Journal of Petroleum & Environmental Biotechnology

DFT study on the mechanism of alkylation reaction between isobutane and 2-butene catalyzed by chloroaluminate ILs

World Congress on Petrochemistry and Chemical Engineering

November 18-20, 2013 Hilton San Antonio Airport, TX, USA

Daxi Wang, Peng Wang, Jingjiang Liu, Chunming Xu, Jinsen Gao and Xinghua Liu

Accepted Abstracts: J Pet Environ Biotechnol

Abstract:

The mechanism of C4 alkylation reactions catalyzed by choroaluminate ILs is studied by quantum chemical methods, with the Gaussian 03w using DFT B3LYP method, at 6-31G* basis set level. It is found that Al 2 Cl 7 - is the catalytically active component, and AlCl 3 is the final catalytically active center in the Lewis acid. 2,2,3-TMP from the reaction between tert-butyl action and 2-butene is the product controlled by kinetics, while 2,2,4-TMP is the product controlled by thermodynamics with greater yield. And the main reaction mechanism between isobutane and 2-butene catalyzed by ionic liquid Et 2 NH-Al 2 Cl 7 is as follows: I. Chain initiation: the -electrons of 2-butene and AlCl 3 can form a stable ADC complex catalyzed by ionic liquid [(C 2 H 5 ) 3 NH] Al 2 Cl 7 . AlCl 4 - and cations are combined to form the neutral organic salts. The formation of ADC complex is a spontaneous process. II. Chain propagation: the ADC complex can act with isobutane to extract hydrogen and form tert-butyl cation. The activation energy of the reaction is 54.26kJ/mol, which is means the reaction can easily occur. The tert-butyl cation acts with the double bond of 2-butene, forming a three-membered ring carbon onium ion which can rearrange to form 2,2,3-TMP + ; while the 2,2,3-TMP+, through a methyl shift, rearranges to generate 2,2,4-TMP + which is relatively more stable with a low energy. III. Chain termination: 2,2,4-TMP + captures another H- from isobutane to form 2,2,4-TMP and tert-butyl cation, termination the chain termination reaction. IV. Circular reaction: The above product tert-butyl cation acts with 2-butene to generate another 2,2,3-TMP + . After rearrangement it can act with isobutane and circular reaction continues until the reaction completes. The results can explain the experimental phenomena very well