Oki Muraza

Conversion of methanol to olefins over Al-rich ZSM-5 modified with alkaline earth metal oxides

Aluminum-rich H-ZSM-5 zeolites modified with alkaline earth metal oxides of Mg, Ca and Ba were applied in the conversion of methanol to olefins (MTO). The pores of the parent H-ZSM-5 zeolite were blocked with a surfactant prior to metal oxide modification. The resulting Mg-ZSM-5, Ca-ZSM-5 and Ba-ZSM-5 exhibited similar structural and morphological patterns to the parent H-ZSM-5. The addition of these alkaline metal oxides affected the acidity of the ZSM-5-based catalysts. Mg-ZSM-5 was found to be the most stable in the MTO reaction, maintaining a conversion of 100% for over 8 h and having the highest selectivity of ca. 46% to propylene due to the presence of weak Bronsted acidity.

Preparation and characterization of bimetallic catalysts supported on mesoporous silica films

Thin (300-1000 nm) mesoporous silica coatings with hexagonal and cubic mesostructure have been prepared on Pyrex@ 7740 borosilicate glass substrates by the evaporation induced self assembly assisted sol-gel route. Prior to the synthesis, a 50 nm TiO 2 layer has been deposited on the substate by atomic layer deposition from titanium tetrachloride and water to reach better adhesion of coatings to the walls of the substrate. The coatings were produced by templating a silica precursor (TEOS) with an EO x PO y EO x amphiphilic triblock copolymer (EO = ethylene oxide, PO = propylene oxide, x = 106, y = 70) at a pH of 2. A surfactant/silica ratio of 0.0076 was found to be optimal at a spinning rate of 1500 rpm to obtain the coatings with a surface area above 500 m 2 /g and a monomodal pore size distribution with a mean pore size of 6.9 nm. Mixed-metal precursor clusters [Ph 4 P] 2 [Ru 5 PtC(CO) 15 ] have been inserted into the mesoporous support. Then, the mesoporo-encapsulated clusters were activated by gentle heating in vacuo at 200°C. The average diameter of the resulting, well-dispersed, isolated and anchored bimetallic nanoparticles is 1.4 nm. By this approach, the functionality of the relatively fragile metallic clusters is mediated through the rigid inorganic framework providing protection and the 3D distribution of the catalytic function. The resulting coatings can be used in a number of fine chemicals synthesis reactions.

Metal Carbides in Fuel Cell Cathode

Moderate-temperature fuel cells are clean power generators for both stationary and mobile applications. In particular, polymer electrolyte membrane fuel cells (PEMCs) have attracted much attention due to their high gravimetric and volumetric power densities. However, due to their acidic environment, platinum-based nanocatalysts are the only feasible electrocatalyts for such systems. High cost and limited resources of this precious metal hinder the commercialization of PEMFCs. As a result, tremendous efforts are being exerted to either reduce Pt loading or substitute Pt metal with other non-noble metals. In this context, metal carbides have been extensively investigated due to their bifunctional mechanism as a catalyst as well as a catalyst support. Hence, the aim of using metal carbides is to replace carbon support since carbon suffers from corrosion problem and at the same time to reduce a substantial amount of Pt in fuel cell cathode. In this chapter, we have given an overview on metal carbides and their benefits as catalyst support for fuel cell cathode reactions.

A Mesopore-Dependent Catalytic Cracking of n-Hexane Over Mesoporous Nanostructured ZSM-5

Herein, pore size, crystalinity, and Si/Al ratio of mesoporous ZSM-5 (MFI) nanocrystals was controlled by synthesis parameters, such as surfactant concentration ([3-(trimethoxysilyl)propyl] hexa-decyl dimethyl ammonium chloride), sodium hydroxide concentrations, synthesis temperature and time. The morphology, surface structure and composition of the MFI particles was systematically investigated. More notably, the mesopore-dependent catalytic activity of ZSM-5 was evaluated by studying the cracking of n-hexane. The findings suggest the porosity has pronounced impact on the catalytic activity, selectivity and stability of ZSM-5 nanocrystals. Critical surface attributes such as nature of acid sites (Brønsted and Lewis), concentration, and strength are obtained by the infrared study of adsorbed probe molecules (pyridine) and the temperature programmed desorption. In spite of being weaker in Si/Al ratio or acidic strength, mesoporous catalysts showed more stable and efficient cracking of n-hexane suggesting that acidity seems not the predominant factor operative in the activity, selectivity and stability.

Alkali Metal Ion-Exchanged Zeolite X from Bamboo Leaf Biomass as Base Catalysts in Cyanoethylation of Methanol Enhanced by Non-Microwave Instant Heating

A series of alkali form (Na, K, Cs, and Ca) faujisite X-type zeolites were prepared from bamboo leaf ash, which was derived from bamboo agricultural waste. The XRD and SEM results revealed that the zeolite structure remained intact after ion exchange treatment. A very high degree of ion exchange (≥ 85 %) was achieved in all of the prepared zeolite samples. The zeolite samples were tested in a solvent-free cyanoethylation reaction of methanol under an instant heating environment that mimicked microwave fast heating, which was explored for the first time. The catalytic performances of the zeolite samples were well correlated with their surface basicity, which was characterised by pyrrole adsorption followed by in situ infrared spectroscopy. The CsX zeolite showed excellent catalytic performance (~97 % reactant conversion and 100 % product selectivity within 15 min), which was comparable to the microwave-assisted system and superior to the normal reflux system. The catalytic activity of the CsX zeolite was retained even after 10 cycles of reaction.