Nucleation growth process, coking

Coking of zeolites can be considered as a nucleation-growth process. The key step is the retention of secondary reaction products in the micropores (nucleation). At high reaction temperatures this retention is generally due to a steric blockage (trapping), while at low temperatures it is mainly due to the low volatility of the secondary products (5). 

The kinetics of graphitization of cokes has been shown to be a growth process and not a nucleation-based process with usually a single-valued activation energy, reported at 962 60 kJ/mol (230 15 kcal/mol) in the 2300 2900°C temperature range for typical industrial cokes.l ... 

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