Open AccessSynthesis and Characterization of Architecturally Modified Mesoporous-Microporous MFI (Mobil Five) Zeolite with Enhanced Catalytic Activity
Author(s) -
Dhanju Mani Pathak,
Pankaj Kumar Ghosh,
Kishor Kr Shah,
Anup Kumar Talukdar
Publication year - 2021
Publication title -
asian journal of chemistry/asian journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.145
H-Index - 34
eISSN - 0975-427X
pISSN - 0970-7077
DOI - 10.14233/ajchem.2021.23352
Subject(s) - microporous material , zeolite , chemistry , mesoporous material , chemical engineering , crystallinity , catalysis , adsorption , carbon fibers , inorganic chemistry , organic chemistry , materials science , crystallography , composite material , composite number , engineering
Four samples of MFI zeolites with silica to alumina ratio of 100 and using different silica to carbonmass ratios (1:1, 1:4, 1:8 and 1:12) were synthesized by using carbon black particles. Silica-aluminamolar ratio imposes the framework structure to the synthesized zeolites. In general with an increase inthe silica-alumina molar gel ratio, the thermal stability, acid resistance and hydrophobicity of theproduct increases and ion-exchange capacity decreases. A higher molar ratio (as high as 100) of silica toalumina is considered. ZSM-5 zeolites being mainly microporous, their use as catalyst is restrictedonly to small molecules. So, by introducing mesopores in zeolite framework, we basically tried toovercome the limited use of ZSM-5 in reactions involving large molecules. Pore structure of ZSM-5can be modified by using carbon black particles during synthesis. Such type of synthesis can be usedto introduce the mesopore and to decrease the crystal size of ZSM-5 zeolite. Different silica to carbonmass ratio is used to study the pore structure and crystal size of ZSM-5 zeolites under autogeneouspressure without adding any promoter or organic solvent. The synthesized samples were characterizedby different techniques such as X-ray diffraction, FTIR spectroscopy, scanning electron microscopy,TGA and N2 adsorption-desorption isotherm. The samples exhibit high crystallinity (84-91%). Theparticle size ranged from 2.8 to 7.3 μm. Mesopore to micropore ratios was found to increase withincreasing silicon to carbon mass ratio. These structurally modified meso-micro zeolite showedenhanced activity in the benzyl alcohol esterification reaction using acetic acid. The selectivity towardsbenzyl acetate in all the cases was found to be 100%.