GB/T 6536-2010 Standard test method for distillation characteristics of petroleum products at atmospheric pressure

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

This standard specifies a method for the quantitative determination of the distillation characteristics of petroleum products at atmospheric pressure using laboratory batch distillation apparatus, including methods for manual and automatic apparatus (clause 1).

Evidence note: this page is a partial study compilation of the 2010 original of the same edition; the listed groups, preparation temperatures, cross-page condensation rates and equation subscripts have been checked against the source images, and technical review is pending. Method precision is not the uncertainty of a batch certificate, and the sample handling temperature of the method is not a storage condition for a product. Verification note: [to be verified] and [source unclear] mark places where the original text of the standard still has to be checked and do not mean that verification has been completed. Do not use these values or steps directly as a basis for work.

Scope: This standard specifies a method for the quantitative determination of the distillation characteristics of petroleum products at atmospheric pressure using laboratory batch distillation apparatus, including methods for manual and automatic apparatus (clause 1). It applies to distillate fuels such as natural gasoline (stabilized light hydrocarbon), light and middle distillates, automotive spark-ignition engine fuels, aviation gasoline, jet fuel, diesel and kerosene, and to naphtha and petroleum solvent products (clause 1). It does not apply to products containing appreciable residue (clause 1). NOTE: the samples used to establish the precision of this method all had a residue volume fraction of not more than 2% (note to clause 1).

Principle: On the basis of properties such as composition, vapour pressure, expected initial boiling point and expected final boiling point, the sample is classified into one of five specified groups. A 100 mL sample is distilled under the conditions specified for its group, at ambient atmospheric pressure and with the apparatus designed to provide about one theoretical distillation plate, using laboratory batch distillation apparatus. According to the requirements for the test result, temperature readings and the volumes of condensate, distillation residue and loss are observed and recorded systematically; the observed temperature readings are corrected for atmospheric pressure, and the results are tabulated or plotted as evaporation percentages or recovery percentages against the corresponding temperatures (clause 4).

Apparatus: Basic elements: distillation flask, condenser and associated cooling bath, metal shield or screen for the distillation flask, heater, flask support and support plate, temperature measuring device, and graduated cylinder to collect the distillate (5.1.1). Manual distillation apparatus is shown in Figure 1 (gas-heated type) and Figure 2 (electrically heated type) (5.1.2). Automatic distillation apparatus, in addition to the basic elements, is equipped with a system that measures and automatically records the temperature and the corresponding recovered volume in the graduated cylinder (5.1.3). Temperature measuring device (5.3): Glass mercury thermometer: shall comply with the specifications for thermometers GB-46 and GB-47 in GB/T 514; GB-46 covers 2 °C to 300 °C with a graduation of 1 °C, and GB-47 covers 2 °C to 400 °C with a graduation of 1 °C (5.3.1). After continuous exposure to temperatures above 370 °C for a considerable time, the thermometer shall be given a zero-point check or verification in accordance with GB/T 514 and JJG 50 (5.3.1). Other temperature measuring systems: may be used for this method provided that they are shown to have the same temperature lag, emergent-stem effect and accuracy as the glass mercury thermometer (5.3.2); the circuit and/or algorithm shall be capable of simulating the temperature lag of a glass mercury thermometer (5.3.2.1); the temperature sensor may also be placed in a sleeve (5.3.2.2). Glass mercury thermometers shall be used for referee tests (5.3.3). Temperature sensor centring device (5.4): shall fit into the neck of the distillation flask by means of a close-fitting device without causing vapour leakage; an acceptable centring device is shown in Figure 3. WARNING: the use of an ordinary stopper with a central hole does not comply with the specification. Safety device (5.5): automatic apparatus is recommended to be fitted with a device that switches off the power automatically and, in the event of fire, sprays inert gas or steam into the chamber containing the distillation flask. Barometer (5.6): capable of measuring the atmospheric pressure at the local observation point at the same altitude as the laboratory in which the apparatus is located, with an accuracy of 0.1 kPa or better. WARNING: the pressure reading of an ordinary aneroid barometer must not be used. Detailed apparatus specification in Annex A (normative): Distillation flask: made of heat-resistant glass, dimensions and tolerances as in Figure A.1; distillation flask A (100 mL) and distillation flask B (125 mL) (A.1). Condenser and cooling bath: the condenser is made of seamless corrosion-resistant metal tube, 560 mm ± 5 mm long, 14 mm outside diameter, 0.8 mm to 0.9 mm wall thickness (A.2.2); a 393 mm ± 3 mm length of the condenser tube is in contact with the cooling medium, with 50 mm ± 3 mm exposed at the upper end and 114 mm ± 3 mm at the lower end (A.2.3); the lower structure of the condenser tube is shown in Figure A.2. Metal shield or screen (manual apparatus only): the gas heater shield is usually 480 mm high, 280 mm long and 200 mm wide, of 0.8 mm sheet metal (A.3.1); the electric heater shield is usually 440 mm high, 200 mm long and 200 mm wide, of 0.8 mm sheet metal (A.3.2). Heater: gas heater (A.4.1); electric heater of low thermal lag, adjustable from 0 W to 1000 W, is suitable (A.4.2). Flask support: the first type is for the gas heater (A.5.1); the second type is for the electric heater (A.5.2). Flask support plate: made of ceramic or other heat-resistant material 3 mm to 6 mm thick, divided into types A, B and C according to the central hole size, dimensions in Table 3; WARNING: materials containing asbestos must not be used for the flask support plate (A.6.1). Receiver graduated cylinder: capable of measuring and collecting 100 mL of sample (A.7.1); for the manual method the cylinder is graduated at 1 mL intervals with a mark at 100 mL (A.7.1.1); for the automatic method the dimensions and structure of the cylinder shall comply with Figure A.3 (A.7.1.2); capacity 100 mL, graduation 1 mL, capacity tolerance ±1.0 mL (note to Figure A.3). Residue graduated cylinder: 5 mL graduated cylinder, graduation 0.1 mL, graduations starting at 0.1 mL (A.8).

Reagents and reference materials: Check liquids: analytical-grade toluene and hexadecane (8.1.2.2); reagents of other grades may also be used provided they are shown not to reduce the accuracy of the determination (note to 8.1.2.2). Drying agent: anhydrous sodium sulphate (6.5.2, 6.5.3); or another suitable drying agent (6.5.3). Boiling chips: a small amount of boiling chips may be added if irregular boiling (bumping) is expected; a small amount may be added at any stage of the distillation (9.4). Cooling bath medium: crushed ice and water, chilled brine, chilled ethylene glycol, etc. (groups 0, 1, 2 and 3, 7.2.1); cold water, hot water or heated ethylene glycol, etc. (group 4, 7.2.2). Other reagent purities and preparations: not given in the material available.

Key conditions: Group characteristics are given in Table 1 (6.1): the distillation type of group 0 is natural gasoline, and the cells for its vapour pressure, initial boiling point and final boiling point are not given in the original table, so no zero is entered and no limit from group 1 is borrowed. Group 1: vapour pressure (37.8 °C) ≥ 65.5 kPa, final boiling point ≤ 250 °C, initial boiling point cell not given in the original; group 2: vapour pressure < 65.5 kPa, final boiling point ≤ 250 °C, initial boiling point cell not given in the original; group 3: vapour pressure < 65.5 kPa, initial boiling point ≤ 100 °C, final boiling point > 250 °C; group 4: vapour pressure < 65.5 kPa, initial boiling point > 100 °C, final boiling point > 250 °C. A blank cell in the original does not mean a value of zero, nor does it guarantee a general product classification. | Group | Distillation type | Vapour pressure at 37.8 °C | Initial boiling point | Final boiling point | | --- | --- | --- | --- | --- | | 0 | Natural gasoline | not given in the original table | not given in the original table | not given in the original table | | 1 | — | ≥65.5 kPa | not given in the original table | ≤250 °C | | 2 | — | <65.5 kPa | not given in the original table | ≤250 °C | | 3 | — | <65.5 kPa | ≤100 °C | >250 °C | | 4 | — | <65.5 kPa | >100 °C | >250 °C | Apparatus preparation is given in Table 3 (7.1): | Group | Distillation flask | Thermometer | Thermometer range | Support plate hole | Flask temperature at start | Support plate and shield | Receiver and 100 mL sample | | --- | --- | --- | --- | --- | --- | --- | --- | | 0 | 100 mL | GB-46 | low | A (32 mm) | 0-5 °C | not above ambient temperature | 0-5 °C | | 1 | 125 mL | GB-46 | low | B (38 mm) | 13-18 °C | not above ambient temperature | 13-18 °C | | 2 | 125 mL | GB-46 | low | B (38 mm) | 13-18 °C | not above ambient temperature | 13-18 °C | | 3 | 125 mL | GB-46 | low | C (50 mm) | 13-18 °C | not above ambient temperature | 13-18 °C | | 4 | 125 mL | GB-47 | high | C (50 mm) | not above ambient temperature | dash in the original, no value supplied | 13 °C to ambient temperature | The last two groups follow the special case of 9.3.2 according to footnote a of the original; non-liquid samples cannot be forced into the temperature ranges of this table. Test conditions are given in Table 5 (9.9): | Group | Condensation bath temperature / °C | Receiver cooling bath temperature / °C | Start of heating to initial boiling point / min | Initial boiling point to 5% recovered / s | Initial boiling point to 10% recovered / min | Mean condensation rate, 5% recovered to 5 mL residue / (mL/min) | Mean condensation rate, 10% recovered to 5 mL residue / (mL/min) | 5 mL residue to final boiling point / min | | --- | --- | --- | --- | --- | --- | --- | --- | --- | | 0 | 0-1 | 0-4 | 2-5 | dash in the original, no value supplied | 3-4 | dash in the original; the rate from 10% below applies | 4-5 | ≤5 | | 1 | 0-1 | 13-18 | 5-10 | 60-100 | not given in the material available | 4-5 | not given in the material available | ≤5 | | 2 | 0-5 (a) | 13-18 | 5-10 | 60-100 | not given in the material available | 4-5 | not given in the material available | ≤5 | | 3 | 0-5 | 13-18 | 5-10 | dash in the original, no value supplied | not given in the material available | 4-5 | not given in the material available | ≤5 | | 4 | 0-60 | sample temperature ±3 | 5-15 | dash in the original, no value supplied | not given in the material available | 4-5 | not given in the material available | ≤5 | a: the suitable condensation bath temperature depends on the distilled fraction of the sample and on its wax content; in general a single condensation temperature is used. A bath temperature of 0 °C to 4 °C is usually suitable for kerosene and light middle distillate fuels; in some cases middle distillate fuels, heavy distillates and similar fractions may require the condensation bath to be kept at 38 °C to 60 °C. Correction of temperature readings: correct the temperature readings to the standard atmospheric pressure of 101.3 kPa by the Sydney Young equation, equation (2), or use Table 6 (10.3). Table 6 lists correction values (0.35 to 0.81 °C) for each 1.3 kPa pressure difference over the temperature range 10-30 °C to >390-410 °C. The correction is added when the atmospheric pressure is below 101.3 kPa and subtracted when it is above 101.3 kPa (footnote a to Table 6). The corrected loss is calculated by equation (3) or read from Table E.1 of Annex E (10.4). The corrected recovery percentage is calculated by equation (4) (10.4).

Calculation and results: Total recovery percentage = maximum recovery percentage (see 9.18) + residue percentage (see 9.19); the loss percentage is obtained by subtracting the total recovery percentage from 100% (10.1). No meniscus correction for atmospheric pressure is applied, and the atmospheric pressure is not adjusted to a sea-level reading (10.2). The temperature reading is corrected to the standard atmospheric pressure of 101.3 kPa by the Sydney Young equation, equation (2): C_c = 0.0009(101.3 − Pk)(273 + te) where: C_c is the correction to be added (algebraically) to the observed temperature reading, in degrees Celsius (°C); Pk is the atmospheric pressure at the time and place of the test, in kilopascals (kPa); te is the observed temperature reading, in degrees Celsius (°C). The correction obtained is applied to the observed temperature reading and, depending on the apparatus used, the result is rounded to 0.5 °C or 0.1 °C; the corrected temperature reading after atmospheric pressure correction shall be used in all subsequent calculations and in the report (10.3). The corrected loss L_c is calculated by equation (3), or may be read from Table E.1 of Annex E: L_c = 0.5 + (L − 0.5)/[1 + (101.3 − Pk)/8.0] where: L_c is the corrected loss, %; L is the observed loss, %; Pk is the atmospheric pressure at the time and place of the test, in kilopascals (kPa) (10.4). The corrected recovery percentage is calculated by equation (4): R_c = Rmax + (L − L_c) where: R_c is the corrected recovery percentage, %; Rmax is the maximum recovery percentage, %; L is the observed loss, %; L_c is the corrected loss, % (10.4). To obtain the evaporation percentage corresponding to a specified temperature reading, the loss percentage is added to each observed recovery percentage obtained at the specified temperature, by equation (5): P_e = P_r + L where: P_e is the evaporation percentage, %; P_r is the recovery percentage, %; L is the observed loss, % (10.5). To obtain the temperature reading corresponding to a specified evaporation percentage, if no temperature data were recorded within 0.1% by volume at that specified evaporation percentage, a calculation or graphical method may be used, and this shall be noted in the report of results (10.6). Calculation method: first subtract the observed loss from each specified evaporation percentage to obtain the corresponding recovery percentage, then calculate the required temperature reading by equation (6): T = T_L + (T_H − T_L) × (R − R_L)/(R_H − R_L) where: T is the temperature reading at the specified evaporation percentage, in degrees Celsius (°C); T_L is the thermometer reading recorded at R_L, in degrees Celsius (°C); T_H is the thermometer reading recorded at R_H, in degrees Celsius (°C); R is the recovery percentage corresponding to the specified evaporation percentage, %; R_H is the recovery percentage adjacent to and above R, %; R_L is the recovery percentage adjacent to and below R, %. Values obtained by the calculation method are affected by the non-linearity of the distillation curve; the interval between consecutive data points at any stage of the test must not be greater than the data interval specified in 9.14; extrapolation shall not be carried out under any circumstances (10.6.1). Graphical method: using paper with uniform fine rulings, plot each temperature reading corrected for atmospheric pressure against its corresponding recovery percentage; plot the initial boiling point at 0% recovery; draw a smooth curve through the points; for each specified evaporation percentage subtract the loss percentage to obtain its corresponding recovery percentage, and read from the curve the temperature reading corresponding to that recovery percentage (10.6.2). For most automatic apparatus, temperature-volume data are collected at intervals of 0.1% by volume or less and stored in memory; to report the temperature reading at a specified evaporation percentage the steps of 10.6.1 and 10.6.2 need not be used, and the corresponding temperature closest to the specified evaporation percentage and within 0.1% by volume is taken directly from the database (10.6.3). The rate of change of temperature, or slope S_c, is calculated by equation (7): S_c = (T_u − T_L)/(V_u − V_L), in °C/%; T_u and T_L are the higher and lower temperatures and V_u and V_L their corresponding recovery or evaporation percentages, V_EP being the percentage corresponding to the final boiling point (12.2.3). When the final boiling point occurs before 95%, equation (8) is S_c = (T_EP − T_HR)/(V_EP − V_HR), HR being the highest reading before the final boiling point at 80% or 90% (12.2.4). For data points between 10% and 85% that are not listed in Table 7, equation (9) is S_c = 0.05 × [T_(V+10) − T_(V−10)] (12.2.5). At a specified temperature, the repeatability of the volume fraction is r_(V%) = r/S_c and the reproducibility R_(V%) = R/S_c (D.8.4); r and R are the temperature precision at that point, the repeatability symbol must not be written as T, and no software calculator is provided.

Quality control: The precision was established from interlaboratory statistical tests: 26 laboratories on 14 gasoline samples, 4 laboratories on 8 kerosene samples by the manual method, 3 laboratories on 6 kerosene samples by the automatic method, and 5 laboratories on 10 diesel samples by the manual and the automatic method respectively (12.1). Table H.1 of Annex H gives, for the different product groups and distillation methods, the clause in which the precision is located and the table used (12.1). Rate of change of temperature, or slope (12.2): To determine the precision of a result it is usually necessary to determine the rate of change, or slope, of temperature at that point; this variable, denoted S_c, equals the change in temperature per recovery percentage or per evaporation percentage (12.2.1). For the manual method of group 1 and the automatic method of all groups, the precision of the initial and final boiling points does not require calculation of the rate of change of temperature (12.2.2). Apart from the provisions of 12.2.2 and 12.2.4, the slope at any point of the distillation may be calculated by equation (7), using the data in Table 7 (12.2.3). For group 1 samples the precision data are based on slopes calculated from evaporation percentage data (12.2.6). For group 2, 3 and 4 samples the precision data (see Tables 9 and 10) are based on slopes calculated from recovery percentage data (12.2.7). When results are reported as recovery percentages, the slope used in the precision calculation is determined from recovery percentages; when results are reported as evaporation percentages, the slope used is determined from evaporation percentages (12.2.8). Manual method repeatability (95% confidence level) (12.3.1): Group 0: the difference between two repeat results for the final boiling point shall not exceed 3.5 °C; the difference between two repeat results for the temperature reading at each specified volume fraction shall not exceed the temperature change corresponding to a 2 mL change of distillate at that volume fraction; Annex I gives an example of the calculation of this temperature change (12.3.1.1). Group 1: the difference between consecutive test results obtained by the same operator in the same laboratory with the same apparatus on the same sample shall not exceed the value specified in Table 8 (12.3.1.2). Groups 2, 3 and 4: the difference between consecutive test results obtained by the same operator in the same laboratory with the same apparatus on the same sample shall not exceed the value specified in Table 9 (12.3.1.3). Manual method reproducibility (95% confidence level) (12.3.2): Group 0: reproducibility not established (12.3.2.1). Group 1: the difference between two single and independent test results obtained by different operators in different laboratories with different apparatus on the same sample shall not exceed the value specified in Table 8 (12.3.2.2). Groups 2, 3 and 4: the difference between two single and independent test results obtained by different operators in different laboratories with different apparatus on the same sample shall not exceed the value specified in Table 9 (12.3.2.3). Automatic method repeatability (95% confidence level) (12.4.1): Group 0: the difference between two repeat results for the final boiling point shall not exceed 3.5 °C; the difference between two repeat results for the temperature reading at each specified volume fraction shall not exceed the temperature change corresponding to a 2 mL change of distillate at that volume fraction; Annex I gives an example of the calculation of this temperature change (12.4.1.1). Group 1: the difference between consecutive test results obtained by the same operator in the same laboratory with the same apparatus on the same sample shall not exceed the value specified in Table 8 (12.4.1.2). Groups 2, 3 and 4: the difference between consecutive test results obtained by the same operator in the same laboratory with the same apparatus on the same sample shall not exceed the value specified in Table 10 (12.4.1.3). Automatic method reproducibility (95% confidence level) (12.4.2): Group 0: reproducibility not established (12.4.2.1). Group 1: two single and independent test results obtained by different operators in different laboratories with different apparatus on the same sample shall not differ by more than the value specified in Table 8 (12.4.2.2) [source unclear — the source text breaks off at this point].

Calibration, reporting and study of the applicability boundaries of precision: Clause 8.1 of the original requires other temperature measuring systems to be verified at intervals not exceeding 6 months and again after replacement or repair; 8.2.1 requires the automatic level tracking over the range 5-100 mL to have a resolution of 0.1 mL or better and a maximum error of 0.3 mL, with calibration verification at intervals not exceeding 3 months; 8.2.2 requires the automatic atmospheric pressure reading to be checked at intervals not exceeding 6 months. These three are not a single daily quality control frequency, nor do they show that a particular software or instrument already meets the requirements. The temperature window of the check liquids of Table 4 at 50% recovery in this method differs from the true boiling point: toluene has a true boiling point of 110.6 °C, with 105.9-111.8 °C for the manual method and 108.5-109.7 °C for the automatic method; hexadecane has a true boiling point of 287.0 °C, with 272.2-283.1 °C for the manual method and 277.0-280.0 °C for the automatic method. Clause 8.1.2.2 of the original permits analytical grade or other grades that ensure accuracy; no specific commercial batch value or availability is promised on the basis of method reference values. The toluene check gives no information on how well an electronic system simulates the temperature lag of mercury. 9.12: if the heating time and uniform rate requirements of 9.9 to 9.11 are not met, the distillation must be repeated; 9.13: heating is stopped at the decomposition point; 9.18: on early termination the sum of residue and loss is reported and the routine residue step is omitted, and that sum must not be treated as the residue alone. Clause 11: pressure to 0.1 kPa, volume percentages 0.5 for manual and 0.1 for automatic, temperature 0.5 °C for manual and 0.1 °C for automatic; it must be stated whether the pressure correction was applied, whether a drying agent was used, and whether the basis is recovery or evaporation. 11.6: the evaporation percentage is calculated without the corrected loss, and the corrected loss of 10.4 must not be substituted into 10.5; where manual interpolation or the graphical method is used this shall be noted, and extrapolation is prohibited. The full text of 12.4.2.2 of the original is that the reproducibility of the automatic method for group 1 follows Table 8, and 12.4.2.3 that the automatic method for groups 2/3/4 follows Table 10; the truncation of the old passage is not proof of complete technical coverage. For group 0 the repeatability of the final boiling point by manual and automatic methods is 3.5 °C and the reproducibility is not established; the temperature difference at a specified volume is compared using the smallest of the four d values of normative Annex I, and the fixed r/R of other groups is not applied. Group 1 uses slopes on an evaporation basis, while the relevant tables for groups 2/3/4 are established on a recovery basis, to be checked against 12.2 according to the basis actually reported; all cells of Tables 8/9/10 and the data points of Table 7 have not been reconstructed here into an operable calculation table. 12.5.1: because of the fully immersed thermometer or the simulating system, the distillation temperature of the method is slightly lower than the true temperature and varies with product and thermometer; 12.5.2: the bias relative to the true boiling point curve of ASTM D2892 has not been precisely studied; 12.5.3: there are no statistical data showing a bias between manual and automatic results, which does not mean the instruments have no error. The 95% method precision is not the uncertainty of a batch certificate. Annexes A/B/D/I are normative; C/E/F/G/H are informative; the instrument dimensions, tolerances, all dense tables, the controlled safety software and independent technical acceptance remain to be verified, and no scans or calculator are published.

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