A.FLUID CATALYTIC CRACKING/a.PROCESS(Contd.)
Q.4 : What reactions lead to acetone formation and how they can be mitigated in the FCC
butane/butylenes stream?
A.4 : The presence of significant acetone in the products from an FCC GRU would be surprising given the contact with water which occurs in the front end of the plant.One potential source is an extraneous stream such as stream from a cumene unit which is fed to the back end of the GRU.
Q.5:What variables influence gasoline aromatics? In particular,please address feed prorties,catalyst,and FCC operating conditions.
A.5:The three key variables which influence gasoline aromatics are feed properties,catalyst properties,and unit operating conditions.
Lower feed hydrogen content translates to lower product hydrogen,i.e.,more aromatic products.Naphthenic feeds make more aromatic products compared to paraffinic feeds.
Catalyst properties are also important.Low hydrogen transfer(low unit cell size/low rare earth) catalyst produces a more aromatic gasoline.ZSM-5 increases aromatics by concentration effect: olefins are cracked out,leaving behind aromatics.
Operating conditions are the third major factor.Increased riser temperature increases gasoline aromatics by dealkylation of larger aromatics and cracking of paraffins,leaving aromatics behind.Cutting deeper to produce more gasoline also increases aromatics,since the aromatics tend to be concentrated in the heavier fractions.
