The combinatorial method and high throughput experimentation have been applied to catalysis development in the last decade. Here we describe equipment for catalyst preparation, catalysis evaluation and product analysis with a gas sensor system. High throughput experimentation using these devices has allowed us to optimize catalyst composition with stochastic methods such as the genetic algorithm. The improvement of propane selective oxidation catalysis is described. High throughput experimentation allowed the construction of a database for elemental reactions. We have developed novel catalysts for ethanol steam-reforming catalysts and a dimethyl ether steam-reforming catalyst by combining good catalysts for each elemental reaction. Our new concept of "Materiomics" is introduced as a promising method for material science based on combinatorial technology.
Titanium dioxide photocatalysts are promising substrates for photodegradation of pollutants in water and air, but show photocatalytic activities only under UV light. To utilize a wider range of incident wavelengths such as solar light, development of photocatalysts active under visible light is very important. Chemically modified titanium dioxide photocatalysts were prepared containing anatase phase with S (S4+) substituted for some lattice Ti atoms or N substituted for some lattice O atoms. These catalysts showed strong absorption of visible light and high activities for degradation of 2-propanol in aqueous solution and partial oxidation of adamantane under irradiation at wavelengths longer than 440 nm. The oxidation states of the S and N atoms incorporated into the TiO2 particles were determined to be mainly S4+ and N3− from XPS spectra, respectively. The photocatalytic activities of S- or N-doped TiO2 photocatalysts with adsorbed Fe3+ ions were markedly improved for oxidation of 2-propanol compared to those of S- or N-doped TiO2 without Fe3+ ions under a wide range of incident wavelengths, including UV light and visible light. The photocatalytic activity reached maximum with 0.90 wt% Fe3+ ions adsorbed on S-doped TiO2, and 0.36 wt% Fe3+ ions on N-doped TiO2. Furthermore, redox treatment of S- or N-doped TiO2 photocatalysts with adsorbed Fe3+ ions by reduction with NaBH4 followed by air oxidation resulted in further improvements in photocatalytic activities. In this case, the optimum amounts of Fe3+ were 2.81 and 0.88 wt% on the surfaces of S- and N-doped TiO2 photocatalysts, respectively.
Hydrothermal desulfurization was evaluated for the upgrading of bitumen in supercritical water with alkali, based on the formation and decomposition of thiophene derivatives. In the alkaline hydrothermal treatment of bitumen at 430°C and 30 MPa with KOH, drastic reduction of sulfur content and visbreaking occur in the first several minutes, followed by relatively slow reactions. This study investigated the desulfurization at the latter stage. The results can be summarized as follows: (1) In the alkaline hydrothermal treatment of bitumen, benzothiophenes (BTs) and dibenzothiophenes (DBTs) were formed first, and subsequent decomposition of BTs resulted in the overall desulfurization of bitumen. (2) Alkali was consumed to form BTs and DBTs by decomposing bitumen. (3) Amounts of each BT and DBT formed were influenced by the type of of bitumen, although the same BTs and DBTs were formed. (4) Types of alkyl BTs detected represented about a half of the theoretically possible isomers, and the carbon number of the alkyl group(s) was mostly three or less. (5) BTs were easily decomposed in comparison to DBTs and much smaller amounts of DBTs were formed, so that the desulfurization mainly progressed via BTs. The sulfur content of remaining DBTs in the upgraded oil was less than 0.3 wt%.
Nickel-catalyzed decomposition of methane was examined in the presence of carbon dioxide cofeed using a thermogravimetric apparatus. Methane was decomposed to hydrogen and multi-walled carbon nanotubes as in the decomposition of pure methane. However, the dry-reforming reaction, gasification of the carbon species with carbon dioxide, and the water gas shift reaction took place simultaneously, and carbon monoxide and water were also formed. Deactivation of the catalyst took place slowly in the presence of carbon dioxide cofeed, and the carbon yield increased with higher partial pressure of carbon dioxide in the feed gas. However, further increase in the carbon dioxide concentration in the feed gas reduced the carbon yield. The most interesting point is that the dry-reforming reaction continued even after carbon formation apparently ceased. Mechanisms for the deactivation of the catalysts are discussed.
Fuel oils were prepared by hydrocracking/isomerization of Fischer-Tropsch waxes followed by fractionation of product oils. The correlation between the operation conditions and the average molecular structures of fuel oils, and the effect of the average molecular structure of the gas oil fraction on the diesel fuel properties were investigated. The iso-/n-paraffin ratio increased with increased 360°C+ conversion in the gas oil and bottom fractions, increased to a lesser extent in the kerosene fraction, and remained almost constant in the naphtha fraction, regardless of the severity of the hydrocracking/isomerization reaction. Average branching numbers of the isoparaffins were determined by 13C-NMR analysis and compared with the severity of the hydrocracking/isomerization reaction. Average branching numbers of the kerosene and gas oil fractions were nearly constant at approximately 1.3 and 2.0 branch/molecule respectively, but were influenced by 360°C+ conversion in the bottom oil fraction. A linear relationship was obtained between average carbon number and average branching number, suggesting that average branching number can be determined by average carbon number regardless of the severity of the hydrocracking/isomerization reaction. Correlation of the molecular structural parameters of the gas oil fraction with fuel properties such as viscosity, ignition property, and cold flow property showed that the molecular structural formula, (average carbon number) × (n-paraffin ratio)A, had a good linear correlation with the kinematic viscosity (30°C), cetane index, and cold flow plugging point for A = 0.0, 0.02, and 0.05. The molecular structure of the naphtha fraction was also investigated to obtain information such as the position of branching.
Photochemical synthesis of methanol from formaldehyde was evaluated with alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae and NAD+ photoreduction by the visible light photosensitization of zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS) in the presence of triethanolamine (TEOA) as an electron-donating reagent. Irradiation of a solution containing ZnTPPS, methylviologen (MV2+), NAD+, diaphorase (5 units) and TEOA in potassium phosphate buffer with visible light resulted in formation of NADH increasing with time. NADH was not formed in the absence of any one of the five components, TEOA, ZnTPPS, MV2+, diaphorase and NAD+. The reduction ratio of NAD+ to NADH reached about 60% after 180 min irradiation. Irradiation of a solution containing formaldehyde, ZnTPPS, MV2+, ADH, diaphorase and TEOA with visible light resulted in formation of methanol. The formaldehyde concentration decreased with formation of methanol. This result indicates that the photochemical synthesis of methanol from formaldehyde depends on ADH and NADH produced by the photosensitization of ZnTPPS. The concentration of methanol was 0.38 μmol·dm−3 after 3 h irradiation under conditions of ZnTPPS (1.0 μmol·dm−3), MV2+ (0.1 mmol·dm−3), NAD+ (0.1 mmol·dm−3), diaphorase (5 units), TEOA (0.3 mol·dm−3), formaldehyde (16 μmol·dm−3) and ADH (25 units).
Carboxylation of 2-naphthol with carbon dioxide in aprotic polar solvents proceeds at the lower temperature in comparison with the Kolbe-Schmitt reaction. The carboxylation of 2-naphthol with carbon dioxide in anisole, an aprotic polar solvent, was investigated to assess the effect of the reaction conditions such as temperature and time on the product yield and selectivity. The carboxylation of 2-naphthol attained high yield at 373 K, and yield decreased at higher temperatures. The carboxylated product consisted only of 2-hydroxy-1-naphthoic acid at 373 K, but the selectivity for 2-hydroxy-1-naphthoic acid decreased and the selectivity for 3-hydroxy-2-naphthoic acid increased at higher temperatures. In addition, 6-hydroxy-2-naphthoic acid formed at 543 K. The selectivity for 2-hydroxy-1-naphthoic acid decreased, and that of 6-hydroxy-2-naphthoic acid increased as the reaction time increased at 543 K. Thermal rearrangement of 2-hydroxy-1-naphthoic acid to 3-hydroxy-2-naphthoic acid and 6-hydroxy-2-naphthoic acid probably proceeds simultaneously with decarboxylation of 2-hydroxy-1-naphthoic acid.
A model naphtha and benzothiophene-1,1-oxide (BTDO) were used to evaluate five commercial adsorbents in order to select a high-performance adsorbent for the separation of sulfur oxides generated in oxidative desulfurization processes. In preliminary experimental runs, the adsorbents were examined to determine their ability to reduce the sulfur concentration in the feed from 14 ppm to 1 ppm using 0.2 wt% adsorbent. Three of the five adsorbents, silica gel (SIL), active carbon-impregnated silica gel (ACSIL), and molecular sieve 13X (MS) met this criterion, while active carbon (AC) and silica-alumina type (NBD) adsorbents did not. Screening of the three adsorbents that passed the preliminary test showed that SIL had the highest throughput, which exceeded 1000 g/g-adsorbent, in reducing the sulfur concentration in model naphtha from 1 ppm to 10 ppb. ACSIL and MS could cope with only about 600 g/g-adsorbent.
The high-throughput screening reactor for high pressure oxidative reforming of methane requires a new simple syngas detector operating under high pressure, because the number of parallel reactors with the conventional detection system is limited by the complexity of the pressure reducing unit. Reduction of metal oxide with color change was applied to the detection system. Copper oxide was supported on the filter made of alumina, and the filter was placed underneath the catalyst bed. After oxidative reforming of methane was carried out under 1 MPa at 650°C, color change of spots from dark brown to light brown was observed just under the catalyst caused by copper oxide reduction. The color change disk can be used to detect hydrogen formation ability of the reforming catalyst under pressure.