https://www.cas.cn/cm/202602/t20260213_5102559.shtml

Ethanol is both an important basic chemical and a recognized clean gasoline additive. However, the promotion of ethanol gasoline in China faces a dilemma. Global ethanol production has heavily relied on the “grain route” through fermentation of corn, sugarcane, etc. For China, with its large population and limited land, this route impacts national food security. But China has abundant coal reserves.

There are two main technological routes for coal-to-ethanol production:

• direct ethanol production from coal via syngas, which requires the use of the precious metal catalyst rhodium and causes equipment corrosion, resulting in high production costs
• ethanol production from coal via acetic acid, which is only feasible when there is an overcapacity in acetic acid production, and due to the highly corrosive nature of the reaction system requires huge investment in equipment.

A team led by Zhu Wenliang at the CAS Dalian Institute of Chemical Physics and Liu Zhongmin, an academician of the Chinese Academy of Engineering, has spent more than ten years to develop an industrial procedure for producing ethanol from dimethyl ether via methyl acetate. They use coal-based syngas as raw material, first producing methanol and dimethyl ether, then allowing the dimethyl ether to undergo a carbonylation reaction to produce methyl acetate, and finally hydrogenating it to obtain pure ethanol. For this process, a highly active and stable molecular sieve carbonylation catalyst was developed, achieved a breakthrough in dimethyl ether carbonylation, and an industrial demonstration project was launched in collaboration with Shaanxi Yanchang Petroleum Group.

In 2017, the world’s first 100,000-ton/year coal-based ethanol industrial demonstration project started up, producing high-quality anhydrous ethanol and achieving a global first industrial demonstration.

A 500,000-ton/year coal-to-ethanol project was the team’s next target and required to develop a new generation of industrial catalysts with higher activity and stronger stability. After four years of R&D, an improved catalyst had an activity increased to 1.7 times the original, and its service life was extended from 6,400 hours to 16,400 hours. In 2022, this catalyst was first applied to a 100,000-ton/year industrial demonstration plant, where its performance was fully verified. And a 500,000-ton/year coal-to-ethanol project was commissioned. At the end of 2023, the world’s largest 600,000-ton/year ethanol plant in Huaibei, Anhui Province, completed trial production. In February 2024, it started up and produced qualified ethanol in one go, achieving a project completion time of 20 months and full-process commissioning in two months.

The team has built robust global intellectual property, obtaining patent authorizations in over 20 countries and regions, including Europe, Iran, and Saudi Arabia. To date, 15 technology implementation license agreements have been signed, with a capacity of 5.15 million tons/year; 7 projects are already in operation, with a capacity of 2.65 million tons/year, driving direct investment exceeding 30 billion yuan. Two sets of equipment have been licensed to Belt and Road Initiative countries, realizing the export of original Chinese chemical technology. In 2024, this technology was recognized as a green patent technology under the Belt and Road Initiative, and in 2025, it was selected as one of the top ten outstanding invention patent cases in Belt and Road Initiative countries and regions.

Based on the calculation that 3 tons of grain produce 1 ton of ethanol, the project will save approximately 1.5 million tons of raw grain for bioethanol production annually. While alleviating China’s reliance on grain for ethanol production, the project can also convert approximately 1.6 million tons of low-rank coal annually, providing strong technical support for the clean and efficient utilization of coal.

The process utilizes coke oven gas as starting material. But the sources of raw materials is adaptable to more scenarios. China is the world’s largest steel producer, and the coke oven gas, blast furnace gas, and converter gas produced annually are rich in carbon monoxide, hydrogen, and methane. Currently, most steel plant gas is only used for combustion power generation, which is not economically viable, wasting valuable carbon and hydrogen resources and generating large amounts of carbon dioxide. If a large amount of steel plant exhaust gas can be used to produce ethanol using this technology, it will promote the large-scale production of clean fuel ethanol.

In the future, the team will focus on the integrated development of coal chemical industry and petrochemical industry, bringing more possibilities to promote the sustainable development of clean energy.

Photo: Yushen 500,000-ton/year coal-based ethanol plant, courtesy of Dalian Institute of Chemical Physics