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Most cellulose fibers are manufactured from dissolving pulp by means of the viscose process. In spite of improvements, this technology consumes more than two metric tons of chemical additives and considerable fresh water volumes per metric ton of cellulose fiber made, requiring major waste water treatment efforts.
In contrast to this, BASFworking with the Denkendorf Institute for Textile Chemistry and Chemical Fibers (ITCF) have discovered through their joint research that cellulose fibers can be produced in an efficient and environmentally sustainable manner by using ionic liquids. The big advantage is that ionicliquids can be almost entirely recycled.
And, furthermore, practical tests have shown that the efficiency of the production processcan be greatly enhanced by the use of ionic liquids. This is becausecellulose dissolves better in ionic liquids.
“Cellulose fibersproduced by means of ionic liquids have properties comparable to those of conventionally made fibers,” said Dr. Eric Uerdingen of the New Business Development team within BASF’s Intermediates division.
Cellulose: A major renewable resource
Cellulose is the earth’s most widespread natural organic chemical and, thus, highly important as abiorenewable resource. The earth’s resources are estimated to be 700billion tons, of which nature renews 40 billion tons each year. Of this, industry uses only 0.1 billion tons as feedstock for further processing.
A more intensive exploitation of cellulose as a biorenewable feedstock has to date been prevented by the lack of a suitable solvent. The use of ionic liquids for the first time permits production of cellulose solutions at concentrations that are technically attractive. This new technology therefore opens up great potential for cellulose processing.
BASF has five years of experience with ionic liquids, both in manufacturing these materials and in their full-scale industrial use. At its Ludwigshafen site, the company has been running the first large-scale industrial process worldwide that uses ionic liquids. This process allows fast and simple removal of acids from reactionmixtures. The reaction of an acid with a base results in a liquid salt instead of solid crystals, which frequently causes process problemsin production.
Use of ionic liquids does away with time-consuming and expensive filtration. These liquids can be easily separated from the desired products, like oil from water, and can also be reused.1 Methylimidazol, which replaces other bases used as additives, additionally acts as a catalyst, thus speeding up the reaction considerably.
An eco-efficiency analysis has confirmed that BASF’s BasilTMprocess for scavenging acids in the chemical synthesis of phosphoruscompounds offers significant advantages over the conventional system.Compared to amines, which have been used traditionally in this type ofreaction, the BASF process based on 1 methylimidazole is less cost-intensive and at the same time easier on the environment. The new process for synthesizing phosphorus compounds, which are used as chemical building blocks to produce UV-curable coatings, reliably avoids a numberof problems encountered to date: Stability and product yield improve,and the process is less laborious.
Future promise
“We believe ionic liquids hold many promises for the future,” said Dr. Matthias Maase, who works in the New Business Development unit of the BASF Intermediates operation division, “By their properties they will open up entirely new fields of application, even outside the classical chemical uses. For example, think of ionic liquids as new materials or as engineering liquids used in the mechanical and automotive industries, but also in oil and gas production, and they might even be used in thefield of renewable resources. The road to use in practice is taking shape. Maase added, “We are currently talking to companies from the mostvaried industries all over the world who have recognised the benefitsof ionic liquids and are discussing concrete applications with us.”
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