Let’s discuss things related to the coal-based ethylene glycol production process

I hope someone can give me some recommendations. Last edited by Wang Jingliang on 2007-12-14 at 11:30.]

The existing processes for synthesizing EG (ethylene glycol) from coal start with syngas produced from coal, and these processes are divided into direct and indirect methods. The direct process involves the direct synthesis of EG from syngas ； The indirect process involves converting syngas into EG via some intermediate compounds, such as methanol or formaldehyde.

This is a new technology; currently, ethylene glycol is mainly produced through the hydration of ethylene oxide

What are the requirements for equipment in the process of producing ethylene glycol from coal, where carbon monoxide is used to generate diethyl oxalate, which is then hydrogenated to produce ethylene glycol?

The EG synthesis process based on coal chemistry has become a topic of interest due to its advantages such as wide and inexpensive raw material sources and high technical and economic efficiency. Especially for a country like China, which has abundant coal but little oil, developing coal-based processes is of great significance. The coal-based ethylene glycol project we are examining consists of two main units: an oxalate production unit and an oxalate hydrogenation unit, which use CH3OH, O2, and CO to synthesize oxalates ； Next, the oxalate ester is hydrogenated to produce ethylene glycol; the process for synthesizing the oxalate ester is carried out in two steps: the first step is a coupling reaction, using supported Pd/α-Al2O3 as a catalyst, at 120℃ ； Under very mild conditions of 0.2–0.5 MPa, it reacts with methyl nitrite to produce dimethyl oxalate and nitrogen monoxide: 2CO + 2CH3ONO → (COOCH3)2 + 2NO. The second step is a regeneration reaction; the nitrogen monoxide produced in the coupling reaction is separated from the product and sent to a regeneration reactor, where it reacts with methanol and oxygen to form methyl nitrite, as shown in the following equation: 2CH3OH + 2NO + 1/2O2 → 2CH3ONO + H2O. The overall reaction for the formation of dimethyl oxalate from carbon monoxide gas is: 2CO + 2CH3OH + 1/2O2 → (COOCH3)2 + H2O. The hydrogenation of oxalates is carried out using a copper-based catalyst at moderate temperatures of 200–230°C and pressures of 2–3 MPa; the reaction equations are as follows: (COOCH3)2 + 2H2 → CH3OCOCH2OH + CH3OH; CH3OCOCH2OH + 2H2 → (CH2OH)2 + CH3OH; (CH2OH)2 + H2 → C2H5OH + H2O. Apart from by-products such as ethanol, methanol is recovered and reused. The overall reaction for the synthesis of ethylene glycol from coal is: 2CO + 4H2 + 1/2O2 → (CH2OH)2 + H2O. From this overall reaction equation, it can be seen that ethylene glycol is produced using syngas. Since little methanol, NO, or N2 is used in this process, the production of ethylene glycol from syngas is similar to the methanol synthesis process, offering significant cost advantages, with costs comparable to those of methanol synthesis.

The plant for producing ethylene glycol from syngas consists of the following six sections: ① Ammonolysis, fresh esterification, and absorption; ② Gas purification and recycled esterification; ③ Dimethyl oxalate synthesis unit; ④ Dimethyl oxalate purification unit; ⑤ Dimethyl oxalate hydrogenation unit; ⑥ Ethylene glycol purification unit. The production of ethylene glycol via the syngas indirect method represents another promising new product in coal chemical industry that utilizes coal as a substitute for oil, following the synthesis of acetic acid through carbonylation. China is at the forefront of research in this field, with breakthroughs having been achieved in terms of catalyst lifespan. To date, two plants with a capacity of 200,000 tons per year have been constructed using this method: one in Tongliao, Inner Mongolia, with an annual capacity of 200,000 tons, and another in Shuangyashan, Heilongjiang, operated by the Bando Company, also with an annual capacity of 200,000 tons.

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