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<strong>Counter-intuitive comparable diffusivity of xylene isomers in zeolitic mesopores: Confirmation from adsorption and catalysis studies</strong>

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Title Statement <strong>Counter-intuitive comparable diffusivity of xylene isomers in zeolitic mesopores: Confirmation from adsorption and catalysis studies</strong>
 
Added Entry - Uncontrolled Name parikh, parimal a; Chem. Eng. Dept., SV National Institute of Technology, Surat 395007
 
Uncontrolled Index Term Aromatic alkylation; Diffusion coefficient; Mesoporous zeolite; Shape selectivity; Zeolite beta
 
Summary, etc. The reaction of commercial interest, toluene methylation to selectively obtain <em>para</em>-xylene has been studied. For this purpose, zeolite Beta is modified to impart mesoporosity in the crystals such that formation of kinetically favour <em>para</em>-isomer (as advocated by some schools earlier) facilitates and diffuse out easily. However, when this modification did not meet the expectation, pore openings on crystal surface have been narrowed using tetraethyl <em>ortho</em>-silicate (TEOS). Albeit, TEOS is found to enter the pores of modified zeolite and no <em>para</em>-selectivity could be attained and proportion of <em>meta</em>-isomer higher than thermodynamically determined is obtained. Catalytic- and xylene adsorption kinetic- results led to conclude (1) diffusivity of <em>para</em>-xylene is only 1.33 times higher than that of the <em>meta</em>-isomers in parent and hierarchical zeolite Beta samples and (2) extent of increase in diffusivity of <em>para</em>- and <em>meta</em>-xylene due to mesoporosity generation is comparable (about 1.14 times) unlike increase by 2 order of magnitude reported in case of ZSM-5. These observations dispel the early reckoning: large pore zeolites affording <em>para</em>-xylene selectivity in the reaction of toluene methylation.
 
Publication, Distribution, Etc. Indian Journal of Chemical Technology (IJCT)
2018-07-05 10:41:26
 
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http://op.niscair.res.in/index.php/IJCT/article/view/16587
 
Data Source Entry Indian Journal of Chemical Technology (IJCT); ##issue.vol## 24, ##issue.no## 5 (2017): Indian Journal of Chemical Technology
 
Language Note en
 
Nonspecific Relationship Entry http://op.niscair.res.in/index.php/IJCT/article/download/16587/49738