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Pure Appl. Chem., 2008, Vol. 80, No. 11, pp. 2273-2282

Catalysis at the interface of nano-oxides and nanozeolites

Kyosuke Ito, Hui Jang, Koji Sakashita and Sachio Asaoka

Faculty of Environmental Engineering, University of Kitakyushu, Kitakyushu 808-0135, Japan

Abstract: The catalysts that can efficiently hydro-reform higher n-paraffin to lower isoparaffins for environmentally friendly gasoline were studied. The catalysts were examined by the conversion of n-hexadecane, n-C16H34 to i-C6H14~i-C12H26. The tri-modally nanoporous (nanometer-size) catalysts composed of (Ni-Mo)/[γ-Al2O3], nano-oxide, and nanocrystalline zeolite have some active and selective performances because of the cooperation between (Ni-Mo)/[γ-Al2O3] and the composite of nano-oxide-nanozeolite. The (Ni-Mo)/[γ-Al2O3] component holding the skeletal isomerization activity enhances the cracking activity on the composite of nanoporous (np)-Al2O3-USY (ultra-stable Y-type zeolite) to result in i‑C6H14~i-C12H26 as the isomerization of n-hexadecane followed the cracking reaction. The catalyst composed of nanocrystalline BEA (beta-type zeolite) or MFI (ZSM-5-type zeolite) zeolite can be more activated with the nano-SiO2 than with the nano-Al2O3. The catalyst composed of the dealuminated zeolite, USY (SiO2/Al2O3 = 12) cannot be activated with the nano-SiO2 but with the nano-Al2O3. This activation depends on the SiO2/Al2O3 ratio of the USY. It is considered that the catalytic property of the three components is partially due to the novel active sites formed concertedly at the interface of the nano-oxides and the nanozeolites. The novel sites have a major role for the isomerization and cracking as the moderate and strong acids and are generated when Si-OH in the nanopores of the USY resulted from the dealumination catches Al-OH in the nano-Al2O3 to form Si-O-Al-O-Al-O-Si instead of Si-O-Al-O-Si-O-Si-O.