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4.4.1. Selective hydrogenation of C
3 
 
Figure B-4-1: Flow sheet of the C
3
 selective hydrogenation process 
Feed section 
The feed to the reactor consists of both fresh and recycle C
3
cut streams. The recycle stream 
comes from the separator. The recycle stream and the fresh stream are first mixed together 
before being mixed with the hydrogen make-up in the static mixer. 
 
Reactor section 
The total stream enters the reactor top and flows downwards through the fixed catalyst bed. 
The hydrogenation of MA and PD occurs selectively according to the following reaction: 
CH
3
─ C CH + H
2
CH
2
═ C ═ CH
2
+ H
2
CH
3
─ CH ═ CH
2
 
 
The reactor effluent is then condensed and cooled down in a cooler. 
A spare reactor is foreseen in order to allow the catalyst reduction, reactivation or in-situ 
regeneration operations in one reactor while the other one is in operation. 
Hydrogen 
Raw C3 
cut 
CW 
separator 
recycle 
pump 
Hydrogenated 
C3 cut 
hydrogenation 
reactors 

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For catalyst reduction, reactivation or regeneration operations, the gas is sent into the reactor 
at the required temperature and the effluent is sent to battery limit for disposal (flare or 
cracker furnace fire box). 
Separator section 
The reactor effluent is then received in a separator where the off-gas is purged if necessary 
(the off-gas purged is recycled). Finally the liquid phase is pumped out and divided into two 
streams: the recycle to the reactor and the product routed to battery limit. 
 
4.4.2. Selective hydrogenation of C