Dynamic Behavior in Methanation Activity During the Reaction on Supported Nickel-based Catalysts

Increase in the methanation activity of supported Ni-based composite catalysts during the H₂-CO₂ reaction was studied. A gradual increase in the activity with repeated use was observed in the Ni-La₂O₃ catalysts supported on alumina, whereas the Ni-La₂O₃ catalysts supported on silica gave an almost constant activity through repeated use. This difference was attributed to the reducibility of the catalysts. The nickel oxide part in the composite catalyst supported on silica was reduced sufficiently to nickel metal by hydrogen reduction at 400°C. On the other hand, some portion of the nickel oxide in the composite catalyst supported on alumina was considered to have formed some NiAl₂O₄ spinel which was difficult to be reduced with hydrogen at 400°C. However, this NiAl₂O₄ spinel was reduced gradually during the methanation reaction even at a much lower temperature, 300°C, with the aid of coexisting water vapor formed by the reaction, resulting in the increase in activity

New Concept for the Effect of Metal Particle Size on the Catalyst Activity in the Reactions Involving Oxygen

Carbon monoxide oxidation, steam reforming of methanol, C₃H₆ oxidation, and oxidation of the copper catalyst itself were performed by a flow method using copper catalysts with varying copper particle sizes ranging from 3.6 to 1700 nm in diameter. The specific rate of CO oxidation increased with a decreasing copper particle size. The specific rate of steam reforming of methanol increased with an increasing particle size in the small range within a 4-10 nm range, but this reaction was insensitive to increases in copper particle sizes greater than 10 nm. The selectivity for acrolein formation from C₃H₆ oxidation was maximum when the copper particle sizes were on the order of 20-80 nm in diameter, where the oxidation state of the copper during the reaction was near that of cuprous oxide. From these results, the following new concept was derived. The metal particle size in metallic catalysts controls the balance between the oxidation of copper and the reducing action of reactants or products during reactions involving oxygen

Adsorption and Fluid-mixing Characteristics of Packed Bed Catalysts with Blow-by Sections Part II. A Theoretical Approach to the Concentration Distribution

A theoretical analysis of the fluid-mixing and adsorption characteristics in packed bed catalysts with blow-by sections was conducted. A modified model of a partition gas chromatography that incorporates the effects of the blow-by section is proposed. A strong correlation between the simulated concetration-time curve predicted from this theoretical model and the experimental data was obtained

Adsorption and Fluid-mixing Characteristics of Packed Bed Catalysts with Blow-by Sections Part I. An Empirical Approach to the Problem of Concentration Distribution

Adsorption and fluid-mixing characteristics of packed bed catalysts with blow-by sections, those which are effective for rapid catalytic reactions, were measured by means of a pulse technique, and the results obtained by gas chromatography were examined by dynamic analysis. The exit age distribution function, E(θ), for blow-by packed tubes was divided into two parts : the blow-by section, part B, and the residence section, part R, according to the normalized residence time, θ, in the range of θ1, respectively. For the semicircular blow-by packing, B was found to become maximum at a packing ratio of 13/16. For the cylindrical blow-by packing, the tracer concentration extended into the packing layer, maintaining a more uniform distribution than with either the 13/16 semicircular blow-by packing or full packing. This suggests that the incorporation of cylindrical blow-by sections in packed tube catalysts can improve both the efficiency and the lifespan of this type of catalyst

Dynamic Adsorption Behaviors of Various Zeolites for the Adsorbent of Air Separation by Pressure-swing Adsorption Method

Adsorption behaviors of O₂ and N₂ in pressure-swing adsorption (PSA) at lower temperature on various American natural zeolites and synthetic zeolites having different pore structures were studied. The adsorption properties were largely dependent on whether the dimension of the pore-structure connection is one or three. Molecular sieves MS-5A and MS-4A, which have a large amount of adsorption and a large difference in adsorption capacity for N₂ and O₂, were preferable to air separation by the PSA method. The applicability to the air separation at low temperature was also investigated by using MS-4A and MS-5A as the adsorbent. Highly concentrated N₂ was obtained by MS-5A in the elution period and by MS-4A in the adsorption period. Furthermore, the applicability to the air separation at room temperature was examined by using MS-4A as the adsorbent, and the separation was confirmed at this condition

Reaction Characteristics of Monolithic Catalysts with Different Size of Channels for NOₓ Reduction

The NOₓ reduction with carbon and NH₃ on various monolithic catalysts was investigated over a wide range of space velocity. A three-component composite catalyst, Co-La₂O₃-Pt, supported on active carbon (DIAHOPE 008) was used. It was pulverized into fine powder, and after mixing with hydrogel of aluminum hydroxide, this was molded into cylindrical forms with an inner channel of three sizes along the axial direction. The maximum limit of space velocity (SVₘₐₓ) to achieve a 100% NO conversion was mainly discussed. The same catalyst components were extensively supported on substrates having various channel structures of ceramic honeycomb. For these substrates, the effects of alumina sol-precoating and thermal treatment on the NO-NH₃ reaction were studied. The 0.93% Co-0.51% La₂O₃-1.6% Pt catalyst supported on the honeycomb precoated with 9.2% AI₂O₃ and calcined at 600°C for 1 hour gave the best performance among the various catalyst components. It also showed the best performance among the various structures from the viewpoint of SVₘₐₓ for achieving a 100% NO conversion

Predictive Model for Adverse Events and Immune Response Based on the Production of Antibodies After the Second-Dose of the BNT162b2 mRNA Vaccine

Background: The BNT162b mRNA vaccine for coronavirus disease 2019, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), mimics the immune response to natural infection. Few studies have predicted the adverse effects (AEs) after the second-dose vaccination. We present a predictive model for AEs and immune response after the second-dose of the BNT162b mRNA vaccine. Methods: To predict AEs, 282 healthcare workers (HCWs) were enrolled in this prospective observational study. The classification and regression tree (CART) model was established, and its predictive efficacy was assessed. To predict immune response, 282 HCWs were included in the analysis. Moreover, the factors affected by anti-SARS-CoV-2 spike protein RBD antibody (s-IgG) were evaluated using serum samples collected 2 months after the second-dose vaccination. The s-IgG level was assessed using Lumipulse G1200. Multiple regression analyses were conducted to evaluate variables associated with anti-s-IgG titer levels. Results: The most common AEs after the second-dose vaccination were pain (87.6%), redness (17.0%) at the injection site, fatigue (68.8%), headache (53.5%), and fever (37.5%). Based on the CART model, headache after the first-dose vaccination and age < 30 years were identified as the first and second discriminators for predicting the headache after the second-dose vaccination, respectively. In the multiple linear regression model, anti-s-IgG titer levels were associated with age, female sex, and AEs including headache and induration at the injection site after the second-dose vaccination. Conclusion: Headache after the first-dose vaccination can be a predictor of headache after the second-dose vaccination, and AEs are indicators of immune response

Endolymphatic Hydrops After Sac Surgery

Meniere’s disease is a common disease, that presents with recurrent vertigo and cochlear symptoms. The pathology of Meniere’s disease was first reported to involve endolymphatic hydrops in 1938. The endolymphatic sac is thought to have a role to keep the hydrostatic pressure and endolymph homeostasis for the inner ear. As a surgery for intractable Meniere’s disease, endolymphatic sac drainage with intraendolymphatic sac application of large doses of steroids is performed to control the endolymphatic hydrops and preserve or improve inner ear function. In the present study, to observe the effect of this surgery, we calculated the endolymphatic space size using 3-Teslamagnetic resonance imaging (MRI) 4 h after intravenous injection of gadolinium enhancement at two time points: just before surgery and 2 years after. To reveal the condition of the endolymphatic space, we constructed three-dimensional MR images semi-automatically and fused the three-dimensional images of the total fluid space of inner ear and the endolymphatic space. After fusing the images, we calculated the volume of the total fluid space and endolymphatic space. Two years after surgery, 16 of 20 patients (80.0%) showed relief from vertigo/dizziness and reductions in the ratio of the volume of the endolymphatic size to the total fluid space of inner ear. Endolymphatic sac drainage with intraendolymphatic sac application of large doses of steroids could control vertigo/dizziness and decrease the endolymphatic hydrops. These results indicate that endolymphatic sac drainage is a good treatment option for patients with intractable Meniere’s disease. In addition, volumetric measurement of inner ear volume could be useful for confirming the effect of treatments on Meniere’s disease

Cosmological Baryon Asymmetry in Supersymmetric Standard Models and Heavy Particle Effects

Cosmological baryon asymmetry B is studied in supersymmetric standard models, assuming the electroweak reprocessing of B and L. Only when the soft supersymmetry breaking is taken into account, B is proportional to the primordial B-L in the supersymmetric standard models. The ratio $B/(B-L)$ is found to be about one percent less than the nonsupersymmetric case. Even if the primordial B-L vanishes, scalar-leptons can be more efficient than leptons to generate B provided that mixing angles $\th$ among scalar leptons satisfy $|\th| < 10^{-8} (T/{GeV})^{1/2}$.Comment: 11 pages in LaTex, 3 PostScript figures include