Patent ID: 6306287
Filing Date: 2001-10-23
Classification: C10G

Abstract:
A process for hydrotreating a heavy hydrocarbon fraction containing asphaltenes, sulphur-containing impurities and metallic impurities in at least two steps, comprising during the first step, hydrodemetallisation, passing the heavy hydrocarbon fraction and hydrogen over a hydrodemetallisation catalyst under hydrodemetallisation conditions, and during the subsequent second step, passing resultant effluent from the first step over a hydrodesulphurisation catalyst under hydrodesulphurisation conditions, in which the hydrodemetallisation step comprises one or more hydrodemetallisation zone with fixed catalyst beds preceded by at least two hydrodemetallisation guard zones also with fixed catalyst beds, disposed in series for cyclic use comprising successive repetition of steps b) and c) defined below:a) a step comprising passing the heavy hydrocarbon fraction through all the guard zones for a period of at most equal to the deactivation time and/or clogging time for one thereof;b) a step during which the deactivated and/or clogged guard zone is short-circuited and the catalyst the short circuited guard zone contains is regenerated and/or replaced by fresh catalyst; andc) a step during which the guard zones are all used together, the guard zone where the catalyst has been regenerated and/or replaced by fresh catalyst during the preceding step, being reconnected, and said step being carried out for a period at most equal to the deactivation and/or clogging time for one of the guard zones;said process being characterized in that a quantity of gas oil representing 0.5% to 80% by weight with respect to the weight of the hydrocarbon feed is introduced into the inlet to the first functioning guard zone at the same time as the feed; andsaid process further comprises passing product from the hydrodesulphurisation to an atmospheric distillation zone, from which an atmospheric distillate is recovered and recycling at least a portion of said atmospheric distillate comprising a gas oil to the inlet of the first functioning guard zone and recovering an atmospheric residue.