(560hg) Elucidating the Factors Governing the Organic-Free Interzeolite Transformation

Jain, R., University of Houston
Rimer, J. D., University of Houston

RimerAdmin Normal Jain, Rishabh 2 114 2019-04-12T16:08:00Z 2019-04-12T16:08:00Z 1 427 2438 University of Houston 20 5 2860 15.00

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normal">Elucidating the Factors Governing
Organic-Free Interzeolite Transformation

Rishabh Jain1 and Jeffrey D. Rimer1


normal">1 bold">Department of Chemical and Biomolecular Engineering, University of
Houston, Houston, Texas


color:#333333;background:white">There is increased interest to identify new
commercially viable routes to produce zeolites with well-defined physicochemical
properties. One such approach is seeded growth, which can expedite zeolite
crystallization by reducing the induction time and impeding the formation of
unwanted impurities. Seeding also provides a route to eliminate expensive
organic structure-directing agents (OSDAs) from the synthesis; however, the
theory behind seeded growth is still unclear due to the inherent complexity of
zeolite crystallization and the vast number of species in synthesis mixtures. Interzeolite transformation involves the use of a parent
zeolite with a different framework as that of the seed, often used as a sole
source of silica and alumina, which transforms into a desired daughter
structure. Okubo and co-workers have hypothesized these transitions are
facilitated by a common composite building unit (CBU) shared between the parent
and daughter zeolite.1


color:#333333;background:white">In this presentation, we will discuss the role
of different physiochemical parameters such as temperature, time, seed properties
(Si/Al ratio, crystal structure), and growth solution composition, to elucidate
the mechanistic details of seeded growth and interzeolite
transformation. We will show the role of kinetics and thermodynamics in such interzeolite conversions. To this end, we utilize ternary (kinetic) phase diagrams to select
the compositions for the seeds and growth solutions to avoid the formation of polymorphs.2
From these studies we have found that the seed phase is metastable, and can
facilitate the formation of the same phase at short times; however, longer
synthesis time often leads to secondary transformation to a putatively more
thermodynamically stable isostructure.

color:#333333;background:white">Here, we will also present our study on the synthesis
of ZSM-5 (MFI) via direct transformation of USY (FAU) in the absence of
organics and seeds.3To the best of our
knowledge, this is the first report of such transformation involving two
zeolites lacking a common CBU. This process, which was previously deemed
improbable, is achieved using a growth medium that favors OSDA-free ZSM-5
crystallization. We observed that the crystalline product obtained from this
transformation has fewer surface defects (e.g. intergrowths) compared to ZSM-5
crystals obtained by direct synthesis (i.e. non-zeolitic



text-indent:-.25in;mso-list:l2 level1 lfo3">(1)  
Itabashi, K., Kamimura, Y., Iyoki, K., Shimojima, A., Okubo, T.; normal">J. Am. Chem. Soc. 134 (2012)
11542-11549. DA;mso-fareast-language:ZH-CN">

text-indent:-.25in;mso-list:l2 level1 lfo3">(2)  
Maldonado, M., Oleksiak, M.D., Chinta, S., Rimer, J.D.; J. Am.
Chem. Soc.
135 (2013) 2641-2652.

text-indent:-.25in;mso-list:l2 level1 lfo3">(3)  
mso-ansi-language:DA;mso-fareast-language:ZH-CN">Qin, W., Jain, R., Hernandez,
F.R., Rimer, J.D.; Chem. Eur. J. 25 (2019) 1-7.