SH/T 0058-1991 Determination of silicon, vanadium and iron contents in petroleum coke

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.

Card type: Test method

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

• Standard number: SH/T 0058-91 (in the original text at the main title it appears as "SH/T 0058-$1", suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction); the page header appears as "SH/T 0058-91")
• Chinese name: Determination of silicon, vanadium and iron contents in petroleum coke
• English name: not provided in the available source
• Replacement relationship: not provided in the available source
• Approval/implementation: approved by China Petrochemical Corporation 1991-06-28, implemented on 1992-07-01

2. Scope of application and non-applicability

• This standard specifies the determination method for silicon, vanadium and iron contents in petroleum coke.
• This standard applies to petroleum coke.
• Non-applicable scope: not provided in the available source.

3. Method principle

Place the sample in a high-temperature furnace at 850±20℃ for ashing; melt the ash with anhydrous sodium carbonate in a high-temperature furnace at 950±20℃; dissolve the melt with hot water, filter; silicate and vanadate remain in the aqueous solution, while iron salts remain in the precipitate. Dissolve the precipitate with sulfuric acid; perform colorimetric determination on the above two solutions separately by spectrophotometry; read the concentration of the sample solution from the working curve, and then calculate the silicon, vanadium and iron contents in the sample.

4. Reagents and materials (purity / preparation)

• 5.1 Sulfuric acid: analytical grade, prepare c(H₂SO₄)=0.5 mol/L and c(H₂SO₄)=4.5 mol/L aqueous solutions and 1:1 (volume ratio) sulfuric acid solution.
• 5.2 Anhydrous sodium carbonate: analytical grade, prepare 10 g/L aqueous solution.
• 5.3 Ammonium molybdate: analytical grade, prepare 100 g/L aqueous solution (filter, prepare fresh before use).
• 5.4 Ascorbic acid (vitamin C): analytical grade, prepare 10 g/L aqueous solution.
• 5.5 Silicon dioxide: reference reagent.
• 5.6 Hydrochloric acid: analytical grade, prepare c(HCl)=6 mol/L aqueous solution.
• 5.7 Sodium hydroxide: analytical grade, prepare 50 g/L aqueous solution.
• 5.8 Metaphosphoric acid: analytical grade, prepare 1:2 (mass ratio) aqueous solution, heat to dissolve.
• 5.9 Sodium tungstate: analytical grade, prepare 100 g/L aqueous solution (the original text says "calcium sodium salt"; according to the context of 6.2.2 and 7.3.2 it should be sodium tungstate, requires confirmation against the source standard (source-text extraction)).
• 5.10 Hydrogen peroxide: analytical grade, prepare 3% (m/m) aqueous solution.
• 5.11 Vanadium pentoxide: high-grade purity.
• 5.12 Nitric acid: analytical grade, prepare 1:3 (V/V) aqueous solution.
• 5.13 Ammonia water: analytical grade.
• 5.14 Ammonium sulfate: analytical grade.
• 5.15 Sulfosalicylic acid: analytical grade, prepare 200 g/L aqueous solution.
• 5.16 Reducing metallic iron: reference reagent.
• 5.17 Anhydrous sodium carbonate: analytical grade, grind it to 0.15 mm, dry in an oven at 110℃ for 4 h and set aside.
• 5.18 Phenolphthalein indicator: prepare 10 g/L ethanol solution.
• 5.19 Distilled water: meets grade three specifications in GB 6682.
• 4.2 Materials: quantitative filter paper, blue ribbon, medium speed.

5. Instruments and equipment

• a. Spectrophotometer, wavelength range 300~800 nm (the original text says "wavelength and open 300-802m", requires confirmation against the source standard (source-text extraction)).
• b. High-temperature furnace: maximum operating temperature 1000℃.
• c. Platform balance: sensitivity 0.2 g (the original text says "0.2B", requires confirmation against the source standard (source-text extraction)).
• d. Platinum crucible: volume 30 mL, diameter 32 mm.
• e. Platinum-tipped crucible tongs.
• f. Plastic beaker: 250 mL.
• g. Glass beaker: 250 mL.
• h. Volumetric flask: 100, 200, 250, 500, 1000 mL.
• i. Pipette: 1, 2, 3, 5, 10, 25, 50 mL.
• j. Boat-shaped porcelain dish: rectangular, top opening length 55–60 mm, width 25–30 mm, bottom length 45–50 mm, width 20–22 mm, height 14~16 mm.
• k. Two-hole water bath.
• l. Closed electric furnace.

6. Recommended operating conditions

• Ashing temperature: 850±20℃ high-temperature furnace.
• Melting temperature: 950±20℃ high-temperature furnace.
• Silicon measurement wavelength: 760 nm, optical path 3 cm cuvette, blank solution as reference solution.
• Vanadium measurement wavelength: 380 nm, optical path 3 cm cuvette, blank solution as reference solution.
• Iron measurement wavelength: 430 nm, optical path 3 cm cuvette, blank solution as reference solution.
• Color development standing time: for silicon, vanadium and iron, all are allowed to stand for 10 min before measuring absorbance.
• Vanadium measurement pH adjustment: pH=4~5.

7. Sampling and sample preparation

• 7.1.1 Prepare the sample according to SY 2871.
• 7.1.2 Weigh the prepared sample 5 g (weighed to 0.2 g), place in a boat-shaped porcelain dish, and calcine and ash in a high-temperature furnace at 850±20℃. When the vanadium content is less than 0.01% (m/m), the sample weight should be increased to 10 g.

8. Analysis procedure

8.1 Ashing and melting of the sample (7.1)

• 7.1.3 Take the boat-shaped porcelain dish out of the high-temperature furnace, cool, add 1.5 g anhydrous sodium carbonate, stir evenly with a glass rod or platinum rod, then transfer into a platinum crucible already filled with 0.6 g anhydrous sodium carbonate, place the sample as much as possible in the middle in a cone shape, then add anhydrous sodium carbonate 0.9 g to the boat-shaped porcelain dish, carefully stir with a glass rod or platinum rod and gently (the original text is interrupted here at source-text extraction, requires confirmation against the source standard (source-text extraction)) into the platinum crucible containing the sample, place a little more at the edge, then place the platinum crucible into a high-temperature furnace that has not been heated, then raise the temperature to 950±20℃, and maintain (the time is missing in the original text at source-text extraction, requires confirmation against the source standard (source-text extraction)) the eutectic mixture. Take out the platinum crucible in air (the original text is interrupted here at source-text extraction, requires confirmation against the source standard (source-text extraction)).

8.2 Separation of silicon, vanadium and iron in the melt (7.2)

• 7.2.1 Place the platinum crucible containing the melt into a 250 mL plastic beaker, add 70–80 mL hot distilled water, cover with a watch glass, and heat the plastic beaker on a water bath to dissolve the melt. At this time, silicate and vanadate dissolve in water, while iron salts form a precipitate. Remove the beaker, take out the platinum crucible with crucible tongs, wash the platinum crucible with hot distilled water, collect the wash water in the plastic beaker, filter while warm, and receive the filtrate in a 250 mL volumetric flask. Wash the beaker with a small amount of hot distilled water 2–3 times, pour the wash water onto the filter paper, wash the precipitate on the filter paper with hot sodium carbonate solution 6~8 times, rapidly cool the filtrate with tap water, dilute to the mark with distilled water, shake well, pour the solution into a clean plastic bottle; this is solution A, used for the determination of silicon and vanadium.
• 7.2.2 To the platinum crucible that still has a brown-red film after dissolution with hot distilled water, add 10 mL 1:1 sulfuric acid solution, place on a just-powered-off closed electric furnace and heat for 15–20 min using residual heat, then pour this sulfuric acid solution into a clean glass beaker, remove the filter paper with precipitate using tweezers, place it into the platinum crucible, and with the aid of a glass rod, scrub off the brown-red film, then also place this filter paper into the beaker already containing 10 mL sulfuric acid, add 10 mL 1:1 sulfuric acid solution to the platinum crucible again, shake gently, pour into the beaker, wash the platinum crucible with distilled water 2–3 times, and combine the wash water into the beaker with the filter paper. If the precipitate does not dissolve well, place the beaker on a water bath and heat until the brown-red color disappears (do not overheat, to prevent the filter paper from charring and the solution turning yellow). After cooling, filter the solution into a 250 mL volumetric flask, wash the filter paper with distilled water 2~3 times, add distilled water to the mark; this is solution B, used for the determination of iron.

8.3 Determination of silicon, vanadium and iron in solutions A and B (7.3)

• 7.3.1 Determination of silicon content: pipette an appropriate amount of solution A (the absorbance should be between 0.1–0.7) into a 100 mL volumetric flask, and measure its absorbance according to 6.1.3–6.1.4. Read the corresponding silicon content from the working curve.
• 7.3.2 Determination of vanadium content: pipette an appropriate amount of solution A into a 100 mL volumetric flask, add 2–3 drops of phenolphthalein indicator, neutralize with hydrochloric acid solution until the red color disappears, adjust pH=4–5, add 2 mL metaphosphoric acid solution, shake well. Then add 1 mL sodium tungstate solution, add distilled water to the mark, shake carefully, measure its absorbance according to 6.2.3, and read the corresponding vanadium content from the working curve.
  • Note: When the color-developing solution is turbid, silicic acid must first be separated before measuring absorbance. For this purpose, again pipette an appropriate amount of solution from solution A, place it in a 100 mL beaker, add 1–2 drops of phenolphthalein indicator, neutralize with hydrochloric acid solution, adjust to pH=4–5, filter with filter paper, filter the filtrate into a 100 mL volumetric flask, carefully wash the beaker and the precipitate on the filter paper with distilled water, combine the wash water into the same volumetric flask, then add hydrogen peroxide solution, and measure its absorbance according to 6.2.3. Find the corresponding vanadium content on the working curve.
• 7.3.3 Determination of iron content: Pipette an appropriate amount of solution B into a 100 mL volumetric flask, add 1 g ammonium sulfate, and 15 mL sulfosalicylic acid solution. Then add ammonia water until a stable yellow color appears, then add an excess of 1~2 mL, after cooling, add distilled water to the mark, shake the solution well; measure its absorbance according to 6.3.3. Find the corresponding iron content on the working curve.

8.4 Preparation of working curve (6)

• 6.1 Preparation of silicon working curve
  • 6.1.1 Weigh silicon dioxide 0.1 g (weighed to 0.0002 g) that has been calcined at 500℃ for 2 h, place in a platinum crucible, add 2 g anhydrous sodium carbonate, mix uniformly, then weigh 1 g anhydrous sodium carbonate to cover on top, place in a 950±20℃ high-temperature furnace to form a uniform melt.
  • 6.1.2 After removing the platinum crucible and cooling, place it in a 250 mL plastic beaker, add 70~80 mL hot distilled water, place in a water bath and heat until the melt is completely dissolved. Remove the platinum crucible from the plastic beaker, wash the platinum crucible with hot distilled water, and combine the wash water into the plastic beaker. Quantitatively transfer the solution in the plastic beaker to a 1000 mL volumetric flask, after cooling with tap water, dilute to the mark with distilled water, after shaking well, store in a plastic bottle. This standard solution contains 0.01 mg of silicon per milliliter.
  • 6.1.3 Using a pipette, respectively pipette 0, 1, 2, 3, 5, 7, 10 mL silicon standard solution into seven 100 mL volumetric flasks, wash the neck with a small amount of distilled water, add 2 drops of phenolphthalein indicator, neutralize with 0.5 mol/L sulfuric acid solution, then add 20 mL distilled water and 5 mL 0.5 mol/L sulfuric acid solution. Then slowly add 5 mL freshly prepared ammonium molybdate solution to each volumetric flask, carefully shake well, after 10 min, then add 25 mL 4.5 mol/L sulfuric acid solution and 10 mL ascorbic acid solution, dilute to the mark with distilled water, and shake well.
  • 6.1.4 After standing for 10 min, place in a cuvette with a light path of 3 cm, at 760 nm on a spectrophotometer, using a blank solution as reference, measure its absorbance. Plot the working curve with absorbance as the ordinate and the corresponding silicon content (mg/100mL) as the abscissa.
  • 6.1.5 When the instrument or reagents change, the working curve should be recalibrated.
• 6.2 Preparation of vanadium working curve
  • 6.2.1 Weigh vanadium pentoxide 0.1785 g (weighed to 0.0002 g) that has been calcined at 400~500℃ for 2 h into a beaker, add 10 mL sodium hydroxide solution, heat to dissolve, after cooling, add 2 drops of phenolphthalein indicator, neutralize with hydrochloric acid solution until slightly yellow, then add a slight excess, quantitatively transfer the solution to a 500 mL volumetric flask, dilute to the mark with distilled water, carefully shake well. Then use a pipette to draw 50 mL of the above solution and transfer to a 200 mL volumetric flask, add distilled water to the mark, and shake well. This standard solution contains 0.05 mg of vanadium per milliliter.
  • 6.2.2 Using a pipette, respectively pipette 0, 1, 2, 3, 5, 7, 10 mL vanadium standard solution into seven 100 mL volumetric flasks, add 40~45 mL distilled water, then add 2 mL metaphosphoric acid solution to each volumetric flask, shake well, then add 1 mL sodium tungstate solution, shake well again, and add distilled water to the mark.
  • 6.2.3 After standing for 10 min, place in a cuvette with a light path of 3 cm, at 380 nm on a spectrophotometer, using a blank solution as reference, measure its absorbance. Plot the working curve with absorbance as the ordinate and the corresponding vanadium content (mg/100mL) as the abscissa.
• 6.3 Preparation of iron working curve
  • 6.3.1 Weigh 0.0500 g (weighed to 0.0002 g) of metallic iron (reference reagent) into a 250 mL beaker, add 25 mL nitric acid solution, dissolve, boil to remove nitrogen oxides, after cooling, quantitatively transfer to a 500 mL volumetric flask. Add distilled water to dilute to the mark, and shake well. This standard solution contains 0.1 mg of iron per milliliter.
  • 6.3.2 Using a pipette, respectively pipette 0, 1, 2, 3, 5, 7, 10 mL iron standard solution into seven 100 mL volumetric flasks, add 20–25 mL distilled water, then add 1 g ammonium sulfate, 15 mL sulfosalicylic acid solution to each volumetric flask, then add ammonia water until a stable yellow color appears, then add an excess of 1–2 mL, after cooling, add distilled water to the mark, and carefully shake well.
  • 6.3.3 After standing for 10 min, place in a cuvette with a light path of 3 cm, at 430 nm on a spectrophotometer, using a blank solution as reference, measure its absorbance. Plot the working curve with absorbance as the ordinate and the corresponding iron content (mg/100mL) as the abscissa.

9. Qualitative and quantitative and calculation formula

The contents of silicon, vanadium, and iron in the sample X [% (m/m)] are calculated according to the following formula:

X = (K × V₁ × 100) / (m × V₂ × 10³)

Where:

• K—— the content of the element being measured found from the standard working curve, mg (original text has “mL”, requires confirmation against the source standard (source-text extraction));
• V₁——the volume of solution A or solution B, mL;
• V₂——the volume taken from solution A or solution B for colorimetric analysis, mL;
• m—— the mass of the sample, g.

(The original formula layout source-text extraction is garbled, the arrangement of symbols and denominator requires confirmation against the source standard (source-text extraction))

10. Precision

The difference between two results of repeated determinations shall not exceed the values listed in the table below (the repeatability sentence is unclear in the source transcription; verify its meaning against the original standard).

Precision table (unit: % (m/m))

(The original table source-text extraction is garbled, the correspondence between content range and repeatability values requires confirmation against the source standard (source-text extraction); the “0.0211” in the table is suspected to be a misrecognition of “0.006”, requires confirmation against the source standard (source-text extraction))

11. Report

Take the arithmetic mean of two results of repeated determinations as the result of the sample.

12. Reference documents

• GB 6682 Laboratory water specifications
• SY 2871 Petroleum coke inspection 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