Computational Study of p-Xylene Synthesis from Ethylene and 2,5-Dimethylfuran Catalyzed by H-BEA

CATEGORY: PARA-XYLENE
Computational Study of p-Xylene Synthesis from Ethylene and 2,5-Dimethylfuran Catalyzed by H-BEA

Type	Journal Article
Author	Yi-Pei Li
Author	Martin Head-Gordon
URL	http://dx.doi.org/10.1021/jp506664c
Volume	118
Issue	38
Pages	22090-22095
Publication	The Journal of Physical Chemistry C
Date	September 25, 2014
Abstract	Researchers determined detailed mechanisms for the synthesis of p-xylene as well as the primary byproducts observed experimentally, 2,5-hexadione and 2,5-dimethyl-3-[(4-methyl-1,3-cyclohexadien-1-yl)methyl]furan, from ethylene and 2,5-dimethylfuran (DMF) mediated by H-BEA employing an extended QM/MM model containing 208 tetrahedral atoms. Analysis of the free energies associated with the mechanisms suggests that the secondary addition can be eliminated by introducing n-heptane as an inert solvent to decrease the loading of DMF in the zeolite or by using a weak Bronsted acid site to facilitate the dehydration of the Diels?Alder product, for which the rate is determined by the deprotonation via the conjugate base of the active site. Water formed in the dehydration process can react directly with DMF to form 2,5-hexadione, thereby decreasing the yield of p-xylene. However, the free-energy barriers for the formation of 2,5-heaxdione compared to the Diels?Alder reaction indicate that DMF and 2,5-hexadione will be equilibrated. Consequently, the 2,5-hexadione yield can be minimized by operating at a high conversion of DMF.