ASTM D5776-21 PDF

Overview

ASTM D5776-21: Standard Test Method for Bromine Index of Aromatic Hydrocarbons by Electrometric Titration establishes a procedure to determine the bromine index in aromatic hydrocarbons. This test method provides a measurement of bromine-reactive substances present, particularly trace amounts of unsaturated compounds, in industrial aromatic hydrocarbons. It is widely used by refiners, chemical manufacturers, and analytical laboratories to set product specifications, conduct quality control, and support research and product development efforts.

The bromine index is a critical quality indicator reflecting the content of olefinic (unsaturated) impurities, which can influence product stability, reactivity, and suitability for downstream processing.

Key Topics

• Scope of Application

  • Applicable to aromatic hydrocarbons containing trace levels of olefins
  • Particularly suited to materials with bromine indexes below 35 mg Br/100 g
  • Covers substances substantially free from lighter components than isobutane and with a boiling end point below 288 °C

• Test Method

  • Utilizes an electrometric titration to indicate endpoint via a voltage change when free bromine appears
  • Requires fixed end-point electrometric titration apparatus, specific chemical reagents, and controlled titration process

• Significance and Use

  • Used for setting product specifications and internal quality control
  • Assists in research and development on aromatic hydrocarbons
  • Provides an overall indication of olefin content but does not differentiate between types of aliphatic unsaturation

• Results and Reporting

  • Bromine index reported in milligrams of bromine consumed per 100 grams of sample
  • Results are rounded in accordance with ASTM E29 practice on significant digits

• Quality Assurance

  • Recommends following established QA/QC protocols such as those found in ASTM D6809
  • Suggests interlaboratory studies to ensure reproducibility and comparability of results

Applications

ASTM D5776-21 is valuable across various sectors in the chemical and petrochemical industries. Its practical applications include:

• Product Specification
  • Verification of aromatic hydrocarbon streams for compliance with regulatory and customer specifications regarding unsaturate content.
• Process and Quality Control
  • Routine monitoring during production of chemicals such as xylenes, toluene, and benzene to ensure low levels of reactive impurities that could affect process equipment or product quality.
• Research and Development
  • Supporting analysis for formulation development or process modification, where knowing unsaturate content is essential for reaction design or stability trials.
• Interlaboratory Comparability
  • Facilitates consistent and reliable reporting between suppliers, manufacturers, and clients, ensuring trust in test results.

Related Standards

The following ASTM standards are commonly utilized in conjunction with ASTM D5776-21:

• ASTM D1159: Test Method for Bromine Numbers of Petroleum Distillates and Commercial Aliphatic Olefins by Electrometric Titration
• ASTM D1193: Specification for Reagent Water
• ASTM D3437: Practice for Sampling and Handling Liquid Cyclic Products
• ASTM D6809: Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
• ASTM E29: Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

These referenced standards provide additional guidance on quality control, test procedures, and proper sampling relevant to the effective implementation of ASTM D5776-21.

Keywords: ASTM D5776-21, bromine index, aromatic hydrocarbons, electrometric titration, quality control, olefin content, specification testing, chemical analysis, laboratory test method.