skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Theoretical Study of the Mechanism Behind the para-Selective Nitration of Toluene in Zeolite H-Beta

Abstract

Periodic density functional theory calculations were performed to investigate the origin of the favorable para-selective nitration of toluene exhibited by zeolite H-beta with acetyl nitrate nitration agent. Energy calculations were performed for each of the 32 crystallographically unique Bronsted acid sites of a beta polymorph B zeolite unit cell with multiple Bronsted acid sites of comparable stability. However, one particular aluminum T-site with three favorable Bronsted site oxygens embedded in a straight 12-T channel wall provides multiple favorable proton transfer sites. Transition state searches around this aluminum site were performed to determine the barrier to reaction for both para and ortho nitration of toluene. A three-step process was assumed for the nitration of toluene with two organic intermediates: the pi- and sigma-complexes. The rate limiting step is the proton transfer from the sigma-complex to a zeolite Bronsted site. The barrier for this step in ortho nitration is shown to be nearly 2.5 times that in para nitration. This discrepancy appears to be due to steric constraints imposed by the curvature of the large 12-T pore channels of beta and the toluene methyl group in the ortho approach that are not present in the para approach.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1040980
Report Number(s):
PNNL-SA-76439
KP1704020; TRN: US201211%%310
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Book
Resource Relation:
Related Information: Industrial Applications of Molecular Simulations, 1-22
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM; BROENSTED ACIDS; DENSITY FUNCTIONAL METHOD; NITRATES; NITRATION; ORIGIN; STABILITY; TOLUENE; ZEOLITES; nitration; toluene; density functional theory; calculations; zeolite H-beta

Citation Formats

Andersen, Amity, Govind, Niranjan, and Subramanian, Lalitha. Theoretical Study of the Mechanism Behind the para-Selective Nitration of Toluene in Zeolite H-Beta. United States: N. p., 2011. Web.
Andersen, Amity, Govind, Niranjan, & Subramanian, Lalitha. Theoretical Study of the Mechanism Behind the para-Selective Nitration of Toluene in Zeolite H-Beta. United States.
Andersen, Amity, Govind, Niranjan, and Subramanian, Lalitha. Mon . "Theoretical Study of the Mechanism Behind the para-Selective Nitration of Toluene in Zeolite H-Beta". United States.
@article{osti_1040980,
title = {Theoretical Study of the Mechanism Behind the para-Selective Nitration of Toluene in Zeolite H-Beta},
author = {Andersen, Amity and Govind, Niranjan and Subramanian, Lalitha},
abstractNote = {Periodic density functional theory calculations were performed to investigate the origin of the favorable para-selective nitration of toluene exhibited by zeolite H-beta with acetyl nitrate nitration agent. Energy calculations were performed for each of the 32 crystallographically unique Bronsted acid sites of a beta polymorph B zeolite unit cell with multiple Bronsted acid sites of comparable stability. However, one particular aluminum T-site with three favorable Bronsted site oxygens embedded in a straight 12-T channel wall provides multiple favorable proton transfer sites. Transition state searches around this aluminum site were performed to determine the barrier to reaction for both para and ortho nitration of toluene. A three-step process was assumed for the nitration of toluene with two organic intermediates: the pi- and sigma-complexes. The rate limiting step is the proton transfer from the sigma-complex to a zeolite Bronsted site. The barrier for this step in ortho nitration is shown to be nearly 2.5 times that in para nitration. This discrepancy appears to be due to steric constraints imposed by the curvature of the large 12-T pore channels of beta and the toluene methyl group in the ortho approach that are not present in the para approach.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Nov 28 00:00:00 EST 2011},
month = {Mon Nov 28 00:00:00 EST 2011}
}

Book:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this book.

Save / Share: