A novel single-surfactant templating was explored for the synthesis of mesoporous zeolites under hydrothermal conditions and microwave irradiation. The latter was employed for easy programming of temperature and time over a wide range of conditions, allowing a significant reduction of the synthesis time from days to hours [1]. The following molar composition was studied: 16CTAB:12Na2O:100SiO2:2Al2O3:2500H2O. Two different synthesis routes were examined: one-pot synthesis (OS) and two-step synthesis (TS) using different crystallization time. Mesopores were created by using cetyltrimethylammonium bromide (CTAB) surfactant as a soft template and the crystalline microporous framework was formed in the absence of organic molecular template [2]. The XRD analysis of the samples prepared at different crystallization times revealed the formation of the MOR/MFI type of microporous structures with different degree of mesoporosity. The resulting materials were stable and suitable for catalytic applications involving larger molecules such as catalytic cracking used for conversion of heavy oil fractions into light liquid hydrocarbons. These materials were characterized by using powder X-ray diffraction, and nitrogen and carbon dioxide adsorption. The XRD analysis was employed to identify the crystalline phases in the materials studied, while adsorption isotherms were used to evaluate their surface area and porosity. A detailed characterization of the samples studied revealed that their properties are comparable with those reported in literature for the samples obtained by dual templating or conventional autoclave heating [3]. Namely, the resulting materials are hybrid micro-mesoporous structures consisting of zeolitic crystallites (ZSM-5 and Mordenite-type crystalline domains) co-existing with the amorphous domains of hexagonally ordered mesoporous silica, MCM-41. The catalytic testing of these materials involved pyrolysis of VGO (vacuum gasoil) physically mixed with 10 wt.% of the catalyst at 500 �C coupled with a GC-MS system (helium used as a carrier gas); the recorded spectrum for catalytic pyrolysis of VGO is shown in Figure 1 in comparison to the spectrum obtained for pyrolysis of VGO alone (without catalyst). The latter spectrum reflecting the pyrolysis of VGO alone is located in a wide range of hydrocarbons, typically C17�C41, while the spectrum for catalytic pyrolysis of VGO shows the light fraction of hydrocarbons in the range of liquefied petroleum gas (C3�C5), gasoline (C6�C10) and diesel (C11�C16), indicating that the mesoporous zeolitic materials prepared via single surfactant templating under microwave irradiation are effective catalysts for pyrolysis of VGO.

Microwave-assisted single-surfactant templating synthesis of mesoporous zeolites

248th National Meeting (2014)

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