| Popis: |
Zeolites are three dimensional microporous structures that play a crucial role in catalysis owing to their tunable properties. MFI and beta are the most common zeolites that have been investigated over time for catalysis. MFI zeolite due to its shape selectivity has been a very good choice for many commercial processes like cracking and biomass conversion. But due to diffusion limitations there is an observed decrease in catalytic activity of these zeolites. Incorporation of heteroatoms like tin in the MFI structure is shown to increase the catalytic activity and selectivity of the zeolite. Tin (IV) chloride (SnCl4) has been traditionally used as the precursor for the tin incorporation into the MFI. We will demonstrate that using a different precursor to introduce the heteroatom changes the properties and catalytic activity of the Sn-MFI zeolite. The project aims to study the effects of tin incorporation using different tin precursors on the Sn-MFI properties. Properties like crystallization time, morphology and the catalytic activity of the Sn-MFI are studied for different sources of tin like tin acetate and tin tertiary butoxide. These properties are compared to that of Sn-MFI synthesized from tin (IV) chloride for further studies. The crystallization process is monitored using DLS to determine the effect of including a heteroatom (tin) into the zeolite framework. The catalyst is characterized using several analysis techniques such as powder X-ray diffraction (PXRD), nitrogen physisorption, Dynamic Light Scattering (DLS), and Diffuse Reflectance UV-Vis Spectroscopy (DRUVS). The catalytic activity of the novel material is evaluated using epoxide ring opening reaction in alcohols as a probe reaction. Sn-MFI material synthesized from tin acetate exhibits better properties like faster crystallization time, small particle size, higher surface area and higher tin incorporation when compared to the other precursors. But the epoxide when reacted with methanol achieved a higher conversion with Sn-MFI material synthesized from tin chloride compared to the materials synthesized from other precursors. Tuning the TPAOH content was observed to affect the properties of the materials. It was demonstrated that decreasing the TPAOH content increased the percentage yield, tin incorporation efficiency, and the catalytic activity of the zeolite. |
