⛽ Carbon residue (micro)
In short
Determination of carbon residue after evaporation and pyrolysis of petroleum products in nitrogen atmosphere at 500°C. The test is performed according to PN-EN ISO 10370:2014; Determination range: 0.10–30.0% m/m. The procedure comprises 10 steps (about 2 h 35 min–2 h 50 min in total); it is used for: Marine fuel quality assessment (ISO 8217 — CR limit by category), Diesel and heavy fuel oil control, Crude oil characterization — distillation yield prognosis.
At a glance
- Standard: PN-EN ISO 10370:2014
- Category: Petrochemistry
- Procedure steps: 10
- Total time of stages: 2 h 35 min–2 h 50 min
- Determination range: 0.10–30.0% m/m
- Pyrolysis temperature: 500°C ± 2°C
- Sample mass: 0.15–1 g (in glass vial)
Overview
Carbon Residue (CR) is a measure of the tendency of a petroleum product to form carbon deposits (coke) under high-temperature thermal degradation conditions. This parameter is crucial in quality assessment of heavy fuels, diesel oils, lubricating oils and crude oil, as it directly correlates with the content of asphaltenes, resins and polycyclic aromatic hydrocarbons.
The micro method according to ISO 10370 replaced the older, classical Conradson method (ISO 6615) and Ramsbottom method (ISO 4262). Advantages of the micro method are: lower sample consumption (approx. 0.15–1 g vs. 10 g), elimination of open flame, possibility of simultaneous testing of up to 12 samples, better repeatability and work safety (inert N₂ atmosphere).
High CR values indicate the presence of heavy fractions which, when burned in engines or boilers, form deposits, sediments and blockages. In marine fuel specifications (ISO 8217), CR is one of the limiting parameters. In crude oil, CR serves to evaluate the efficiency of vacuum distillation process and depth of conversion in cracking processes.
Micro method results in the range 0.10–25.0% m/m are equivalent to classical Conradson method results. For samples with expected residue below 0.10% m/m, the 10% (V/V) distillation residue prepared according to ISO 3405 is tested.
Method principle
A weighed sample portion (0.15–1 g) is placed in a glass test vial inside an aluminum heating block. The vial is heated in a controlled manner in nitrogen atmosphere (inert gas) to 500°C ± 2°C. During heating, evaporation of volatile fractions and pyrolysis of heavy components occurs. Nitrogen flowing through the system removes pyrolysis vapors and gases, preventing oxidation. After cooling, the carbon residue in the vial is weighed. The result is expressed as mass percent of residue relative to sample mass.
Applications
- Marine fuel quality assessment (ISO 8217 — CR limit by category)
- Diesel and heavy fuel oil control
- Crude oil characterization — distillation yield prognosis
- Base and lubricating oil testing — deposit formation tendency
- Refinery process control (cracking, delayed coking)
- Asphalt and petroleum bitumen quality assessment
Key parameters
| Parameter | Value |
|---|---|
| Determination range | 0.10–30.0% m/m |
| Pyrolysis temperature | 500°C ± 2°C |
| Sample mass | 0.15–1 g (in glass vial) |
| Inert gas | Nitrogen, purity ≥99.9% |
| Repeatability | 0.03 × average result (for CR >0.10%) |
| Determination time | 45–60 min (automatic cycle) |
Standard
- Standard number
- PN-EN ISO 10370:2014
- Title (PL)
- Przetwory naftowe — Oznaczanie pozostałości po koksowaniu — Metoda mikro
- Title (EN)
- Petroleum products — Determination of carbon residue — Micro method
Step-by-step procedure
-
Vial preparation
Wash glass vials with toluene and acetone. Dry in oven (110°C, 30 min). Cool in desiccator and weigh to 0.01 mg accuracy.
-
Sample weighing
Weigh 0.15–1 g of sample into vial to 0.01 mg accuracy. For samples with low CR use larger weight (closer to 1 g). For heavy oils — approx. 0.15 g.
-
Placement in apparatus
Insert vials into aluminum heating block sockets of apparatus (max. 12 positions simultaneously). Ensure vials are properly seated.
-
Nitrogen connection
Connect nitrogen line and set flow to value recommended by apparatus manufacturer (typically 150–600 mL/min). Check connection tightness.
-
Heating cycle programming
Set temperature program: heating ramp to 500°C at approx. 10°C/min, hold at 500°C for 15 min, cooling.
-
Test execution
Start automatic cycle. Apparatus heats samples in N₂ atmosphere, vapors are removed by gas stream. Cycle takes approx. 45–60 min.
-
Cooling
After cycle completion, wait for block to cool to room temperature. Do not open apparatus before reaching safe temperature.
-
Residue weighing
Remove vials, place in desiccator for 15 min, then weigh to 0.01 mg accuracy.
-
Result calculation
CR [% m/m] = [(vial mass with residue − empty vial mass) / sample mass] × 100.
-
Quality control
Compare duplicates with repeatability limits. Analyze CRM every series. Clean apparatus and dispose of used vials.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Micro carbon residue apparatus | PAC Alcor MCRT-160, Tanaka ACR-100M, Normalab NCR M10 | 80 000–180 000 PLN |
| Disposable glass vials | Borosilicate vials for MCRT, pack of 100 pcs. | 800–1 500 PLN / 100 pcs. |
| Analytical balance (d=0.01 mg) | Mettler Toledo XPR205, Sartorius Cubis II, Radwag XA 210.5Y | 15 000–40 000 PLN |
| Nitrogen cylinder + regulator | Technical nitrogen 5.0, 50 L cylinder, two-stage regulator | 300–800 PLN / cylinder + 1 500 PLN regulator |
| Desiccator with silica gel | Glass desiccator Ø 200 mm, Duran | 400–1 200 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Nitrogen gas (purity ≥99.9%) | 7727-37-9 | Inert gas for flow through apparatus, prevents sample oxidation |
| Toluene | 108-88-3 | Analytical grade, for washing equipment and vials |
| Acetone | 67-64-1 | Analytical grade, for cleaning and degreasing vials |
| Reference material (CRM) | — | Certified reference material for validation, e.g., reference oil NIST / Paragon Scientific |
Health and safety (OHS)
- Temperature 500°C — serious burn risk, do not touch heating block
- Nitrogen — asphyxiant gas, ensure room ventilation (risk of oxygen displacement)
- Petroleum samples — flammable, store away from heat and fire sources
- Toluene, acetone — flammable and irritating, work under fume hood
- Use heat-resistant gloves when removing vials
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 10370:2014 — “Petroleum products — Determination of carbon residue — Micro method”.
How does this method work?
A weighed sample portion (0.15–1 g) is placed in a glass test vial inside an aluminum heating block.
What is the measuring range and accuracy?
Determination range: 0.10–30.0% m/m; Pyrolysis temperature: 500°C ± 2°C; Sample mass: 0.15–1 g (in glass vial); Inert gas: Nitrogen, purity ≥99.9%.
How long does the test take?
The times given for the individual stages add up to approximately 2 h 35 min–2 h 50 min. The procedure comprises 10 steps.
What equipment is required?
Micro carbon residue apparatus, Disposable glass vials, Analytical balance (d=0.01 mg), Nitrogen cylinder + regulator, Desiccator with silica gel. Indicative cost of the core instrument (Micro carbon residue apparatus): 80 000–180 000 PLN.
Where is this test used?
Marine fuel quality assessment (ISO 8217 — CR limit by category); Diesel and heavy fuel oil control; Crude oil characterization — distillation yield prognosis; Base and lubricating oil testing — deposit formation tendency; Refinery process control (cracking, delayed coking); Asphalt and petroleum bitumen quality assessment.
What safety precautions apply?
Temperature 500°C — serious burn risk, do not touch heating block; Nitrogen — asphyxiant gas, ensure room ventilation (risk of oxygen displacement); Petroleum samples — flammable, store away from heat and fire sources; Toluene, acetone — flammable and irritating, work under fume hood; Use heat-resistant gloves when removing vials.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 10370.