Naphtha desulfurization process

Abstract

This invention relates to a process for selectively desulfurizing naphtha. More particularly, a low sulfur naphtha feed containing less than 500 wppm sulfur is hydrodesulfurized using a hydrodesulfurization catalyst and a hydrogen treat gas containing at least about 50 vppm hydrogen sulfide followed by mercaptan removal or conversion.

Description

FIELD OF THE INVENTION [0001] This invention relates to a process for selectively desulfurizing naphtha. More particularly, a low sulfur naphtha feed is hydrodesulfurized using a hydrodesulfurization catalyst and a hydrogen treat gas containing hydrogen sulfide followed by mercaptan removal or conversion. BACKGROUND OF THE INVENTION [0002] Environmental regulations covering the sulfur content of fuels for internal combustion engines are becoming more stringent with regard to allowable sulfur in fuels. It is anticipated that motor gasoline sulfur content may need to meet a sulfur limit of 30 wppm with possible further mandated reductions. The feedstocks for motor gasoline are typically catalytically cracked naphthas, which contain substantial amounts of sulfur and olefins. [0003] A common method for reducing the sulfur content of feedstocks is by hydrotreating using catalysts that convert sulfur-containing species to hydrogen sulfide. The extent to which hydrotreating lowers the sulf...

AI Technical Summary

Benefits of technology

The present invention relates to a process for hydrodesulfurizing a low sulfur naphtha feedstock. The process involves contacting the feedstock with a catalyst in a first reaction stage under hydrodesulfurization conditions. The resulting product has a reduced amount of mercaptan sulfur. In a second stage, the mercaptan sulfur is at least partially removed or converted from the first stage product to obtain a second stage product with a reduced amount of mercaptan sulfur. The technical effect of this invention is that it allows for the efficient hydrodesulfurization of low sulfur naphtha feedstock while maintaining catalyst activity and reducing the amount of mercaptan sulfur.

Problems solved by technology

However, such severe hydrotreating conditions normally result in a loss of molecules contributing to desirable octane properties either by cracking to non-fuel molecules or hydrogenation of olefins to molecules having lower octane rating.

However, such adjustments result in further loss of desirable molecules contributing to high octane.

This then results in increased production costs to produce high octane fuels because of the need to boost octane through added process steps such as isomerization, blending or addition of octane boosting additives.

The use of such catalysts in a low sulfur feed may lead to catalyst deactivation with attendant loss in catalyst activity and selectivity.

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