MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Zincoaluminophosphate Molecular Sieves with AFI and ATS Topologies: Synthesis by Dry-Gel Conversion Methods and Their Catalytic Properties in the Isopropylation of Biphenyl
Shyamal Kumar SahaHiroyoshi MaekawaSuresh B. WaghmodeShafeek A. R. MullaKenichi KomuraYoshihiro KubotaYoshihiro SugiSung June Cho
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2005 Volume 46 Issue 12 Pages 2659-2667

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Abstract

Zincoaluminophosphates, ZnAPO-5 and ZnAPO-36 with AFI and ATS topologies, were successfully synthesized by dry-gel conversion (DGC) method: vapor-phase transport (VPT) and steam-assisted conversion (SAC) methods. ZnAPO-5 was synthesized successfully at 175°C by VPT and SAC methods using Et3N as structure directing agent (SDA). ZnAPO-36 was also obtained by VPT and SAC methods using Pr3N as SDA. The heating protocol was a key factor for the crystallization in the synthesis of ZnAPO-36: the best result was obtained by heating at 140°C for 1 d after aging of the gel at 105°C for 2 d. Calcination procedure is important to get microporous molecular sieves. ZnAPO-5 by VPT method calcined at 550°C gave clear XRD with high microporosity. Highly microporous ZnAPO-36 by VPT method was obtained by careful calcination. Characterization of these zincoaluminophosphates was performed by XRD, NH3-TPD, TG, SEM, N2 adsorption, and ICP analysis. ZnAPO-5 and ZnAPO-36 have the Brønsted acidic characters by the substitution of a part of aluminum with zinc.
The isopropylation of biphenyl (BP) over these molecular sieves gave different level of the selectivities for 4,4′-DIPB: 60–75% for ZnAPO-5 and 35–45% for ZnAPO-36: these selectivities are in the similar level to corresponding magnesioaluminophosphates corresponding magnesioaluminophosphates. These differences of ZnAPO-5 and ZnAPO-36 in the selectivity are due to the pore structure: ZnAPO-5 has one-dimensional straight channel; however, ZnAPO-36 has one-dimensional channel with side pocket. The steric restriction by ZnAPO-5 effectively controls the transition state to differentiate the slim isomers from others; however, pores of ZnAPO-36 cannot differentiate effectively the isomers because of their side pockets.

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© 2005 The Japan Institute of Metals and Materials
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