Molecular sieves MCM-41 presenting acid properties obtained by various techniques

Samples of MCM-41 mesoporous molecular sieves presenting different pore sizes were prepared from a gel presenting the following molar composition: 1,0 SiO₂: 0,12 CTABr: 0,28 TMAOH: 100 H₂O. The samples pores diameter was controlled by changing temperature and time synthesis. An acid function was incorporated by two different methods taken from literature: the impregnation of tungstophosphoric acid and incorporation of sulphated zirconium from ZrOCl₂.8H₂O. According to the X-ray diffraction analysis, the sample synthesized at 150°C for two days presented more ordered crystalline structure, higher values of interplanar (d100) distance and was more stable to acid function incorporation. Based on that, this sample was choose to be catalytically evaluated. From nitrogen adsorption isotherms, a BET surface area of 723 m²g^-1 and a pore size of 46,1Å were determined for the sample synthesized at 150°C for two days. It was shown by infrared spectroscopy that acid function was incorporated very efficiently into MCM-41 pores. The samples were catalytically evaluated by using cumene cracking reaction. It was observed that all functionalized samples presented activity and that the most active one was that with 30% of tungstophosphoric acid. Keywords: Heteropolyacid, sulphated zirconium, tungstophosphoric. (author)