Development of HZSM-5/AlMCM-41 hybrid micro-mesoporous material and application for pyrolysis of vacuum gasoil

The pyrolysis of vacuum gasoil (VGO) was studied alone and in presence of HZSM-5/AlMCM-41 hybrid catalyst. This micro-mesoporous material was synthesized by the hydrothermal method using dual templates of tetrapropilamonium and cetyltrimethylammonium ions at different crystallization times. The obtained materials were washed and calcined for remotion of the organic templates. The characterization by X-ray diffraction, nitrogen surface area by the BET method, scanning and transmission electron microscopies, evidenced that typical MFI structure was embedded into the bulk of the MCM-41 matrix, in order to obtain the hybrid micro-mesoporous phase. The protonic form of the material was obtained by ion exchange with ammonium chloride solution and subsequent thermal treatment. The total acidity, as determined by n-butylamine adsorption, was equivalent to 0.75 mmol g(-1), in the temperature range of 300-500 degrees C, corresponding to strong acid sites. For catalytic reaction, a physical mixture of 10% of catalyst/VG was decomposed in a thermobalance at heating rates of 5; 10 and 20 degrees C min(-1), from 100 to 550 degrees C. From TG/DTG data, applying the model-free kinetics, it was observed that the activation energy for the pyrolysis of VGO alone was ca. 125 kJ mol(-1). For VG physically mixed to both AlMCM-41 and HZSM-5, the value decreased to ca. 80-90 kJ mol(-1), whereas for the hybrid, the value was the lowest, ca. 65 kJ mol(-1), evidencing the efficiency of the combined effect of the acid sites, crystalline phase and microporosity of ZSM-5 zeolite with the accessibility of the mesoporous of the AlMCM-41 ordered material. For determination of the catalytic properties, the samples of VGO and catalyst/VG were submitted to pyrolysis-GC-MS system at 500 degrees C using helium as gas carrier. The VGO alone suffers decomposition to a wide range of hydrocarbons, typically C-17-C-41, while in the presence of catalyst, light fraction of hydrocarbons, in the range of liquefied petroleum gas (C-3-C-5), gasoline (C-6-C-10) and diesel (C-11-C-16) were obtained, evidencing that the HZSM-5/AlMCM-41 hybrid material is an effective catalyst for pyrolysis of VGO. (C) 2013 Elsevier Inc. All rights reserved.