This review examines a series of studies investigating the molecular phenomena occurring on the surface of TiO₂, in the dark and under ultra violet spectroscopy (UV) irradiation, in processes intended to achieve the photocatalytic abatement of organic pollutants (e.g. phenols, VOCs, acetonitrile) of air and water. The investigation technique was fourier transform infrared spectroscopy (FT-IR), applied under simulated operating conditions, augmented with high resolution transmission electron microscopy for the elucidation of the surface structure and morphology of the TiO₂ particles. The results indicate the key role of surface hydroxyl groups as adsorbing/reacting centres (under UV irradiation) and the possibility that basic surface centres (hydroxyl groups and/or surface O²⁻ of the TiO₂ lattice) also affect the surface chemical processes.

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Methods for the storage and supply of pure H₂ are proposed based on the reduction of iron oxide with H₂ (Fe₃O₄ + 4H₂→3Fe + 4H₂O) followed by the oxidation of the iron metal with H₂O (3Fe + 4H₂O→Fe₃O₄ + 4H₂). In addition, production of pure H₂ from CH₄ is proposed based on the reduction of iron oxides with CH₄ (Fe₃O₄ + CH₄→3Fe + CO₂ + 2H₂O) and the subsequent oxidation of iron metal with H₂O (3Fe + 4H₂O→Fe₃O₄ + 4H₂). Iron oxides without other metal elements were deactivated quickly during these redox cycles due to sintering irrespective of the reductant (H₂ or CH₄). The addition of metal cations such as Al, Sc, Ti, V, Cr, Ga, Zr or Mo cations mitigated the sintering of iron oxides and/or iron metals during repeated redox cycles. The addition of metal species such as Cu, Ni, Pt and Rh promoted the reactivity of iron oxides in the redox reaction at lower temperatures. The favorable effects of the addition of these metal species on the redox of iron oxides were observed for both reduction with H₂ or with CH₄. Therefore, iron oxide modified with these cations and metals can supply pure H₂ continuously throughout these redox cycles. The favorable effects of the metal species added to iron oxides were investigated based on the local structures.

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Dry reforming of methane is a potentially important process to convert the greenhouse gases carbon dioxide and methane simultaneously to syngas (CO + H₂). The most serious problem with the dry reforming of methane is carbon deposition, so preparation parameters of the citric acid method were surveyed to prepare an active Co-MgO catalyst with low carbon deposition using design of experiment, artificial neural network and grid search. The preparation parameters such as Co loading, amount of citric acid, calcination temperature, and pelletization pressure were determined according to an L₉ orthogonal array. After 9 data sets of the parameter activity were designed and measured in a conventional pressurized fixed bed reactor, an artificial neural network was constructed. The optimum composition was determined by a grid search and verified experimentally to be active with a small amount of carbon deposition. Design of experiment combined with an artificial neural network and grid search was useful for catalyst development.

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Synthesis of liquefied petroleum gas (LPG) from methanol and/or dimethyl ether (DME) was investigated over various zeolite catalysts. H-ZSM-5 with the MFI structure was confirmed to be the optimum catalyst for selective LPG synthesis. Effects of the silica-alumina ratio in H-ZSM-5 on the methanol or DME conversion were also investigated. The conversion of methanol or DME was maximum at a silica-alumina ratio of 50 or 90, respectively. Selectivities towards LPG hydrocarbons improved with increasing silica-alumina ratio for both feeds. The correlation between catalytic performance of the selected H-ZSM-5 catalyst and kinetic factors in methanol conversion was also examined. The operating conditions for the formation of C₃-C₄ hydrocarbons were identified by optimizing gas hourly space velocity and reaction temperature as well as feed partial pressure, e.g., 20,000-30,000 h^-1, > 400°C, and > 45 kPa, with a system pressure of about 120 kPa. LPG fractional hydrocarbons could be formed selectively from methanol, DME, or a mixed feed. Addition of steam to the nitrogen used as diluent gas led to a decrease in DME conversion.

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Zeolite-filled liquid membranes were prepared by coating zeolite particles (2-3 μm) and triethylene glycol (TEG) mixture on a hydrophobic microporous membrane. Permeation experiments for the dehumidification of air were conducted using the zeolite-filled liquid membranes under reduced pressure at the permeate side. To reduce the air permeation rate to suitable levels, the membrane thickness should be over 300 μm. The dehumidification performance of the zeolite-filled membrane was comparable to the supported liquid membrane using TEG liquid. The ideal separation factor of water vapor over air was 25 for the zeolite 3A (60 wt%)-TEG liquid membrane. The present zeolite-liquid membrane has advantages in membrane preparation and durability compared to the supported liquid membrane or zeolite-filled polymer membrane.

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The photovoltaic cell using visible and near-infrared sensitization of nanocrystalline TiO₂ films by chlorophyll derivative, zinc chlorin-e₆ (ZnChl-e₆), is developed. The short-circuit photocurrent (I _SC) is 0.27 mA·cm⁻², the open-circuit photovoltage (V _OC) is 422 mV, and the fill factor (FF) of device using ZnChl-e₆ adsorbed on nanocrystalline TiO₂ film electrode is estimated to be 41.0%, respectively.

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Charcoal-supported rhodium and ruthenium catalysts were active and selective for the hydrogenation of biphenyl to bicyclohexyl at low temperature (323 K) under supercritical carbon dioxide. The conversion of biphenyl hydrogenation increased with increase in carbon dioxide pressure and hydrogen pressure. From the beginning of reaction, cyclohexylbenzene and bicyclohexyl were formed and finally >95% yield of bicyclohexyl was obtained over the both catalysts.

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