PETR 8 |
| The hydrothermal synthesis of MCM-68 (MSE topology) has been only possible so far by using N,N,N',N'-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium diiodide (diquat-diiodide) as an organic structure-directing agent (SDA). The gel composition window for the successful crystallization of the pure MCM-68 is very narrow and the Si/Al ratio of the product has been limited to 9-12. The use of so-called “steam-assisted crystallization (SAC) method” gives a highly crystalline MSE-analogue with currently unattainable chemical composition, i.e. purely siliceous composition, which is totally different from that of typical MCM-68. Unlike the starting gel for MCM-68 containing K+ and diquat-diiodide, the gel for YNU-2P has more ordinary, halogen-free composition containing Na+ as well as diquat-dihydroxide. Moreover, the crystallization period is much shorter for the SAC method than for the hydrothermal synthesis and the SAC product exhibits very high crystallinity. The as-synthesized SAC product is designated as YNU-2P. Upon calcination, the framework of YNU-2P collapsed to give amorphous. In order to avoid this collapse, post-synthetic silylation successfully provids the material with robustness and the framework remains after calcination. The SDA-free, pure-silia material is designated as YNU-2, which is the first example of highly crystalline, pure-silica version of the MSE-like molecular sieve. |
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Zeolite Catalysis for Green Chemistry in Synthesis of Chemicals and Fuels
8:20 AM-12:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 209, Oral
Division of Petroleum Chemistry |