Surface, textural and catalytic properties of pyridinium hydrogen sulfate ionic liquid heterogenized on activated carbon carrier

Abstract Pyridinium hydrogen sulfate ionic liquid (PHS) heterogenized on activated carbon (AC) is investigated for the first time in the current paper. For that purpose, the xPHS/AC (x = 8, 17, 33 and 66 wt%) samples are analyzed by a number of physicochemical methods such as N2 adsorption–desorption measurements, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Catalytic activity and reusability of xPHS/AC are evaluated in the reaction of butyl acetate synthesis. Effect of the reaction temperature and catalyst loading on the butyl acetate yield are examined in this work as well. Important thermodynamic parameters such as equilibrium constant, activation energy, Gibbs free energy and activation energy barrier for the reaction of butyl acetate synthesis in the presence of xPHS/AC are determined. Textural characterization revealed the that xPHS/AC are mixed micro-mesoporous materials. The PHS heterogenization on AC affects both ionic liquid and support phases due to a surface PHS–AC interaction. FT-IR and XPS showed that this interaction is: (i) manly expressed as a close contact between the pyridinium cation and the functional groups on the AC surface and (ii) electrostatic in nature. The existence of a PHS–AC interaction is found to be responsible for the formation of surface PHS particles of various size. However, the catalytic activity of xPHS/AC is established to be affected by the surface active phase amount, but not the PHS particle size.