Chemical vapour deposition (CVD) of molybdenum into medium pore H-zeolites

Several medium pore H-zeolites (HZSM-5, HIM-5, HTNU-9 and HZSM-11) were evaluated toward molybdenum deposition via chemical vapor deposition using Mo(CO)₆ as the molybdenum precursor. The deposition was through a high temperature adsorption of Mo(CO)₆ vapor onto dehydrated zeolites. The progress of deposition was monitored gravimetrically. Exsitu infrared (FTIR) spectroscopy was employed to observe the interaction between Mo(CO)₆ and the zeolites during the deposition. X-ray photoelectron spectroscopy (XPS) was used to scrutinize the nature of molybdenum deposit within the zeolite. High temperature adsorption of Mo(CO)₆ vapor is an irreversible adsorption resulted in a molybdenum deposition onto the zeolites whereas the adsorption conducted at room temperature is a reversible one. Interaction of Mo(CO)₆ and the zeolites at high temperature led to the reaction of Mo(CO)₆ and hydroxyl group within zeolites i.e. silanol group and Brnsted acid site. The molybdenum dispersion within the zeolites was governed by the particle size of the zeolite. More concentrated molybdenum deposited on zeolite surface occurred on the zeolite with bigger particle size. The highest surface molybdenum deposition was observed on ZSM-11 surface as it has the biggest particle size.