Lanthanide Contractions and a Dog’s Lunch

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The rare earths are a curious group of elements from the commercial point of view.  There are a variety of lanthanide products available from a handfull of vendors, most of whom cater to a small group of users. Some of the catalog houses have respectable collections of them.  My friends at GFS offer lanthanides- specializing somewhat in cerium products.  Aldrich, Gelest, and Strem, of course, offer a variety of rare earths (RE). Hard to say if they are big sellers-I’m guessing they are on the slow side of the 80/20 rule.  I’m aware of a single American company that actually refines Scandium Oxide and manufactures Scandium Triflate as well. They are one of the few, if not the only, companys in North America that refines any RE’s. Most everyone else imports from Estonia, Russia, or China.

From my perusal of the literature it seems that the field partitions roughly into reagents for chemical transformations and oxides for material science.  The material science side is way beyond my reach, so I’ll pass on that segment.

The least expensive and most basic RE products are the oxides. If you spend some time shopping around for various RE’s, what you’ll find is a sliding scale of purity specs, 99%, 99.9%, 99.99%, 99.999%, etc.  If you look even closer to the specs, what you’ll find is some sleight of hand in regard to what the number of nines actually represents.  Most vendors will offer a number of 9’s that are TREO, Total Rare Earth Oxides. So if you are keen on Scandium Oxide, 99.99 % (or 4N), chances are that the 4 nines really represents the total of all of the RE oxides present.  In reality, 99.99 % TREO Sc2O3 will be 99.9 % in Scandium and the balance of the 4 nines is a dogs lunch of Ln Oxides. 

As we all know, when you analyze for more and more 9’s, you eventually find most of the periodic table present in your material.  But if you really want 99.99% in Scandium, it can be relatively hard to sort from the TREO products.  You are forced to swim through spec sheets to find material that meets your need. BSC offers 4N in Scandium, and some others do as well.

One of the interesting applications of RE triflates is as a water tolerant acid catalyst.  Essentially all of the RE triflates have been reported, with the possible exception of Promethium. The lanthanides show a general decrease of ionic radius as one increases atomic number. This is the lanthanide contraction. It has been shown that the catalytic activity in certain acid catalyzed reactions (i.e., with a Ln(III) triflate) correlates with the charge-to-radius ratio in this group.  Not surprising, I suppose. 

So, for an ambitious person with designs of bringing rare earth reagents to the marrket, this is a classic “technology push” situation.  In order to convince people to buy RE triflates as acid catalysts, you first have to offer a value proposition.  They can use conc H2SO4 or they can use Yb(OTf)3 as an acid catalyst. Hmmm.  So which is cheaper in my application?  Given the sparse literature on Ytterbium Triflate chemistry, for instance, it could be hard to convince a customer to adopt your RE product beyond R&D use.

So, whaddaya hafta do to sell a boat load of this stuff? You probably have to come up with a killer application for the RE Triflate to convince people to buy it and try it. If you as the purveyor lack this application, they you have to rely on the customer to do it for you.  In the mean time, you could get very hungry.

4 thoughts on “Lanthanide Contractions and a Dog’s Lunch”

  1. JimT

    Beadnusto, I gotta admit that most of this is completely over my head. Do you have anything on the tactile cohesive coefficiency of Velvetta cheesefood (a.k.a. petroleum distillate)?

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  3. Jordan

    I read an interesting statistic the other day — I think it was in the C&EN “Periodic Table” special from last year — that several of the REs, I think La, Ce and Nd, are more common in the earth’s crust than Pb. I found this hard to believe (with the possible exception of Ce which really is quite common).

    The trick with the lanthanides, as you suggest, is separating them from one another. I have an antique “chemist’s handbook” at home that still describes an element called “didymium” (before chemists were sure how many lanthanides there should be, I guess) Of course, now we know that didymium = Nd + Pr, which are difficult to separate.

    If you look up Hf salts in the Aldrich catalogue, they all list their respective purity levels — followed by the disclaimer that these numbers don’t include the few percent of Zr that is naturally present. Interesting stuff.

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  4. gaussling Post author

    Yeah, that business with Zr in your Hf can be a serious problem too. For instance, if you make a catalyst based on Hf, there is a chance that you also have some quantity of the corresponding Zr species present. Of course, this depends on the sequence of steps that were used. It is not uncommon for there to be a large difference in activities between Zr and Hf species. So a 1 % concentration of a Zr catalyst that is 100x faster than the Hf species would lead one to make incorrect conclusions about the catalyst. Fortunately, companys like Wah Chang will allow you do do lot picking of your Hf to keep the Zr levels low and consistent. This is a serious problem for those doing Group IV catalyst development.

    Thanks for bringing up the info about Didymium! I was unaware of that.

    I’m interested in RE’s these days. Especially Erbium. There is a glut of Erbium Oxide on the market right now and so it is reasonably cheap.

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