Patent ID: 7754068

Claim:
A process for the selective hydrodesulfurization of naphtha streams containing olefins and organosulfur compounds, said process including: a) contacting said naphtha feed containing olefin content in the range of 20 to 50 mass % and sulfur in the range of 200 to 7,000 mg/kg in a first reaction stage, under hydrodesulfurization conditions comprising temperature from 200 to 420° C., pressure from 0.5 to 5.0 MPag, and space velocity LHSV between 1 to 20 h −1 , in a reactor charged with a sulfided hydrorefining catalyst, with a stream of hydrogen and at least one added non-reactive compound and limiting H 2 S at the reactor inlet to not more than 0.1% by volume, in order to yield an effluent; b) removing H 2 S from the first reaction stage effluent so as to obtain a partially hydrodesulfurized naphtha; and c) directing said naphtha obtained in step b) towards a second reaction stage, in a reactor charged with a hydrorefining sulfided catalyst, under hydrodesulfurization conditions similar to those of the first stage, and contacting said partially hydrodesulfurized naphtha with a stream which is a mixture of H 2 and at least one added non-reactive compound, and limiting H 2 S at the reactor inlet to not more than 0.05% by volume, wherein said process comprises: (i) in the said first reaction stage: the said hydrorefining catalyst is made up of a more active catalyst for HDS while the H 2 fraction in the mixture of H 2 and at least one added non-reactive compound is higher than the said H 2 fraction added to the said second reaction stage; (ii) in the said second reaction stage: the said hydrorefining catalyst is made up of a less active catalyst for HDS, said second stage catalyst being distinct from the said first stage catalyst, and the H 2 fraction in the mixture of H 2 and at least one added non-reactive compound is lower than said H 2 fraction present in the said first reaction stage, and wherein (iii) the said first reaction stage catalyst is more active towards HDS than the said second reaction stage catalyst since said first reaction stage catalyst requires, for obtaining the same sulfur conversion and same hydrorefining conditions, lower temperature than the said second reaction stage catalyst for obtaining the same sulfur content when processing the same naphtha feed, whereby a hydrodesulfurized naphtha of improved selectivity relative to the state-of-the-art technique is recovered at the end of the said process, wherein the mole ratio, H 2 /(H 2 +non-reactive compound), is between 0.2 and 1.0 for the first reaction stage, and between 0.2 and 0.7 for the second reaction stage.