Studies of all-silica zeolite nucleation and growth from clear solutions: Is ZSM-5 the exception and not the rule?

COLL 415

Daniel F Shantz and Henry Cheng. Department of Chemical Engineering, Texas A&M University, TAMU Mail Stop 3122, College Station, TX 77843-3122
The formation and growth of zeolite ZSM-5 has been intensely studied over the last two decades. These studies have proved invaluable for developing a possible explanation of both zeolite nucleation and growth. Of particular note are the numerous studies of Silicalite-1 formation from clear solutions at low (< 373 K) temperatures given the (relative) ease with which one can study in situ growth of this particular system. A question we will address here is: how many all-silica zeolites can be nucleated and crystallized under these conditions? We will discuss work performed in our lab on the nucleation and growth of ZSM-12 made from clear solutions at low temperature in the presence of a variety of SDAs. These investigations include both particle nucleation and growth using SAXS and DLS as well as chemical speciation using 29Si NMR. We will also discuss work on ZSM-11 made with an SDA selective for MEL formation without MFI intergrowths as well as describe ongoing work studying the feasibility of using other SDAs such as N,N,N-trimethyl-1-adamantammonium hydroxide for the nucleation and growth of all-silica zeolites from clear solutions.