Trace metal contaminants such as silicon and arsenic can either poison expensive catalysts, or in case of iron, cause equipment corrosion in the refinery process where naphtha is used as feedstock. Therefore it is essential to analyze the trace metals in naphtha, so necessary actions can be taken before they cause serious problems.
Naphtha Analysis for Trace Elements
Naphtha—a product of crude oil refinery
Naphtha is a generic term referring to a class of hydrocarbons produced in the first step of distillation of crude oil refinery, and it can also come from coal tar. Naphtha products can be divided into two categories: 1) light naphtha containing 6 carbon atoms or less with low initial and final boiling points, and 2) heavy naphtha containing more than 6 carbon atoms with higher initial and final boiling points.
Different regions and refineries produce different compositions and properties of naphtha. Naphtha has two primary uses:
- As the major component in fuel production to be catalytically reformed to produce a high-octane gasoline blending component.
- As a feedstock for steam cracking to produce petrochemical products such as ethylene, propylene, and pyrolysis gasoline.
Why analyze naphtha for trace elements
Using ICP-OES with a cooled spray chamber for naphtha trace element analysis
Analyzing naphtha for trace element analysis is performed by ICP-OES. For this analysis, it is important to use a cooled spray chamber (-10°C) to cool down the sample and reduce the volatility.
Here’s why: Using ICP-OES to analyze organic solvents raises a serious concern. The ICP-OES standard sample introduction transports a volatile solvent such as naphtha much more efficiently compared to aqueous samples, resulting in instable plasma. Therefore it is important to reduce volatility of naphtha before introduction into the plasma. One option is to dilute the naphtha sample with a less volatile solvent such as kerosene. However, the dilution lowers the sensitivity for analysis. A better option is to use a cooled spray chamber (-10°C) to cool down the sample and reduce the volatility.
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