T/SXCIES 002-2020 The determination method of moisture content in crude benzene

Scope

Main Technical Content: Method for Determining the Water Content in Crude Benzene 1 Scope This standard provides a method for determining the water content in crude benzene, including test instruments, test procedures, result calculation, and repeatability. It applies to crude benzene obtained from high-temperature coking processes. 2 Normative References The following documents are essential for the application of this standard. For dated references, only the version dated is applicable. For undated references, the latest version (including all amendments) is applicable. - GB/T 1999: Sampling Methods for Coking Oil Products - GB/T 8170: Rules for Rounding Values and Determination and Judgment of Limit Values - GB/T 6682: Specifications and Test Methods for Water Used in Analytical Laboratories 3 Method I: Karl Fischer Titration 3.1 Principle In an organic reagent containing methanol, the water in the sample reacts with the Karl Fischer reagent as follows: H2O + I2 + SO2 + C5H5N (or C3H4N2) → C2H5N?HI (or C3H4N2?HI) + C5H5N?SO3 C5H5N?SO3 (or C3H4N2?HI) + CH3OH → C5H5N?HSO4CH3 (or C3H4N2IHSO4CH3) During the titration reaction, a double platinum electrode connected to a power supply is used to track the current signal. When only iodide is present in the solution, the electrode is polarized and no current flows. At the titration endpoint (when the water reaction is complete), free iodine is present in the solution, causing the electrode to depolarize and a sudden increase in current. One electrode oxidizes iodide (Iˉ), while the other electrode reduces the same amount of iodine (I2). Based on the volume of Karl Fischer reagent consumed, the water content in the sample can be calculated. 3.2 Reagents 3.2.1 Anhydrous methanol: Analytical grade. 3.2.2 Karl Fischer reagent: With a titratability of 3.5 mg/mL to 4.5 mg/mL. The titratability for water must be recalibrated before each use. 3.2.3 Deionized water: Should meet the requirements of

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