Overview[1]
Ethylene glycol is an important chemical raw material and strategic material in the country. It is used to manufacture polyester (which can further produce polyester, PET bottles, and films), explosives, and glyoxal. It can also be used as antifreeze, plasticizer, hydraulic Fluids and solvents, etc. In 2009, China’s ethylene glycol imports exceeded 5.8 million tons. It is expected that my country’s ethylene glycol demand will reach 11.2 million tons in 2015, with a production capacity of about 5 million tons. The gap between supply and demand is still 6.2 million tons. Therefore, my country’s ethylene glycol production The development and application of new technologies have good market prospects. Internationally, ethylene oxide from petroleum cracking is mainly oxidized to obtain ethylene oxide, and ethylene oxide is hydrated to obtain ethylene glycol. In view of my country’s energy resource structure of being “rich in coal but short of oil and gas” and the long-term high price of crude oil, the new coal chemical technology of coal-to-ethylene glycol can not only ensure the country’s energy security, but also make full use of my country’s coal resources. It is the most realistic choice for the future coal chemical industry.
Ethylene glycol
Apply[1]
Reaction of ethylene glycol and alkyl halide
A method for synthesizing ethylene glycol monomethyl ether using methyl iodide and ethylene glycol as raw materials. This method uses iron perchlorate as a catalyst, and the selectivity of ethylene glycol monomethyl ether is 88%. This type of method contains hydrochloric acid as a by-product, which requires high equipment anti-corrosion and will increase equipment investment.
Reaction of ethylene glycol and monohydric alcohol
Charles Baimbridge disclosed in US2004/0044253A1 and others a method for synthesizing ethylene glycol ether by reacting ethylene glycol and monohydric alcohol. The catalyst used is perfluorocarbon sulfonic acid polymer, Nafion; the combination of monohydric alcohol and ethylene glycol substances The volume ratio is 3-5:1, the reaction temperature is 100-300°C, the pressure is 6.895MPa, the reaction time is 4-5 hours, the ethylene glycol conversion rate is 75.7%, and the total selectivity of ethylene glycol methyl ether and ethylene glycol dimethyl ether is 94.3%.
Use Cs/P/Si oxide as a catalyst to react ethylene glycol and methanol to synthesize ethylene glycol methyl ether. The reaction temperature is 300°C, the reaction pressure is 0.1-12MPa, and the ethylene glycol conversion rate is 46-23%. , the selectivity of ethylene glycol ether is 10-76%, that is, the conversion rate of ethylene glycol is 46% at low pressure, but the selectivity of ethylene glycol methyl ether is low, which is 10%. At a high pressure of 12MPa, the selectivity of ethylene glycol methyl ether reaches 76%, but the ethylene glycol conversion rate is only 23%. And there are many by-products, including diethylene glycol, 1,4-dioxane, acetaldehyde, 3-hydroxybutyraldehyde, 2-butenal, etc., making separation difficult.
Preparation[2]
The indirect synthesis of ethylene glycol from syngas is divided into two steps: CO oxidative coupling to synthesize dimethyl oxalate and catalytic hydrogenation of dimethyl oxalate to produce ethylene glycol. Since the 1980s, the successful development of atmospheric-pressure gas-phase catalytic coupling of CO to synthesize oxalate diesters has played an important role in changing the traditional process routes and raw material routes for the production of existing chemical products such as oxalate esters, oxalic acid, and ethylene glycol. significance. Ethylene glycol (EG), as an important organic chemical raw material, is widely used in the production of polyester fiber, antifreeze, lubricants and other industries. There are various process routes for synthesizing ethylene glycol, and currently the main industrial route is the petroleum ethylene route. With the increasing scarcity of petroleum resources, the development of process routes for producing ethylene glycol from coal-based synthesis gas has attracted more and more attention.
The reaction of hydrogenating dimethyl oxalate to ethylene glycol is complex. Cu catalyst is used. The hydrogenation process is carried out in multiple steps. Moreover, the reaction system has many side reactions and the hydrogenation selectivity is difficult to control. It is inevitable to produce ethylene glycol in Cu catalyst. Reactions between alcohols occur on the base catalyst, producing polyols, aldehydes, and ester by-products, which affects the hydrogenation selectivity. In the hydrogenation reaction of dimethyl oxalate, when the hydrogenation catalyst contains acidic or basic groups, there are four main types of reactions that may occur in the hydrogenation of dimethyl oxalate: carbonyl hydrogenation, alcohol hydroxyl dehydration, and ester addition. Hydrogen cracking and Guerbet reaction.
Hydrogenation of dimethyl oxalate produces methyl glycolate and methanol. The chemical equation is as follows:
(CH3OOC)2+2H2→CH3OOCCH2OH+CH3OH
Excessive hydrogenation of dimethyl oxalate produces glycerol and methanol. The chemical equation is as follows:
(CH3OOC)2+3H2→HOCH2CH(OH)CH2OH+CH3OH
Hydrogenation of methyl glycolate produces ethylene glycol and methanol. The chemical equation is as follows:
CH3OOCCH2OH+2H2→HOCH2CH2OH+CH3OH
Two molecules of ethylene glycol condense to form one molecule of diethylene glycol and one molecule of water. The chemical equation is as follows:
2HOCH2CH2OH→HOCH2CH2OCH2CH2OH+H2O
Excessive hydrogenation of ethylene glycol produces ethanol and water. The chemical equation is as follows:
HOCH2CH2OH+H2→CH3CH2OH+H2O
Ethylene glycol reacts with ethanol to produce 1,2-butanediol (1,2-BDO) and water. The chemical equation is as follows:
HOCH2CH2OH+CH3CH2OH→HOCH2CH(CH2CH3)OH+H2O
Ethylene glycol reacts with methanol to produce 1,2-propanediol (1,2-PDO) and water. The chemical equation is as follows:
HOCH2CH2OH+CH3OH→HOCH2CH(CH3)OH+H2O
As can be seen from the reaction equation, during the preparation of ethylene glycol, there will be an intermediate product of methyl glycolate from the hydrogenation of dimethyl oxalate, and the accompanying by-products include methanol, ethanol, water, diethylene glycol, Glycerol, 1,2-propanediol and 1,2-butanediol, etc. The presence of by-products affects the purity of ethylene glycol products. For example, 1,2-propanediol and 1,2-butanediol affect the UV transmittance of ethylene glycol products. Therefore, the by-products are separated and the high value-added products contained in them are recovered. , it is very critical to improve the purity and UV transmittance of ethylene glycol products.
Document US4,966,658 proposes to use ethylbenzene, 3-heptanone, diisobutyl ketone, etc. as entrainers, and use azeotropic distillation method to separate ethylene glycol, 1,2-butanediol, and 1,3 -Butanediol, the number of theoretical plates in the distillation column is 30. Document CN103193594A uses a stream containing ethylene glycol and 1,2-butanediol to remove light components through a separation tower and then enters the middle and lower part of the azeotropic distillation tower, where the ethylene glycol forms a co-evaporator with the entrainer added at the top of the tower. The boiling matter is evaporated from the top of the tower and enters the phase separator after condensation. After phase separation, the upper entrainer-rich phase returns to the top of the tower to continue participating in the azeotrope, and the lower ethylene glycol-rich phase enters the fourth separation tower for purification to obtain ethyl alcohol. Glycol products.
Document CN102372601A uses resolving agent I and resolving agent II plus distillation to separate ethylene glycol, propylene glycol and butylene glycol. Wu Liangquan et al. analyzed the mechanism of impurities produced during the hydrogenation of oxalate esters to ethylene glycol, and briefly described the impact of different impurities on the UV value of ethylene glycol products (Natural Gas Chemical Industry, 2011, 36(6):66-70) . CN203177U uses a two-stage dealcoholization tower for methanol recovery and adds a dealcoholization tower to recover ethanol and a dealtylene glycol tower to collect butanediol. It can collect ethanol and butanediol with higher purity to increase revenue and reduce costs. At the same time, Part of the qualified ethylene glycol extracted from the top of the ethylene glycol refining tower is returned to the dealtylene glycol tower.
Main reference materials
[1] Bai Ying, Lu Chunshan, Ma Lei, Chen Ping, Zheng Yifan, & Li Xiaonian. (2006). Ce and mg modified γ-al2o3 supported pt catalyst catalyzed aqueous reforming of ethylene glycol Hydrogen. Journal of Catalysis, 27(3).
[2] Zhao Guanhong, Zheng Mingyuan, Wang Aiqin, & Zhang Tao. (2010). Catalytic conversion of cellulose to ethylene glycol by tungsten phosphide. Acta Catalytica Sinica, 31(8), 928-932.
[3] Zhou Zhangfeng, Li Shaoji, Pan Pengbin, Lin Ling, Qin Yeyan, & Yao Yuangen. . Progress in coal-to-ethylene glycol technology. Chemical Engineering Progress (11), 7-13.
