The large-scale development of ethanol produced from coal should not be pursued recklessly

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Blind large-scale development of ethanol produced from coal is not advisable. Author/Source: Huahua Network – Coal Chemical Industry. Date: March 5, 2018. Clicks: 22. On September 13, 2017, 15 ministries and commissions including the National Development and Reform Commission jointly issued the \"Implementation Plan for Expanding the Production of Biofuel Ethanol and Promoting the Use of Ethanol-blended Gasoline in Vehicles\" (hereinafter referred to as the Plan). According to the plan, by 2020, nationwide coverage of ethanol-blended gasoline for vehicles will be essentially achieved. The plan specifies the need to expand the production of biofuel ethanol and promote the use of ethanol-based gasoline in vehicles, but it does not clarify whether coal-derived ethanol is also included. Therefore, whether coal chemical enterprises can take advantage of the new policies is a matter of great concern within the industry. Since 2004, biofuel ethanol has been gradually introduced in 11 provinces and regions across the country. Among them, Henan, Anhui, Heilongjiang, Jilin, Liaoning, and Guangxi see its promotion and application across the entire province. According to statistics, in 2014, 2.3 million tons of modified fuel ethanol were sold in 9 cities in Hubei, 7 cities in Shandong, 6 cities in Hebei, 5 cities in Jiangsu, and 3 leagues/municipalities in Inner Mongolia. Additionally, 23 million tons of E10 ethanol gasoline was sold (accounting for about 1/4 of the total amount of gasoline used for vehicles nationwide). Sales in 2015 were roughly on par with those in 2014. In 2016, the consumption of fuel ethanol was 2.6 million tons, of which 2.06 million tons were produced domestically and 540,000 tons were imported. As can be seen from the above data, the development of fuel ethanol production and consumption in China is not fast at present. According to statistics, China’s gasoline production in 2016 was 129.32 million tons; based on the requirement of a 10% addition, the demand for fuel ethanol was 12.932 million tons. Although there are currently only 8 biofuel ethanol manufacturers in the country, with a total production capacity of 2.59 million tons, it is difficult to determine how large the market potential for coal-based ethanol will be, given that the introduction of this policy is expected to lead to a rapid expansion of bio-based ethanol production capacity. If coal-based ethanol companies want to take advantage of favorable policies, they need to focus on industrialization and cost competitiveness. To produce ethanol from coal, syngas must first be obtained. Starting from syngas, ethanol can be obtained directly, or it can be produced through intermediates such as methanol, ethylene, acetic acid, dimethyl ether, etc. To date, there are four available processes for producing ethanol from coal: Route 1: Direct synthesis of ethanol from syngas. One approach involves the direct synthesis of C1-C5 lower alcohols from carbon monoxide and hydrogen in the presence of a catalyst, followed by the separation of ethanol. Most of the products obtained through this route are methanol; the products vary depending on the catalyst used. The drawback is that the ethanol content is low, rarely exceeding 50%. Since the early 1980s, the Shanxi Coal Chemistry Institute of the Chinese Academy of Sciences has been developing a zinc-chromium catalytic system suitable for this process. Through research on industrial pilot tests, product dehydration, and precise desulfurization of feed gas, it has completed 1,200 hours of pilot-scale operation. Another approach is the direct production of high-concentration ethanol from syngas, using a rhodium catalyst. In the 1980s, the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences developed rhodium-supported catalysts. Pilot test results show that the catalyst maintains stable performance after 1200 hours of continuous operation, with an ethanol selectivity of over 80%. In 2011, Jiangsu Supor Group adopted this technology in a research and development project aimed at creating a complete set of systems for producing ethanol from 30,000 tons of syngas per year. Route 2: Hydrogenation of acetic acid to ethanol. The technology developed by U.S.-based Celanese uses platinum/tin catalysts supported on silica, graphite, calcium silicate, or aluminosilicate; under conditions of around 250°C, this catalyst facilitates the selective conversion of acetic acid and hydrogen into ethanol. In March 2012, Serranus Corporation applied this technology in the Nanjing Chemical Industrial Park to build a plant with an annual production capacity of 275,000 tons of ethanol and 51,000 tons of ethyl acetate as a by-product; the total investment in this project was 180 million US dollars. The production facility is now in operation. In April 2012, Henan Shunda Chemical Technology Co., Ltd. collaborated with the Southwest Chemical Research and Design Institute to build a plant in Zhumadian, Henan, capable of producing 200,000 tons per year of ethanol via the hydrogenation of acetate esters, using the company’s existing acetic acid production facility with an annual capacity of 360,000 tons. At present, the construction progress of this project is slow. Route 3: Dimethyl ether is carbonylated and then hydrogenated to produce ethanol. Carbon monoxide and hydrogen react under the action of a catalyst to form methanol; methanol is dehydrated to yield dimethyl ether, which is then carbonylated to produce methyl acetate. Methyl acetate is finally hydrogenated to give ethanol. The Dalian Institute of Chemical Physics, Chinese Academy of Sciences, uses non-precious metal carbonylation catalysts to implement this route. In 2013, Shaanxi Yanchang Petroleum (Group) Co., Ltd. and the Dalian Institute of Chemical Physics launched an industrial demonstration project for the production of ethanol from syngas at a capacity of 100,000 tons per year. On January 11, 2017, qualified anhydrous ethanol was produced, with a purity of 99.71%; all key performance indicators met the design specifications. Route 4: Production of ethanol from ethylene – Ethylene is obtained from coal as a raw material; this technology is already widely used in China, so no further details are provided here. As for the production of ethanol from ethylene, the United States first adopted the sulfuric acid hydration method in 1930, and later developed the direct hydration method. The production process via sulfuric acid hydration is carried out in two steps. The first step is the reaction of ethylene with sulfuric acid to produce alkyl sulfates, and the second step is the hydrolysis of alkyl sulfates to produce ethanol. This method requires the use of special evaporators for vacuum evaporation, which results in high costs, severe pollution, numerous side reactions, and high raw material consumption. The direct hydration method is a gas-phase process; the process conditions require a reaction temperature of around 250 degrees Celsius, a pressure of 7.0 megapascals, and it is carried out using a silicic acid diatomite catalyst. Under these process conditions, the one-pass conversion rate of ethylene is around 5%, the selectivity ranges from 94% to 95%, and environmental pollution associated with the process is relatively low. United Carbon Corporation in the United States uses this process to produce ethanol, with the workflow divided into three stages: synthesis, purification, and dehydration. Looking at the above four process routes, although the first three have received attention and have a certain foundation in industrial testing, in terms of actual operation, they are still some way away from being mature industrial technologies. It is difficult for them to reach the designed annual output levels within 3 to 5 years of commissioning, while ensuring safe, stable, long-term, full-load operation. As for the last process route, it is feasible from the perspective of coal chemistry; not only are there mature experiences from earlier industrial applications, but also all the units involved in the ethylene hydration step following coal-to-ethylene production are already developed, though there are few examples of such industrial combinations. If coal chemical enterprises wish to achieve the industrialization of ethanol production from coal, they must pay special attention to the selection of process routes. In terms of production costs, when producing ethanol from coal, theoretically 2,919 cubic meters of syngas (carbon monoxide:hydrogen) in a 1:2 ratio are required to produce 1 ton of ethanol. The actual consumption rate for producing low-carbon alcohols using the aforementioned process is approximately 3,500 standard cubic meters; it is estimated that the cost of coal-based ethanol and low-carbon alcohols will be around 4,500 to 5,000 yuan per ton. At present, China mainly uses traditional grain fermentation methods to produce ethanol, with a cost of over 5,000 yuan per ton. At present, cellulose ethanol in China is still in the pilot production stage, with a cost of over 7,000 yuan per ton. It can be said that under the current circumstances, coal-based ethanol still has an advantage in terms of cost competitiveness. However, whether coal-based ethanol can be industrialized and scaled up at present is inseparable from **policies aimed at promoting fuel ethanol. Coal chemical enterprises should pay special attention to the fact that the overall national demand for ethanol produced from coal is in the range of a few million tons; meanwhile, coastal areas import ethane to produce ethylene, and may also produce some ethanol for local use. Therefore, the large-scale development of ethanol produced from coal should not be pursued recklessly; especially when industrial technologies are not yet fully mature, it is inappropriate to build plants with capacities of hundreds of thousands or even millions of tons, in an attempt to dominate the national market right away. For coal chemical enterprises, carrying out capacity-expansion upgrades by constructing 100,000-ton-scale side lines on existing facilities and selling the products locally is the best option for developing coal-based ethanol, as it enables economic viability, efficiency, and rapid development. Especially for enterprises that already produce syngas, methanol, acetic acid, dimethyl ether, coal-based ethylene, coal-based oil, etc. (i.e., those that have syngas or produce a small amount of ethylene as a by-product), installing a side-stream unit after the existing plants to produce ethanol represents a viable option for diversifying their product portfolio, particularly in light of the existing or upcoming overcapacity.