Naphtha sulphur content

In naphtha reforming, hydrotreatment is always applied to protect the platinum-containing catalyst against sulphur poisoning. The specification of sulphur content for the feed for the reforming unit is less than 1 ppm. 

This plot shows that most of the sulphur is concentrated in the heavier fractions. Even for crude oils with high sulphur content the level of sulphur in the naphtha fraction can be low (below 100 ppm). This... 

Commercial naphthas are complex mixtures of a large number of different isomers and are generally characterized by specific gravity and boiling curves (TBP curves or ASTM D86). The relevant properties of different straight run naphthas are reported in Table VIII. The sulphur content is usually lower than 2% and nitrogen is in the order of a few ppm. Light and heavy naphthas are... 

As well as naphtha, some operations use gas-oil as the feedstoek. Gas oil is the crude oil fraction boiling typically at 220°C to 360°C, and some processing vacuum gas oils boiling typically at 360°C to 550 C. However, in some instances these crackers have been revamped to use the atmospheric column bottoms (sometimes called long residua) where the crude oil being processed has the appropriate properties of high wax (linear paraffin) content and low metal content (which otherwise promotes excessive coke formation). This material is often referred to as Low Sulphur Waxy Residual Fuel Oil (LSWR). 

Although gas oils obtained from the atmospheric distillate still remain the main source of diesel fuels, in order to cope with the increased consumption of naphtha and middle distillates almost all refineries in Romania use conversion processes such as fluid catalytic cracking on vacuum distillates and coking or visbreaking on residue. These processes generate middle distillates with higher olefins, diolefins, sulphur, nitrogen and aromatics content compared to gas oil obtained from an atmospheric distillation unit... 

In adiabatic pre-reformers, it is possible to process naphtha with a final boiling point up to 220 C and an aromatic content up to 30%. It may be possible to process even heavier feedstocks depending on the operating conditions. During the operation of an adiabatic pre-reformer, progressive deactivation takes place, mainly by sulphur poisoning. This phenomenon causes the temperature profile to move in the flow direction (Davies et al., 1967). 

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