SH/T 0172-2001 Determination of sulfur content in petroleum products (high-temperature method)

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Card type: Test method

1. Method number / full name / English name / replacement relationship

• Method number: SH/T 0172-2001
• Chinese full name: Determination of sulfur content in petroleum products (high-temperature method)
• English name: Determination of sulfur in petroleum products (high-temperature method)
• Replacement relationship: replaces SH/T 0172-92
• Adoption relationship: equivalent adoption of ASTM D1552-95
• Publication/implementation: published on 2001-11-23, implemented on 2002-01-01
• Issuing authority: State Economic and Trade Commission

2. Scope of application and non-applicability

• 1.1 specifies three methods for determining total sulfur content in petroleum products (including additives and additive-containing lubricating oils): the first two respectively use an induction-type furnace and a resistance-type furnace for high-temperature decomposition, followed by iodate determination; the third uses a resistance-type furnace for high-temperature decomposition followed by detection with an infrared detection system.
• 1.2 is applicable to petroleum products with a boiling point higher than 177℃ and a sulfur content not lower than 0.06%(m/m).
• 1.3 can determine sulfur content up to 8%(m/m) in petroleum coke.
• 1.4 Interference notes: the iodate detection system has no interference when the chlorine content is lower than 1%(m/m); the infrared detection system allows the presence of higher chlorine content. When the nitrogen content exceeds 0.1%(m/m), interference may occur with the iodate system (the degree depends on the type of nitrogen compound and combustion conditions); nitrogen does not interfere with the infrared detection system. Alkali metals, alkaline earth metals, zinc, phosphorus, and lead do not interfere with either system.
• 1.5 Safety note: hazardous materials, operations, and equipment may be involved, and the user is responsible for establishing safety and protective measures.
• Not applicable: no explicit non-applicable clauses are provided in the available source.

3. Method principle

• 3.1 Iodate detection system: the sample is burned in a high-temperature oxygen stream, and about 97% of the sulfur is converted to sulfur dioxide. A correction factor is required to obtain accurate results. The combustion products are passed into an absorber containing an acidic solution of potassium iodide and starch indicator, and potassium iodate standard solution is added to make the solution light blue. As combustion proceeds and the blue color fades, potassium iodate standard solution is added. The sulfur content is calculated from the total amount of potassium iodate standard solution consumed during combustion.
• 3.2 Infrared detection system: after weighing, the sample is placed in a special porcelain boat and pushed into a 1371℃ combustion furnace with an oxygen atmosphere, where sulfur is burned and converted to sulfur dioxide. After moisture and dust are removed with a trap, detection is performed with an infrared detector. The microprocessor calculates the sulfur content based on sample mass, detection signal value, and a pre-determined correction factor, and prints the sample identification number and sulfur content in mass percent. The correction factor is obtained by determining standard substances similar to the sample type.

4. Reagents and materials (purity / preparation)

• 6.1 Water: meets the technical requirements for grade three water in GB/T 6682.
• 6.2 Aluminum oxide: analytical reagent.
• 6.3 Magnesium oxide: analytical reagent.
• 6.4 Magnesium perchlorate: analytical reagent. (Warning: handling requires special care, avoid contact with acids and organic matter, and reaction with fuel may be very violent)
• 6.5 Vanadium pentoxide: analytical reagent, anhydrous powder.
• 6.6 Phosphorus pentoxide: analytical reagent.
• 6.7 Hydrochloric acid: analytical reagent, relative density 1.19. (Warning: toxic and corrosive; ingestion may be fatal; liquid and vapor can cause severe burns)
• 6.8 Sulfuric acid: analytical reagent, relative density 1.84. (Warning: toxic; corrosive; strong oxidizer)
• 6.9 Potassium aluminum sulfate (alum): analytical reagent, used for instrument calibration.
• 6.10 Potassium iodide: analytical reagent.
• 6.11 Potassium iodate: analytical reagent.
• 6.12 Soluble starch: chemical reagent.
• 6.13 Hydrochloric acid solution: dilute 30mL hydrochloric acid to 2L with water.
• 6.14 Starch-potassium iodide solution: add 9g starch to 15mL water to form a paste, add it to 500mL boiling water with stirring, after cooling add 15g potassium iodide, and dilute to 1L with water.
• 6.15 Potassium iodate standard solution (0.06238mol/L, 1mg S/mL): dissolve 2.225g potassium iodate, dried to constant weight at 180℃, in water, dilute to 1L, and mix uniformly.
• 6.16 Potassium iodate standard solution (0.006238mol/L, 0.1mg S/mL): accurately measure 100mL potassium iodate standard solution (0.06238mol/L, 1mg S/mL) and inject into a 1L volumetric flask, dilute to the mark with water, and mix uniformly.
• 6.17 Potassium iodate standard solution (0.01248mol/L, 0.2mg S/mL): accurately measure 200mL potassium iodate standard solution (0.06238mol/L, 1mg S/mL) and inject into a 1L volumetric flask, dilute to the mark with water, and mix uniformly.
• 6.18 Oxygen: especially dry, purity at least 99.5%, and no detectable sulfur in blank determination. (Warning: oxygen strongly supports combustion)
• 6.19 Soda asbestos: 8 mesh to 20 mesh.
• 6.20 Special materials for the induction-type furnace:
  • 6.20.1 Tin: 20 mesh to 30 mesh.
  • 6.20.2 Iron chip catalyst: sulfur content not greater than 0.005%(m/m).

5. Instruments and equipment

• 5.1 Combustion and iodate detection system
  • 5.1.1 Combustion furnace: two types may be used, the main difference being the method of obtaining high temperature.
    • 5.1.1.1 Induction-type furnace: heated by a high-frequency induction method, under the conditions specified in Chapter 9, the temperature of the sample combustion zone reaches at least 1482℃, and an additional induction coil must be installed above the combustion zone (as shown in Figure 1).
    • 5.1.1.2 The minimum output power of the furnace working coil is 500W, the minimum input rated power must be 1000W, the mass of the iron chip catalyst is accurate and weighed to ±0.05g, and the maximum plate current is between 350mA and 450mA. (Warning: can cause high-frequency burns and high-voltage electric shock, corresponding protective measures should be taken; the furnace power must be cut off during each repair and adjustment)
    • 5.1.1.3 Resistance-type furnace: can obtain a high temperature of at least 1371℃.
  • 5.1.2 Absorber: the same as the absorber in test method GB/T 11131. (Note: automatic titrators designed specifically for the iodometric method are suitable for both furnace types and can combine absorption and titration-to-endpoint functions)
  • 5.1.3 Burette: a 25mL standard burette or automatic titration equipment matched with a dedicated combustor is suitable (see Note in 5.1.2).
• 5.2 Combustion and infrared detection system: includes an automatic balance, oxygen flow controller, drying tube, combustion furnace, infrared detector, and microprocessor. The furnace should be able to maintain an operating temperature of about 1350℃.
• 5.3 Other instruments: additional equipment required according to the combustion device, such as crucibles, combustion boats, crucible covers, boat push rods, separation disks, combustion tubes, sample injectors, oxygen flow indicators, and oxygen drying equipment. Additional equipment determined by the furnace type can be obtained from the combustion equipment manufacturer. To determine the lower sulfur content given in Chapter 1, ceramic articles used for the induction-type furnace must be calcined in a muffle furnace at 1371℃ for at least 1h before use.
• 5.4 Sieve: 100 mesh.

6. Recommended operating conditions

• 8.1 Induction-type furnace: oxygen passes sequentially through (1) sulfuric acid, (2) soda asbestos, (3) magnesium perchlorate or phosphorus pentoxide for purification. A rotameter is installed between the purification system and the furnace. The upper end of the glass tube connecting the furnace and the absorber is plugged with a glass wool plug to intercept tin oxides. Connect the outlet at the end of the combustion tube to the absorber with a glass tube using a latex tube, and keep the connecting tube as short as possible. Adjust the oxygen flow rate to 1L/min±0.05L/min. Add 65mL hydrochloric acid solution and 2mL starch-potassium iodide solution to the absorber, and add enough corresponding potassium iodate standard solution (see Table 1) to make the solution light blue as the titration endpoint. Adjust the burette liquid level to zero. Turn on the furnace switch and preheat for at least 1min before determining samples.
• 8.2 Resistance-type furnace: oxygen passes sequentially through (1) sulfuric acid, (2) soda asbestos, (3) magnesium perchlorate or phosphorus pentoxide for purification. A rotameter is installed between the purification and the resistance furnace. Turn on the power and adjust the furnace control device so that the temperature is constant at 1316℃±14℃. Adjust the oxygen flow rate to 2L/min±0.1L/min. Add 65mL hydrochloric acid solution and 2mL starch-potassium iodide solution to the absorber, and add a few drops of the corresponding potassium iodate standard solution (see Table 2) to make the solution light blue. Adjust the burette liquid level to zero.
• 8.3 Resistance-type furnace-infrared detection system: install and calibrate the instrument according to the manufacturer's instructions. Install the microprocessor and power supply system, set the oxygen pressure and flow rate, and set the furnace temperature to 1371℃.
  • 8.3.1 For a new anhydrous gas purification system, adjust the instrument using four coal samples.
  • 8.3.2 Calibrate the automatic balance according to the manufacturer's instructions.
• Table 1 Sample amount for induction-type furnace:
  • Sulfur content 0 to 2%(m/m): sample amount about 90mg, potassium iodate standard solution concentration 0.006238mol/L
  • Sulfur content 2 to 4%(m/m): sample amount 50 to 90mg, potassium iodate standard solution concentration 0.006238mol/L
  • Sulfur content 4 to 10%(m/m): sample amount 50 to 90mg, potassium iodate standard solution concentration 0.01248mol/L
  • Sulfur content >10%(m/m): for sample amount see the note in 11.1.1, for potassium iodate standard solution concentration see the note in 11.1.1
• Table 2 Sample amount for resistance-type furnace:
  • Sulfur content 0 to 2%(m/m): sample amount 100 to 200mg, potassium iodate standard solution concentration 0.006238mol/L
  • Sulfur content 2 to 5%(m/m): sample amount 100 to 200mg, potassium iodate standard solution concentration 0.01248mol/L
  • Sulfur content 5 to 10%(m/m): sample amount 100 to 200mg, potassium iodate standard solution concentration 0.06238mol/L
  • Sulfur content >10%(m/m): for sample amount see the note in 11.1.1, for potassium iodate standard solution concentration see the note in 11.1.1

7. Sampling and sample preparation

• 7 Sampling: sample according to GB/T 4756.
• 10 Preparation of petroleum coke samples:
  • 10.1 The analytical sample must be representative.
  • 10.2 The sample is ground and screened through a 100 mesh sieve.
  • 10.3 After screening, the sample is dried to constant weight under the conditions of 105℃ to 110℃.

8. Analytical procedure

• 11 Test procedure for the induction-type furnace
  • 11.1 Preparation of the test sample: Add a layer of aluminum oxide or magnesium oxide with a thickness of 3.2mm～4.8mm in the test sample crucible. Use the end of a stirring rod to dig a groove in the aluminum oxide or magnesium oxide layer. Weigh the crucible to the nearest 0.1mg. According to Table 1, accurately weigh an appropriate test sample into the groove. Cover the test sample with a separable disk; to obtain the required temperature, a pre-weighed iron sheet catalyst must be placed on the separable disk. The mass of the iron sheet catalyst is usually between 1.2g～2.0g (weighed to the nearest ±0.05g). Sprinkle approximately 0.5g of tin on the iron sheet catalyst, cover the crucible lid, and place the crucible on the furnace base.
    • 11.1.1 In an induction-type furnace, the amount of organic test sample must not be greater than 10%.
      • Note 1: For samples with a sulfur content greater than 10%(m/m), a potassium iodate standard solution of higher concentration (e.g., 0.06238mol/L) may be used. The test sample amount and the concentration of the potassium iodate standard solution should be selected so that the required standard titration solution does not exceed 25mL.
      • Note 2: The use of the separable disk is optional.
  • 11.2 Combustion and titration: Turn on the plate current switch, and after preheating for 1min, raise the furnace base and fix it in a certain position. After the plate current fluctuates for a few seconds, it gradually rises to the maximum value. Add an appropriate amount of potassium iodate standard solution (see Table 1) to the absorber to keep the solution blue. If the absorber solution completely becomes colorless, abandon this determination. As the rate of sulfur dioxide generation decreases, add potassium iodate standard solution so that the blue depth of the titrated solution at the end of combustion is similar to that at the beginning. When the color is maintained for at least 1min and the plate current significantly decreases, combustion is complete. Record the volume of potassium iodate standard solution used to titrate the generated sulfur dioxide.
  • 11.3 Blank determination: A blank determination shall be performed whenever a new crucible, material, or reagent is used. The test procedure is the same as above, but no test sample is added.
• 12 Test procedure for resistance-type furnace
  • 12.1 Preparation of the test sample: In a combustion boat, weigh an appropriate test sample according to Table 2, add 100mg±5mg vanadium pentoxide, and completely cover the mixture of test sample and vanadium pentoxide with aluminum oxide powder.
  • 12.2 Combustion and titration: Place the porcelain boat in the cold zone at the entrance of the combustion tube. Use the special equipment provided by the instrument manufacturer to push the porcelain boat containing the test sample to the hot zone of the combustion tube. The pushing speed of the porcelain boat should be as consistent as possible with the generation rate of sulfur dioxide. Add an appropriate amount of potassium iodate standard solution (see Table 2) to the absorber to keep the solution blue. If the absorber solution completely becomes colorless, abandon this determination. As the rate of sulfur dioxide generation decreases, add potassium iodate standard solution so that the blue depth of the titrated solution at the end of combustion is similar to that at the beginning. When the color is maintained for at least 1min, combustion is complete. Record the volume of potassium iodate standard solution used to titrate the generated sulfur dioxide.
  • 12.3 Blank determination: A blank determination shall be performed whenever a new combustion boat, material, or reagent is used. The test procedure is the same as above, but no test sample is added.
• 13 Test procedure for resistance-type furnace-infrared detection system
  • 13.1 Heat the system so that the combustion furnace reaches the operating temperature.
  • 13.2 Ensure the test sample is homogeneous and take the sample as follows: for liquid test samples take 0.13g, for solid test samples take 0.4g. When the sulfur content is expressed as a mass percentage, the number of weighings must be less than or equal to four when using a SC32 type instrument; the number of weighings must be less than or equal to two when using a SC132 type instrument. For other instruments, refer to the instrument manual provided by the manufacturer.
  • 13.3 Determine and store the system blank value.
  • 13.4 Add the test sample to the combustion boat and weigh it, recording the net mass. Multiple weighings may be performed before a series of combustions, and the weighed masses are stored in the microprocessor.
    • 13.4.1 Evenly spread magnesium oxide powder in the combustion boat up to one third of its volume.
    • 13.4.2 Use a medicine spoon to make a groove in the magnesium oxide powder layer.
    • 13.4.3 Place the combustion boat on the balance and weigh an appropriate amount of test sample into the groove in the magnesium oxide powder. Input the test sample mass into the microprocessor.
    • 13.4.4 Remove the combustion boat from the balance and add more magnesium oxide powder into the boat up to two thirds of its volume.
      • Note 1: If poor repeatability is encountered for special oil samples, vanadium pentoxide or a combustion aid produced by the American company Leco (LECO)) (C-Aid)) may be used instead of magnesium oxide.
      • Note 2: Vanadium pentoxide can corrode ceramic furnace tubes and must be used with caution.
  • 13.5 Introduce oxygen and push the combustion boat into the furnace.
  • 13.6 After the analysis is completed, read the result from the microprocessor.
  • 13.7 Remove the used combustion boat from the furnace.
  • 13.8 Repeat the operation until the difference between two results is less than the repeatability requirement of the method.

9. Qualitative and quantitative determination and calculation formulas

• 9 Instrument calibration
  • 9.1 Iodate method
    • 9.1.1 Determination of alum factor
      • 9.1.1.1 Because the rapid combustion method involves the reversible reaction 2SO₂+O₂⇌2SO₃, it is impossible to convert all sulfur to sulfur dioxide. This equilibrium reaction depends on temperature; in an oxygen stream above 1316℃, about 97% of the sulfur is converted to sulfur dioxide. Alum can be used to calibrate the instrument to ensure that the furnace position is properly adjusted so that the furnace temperature reaches the required temperature. Depending on the type of combustion equipment used, use 15mg±0.1mg alum to determine the alum factor according to the procedures described in Chapter 9 to Chapter 12. The same materials shall be used when determining the alum factor and the correction factor for unknown samples. For example, vanadium pentoxide has a certain effect, and this effect shall be taken into account when using a resistance-type furnace to determine unknown samples.
      • 9.1.1.2 The alum factor is calculated according to formula (1):
        • Alum factor (AF) = (SA × WA) / (100(V₀ − Vb) × C)
        • Where: SA— sulfur content of the alum used, %(m/m); WA— mass of the alum used, mg; V₀—volume of potassium iodate standard solution used in determining the alum factor, mL; Vb— volume of potassium iodate standard solution used in the blank determination, mL; C— potassium iodate standard solution used in determining the alum factor, each milliliter of which is equivalent to the mass of sulfur, mg S/mL.
      • 9.1.1.3 The alum factor should be in the range of 1.02～1.08. If the measured alum factor is less than 1.02, then before repeating the determination of the alum factor, verify the sulfur content in the alum and the mass of sulfur equivalent to the potassium iodate standard solution separately. If the alum factor is greater than 1.08, adjust the instrument according to the manufacturer's instrument manual and then repeat the determination of the alum factor.
    • 9.1.2 Determination of correction factor
      • 9.1.2.1 Because the volatility of the test sample may also affect the relative recovery of sulfur originally present in the test sample converted to sulfur dioxide, a correction factor must be determined. Use a sample with a known accurate sulfur content and similar in type to the unknown sample, and perform the determination according to the procedures described in Chapter 9 to Chapter 12. (Note: Sulfur content samples for this standard may also be prepared according to Appendix A)
      • 9.1.2.2 For infrared detection systems, determine the correction factor for the specific type of test sample used for analysis (lubricating oil, petroleum coke, residual oil) according to the method recommended by the instrument manufacturer and input it into the microprocessor.
      • 9.1.2.3 The correction factor is calculated according to formula (2):
        • Correction factor (F) = (Ss × Ws) / (100(Vs − Vb) × C)
        • Where: Ss— sulfur content of the standard test sample used, %(m/m); Ws— mass of the standard test sample used, mg; Vb— volume of potassium iodate standard solution used in the blank determination, mL; Vs— volume of potassium iodate standard solution used in determining the correction factor, mL; C— potassium iodate standard solution used in determining the correction factor, each milliliter of which is equivalent to the mass of sulfur, mg S/mL.
    • 9.1.3 Quality control: Determine an appropriate analytical quality control test sample several times each day, and when the measured value is within the allowable range of the quality control chart, proceed with the analysis of test samples.
• 14 Calculation
  • 14.1 Calculation for iodate detection system: The sulfur content in the test sample X[%(m/m)] is calculated according to formula (3):
    • X = 100(V − Vb) × F × C / W
    • Where: V— volume of potassium iodate standard solution used in the analytical determination, mL; Vb— volume of potassium iodate standard solution used in the blank determination, mL; F— correction factor; C— potassium iodate standard solution used for analysis, each milliliter of which is equivalent to the mass of sulfur, mg S/mL; W— mass of the test sample used for analysis, mg.
  • 14.2 Calculation for infrared detection system
    • 14.2.1 Report all results using the microprocessor.
    • 14.2.2 Report the average of two results.
• Appendix A (Informative appendix) Preparation of sulfur standard samples
  • A1 Instruments and materials: adsorption column (length 600mm, diameter 40mm, lower end diameter about 6mm); volumetric flask (100mL); neutral oil (sulfur content less than 0.05%(m/m)); silica gel (100 mesh～200 mesh); acidic aluminum oxide (100 mesh～200 mesh).
  • A2 Reagents: A2.1 n-hexadecane (analytical reagent); A2.2 dibutyl sulfide, dibenzyl sulfide, or dibenzyl disulfide (reference material, used as the primary sulfur compound).
  • A3 Preparation work: A3.1 Activate silica gel in an oven at 150℃ for 3h, then store in a desiccator for later use; A3.2 Activate acidic aluminum oxide in a muffle furnace at 450℃ for 4h～5h, then store in a desiccator for later use; A3.3 First plug the lower end of the adsorption column with clean degreased cotton, then while tapping, add activated silica gel and acidic aluminum oxide in a ratio of 1:1 to three quarters of the height of the adsorption column, and continue tapping the column until the silica gel and acidic aluminum oxide no longer settle. The column should be placed vertically, neutral oil is added, and a clean glass bottle is used to collect the desulfurized neutral oil that drips down.
  • A4 Preparation of sulfur standard sample: 100mL Weigh a certain amount of desulfurized neutral oil or n-hexadecane into a volumetric flask (weighed to the nearest 0.0001g), then weigh a certain amount of the primary sulfur compound (weighed to the nearest 0.0001g).
  • A5 Calculation: The sulfur content of the sulfur standard sample S[%(m/m)] is calculated according to formula (A1):
    • S = [(W₁ × S₁/100) / (W₁ + W₂)] × 100
    • Where: S₁—sulfur content of the reference sulfur compound, %(m/m); W₁—mass of the reference sulfur compound, g; W₂—mass of the desulfurized neutral oil or n-hexadecane, g.

10. Precision

• 16 Precision and bias
  • 16.1 Precision: Judge the reliability of the results according to the following provisions (95% confidence level).
    • 16.1.1 Petroleum products
      • 16.1.1.1 Repeatability (r): Under long-term normal and accurate operation, by the same operator using the same instrument, with the same test material, under certain operating conditions, the difference between two results obtained shall not be greater than the value in Table 3.
        • Table 3 Repeatability (r) %(m/m):
          • Sulfur content 0.0～0.5: Iodate detection system method 0.05, infrared detection system method 0.04
          • Sulfur content 0.5～1.0: Iodate detection system method 0.07, infrared detection system method 0.07
          • Sulfur content 1.0～2.0: Iodate detection system method 0.10, infrared detection system method 0.08 (the infrared-system precision value is garbled in the source transcription and remains unverified)
          • Sulfur content 2.0～3.0: Iodate detection system method 0.16, infrared detection system method 0.12
          • Sulfur content 3.0～4.0: Iodate detection system method 0.22, infrared detection system method 0.13
          • Sulfur content 4.0～5.0: Iodate detection system method 0.28 (the iodate-system precision value is garbled in the source transcription and remains unverified), infrared detection system method 0.16
      • 16.1.1.2 Reproducibility (R): Under long-term normal and accurate operation, in different laboratories, by different operators using the same test material, under the same operating conditions, the difference between two independent results obtained shall not be greater than the value in Table 4.
        • Table 4 Reproducibility (R) %(m/m):
          • Sulfur content 0.0～0.5: Iodate detection system method 0.08, infrared detection system method 0.13
          • Sulfur content 0.5～1.0: Iodate detection system method 0.11, infrared detection system method 0.21
          • Sulfur content 1.0～2.0: Iodate detection system method 0.17, infrared detection system method 0.27
          • Sulfur content 2.0～3.0: Iodate detection system method 0.26, infrared detection system method 0.38
          • Sulfur content 3.0～4.0: Iodate detection system method 0.40, infrared detection system method 0.44
          • Sulfur content 4.0～5.0: Iodate detection system method 0.54, infrared detection system method 0.49
    • 16.1.2 Petroleum coke
      • 16.1.2.1 Repeatability (r): Under long-term normal and accurate operation, by the same operator using the same instrument, with the same test material, under the same operating conditions, the difference between two results obtained shall not be greater than the value of formula (4): r = 0.05X₁, where X₁—arithmetic mean of the two repeat determination results.
      • 16.1.2.2 Reproducibility (R): Under long-term normal and accurate operation, in different laboratories, by different operators using the same test material, under the same operating conditions, the difference between two independent results obtained shall not be greater than the value of formula (5): R = 0.22X₂, where X₂—arithmetic mean of the two determination results submitted by different laboratories.
  • 16.2 Bias: The bias of this standard is being determined.

11. Report

• 15 Report: When the sulfur content is within the range of 0.05%(m/m)～5.00%(m/m), report the test result to the nearest 0.01%(m/m). When the sulfur content is within the range of 5%(m/m)～30%(m/m), report the test result to the nearest 0.1%(m/m).

12. Normative references

• GB/T 4756 Petroleum liquids—Manual sampling
• GB/T 6682 Water for analytical laboratory use—Specification and test methods
• GB/T 11131 Determination of total sulfur content in petroleum products (lamp method)

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick reference for questions and answers