Monday, October 9, 2017

This week's C&EN

A few articles from this week's issue of Chemical and Engineering News:

10 comments:

  1. the new Akzo Nobel manufacturing route for oligo-ethyleneimines actually uses ring-opening reaction of oxazolidines with primary amines in the presence of urea as carbonylating agent (not carbon monoxide as shown in the scheme!!). The products are cyclic ureas (imidazolidinones) that are converted to polyamines by hydrolysis with NaOH. There is no mystery whatsoever, it is all laid out in the patent experimental examples. The amount of time it took to draw the incorrect scheme shown in C&EN would be better spent by reading experimental examples 1 and 2 in the patent...

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  2. I find it hard to believe that route is commercially competitive with EO-amine routes. Cheap raw materials, better atom economy, fully depreciated plants.

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    1. The amine process gives mixtures of mono-, di-, and triethanolamines from ammonia (Industrial Organic Chemistry, 4th Edition, 2003, Weissermel and Arpe, p. 159) - even at 10:1 ammonia:ethylene oxide, both di- and triethanolamines are formed in significant amounts. You'd have to use a massive excess of ammonia and recycle, which is easy on scale, but the separation might suck. So the current process might not be so atom-economic.

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    2. The process you describe is absolutely correct. The process has been practiced for decades and markets have been found (and still exist) for every distillation fraction. Just about nothing goes to waste. Also, given that it appears the key step in this Akzo process involves nucleophilic ring-opening it is not clear to me that it will or should be selective either - once nitrogen is alkylated it becomes a better nucleophile and thus gives secondary and tertiary amines. Profit margins in the ethyleneamines/ethanolamines business are quite healthy. You'd have to have a very significant change in economics to enter this market and compete.

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    3. Hap - This is Anon 6:51/9:57. Take a look at the patent linked to in the CENews article, especially the examples. They are making mixtures as well. Separating those mixtures from the aqueous caustic used in the workup probably isn't too pretty either. Really not clear to me why this was chosen to be highlighted in CENews, other than possible lobbying by Akzo.

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  3. to clarify, I see this as a relatively brutal but enviro-friendly way to turn OH group in ethanolamines into NHR, by heating with urea (and optionally with sone added primary amine). Urea "activates" the OH by forming oxazolidine, it also provides ammonia equivalent for the aminolysis. You need to hydrolyze the formed imidazolones at the end, thats is the ugly part. But probably still better than chloralkali-based process. My main gripe was with C&EN writer not bothering to read the patent experimental examples and publishing incorrect reaction scheme

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    1. Agree that the CENews write up and scheme is awful/wrong.

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    2. The book I got the alternative process from used another process (direct oxidation) to generate the ethylene oxide - using direct oxidation burns some of the ethylene to CO2 but probably doesn't generate the waste the chloro-alkali process would.

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    3. There may not be anyone who still uses the dichloroethane process to make ethyleneamines/ethanolamines, the EO process replaced most of it. Ethylene is at >90% selectivity to EO and at enormous scale - that's where all of your ethylene glycol comes from.

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    4. typo - sorry - should read: Ethylene is oxidized at >90% selectivity to EO...

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