Interview: Prof. Eric Schelter, University of Pennsylvania

(A few weeks back, I posted about rare earth chemistry, and how insufficient domestic supply may hurt new-tech industries in the US.  Prof. Eric Schelter, a Professor of Inorganic and Materials Chemistry, graciously spoke with me about his research) 

SAO: How did you become interested in inorganic / organometallic chemistry, and rare earth / actinide chemistry specifically?

ES: I became interested in inorganic chemistry through interaction with my excellent undergrad mentor, Prof. Rudy Luck at Michigan Tech. Rudy set me up with a synthetic project on a dihydrogen complex of rhenium. This experience was quite formative as Rudy also got me interested in Texas A&M for grad school (he was a postdoc at TAMU). Also, the exposure to dihydrogen complexes introduced me to Los Alamos National Laboratory through the work of Greg Kubas.



In grad school at TAMU I did more synthesis and worked on electronic structure with Kim Dunbar. Working with Kim and her group was a great experience to learn X-ray crystallography, magnetism and electrochemistry. I had an interest in working with actinides so I pursued the LANL postdoc where I learned some uranium and thorium chemistry with Jackie Kiplinger and lanthanide chemistry with Kevin John. My interests in magnetism and f-block chemistry dovetailed nicely for starting my independent career in rare earths and energy science at Penn.







Prof. Eric Schelter (credit: UPenn)



SAO: We've read in National Geographic and Discover about rare earth usage in smartphones, hybrid cars, and military applications.  Can you give examples of other industries that rely heavily on these metals? 





ES: In general, rare earth magnetic materials are very important in many industries. Rare earth (RE) permanent magnets, primarily NdFeB, are used in the wind energy industry in large capacity turbine generators. The permanent magnets are also used in hard drives. Fluorescent lighting depends on phosphor materials that contain REs, especially europium and terbium. Neodymium is also used is lasers. Lanthanum and cerium are important catalysts in FCC [Fluid catalytic cracking] petroleum refining. Erbium is used in amplifiers for fiber optic communication. Yttrium is a critical component of high temperature superconducting materials. Gadolinium has an important use in medicine as a contrast agent in magnetic resonance imaging. This is by no means an exhaustive list.



SAO: Given the supply problem (the US currently does not produce enough rare earths for domestic industry), what is our long-term strategy to obtain more? Do we have a reserve, like the Strategic Petroleum Reserve, that we can operate from?  Or will new mining and separation techniques be the answer?

ES: There is currently no comprehensive long term strategy to address the US supply crisis and no strategic reserve of REs. A single supplier (Molycorp) of REs exists in the US, but rare earths are not rare - there are reserves of light and heavy rare earths in many places in the lower 48 [states] and in Alaska. There is a great opportunity here for scientists to help meet an important need by improving methods of obtaining pure RE materials.

SAO: How does your research address the rare earth supply problem?

ES: Much of the cost, time, and energy in obtaining rare earths is concentrated at the separations stage. We're working on new separations chemistry from several angles. In work sponsored by the DOE we're developing a new extractant strategy for use in liquid-liquid separations. We expect to contribute to a renewed domestic supply chain by targeting certain high value REs and improving the efficiency and reducing the environmental impact of their separations. We are also exploring fundamental redox chemistry of REs for application to separations.

SAO: Tell me something fun about yourself, your research, or your group.

ES: I am a complete /Lord of the Rings /enthusiast (freak) and am anxiously awaiting the film release of The Hobbit: An Unexpected Journey (SAO: Me too!)



Wow, much thanks to Prof. Eric Schelter for his preparation and willingness to be interviewed. Readers, if you (or someone you know) on the cutting-edge of chemistry would like to be interviewed, simply leave a comment here or contact me at seearroh_at_gmail.com

Update (8/11, 8:45AM): Carmen & CEN YouTube Channel recently covered Eric's chemistry

Rare Earths, Common Problem

Rare earth elements have made quite a stir lately: just last month, both Discover and National Geographic have written full articles about these 17 unique metals, which comprise the top part of the periodic table “f-block” (plus scandium and yttrium). Pundits and scientists alike are anxious that the US won’t be able to compete in the high-tech sector with scarce domestic rare earth supply.

Discover’s Hugh Aldersey-Williams (July / Aug 2011, p. 62) takes the historic view, starting from the elements’ first discovery in Ytterby, Sweden (1787, yttrium) and wending through the myriad of uses for the rare earths in modern-day electronics, hybrid cars, lighting, and materials.  The NatGeo article (June 2011, p. 136) takes a decidedly more polemically charged stance, peeking over the fence at China’s 97% share of the world rare earths market. Reporter Tim Folger argues that China’s unmatched mining infrastructure, coupled with lax environmental restrictions and cheap labor, make it tough for US miners to compete, despite the importance of a regular supply – the world demand for technology items such as iPods, wind turbines, flatscreens, and military equipment may drive lanthanide demand to a projected 185,000 tons by 2015, of which the US can only account for 5,000 tons of production. Worse, Folger bases this estimate on the production of a single mine (Molycorp) in California.

So what’s the impact for synthetic chemists?

Many of our favorite reactions use these metals. Lanthanum and scandium triflate promote aldols, acetylation, imine addition, cyclopropanation, and guest-star in new reagents like Leighton’s “EZ-crotyl” (JACS 2011, 6517). Samarium diiodide, a 1-electron reducing agent with a penchant for carbonyls and halides, underlies the Evans-Tischenko and Barbier couplings.  Cerium ammonium nitrate (CAN), a stable, off-the-shelf oxidizer, plucks off TBS and PMB groups, and promotes oxidative fragmentations. Perhaps even more worrisome is that the cerium and samarium reactions usually use the metal-containing reagent in large excess.

How can we fix the problem? New labs might find themselves conducting cost-benefit analyses simply to see if the improved reactivity or selectivity offered by these metals is worth their increased price (the Hoveyda-Grubbs 2^nd-gen catalyst, a highly active precious metal catalyst based on still-rarer ruthenium, runs $671 USD / 2g).  Perhaps the NSF will step in to issue challenge grants to develop catalytic processes intended to wean us from rare earth excesses. Either way, we’ve got to figure it out soon; as the US has shifted to a service-based economy, we’ve lost many skilled laborers (steel workers, miners, heavy industry) and may not be able to increase our rare earth capacity quickly enough.

Updates (July 28, 8:15PM) - Ever-helpful editor @carmendrahl informs me of a fantastic rare earth cover story from C&EN.  Others showed me the WIRED post about the US stealth fleet.

(July 30, 7:40AM) - Here's a July 2011 story in Scientific American debating the potential for harvesting rare earths from ocean floor sediment. Says Duke researcher Cindy Van Dover: "Four thousand meters in the deep ocean is a long way down"

(August 27, 10:36PM) - Commenter gippgig refers to Science News cover story, see here