Coal-to-aromatics: Born out of time or naturally gifted?

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Coal-to-aromatics: Born out of time or naturally gifted? Author/Source: Huahua Network Coal Chemicals, Chen Jijun; Date: 2018-02-06; Clicks: 48. Affected by factors such as low oil prices, the competitiveness of several modern coal chemical industries that have already been industrialized has significantly declined. Among them, coal-to-oil and coal-to-natural gas operations are both suffering from industry-wide losses ； Coal-based ethylene glycol can only generate modest profits ； Although coal-based olefins operate with good profitability, their profit margins have been significantly compressed, and there is a risk of overcapacity leading to further declines in profits. Under these circumstances, what are the prospects for coal-derived aromatics, which have not yet been put into industrial use? Can it withstand the impact of low oil prices? How should it develop in the future? With these issues of concern within the industry, the reporter conducted research and interviews. The promotion of advanced technologies has met with little enthusiasm. On December 7, 2017, the basic design for the project undertaken by Shaanxi Coal and Chemical Industry Shenmu Fatty Oil Energy Technology Co., Ltd.—a facility capable of producing 500,000 tons per year of aromatic hydrocarbons, aviation kerosene, light white oil, and naphthenic-based base oils through the hydrogenation of the full range of coal tar fractions—was approved following a review. The total investment in this project is 2.493 billion yuan, and the products include lubricating oils, aromatics, sulfur, etc. This is another significant exploration and practice in China’s coal-to-aromatics sector. In fact, after more than 10 years of intensive research, the coal chemical industry has developed a number of new technologies for producing aromatics from coal, including hydrogenation of high-temperature coal tar to produce aromatics, hydrogenation of medium and low-temperature coal tar to produce aromatics, production of mixed aromatics from methanol in a fixed-bed reactor (also known as methanol-to-gasoline), production of aromatics from methanol in a fluidized-bed reactor, production of aromatics from methanol and toluene in a fixed-bed reactor, co-production of p-xylene and low-carbon olefins from toluene and methanol in a fluidized-bed reactor, and selective alkylation of benzene and methanol to produce p-xylene. Moreover, aside from the technologies for producing aromatics via coal tar hydrogenation and gasoline from methanol which are on par with international standards, the rest of the technologies have reached international leading levels. Among them, the technology for producing aromatics from coal via a methanol fluidized bed, independently developed by Wei Fei’s team at Tsinghua University, is capable of simultaneously achieving methanol aromatization, light hydrocarbon aromatization, and benzene/toluene methanol alkylation. This technology also includes specialized catalysts for the production of aromatics from methanol in fluidized beds, which possess properties such as resistance to metal sintering, as well as special equipment such as two-stage internal component circulating fluidized bed and two-stage component turbulent fluidized bed regenerators. The ability to obtain the target product, aromatics, using methanol as the sole raw material represents a milestone in the history of the development of aromatics worldwide. The entire process is as follows: coal (natural gas, coke oven gas, refinery dry gas) → methanol → dehydration → dimethyl ether → low-carbon olefins → oligomerization and cyclization reactions → mixed aromatics → aromatic complexing unit → p-xylene. The methanol conversion rate throughout the process is as high as 99.99%, with the content of \"triphenyl\" in the product exceeding 85% and the content of p-xylene exceeding 50%. This technological process was successful in 2011; between 2011 and 2013, an industrial pilot plant with a capacity of 30,000 tons per year was built and put into operation, and a process package with a capacity of 600,000 tons per year was successfully developed. After completing a pilot-scale production of 5,000 tons per year, the fixed-bed toluene-methanol methylation technology for producing p-xylene, developed by Sinopec Shanghai Research Institute of Chemical Industry, was implemented on a 200,000 tons per year toluene isomerization unit at Sinopec Yangzi Petrochemical Co., Ltd. at the end of 2012. This marked the first industrial application of this technology for producing p-xylene from toluene-methanol on a global scale. The fluidized-bed toluene-methanol process for producing p-xylene along with low-carbon olefins, developed by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, enables the high-selective production of p-xylene as well as low-carbon olefins such as ethylene and propylene in a single reaction system using one catalyst only, thus pioneering a non-naphtha-based route for the fluidized-bed toluene-methanol production of p-xylene. The new technologies developed by Shaanxi Coal Chemical Technology Engineering Center Co., Ltd. for producing p-xylene from toluene and methanol while simultaneously generating low-carbon olefins, as well as for the selective alkylation of benzene and methanol to produce p-xylene, are referred to in the industry as the second-generation technologies for producing p-xylene from toluene and methanol with low-carbon olefins as a by-product. These technologies not only broaden the sources of raw materials available for p-xylene production and reduce the stringent requirements previously imposed on such raw materials, but also increase the toluene conversion rate by more than twice compared to the technology developed by the Dalian Institute of Chemical Physics under the Chinese Academy of Sciences. This technology can flexibly adjust the production volumes of p-xylene and olefins according to market demands, thereby maximizing project profits. Regrettably, the pace of industrial adoption of these internationally leading coal-to-aromatics production technologies, all of which have been validated through pilot-scale testing, is extremely slow; in fact, it can be said that none of these technologies have yet been put into practical use. Take the fluidized-bed methanol-to-aromatics technology, which is highly anticipated by the industry, as an example. In March 2011, the world’s first million-ton-class demonstration project, funded and constructed by China Huaneng Group, was launched; yet to this day, the project is still in the preliminary stages and no actual construction work has begun ； The fixed-bed toluene-methanol methylation technology for the production of p-xylene, developed by Sinopec Shanghai Research Institute of Chemical Technology, was integrated into a 200,000-ton/year toluene selective disproportionation unit at Yangzi Petrochemical as early as the end of 2012; however, the unit only achieved stable operation in March 2015, and to date no license has been granted for a second such unit ； The technology developed by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, for producing p-xylene from toluene and methanol while generating low-carbon olefins has not yet been put into industrial use ； The path toward industrial application of the new technology developed by Shaanxi Coal Chemical Technology Engineering Center Co., Ltd. – which involves using toluene and methanol to produce p-xylene along with low-carbon olefins, as well as the technology for producing p-xylene through selective alkylation of benzene and methanol – was also fraught with difficulties; the evaluation of the results of this industrial pilot study was completed on August 25, 2017. According to Zhang Junmin, the company’s chairman, after the technical achievement assessment was completed, more than 20 companies approached the company to discuss potential cooperation. The company’s market development team also got in touch with nearly a hundred potential clients both domestically and internationally. But so far, no technology licensing contract has been signed. There is a risk of market surplus. \"Reluctance to take risks and to be the first to try something new are the main reasons why coal-based aromatic hydrocarbon technology fails to gain widespread adoption.\" ”When talking about the reasons why technology fails to gain widespread adoption, Zhang Junmin said the following. He said that the traditional process for producing aromatics from oil involves the continuous reforming and hydrocracking of atmospheric naphtha and vacuum naphtha respectively, followed by aromatic extraction to obtain benzene, toluene, and xylene ； Toluene undergoes selective disproportionation and alkylation transfer to yield xylene, which is then isomerized to produce p-xylene. Due to its long history and mature, stable technical processes, over 95% of aromatics worldwide are currently processed using this technology. Coal-based aromatics, in particular world-leading technologies such as fluidized-bed methanol-to-aromatics, methanol-toluene-to-aromatics, and selective alkylation of benzene and methanol to produce p-xylene, are new technologies that were developed only over the past 10 years, and have not yet been validated through industrial-scale plant demonstrations. The maturity of any technology is achieved through repeated applications, during which problems are identified, addressed, and the processes are optimized until they become perfect; some technologies even require repeated failures before they can succeed. Many companies are wary of the risks and challenges that may arise during the industrialization of technology, so they hold back; they prefer to let other companies take the lead and try first, before following suit once success is achieved. Such a mindset leads to more attention being paid to coal-based aromatic hydrocarbon technologies, with less actual experimentation. Zhang Junmin’s words were confirmed in subsequent interviews with reporters. Relevant officials from Shaanxi Shanjiao Chemical Co., Ltd., Shanxi Tianji Group, and CNOOC Huizhou Petrochemical Co., Ltd. all stated in interviews with reporters that although the process of producing aromatics from toluene and methanol can save a significant amount of mixed aromatic resources, and methanol still has a considerable price advantage over naphtha, theoretically making the cost of coal-based production of aromatics lower than that of naphtha-based production; compared to traditional technologies, this new technology has not been tested or refined in practice, thus posing greater application risks. As a result, they dare not adopt it lightly. “In addition to the aforementioned reasons, the rapid expansion of xylene production capacity, which poses risks of overcapacity and falling prices, is also a major reason why we approach coal-based aromatic hydrocarbon technology with caution. ”Yao Jifeng, chairman of Shaanxi Coking Company, said. He said that although China’s demand for p-xylene has exceeded its supply over the years, with import volumes rising continuously – the degree of dependence on imports increasing from 37.4% in 2010 to 56.95% in 2016, and even exceeding 59% in 2017 – the construction of domestic p-xylene production facilities has accelerated significantly since 2014, when the State Council issued the new version of the \"List of Approved Investment Projects (2014 Edition)\", granting provincial authorities the authority to approve projects related to the construction of new p-xylene, ethylene, toluene diisocyanate, and purified terephthalic acid plants. This has now led to a risk of overcapacity. The situation with toluene is exactly the opposite. Due to strong demand downstream, and affected by the **regulations on the coking industry upstream, the supply of coal tar and crude benzene is tight; as a result, their prices remain firm and continue to rise, leading to substantial profits. Taking everything into account, building a new toluene-methanol to p-xylene production facility using the company’s own methanol, toluene, and benzene as raw materials is not economically viable; in fact, it involves certain risks as well. In fact, there is indeed a risk of overcapacity for p-xylene in the domestic market. Journalists have found that currently, major p-xylene projects under construction or in the preliminary stages across China include: Hengli Petrochemical (Dalian) Co., Ltd.’s project on Dalian’s Changxing Island, which involves a 20-million-ton/year oil refinery coupled with a 4.5-million-ton/year p-xylene production facility; Zhejiang Petrochemical Co., Ltd.’s project in Zhoushan, featuring a 40-million-ton/year oil refinery and an 8-million-ton/year p-xylene plant; Norinco Group’s project in Qinzhou, with a capacity of 1.4 million tons/year of p-xylene; Sinopec Hainan Refining & Chemical Co., Ltd.’s 1-million-ton/year p-xylene facility; Yangfan Energy & Chemical Investment Co., Ltd.’s 1-million-ton/year p-xylene plant in Qinzhou; Sinochem Quanzhou Petrochemical Co., Ltd.’s 800,000-ton/year p-xylene production unit; Shenghong Petrochemical Group Co., Ltd.’s project in Lianyungang, which includes a 16-million-ton/year oil refinery and a 2.8-million-ton/year p-xylene plant; Sinopec Tarim Branch’s 1-million-ton/year p-xylene facility in Xinjiang; Hebei Xinhua United Petrochemical Co., Ltd.’s project in Caofeidian, involving a 20-million-ton/year oil refinery and a 4-million-ton/year p-xylene plant; and CNOOC Huizhou Petrochemical Co., Ltd.’s 1-million-ton/year p-xylene production unit. In total, these projects have a combined annual production capacity of 25.5 million tons of p-xylene. If we also include the combined PX production capacity of 10 million tons per year that has been applied for by Shandong-based refineries in locations such as Dongying, Weifang Binhai New Area, Rizhao Gangqiao, and Wudi Xinyue, then over the next five years, China’s total new PX production capacity will reach 35.5 million tons. Together with the existing operational capacity of 12.56 million tons per year, the total capacity reaches 48.06 million tons per year, representing an average annual growth rate of 36.53%. Among them, in 2018 alone, an additional capacity of 8.5 million tons per year will be added, representing a growth rate of 67.68%. According to industry plans, from 2017 to 2020, China’s production of purified terephthalic acid is expected to increase from 33.98 million tons in 2017 to 40.43 million tons. The corresponding demand for p-xylene will be 22.43 million tons and 26.68 million tons respectively, with an average annual growth rate of only 6.32%. “Over the next 10 years, China’s new production capacity of p-xylene will far exceed domestic demand, posing a significant risk of overcapacity. ”Luo Hongjing, deputy director of the Petrochemical Consulting Center at Sinopec’s Economic and Technical Research Institute, warned. Xue Yue, head of the Energy, Chemicals and Geology Trade Union in Shaanxi Province, believes that for coal-to-aromatics projects, in addition to having to deal with the risks of overcapacity and falling prices for p-xylene, they also face the challenges of declining demand for refined oil products, falling prices for naphtha, and a weakening or even disappearance of cost advantages for such projects. Cost advantages emerge over time. \"The overcapacity in p-xylene creation provides an opportunity to promote new technologies such as the production of p-xylene from toluene and methanol along with low-carbon olefins, as well as the technology for producing p-xylene through selective alkylation of benzene and methanol.\" Because the greater the overcapacity, the more competition there is over costs. Moreover, the technologies for producing p-xylene from toluene and methanol, as well as selective alkylation of benzene and methanol to produce p-xylene, offer greater cost advantages. ”Zhang Junmin said. Regarding the technologies for producing p-xylene from toluene and methanol, as well as for the selective alkylation of benzene and methanol to produce p-xylene, in an era of low oil prices, there are more opportunities due to the lack of a positive correlation with oil prices and the wide applicability of these technologies. For example, when applied in coking enterprises, this technology can use methanol and benzene produced as by-products of coking as raw materials to manufacture p-xylene, which has a higher added value; this helps to extend the industrial chain, improve the level of comprehensive resource utilization, and enhance the economic efficiency of the enterprises ； Grafting onto the aromatic compound production units in integrated refining and chemical enterprises allows for the use of inexpensive methanol as a raw material, while also significantly increasing the yield and production volume of p-xylene. This reduces the number of material cycles and production costs, thereby enhancing the overall competitiveness of such enterprises ； Coupling it with large-scale coal-to-aromatics plants using methanol fluidized beds can address the shortcomings such as the low one-pass yield of xylene and the generation of large amounts of mixtures during the production process. This approach enables process optimization, thereby increasing the yield of xylene as well as the overall efficiency of the plant, its resource utilization rate, and energy efficiency, and ultimately enhancing the project’s profitability and competitiveness. Wei Fei, a professor at Tsinghua University and a leading expert in fluidized-bed methanol-to-aromatics technology, said that the raw material for this technology is methanol. The construction of such projects can take place in western regions with abundant coal resources, or in eastern coastal areas where it is possible to import cheap methanol easily. Due to the wide range of sources for methanol – it can be produced from coal, natural gas, coke oven gas, refinery dry gas, and oil field gas – as well as through imports in response to changes in domestic and international markets – the choice of raw materials for this project is very diverse. Additionally, the target products of the project can be either p-xylene or mixed aromatics. Depending on market conditions, parameters can be flexibly adjusted to maximize output of products such as benzene, p-xylene, C9 aromatics, and hydrogen, thereby achieving optimal economic benefits. According to Cao Xianghong and Liu Zhongmin, who are academicians of the Chinese Academy of Engineering, as well as Li Dapeng, a leading expert in coal chemical engineering at Yanchang Petroleum Group, taking all factors into consideration, whether it is aromatics produced from coal or those derived from petroleum, it is necessary to operate on a large scale with integrated upstream and downstream processes. It is important to leverage the respective advantages of these approaches, achieve flexible integration in order to complement each other’s strengths, improve efficiency, and reduce risks. Taking the production of aromatics from coal via a methanol fluidized bed as an example. Once a coal-methanol-aromatics-pure terephthalic acid-polyester-textiles industrial chain is established, the overall cost of aromatics can be reduced by more than 500 yuan per ton compared to the petroleum-based route. Moreover, it is capable of taking on the shift of the textile industry from the eastern region and driving the upgrading of the industrial structure in the western region, thereby generating significant economic and social benefits and demonstrating the strong vitality of technology. Take the production of p-xylene from toluene and methanol, as well as the selective alkylation of benzene and methanol to produce p-xylene, as examples. Its main advantages are low investment and a short production process; it can be easily integrated with large-scale aromatic and coking projects, thereby improving the resource utilization efficiency of such projects, the yield of p-xylene, and overall economic benefits. In the later stage, efforts should be made to actively seek cooperation with large-scale integrated coal-coke-chemical enterprises, large-scale integrated oil refining-aromatic chemical enterprises, and large-scale projects for producing aromatics from coal via methanol fluidized beds. This will enable these entities to play a supporting and complementary role; while helping clients reduce costs and improve efficiency, it will also facilitate the widespread application of the technology. Reporters learned that in 2017, companies that established a petrochemicals-aromatics-precise terephthalic acid-polyester-fiber production chain, or that had related projects within their industrial parks, achieved significantly higher returns compared to those that operated only in the petrochemicals-aromatics or precise terephthalic acid-polyester-fiber sectors. This also verifies the experts’ views with facts. Wang Tong, deputy director of the Coal Chemicals Management Department at Huadian Coal Industry Group, also revealed in a previous interview with journalists that, in order to minimize project risks and maximize profits, the Huadian Yulin industrial demonstration project for producing aromatics from coal via methanol, with an estimated total investment of 36 billion yuan, has been revised from the original plan to produce 3 million tons of coal-derived methanol per year and 1 million tons of p-xylene from methanol, to a new plan that involves producing 3 million tons of coal-derived methanol per year, 1.2 million tons of aromatics via fluidized-bed methanol process, 1 million tons of combined aromatics (i.e., p-xylene produced from mixed aromatics), 1.6 million tons of purified terephthalic acid, and 600,000 tons of polyester – thus creating a large-scale integrated upstream and downstream production facility. Among them, Phase 1 has been adjusted to an integrated project with an annual production capacity of 1.2 million tons of coal-to-methanol, 600,000 tons of methanol-to-aromatics, 500,000 tons of p-xylene, and 800,000 tons of purified terephthalic acid.