The tar cleaning and phenol extraction technology has passed technical evaluation

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The technology for cleaning coal tar to extract phenol has passed technical evaluation. Author/Source: Collaborative Group on Advanced Processing and Hydrogenation of Coal Tar; Date: 2022-04-16; Clicks: 12. Developed independently by Shaanxi Coal and Chemical Technology Research Institute Co., Ltd., this technology uses coal tar phenol oil as raw material and a biphasic solvent extraction process; the crude phenol obtained through this method has high quality and low impurity content, making it easy to further refine and separate. The successful development of this technology has solved the problem of efficiently and cleanly extracting high-value phenolic compounds from coal tar. It not only generates substantial profits but also reduces hydrogen consumption in the downstream processes for lightening coal tar, thereby further improving overall economic efficiency; it holds great significance for the industry of deep processing of coal tar. It takes a decade to break through the bottlenecks in this field. Phenols such as phenol, methylphenol, and xylene are widely used in various high-value fine chemicals industries including pharmaceuticals, fragrances, engineering plastics, and phenolic resins; their chemical synthesis is complex. Currently, the industrial extraction of phenol from coal tar relies on acid-base leaching processes that result in high pollution levels and high energy consumption, which hinders the sustainable large-scale development of this entire industry. The high-boiling-point extractants used in phenol extraction technology increase the energy consumption required for their recovery ； The crude phenol product obtained contained large amounts of pyridine and neutral oil impurities, which increased the cost of refining the crude phenol. Since 2012, Shaanxi Coal and Chemical Technology Research Institute Co., Ltd. has been working on research and development related to the clean extraction of phenol from coal tar. To address the high energy consumption associated with conventional coal tar phenol extraction agents, the research team developed a two-phase solvent extraction system based on the principles of like dissolves like and azeotropy. This system utilizes a continuous counter-current extraction process to efficiently extract and separate crude phenol from phenol-rich oil as well as from dephenolated oil, thereby achieving complete removal of neutral hydrocarbon oils such as naphthalene from the crude phenol. The extraction agent can be recovered and reused through distillation. The presence of pyridine-based impurities in crude phenol significantly affects its quality and leads to high costs associated with its purification. To address this issue, the research team developed a technology for the selective removal of such impurities from crude phenol, enabling their efficient elimination and thereby improving the quality of the crude phenol. This lays a solid foundation for subsequent low-cost purification processes. The pilot test was successful. On November 18, 2021, the project for the clean extraction of phenol from coal tar completed a 72-hour evaluation on a pilot plant designed for the extraction of phenol from phenol-rich oil at a capacity of 80 tons per year. The extraction efficiency of crude phenol from the phenol-rich oil was 97.68%, while the content of phenol and its derivatives in the crude phenol was 99.19%. No hydrocarbons, neutral oils, or pyridine alkaloids were detected by gas chromatography. All process and product parameters met the specified standards. The pilot plant has operated for a total of 840 hours, with 260 hours of continuous and stable operation; the extractant can be reused over extended periods, and all performance parameters remain stable. On March 11, 2022, the coal tar extraction technology for phenol recovery passed the technical evaluation conducted by industry experts. The panel unanimously agreed that this technology is at the leading level in China and approved its acceptance. It was also pointed out that the technology already meets the conditions for further expansion, and it is recommended to accelerate the work in the next phase by integrating it with the crude phenol refining process. Black oil-based phenols open up new prospects. China’s resource profile of abundant coal, limited oil, and scarce gas means that coal will continue to play a dominant role in the country’s energy structure for a long time to come; therefore, it is essential to utilize coal in a clean and efficient manner. In 2020, China’s coal tar production reached 26 million tons. The regions of Northern Shaanxi, Western Mongolia, Shanxi, and Ningxia are important energy bases as well as hubs for the modern coal chemical industry in China, where coal tar resources are relatively concentrated. The lack of efficient processes for cleaning and extracting phenols at present results in the loss of a large amount of high-value phenolic resources, which hinders the scaling up of the entire coal tar phenol extraction and refinement industry, thereby restricting industrial upgrading and the expansion of the value chain. The production of high-purity phenols from coal tar for use in fine chemical products not only helps to reduce China’s dependence on imported oil and ensure energy security, but also facilitates the advancement of the coal chemical industry. This leads to the formation of industrial clusters focused on fine chemicals such as pharmaceuticals and fragrances, as well as new polymer materials, thus opening a new chapter in the development of advanced coal chemical industries.