal cracking of WCO are not readily available, a reasonable strategy can be adapted for determining such estimates. A reacting molecule contains translational, vibrational and rotational entropies [54]. The contributions of vibrational and rotational entropy of a molecule during activation are low as compared to the contribution of translational entropy [54,69].…”

“…A reacting molecule contains translational, vibrational and rotational entropies [54]. The contributions of vibrational and rotational entropy of a molecule during activation are low as compared to the contribution of translational entropy [54,69]. Thus, it was assumed that the vibrational and rotational entropies of a molecule are negligible as compared to the translational entropy.…”

“…The number of parameters (A j,i and E j,i ) to be estimated through regression was reduced by calculating the preexponential factors through transition state theory and statistical thermodynamics concepts [54]. This avoids the correlation between preexponential factors and activation energy of the reactions in parameter optimization.…”

Single-event microkinetics for coke formation during the catalytic cracking of (cyclo)alkane/1-octene mixtures

“…T m is the average temperature over the experiments andà the single-event preexponential factor. In order to reduce the number of kinetic parameters to be handled simultaneously, preexponential factors, were not estimated but calculated a priori via transition state theory and statistical thermodynamics [24][25][26]. A preexponential factor equal to 1.9  10 7 (kPa s) À1 was obtained for the alkylations considered as rate-determining steps for coke, by assuming that the transition state species has lost two translational degrees of freedom compared to the reactant state.…”

“…Rather than a pure deactivating effect by coking, in practice an interaction occurs between the cracking and the coking reactions [8]. Recently, during the cracking of isobutene on ultra-stable Y-zeolites at relatively high coke levels, a positive effect of coke formation www.elsevier.com/locate/cattod Catalysis Today 127 (2007) [17][18][19][20][21][22][23][24][25][26][27][28][29][30] on the formation of alkanes was observed [9]. The fact that both cracking and coking processes occur in a concerted way implies that they must be simultaneously investigated.…”