A study of the regioselectivity in the zeolite-assisted nitration of toluene

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Joel M. Barden III (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/

Abstract: Nitration of toluene has been an important industrial process for many years. The conventional method is effective in nitrating toluene, but it produces an ortho:meta:para (o:m:p) ratio of approximately 57:4:39, respectively. There has been considerable effort studying the potential for various zeolites to influence regioselectivity towards the para- isomer, which is the most desirable isomer. By introducing zeolites into the process, the regioselectivity can be directed with the proper selection of the pore size of the zeolite used. The use of the zeolite catalysts improved the regioselectivity of the reaction and has produced the para-isomer as high as 80%. It has been reported that the increase in regioselectivity is related to the silica/alumina ratio (SAR) of the zeolites used. This is somewhat unexpected based upon size selective reactions in other zeolite systems. Our investigations of the zeolite assisted reactions led to the conclusion that the increase in the regioselectivity of these reactions did not depend on the SAR, as previously reported, but is due to the pore size of the zeolite. The improved zeolite reaction produced an isomeric distribution of 18% ortho-, 0.52% meta-, and 82% para-mononitrotoluene with more readily available zeolites. While investigating the regioselective zeolite reaction, a side product was noted that had not previously been reported with respect to this reaction. This side product was considered a contaminant initially and its production was minimized during the reaction. The contaminant was identified as phenylnitromethane, PNM and it was determined that its production was significantly different from the nitrotoluene in that a radical reaction was responsible instead of an aromatic substitution. After identification, it was decided to take advantage of this side reaction to produce the PNM, as the reported methods were difficult and/or time-consuming syntheses. The zeolite method for producing the PNM was investigated and yielded 3.00g of phenylnitromethane (94% purity by GC).

Additional Information

A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Aromatic compounds, Toluene--Research
Toluene -- Research
Aromatic compounds

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