Wednesday, August 24, 2011

Process Wednesday: trying the brute force approach

From Th'Gaussling, a reminder that the simple, direct approach can work, too:
Reaction chemistry (not including biochemical transformations!!) can be thought to occupy two broad domains- 1) low temperature, ambient pressure transformations with highly reactive species (preferably named after dead chemists), and 2) high pressure, high temperature transformations with lower reactive species. Most chemists fresh out of school know the former better than the latter. And that drives our problem solving strategies: Finding reactive intermediates that will react between -30 C and 150 C with a 5 lb nitrogen sweep in a kettle reactor. 
Sometimes, the dumber brute force approach is worth considering.  What can be done under pressure and at elevated temperature?  Or, what can be done at high temperature and short contact time?  That dusty Parr reactor sitting in the corner may be capable of a goodly bit of magic.  Behind a shield. It is good to visit the high temperature, high pressure world now and then. Of course, our engineering friends already know this. 
As far as the search for simplicity goes, consider what merits there may be in thermally driven transformations. Every once in a while it may be a viable avenue for something useful. Try thinking of heat as a kind of reagent. Chemical plants are good at producing heat.
I feel like some chemists attempt the brute force method, hoping to get lucky when they'll actually get a brown sludge. But there is real value in simplicity, especially in processes. It seems to me that the limitations of scaling up the brute force approach have to do with your equipment. If your vessels can't run reactions at high pressure or you're not willing to purchase/build a flow reactor, you can't go there.

Remember, when brute force fails, you're just not trying hard enough.

1 comment:

  1. Microwave reactors are very useful for small brute force reactions, I attempted one yesterday. Unfortunately a sudden (thus far unexplained) pressure increase caused a little too much pressure and a minor explosion.
    The cavity has now been cleaned out and dried, but it goes to show that brute force is the lesser used course for a reason...

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