Synthesis, Characterization and Stability of Fe-MCM-41 for Production of Carbon Nanotubes by Acetylene Pyrolysis Placidus Amama, Sangyun Lim, Dragos Ciuparu, Yanhui Yang, Lisa Pfefferle, Gary Haller Yale University, Department of Chemical Engineering, New Haven, CT 06520 Introduction The use of mesoporous silica as a catalytic template for production of carbon nanotubes (CNTs) is gaining prominence because of the possibility of properly controlling the size of the metal nanoparticles [1]. The metal catalyst plays a key role during CNT growth. Several studies have revealed a direct relationship between the size of the metal particle and the eventual diameter of CNT [2]. To be able to control the physical properties (diameter and hellicity) of CNTs, a thorough understanding of the microstructure, stability and chemical properties of the catalytic sites would be necessary. In this study, different loadings of Fe-incorporated MCM-41 (ca. 1, 2 and 3 wt% Fe) were hydrothermally synthesized using different colloidal silica (HiSil-915 and Cab-O-Sil) and C16 surfactant. The synthesis procedure was adapted from a recipe previously reported for V- MCM-41 [2]. The catalysts were characterized using different techniques to determine their mesoporous structural integrity and the local environment of Fe in the silica framework. These materials were then used as catalytic templates for the production of CNTs by acetylene pyrolysis at atmospheric pressure. The results presented here reveals a strong correlation between Fe loading in MCM-41 and the type of carbon specie produced. Experiments and Results Fe loading in the catalytic templates (containing ca. 1, 2 and 3 wt% Fe) was verified by ICP. The following results were obtained: 0.99, 1.59 and 2.25 wt% Fe for samples synthesized from HiSil-915 while those synthesized from Cab-O-Sil were 0.99, 1.78 and 2.37 wt% Fe. N 2 physisorption and XRD studies carried out using calcined Fe-MCM-41 revealed a significant improvement in the mesoporous structural quality upon incorporation of ca. 1 wt% Fe, but a decrease is observed as Fe loading increases. Catalysts synthesized from Cab-O-Sil showed higher structural order in comparison to those synthesized from HiSil-915. The local environment of Fe was characterized by UV–Vis, EPR and X-ray absorption spectroscopy. Fe 3+ species in all the “as-synthesized” samples regardless of its loading were found in predominantly tetrahedral environment (framework). Upon calcination, dislodgement of some Fe 3+ species to non-framework environment occurs and this phenomenon was more severe for catalysts containing ca. 2 and 3 wt% Fe. Generally, Fe 3+ species occupying tetrahedral environment decreases with increasing Fe loading. The pyrolytic decomposition of acetylene to produce CNTs was performed at 800 °C using a C 2 H 2 /N 2 (99% N 2 and 1% C 2 H 2 ) flow rate of 200 sccm for 1 h over Fe-MCM-41. The above conditions were found to be optimal at atmospheric pressure. In a typical run, 0.5 g of the calcined catalyst was put into the cylindrical quartz reactor and heated to the reaction temperature in flowing He at 10 °C/min. At the reaction temperature, the gas flow was switched