Methylcyclohexane dehydrogenation for hydrogen production via a bimodal catalytic membrane reactor

The dehydrogenation of methylcyclohexane (MCH) to toluene (TOL) for hydrogen production was theoretically and experimentally investigated in a bimodal catalytic membrane reactor (CMR), that combined Pt/Al₂O₃ catalysts with a hydrogen‐selective organosilica membrane prepared via sol‐gel processing using bis(triethoxysilyl) ethane (BTESE). Effects of operating conditions on the membrane reactor performance were systematically investigated, and the experimental results were in good agreement with those calculated by a simulation model with a fitted catalyst loading. With H₂ extraction from the reaction stream to the permeate stream, MCH conversion at 250°C was significantly increased beyond the equilibrium conversion of 0.44–0.86. Because of the high H₂ selectivity and permeance of BTESE‐derived membranes, a H₂ flow with purity higher than 99.8% was obtained in the permeate stream, and the H₂ recovery ratio reached 0.99 in a pressurized reactor. A system that combined the CMR with a fixed‐bed prereactor was proposed for MCH dehydrogenation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1628–1638, 2015     

Influence of a fiber-network microstructure of paper-structured catalyst on methanol reforming behavior

A novel microstructured catalyst that consists of Cu/ZnO catalyst powders and ceramic fibers was successfully prepared using pulp fibers as a tentative matrix by a papermaking technique. As-prepared material, called a paper-structured catalyst, possessed porous microstructure with layered ceramic fiber networks (average pore size ca. 20 μm, porosity ca. 50%). In the process of methanol autothermal reforming (ATR) to produce hydrogen, paper-structured catalysts demonstrated both high methanol conversion and low concentration of undesirable carbon monoxide as compared with catalyst powders and pellets. The catalytic performance of paper-structured catalysts depended on the use of pulp fibers, which were added in the paper-forming process and finally removed by thermal treatment before ATR performance tests. Confocal laser scanning microscopy and mercury intrusion analysis suggested that the tentative pulp fiber matrix played a significant role in regulating the fiber-network microstructure inside paper composites. Various metallic filters with different average pore sizes, used as supports for Cu/ZnO catalysts, were subjected to ATR performance tests for elucidating the pore effects. The tests indicated that the pore sizes of catalyst support had critical effects on the catalytic efficiency: the maximum hydrogen production was achieved by metallic filters with an average pore size of 20 μm. These results suggested that the paper-specific microstructures contributed to form a suitable catalytic reaction environment, possibly by promoting efficient diffusion of heat and reactants. The paper-structured catalyst with a regular pore microstructure is expected to be a promising catalytic material to provide both practical utility and high efficiency in the catalytic gas-reforming process.     

Numerical simulation on the dynamics of photoinduced cooperative phenomena in molecular crystals

We develop a new simulation method to study the dynamics of initial nucleation processes of photoinduced structural change of molecular crystals. In order to describe the nonadiabatic transition in each molecule, we employ a model of localized electrons coupled with a fully quantized phonon mode, and the time-dependent Schrödinger equation for the model is numerically solved. By applying a mean-field approximation in solving the Schrödinger equation, the calculation method is quite efficient on parallel computing systems. We show that coherently driven molecular distortion plays an important role in the successive conversion of electronic states which leads to photoinduced cooperative phenomena.     

在线实时浓度监测减少环境压力，降低总体拥有成本

随着半导体制造业的不断发展，对现场浓度测量的需求也不断增加。化学品浓度细微变化都会对晶圆缺陷等级造成不良影响，最为重要的是会对产量产生影响。另外，减少液态化学品废弃物流，使其对环境的影响最小化面临着不断增长的压力。     

Fragmentation of the large subunit of ribulose-1,5-bisphosphate carboxylase by reactive oxygen species occurs near Gly-329

The large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) in the illuminated lysates of wheat (Triticum aestivum L.) chloroplasts is broken down by reactive oxygen radicals into 37- and 16-kDa polypeptides. Analysis of the terminal amino acid residues of both fragments revealed that the C terminus of the 37-kDa fragment was Ser-328 and the N terminus of the 16-kDa fragment was Thr-330. Gly-329, which links the two fragments, was missing, suggesting that the fragmentation of the LSU in the lysates driven by oxygen-free radicals occurs at Gly-329. Purified rubisco, exposed to a hydroxyl radical-generating system, was also cleaved at the same site of the LSU. The cleavage site was positioned at the N-terminal end of the flexible loop (loop 6) within the beta/alpha-barrel domain, constituting the catalytic site of rubisco. The binding of a reaction intermediate analogue, 2-carboxyarabinitol 1,5-bisphosphate, to the active form of rubisco completely protected the enzyme from the fragmentation. The fragmentation was differentially affected by CO2, Mg2+, ribulose 1, 5-bisphosphate, or 2-carboxyarabinitol 1,5-bisphosphate. All these results indicate that the conformation of the catalytic site of the enzyme is involved as an important factor determining the breakdown of rubisco by reactive oxygen species. Reactive oxygen species generated at its catalytic site by a Fenton-type reaction may trigger the site-specific degradation of the LSU in the lysates of chloroplasts in the light.     

A New Slip Frequncy Detector of an Induction Motor Utilizing Rotor Slot Harmonics

A method to detect slip frequency from rotor slot harmonics of a three-phase squirrel-cage induction motor is proposed. The rotor slot harmonic voltage Is obtained by summing the three phase voltages, and after being sampled with a multiple of the stator frequency, it is changed into slip frequency waves, from which a voltage proportional to the slip frequency is obtained. Sophisticated sampling techniques allow elimination of the third harmonic voltage induced in the sum of the three-phase voltages and also allow reduction of time constant of the slip frequency detector. Expenmental results show that the slip frequency detector has a good linearity in the range of slip frequency of about -50 to +30 percent of the stator frequency.     

A pneumatically actuated full in-channel microvalve with MOSFET-like function in fluid channel networks

A pneumatically actuated silicon microvalve applicable to integrated microfluidic systems is presented. All the ports of this microvalve are in-channel, and connectable to any surface fluid channels in microfluidic systems. This microvalve controls fluid flow by means of the controlled gap between glass and silicon diaphragm actuated by a control pressure. In addition, the diaphragm is also deformed by the outlet pressure of the microvalve. Due to the feature, this microvalve shows saturation of flow rate like MOSFETs operated at saturation region. The fabricated microvalve device was evaluated focusing on analogous relationship between MOSFET and the microvalve. Fluids such as air and DI-water were well controlled by the control pressure. Fluid starts to flow in the microvalve when the control pressure exceeds its "threshold pressure." Hysteresis due to sticking of diaphragm was not observed in the characteristics. Air flow rate of the microvalve was gradually saturated with the increasing of the outlet pressure as expected. Through the evaluation, analogous relationship between this microvalve and MOSFET has been experimentally demonstrated.     

Highly selective fluorometric determination of polyamines based on intramolecular excimer-forming derivatization with a pyrene-labeling reagent

We introduce a novel approach in highly selective and sensitive fluorescence derivatization of polyamines. This method is based on an intramolecular excimer-forming fluorescence derivatization with a pyrene reagent, 4-(1-pyrene)butyric acid N-hydroxysuccinimide ester (PSE), followed by reversed-phase high-performance liquid chromatography (HPLC). Polyamines, having two to four amino moieties in a molecule, were converted to the corresponding dipyrene- to tetrapyrene-labeled derivatives by reaction (100 degrees C, 20 min) with PSE. The derivatives afforded intramolecular excimer fluorescence (450-520 nm), which can clearly be discriminated from the monomer (normal) fluorescence (360-420 nm) emitted from PSE, its hydrolysate and monopyrene-labeled derivatives of monoamines. The structures of the derivatives were confirmed by HPLC with mass spectrometry, and the emission of excimer fluorescence could be proved by spectrofluorometry and time-resolved fluorometry. The PSE derivatives of four polyamines [putrescine (Put), cadaverine (Cad), spermidine (Spd), and spermine (Spm)] could be separated by reversed-phase HPLC on a C8 column with linear gradient elution. The detection limits (signal-to-noise ratio of 3) for the polyamines were 1 (Put), 1 (Cad), 5 (Spd), and 8 (Spm) fmol on the column. Furthermore, the present method was so selective that biogenic monoamines gave no peak in the chromatogram.     

Characterization of natural resin shellac by reactive pyrolysis-gas chromatography in the presence of organic alkali

A method to determine chemical composition of natural resin shellac was developed on the basis of reactive pyrolysis-gas chromatography (Py-GC) in the presence of an organic alkali, tetramethylammonium hydroxide ((CH(3))(4)NOH, TMAH). Py-GC using 25% TMAH aqueous solution enabled the highly sensitive determination of terpenic acids, aleuritic acid, several minor fatty acids, and the wax components of shellac as their methyl derivatives on the resulting pyrograms with less than 2.0% relative standard deviations without using any cumbersome pretreatment. The observed average distributions of each resin acid component determined by reactive Py-GC for shellac samples from India and Thailand showed that the average ratios among terpenic acids, aleuritic acid, and the other fatty acids were about 53:34:14 for Indian shellac and 51:35:14 for Thailand shellac, respectively, suggesting a slightly significant difference. However, clearer discrimination of the shellac samples from the two different growing places was attainable by applying principal component analysis for the mole percent distributions of all the acidic components determined by reactive Py-GC.