Role of the Si/Al molar ratio and pH in NIW/MCM41-Al2O3 catalysts for HDS of DBT

Abstract

This research presents a series of catalytic supports of MCM41 modified with γ-Al2O3 with a Si/Al molar ratio of 10, 25 and 50. These materials were impregnated with Ni+W solutions at pH 7 and pH 9, respectively and were evaluated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction. In order to modify the low acidity of MCM41, its surface acidity was modified by incorporation of alumina content in the supports.The sol–gel incorporation method of Al2O3 to the structure of the MCM41 did produce changes in the characteristic of hexagonal arrangement of mesoporous materials.The symmetries of the materials were determined through UV–vis where the octahedral and tetrahedral nickel species were found. By Raman, monotungstate (WO4) and polytunsgtate (W12O408−) species were observed. The HDS of DBT showed that in the NiW/AMS50 catalyst impregnated at pH 9 presents the highest reaction rate. And in the case of the catalysts impregnated at pH 7 the highest reaction rate was achieved by the NiW/AMS10 catalyst. The selectivity was mainly oriented to the production of biphenyl (BP). The low catalytic activity was attributable to low formation NiWS species responsible for the HDS activity.