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Current Application Status, Economic Analysis, and Future Development Trends of Major Coal-to-Olefins Technologies Author/Source: Beijing Petrochemical Engineering Co., Ltd. Date: November 26, 2021 Clicks: 15 Driven by China’s characteristics of abundant coal, limited oil, and scarce gas as far as fossil resources are concerned, as well as the continuous strong demand for downstream petrochemical products, China’s modern coal chemical industry has developed rapidly and has become an important supplement to the petrochemical industry. As one of the key components of modern coal chemical industry, coal-based olefins have seen rapid technological advancement and industrial development in recent years. Their market share continues to expand, making them the sector within modern coal chemistry that offers the best economic returns and the fastest growth in production capacity. In 2019, China’s dependence on foreign oil reached 72%, drawing great attention within the industry to energy security issues. In this context, continuously promoting technological advancements and the high-quality development of the coal-to-olefins industry is of great significance for conserving precious oil resources, meeting the growing demand for petrochemical products, and ensuring **energy security**. 1 Current Development Status of Coal-to-Olefins Technology. Coal-to-olefins is one of the important process technologies for producing olefins in China. It uses coal as raw material; through processes such as gasification, conversion, purification, and synthesis, methanol is first produced, which is then used to manufacture olefins (ethylene + propylene), thereby yielding downstream products such as polyolefins (polyethylene, polypropylene). Coal-to-methanol production and the polymerization of olefins to produce polyolefins are both traditional and mature technologies, while methanol-to-olefins conversion is a new technology that has been developed in recent years and represents the key technical aspect of coal-to-olefins processes. The basic reaction process for producing olefins from methanol involves methanol first dehydrating to dimethyl ether (DME), which is then dehydrated to form low-carbon olefins such as ethylene, propylene, and butylene. A small amount of these low-carbon olefins undergo reactions such as polycondensation, cyclization, alkylation, and hydrogen transfer to produce saturated hydrocarbons, aromatics, and higher-carbon olefins. Currently, the main technologies for producing olefins from methanol are MTO and MTP. MTO technology is a process that converts methanol into a mixture of ethylene and propylene; in addition to ethylene and propylene, it also produces by-products such as butylene ； The MTP technology is a process that primarily converts methanol into propylene. Besides propylene, it also produces products such as ethylene, liquefied petroleum gas (LPG), and naphtha. Among these two technologies, enterprises with coal resources can use coal as a raw material to produce methanol via syngas, and then use methanol to produce olefins ； Enterprises lacking coal resources (such as those in coastal areas) can purchase methanol from external sources (e.g., imported methanol) to directly produce olefins. 1. Several typical methanol-to-olefins technologies. The representative methanol-to-olefins technologies currently in use include the UOP/Hydro MTO process developed jointly by UOP (an American company) and Hydro (a Norwegian company), the MTP process developed by Germany’s Lurgi company, the DMTO process developed by the Dalian Institute of Chemical Physics under the Chinese Academy of Sciences, the SMTO process developed by the Shanghai Research Institute of Petrochemical Technology affiliated with Sinopec, the SHMTO process developed by Shenhua Group, and the circulating fluidized bed methanol-to-propylene (FMTP) process developed by Tsinghua University. (1) UOP/Hydro MTO process: This process uses crude methanol or product-grade methanol as raw materials to produce polymeric-grade ethylene/propylene. It employs a fluidized-bed reactor, with a reaction temperature of 400–500°C and a pressure of 0.1–0.3 MPa. The selectivity for ethylene+propylene can reach 80%, and the molar ratio of ethylene to propylene can be between 0.75 and 1.50 ； Its catalyst model is MTO-100, and its main component is SAPO-34 (silicon, aluminum, phosphorus). To improve the yields of ethylene and propylene in the product stream, UOP has developed a technology that couples the methanol-to-olefins process with the C4 and C5 olefins cracking process (OCP). This technology can achieve a diolefin (ethylene + propylene) selectivity of up to 85%–90%, and the ethylene/propylene ratio can be adjusted within a wide range. In 2008, UOP collaborated with Total to establish an integrated demonstration project for methanol-to-olefins in Ferrière, Belgium, where the MTO and OCP processes were combined. The project had a methanol processing capacity of 10 tons per day, thereby verifying the reliability of its integrated process flow and its scalability to an industrial scale of millions of tons. The specific process flow diagram is shown in the literature. In 2011, Huisheng (Nanjing) Clean Energy Co., Ltd. received authorization from UOP to build an industrial methanol-to-olefins plant with a production capacity of 295,000 tons per year. The plant was successfully commissioned for the first time in September 2013, producing qualified products. Subsequently, UOP authorized the construction of four methanol-to-olefins projects: Shandong Yangmei Hengtong Chemical Co., Ltd. (300,000 tons/year), Jiutai Energy Corporation (600,000 tons/year), Jiangsu Sierbang Petrochemical Co., Ltd. (820,000 tons/year), and Jilin Caner Group Co., Ltd. (600,000 tons/year). The first two projects were put into operation in June 2015 and January 2019, respectively; the latter two projects are currently under construction. In January 2018, UOP’s MTO catalyst production plant in Zhangjiagang City, Jiangsu Province, was completed and put into operation. It will help meet the growing demand for MTO catalysts from coal-to-olefins plants in the Chinese market. (2) Lurgi MTP process: The German company Lurgi began developing the MTP process in 1996, using a zeolite-based modified ZSM-5 catalyst from Sudchemie of Germany; this catalyst exhibits high selectivity for low-carbon olefins ； In May 2004, the industrial demonstration test with a methanol treatment capacity of 360 kg/d was successful. The process consists of 3 fixed-bed reactors (2 in operation and 1 as a backup), with each reactor having 6 catalyst beds. In practice, however, two types of reactors are available: fixed-bed reactors (which produce only propylene) and fluidized-bed reactors (which can produce both ethylene and propylene). During the production process, the target product of the Lurgi MTP process is propylene. First, methanol undergoes dehydration to form dimethyl ether; subsequently, dimethyl ether, methanol, and water enter the first MTP reactor. The reaction takes place at 400–450°C and 0.13–0.16 MPa. The conversion rates of methanol and dimethyl ether exceed 98.99%. Propylene is the main product, while small amounts of ethylene, LPG, and gasoline are also produced as by-products ； Meanwhile, a second and third MTP reactor were set up to achieve a higher propylene yield (up to 71%). In December 2010, the 500,000-ton/year coal-based polypropylene project at Shenhua Ningmei, which utilized Lurgi’s MTP technology, achieved full operational capacity, and qualified polypropylene products were produced in April 2011 – marking the first time that the MTP technology was applied in China. In September 2011, China’s Datang Duolun 460,000-ton-per-year coal-based methanol to propylene project, utilizing Lurgi MTP technology, was completed and put into operation, and in March 2012 the first batch of high-quality polypropylene products were successfully produced. In August 2014, the second phase of Shenhua Ningmei’s 500,000-ton/year MTP project, which utilized Lurgi MTP technology, achieved full operational capacity across the entire process. Shenhua Ningmei holds a 15% patent licensing interest in the Lurgi MTP technology worldwide. Through independent technological innovation, it has achieved the domestic development and industrial application of MTP catalysts; to date, it has developed a second-generation MTP process catalyst based on low-cost, high-performance multi-porous ZSM-5 molecular sieves. (3) The DMTO process at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences. The Dalian Institute of Chemical Physics, Chinese Academy of Sciences (abbreviated as DICP) began research on the MTO process in the 1980s. In the early 1990s, it pioneered an innovative method internationally for producing lower olefins from syngas via dimethyl ether; this method is known as the SDTO process. This process consists of two reaction stages. In the first stage, syngas is converted into dimethyl ether with high selectivity over a bifunctional catalyst comprising metal and zeolite. In the second stage, dimethyl ether is transformed into light olefins such as ethylene and propylene with high selectivity over an SAPO-34 molecular sieve catalyst. Through further technological advancements, this process has been simplified to a direct conversion of syngas into olefins via methanol, utilizing an SAPO-34 molecular sieve catalyst. This catalytic conversion takes place in a dense-phase circulating fluidized bed reactor. The corresponding catalysts include the DO123 series (primarily producing ethylene) and the DO300 series (primarily producing propylene). In 2004, the Dalian Institute of Chemical Physics, Shaanxi Xinxing Coal Chemical Technology Development Co., Ltd., and Sinopec Luoyang Petrochemical Engineering Company collaborated to develop the complete set of industrial technologies for DMTO. An industrial test facility capable of producing tens of thousands of tons per year of olefins from methanol was built, and the industrial tests were completed in 2006. The methanol conversion rate was nearly 100%, while the selectivity for C=2–C=4 compounds was over 90%. In August 2010, the world’s first million-ton-scale industrial plant using the DMTO process was put into operation – the Shenhua Group’s coal-to-olefins project in Baotou, Inner Mongolia. The project includes a coal-based methanol plant with an annual capacity of 1.8 million tons, as well as a polyolefin (polyethylene, polypropylene) integrated petrochemical plant with an annual capacity of 600,000 tons. The methanol conversion rate is over 99.9%, while the selectivity for ethylene + propylene is above 80%; the products meet the specifications required for polymer-grade olefins. Based on the DMTO process, the Dalian Institute of Chemical Physics further developed the DMTO-Ⅱ process. This process adds recombination and cracking units for compounds above C4; that is, the C4 and higher components produced by the olefin separation unit are fed into a cracking reactor. The cracking reactor is of the fluidized bed type, and the catalyst used in the catalytic cracking unit is the same as that used in methanol conversion. Within the fluidized bed reactor, the catalytic cracking of C4+ components takes place, resulting in mixed hydrocarbon products primarily composed of ethylene and propylene. The resulting mixed hydrocarbon is mixed with the methanol conversion product gas and fed into a separation system for separation. By adding more cracking units, the yields of ethylene and propylene can be increased from 80% to around 85%, reducing the methanol consumption per ton of light olefins from 3 tons to 2.6–2.7 tons; meanwhile, the yield of dienes increases by 10% compared to the DMTO process. In this process, the same catalyst is used for both the C4+ conversion reaction and the methanol conversion reaction. Both the methanol conversion system and the C4+ conversion system employ a fluidized bed process, thereby enabling coupling between these two systems. In December 2014, the DMTO-Ⅱ industrial demonstration plant was successfully commissioned at Shaanxi Pucheng Clean Energy Chemical Co., Ltd., producing polymeric-grade propylene and ethylene. In addition, Gansu Pingliang Huahong Huijin Coal Chemical Co., Ltd. will also employ the DMTO-Ⅱ technology in its 700,000 tons per year olefin project. In recent years, DMTO technology has been put into industrial use and licensed for more than 20 plants in China, resulting in a total olefin production capacity of over 10 million tons per year. Building on the DMTO-II technology, the Dalian Institute of Chemical Physics is actively researching the DMTO-III technology. The goal is to increase the processing capacity of a single DMTO unit from the current level of 1.8 million tons per year to over 3 million tons per year, while ensuring that the single-pass methanol conversion rate and olefin selectivity remain at least as high as those achieved with the DMTO-II technology. In 2019, the institute completed the development of catalysts for the DMTO-III technology and the laboratory-scale pilot testing and scale-up of the reaction process. Currently, it is working on preparing a million-ton-scale process package. (4) Sinopec SMTO process: The Shanghai Research Institute of Petrochemical Technology at Sinopec began research and development on MTO technology in 2000. In 2007, the institute collaborated with China Petroleum & Chemical Engineering Construction Corporation to develop a complete set of SMTO technologies. Subsequently, a 100 t/d SMTO industrial pilot plant was built at Beijing Yanshan Petrochemical. This technology uses a self-developed SMTO-1 catalyst, achieving a methanol conversion rate of over 99.5%, a selectivity for ethylene + propylene of over 81%, and a selectivity for ethylene + propylene + butylene of over 91%. In 2008, the institute completed the development of an SMTO process package for an annual methanol feed of 1.8 million tons. In October 2011, the methanol-to-olefins demonstration project of Zhongyuan Petrochemical, which utilized the SMTO process, was successfully commissioned for the first time. The plant’s capacity was 600,000 tons per year of methanol processing, with the ability to produce 100,000 tons of polyethylene and 100,000 tons of polypropylene. In October 2011, the Zhongtian Hechuang coal-to-olefins deep coal processing demonstration project completed the entire production process, yielding qualified polyethylene and polypropylene. Located in Ordos, Inner Mongolia, the project utilizes GE’s coal slurry gasification technology as well as SMTO technology; it includes facilities for producing 3.6 million tons per year of methanol, 2×1.8 million tons per year of olefins from methanol, 670,000 tons per year of polyethylene, and 700,000 tons per year of polypropylene. It is currently the largest coal-to-olefins project in the world. In January 2017, the Zhongan United Coal-to-Chemicals Integration Project located in Huainan, Anhui, resumed operations. This project utilizes Sinopec’s single-nozzle dry powder coal gasifier (SE furnace) as well as SMTO technology, and is carried out in two phases; the first phase involves the construction of a facility capable of producing 1.7 million tons per year of coal-based methanol, along with converted olefins and derivative products. In addition, projects that utilize the SMTO process include those for coal-to-olefins in Hebi, Henan, with a capacity of 600,000 tons per year, and in Zhijin, Guizhou, also with a capacity of 600,000 tons per year. The results of the industrial application of SMTO technology show that its ethylene selectivity is 42.10%, propylene selectivity is 37.93%, the selectivity for C2–C4 compounds is 89.87%, the methanol conversion rate is 99.91%, the methanol consumption per ton of product is 2.92 t/t, and the coking rate is 1.74%. (5) Shenhua Group’s SHMTO process: In 2010, the world’s first large-scale industrial methanol-to-olefins plant (using DMTO technology) was successfully commissioned in Baotou under Shenhua Group’s ownership. Drawing on the extensive experience gained from the operational phase of this pilot plant, Shenhua Group developed a number of new processes and technologies, including the creation of a new type of MTO catalyst (SMC-1) as well as new MTO processes. In 2012, the new methanol-to-olefins catalyst SMC-1 was successfully developed and applied in the MTO plant in Baotou. In the same year, Shenhua Group applied for a patent for a device and method for converting methanol into low-carbon olefins, and completed the development of a new 1.8 million tons per year methanol-to-olefins (SHMTO) process package. In September 2012, the 1.8 million tons per year methanol-to-680,000 tons per year olefins project at Shenhua Ganchuanbao in Xinjiang, which utilized the SHMTO process, was successfully commissioned. The industrial operation of this facility showed an ethylene selectivity of 40.98%, a propylene selectivity of 39.38%, a C2–C4 selectivity of 90.58%, a methanol conversion rate of 99.70%, and a char formation rate of 2.15%. (6) Tsinghua University’s FMTP process: This is a fluidized-bed methanol-to-propylene process (referred to as the FMTP process) that was developed jointly by Tsinghua University, China National Chemical Engineering Group Corporation, and Huaihua Group. Industrial trials of this process were carried out in October 2009 at Huaihua Group in Anhui Province. It utilizes SAPO-18/34 molecular sieve catalysts and fluidized-bed reactors; the methanol feed rate is 4250 kg/h, with a methanol conversion rate of 99.9%. The ratio of propylene to ethylene in the products is 1.18:1, while the selectivity for ethylene plus propylene reaches 70.6%. The FMTP process is generally an improvement over the MTP process, allowing the propylene/ethylene ratio to be adjusted from 1.2∶1 to 1∶0 (pure propylene output). Using this technology to produce olefin products based on propylene, the overall yield of dienes (ethylene + propylene) can reach 88%, with a methanol consumption of 2.62 t per ton of dienes. By utilizing FMTP technology, the Huating Coal Industry Group in Pingliang, Gansu is constructing China’s first fluidized-bed methanol-to-propylene plant. This facility will consume 600,000 tons of methanol per year, producing 160,000 tons of polypropylene, 19,000 tons of liquefied gas, 21,000 tons of propane, 14,000 tons of gasoline, 8,000 tons of fuel gas, and 28,000 tons of methyl tert-butyl ether (MTBE) per year. It is expected to be completed and put into operation in 2021. 2 Comparative analysis of the main technical indicators of several typical processes. In a general summary analysis, Table 1 shows the comparison of the main technical indicators among several typical methanol-to-olefins processes. As can be seen from Table 1, except that the MTP process of Lurgi uses a fixed-bed reactor and ZSM-5 molecular sieve catalyst, the other technologies all use fluidized-bed reactors and SAPO-34 catalysts. In terms of technical indicators, the DMTO-II technology developed by Dalian Institute of Chemical Physics achieves the highest yield of dienes (95%), followed by the DMTO technology (86%) ； The DMTO-II technology has the lowest methanol consumption (2.67 t/t), followed by Sinopec’s SMTO technology (2.82 t/t) ； The methanol conversion rate for several technologies exceeds 99%. After a comprehensive comparison of process characteristics and technical parameters, the DMTO technology currently enjoys the highest level of recognition for methanol-to-olefins production in China. The UOP technology only has certain advantages when combined with an OCP unit. The SMTO technology is currently available only to companies under Sinopec Group, and no technical transfers have been made to external parties yet. There is limited publicly available information regarding the SHMTO technology. Therefore, the MTO technology that will hold a competitive advantage in the future is likely to be the domestic process. Based on the actual application of these various typical processes, it can be seen that the process technologies used in coal-to-olefins projects in China are quite diverse, with both domestic and foreign technologies being employed. Overall, however, the DMTO technology developed by the Dalian Institute of Chemical Physics is the most widely used. According to incomplete statistics, as of now this technology has been licensed for 25 industrial plants, resulting in an olefin production capacity of 14.58 million tons per year. Of these, 14 plants are already in operation, with an olefin production capacity of 7.76 million tons per year, accounting for a market share of 67.9%. There are 8 sets of industrial licenses for the UOP/Hydro MTO process, with a production capacity of 3.52 million tons per year ； Six sets have been put into operation, with a production capacity of 2.89 million tons per year. Six sets of industrial licenses for Sinopec’s SMTO process have been granted, with a production capacity of 3.37 million tons per year ； Three sets have been put into operation, with a production capacity of 2.27 million tons per year. Including the Shenhua SHMTO process in the 1.8 million tons per year methanol-to-680,000 tons per year olefins project in Ganquanbao, Xinjiang, there are currently 24 coal (methanol)-based olefins production units in China, with a total capacity of 13.6 million tons per year. According to the \"2020 Capacity Warning Report on Key Petrochemical Products\" issued by the China Petroleum and Chemical Industry Federation, in 2019 China’s total production capacity for ethylene and propylene was 69.63 million tons per year (29.02 million tons per year for ethylene and 40.61 million tons per year for propylene). It is estimated that the capacity for producing olefins from coal (methanol) accounted for 19.5% of China’s total olefin production capacity, highlighting its growing importance in China’s olefin manufacturing sector. 2 Analysis of Production Costs and Economic Viability of Coal/Methanol-Based Olefin Production Technology 1 Analysis of Plant Scale, Investment, and Production Costs The typical scale for a methanol-based olefin production plant is 3.6 million tons per year of methanol feed, with an output of 1.2 million tons per year of polyolefins (polyethylene + polypropylene). For example, Zhongtian Hechuang has a coal-to-methanol production capacity of 3.6 million tons per year (including 2 units with a capacity of 1.8 million tons each), as well as a methanol-to-olefins production capacity of 1.37 million tons per year. Its polyolefin production facilities include 2 units for producing polypropylene at a capacity of 350,000 tons per unit, 1 unit for producing full-density polyethylene at a capacity of 300,000 tons per year, 1 unit for producing high-pressure LDPE via the tubular process at a capacity of 250,000 tons per year, and 1 unit for producing high-pressure LDPE via the batch process at a capacity of 120,000 tons per year. The capacity of a single production line is 1.8 million tons/year for methanol and 600,000 tons/year for polyolefins (polyethylene + polypropylene). Examples include Shenhua Baotou Coal-to-Methanol Plant (1.8 million tons/year) and its 600,000-ton/year methanol-to-olefins facility, which includes one 300,000-ton/year polyethylene unit and one 300,000-ton/year polypropylene unit. Generally, the investment for a single production line in a coal-to-olefins plant is around 15 billion yuan; if ethylene and propylene polymerization units are included, the total investment amounts to about 21 billion yuan. The cost components of olefins produced from coal and those produced from purchased methanol are shown in Figure 1 and Figure 2, respectively. As can be seen from Figure 1, in the cost structure of coal-based olefins, the cost of raw coal accounts for only 22% of the total cost, while equipment depreciation and financial costs together make up 49%. As can be seen from Figure 2, in the cost structure of producing olefins directly from purchased methanol, equipment depreciation and financial expenses account for only 9%, while the cost of the raw material methanol makes up as much as 74%. It can be seen that the main factors affecting the production cost of coal-based olefins are equipment depreciation and financial expenses; changes in coal prices are only a secondary factor affecting production costs. This is because the production process for coal-based olefins is lengthy and requires high initial investments, resulting in high equipment depreciation costs ； In the direct conversion of methanol into olefins, the production process is short and the initial investment is low; therefore, the production cost mainly depends on fluctuations in the price of the raw material methanol, while the depreciation cost of the equipment accounts for a small proportion of the total cost. 2 Technical and economic analysis of coal/methanol-based olefin production (1) Economics of coal-based olefin production: The coal-based olefin production process requires approximately 7 tons of coal and about 22 tons of fresh water to produce 1 ton of olefins. Based on Ordos raw coal (5500 cal/kg at the mine entrance, with a price of 300 yuan per ton), the production cost of olefins in a typical coal-to-olefins plant ranges from 6300 to 6800 yuan per ton (including taxes). Among these costs, variable expenses such as raw coal, fuel coal, water consumption, and catalyst usage account for about 40% of the total cost; financial expenses and equipment depreciation account for 45% to 50%; while labor costs, administrative expenses, and transportation costs account for 10% to 15%. Given the current market prices of polyolefin products (as of early January 2020, the average spot price of polyethylene in the East China region was around 8,200 yuan per ton, while the average price of polypropylene was around 9,500 yuan per ton), coal-based olefins offer a favorable level of profitability. Since the price of olefins fluctuates with crude oil prices, the higher the oil price, the higher the price of olefins. According to calculations by the author of this paper, coal-to-olefins projects generate positive cash flow when the oil price is $30 per barrel; they become profitable at $40 per barrel, and can achieve satisfactory profitability at $50 per barrel ； At oil prices of $65–75 per barrel, the cost of coal-based olefins is comparable to that of naphtha-based olefins, resulting in good profit margins ； When oil prices are above $85 per barrel, the after-tax profit from coal-based olefins can reach 1,865 yuan per ton, which meets the requirement of an internal rate of return of over 12% for new facilities, indicating strong profitability. It is worth noting that in the second half of 2014, international crude oil prices plummeted. The low oil prices during the subsequent two to three years put tremendous pressure on coal chemical enterprises, including those engaged in coal-to-olefins production. Over the past two years, international oil prices have stabilized and risen, generally fluctuating around $50–$65 per barrel. As a result, coal-to-olefins projects have generally achieved decent profitability. However, on March 6, 2020, due to the breakdown of negotiations within the OPEC+ production cut alliance, coupled with the impact of the novel coronavirus pandemic that erupted in late January, international crude oil prices experienced another sharp decline. On April 20, the price of WTI crude oil futures closed at -$37.63 per barrel, marking the first occurrence of negative oil prices in history ； After entering May, the OPEC+ production cut agreement took effect, and oil prices began to rise gradually, remaining at a low level of around $40 per barrel in early June. It is highly likely that, as the global COVID-19 situation gradually improves by the end of 2020, international crude oil prices will rise back to around $50 per barrel. Under such circumstances, coal-to-olefins production is expected to return to a profitable phase. (2) Economics of methanol-to-olefins production: In the process of producing olefins from purchased methanol, approximately 2.7 tons of methanol are consumed per ton of olefins produced, with about 3 tons of water being used per ton as well. In the cost structure of externally purchased methanol-to-olefins production, the cost of methanol as a raw material accounts for over 70%. Fluctuations in this cost are closely related to changes in crude oil prices. Rising oil prices increase the cost of producing olefins from imported methanol, resulting in reduced profits. According to the calculations by the author of this article, at low crude oil prices (30 dollars per barrel), the production cost of olefins in typical methanol-based olefin production plants is comparable to the cost of olefins produced from coal (around 6,000 yuan per ton), but it is higher than the cost of olefins produced from naphtha (around 4,500 yuan per ton) ； At an oil price of $50 per barrel, the cost of producing olefins from externally purchased methanol is approximately 7,500 yuan per ton. This is higher than the cost of coal-based olefin production (about 7,000 yuan per ton) and naphtha-based olefin production (about 6,000 yuan per ton) ； When oil prices rise to $70 per barrel, the cost of producing olefins from imported methanol increases to 8,500 yuan per ton; at such oil prices, the cost of producing olefins from coal is comparable to that of producing them from naphtha (around 7,000 yuan per ton) ； When oil prices rise to $100 per barrel, the cost of producing olefins from externally sourced methanol increases to around 9,500 yuan per ton, which is comparable to the cost of producing olefins from naphtha. This figure is about 26% higher than the cost of producing olefins from coal (7,500 yuan per ton). Clearly, whether methanol-to-olefins production via purchased methanol can be profitable depends crucially on the availability of a stable and low-cost source of methanol. 3 Analysis of the Development Trends of Coal-to-Olefins Technology After years of rapid development, coal-to-olefins technology has now been fully industrialized. However, there is still room for further improvement in its technical level. In the future, the main development trends of this technology will include the following aspects. (1) Enhance the level of technological self-reliance throughout the entire process and promptly break free from foreign technological constraints. According to the “Regulatory Conditions for the Coal-to-Olefins Industry” released by the Ministry of Industry and Information Technology in August 2015, newly built, renovated, or expanded coal-to-olefins projects are encouraged to adopt a series of advanced and reliable process technologies with independent Chinese intellectual property rights, including clean coal gasification, air separation, purification, sulfur recovery, methanol synthesis, methanol-to-olefins conversion, and olefin separation. Its key technical indicators shall meet the following requirements: The gasification process should employ pressurized entrained-flow gasification technology; the carbon conversion rate must be no less than 98%, and the cold gas efficiency must be no less than 70% ； The oxygen production capacity of a single air separation unit shall be no less than 6×10^4 m³/h ； In the purification process, the loss rate of “CO+H2” shall not exceed 0.5% ； In the sulfur recovery process, the sulfur recovery rate is not less than 99.5% ； In the methanol synthesis process, the consumption of fresh gas per 1 ton of methanol is no more than 2,250 m³ ； In the MTO process, no more than 3.06 tons of methanol are required to produce 1 ton of olefins, while in the MTP process, no more than 3.5 tons of methanol are needed to produce 1 ton of propylene ； In the olefin separation process, the olefin recovery rate is not less than 99.5%. Based on the technologies currently used in the entire coal-to-olefins production process, the methanol-to-olefins stage makes use of domestically developed DMTO technology. For coal gasification, domestic multi-nozzle coal slurry gasification technology and pressurized pulverized coal gasification technology are employed; in some cases, the coal slurry gasification technology developed by the American company GE is used as well. The purification of raw gas is carried out using the low-temperature methanol washing process provided by the German company Linde. The methanol synthesis stage utilizes technology from the British company Davy. Olefin separation is achieved through technologies provided by the American companies ABB Lummus and Univation. HDPE is produced using Ineos’ slurry loop process, while LLDPE is manufactured via Univation’s gas-phase fluidized bed polymerization process. Polypropylene is produced either using technology from the American company Dow or Ineos’ gas-phase polymerization process. Thus, it can be seen that the degree of self-reliance in the entire process technology for coal-to-olefins in China is not very high. The integrity of the technology package and its key equipment remain major bottlenecks; therefore, efforts must be stepped up in the research, development, and application of such technology packages. (2) Developing new catalysts to further improve the technology level of methanol-to-olefins production. In recent years, several large-scale integrated refining and chemical projects in China, such as those operated by Zhejiang Petrochemical, Hengli Petrochemical, and Shenghong Petrochemical, as well as those of China National Petroleum Corporation and Sinopec, have been put into operation. Over the next 3 to 5 years, the production capacity of additional large-scale integrated refining and chemical projects will also be gradually brought online. According to the \"2020 Capacity Warning Report for Key Chemical Products\" issued by the China Petroleum and Chemical Industry Federation, in 2019 the production capacity of ethylene was set to increase by 3.52 million tons per year, bringing the total capacity to 29.02 million tons per year. It is expected that by 2025, China’s total ethylene production capacity will exceed 50 million tons per year ； In 2019, new propylene production capacity added amounted to approximately 4.41 million tons per year. The total capacity is expected to exceed 40.61 million tons per year. It is anticipated that by 2025, the overall propylene production capacity will reach 56 million tons per year ； If the 45 announced propane dehydrogenation projects under construction or planned for construction are completed as scheduled, the total propylene production capacity will exceed 62 million tons per year. Against the backdrop of rapid growth in China’s total olefin production capacity, coal-based olefin manufacturers undoubtedly face severe challenges in terms of product marketing and economic profitability. As the core technology for producing olefins from coal, methanol-to-olefins still has room for further improvement. In the future, the focus will be on developing a new generation of MTO catalysts that can reduce the coking rate of these catalysts, increase the yields of propylene and ethylene, and allow for flexible adjustment of the ratio between propylene and ethylene, thereby enhancing resilience to risks. To address the prominent issues associated with MTP technology, such as high energy consumption and low propylene yield, new MTP catalysts have been developed to reduce the methanol consumption per ton of olefins. At the same time, the technical process flow has been optimized to lower energy consumption, and by-depth processing of by-products such as C4 and C5 is carried out to improve economic efficiency. (3) Scientifically arrange the product structure of projects to enhance product differentiation and high-end characteristics. Although China’s coal-to-olefins industry has developed rapidly, its product structure is single and homogenization is severe, resulting in fierce market competition ； At the same time, with the introduction of strict environmental protection regulations in China in 2015, several planned coal-based olefin projects faced rejections in their environmental impact assessments. In the future, coal-based olefin projects will require more rational analysis, improved planning, and differentiated products. At present, there is still a significant gap in the production capacity of ethylene and propylene in our country. The focus remains on increasing investment in research and development; by improving relevant processing technologies, it is possible to achieve greater differentiation and a higher quality level for these products. With international crude oil prices remaining at a moderate level (around $50 per barrel), coal-based olefins are economically viable. Coupled with strong demand from the polyolefin market, the development potential of coal-based olefins cannot be underestimated. The future direction of development lies in advancing research and development of new products, striving to create high-end, differentiated, and functional products in order to increase their added value. This includes developing high-end polyolefin products such as metallocene polyolefin elastomers, ultra-high molecular weight polyethylene, and bimodal polyolefins. It also involves increasing the proportion of high-end specialty materials used in pipes, medical applications, automotive components, electronic and electrical films, and gas pipelines, thereby boosting the added value of these products. In addition to producing polyolefins, ethylene oxide/propane oxide, butyl octyl alcohol, acrylic acids and esters, and acrylonitrile should also be produced, making good use of by-products such as C4, C5, and LPG ； In addition, intelligent and information-based methods are employed to improve the level of operational management, reduce resource waste in maintenance processes, and lower production costs. (4) Transition of production technologies to environmentally friendly ones to achieve zero pollutant emissions. Based on an analysis of the current situation regarding coal/water resource supply and clean production in the coal chemical industry, coal-to-olefins production faces pressures related to water resource supply, clean production, and carbon emissions. Firstly, coal-to-olefins plants must be built in areas rich in coal resources (about 8 tons of coal are required to produce 1 ton of olefins), in order to reduce the costs associated with transporting coal ； At the same time, the location of the facility must have abundant water resources (the coal-to-olefins technology requires approximately 20 tons of water to produce 1 ton of olefins), which runs counter to the “inverse distribution” pattern of coal and water resources in China. Secondly, coal-to-olefins processes generate large amounts of CO2 emissions; 75% of the carbon in coal is converted into CO2 and released. A coal-to-olefins plant with an annual capacity of 600,000 tons emits around 6 million tons of CO2 per year. China has already begun carbon trading, and carbon taxes will be imposed gradually on companies with high carbon emissions. As one of the main targets for such taxes, the coal chemical industry will undoubtedly face pressure related to carbon emissions. Third, coal-to-olefins processes generate large amounts of “three wastes”. The wastewater mainly consists of organic wastewater and saline wastewater. The waste residues include fly ash, coal gangue, boiler ash and slag, gasifier slag, desulfurization gypsum, etc. The main harmful substances in the exhaust gases are SO2, H2S, NOx, soot, hydrocarbons, and other organic compounds. With China’s growing emphasis on environmental protection and increasingly stringent environmental policies, the clean production of coal-to-olefins also faces tremendous pressure. Given the current development status and trends, coal-based olefins production will place greater emphasis on the use of advanced water-saving technologies as well as techniques for treating, reusing wastewater, waste gas, and waste residues, in order to further reduce water consumption and achieve \"zero emissions\" of pollutants. At the same time, efforts will be made to develop and utilize carbon capture, storage, and utilization (CCUS) technologies in order to reduce carbon emissions, thereby lowering the production costs of olefins while achieving clean production. Currently, there are 12 CCUS projects under construction or already operational in China. Some large coal and power companies are undertaking efforts to develop CCUS technologies and carry out demonstration projects; examples include Sinopec’s 1 million tons per year CCUS project at the Shengli Oilfield coal-fired power plant, as well as Shenhua Group’s 100,000 tons per year CCS demonstration project in Ordos. It is worth noting that for the vast majority of modern coal chemical projects currently in operation in China, significant progress has been made in terms of wastewater and waste residue treatment and reuse technologies, enabling near \"zero emissions\". In the future, it will be necessary to continue to advance technological innovation, develop technologies for utilizing CO2, reduce operating costs of these facilities, and improve the economic viability of coal-based olefin production projects. (5) The technology for producing olefins directly from coal via syngas has clear advantages, and further research and development efforts are needed. In China, the coal-to-olefins projects that are currently in operation all first convert syngas into methanol, and then use MTO or MTP technologies to produce olefins from methanol. This technological route is mature and has been widely applied on an industrial scale; however, compared with the technology for producing olefins directly from coal-based syngas, it has drawbacks such as greater technical complexity, longer process flows, and lower conversion efficiency. In September 2019, the Dalian Institute of Chemical Physics, in collaboration with Shaanxi Yanchang Petroleum (Group), completed an industrial pilot test for the technology of directly producing low-carbon olefins from coal via syngas. This technological approach eliminates the traditional hydrogen production process based on water-gas shift, which is characterized by high water consumption and high energy use, as well as the conversion processes of intermediate products such as methanol and dimethyl ether. It establishes, in principle, a new pathway for the one-step conversion of coal into syngas with low water consumption (no water circulation in the reaction, and no wastewater generation). This new process features a short operation cycle, low water and energy consumption, as well as clear technical advantages. If industrial trials prove successful in the future, it is expected to become a new generation of alternative process to existing coal-to-olefins technologies. It is necessary to continue investing in research and development in order to achieve industrial application at an early date. 4 Conclusion: In the face of China’s growing energy security challenges stemming from its increasing dependence on imported oil and gas, as well as the rising domestic demand for petrochemical products, the development of coal-based olefins serves as an important supplement to petroleum-derived olefins. Through the joint efforts of coal chemical industry researchers and professionals in China, the technology for producing olefins from coal has become mature overall. China has now emerged as a leader in the world in terms of technologies for producing olefins from coal and methanol. It is an undeniable fact that this technology is being widely applied on an industrial scale in China, and it represents the modern coal chemical sector with the best profitability and greatest potential for development. However, there is still room for further improvement in coal-to-olefins technology. In particular, it is necessary to accelerate technological innovation in order to develop integrated technologies for the entire coal-to-olefins process that possess independent intellectual property rights. At the same time, it is important to plan for downstream products and develop new ones, continuously reducing energy consumption, water usage, coal consumption, and CO2 emissions. Proper treatment and recycling of waste materials must also be ensured, and research and development in CO2 storage and utilization techniques should be accelerated, so as to promote the cleaner and more sustainable development of coal-to-olefins production. Of interest to the petrochemical industry is the rapid growth in China’s coal-based olefin production capacity in recent years, which is having an increasing impact on the petroleum olefin market. In the future, competition between petroleum olefins and coal-based olefins will intensify. Therefore, it is necessary to take into account the characteristics of this industry, leverage the advantages of both the petroleum chemical and coal chemical sectors, accelerate technological innovation and product structure adjustment, strive for a more diversified and high-end product portfolio, and promote complementary strengths between these two sectors in order to drive high-quality development of China’s chemical industry.