This review describes the olefin polymerization behavior of bis(phenoxy-imine) and bis(phenoxy-ketimine) early transition metal complexes (a.k.a. FI catalysts). FI catalysts display unique catalytic properties due to the coordination of a pair of non-symmetric, electron-withdrawing and reactive [O−, N] chelating ligands (FI ligands). Moreover, FI ligand structures can be readily tailored from the electronic and steric point of view. Thus, FI catalysts in combination with appropriate activators are capable of producing a wide variety of unique olefin-based materials (FI polymers). Specific examples of FI polymers include selective vinyl-terminated polyethylenes, ultra-high molecular weight linear polyethylenes, well-defined and controlled multimodal polyethylenes, ethylene/polar monomer copolymers, highly syndiotactic and isotactic polypropylenes with exceptionally high Tms, ethylene- and propylene-based end-functionalized polymers, a wide array of polyolefinic block copolymers from ethylene, propylene and higher α-olefins, and ultra-fine non-coherent polyethylene particles. These FI polymers display new or enhanced material properties, and to this end, several FI polymers are now entering the industrial phase.
A detection method of hydrogen leakage locations has been proposed and characterized. Platinum-supported tungsten trioxide (Pt/WO3) was utilized as a sensing material whose color changes from semi-transparent to blue in the presence of hydrogen gas. The Pt/WO3 thin film was coated on the glass plate by sol-gel technique and evaluated with the exposure to hydrogen gas squirting out of the test nozzle at the different leak rate. The colored area was determined with binary image processing of the differential picture before/after the hydrogen exposure. The colored area expanded quickly and reached to an plateau level after 30 s, suggesting the reaction took place quite fast even at room temperature. Furthermore, the colored area in the steady state became larger as the hydrogen leak rate increased. This relationship and response kinetics was significantly affected by the angular orientation of the imaging device. The proposed method would be applicable to the inspection of various equipments using hydrogen, such as fuel cells, hydrogen storage tanks and hydrogen engine systems.
Ethanol distributions between selected organic and aqueous phases were measured for recovery and concentration of bioethanol from fermented solution. The strategy of solvent selection was based on the background of biofuel production, and m-xylene was selected as the primary solvent and capric acid, 1-hexanol and 2-ethyl hexanol secondary solvents were utilized to enhance the ethanol solubility. The extraction performance was evaluated through the liquid-liquid equilibrium. m-Xylene showed low distribution coefficient of ethanol and high separation selectivity of ethanol relative to water. All secondary solvents increased the distribution coefficient. The separation selectivity was greatly reduced by capric acid, but was similar for 1-hexanol and 2-ethyl hexanol. The two phase region was smaller for 1-hexanol than for 2-ethyl hexanol, chosen as the best secondary solvent. Examination of the effects of 2-ethyl hexanol concentration in the solvent found that a small amount of 2-ethyl hexanol could enhance the distribution coefficient and maintain the separation selectivity constant. The measured liquid-liquid equilibria were estimated with the ordinary and modified UNIFAC methods. Both methods could predict the liquid-liquid equilibrium behaviors of the measured systems, but the modified UNIFAC method could show a better correlation. However, the water concentrations in the organic phases were estimated to be larger than the measured values if the measured concentrations were very low.
Methane conversion by the dielectric-barrier discharge plasma method (DBD) was compared with our previous findings for the microwave plasma method (MW). The power (Pw), initial pressure (P0) and flow rate (F0) affect the collisions between electrons and molecules, so the dissociated radical species may change. Changing the Pw resulted in methane conversion (XCH4) of DBD as high as 9.6% at 44 W, but much lower than the XCH4 of MW (93.8%). Ethane was the main product (60%) of DBD. Propane, methylpropane and butane were also produced. Therefore, DBD promoted homologation. Acetylene was the main product (90%) of MW. Therefore, MW promoted dehydrogenation. Changing the P0 resulted in lower XCH4 of DBD than XCH4 of MW. Propane selectivity was increased with higher P0, and butane was produced at 101.4 kPa in DBD. Acetylene was the main product irrespective of P0 in MW. Changing the F0 resulted in lower XCH4 of DBD. XCH4 of MW increased until 0.8 mmol/min and remained constant after 1.26 mmol/min. However, changing the F0 showed no effect on product selectivity. Therefore, methane conversion may be caused by the pulse-plasma effect under pressure. The conversion of ethane, ethylene and ethane/hydrogen was investigated to clarify the reaction mechanism of the methane conversion by DBD. Methane, acetylene, propane and butane were produced irrespective of the starting gases. Ethylene was produced from starting ethane. Ethane was produced from starting ethylene. The process of methane decomposition is considered to occur as follows. Firstly, methane converts to ethane. Secondly, ethane converts to propane. Finally, butane is produced from coupling of CH3 and C3H7 obtained from propane, and butane is produced from coupling of C2H5. In contrast, dehydrogenation is slightly promoted.
Cu/Ce1−xZrxO2 (x = 0-1) was prepared by a coprecipitation-decomposition method using NH3 · H2O as precipitant (to avoid residues of alkali metals), followed by a boiling process to eliminate NH3 and decompose [Cu(NH3)4]2 + complex. Then Cs was introduced to Cu/Ce1−xZrxO2 by the impregnation method. The prepared CsCu/Ce1−xZrxO2 catalysts (Cs: 1.0 wt%; Cu: 20 wt%) were used to catalyze the synthesis of mixed alcohols in a high-pressure fixed-bed flow reactor under reaction conditions of T = 573 K, P = 3 MPa, H2/CO = 2/1, and GHSV = 2400 h−1. CsCu/CeO2 showed higher CO conversion than the industrial catalyst CsCu/ZnO due to the reducibility of the CeO2 support. Moreover, the STY of higher alcohols over CsCu/CeO2 was much higher than that over CsCu/ZnO due to the oxygen storage capacity of the CeO2-based compounds. Introduction of Zr4 + ions into CeO2 lattices increased the reducibility and the oxygen storage capacity of the CeO2-based compounds, so the STY of higher alcohols over CsCu/Ce0.8Zr0.2O2 was larger than that over CsCu/CeO2. CO conversion increased but selectivity for methanol decreased with higher reaction temperature over CsCu/Ce0.8Zr0.2O2. The selectivity for higher alcohols was maximum at 573 K over CsCu/Ce0.8Zr0.2O2. Both CO conversion and selectivity for higher alcohols increased with higher reaction pressure over CsCu/Ce0.8Zr0.2O2 for the synthesis of mixed alcohols from syngas.
CP-MS41 was synthesized by hydrolysis of tetraorthosilicate, as a silicon source, with 3-chloropropyltriethoxysilane as an organosilane using cetyltrimethylammonium bromide as a template. TEA-CP-MS41 was synthesized by immobilization of triethylamine on the mesoporous MCM-41 and was dispersed in organic liquid as a mesoporous catalyst for the reaction between carbon dioxide and phenyl glycidyl ether (PGE). Carbon dioxide was absorbed into the PGE solution in a stirred batch tank with a planar gas-liquid interface within a range of 0-2.0 kmol/m3 of PGE and 333-363 K at 101.3 kPa. The measured values of absorption rate were analyzed to obtain the reaction kinetics using the mass transfer mechanism associated with the chemical reactions based on the film theory. The overall reaction of CO2 with phenyl glycidyl ether (PGE), which is assumed to consist of two steps: (i) A reversible reaction between PGE (B) and catalyst of TEA-CP-MS41 (QX) to form an intermediate complex (C1), and (ii) irreversible reaction between C1 and CO2 to form QX and five-membered cyclic carbonate (C), was used to obtain the reaction kinetics through the pseudo-first-order reaction model. Polar solvents such as N, N-dimethylacetamide, N-methyl-2-pyrrolidinone, and dimethyl sulfoxide affected the reaction rate constants.
Titanium dioxide (TiO2) is the most widely used metal oxide for environmental applications, cosmetics, paints, electronic paper and solar cells, so demand is increasing rapidly. TiO2 can be produced from Ti-flocculated sludge, which is superior to the commercially available TiO2 in terms of photocatalytic activity and surface area. This process also reduces the amount of sludge for disposal after waste water treatment. In this study, flocculation of dye wastewater using TiCl4 and Ti(SO4)2 coagulants was investigated to prepare TiO2 nanoparticles from Ti-salt flocculated sludge. Both coagulants showed high flocculation performance in removing organic matter (77%), total nitrogen (76%) and total phosphorus (95%) from dye wastewater. Therefore, Ti-salt coagulants can be used in dye wastewater treatment. Incineration of the Ti-salt flocculated sludge at 600°C was performed to produce TiO2 nanoparticles. Detailed characteristics of the TiO2 nanoparticles were investigated in terms of X-ray diffraction, surface area, functional group, microscopy and photocatalytic activity. The TiO2 produced from TiCl4 and Ti(SO4)2 flocculated sludge (DCT and DST, respectively) had only the anatase structure with 20 nm particle size. The specific area of DCT and DST was 71 and 69 m2/g, respectively. Both DCT and DST were doped with carbon, silicon and sodium. Both exhibited high photocatalytic activity with complete degradation of acetaldehyde within 80 min under UV irradiation. These findings imply that TiO2 nanoparticles produced from wastewater sludge have significant potential for applications such as photocatalyst bricks, ceramic filters for air/water purification, and selective catalytic reduction catalysts.
Ni2P catalysts supported on SiO2 and SBA-15 were successfully prepared by temperature-programmed reduction (TPR), and the effect of Ni2P dispersion on the 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS) activity was studied. The surface areas of the samples varied from low (Ni2P/SiO2, 127 m2 · g−1) to high (Ni2P/SBA-15, 283 m2 · g−1), with corresponding Ni2P average crystallite sizes decreasing from 20 to 5 nm. Extended X-ray absorption fine structure (EXAFS) studies were used to confirm the formation of Ni2P phase. Transmission electron microscopy (TEM) analysis showed that the SBA-15-supported Ni2P sample consisted of nanoparticles, which were probably located in the mesoporous channels or the external surfaces. The catalytic activity for HDS was measured at 613 K and 3.1 MPa in a three-phase fixed bed reactor using a model liquid feed containing 500 ppm S as 4,6-dimethyldibenzothiophene, 1000 ppm S as dibenzothiophene, 200 ppm N as quinoline, and 1% aromatics as tetralin in tridecane solvent. The Ni2P/SBA-15 catalyst had a steady-state HDS conversion of 99% at 613 K, much higher compared to the Ni2P/SiO2 catalyst with a HDS conversion of 54%. These results are probably due to the enhanced dispersion of the Ni2P particles on the high surface area SBA-15 support, as confirmed by CO chemisorptions, TEM and EXAFS analysis.
The catalytic activity of iron oxide composite catalyst (ZrO2–Al2O3–FeOx) was investigated for converting aromatic compounds derived from plant biomass into useful aromatics. Catalytic cracking of lignin constituent-related di-aromatics such as diphenyl ether, diphenyl methane, and 2-benzyloxyphenol, and mono-aromatics such as guaiacol, acetophenone, and 1-phenyl-1-propanol was carried out over ZrO2–Al2O3–FeOx. The catalytic reactions were conducted in a fixed-bed reactor at 773 K under atmospheric pressure. Diphenyl ether and diphenyl methane were stable, whereas 2-benzyloxyphenol was thermally decomposed, followed by the production of toluene and phenol over ZrO2–Al2O3–FeOx. Guaiacol and acetophenone were selectively converted into 54 C-mol% of phenol and 29 C-mol% of benzene, respectively. The methoxy and carbonyl groups were decomposed into gaseous products mainly consisting of CO2, whereas dehydration of the aliphatic hydroxyl group in 1-phenyl-1-propanol mainly occurred to produce 1-phenyl-1-propene. ZrO2–Al2O3–FeOx catalyst is effective for degrading alkyl ether bonds between aromatic rings, and the ring substituent methoxy and carbonyl groups.
Removal of phenol by wet air oxidation was conducted with 1 wt% Pt/Al2O3 catalyst in a batch reactor and in a continuous flow fluidized bed reactor with air lift tube operated at 423 K and 1.4 MPa. After 60 min in the batch reactor with initial phenol concentration of 1000 mg/l, almost complete conversion into CO2 and H2O was achieved. Pt/Al2O3 catalyst deactivation was observed during the wet oxidation reaction. TEM, EDX, XPS and TPO analyses showed the deactivation was caused by formation and deposition of carbonaceous materials on the catalyst surface. TEM of the deactivated Pt/Al2O3 showed formation of filamentous materials, which linked Pt particles, and some Pt particles were completely encapsulated by deposited material. XPS analysis showed that the carbonaceous materials on the catalyst consisted of four different morphologies (C1, C2, C3, C4). As the wet oxidation proceeded, the C1 peak increased gradually with reaction time, whereas the C2 and C3 peaks passed through maxima. At around the C2 and C3 peak maxima, the C4 peak began to appear and increased continuously up to 10 h reaction. This result indicates that at least two carbonaceous materials of C2 and C3 were transformed morphologically into C4 material. The broad profiles of CO2 formation from the TPO experiment implied that at least two types of carbon deposits were oxidized at different temperatures, one type on Pt particles, the other type on Al2O3. The carbonaceous deposit was formed on Pt particles and migrated continuously onto the support. The continuous flow fluidized bed reactor showed very stable wet oxidation performances in the presence of the air lift tube. The air lift tube was important in continuously regenerating the deactivated catalyst. The accumulated carbon deposits were reduced drastically by the action of the air lift tube.
To suppress total oxidation and increase the CO selectivity of high-pressure oxidative reforming of methane, preparation parameters of K−Ni/α-Al2O3 catalyst were optimized. The target preparation parameters were the main factors affecting CO selectivity such as calcination temperature of γ-Al2O3, and NiO and K loadings. Parameters were designed by L9 orthogonal array containing three factors and three levels, and the catalysts were prepared by the sequential impregnation method with Ni loaded prior to K. Activity test of the L9 catalysts was conducted at 1 MPa and 650°C. The relationship between the preparation conditions and CO selectivity of the L9 catalysts obtained from the experimental results was analyzed using a radial basis function network (RBFN). The CO selectivity was expressed by the RBFN as functions of the catalyst preparation parameters. A grid search, where all combinations of the preparation conditions were input to the RBFN, was conducted to identify the optimum conditions of catalyst preparation for the highest CO selectivity. The predicted catalyst was 1.3 wt% K−14 wt% NiO on α-Al2O3 calcined at 1195°C. Surface NiO morphology was estimated by fractal dimension of Ni distribution in the EPMA image, and X-ray diffraction (XRD) and BET surface area measurements were conducted using the L9 catalysts. These characters were correlated to the catalyst preparation conditions by RBFNs, and the grid data were calculated on the RBFNs. These grid data were analyzed by multivariate analysis to calculate the correlations between CO selectivity, fractal dimension, NiO crystalline parameters, and BET surface area. CO selectivity was expressed by a linear combination of the fractal dimension and NiO crystalline parameters. Another multivariate analysis suggested that fractal dimension was also expressed by primary expression of the NiO diffraction angle, so that the preparation conditions, especially the K loading, affect the NiO diffraction angle. Therefore, K addition was suggested to affect the NiO lattice to modify the surface morphology of NiO resulting in change of CO selectivity.