NB/SH/T 0425-2023 Determination of wax content in petroleum asphalt

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Card type: Test method

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

• Standard number: NB/SH/T 0425—2023
• Chinese name: Determination of wax content in petroleum asphalt
• English name: Test Method for Wax Content in Asphalt
• Replacement relationship: replaces SH/T 0425—2003 "Determination of wax content in petroleum asphalt"
• Previous versions: first published in 1992 as SH/T 0425—1992, first revision in 2003, this is the second revision
• Publication/implementation: published on 2023-02-06, implemented on 2023-08-06
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants, Subcommittee on Petroleum Asphalt (SAC/TC280/SC4)
• Proposed by: China Petrochemical Corporation

2. Scope of application and non-applicability

• This document specifies the determination of wax content in petroleum asphalt by the pyrolysis distillation method (see Chapter 1).
• Applicable to petroleum asphalt produced from crude oil; for modified asphalt and asphalt produced from other raw materials, it may be used for reference (see Chapter 1).
• Non-applicable scope: not provided in the available source.

3. Method principle

The distillate oil obtained by pyrolysis of the sample is dissolved and diluted with anhydrous diethyl ether-anhydrous ethanol (or trichloroethylene-anhydrous ethanol) mixed solvent, cooled, crystallized, filtered, and washed at -20℃ temperature; the wax obtained by crystallization is dissolved with petroleum ether, the solvent is evaporated from the solution, vacuum dried, weighed, and calculation and data processing are performed to obtain the wax content (see Chapter 3).

• Note: The analyst may choose to use either the anhydrous diethyl ether-anhydrous ethanol or trichloroethylene-anhydrous ethanol solvent system according to actual conditions. For arbitration testing, the anhydrous diethyl ether-anhydrous ethanol solvent system is used (see Chapter 3).

4. Reagents and materials (purity / preparation)

• 4.1.1 Anhydrous diethyl ether (or trichloroethylene), chemically pure.
• 4.1.2 Anhydrous ethanol, chemically pure.
• 4.1.3 Petroleum ether, 60℃～90℃, chemically pure.
• 4.1.4 Industrial ethanol.
• Preparation of washing liquid (see 5.7): 30mL anhydrous diethyl ether-anhydrous ethanol 1:1 (or 30mL trichloroethylene-anhydrous ethanol 1:2) mixed liquid.
• Other preparation details: not provided in the available source.

5. Instruments and equipment

• 4.2.1 Automatic refrigeration device: the cold bath can accommodate more than three sets of freeze-filtration components consisting of a suction flask, glass filter funnel, sample cooling cylinder, and plunger stopper, or the freeze-filtration components are assembled into a freeze-filtration device as specified in 4.2.3; the cold bath temperature can be reduced to -22℃ and can be controlled at ±0.1℃.
• 4.2.2 Glass pyrolysis distillation flask: shape as shown in Figure 1, the side tube of the flask serves as the condenser.
• 4.2.3 Wax freeze-filtration device: composed of a suction flask, sintered glass funnel, plunger stopper, and sample cooling cylinder, etc., installation general drawing as shown in Figure 2; the pore size of the filter plate in the glass filter funnel is 10μm～16μm.
• 4.2.4 Conical flask: 100mL, 150mL.
• 4.2.5 Vacuum pump: pumping speed ≥1L/s.
• 4.2.6 Hot water bath or electric heating mantle (plate).
• 4.2.7 Desiccator.
• 4.2.8 Gas burner or flowerpot-type electric furnace: the heating surface of the flowerpot-type electric furnace should be able to wrap the spherical part of the pyrolysis flask to a height of at least 2/3, and the height and heating rate are adjustable, can display and set temperature, minimum heating temperature ≥600℃.
• 4.2.9 Vacuum drying oven: meets controlled temperature 100℃～110℃, residual pressure 21kPa～23kPa.
• 4.2.10 Stopwatch.
• 4.2.11 Thermometer.

6. Recommended operating conditions

• Pyrolysis distillation heating: heat the sample in the distillation flask with a gas burner flame or flowerpot-type electric furnace; for arbitration testing, use flame heating; during heating, the flame or electric furnace heating surface should wrap around the flask (see 5.1).
• Initial distillation time: from the start of heating, initial distillation is reached within 5min～8min (the first 1 drops flow down from the side tube head) (see 5.2).
• Distillation rate: continuously distill at a rate of 2 drops per second (4mL/min～5mL/min) until distillation ends, continuously observe for no distillate within 10s, and distillation should be completed from the start of heating to the end within 25min (see 5.2).
• Cold bath temperature: -20℃±0.5℃ (see 5.4).
• Cooling crystallization time: 1h (see 5.7).
• Natural filtration time: 30min (see 5.8).
• Suction filtration rate: the filtration rate of the filtrate is about 1 drops per second (see 5.9).
• Suction drying time: when the cold washing agent is no longer visible on the wax layer, continue suction filtration for 5min (see 5.9).
• Petroleum ether dissolution temperature: heat to 30℃～40℃ (see 5.10).
• Vacuum drying: temperature 105℃±5℃, residual pressure 21kPa～35kPa, dry for 1h (see 5.11).
• Desiccator cooling: 1h (see 5.11).

7. Sampling and sample preparation

• Sampling refers to GB/T 11147 Asphalt sampling method (see Chapter 2).
• Place about 50g of sample into the pyrolysis distillation flask, weighed to the nearest 0.1g (see 5.1).
• The distillate oil is weighed to the nearest 0.05g (see 5.2).
• From the mixed oil, weigh appropriate amounts of sample in 3 portions, respectively add to 100mL conical flasks of known mass, accurate to 1mg; the weighed amount of the 3 portions of sample should be such that the wax amount obtained after cooling and filtration is between 50mg～100mg, and they cannot all be greater than or all be less than 75mg; the sampling amount of each portion of distillate oil shall not exceed 10g (see 5.3).

8. Analysis steps

• 5.1 Place about 50g of sample into the pyrolysis distillation flask, weighed to the nearest 0.1g. Cover the distillation flask tightly with a cork stopper. Use a 150mL conical flask of known mass as the receiver, immersed in a beaker containing an ice-water mixture. Cut a small groove on the side of the cork stopper of the receiver to allow non-condensable gas to escape. Heat the sample in the distillation flask with a gas burner flame or flowerpot-type electric furnace, but for arbitration testing, use flame heating. During heating, the flame or electric furnace heating surface should wrap around the flask.
• 5.2 Adjust the flame intensity or the heating intensity of the electric furnace so that initial distillation is reached within 5min～8min from the start of heating (the first 1 drops flow down from the side tube head). Continuously distill at a rate of 2 drops per second (4mL/min～5mL/min) until distillation ends, continuously observe for no distillate within 10s, and distillation should be completed from the start of heating to the end within 25min. After distillation ends, the distillate oil remaining in the side tube should not flow into the receiver; the distillate oil is weighed to the nearest 0.05g.
• 5.3 To avoid evaporation loss, heat the distillate oil to slightly warm and carefully shake the receiving flask until the distillate oil is fully melted and uniformly mixed. From this mixed oil, weigh appropriate amounts of sample in 3 portions, respectively add to 100mL conical flasks of known mass, accurate to 1mg; the weighed amount of the 3 portions of sample should be such that the wax amount obtained after cooling and filtration is between 50mg～100mg, and they cannot all be greater than or all be less than 75mg. However, the sampling amount of each portion of distillate oil shall not exceed 10g.
• 5.4 Prepare an automatic refrigeration device that meets the temperature control accuracy, or the freeze-filtration device shown in Figure 2, but for arbitration testing, use the automatic refrigeration device. Set the refrigeration temperature so that the cold bath temperature is maintained at -20℃±0.5℃, or add industrial ethanol to the freeze-filtration device shown in Figure 2, cool with dry ice, maintain the temperature at -20℃±0.5℃, and immerse the thermometer to a depth of 150mm. The amount of liquid refrigerant in the cold bath should be such that when the freeze-filtration assembly is immersed in the cold bath, its liquid level is about 100mm or more higher than the solvent liquid level in the sample cooling cylinder.
• 5.5 Assemble the suction flask, glass filter funnel, sample cooling cylinder, and plunger stopper into the freeze-filtration assembly as shown in Figure 2.
• 5.6 To the 100mL conical flask containing the distillate oil, add 10mL anhydrous diethyl ether (or trichloroethylene), after sufficient dissolution transfer to the sample cooling cylinder. Rinse the conical flask twice with 15mL anhydrous diethyl ether (or 10mL trichloroethylene) and pour into the sample cooling cylinder. Then add 25mL anhydrous ethanol (or 40mL anhydrous ethanol) to the sample cooling cylinder and shake well to mix.
• 5.7 Place the freeze-filtration assembly into the pre-cooled cold bath, cool for 1h to allow the wax to crystallize sufficiently. In a test tube with a ground stopper, place 30mL anhydrous diethyl ether-anhydrous ethanol 1:1 (or 30mL trichloroethylene-anhydrous ethanol 1:2) mixed liquid as the washing liquid for the wax after filtration, and place in the cold bath to cool to -20℃±0.5℃.
• 5.8 Remove the plunger stopper and filter the precipitated wax. Suspend the plunger stopper in the sample cooling cylinder by an appropriate method. Maintain natural filtration for 30min.
• 5.9 Start the suction filtration device, maintain the filtration rate of the filtrate at about 1 drops per second. When the filtrate on the wax layer is about to be exhausted, add at once 30mL of the anhydrous diethyl ether-anhydrous ethanol 1:1 (or trichloroethylene-anhydrous ethanol 1:2) mixed solvent pre-cooled to -20℃±0.5℃, wash the wax layer, plunger stopper, and inner wall of the sample cooling cylinder, continue filtration, then use a vacuum pump for suction filtration; when the cold washing agent is no longer visible on the wax layer, continue suction filtration for 5min to dry the solvent in the wax.
• 5.10 Remove the freeze-filtration assembly from the cold bath, take off the suction flask, and attach it to a wax recovery flask of known mass; after reaching room temperature, use 100mL of petroleum ether heated to 30℃～40℃ to dissolve the wax on the glass filter funnel, sample cooling cylinder, and plunger stopper.
• 5.11 Place the wax recovery flask on a suitable heat source for distillation, remove the petroleum ether, then place in a vacuum drying oven to dry for 1h. The temperature in the vacuum drying oven is 105℃±5℃, and the residual pressure is 21kPa～35kPa. Then place the wax recovery flask in a desiccator to cool for 1h, weighed to the nearest 0.1mg.
• Note (after 5.11): The type, ratio, and quantity of the trichloroethylene-anhydrous ethanol solvent system in parentheses in test steps 5.6, 5.7, 5.9 are determined for use after verification of consistency of test results of representative samples under this solvent system with the anhydrous diethyl ether-anhydrous ethanol solvent system during standard revision, and after verification of repeatability and reproducibility of test results under the trichloroethylene-anhydrous ethanol solvent system. The analyst may choose the solvent system according to actual conditions. In case of dispute over results, the anhydrous diethyl ether-anhydrous ethanol solvent system should be used.

9. Qualitative and quantitative and calculation formulas

• Perform the cracking distillation operation once according to clauses 5.1 and 5.2, and perform the dewaxing operation three times according to clauses 5.4 to 5.11.
• The wax content in asphalt X (%) is calculated according to the following formula: X = 100%×(D×P)/(S×d)
• Where:
  • S — sample sampling amount, g;
  • D — distillate oil amount, g;
  • d — sample taken from the distillate oil, g;
  • P — mass of wax obtained, g.

10. Precision

When the difference between each other does not exceed the value in Table 1, it is considered correct.

Table 1

11. Report

Take the obtained wax mass (P) as the abscissa x, and the wax mass fraction (X) as the ordinate y, perform linear fitting to obtain the relationship line, and use interpolation to find the wax mass fraction when the wax mass is 0.075g as the reported wax content, accurate to the 1th decimal place.

• Note: The direction coefficient of the relationship line is only taken as positive; when there are two lines, take the interpolated value.

12. Normative References

• GB/T 514 Technical conditions for glass liquid thermometers for petroleum product testing
• GB/T 11147 Asphalt sampling method
• Note: The citation principle is—for dated references, only the version corresponding to that date applies; for undated references, the latest version (including all amendments) applies (see Chapter 2).

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 Q&A Reference