Influence of acidity of modified chloroaluminate based ionic liquid catalysts on alkylation of iso-butene with butene-2

In the present work, aluminium chloride based ionic liquids (ILs) were used as catalysts for alkylation of isobutane with butene-2. Some additives such as, transition metal salts, water and acidic cation exchange resins were used to improve the selectivity of the main products and the yield of reaction. A high content of the desired trimethylpentanes (TMPs) (up to 72.3%) and thus a high research octane number (RON up to 98) of the alkylate were received on using CuCl modified triethylamine hydrochloride aluminium chloride ([Et3NH]Cl/AlCl3) (molar fraction of AlCl3 is 0.6) at -5 degrees C over a period of 15 min. The effectiveness of additives is assumed to explain by the formation of Bronsted acid or complexes which exhibit the Bronsted acidity or superacidity. The acidity of investigated catalytic systems was evaluated by FT-IR and confirmed that. The Bronsted and Lewis acidic sites were detected by FT-IR. The Lewis acidity can be adjusted mainly by mol fraction of AlCl3 while the Bronsted acidity can be increased by using the suitable amounts of additives. This is a valuable guide to explain the mechanism and to select the catalysts for alkylation. (C) 2012 Elsevier B.V. All rights reserved.