Purification of Phenylaldehyde by Vacuum Batch Distillation Xu Songlin, Ying Anguo, Wang Shuhua (National Engineering Research Center of Distillation Technology, Tianjin University, Tianjin 300072, China) Temperature range and suitable operating methods. The test results show that: using variable reflux ratio operation, the operating pressure does not exceed 40 kPa, the pyrolysis aldehyde content of the kettle temperature below 180K product reaches 99.0% or more, the yield reaches 724%, and the octanol impurity content is lower than 5X10-\ Applied chemical process dynamic simulation software HysysPlant 22 simulated the test process, using the constant tower top concentration and variable reflux ratio control strategy, the simulation results and test values â€‹â€‹are in good agreement.
Tao Xing, also known as a heptyl-7-butyrolactone, is a colorless, transparent to slightly yellow liquid, widely used in food flavor industry 111. Due to the incomplete separation of the raw material octanol in the process of synthesis of peach aldehyde, content Exceeding the standard, failing to meet export requirements, can only be sold at a lower price.
Therefore, it is of great practical significance to study the separation technology of peach aldehydes, increase the purity of the peach aldehydes, reduce the impurities in the products to internationally recognized standards, and make them high value-added products. In this paper, vacuum intermittent distillation separation method was used to study the influence of several factors such as operating pressure, operating temperature and reflux ratio on the purity, yield and impurity content of acetaldehyde.
0*C is a high-boiling aromatic material with certain heat sensitivity. The raw material, peach aldehyde, has a transparent appearance, no turbidity and suspended matter, and a slight peach fragrance. The raw material has a peach aldehyde content of 6677%, which is produced by Anhui Chemical Industry Co., Ltd.
Gas Chromatograph Model 1790F; Column Type HP-5, Column Gauge 300*C; Detector FID; Sample Load 0.6 Torr, Sampler Splitter (Distribution Ratio 1:100) Carrier Gas is Nitrogen; Rice uses area normalization.
1.3 Thermal-sensitivity test apparatus and method: The apparatus involved is a 250-mL flask, a piezoelectric heat jacket, a thermometer, and a condenser. METHODS: 150 mL of crude peach aldehyde was added to a 250 mL three-necked flask. The temperature of the heating mantle was adjusted to uniform temperature, and the temperature was increased to the target temperature. The sample was stable at this temperature for about 1 hour. The content of mellow aldehyde in raw materials was determined by gas chromatography.
1.4.2 Determination of the test operation method The chromatographic analysis of raw materials shows that the impurity content of octanol which is lower than the boiling point of the mellow aldehyde (mass fraction, the same below) is 17 90% and the impurity content higher than that of the peach aldehyde is 15.33. %. It can be seen that the peach aldehyde is an intermediate component in the raw material. During the separation, components with a higher boiling point than mellowaldehyde are removed, and impurities lighter than it are removed, so that the content of mellow aldehyde is more than 99.0%, and the content of octanol is lower than 5Ã—10'. Test Idea: The initial stage adopts a full reflux ratio operation (about (40min), the light components enriched at the top of the tower; then, using a larger reflux ratio to remove lower boiling impurities such as octanol, while avoiding a large number of active ingredients peach acetaldehyde was distilled out; when the overhead distillate When the content of mellow aldehyde reaches the requirement, it begins to collect, and then uses a constant reflux ratio for a period of time to obtain product I; at the later stage of separation, the reflux ratio is increased, the purity of the mellow aldehyde is maintained within the required range, and the product is obtained; The part of the kettle is also an impurity section. The reflux ratio changes as shown.
Relationship between boiling point and pressure of Phenolic Aldehyde 4 Vacuum intermittent distillation 1.4.1 Test device Test device As shown in the figure, the height of the effective packed section column is 25mm in diameter, and the high-efficiency stainless steel 0 ring packing with 3mmX3mm is installed.
Thermal sensitivity analysis: The heat sensitivity curve of mellow aldehyde is as shown.
As can be seen from the figure, at 180*C, the purity of the raw material mellow aldehyde did not change substantially within 5 hours; at 200*C and 220 degrees 0, the mellow aldehyde content decreased by 9.77% and 20.57%, respectively, which was the boiling point and pressure of the mellow aldehyde. Relationship lines. Combined with heat-sensitive analysis, it can be seen that the tower kettle temperature should not exceed 180C in the process of separation of the peach aldehyde. The system operating pressure should not exceed 4.0 kPa. 2 Test results and discussion 3 Computer simulation of the batch distillation process 2.1 Determination of the minimum theoretical plate number and the determination of the minimum reflux ratio Peach The aldehyde raw material is a multi-component mixture and the minimum theoretical plate number and minimum reflux ratio of the separation process must be determined. The calculation method for the minimum theoretical number of plates (NT) and the minimum reflux ratio (Rmin) in the medium and intermittent batch feeds is used to calculate the two pseudo binary components: 1) The light components in the raw materials are cut to make mellow aldehydes Nt and Rmm when the purity was purified from 6677% to above 990% were 17 and 7.5, respectively; 2) Nt and Rmm when the purity of the mellow and heavy components were cut and kept at 99.0% were 15 and 6.5, respectively. The height of the high-efficiency packed column used in the device can meet the separation requirements.
2.2 Variations in the temperature of the top of the tower and the tower and the effect on the purity of the product indicate the changes in the temperature at the top of the tower, the temperature in the tower, and the effect on the purity of the product. In the full reflux stage, the temperature at the top of the tower, the temperature at the bottom of the tower and the purity of the product are all increased; the operation at a high reflux ratio of 40min and 90min, the removal of impurities, the temperature of the kettle and the top gradually increase, and the purity of the product decreases with the removal of light components. Reached 99.0%; 90min280min constant reflux ratio operation, product collection phase, the top of the tower and the tower temperature were stable at about *C, the purity was stable at 99. 1%; 280min, the tower temperature began to rise, the product purity has decreased ; To 300min, the product purity is less than 99.0%, stop production. The entire test process takes about 5 h and the system pressure does not exceed 40 kPa. Batch distillation is a dynamic process. Ion Exchange and Adsorption, 2002, 18(1)45-50.
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