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Mesoporous TiO2 and mixed Ti oxides are prepared by a modified sol-gel method using a block copolymer as a mesoporous template. Calcination of the material at 400 °C for template removal is shown to induce crystallization of pure TiO2, resulting in the destruction of the original mesoporous structure and the development of larger pores (7.5 nm) as inter-particle voids. The addition of tri-, tetra- and penta-valent metals (Al, Zr and Nb) to Ti oxide in the amorphous phase in the ratio Ti : M = 1 : 2 (M = Al, Zr or Nb) increases the thermal stability of the material by elevating the crystallization temperature above that for pure TiO2. The formation of Al2TiO5, TiZr2O6 and TiNb2O7 crystal phases without phase separation is confirmed in these materials, demonstrating the homogeneous mixing of TiO2 and the additive element at the atomic level. The mixed mesoporous oxides are thermally stable at 400 °C, although the porous structure is still destroyed due to crystallization. Thus, a homogeneous mixture of Ti with another element (Al, Zr or Nb) in mesoporous amorphous Ti-mixed oxide is observed.

The pore arrangement of mesoporous tantalum oxide prepared with a block copolymer surfactant as a structure-directing agent is remarkably improved by optimizing the amounts of metal source and wate...

The synthesis of a new class of sulfuric acid-functionalized ethane-bridged, mesoporous hybrid organosilicas is reported where the propylsulfonic groups attached with ethane-bridged silica exhibited reasonable catalytic activity in esterification of acetic acid with ethanol as well as the hydrolysis of cyclohexylacetate. Materials were synthesized by co-condensation of ethane-bridged organosilane (MeO)3SiCH2CH2Si(OMe)3 with 3-mercaptopropyltrimethoxysilane (MeO)3SiCH2CH2CH2SH in the presence of octadecyltrimethylammonium chloride surfactant. Powder X-ray diffraction patterns and nitrogen sorption analysis reveal the formation of mesoporous material with uniform porosity. The maximum content of incorporated mercaptopropylsilane in the mesoporous framework obtained was 3.45 mmol g−1. The thiol (–SH) moieties of mercaptopropyl groups that protrude into the pore channels are readily accessible for further oxidation. The surface moieties functionalized with propylsulfonic groups (–CH2CH2CH2–SO3H) were generated by the controlled oxidation of propylthiol surface groups using concentrated HNO3. A maximum acid exchange capacity (acid–base titration methods) of 1.38 H+ mmol g−1 was achieved after oxidation. Further, the materials were characterized using elemental analysis, FT-IR, 29Si and 13C MAS-NMR, transmission electron microscopy and TGA. Two probe reactions, the esterification of acetic acid with ethanol and its reverse the hydrolysis of cycloacetonate, showed the significance of the material in catalytic applications. The catalytic results showed the esterification activity is comparable to that of commercial Nafion-H and also the involvement of hydrophobic nature of the material in the hydrolysis reaction.

An ordered (2D-hexagonal) mesoporous Mg and Ta mixed oxide (Mg−Ta oxide) is successfully prepared. The mesoporous Mg−Ta oxide is stable after calcination at 773 K for 30 h, and has a BET surface ar...

The adsorption of 2-methylalkanes (propane, butane and pentane) onto ferrierite zeolite was studied by infrared (IR) spectroscopy at temperatures below room temperature. It was found that 2-methylpropane molecules penetrate into micropores only partially, and that only a small fraction of the acidic OH groups available in the micropores interact with the alkyl groups of 2-methylpropane. The interaction is therefore considered to represent interaction between the methyl groups and OH groups located close to the entrance of the micropores. Increasing the carbon number of the main alkyl chain of 2-methylalkanes resulted in a proportional increase in the fraction of acidic OH groups interacting with alkyl groups. Infiltration of n-alkane molecules into the micropores of ferrierite therefore appears to be hindered by methylation of the carbon at the second position. In general, stability was achieved when the longest alkyl chain had entered the micropores of ferrierite, allowing the pore length of ferrierite to be estimated from the extrapolated length of the main alkyl chains. The estimated length of up to 30 nm is consistent with SEM observation.

The isotope-exchange reaction between molecular D2 and OH species on bare (b-) and modified with adsorbed formate (f-) and methoxy (m-) ZrO2 has been studied. On the b-ZrO2, the reaction rate was proportional to PD21/2, suggesting that the rate-determining step is the migration of D atoms. The initial activation energies (E‡) were 35 and 41 ± 4 kJ mol–1 for terminal (t-) and bridging (b-) OH groups, respectively, and increased as the reaction progressed, indicating the heterogeneity of the surface activation barrier for migration of D atoms. The kinetics of the exchange reaction on f- and m-ZrO2 was found to be different from that of b-ZrO2.

The adsorption of H2 and D2 at various temperatures and the isotope effect have been studied in detail over a ZrO2 catalyst by means of FTIR. Four different types of adsorbed hydrogen were observed as follows: (1) molecularly adsorbed hydrogen, H2(a), was observed below 173 K and was easily desorbed by evacuation; (2) homolytic dissociative adsorption produces Zr[graphic omitted] species was observed below 373 K and was stable below 178 K; (3) heterolytic dissociative adsorption which forms OH and ZrH was observed in the temperature range 223–373 K and the isotope effect of adsorption between H2 and D2 was also found; (4) the adsorption which generates two OH bands at 3778 and 3668 cm–1 takes place above room temperature. For the heterolytic dissociative adsorption of H2 and D2, both the kinetic and the equilibrium isotope effects were observed. The magnitude of these isotope effects is in good agreement with the values calculated via IR data.

Two kinds of methoxide species formed from methanol adsorbed on MgO were observed by infrared spectroscopy.

Infrared active dinitrogen band was observed at 2341 cm−1 on a ZrO2 surface at 300 K. These species disturb the dissociative adsorption of hydrogen on ZrO2.

An ion-exchangeable thin film which has the layered structure of K4Nb6O17 was prepared from a suspension of fine particles of K4Nb6O17. The superfine particles which were obtained by wet grinding were coated onto a substrate, and they were calcined between 873 and 1073 K. Crystallization of the fine particles by calcination was observed by XRD, SEM, and AFM, and very flat crystals of ∼500 nm with the b-axis perpendicular to the substrate surface were obtained by calcination at 1027 K. The obtained thin film had a layered structure similar to that of the original K4Nb6O17 powder. Furthermore, it had ion-exchange properties which enabled the exchange of interlayer cations from potassium to others without destroying the layered structure.

The adsorption and reaction of H2, CO, CO2, OH(a)+ CO(g) and CO2(a)+ H2(g) have been studied in detail by infrared spectroscopy. Hydrogen is dissociatively adsorbed to form the OH and the Zr—H species and CO is weakly adsorbed as the molecular form. The infrared spectrum of adsorbed species of CO2 over ZrO2 shows three main bands at ca. 1550, 1310 and 1060 cm–1 which can be assigned to the bidentate carbonate species. The reaction of OH(a)+ CO(g) at 373 K gave rise to formate and bidentate carbonate species, and after having introduced hydrogen onto this system at 473 K, methoxide species appeared. When hydrogen was introduced over CO2-preadsorbed ZrO2, formate and methoxide species also appeared. It is concluded that the formation of the formate and methoxide species results from the hydrogenation of bidentate carbonate species.