SH/T 0705-2001 Standard test method for determination of vanadium in heavy oils by spectrophotometry

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Source limitations: The source has unresolved oxidation-state notation, standard-solution concentration, volume symbols and precision coefficients. These uncertainties are retained below and summarized in section 13. Check the original standard before using the values or calculation.

Card type: Test method

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

• Standard number: SH/T 0705-2001
• Chinese title, translated: Determination of vanadium content in heavy oils (spectrophotometric method)
• English name: Standard test method for determination of vanadium in heavy oils by spectrophotometry
• Replacement relationship: not found in the available source.
• Publication/implementation: published on 2001-11-23; implemented on 2002-01-01; issuing authority: State Economic and Trade Commission.
• Technical administration: Research Institute of Petroleum Processing, China Petroleum & Chemical Corporation.
• Drafting organization: Fushun Petroleum Institute; principal drafters: Li Ping and Zhao Shanlin.

2. Scope and exclusions

• 1.1 This standard specifies a method for determining vanadium content in heavy oils and crude oils.
• 1.2 The minimum detection limit for vanadium content is 0.06 mg/kg.
• 1.3 Precision data were obtained by statistical testing of samples with vanadium contents not greater than 5.00 mg/kg.
• Note: heavy oils in this standard include atmospheric residues, vacuum residues and wax-oil fractions.
• Exclusions: no explicit exclusion clause was found in the available source.

3. Principle

Prepare a sample solution containing V³⁺ and VO²⁺ by the treatment procedure. Pass a measured portion through a cation-exchange resin so that V³⁺, VO²⁺ and certain other cations are retained. Elute the column with acidified hydrogen peroxide to oxidize the species to V⁵⁺, which leaves the cation-exchange column as VO₃⁻. The source card lists the species being oxidized as V(Ⅳ), V(Ⅳ), with the extracted wording 'VII, V4+'; this unresolved oxidation-state wording requires verification against the original standard. Collect and treat the eluate, then react its V⁵⁺ with a mixed tannic acid–thioglycolic acid solution to form an indigo-blue complex. Measure at a wavelength of 600 nm.

4. Reagents and materials (purity / preparation)

Unless otherwise stated, all reagents are analytical grade and the water meets the grade-two requirements of GB/T 6682.

• 5.1 Acetic acid.
• 5.2 Ammonium acetate (the extracted Chinese reagent name is garbled).
• 5.3 Tannic acid (several extracted Chinese forms of the reagent name are garbled).
• 5.4 Thioglycolic acid.
• 5.5 Hydrochloric acid: relative density 1.19.
• 5.6 Sulfuric acid: relative density 1.84.
• 5.7 Aqueous ammonia: 25%～28%.
• 5.8 Hydrogen peroxide: 30%.
• 5.9 Ammonium metavanadate (the extracted Chinese reagent name is garbled).
• 5.10 Silver nitrate.
• 5.11 Congo red test paper.
• 5.12 Qualitative filter paper.
• 5.13 Polystyrene-based cation-exchange resin: grade 001×7 (GB/T 1631).

6.1 Preparation of solutions

• 6.1.1 Acetic acid–ammonium acetate buffer solution (pH=4): dissolve 25 g of ammonium acetate, weighed to 0.1 g, in a small amount of distilled water. Add 80 mL of acetic acid and dilute to 1 L with distilled water.
• 6.1.2 Tannic acid solution: dissolve 5 g of tannic acid, weighed to 0.1 g, in a small amount of distilled water, then dilute to 1 L with distilled water.
• 6.1.3 Thioglycolic acid (mercaptoacetic acid) solution: add 10 mL of thioglycolic acid solution to 90 mL of distilled water.
• 6.1.4 Mixed tannic acid–thioglycolic acid solution: mix equal volumes of the tannic acid and thioglycolic acid solutions. Filter through qualitative filter paper into an amber bottle for use. This solution is stated to be stable for three months.
• 6.1.5 Silver nitrate solution: 0.1 mol/L.
• 6.1.6 Hydrogen peroxide eluent: take 30 mL of hydrogen peroxide, add 4 mL of 1:1 (V/V) sulfuric acid solution, then dilute to 1 L with distilled water.
• 6.1.7 Vanadium standard solution: weigh 0.2297 g of ammonium metavanadate to 0.0001 g. Dissolve with gentle heating in a small amount of distilled water, transfer to a 1 L volumetric flask and dilute to the mark with distilled water. The concentration is 0.1 mg/mL. Transfer 10 mL of this solution to a 100 mL volumetric flask and dilute to the mark with distilled water, giving a concentration of 10 μg/mL. The extracted string 'IOW ML' is garbled; the concentration requires verification against the original standard.

6.2 Treatment of the cation-exchange resin

Sieve the cation-exchange resin to obtain the 60～80 mesh fraction. Place it in 20% (V/V) hydrochloric acid solution and soak for 1 h. Wash with distilled water until neutral and until a test with silver nitrate solution shows no chloride ions. Measure 40 mL of the activated hydrogen-form resin and pack it into the cation-exchange column for use.

6.3 Regeneration of the cation-exchange column

Soak the used cation-exchange column with 40 mL of 1:2 (V/V) hydrochloric acid solution for 1 h, then rinse with distilled water until neutral. Test with silver nitrate solution for absence of chloride ions. Shake the resin column to loosen the packing for the next use.

5. Apparatus

• 4.1 Spectrophotometer.
• 4.2 Electric heater with adjustable temperature: 1000 W.
• 4.3 High-temperature furnace: capable of maintaining 550℃±25℃.
• 4.4 Quartz beakers: 100 mL.
• 4.5 Volumetric flasks: 25 mL, 50 mL and 100 mL.
• 4.6 Pipettes: 1 mL, 2 mL, 5 mL and 10 mL.
• 4.7 Graduated cylinder: 50 mL.
• 4.8 Beaker: 100 mL.
• 4.9 Amber narrow-neck bottle: 500 mL.
• 4.10 Absorption cell: optical path length 3 cm.
• 4.11 Analytical balance: sensitivity 0.0001 g.
• 4.12 Sieves: 60～80 mesh.
• 4.13 Cation-exchange column (see Figure 1 in the source).

6. Recommended operating conditions

• Measurement wavelength: 600 nm.
• Absorption-cell optical path length: 3 cm.
• Colour-development standing time: 25 min.
• Flow rate through the cation-exchange column: 2 mL/min～3 mL/min.
• Ashing temperature: 550℃±25℃.
• Reference: blank solution.

7. Sampling and sample preparation

• 7.2 Sample treatment: weigh approximately 30 g of thoroughly mixed sample into a quartz beaker, to 0.1 g. Heat on an electric heater until white fumes appear, then ignite using filter paper and allow it to burn freely. When combustion is about to cease, continue carbonizing on the electric heater until it no longer ignites. Transfer to the high-temperature furnace, maintain 550℃±25℃ and ash until residual carbon is removed. Ashing time varies with the oil and generally requires 8 h～12 h or longer; absence of black carbon deposits is taken to indicate completion. Cool to room temperature. Using a pipette, add approximately 10 mL of 1:1 (V/V) hydrochloric acid solution down the beaker wall. Continue heating on the electric heater to dissolve the ash and concentrate to approximately 2 mL. Transfer to a 25 mL volumetric flask. Rinse the beaker three times with distilled water, add the rinsings to the flask, dilute to the mark and mix thoroughly. Keep as the sample solution.

8. Procedure

7.1 Preparation of the calibration curve

Into 6 separate 25 mL volumetric flasks, add respectively 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mL of the 10 μg/mL vanadium standard solution. Add a small piece of Congo red test paper and adjust with aqueous ammonia until the paper turns red. Then add, in sequence, 10 mL of acetic acid–ammonium acetate buffer solution and 2.5 mL of mixed tannic acid–thioglycolic acid solution. Dilute to the mark with distilled water and mix. After standing for 25 min, measure the absorbance of these standard solutions at 600 nm using a spectrophotometer with a 3 cm optical-path cell and the blank solution as reference. Plot vanadium concentration of the standard solutions on the horizontal axis and absorbance on the vertical axis.

7.3 Measurement of the sample solution

Pipette a measured volume of sample solution through the cation-exchange column at 2 mL/min～3 mL/min. When vanadium content does not exceed 1 mg/kg, pass the entire 25 mL sample solution through the column. Then pass 35 mL of water through the column to flush out all the sample solution and discard all this effluent. Next elute the column successively with 50 mL of hydrogen peroxide eluent and 25 mL of distilled water. Collect the eluate in a 100 mL beaker and add 1 mL of 1:1 (V/V) sulfuric acid solution. Concentrate on the electric heater until sulfur trioxide appears as white fumes. After cooling, transfer the solution to a 25 mL volumetric flask. Rinse the beaker three times with distilled water, using a total volume not exceeding 10 mL, and add the rinsings to the flask. Add a small piece of Congo red test paper and adjust with aqueous ammonia until the paper turns red. Add, in sequence, 10 mL of acetic acid–ammonium acetate buffer solution and 2.5 mL of mixed tannic acid–thioglycolic acid solution. Dilute to the mark with distilled water, mix and leave for 25 min. Measure absorbance at 600 nm on a spectrophotometer using a 3 cm optical-path cell and the blank solution as reference. Read the vanadium content of the sample solution from the calibration curve.

Notes

1. If the sample vanadium content exceeds 5.00 mg/kg, increase the sample dilution factor for the determination.
2. Iron (Fe³⁺), aluminium (Al³⁺) and cobalt (Co²⁺) ions do not interfere when their contents are no greater than 75, 50 and 50 times the vanadium content, respectively. Otherwise, a longer cation-exchange column may be used for treatment.

9. Determination and calculation

Calculate the sample vanadium content X (mg/kg) using equation (1):

X = (c × 25 × 25) / (m × V₁)

Where:

• c — diluted vanadium concentration read from the calibration curve, μg/mL;
• V₁ — volume of sample solution pipetted for the determination, mL;
• 25 — final diluted volume of the pipetted sample solution, mL; the source extraction has garbled characters before '25mL', requiring verification against the original standard;
• 25 — volume of the sample solution, mL; the source extraction reads 'V[unreadable sign]25mL', requiring verification against the original standard;
• m — mass of the sample, g.

Note: the extracted formula appears as 'cx [unreadable character]x V / M X V₁' and 'cx25x25 / M X V₁'. The source card uses c×25×25 as the numerator and m×V₁ as the denominator, but the formula remains subject to verification against the original standard.

10. Precision

Assess the reliability of test results using the following criteria (95% confidence level).

9.1 Repeatability (r)

The difference between two results obtained by the same operator, on the same instrument and for the same sample shall not exceed the value specified in Table 1.

Table 1 Repeatability (r)

Reproducibility (R)

The difference between two results obtained by different operators in different laboratories, using different instruments for the same sample, shall not exceed the value specified in Table 2.

Table 2 Reproducibility (R)

11. Report

Report the arithmetic mean of two repeat determinations as the sample vanadium content, to two decimal places.

12. References

• GB/T 1631 Classification, designation and model numbers of ion-exchange resins.
• GB/T 6682 Water for analytical laboratory use — Specification and test methods.

13. Source limitations and verification

• Source extraction uncertainties: the vanadium standard-solution concentration '10 μg/mL' in 6.1.7; volume symbols and values in the formula in section 9; precision coefficients in Tables 1 and 2; and the oxidation-state wording 'V(Ⅳ), V(Ⅳ)' in the Principle section 3. All require verification against the original standard.

14. Quick reference questions