Hydrogen Sulfide and Mercaptan Sulfur in Liquid Hydrocarbons by Potentiometric Titration

UOP Method 163-10: Hydrogen Sulfide and Mercaptan Sulfur in Liquid Hydrocarbons by Potentiometric Titration

For professionals in the petroleum refining, petrochemical, and chemical industries, accurately quantifying sulfur compounds is not just a matter of quality control, but also a critical aspect of process efficiency and regulatory compliance. UOP Method 163-10 provides an essential, industry-leading approach to determining hydrogen sulfide and mercaptan sulfur in liquid hydrocarbons, ensuring that your analytical processes are robust and reliable.

What is UOP Method 163-10?

UOP Method 163-10, published by UOP/ASTM International, is an authoritative standard detailing a potentiometric titration technique for the precise measurement of hydrogen sulfide (H₂S) and mercaptan sulfur (RSH) in various liquid hydrocarbon streams. Developed from proven methodologies, its primary purpose is to provide a reliable and reproducible means for laboratories to assess these specific sulfur contaminants, which can significantly impact product quality and operational integrity.

Scope & Purpose

This comprehensive standard governs the quantitative analysis of hydrogen sulfide and mercaptan sulfur in hydrocarbon samples that are liquid at ambient temperature and pressure. This includes typical feedstocks and products such as gasoline, naphtha, and light cycle oils. The method is specifically designed for quantitation down to 1.0 mass-ppm for hydrogen sulfide and 0.2 mass-ppm for mercaptan sulfur. It does not cover the determination of other sulfur species, such as thiophenes, or samples that are solid or gaseous under standard conditions.

Who Must Comply?

• • Primary audience: Laboratory technicians, analytical chemists, quality control analysts, and research scientists involved in hydrocarbon analysis.
• • Industries affected: Petroleum refining, petrochemical manufacturing, and the broader chemical processing sector.
• • Compliance nature: While often adopted as a best practice, compliance may be mandatory for specific contractual agreements, quality assurance programs, or regulatory requirements.
• • Enforcement: Compliance is typically verified through internal quality assurance protocols, third-party audits, and regulatory agency inspections where applicable.

Key Requirements Overview

The standard requires meticulous preparation of the potentiometric titration system, particularly the silver/silver sulfide electrode, to ensure accurate endpoint detection. Professionals must ensure that samples are handled swiftly and under a nitrogen blanket to prevent oxidation of mercaptans. Key provisions include the use of specific solvent systems, such as 2-propanol, and precise alcoholic silver nitrate titrant solutions of defined normality. The method also outlines procedures for interpreting titration curves, especially in the presence of free sulfur, and mandates the use of a nitrogen purge for volatile solvents to maintain sample integrity.

Related Standards & References

UOP Method 163-10 often works in conjunction with other analytical standards. UOP Method 41, "Doctor Test for Petroleum Distillates," provides a complementary qualitative test for certain sulfur compounds, offering an initial indication of potential issues. Furthermore, UOP Method 999, "Precision Statements in UOP Methods," provides essential guidance on understanding and applying the precision and bias statements specific to UOP methods, including 163-10, which is vital for inter-laboratory comparisons and quality control.