Hydrocarbon coking

Coke oven discharging (pushing) Hydrocarbons, coke dust Hoods to fans and venturi scrubbers, low-energy scrubbers followed by ESPs (may use water spray at oven outlet)... 

The activity and selectivity of catalyst HZSM5-1 was constant over 1 hour on stream although the formation of a linear hydrocarbon species at the catalyst was noticed. The IR spectra suggest that this species is a linear aliphatic hydrocarbon (coke precursor) increasing in concentration with time on stream [13], It is concluded that this species is adsorbed at the (catalytically inactive) Si-OH groups of the catalyst. During our measurements, the catalytically active Si-OH-AI groups were not blocked by this surface species and the product selectivity was not altered... 

Touring the pyrolysis of hydrocarbons, coke is unfortunately always formed in addition to ethylene, propylene, diolefins, aromatics, and other valuable hydrocarbons. Information available on coke formation up to 1965 has been reviewed by Pallmer and Cullis (1). Some (but not extensive) results obtained using an electron microscope have been reported. 

Coke formation will always be a potential problem in any high temperature process involving hydrocarbons. Coke and tars formed during reaction can deposit on reactor surfaces or in quench heat exchangers, and several effects have been observed in a steam cracker tube (4, 9 ). As the reaction proceeds the tube will accumulate coke towards the reactor exit, while the inlet zone remains relatively coke free, as a result of the induction time associated with the formation of tars and coke (J ). Gas phase reactants may adsorb and react on this bare metal, and the components of the gas phase in the reactor should and do reflect this interaction (4, 9, JO). Since carbon formation depends on the nature of the gas phase species, these interactions should also influence coke formation towards the exit of the ractor. Again, this is found to be the case (4, 9 - 11). 

Regeneration of catalysts CO2, THF, hexane, ethylbenzene, benzene Hydrocarbon, coke removal from catalysts... 

For a given type of hydrocarbon, coke deposition from re-paraffins displays a minimum for re-heptane from aromatics coke deposition increases for side chain with the possibility of forming a five-carbon ring (indenic structure) for naphthenes the coke deposition is higher in the case of five-carbon atoms rings (95,97). 

Materials problems must also be considered in selecting the regeneration temperature. In the presence of hydrocarbons, coke deposition occurs on zeolites as a result of the catalytic decomposition at temperatures as low as 100 °C, depending on the hydrocarbon compound, its partial pressure, and other factors. Severe oxidation occurs in activated carbon at slightly above 100 °C in the presence of trace amounts of oxygen. 

Another significant feature is that the coke generation is rigorously modeled and included in the deactivation and adsorption factor F for each reaction. The deactivation factor is a function of reactor pressure, adsorbed hydrocarbons, coke on catalyst and acid/metal function of the catalyst This feature allows us to calibrate the model to a variety of operating conditions and catalyst behavior. In this work, we model a CCR with a hydrotreated feed therefore, we do not include any significant changes in catalyst activity due to changes in add of the catalyst... 

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