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Ethylene glycol produced from coal: Where lies the path for downstream applications? Author/Source: Sinochem New Network Date: October 27, 2020 Clicks: 2 At present, the rapid increase in domestic production capacity of ethylene glycol derived from coal is leading to an increasing disparity caused by the overly limited range of downstream applications; the operating capacity of facilities producing such ethylene glycol is only 40%. In our country, over 90% of ethylene glycol is used in PET polyester, and a considerable number of polyester manufacturers have established an integrated industrial chain that covers crude oil – PX – PTA – PET polyester – textiles. There are no more opportunities for coal-based ethylene glycol to be integrated into the downstream PET industry chain. So, where lies the path for further development of coal-based ethylene glycol? Polyglycolic acid: Market demand is expected to grow. Polyglycolic acid (PGA) is an ideal fully biodegradable material that can be completely degraded within 1–3 months; it is non-toxic and harmless, with carbon dioxide and water as its end products. It holds great potential for use in areas such as medical sutures and biodegradable plastics. At present, PGA chips still rely entirely on imports. Dimethyl oxalate (DMO) is the most important intermediate in the coal-based ethylene glycol production process; DMO can be hydrogenated to produce either ethylene glycol or methyl glycolate. By replacing the hydrogenation catalyst in the DMO, production can be shifted from ethylene glycol to methyl glycolate and glycolic acid, which can then be used to produce PGA; internationally, the dominant process technology is the ring-opening polymerization of lactide. At present, there are dozens of domestic manufacturers of PGA sutures, but most of them reprocess imported PGA finished sutures from countries such as South Korea. If PGA produced by enterprises that manufacture ethylene glycol from coal enters the sutures industry, it will face a disruption in the product supply chain, as there are no domestic companies capable of spinning PGA chips, and the amount of PGA chips used in sutures is limited; moreover, the requirements regarding production and storage conditions for such materials are quite high. Another use of PGA is as supermarket shopping bags, agricultural films, disposable plastic tableware, and packaging for deliveries. Currently, most supermarket shopping bags are made of polyethylene, with a factory price of over 7,000 yuan per ton. The production cost of PGA sheets is around 8,000 yuan per ton; therefore, there is no cost advantage to using PGA as a substitute or in combination with other materials. Although a ban on plastic use has been implemented, biodegradable plastics are still in the stage of promotion in our country; the development of this market depends on the reduction in the cost of biodegradable plastics as well as the severity of the ban. However, one fundamental fact is that in recent years, with the rapid growth of industries such as food delivery and online shopping and parcel delivery, the usage of plastic packaging bags for deliveries has been increasing year by year, and demand for PGA is also expected to grow. PEN polyester: promising prospects for industrial applications. Polyethylene terephthalate ether (PEN) is one of the polymer materials that has seen the fastest development and application in recent years. Its structure is similar to that of PET, but the difference lies in the fact that naphthene rings replace the benzene rings in PEN’s molecular structure. Naphthalene rings possess more stable resonance structures than benzene rings; the molecular chains are more rigid, and the structure is more planar. As a result, their mechanical and chemical properties are superior, making them suitable for use in insulating films, food heat-sealable bottles, and pharmaceutical packaging films. The general synthesis route for PEN involves using 2,6-naphthalic acid or dimethyl 2,6-naphthalate along with ethylene glycol as raw materials; through esterification or transesterification reactions, the monomer 2,6-naphthalic acid ethylene glycol ester is synthesized, which is then subjected to a polycondensation reaction to produce PEN. Currently, only Mitsubishi Gas Chemical Company in Japan, Amoco in the United States, and Sumitomo Chemical Company in Japan possess the technology for the industrial production of PEN. Due to the complex production process and high costs associated with 2,6-naphthalenedicarboxylic acid, there have been no manufacturing facilities in China; as a result, raw material shortages and high prices have hindered the production and use of PEN in the country. Ethylenediamine: Still a long way to go before industrialization Ethylenediamine is primarily used in the production of pesticides, pharmaceuticals, and various chemical additives. Its synthesis methods mainly include the dichloroethane method, ethanol amination method, ethylene oxide method, ethylene amination method, etc. From the perspective of reaction principles, the aminoalkylation of ethylene glycol is an ideal route for producing ethylenediamine, and directly converting ethylene glycol into ethylenediamine represents a better process. BASF disclosed a method for producing ethylenimine and ethanolamine from ethylene glycol, with an conversion rate of 46% for ethylene glycol. The one-step hydroamination method for producing ethylenediamine involves feeding ethylene glycol and ammonia into a reactor where a hydroamination reaction takes place, resulting in the formation of ethylenediamine and water, with ethanolamine as a by-product; after the reaction, the mixture is separated to yield ethylenediamine. At present, the process of producing ethylenediamine by the amination of ethylene glycol is not yet mature. The main problems are poor catalyst stability, numerous side reactions that are difficult to control, and a long way to go before it can be industrialized. Additionally, the demand for ethylenediamine in China is not high. 1,3-Dioxolane: Limited opportunities for use in combination with other substances. 1,3-Dioxolane is used as an extractant, an electrolyte solvent in lithium batteries, a stabilizer for chlorinated solvents, and a second monomer in polyoxymethylene; it is produced by the reaction of polyoxymethylene or concentrated formaldehyde with ethylene glycol. 1,3-Dioxolane is used as a pretreatment solution to soak lithium electrodes, and its consumption is limited. As the second monomer for polyoxymethylene, 1,3-dioxolane is required in an amount of about 2,000 tons for a polyoxymethylene plant with a production capacity of 40,000 tons per year. Currently, the annual production capacity of polyoxymethylene in China is around 300,000 tons, which requires 20,000 tons of 1,3-dioxolane. To ensure stable raw material prices, most polyoxymethylene manufacturers also produce 1,3-dioxolane; Tangshan Zhonghao Chemical Co., Ltd. is currently launching a project to produce 4,000 tons per year of 1,3-dioxolane. Indole: The domestic production technology is not yet mature. Indole is a white crystal and an important intermediate in the fine chemical industry; it serves as a key raw material for producing fragrances, dyes, as well as drugs used to prevent and treat cardiovascular diseases, neurological disorders, tumors, and to boost immunity. One of the most important uses is as an intermediate in the synthesis of tryptophan, used as an efficient feed additive. Indole was originally obtained mainly from coal tar, but this process is difficult to separate, requires high energy consumption, and has a complex purification procedure. The synthesis of indole from aniline and ethylene glycol is a new one-step method for indole synthesis developed in Japan in the mid-1990s. This method not only features low raw material costs and a simple operating procedure, but also generates no waste such as inorganic salts during the reaction, making it the most economical among various indole synthesis methods. Currently, in China, there are issues with catalyst development and high reaction temperatures, and the technology is not yet mature. PETG and PCTG copolyester: The cost-performance ratio is not satisfactory. PETG and PCTG are copolyesters formed by the polycondensation of terephthalic acid, ethylene glycol, and cyclohexanediol (CHDM). Among them, the copolyester with a CHDM content of over 50% is PCTG, while the copolyester with a CHDM content of less than 50% is PETG. The biggest advantage of PETG/PCTG over PET is that it meets environmental protection standards and FDA approval requirements for food use. The molded products possess excellent transparency, toughness, chemical resistance, and processability, making them suitable for use in applications involving food contact, cosmetic packaging, medical devices, and drug packaging. However, the high production cost of CHDM directly affects the cost-performance ratio of its downstream polyester products. Ethylene glycol ethers: signs of overcapacity emerging Ethylene glycol ethers, used as industrial solvents, are typically produced through a catalytic reaction between ethylene oxide and corresponding anhydrous alcohols. Ethylene glycol is cheaper than ethylene oxide; using ethylene glycol as a raw material to synthesize ethylene glycol ethers requires mild reaction conditions and poses little risk. Among the ethylene glycol ether product series, butyl ethylene glycol ether is used in the largest quantities, while monomethyl ethylene glycol ether is used in relatively smaller amounts. Terbutyl ethylene glycol ether, as a new type of environmentally friendly solvent, can be used in the production of plastic coatings for computers, mobile phones, digital cameras, high-end cars, etc. It is manufactured from ethylene glycol and isobutylene as raw materials. Currently, four or five companies in Shandong and other regions are producing tert-butyl ethylene glycol, leading to a surplus in supply. Glutaraldehyde: Overcapacity exists in the domestic market. Glutaraldehyde, also known as oxalic aldehyde, is mostly available in the market as an aqueous solution with a concentration of 30%~40%. There are mainly two industrial methods for the production of glyoxal: the oxidation of acetaldehyde and the oxidation of ethylene glycol. The ethylene glycol oxidation method features simple process equipment, high concentration of the primary product, easy post-treatment, and suitability for continuous production. Taking into account factors such as environmental protection and quality, the ethylene glycol oxidation method is superior to the acetaldehyde oxidation method, representing the development trend in the production of glyoxal. At present, there is an oversupply of glyoxal production capacity in China. Hubei Luotian Hongyuan Pharmaceutical Technology Co., Ltd., which has the largest production capacity in the country, has started construction on a production facility with an annual capacity of 100,000 tons this year.