ASTM D4045 Test Method for Sulfur in Petroleum Products
ASTM D4045 Standard Test Method for Sulfur in Petroleum Products by Hydrogenolysis and Rateometric Colorimetry
7. Preparation of Apparatus
7.1 Turn on the furnace with temperature controls at minimum. Gradually increase furnace control over a 3-h period to approximately 1300°C to minimize thermal shock. Reverse the procedure when preparing for long-term storage. For shutdown at night and over weekends, reduce temperature to about 900°C but do not turn off the furnace. Furnace and quartz tubing life are extended by not cooling to room temperature.
7.2 Connect all tubing and fill prehumidifier outside the cabinet with water if this apparatus is being used, and final humidifier inside the cabinet with 5 % by volume acetic acid solution. Purge with inert gas, then close valve. Check all connections and repair any leaks that are found. (Warning - On instruments where electronics are in close proximity with the flow systems, exercise care if leak checking with a soap solution. A suitable method is to block the line that goes to the final humidifier and observe the flow meter. If the flow drops to zero, the flow systems are adequately leak-free.) Set hydrogen flow at 200 mL/min, and allow temperature to stabilize. (Warning - Extremely flammable gas under pressure.) Make final temperature adjustment to 1315 more or less 15°C. Use a standard thermocouple to verify temperature by inserting through a septum with hydrogen flowing at the rate noted above. Determine depth of insertion required, and always insert the hypodermic tip to the 550°C point (see 7.6). (Warning - The use of a humidifier gas wash bottle filled with approximately 250 mL of water is a potential safety hazard as hydrogen pressure may build up inside the container. The user of this test method should take appropriate safety measures to prevent an accidental injury, if the humidifier gas wash bottle is used in the analysis.)
7.3 Prepare the sample injection drive. Check to be sure desired injection rate is obtained at various settings. Verify that erratic pulses of fast drive do not occur when the drive range is switched. Pulses of high sample flow above 15 µL/min will cause carboning and spurious readings.
7.4 Install sensing tape, and turn H2S readout analyzer on.
7.5 Connect the recorder and adjust the zero to desired position with hydrogen flowing.
7.6 Fill syringe with blank reference standard solution, typically isooctane, insert the needle through the septum to the 550°C temperature zone, and clamp to the syringe drive. At high temperature the hot needle may absorb sulfur and at lower temperature heavy compounds may not evaporate. Set the syringe drive rate desired, normally 6 µL/min, maximum with 200 mL/min hydrogen flow. Drive rate may be increased for increased sensitivity up to the point at which carbon is formed. (Hydrogen flow at 500 mL/min allows injection of 15 µL/min; however, dibenzothiophene conversion will be low.)
