One-step phenol with laughing gas
15 Jan 2000
Monsanto hopes to be laughing all the way to the bank with a new, single-step process to make phenol directly from benzene. The company claims that this method produces better yields, and is cheaper, than the conventional synthesis via cumene.
In the Monsanto process, nitrous oxide (better known as laughing gas) and benzene are passed over a zeolite-based catalyst developed by the Boreskov Institute of Catalysis (BIC) in Novosibirsk, Russia. Monsanto, which carried out the reactor design and process developed and has the rights to BIC's patents, claims that there are no aqueous wastes, by-products or `significant waste products' resulting from the process. Moreover, and unlike other industrial processes involving oxidation, the process is designed so that the gas compositions within the plant are always non-flammable.
The process typically converts 99 per cent of the benzene feed into phenol, claims Monsanto - a considerable improvement over the cumeme process, which gives a 93 per cent yield.
In addition to its efficiency improvements, the process also offers Monsanto the opportunity to use one of its more troublesome waste streams. Nitrous oxide is a by-product of adipic acid manufacture, one of the stages in the manufacture of nylon. It is toxic and cannot be released to the environment, so the company currently has to install costly abatement equipment on its adipic acid plants. Using the gas as a feedstock for another process turns a cost into an asset. `This project demonstrates Monsanto's commitment to developing and commercialising new processes that emphasise the sustainable use of raw materials and the reduction of our operations' environmental impact,' comments Hameed Bhombal, director of the company's fibres technology division.
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