Synthesis And Catalytic Properties Of Fe-Mn-MCM-41 And Al-Mn-MCM-41

The mesoporous MCM-41 molecular sieves have potential application as catalysts. But the pure silicon MCM-41 limited its application for catalysis owing for the lack of active sites in their matrixes. It is necessary to incorporate metal centers into the framework which are able to increase the acidaty and catalytic activity. The incorporation of two different metals might create materials with different acid properties and catalytic activity. Epoxides represent an important class of oxygenated heterocycles in organic synthesis. One of the most widely used method for epoxidation of alkenes is the use of H₂O₂ as oxidant. only a few useful catalytic systems for epoxidation with H₂O₂ have been developed. So it is important to incorporate two different metals into MCM-41 framework to create new catalysts.In the first part of the experiments, Manganese and iron were incorporated by template-ion exchange?TIE? and direct hydrothermal?DHT? methods to develop Fe-Mn-MCM-41 mesoporous. The samples were characterized by X-ray diffraction?XRD?, Fourier transformation infrared spectrum?FT-IR?, Scanning electron microscopy?SEM?, transmission electron microscopy?TEM?,N2-adsorption-desorption techniques and H2 Temperature programmed reduction?H2-TPR?. The results illustrated that the definite structure of the MCM-41 was retained after incorporate Mn and Fe into MCM-41 by different methods.In the second part of the experiments, The catalytic activity and selectivity of the Fe-Mn-MCM-41 in the epoxidation of styrene with 30% H₂O₂ as an oxidant agent were explored. The Fe-Mn-MCM-41-2 showed the highest activity. However, the Fe-Mn-MCM-41-4 and Fe-Mn-MCM-41-5 catalysts showed poor performance in the catalytic epoxidation of styrene. Various parameters such as different reaction molar ratio of H₂O₂/styrene, catalyst amount, concentration of NaHCO3 and kinds of solvents were studied to optimize the reaction conditions.In the third part of the experiments, Manganese were incorporated by template-ion exchange?TIE? to the Al-MCM-41 which syntheses from natural palygorskite without addition of silica or aluminum reagents. The samples were characterized by XRD, SEM, TEM, N2-adsorption-desorption techniques. The results illustrated that the Al-Mn-MCM-41 has the definite structure of the MCM-41. TheAl-Mn-MCM-41 showed better epoxyethylbenzene selectivity in the epoxidation of styrene with 30% H₂O₂ as an oxidant agent than Mn-MCM-41-T. Various parameters were also studied to optimize the reaction conditions.