Efficient homogeneous and supported ionic liquid catalysts for production of linear alkylbenzenes

Abstract

AlCl3 based homogeneous ionic liquids, such as 1-butyl 3-methyl-imidazolium chloroaluminate ([BMIm]+Al2Cl 7 − ), 1-butyl 3-methyl-pyridinum chloroaluminate ([BMPy]+Al2Cl 7 − ), and triethylamine hydrochloride chloroaluminate (Et3NHCl-AlCl3), were prepared to study the benzene alkylation with 1-dodecene. All homogeneous ionic liquid catalysts have shown higher selectivity (∼40%) for desired 2-LAB (2-linear alkylbenzene) than the conventional AlCl3 catalyst (∼32%). Apart from the homogeneous catalysts, one supported ionic liquid catalyst (SG–N+(C2H5)3–Al2Cl 7 − ) was also synthesized. The supported ionic liquid catalyst showed further increased selectivity of the 2-LAB (∼45%). Moreover, the reusability of SG–N+(C2H5)3–Al2Cl 7 − catalyst was much higher than the homogeneous ionic liquid catalysts. The supported ionic liquid catalyst was characterized by various techniques such as FT-IR, MAS-NMR and Scanning Electron Microscopy (SEM). Hammett acidity function (Ho) was used to determine the acidity of supported ionic liquid catalysts. The pyridine adsorbed FT-IR spectra of (SG–N+(C2H5)3–Al2Cl 7 − ) catalyst showed presence of common Bronsted (Bronsted)—Lewis acidic sites. The 27Al MAS-NMR of (SG-N+(C2H5)3-Al2Cl 7 − ) catalyst showed a band at ∼6.987 ppm, which is attributed to 6-coordinated Al species. A nonlinear optimization algorithm was developed in MATLAB 7.4.0 to determine the kinetic parameters of the benzene alkylation with 1-dodecene in presence of (SG–N+(C2H5)3–Al2Cl 7 − ) catalyst. The concentrations of the products predicted by model were found in good agreement with experiments (relative error ∼1.5%).