Diethylene glycol (DEG) is a by-product of the hydrostatic production of ethylene oxide (EG). Its amount varies with process conditions. Generally, the amount of by-product diethylene glycol DEG is 8% of the EG output. ~10%. In recent years, with the continuous development of my country’s polyester industry and petrochemical industry, the output of ethylene glycol, an important raw material, has continued to increase. It is expected that my country’s total ethylene glycol production capacity will reach approximately 4.2 million tons/year by 2010. By then, as ethylene glycol The annual output of diethylene glycol, a by-product of alcohol production, can reach about 400,000 tons. Therefore, it is an important topic to develop downstream products of diethylene glycol, make full use of diethylene glycol resources, and improve its economic benefits. At present, a lot of work has been done on the comprehensive utilization of diethylene glycol in China. The new progress in the comprehensive utilization technology of diethylene glycol in China this year is summarized as follows.
1 Direct utilization of diethylene glycol[1]
Diethylene glycol is a colorless, odorless, transparent, hygroscopic and viscous liquid. It is easily soluble in water, alcohol, acetone, ether, ethylene glycol and other polar solvents. Its chemical properties are similar to ethylene glycol. Direct utilization can be mainly used as solvents for various purposes, natural gas dehydration desiccant, aromatic hydrocarbon separation extraction agent, textile lubricant, softener, finishing agent, as well as solvents such as nitrocellulose, resin, grease and printing ink, and also used as brakes It is an antifreeze component in liquids and compressor lubricating oils. It can also be used to prepare cleaning agents and as a dispersing solvent in other daily chemicals such as inks. For example: the water content of natural gas dehydrated with 99% diethylene glycol can be as low as 48 mg/m3; diethylene glycol is used as a BTX extraction solvent in the Eudicus device, with good selectivity and an aromatic hydrocarbon recovery rate of >98%; As a dyeing and finishing auxiliary for textiles, alcohol can improve the transfer of dyes and washing fastness, enhance the antistatic properties, water absorption and stain resistance of synthetic fibers; diethylene glycol is used as an ink wetting agent, which can improve the fluidity and durability of ink. Viscosity quality, increases light resistance and long-term storage stability, accelerates the fixation and drying speed of the ink on the substrate.
2 Processing and Utilization of Diethylene Glycol
The molecular structure of diethylene glycol contains two functional groups, ether bond and hydroxyl group, which give it unique physical and chemical properties. It can be used to produce a variety of chemical products such as ethers, acids, esters, and amines, and is widely used in petroleum. It is widely used in chemical, rubber, plastic, textile, coating, adhesive, pharmaceutical and other industries.
2.1 Morpholine[2-12]morpholine (1, 4-oxazacyclohexane) is an important organic chemical raw material and chemical intermediate with a wide range of uses. It can be used as rubber additives and textile dyeing and weaving auxiliaries. , pharmaceutical intermediates, plastic additives, rust inhibitors, surfactants, optical polishing agents, polyamide foaming agents, water treatment agents, preservatives, etc. In addition, morpholine is also an important organic solvent.
Before 1990, my country was completely dependent on imports of morpholine. Subsequently, many domestic scientific research institutes conducted extensive research on its synthesis technology and made great progress. Several industrial units were built successively to meet the growing demand for morpholine in the domestic market. growing demand. In recent years, with the continuous advancement of science and technology, new uses of morpholine have continued to emerge, and the market demand for morpholine has continued to increase. According to market statistics, my country’s demand for morpholine in 2007 was approximately 15,000 tons.
The production of morpholine currently mainly uses diethylene glycol and ammonia as raw materials. Under the action of a catalyst, the ammonolysis and dehydration reactions are completed simultaneously to obtain morpholine products. According to different operating pressures, this technology is divided into three synthesis processes: high-pressure liquid phase method, low-pressure gas phase contact method and normal pressure gas phase method. The high-pressure liquid phase method reacts at a pressure of 6.5~22.5MP and requires high-pressure equipment. From a thermodynamic point of view, high pressure is unfavorable to the reaction. The morpholine yield is low, generally below 49%, and the catalyst is easily pulverized and has a short life.
The reaction pressure of low-pressure vapor-liquid phase contact method is generally in the range of 0.5~4.2MPa, and diethylene glycol is in a vapor-liquid mixed phase state. Nanjing Chemical Plant No. 2 pioneered the use of low-pressure catalytic synthesis of morpholine from diethylene glycol in 1993. In 1994, the Research Institute of Jilin Chemical Company conducted in-depth research on the low-pressure synthesis of morpholine from diethylene glycol and established 6 sets of equipment in China. This technology uses a fixed-bed reactor and a hydrogenation Ni-Cu catalyst at a temperature of 200°C~260°C. ℃, gas phase ammoniation under pressure of 1.4~1.8MPa, the diethylene glycol conversion rate can reach more than 98%, the morpholine content in crude morpholine reaches 55%~65%, and the diethylene glycol consumption per ton of morpholine is less than 1.7 tons , the product purity can reach over 99.5%. At present, various indicators of domestically developed low-pressure method technology have reached the international advanced level.
The operating pressure of the normal pressure vapor phase method is less than 0.5MPa, and the reaction is carried out within a temperature range that keeps diethylene glycol basically in the vapor phase. The Beijing Research Institute of Chemical Industry has developed the technology for the synthesis of morpholine from diethylene glycol using the atmospheric pressure vapor phase method, and has successively built three sets of 500t/a production units, using overflow bed reactors, Ni-Cu catalysts, and diethylene glycol. Add 50% dilution with water, and carry out catalytic ammonia reaction at a pressure of 5.0MPa and a temperature of 210℃~240℃. The single-pass yield of morpholine can reach up to 75%. Each ton of morpholine consumes 2.0~2.4 tons of diethylene glycol. The catalyst life is three months. The atmospheric pressure method does not require pressure equipment and is safe to operate, but the catalyst life is short, the selectivity is not high, and the raw material consumption and energy consumption are high.
Most of the catalysts used in the catalytic amination of diethylene glycol (DEG) to prepare morpholine are hydrogenation or dehydrogenation catalysts, and the main catalyst is Ni. Patent CN1031663A uses Al2O3 as a carrier to load Ni, Cu, Cr, and Ti active components. The conversion rate of diethylene glycol is 82.79%, and the selectivity of morpholine is 95.44%. However, the content of catalyst active components is high, the catalyst production cost is high, the repeatability is poor, and there are still shortcomings in its activity, stability, strength and selectivity. Jilin Chemical Company has developed a dihydrogen with low active component content.��Qingsong. Synthesis of diethylene glycol dibenzoate from Cs2.5H0.5PW12O40/S iO2[J]. Liaoning Chemical Industry, 2003, 32 (9): 372-374.
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