Which path is more promising for modern coal chemical industry?

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Which path is more promising for modern coal chemical industry? Listen to what Academician Liu Zhongmin, the lead scientist at DMTO, has to say. Author/Source: Date: 2016-05-04. Clicks: 37. Many experts and industry professionals have attempted to predict and evaluate the technical economics and prospects of modern coal chemical processing routes, but most of these assessments were based on conditions during high oil prices, and the conclusions reached by different experts varied significantly. With low oil prices, which modern coal chemical pathways are more competitive? What is the direction of development? Recently, Liu Zhongmin, an academician of the Chinese Academy of Engineering and the pioneer scientist in DMTO technology, analyzed issues related to modern coal chemical pathways, including coal-based DMTO, coal-to-oil, coal-to-ethylene glycol, coal-to-natural gas, coal-to-aromatics, as well as the differentiated utilization of coal centered on pyrolysis. 　　Coal-based DMTO still has significant room for development. Liu Zhongmin said that following the drop in oil prices, the differences in cost, economic viability, and competitiveness among various processes such as coal-based DMTO, coal-to-oil, coal-to-ethylene glycol, coal-to-natural gas, coal-to-aromatics, as well as the differentiated utilization of coal through pyrolysis, have become quite apparent. Judging from the performance of various units in 2015, coal-based DMTO remains highly competitive. Since the decline in polypropylene/ethylene prices did not coincide with the drop in oil prices, and given that oil prices fell significantly while polyolefin prices fell less, the vast majority of DMTO projects achieved good returns. Given China’s large deficit in olefins and the continued strong growth in demand, DMTO still has significant room for development. 　　To date, the DMTO technology has been licensed for 20 units, with a total capacity of 11.26 million tons per year; 9 units have been built and put into operation, offering a total capacity of 5.2 million tons per year. All these projects have yielded good economic and social benefits. In particular, in 2015, despite the continuous decline in international oil prices and the significant reduction in profits, or even losses, for many coal chemical projects, DMTO projects still managed to achieve good profits. The net profit of some coal-to-olefins plants even exceeds 1 billion yuan per year. The market has proven the strong competitiveness and promising prospects of DMTO technology and its industrial-scale plants. 　　Economics is the most fundamental and practical requirement for the success of a technology. The true significance and value of DMTO technology lie not only in its economic advantages, but also in providing coal-rich regions with a non-petroleum-based route for olefin production; it makes it possible to diversify the sources of olefin raw materials. It enables the olefin industry, which was previously constrained by resource shortages, to experience a major turning point in its development, thereby facilitating the growth of downstream fine chemical industries. For this reason, when the DMTO technology was introduced, it attracted great attention from countries in Europe, America, and Japan, as they understood that with the application of modern coal chemical technologies in China, China’s dependence on petroleum resources would change, and it could even lead to shifts in the supply and demand dynamics of downstream products. Given the fact that global coal resources are much more abundant than oil resources and are also cheaper, if other regions rich in coal and gas use coal or natural gas as raw materials to produce petrochemicals and downstream products, then the energy structure of these regions will change, which could in turn affect the global energy landscape. 　　Ethanol from coal: Prospects that are on par with DMTO. Liu Zhongmin emphasized that, objectively speaking, the prospects and significance of ethanol production from coal are not inferior to those of DMTO technology. On the one hand, there is a huge market demand for ethanol as a clean fuel for vehicles. Ethanol not only has a high oxygen content, which enables it to increase the octane rating of gasoline and improve combustion efficiency while reducing emissions of pollutants such as carbon monoxide and hydrocarbons, but it is also non-toxic and harmless, posing no risk of contaminating groundwater. For these reasons, it is widely used as a vehicle fuel or additive in gasoline in many countries including the European Union, the United States, and Brazil. Since 2005, our country has begun to promote the use of ethanol-blended gasoline in certain provinces and cities, and currently 11 provinces and cities are implementing this initiative on a widespread scale. China’s apparent annual gasoline consumption exceeds 100 million tons. By using ethanol-blended gasoline, it is possible to save petroleum while also effectively reducing the impact of vehicle exhaust emissions on the atmospheric environment. 　　Currently, there are roughly three process routes for ethanol production both domestically and internationally: directly producing ethanol from syngas obtained through coal gasification; first producing methanol from coal gasification, then manufacturing acetic acid, and finally producing ethanol through the hydrogenation of this acid; and producing ethanol through the hydrogenation of acetate esters. But to date, none of these three processes have been verified through application in large-scale industrial facilities. Currently, the Dahuahua Research Institute is working together with the Yanchang Petroleum Group to build the world’s first industrial demonstration plant for producing ethanol from coal, with a capacity of 100,000 tons per year, in Xingping, Shaanxi. This plant will be completed and put into operation in October this year, using the new technology developed by the Dahuahua Research Institute for converting coal into ethanol through methanol. 　　Moreover, compared to methanol, ethanol offers a wider range of downstream processing pathways and its derivatives have higher added value. It can be used to produce not only ethylene and ethylbenzene but also a variety of bulk chemicals and fine chemical products such as ethers, alcohols, esters, and other types of alcohols, making it highly promising for various applications. In particular, if the process for producing ethylene from ethanol can be promoted and applied by leveraging low-cost coal-based ethanol production technology, the project will have lower energy consumption, a shorter process flow, a higher conversion efficiency per cycle, as well as greater economic viability and competitiveness. It is precisely because of the promising prospects of coal-based ethanol that, over the years, some developed countries have been focusing on this technological approach, hoping that our country will achieve a technological breakthrough first. 　　Ethylene glycol produced from coal: Major industrial challenges remain to be overcome. Theoretically, producing ethylene glycol from syngas is the most reasonable approach, offering broad prospects for development; China was the first country to achieve industrialization in this area. However, further technological breakthroughs are still needed, especially to overcome the bottleneck of large-scale industrialization technologies as soon as possible. At present, the production capacity of a single reactor for coal-based ethylene glycol is not sufficient; it falls short of the concepts associated with large-scale chemical manufacturing and the corresponding scale benefits, which to some extent limits the competitiveness of coal-based ethylene glycol. If industrial technologies and equipment capable of producing 500,000 tons per year of coal-based ethylene glycol can be developed, the potential for the development of coal-based ethylene glycol will truly be unlocked. 　　Furthermore, from a technical standpoint, the catalysts still need further improvement, particularly in the development of non-precious metal catalysts and in enhancing the catalyst’s resistance to carbon monoxide or hydrogen. 　　Coal-derived aromatics: The coal pyrolysis route is more economical. Due to limitations in naphtha as a raw material, aromatics production in China is insufficient. Liu Zhongmin is in favor of coal-based aromatics, but he supports obtaining them through coal pyrolysis. He explained that this is because coal already contains a large amount of substances with aromatic ring structures. By separating it after pyrolysis, it should serve as an excellent raw material for aromatics; this approach not only enables the differentiated and graded utilization of coal but also reduces the cost of producing aromatics, making it cost-effective both in terms of atomic economy and investment efficiency. 　　Liu Zhongmin expressed disapproval of the use of methanol to produce aromatics. He emphasized that, primarily due to issues related to the carbon-hydrogen balance of raw materials and products, it is difficult to increase the yield of aromatics. Moreover, since the products are mixed aromatics, further processing and complex separation and purification are required to produce high-value products such as p-xylene, and there are concerns regarding the economic viability of this approach. Of course, as a new technological approach, it is still worth exploring, and its economic viability requires large-scale industrialization and market validation. It would be a more ideal technical approach if aromatics could be produced directly from syngas. 　　Coal-to-oil and gas: The importance of technical reserves. Regarding coal-to-oil and gas, Liu Zhongmin said that from the perspective of energy security, having necessary technical reserves and industrial demonstration projects is undoubtedly beneficial for our country. However, the several coal-to-natural gas plants that have been built or are under construction currently all utilize foreign technology; there are no substantial technological breakthroughs or innovations. It is better to avoid following the old path of importing, digesting, and absorbing such technology. 　　In terms of coal-to-oil conversion, China’s technology is already ahead. However, it is likely to lack economic competitiveness when oil prices are low. Of course, if coal-to-oil production can achieve complementarity with the refining industry and the petrochemical sector, by focusing on the production of high-purity waxes, high-molecular-weight rigid waxes, high-density oils for aerospace use, or high-grade base oils for lubricants that are in short supply in China, thereby addressing the shortcomings of the petrochemical industry, its future prospects should be promising. 　　Differentiated utilization of coal: Attention should be paid to the graded use of pyrolysis oil. Liu Zhongmin believes that the concept of differentiated coal utilization is excellent, and it represents an effective approach for the hierarchical and efficient, clean utilization of coal. However, due to the difficulties associated with pyrolysis, domestic research institutions and enterprises have focused their main efforts on this aspect, neglecting the refined and graded utilization of pyrolysis oil. At present, the vast majority of companies use a rather crude method for processing pyrolysis oil: the valuable aromatic-rich tar is hydrogenated without any distinction between its different components, and in the process of producing diesel, the valuable aromatics in the gasoline fraction are converted into naphtha with low added value. 　　He suggested that, on the basis of larger and more integrated installations, diesel should be produced while also manufacturing high-octane gasoline or aromatics. This is more scientific and reasonable both from the perspective of rational resource utilization and investment economics.