Caprolactam, the main organic compound of nylon fiber, is mainly produced from benzene extracted from oil. However, in the conventional production process, ammonium sulfate is also produced as a by-product. The ammonium sulfate produced in this process is not profitable in proportion to the production cost and the price of raw materials as it requires considerable energy to recover it as well as an additional cost for anti-corrosion measures for the production plants. Sumitomo Chemical Company developed a new catalyst and commercialized a production process that is completely free of ammonium sulfate.
The raw materials needed for production were reduced by 25 to 40% (in term of reduced material cost) and the number of plants required for production was reduced by 60 to 70% (in terms of improved capital turnover). Due to the removal of such corrosive fluids as sulfuric acid from the plants, facility investments, repair costs, and other expenditures have been considerably reduced as well.
Sumitomo Chemical Co., Ltd. http://www.sumitomo-chem.co.jp/
Founded in 1913 as part of the Sumitomo conglomerate, the company initially operated a fertilizer plant (today’s Ehime Plant) that was built to produce fertilizer from the exhaust emitted from the copper refining process at the Besshi Copper Mine located in Niihama, Ehime Prefecture, in an effort to alleviate environmental impact. The Ehime Plant now operates as the production base to support the Basic Chemicals Sector of the company, which is a comprehensive manufacturer of chemicals.
“I am sure that most people do not know what chemical products are produced from caprolactam,” Mr. Izumi says laughingly. The answer is nylon, used in stockings and other products. This synthetic fiber originally developed as an alternative to silk is simply indispensable to our daily life today.
There are a few methods (processes) of producing caprolactam, which is mainly derived from benzene separated from petroleum, and are still being used today. There has been, however, a bottleneck that cannot be overcome by any of these methods. That bottleneck is ammonium sulfate, a by-product of the process. Although ammonium sulfate can be used as nitrogenous fertilizer, there are two problems posed by this chemical by-product.
“If you want to produce nitrogenous fertilizer, you can do it cheaper by using urea as a raw material. There is no advantage in ‘bothering to use’ ammonium sulfate. The other problem is that, after all, you are dealing with sulfuric acid, which incurs high additional cost for anti-
corrosion measures necessary for production equipment.”
For this reason, even as far back as 1942 when the commercial production of caprolactam began in Germany, many studies have been conducted on how to achieve an “ammonium sulfate-free” process. Sumitomo Chemical Company began its basic study in 1984. Mr. Izumi became directly involved in the project in 1993 upon reassignment to the Ehime Plant after his posting at the company’s Process Research Center. However, the very process the company was attempting to develop, so-called, “gas phase method,” had encountered a serious setback: a major overseas chemicals manufacturer gave up on commercializing this process despite its development up to the point of building a pilot plant for the process. They could not meet the quality standards. Against this background, there was “talk in industry circles that ‘Sumitomo’s caprolactam (produced by the gas phase method) would be no good.” The only way to silence such rumors was to come up with high quality products.
Under such circumstances, a project team was formed in 1998 for the first time in the company’s history. This joint team consisted of on-site plant operators and staff members from research institutes. The following year they began operating a test plant with a monthly production capacity of five thousand tons. However, they encountered a host of troubles in the early stages.
“In order to maintain the flow of hardened caprolactam, we wrapped the plant with copper pipes in which steam provided heating. We could have spared ourselves the trouble had we installed pipes of a dual-layer construction from the beginning. There was such a big fuss at that time about the lack of copper pipes available in Shikoku (laughingly).”
The chemical plant was operated 24 hours a day, with staff working in shifts. Still, in case of an emergency, all the staff could be called back to duty whether during the day or at night. Mr. Izumi looks back and says, “I also had to take care of one particular situation that lasted two whole days without getting any sleep.”
While operating the plant, they made various technical improvements, and as a result, in 2001, they could roughly pinpoint the start of production using the new process. Plant operation for the world’s first commercial production of ammonium sulfate-free caprolactam began in 2003.
The reason why Sumitomo Company could succeed whereas other manufacturers had failed is the catalyst that mediates chemical reactions. They provided a solution to a long-pending issue that faced the industry for more than a half century.
The plant produces no ammonium sulfate as a by-product, reduces the amount of raw materials necessary by 25 to 40%, and thanks to its simpler process whereby “redundant” chemical reactions are eliminated, the physical size of the plant itself could be reduced. Another advantage is the higher quality of caprolactam produced than is possible by conventional methods. Of the 180,000 tons of caprolactam produced monthly by the company, about 80,000 tons are now being produced using the new process.
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