Improvement of catalysts for the steam reforming of tar derived from the pyrolysis of biomass is needed in terms of activity, stability, and resistance to coke deposition. Ni and Co are known to be active components for the steam reforming reaction, and one effective method to improve the catalytic performance is the alloying of the active metal with another suitable metal. The development of Ni–Fe, Ni–Co, and Co–Fe alloy catalysts is described. The relationship between the promoting effect of alloy formation and the characterization of alloy particles is introduced. The catalytic performance of alloy particles is greatly influenced by the properties such as components, compositions, crystal structures, uniformity, and so on. In particular, utilization of hydrotalcite-like compounds as the catalyst precursors can produce alloy particles with uniform composition as well as higher catalytic activity than those prepared by the conventional impregnation method, demonstrating an effective method for preparing excellent alloy catalysts.
A wide range of microorganisms, from photoautotrophs to heterotrophs, can generate molecular hydrogen (H2). The hyperthermophilic archaeon, Thermococcus kodakarensis KOD1, is one such organism, an anaerobic heterotroph that grows optimally at 85 °C. The H2-producing potential of this organism was evaluated in a complex medium supplemented with either pyruvate or starch. In a continuous culture using pyruvate, the H2-production rate (per gram dry weight per hour) was 59.6 mmol g−1 h−1 at a dilution rate of 0.8 h−1, indicating that T. kodakarensis exhibits one of the highest H2-production rates among microorganisms so far examined. Our efforts are now focused on understanding the mechanisms governing H2 production in this organism, which should also lead to strategies to further enhance productivity. The T. kodakarensis genome contains three gene clusters that encode [NiFe]-hydrogenase orthologs, Hyh, Mbh and Mbx. Analysis of the phenotypes of individual gene disruption strains revealed that Mbh is the hydrogenase responsible for H2 evolution, whereas Hyh and Mbx participate in H2 consumption and H2S production, respectively. Therefore, enhancing the function of Mbh and eliminating the function of Hyh should be effective in developing a strain with increased H2-generation capacity.
Hydrogen gas as a fuel has the potential to alleviate the threat of global climate change and help to avoid various undesirable effects caused by the mass consumption of fossil fuel. Photocatalytic water splitting has been widely studied as a potential method to produce H2 from renewable solar energy. Photocatalysts that can operate under visible light irradiation (λ>400 nm), which forms the main part of sunlight, are highly desirable. Successful two-step water splitting systems (Z-scheme) that operate with or without a reversible redox couple have been reported for the application of visible light-driven photocatalysts. The Z-scheme system, which mimics photosynthesis in green plants, consists of two photocatalysts, one for H2 evolution, and the other for O2 evolution. The Z-scheme process can utilize a wider range of visible light than the conventional one-step excitation system because the energy required to drive each photocatalyst can be reduced. This review presents recent research progress in the development of visible light-driven photocatalytic materials with a focus on Z-scheme water splitting.
A microreactor technology, in which a microchannel is used as a catalytic reaction field in order to supply hydrogen to a small polymer electrolyte fuel cell (PEFC) for portable electronic devices, was described. The reduction of heat loss in the microreactor is the primary requirement for improving system efficiency, since heat release in microreactors is higher than in conventional reactors due to the increased specific surface area. Therefore, the methanol steam reforming, operated below 300 °C, is an appropriate process for the hydrogen production using the microreactor. First, the high-performance Cu/ZnO/Al2O3 catalyst for methanol reforming at low temperature was developed under the optimized preparation condition. The miniaturized methanol reformer was then developed to utilize this Cu/ZnO/Al2O3 catalyst. The length of the microchannel was determined based on one-dimensional mass and heat balance analyses. The microreactor was fabricated from silicon and glass substrates using a number of microfabrication techniques. Methanol reforming using this reactor has been demonstrated to reach the levels necessary to power a 1 W-class small PEFC system. The multilayered integrating the miniature methanol reformer with a CO remover, a catalytic combustor as a heat source for methanol reforming, vaporizers, and several necessary functional elements for hydrogen production has also been successfully fabricated. Finally, the microreactor system has been demonstrated to produce hydrogen at a rate sufficient to generate electrical power of 2.5 W.
AE diagnostics are widely used as a tool to conduct surveys and experiments in order to understand the characteristics of corrosion damage in the bottom plates of above-ground oil tanks worldwide. However, AE diagnostics have not yet become common as an on-site application at Japanese refineries because the degree of corrosion rate of tank bottom plates has been modest (<0.1 mm/year) and the conventional methods of corrosion management which use data collected periodically under the fire defense law, are widespread in the industry. On the other hand, the overall plate thickness measurement method of tanks using non-destructive inspection technology called Ultrasonic Testing (UT) has recently become popular. UT has been used to measure the thickness of above-ground tank bottom plates undergoing planned maintenance, so has enabled assessment of corrosion damage. In addition, the accuracy of the diagnostic technique using AE has been improved by advances in the specification of source location through increased accuracy in collecting the predominant AE signals based on improved denoising techniques. Overall UT measurement instead of discrete UT measurement has enabled confirmation of the accuracy of AE and assembling databases has enabled quantative evaluation of AE. Accordingly, we have improved the old principles of testing and evaluation methods, and developed a new method for detecting corrosion rate in tank bottom plates in service. By using the improved AE technique, we were able to obtain a good correlation between the data collected by the method and the status of corrosion rate in tank bottom plates. We describe the AE evaluation technique and we present the recommended practice for AE diagnostics.
Cracked kerosene, aqueous solution of polyoxyethylene sorbitan monooleate (Tween80), and hexane were used as the feed oil, membrane solution, and solvent, respectively. A baffled stirred vessel was used as the permeator. The aromatic components could selectively permeate through the emulsion liquid membrane and the yields of aromatic components were much larger than those of alkane components. The mass transfer rates of aromatic components were less affected by membrane breakage, and the permeation of aromatic components through the emulsion liquid membrane was controlling relative to the overall mass transfer. The overall volumetric permeation coefficients of total aromatic components were ten-fold more than those of total alkane components. The overall volumetric permeation coefficients were affected by the stirring velocity and surfactant mass fraction in the membrane phase. The stirring velocity was important for the dispersion of the emulsion phase in the extract phase and the specific surface area should increase with the stirring velocity. The mass fraction of surfactant in the membrane phase should be appropriately adjusted to achieve larger overall permeation coefficient. The separation selectivity of total aromatic components relative to total alkane components reached more than 10, similar to the previous results of batch liquid-liquid extraction measurements with sulfolane solvent.
Rh/CeO2 catalysts were investigated for automotive catalysts prepared by a supercritical CO2 impregnation technique. Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for the analysis of the Rh loading, Rh structure, and the morphology of the particles, respectively. Results of TEM and XRD showed Rh particles are highly dispersed on CeO2 surface, and Rh/CeO2 after calcination were prevented aggregation of CeO2. OSC of Rh/CeO2 prepared by supercritical impregnation method was higher than those of conventional catalysts. The catalytic tests for three way catalysts (TWC) showed high CO oxidation activity obtained using Rh/CeO2 prepared by supercritical impregnation. Thus, it was concluded that supercritical CO2 impregnation technique can improve OSC and TWC activity.
Residual feeds to the RFCC process could be well upgraded by catalyst containing FAU (USY) zeolite with higher hydrogen transfer activity, resulting in lower bottom and higher gasoline yields. However, the hydrogen transfer reaction has been shown to have negative aspects among the various reaction elements occurring simultaneously in the catalytic cracking process, because octane loss or coke formation were accelerated in most cases of inappropriate application of catalysts. Multifunctional catalyst was developed by adding beta (*BEA) zeolite to RFCC catalyst, and resulted in improved octane number without sacrificing gasoline yield. Addition of *BEA zeolite to the RFCC catalyst maintained the octane number even in use of catalyst with high hydrogen transferring activity by further isomerizing single branched to multiple branched isoparaffins.
An effective energy production from lignocellulosic biomass is the most important issue in utilization of energy. Using hydrothermal pretreatment, ethanol can be produced effectively from lignocellulosic biomass. However, fermentation inhibitors are generated in the process of the hydrothermal pretreatment, which affects not only cell growth but also ethanol fermentation. It is essential to quantitatively express these effects, but so far no report has been made. Therefore, in this study, we determined the effects of 4 inhibition substances on yeast growth, and by fitting to Monod equation, quantified the effect of these inhibitors on the Monod parameters.
The effect of temperature (370-450 °C) and residence time (0.5-100 s) on phenol and benzene decomposition in supercritical water (SCW) at a pressure of 25 MPa was investigated. Although the rates of phenol and benzene decomposition are relatively low under the conditions used in this study, char and gas formation occurred at a residence time of 20 s and was enhanced with an increase in the temperature and residence time. Char formation from phenol and benzene competes with gas formation. Benzene decomposes in SCW, although the reaction is slower than the decomposition of phenol. The formation of resonance-stabilized phenoxy radicals is believed to play a key role in promoting its decomposition. In the supercritical water gasification (SCWG) of phenol, direct gasification occurring primarily through pyrolysis was more likely. However, in the SCWG of benzene, gasification occurred through two different pathways. Direct gasification mainly occurred through pyrolysis within the first few seconds, and ring opening of the aromatic compounds occurred during longer residence times, ultimately affording gaseous compounds through intermediates such as formic and acetic acid. The formation of phenol from benzene showed Arrhenius behavior, but benzene formation from phenol decreased with temperature in SCW (non-Arrhenius behavior). Based on the deduced mechanisms, we proposed reaction pathways for the decomposition of phenol and benzene in SCW.
Crude palm and Jatropha oils, obtained from Malaysia and Thailand, respectively, were used as low-value feed oils. To remove free fatty acid (FFA) in the feed oils, alkali or acid deacidification treatments were carried out, in which FFA was neutralized with NaOH, and esterified with methanol by H2SO4 catalyst, respectively. Both methods could reduce FFA to low levels, and the following transesterifications with alkali catalysts were successfully carried out. The yields of the treated oils were smaller with alkali than with acid deacidification. Acid deacidification required much longer treatment time than alkali deacidification. Transesterification with NaOH or CH3ONa catalyst could be conducted with the treated oil of FFA mass fraction less than 0.03. CH3ONa catalyst increased the biodiesel yields to more than 0.99 with the treated crude Jatropha oil. Crude palm oil contained more glycerides with shorter chain alkyl fatty acids, which were more reactive to saponification at transesterification, so the yields of biodiesel became lower at the transesterification.
H-beta (*BEA) zeolite catalyst has high activity/stability for the alkylation of isobutane with 1-butene in a CSTR, based on the catalytic nature of H-*BEA. Various preparation methods for H-*BEA were investigated to optimize the catalytic activity for alkylation, including Si/Al ratio, H+/Na+ ion exchange rate, and grain size of zeolite. The relationship between Brønsted acid amount and butene consumption over the catalyst lifetime showed a positive correlation. H-*BEA zeolite with larger grain size and prepared with longer crystallization time achieved higher alkylate yield based on the higher hydride transfer activity.