On April 21, 2000 the chemical engineering department invited Michael Deem from the University of California, Los Angeles to discuss his research on Zeolite frameworks and structure solutions using Monte Carlo techniques. Pizza was served to the class, as usual.

Dr. Deem started off his presentation of what a zeolite is and what its framework resembles. Zeolites are a class of crystalline aluminosilicates, which occur naturally and are synthesized in the laboratory. Recently, they have become extremely important in industrial processes, including catalytic cracking of alkanes, air separation, and ion exchange. There are many different types of zeolites about 130 that have known structures and there are many more that are being discovered. The common feature that distinguishes these zeolites is the structural similarities. Dr. Deem then began to talk about what the zeolite framework is composed of. Zeolites have frameworks that are composed of "tetrahedrally-coordinated atoms" which are sometimes referred to as T-atoms. Oxygen atoms join these atoms. Through various pictures and illustrations Dr. Deem showed us that the T-atom is usually silicon he then described the main feature of zeolite frameworks, which is the presence of pores. These pores consist of are 4-12 Angstrom in size. Some of these frameworks have one-dimensional pores, and some even have two or three-dimensional pores.

The next part of his discussion included structure solutions for determining what these zeolites look like by a Monte Carlo method. The Monte Carlo method generates a bunch a random numbers and it tries to find the similarities between measured diffraction values. He proposed two types of methods, one, which is the Metropolis method and a new Biased method. The Metropolis method is the conventional method and does not work for all the zeolites and it is not very efficient. The Biased method; however, is very powerful and efficient, thus, it is the desired method. It is able to calculate the structures very quickly. One of the structural determinations was completed in about four hours. He then talked a little about the difficult in determining the structures. The difficulty stems primarily from the polycrystalline nature of most zeolites. Some of his last comments included the discussion of how is it crucial to develop the field of zeolite science to determine the structure of newly synthesized materials. Dr. Deem then emphasized for us to look into zeolite science and consider graduate school so that we can understand it.

The chemical engineering thanked Dr. Deem for his presentation.

I found a website that shows an animated structure of zeolites and it is really interesting if anyone is curious to see what many different zeolite structures look like. The web address is: http://www.iza.ethz.ch/IZA/

Submitted by Craig Pribila

ChE 102, Class of 2003