Porous siliceous materials such as zeolite and mesoporous silica are often used as the support of TiO2 photocatalyst. Control of the surface properties, shapes and structures on the nanoscale can expand their inherent properties for design of more efficient reaction systems and improved photocatalytic performance with additional functions. This review mainly describes our recent investigations on the design of TiO2-loaded porous siliceous materials for application to photocatalytic environmental purification via efficient adsorption and condensation of target organic molecules and decomposition in water and air. The compositions, surface properties, pore structures and other characteristics realized by various modification techniques are briefly summarized.
Catalytic ethanol steam reforming was investigated over Pt/CeO2 catalyst in an electric field at low temperature, and the effect of the electric field and controlling factors for the activity and selectivity were examined. With the electric field, ethanol steam reforming proceeded at temperatures as low as 423 K, at which the conventional catalytic reaction hardly proceeded. Supported platinum acted as an active site for ethanol steam reforming. Conversion of ethanol and H2 yield drastically increased with the electric field, and apparent activation energies for ethanol dehydrogenation, acetaldehyde decomposition, and acetaldehyde steam reforming were lowered by the electric field. In-situ DRIFTS measurements revealed that the adsorbed ethanol formed reactive acetate species with the electric field even at low temperature, which improved hydrogen selectivity. This process can produce hydrogen from bioethanol using less energy at low temperatures, such as 423 K, with high efficiency.
Zeolite-containing catalysts with hierarchical structures were prepared by combining microporous zeolites (beta and Y zeolite) with mesoporous matrices (silicas and silica–aluminas with large mesopores) prepared by the gel skeletal reinforcement method and a binder. Morphology of the prepared catalysts was characterized by X-ray diffraction, nitrogen adsorption-desorption, ammonia adsorption-desorption, and thermogravimetric-differential thermal analysis. Catalytic cracking of soybean oil was performed with these mixed catalysts to observe the effect of the pore size on the catalytic activity and the selectivity of products using the convenient Curie point pyrolyzer. Zeolite-containing mixed catalysts exhibited great improvements in all aspects such as maximum increase of 31 % conversion, about 10 % higher gasoline yields, and maximum decrease of 36 % coke formation in comparison with single zeolite, indicating that the presence of the matrices greatly influenced the catalytic cracking. The yields of gasoline, single branched and multi-branched hydrocarbons increased with higher conversion, indicating that increased conversion was necessary to obtain higher yields of products. In comparison of product yields at the same conversion, Y zeolite-containing catalysts exhibited the higher yields than beta (β) zeolite-containing catalysts, indicating that the larger micropore diameter of Y zeolite in the catalysts induced the increase in the gasoline fraction and promoted the isomerization to produce the bulkier products. The conversion of soybean oil increased with increasing the pore diameter for β series catalysts and the conversions were maximum for MAT(200S)-β and MAT(200SA)-β with relatively larger mesopores, indicating that the diffusion of reactants and products affected the catalytic performance. In contrast to this phenomenon, MAT(0S)-Y and MAT(0SA)-Y with relatively smaller mesopores exhibited the maximum conversions for Y series catalysts.
Precise, one-pot synthesis of end-functionalized conjugated polymers, poly(9,9-di-n-octyl-fluorene vinylene)s (PFVs), have been prepared by acyclic diene metathesis (ADMET) polymerization followed by Wittig-type coupling with aldehyde in the presence of molybdenum-alkylidene catalyst, Mo(CHMe2Ph)(N-2,6-Me2C6H3)[OC(CH3)(CF3)2]2 (Mo cat.). Further addition of Mo cat. after the ADMET polymerization was necessary for completion of olefin metathesis (with the vinyl chain end) and for exclusive end-functionalization by the subsequent coupling. Various end-functionalities could be introduced without purification or isolation by this one-pot methodology.
High mass transfer rate is one of the advantages of the micro reactor. Phenyl benzoate formation from benzoyl chloride and phenol was carried out in a micro reactor with a rectangular cross section micro reactor with three rounded channels which acted as stabilizers for parallel flow. Flow dynamics were very important for this reaction as phenyl benzoate and benzoyl chloride are easily hydrolyzed. The third phase contained phase transfer catalyst which was not soluble in the aqueous or organic phases. The third phase was present at the organic phase — aqueous phase interface and formed a barrier for separating the aqueous and organic solutions. To maintain high selectivity for phenyl benzoate, parallel flow was required. Aqueous and organic solution flow rates were varied and flow dynamics in the micro channel was observed with a microscope. Low organic solution flow rate formed parallel flow. Reaction was carried out in the parallel flow condition. Phenol mass transfer through the third phase was the rate controlling step. To increase the main reaction rate, phenol was dissolved in both the organic and aqueous solutions. Selectivity was increased under that condition. Reaction rate in the micro reactor was higher than reaction rate in the conventional stirring batch reactor.
CO2 physical absorption has great potential for greenhouse gas mitigation. CO2 physical absorption mechanisms at the atomistic level were investigated by evaluating the correlations between molecular diffusions and molecular interactions using molecular dynamics (MD) simulations for three types of CO2 loaded absorbents: diethylene glycol (DEG), triethylene glycol (TEG), and diethylene glycol dimethyl ether (DEGDME). The diffusion coefficient of DEGDME was about one order of magnitude greater than those of DEG and TEG. The radial distribution functions between CO2 molecules and solvent molecules and those between solvent molecules suggested that the interactions between the solvent molecules were significant in CO2-loaded DEG and TEG solvents, whereas the interactions between the CO2 and solvent molecules were dominant in the CO2-loaded DEGDME solvent. The difference in the molecular interactions was correlated with the absolute values of the calculated diffusivities. MD calculations are a powerful tool to investigate CO2 physical absorption mechanisms at the atomistic level.
A molecule-based kinetic model simulating main reaction behavior in residue desulfurization (RDS) was developed based on detailed composition data of heavy oils obtained from Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). In this study, a kinetic modeling approach was applied to quantitatively demonstrate the reaction pathways of heavy oils based on the structural attributes (cores, side chains and bridges) of heavy oils. Reaction behavior of cores, an important factor for RDS, was analyzed using the structure/composition data of cores during RDS as obtained from FT-ICR-MS. From the analysis, 1233 types of cores were selected as main reaction species, and a reaction network of the cores is proposed consisting of 2107 reaction pathways (hydrosulfurization/hydrodenitrogenation/aromatic-ring saturation). Activation energies of the reaction pathways of the cores were estimated from both the standard enthalpy of reaction in the cores and the quantitative structure-reactivity relationship (QSRR). The side chains and bridges of heavy oils were also modeled, and a molecule-based kinetic model was developed for RDS reaction simulation. In addition, the relationship between catalyst activities and physical properties was investigated by comparison of the kinetic models constructed for two types of catalysts.
Production of hydrocarbons from biomass, in which the hydrocarbon molecules have been included in conventional gasoline, becomes attractive, because the products will be compatible with existing gasoline supply infrastructures and can be blended in higher ratios into gasoline than ethanol. The present study proposes a gasoline-boiling-range olefin production process, which combines hexanol production from cellulose using Ir–ReOx/SiO2 and acid catalysts, and hexene production from the hexanol using dehydration catalyst (H-ZSM-5). Our previous study found that hexanol can be obtained in relatively high yield of 60 % in depolymerizing cellulose by mechanocatalysis with the aid of H2SO4, and then reacting the cellulose with hydrogen over Ir–ReOx/SiO2. The present study investigated the compositions of the hexene mixture obtained by dehydrating 1-, 2-, and 3-hexanol, and the applicability of the mixture to gasoline based on JIS specifications. About 22 vol% and ca. 7 vol% of the hexene mixture could be blended into regular gasoline in summer and winter, respectively. Therefore, the hexene mixture obtained from cellulose through this pathway is a potential biofuel.
Crude oil and natural gas may contain traces of mercury depending on the origin. Mercury contamination of oil feedstocks may cause problems in both upstream and downstream operations. Mercury also has toxic effects on human health. Therefore, mercury should be removed from oil and natural gas products at the production facility before shipping. Identification of the mercury species in hydrocarbons is very important for effective removal from oil and gas. Mercury species analysis was investigated using GC-ICP-MS. Metallic mercury analysis used various sample injection procedures for GC. Ionic mercury analysis compared Grignard (butylmagnesium chloride) with sodium tetraphenylborate agents for the derivatization technique and confirmed that both reagents provided good results. The present study optimized mercury species analysis for liquid hydrocarbons using GC-ICP-MS.