Test Method for Vacuum Distillation Range of Wax Oil
Wax oil is a colorless, transparent, semi-solid or liquid substance obtained from petroleum, animal fats or vegetable oils through processes such as refining, decolorization and deodorization. It is mainly composed of macromolecular alkanes including cerane, isopentane and n-pentane, together with a small amount of low-molecular alkanes. It features high melting point, low viscosity and low volatility, and is widely used in candle making, cosmetics, pharmaceuticals, food packaging, lubricating oils, polishing agents and other fields.
Experimental Purpose
As a heavy petroleum product, the determination of the distillation range of wax oil is of great industrial significance.
①To evaluate its light and heavy component distribution and evaporation performance:As a complex mixture, wax oil has no fixed boiling point. Determination of its distillation curve can directly reflect the proportion of light and heavy components, demonstrate its vaporization characteristics at different temperatures, and thus evaluate its evaporation performance.
② For product quality assessment and process optimization:In the petroleum refining process, wax oil is often used as feedstock for secondary processing units such as catalytic cracking and hydrocracking. Determination of its distillation range provides key feed parameters for the process, helping to adjust reaction temperature, pressure and catalyst activity, so as to optimize product quality. In addition, distillation range data can reflect key physical properties such as viscosity, calorific value and molecular weight. Judging the distillation range width or final boiling point can identify the composition of wax oil and evaluate its product quality.
③ To provide a basis for engineering design:The distillation range data of wax oil serves as the foundation for designing distillation units (such as vacuum distillation towers) and conducting thermodynamic calculations. It helps to determine operating conditions including the number of theoretical plates and reflux ratio required for separating different components, providing necessary engineering parameters for industrial production.
Experimental Apparatus
① SD-0165 Vacuum Distillation Range Tester
② Auxiliary materials: unglazed porcelain rings, vacuum grease, chemically pure anhydrous calcium chloride, cleaning solvent, etc.
Experimental Procedures
① Inspect the instrument and all vessels to ensure they are dry and free of contamination, then connect the power supply.
② Take the sample and perform dehydration treatment. Weigh or measure 100 mL or an equivalent mass of the sample, and transfer it into a clean distillation flask containing porcelain rings. Record the temperature at which the sample is measured, then place a thermometer at the center of the distillation flask neck.
③ Start the vacuum pump, close the vent valve, check the airtightness of the system, and adjust the vent valve to achieve the required residual pressure for the test.
④ Apply heat. During distillation, control the time from the initial boiling point to 10% distillate recovery to be no more than 6 minutes; control the distillate recovery rate at 4–5 mL per minute between 10% and 90% recovery. At 90% recovery, one final adjustment of heating intensity is permitted to ensure the time from 90% to the final boiling point does not exceed 5 minutes.
⑤ Record the temperature and distillate percentage in accordance with the requirements of the sample technical standard, and simultaneously record the residual pressure and time. The fluctuation of residual pressure during distillation shall not exceed 0.5 mmHg.
⑥ Stop heating when distillation reaches the final boiling point. Remove the thermal insulation cover, allow the thermometer to cool naturally to below 100℃, then slowly vent the system. After the mercury vacuum gauge returns to its original position, stop the vacuum pump.
⑦ Convert all measured temperatures under vacuum to equivalent temperatures at atmospheric pressure using the atmospheric-vacuum temperature conversion chart. Repeat the experiment 1 to 2 times.
Experimental Results and Analysis
After testing and analysis, the distillation properties of the wax oil are determined as follows:
Initial boiling point: 275℃
50% recovery temperature: 396℃
95% recovery temperature: 448℃
The results meet the applicable petroleum product standards.