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    Home > Chemicals Industry > Chemical Technology > Electrochemical method for determination of trace oxygen in ethylene and propylene for industrial use (1)

    Electrochemical method for determination of trace oxygen in ethylene and propylene for industrial use (1)

    • Last Update: 2022-01-17
    • Source: Internet
    • Author: User
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    1 Scope

    This standard specifies the electrochemical method and electrochemical method of membrane-covered galvanic cells for the determination of trace oxygen in gaseous ethylene or propylene
    .

    This standard is applicable to the determination of trace molecular oxygen with a content of not less than 1mL/m³ in industrial ethylene and propylene
    .

    2 Reference standards

    The provisions contained in the following standards constitute the provisions of this standard through quotation in this standard
    .
    When this standard was published, the editions indicated were valid

    .
    All standards will be revised, and all parties using this standard should explore the possibility of using the latest version of the following standards

    .

    GB/T66821986 Analytical laboratory water specifications and test methods (neq ISO 3696: 1987)

    GB/T13289-1991 Industrial ethylene liquid and gas sampling method (req ISO 7382: 1986)

    GB/T13290-1991 Industrial Propylene and Butadiene Liquid Sampling Method (neq ISO 8563: 1987)

    3 Method summary

    3.
    1 Electrochemical method of membrane-covered primary cells

    When the gas flows at a constant rate through the measurement chamber equipped with a membrane-covered cell (fuel cell), the oxygen molecules in the gas diffuse through the polymer film covered on the cell surface, and a reduction reaction occurs at the cathode made of inactive metal.
    , Oxygen molecules get electrons from the external circuit:

    O 2 + 2H 2 O → 4OH 4E + -

    At the same time, the lead anode is corroded by the KOH in the water-containing colloidal electrolyte, and an oxidation reaction occurs, and electrons are output to the external circuit:

    2OH - + PB-> of PbO + H 2 O + 2E

    The total reaction of the primary battery is:

    2Pb+O 2 =2PbO

    The current generated by the external circuit is proportional to the partial pressure of oxygen in the gas.
    When the total pressure is constant, the current is proportional to the concentration of oxygen in the gas

    .

    3.
    2 Electrolysis electrochemical method

    When the gas flows through the measuring chamber of the electrolytic electrochemical method instrument at a constant rate, the oxygen molecules in the gas diffuse through the porous material and enter the electrolytic cell containing the potassium hydroxide electrolyte.
    The oxygen molecules are driven by the applied DC voltage.
    A reduction reaction occurs at the cathode made of platinum, gold or graphite, and the oxygen molecules get electrons from the external circuit:

    O 2 + 2H 2 O → 4OH 4E + -

    At the same time, the OH - in the electrolyte undergoes an oxidation reaction on the surface of the inert anode and outputs electrons to the external circuit:

    4OH - → O 2 + 2H 2 O + 4E

    The reaction does not consume the anode material, and the molecular oxygen generated by the reaction is discharged through the porous material near the anode
    .
    The size of the electrolysis current is proportional to the concentration of oxygen in the sample gas

    .

     

     

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