[Background and Overview][1]
Tetraethylene glycol is a valuable chemical product. It is mainly used as an extraction solvent for the extraction of aromatic hydrocarbons (benzene, toluene and xylene) from the oil produced by catalytic reforming in refineries and cracked light tar. It can also be used as an extraction solvent. It is used as a raw material for the synthesis of tetraethylene glycol alkyl ethers and polyester resins. In the aromatic hydrocarbon extraction process in which glycol is used as the extraction solvent, tetraethylene glycol is a high-efficiency and energy-saving aromatic hydrocarbon extraction agent.
【Preparation】[1]
The preparation method of tetraethylene glycol generally uses ethylene oxide and diethylene glycol as reaction raw materials, and alkaline substances such as alkali metal hydroxides as catalysts. Under certain reaction temperature and pressure conditions, the process is carried out step by step. level addition reaction, the structural formula is HO(C2H5O)n(n=2, 3, 4…), with Mixtures of triethylene glycol, tetraethylene glycol and pentaethylene glycol with various addition degrees. By optimizing and adjusting the raw material ratio and other process conditions, this method can obtain products mainly composed of triethylene glycol and tetraethylene glycol, which are then separated and purified. , to obtain tetraethylene glycol products with high industrial utilization value.
In the preparation method of the prior art, since the materials after the synthesis reaction are highly alkaline, acids such as acetic acid, sulfuric acid or phosphoric acid are often used for neutralization treatment, and the salt compounds generated after the treatment remain in the reaction materials. , a small amount of alkaline catalyst also remains in the reaction materials, and these substances enter the separation system together with the reaction materials. Due to the higher boiling points of glycol substances, the boiling point of triethylene glycol is 287.4°C (101.34 kPa) and the boiling point of tetraethylene glycol is 327.3°C (101.34 kPa). In the subsequent multi-tower distillation and separation process, the operating temperature of the tower kettle needs to be Above 200°C (vacuum degree is about 10 mmHg), these salt compounds in the distillation separation system make the reaction products prone to various side reactions such as catalytic decomposition, condensation or polymerization under high temperature conditions, causing product degradation. The rate decreases. Impurities with small molecular weight generated by decomposition enter the overhead product fraction, reducing product purity. Colored impurities generated by condensation oxidation reaction enter the product, further deepening the appearance coloration of the product, seriously affecting product quality, directly Affects the industrial application of tetraethylene glycol.
A new method for preparing tetraethylene glycol can solve the above technical problems. It uses glycol and ethylene oxide as raw materials, and uses one of alkali metal hydroxides and alkaline earth metal oxides or a mixture thereof as a catalyst. The amount of catalyst accounts for 0.02 to 1.5% of the weight of raw materials. The reaction is carried out under the conditions of reaction temperature 90-220°C, reaction pressure 0.2-0.5MPa, and the weight ratio of ethylene oxide and glycol is 1:1-4 to obtain triglyceride. The reaction materials of alcohol and tetraethylene glycol are separated and purified into a rectification tower to obtain a tetraethylene glycol product, which is co-produced with triethylene glycol. Before the reaction materials enter the rectification tower for separation and purification, acid clay and diatomaceous earth are used. The mixture is pretreated, the treatment temperature is 30~90℃, the treatment time is 0.1~4 hours, the dosage of acidic clay and diatomite accounts for 0.5~5% of the total weight of the reaction material, in which the weight ratio of acidic clay and diatomite It is 8~15:1.
In the above technical solution, the raw material glycol can be diethylene glycol, triethylene glycol or their mixture. The preferred range of catalyst dosage is 0.02-0.5% of the weight of raw material input. The reaction material processing temperature is preferably 40-40%. 60°C, and the treatment time is preferably 0.3 to 2 hours. The acidic clay and diatomite used are commercially available ordinary types of acidic clay and diatomite. The preferred dosage range is 1 to 3% of the total weight of the reaction materials. The acidic clay The weight ratio to diatomite is preferably 9 to 12:1. During the reaction, the alkali metal hydroxide of the catalyst component used can be selected from one of lithium hydroxide, sodium hydroxide, potassium hydroxide or their mixture, and the alkaline earth metal oxide can be selected from calcium oxide and strontium oxide. , one of barium oxide or their mixture, the preferred reaction temperature in the reaction is 110~170C, the reaction pressure is 0.2~0.4MPa, the weight ratio of ethylene oxide and glycol is 1:2~3, using the above catalyst and According to the preparation method of the process conditions, tetraethylene glycol product can be obtained and triethylene glycol can be co-produced at the same time. The reaction results are shown in Table 1.
[Application][2]
After the lubricating oil is used for a period of time, due to its own oxidation and metal impurities, moisture, etc. brought by the environment, the function of the lubricating oil will decrease. After reaching a certain level, it must be replaced, and the replaced oil will become waste. Oil. Moreover, lubricating oil additives contain large amounts of chlorine, sulfur, phosphorus and metal elements, which are harmful to humans and animals. Therefore, how to deal with these waste lubricants has become an issue of increasing concern. Waste lubricating oil can be refined using tetraethylene glycol as the main solvent and sulfolane as the auxiliary solvent. The waste lubricating oil was naturally settled for 24 hours to remove moisture and mechanical impurities at the bottom; the waste lubricating oil was processed through a vacuum distillation device, and the lubricating oil fraction between 220 and 350°C was taken for experimental research. When the agent-to-oil ratio (volume ratio) is 1:1, 1.5:1, 2:1, 2.5:1, and 3:1 respectively, heat the water bath to 85°C, stir at a constant temperature for 30 minutes, cool and pour into a separatory funnel. Let stand for 1 hour and separate layers; then repeat the operation at temperatures of 95, 105, 115, and 125°C. Add 5% (mass fraction), 10%, 15%, 20%, and 25% to the solvent under optimal conditions. % sulfolane, respectively, at temperatures of 85, 95, 105, 115, and 125°C to refine waste lubricating oil and recover the oil.
[Main reference materials]
[1]CN02111017.4
[2]Liu Ying, Chen Wenyi, Yang Qianwen, Liu Huizhen, Yao Erwei. Research on refining and regenerating waste lubricating oil with tetraethylene glycol composite solvent [J]. Applied Chemical Engineering, 2016, 45(11): 2091-2094.
