Thursday, December 08, 2005

Nice piece of heterogeneous catalysis chemistry

Warning: chem geek ahead.

Nature is one of the two major weekly science magazines (along with Science). Heterogeneous catalysis is an old discipline and not overly interesting (huh!) in this day and age of genomics, preteomics and nanotech so when a nice piece of work is done, and recognised, it's only fitting i give it a plug (Nature, News & Views, 27 Oct 2005).

Green chemistry (no, it's not an oxymoron) is a research theme that tries to minimise the amount of wasteful products produced during the synthesis of commodity chemicals. In fact, with a lot of chemicals, you can accurately describe the 'desired' product as a minor by-product of the synthesis route. Ratio's of [weight not useful]/[wt useful] of 1000:1 are not overly uncommon, especially with tricky organic molecules (needed for all those pesky FDA studies...).

A lot of chemical synth's are done in liquid form with the catalyst (a substance that speeds up the rate of the rxn) also in liquid form (homogeneous catalysis). This makes for tricky clean-up of your product at the end and it is often very difficult to recycle the catalyst itself - this all adds up to $$
It would be much nicer to do a reaction between two liquids and have the catalyst as a solid (heterogeneous catalysis). Recycling the catalyst is then pretty trivial.

John Thomas and Raja (Proc. Natl. Acad. Sci. USA 102, 13732-13736 (2005)) have come up with a way of doing both the redox and rearrangement steps of Epsilon-caprolactam synthesis on the same catalyst. They have taken a novel structured pore oxide system (Aluminium Phosphate Oxides, AlPO's) and replaced about 4% of the Al atoms in the framework with manganese and magnesium.
Epsilon-caprolactam is the precursor to nylon manufacture and its classic synthesis involves both sulfuric acid and fuming sulfuric acid (don't ask, it's as bad as it sounds). All this acid needs to be neutralised and vast quantities of ammonium sulphate get generated. Considering some 4 million tonnes of CPL are produced each year, eliminating the waste (the major product!) would be a good thing all round.

Even if you're not a huge fan of industrial chemistry (which i would debate, there's no iPods without chemistry...) you would have to agree that investing some research money into developing cleaner methods for delivering our chemistry needs is a good thing and the efforts of JT and R should be applauded as a high impact example of what can be acheived. Well done.


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