Porosity Effect of the Silver Catalyst in Hydrogen Peroxide Monopropellant Thruster

In monopropellant system, hydrogen peroxide is used with catalyst to create an exothermic reaction. Catalyst made of silver among the popular choice for this application. Since the catalyst used is in porous state, the effect of its porosity in the hydrogen peroxide monopropellant thruster performances is yet unknown. The porosity changes depending on factors including catalyst pact compaction pressure, bed dimension, and type of catalyst used. As researches on this topic is relatively small, the optimum porosity value is usually left out. The performance of the thruster indicated by the pressure drop across the catalyst bed. Porosity of the catalyst bed adds additional momentum sink to the momentum equation that contributes to the pressure gradient which lead to pressure loss inside thruster. The effect of porosity influences the performance and precision of the thruster. Study of the pressure drop by the catalyst bed requires a lengthy period and expensive experiments, however, numerical simulation by mean of Computational Fluid Dynamics (CFD) can be an alternative. In this paper, 90 wt% hydrogen peroxide solution with silver catalyst is studied in order to investigate the influence of porosity to the performances of the thruster, and to find the optimum porosity of the thruster. Species transport model is applied in the single-phase reaction simulation using the EDM for turbulence-chemistry interaction. Through this study, the effect of porosity towards the thruster performances represented in term of pressure drop, exit velocity, bed temperature, and thrust, and porosity of 0.4 found to be as an optimal value.

Copper Electroless Metallization of Cellulose Paper via Polydopamine Coating and Silver Catalyst

The paper presents the results of copper electroless metallization of cellulose paper with the use of a polydopamine coating and silver catalyst. The polydopamine coating was deposited via a simple dip method using a dopamine hydrochloride solution in 10 mM TRIS-HCl buffer with a pH of 8.5. The research showed that as a result of this process, cellulose fibers were covered with a homogeneous layer of polydopamine. The unique properties of the polydopamine coating allowed the reduction of silver ions from silver nitrate solution and the deposition of silver atoms on the paper surface. Deposited silver served as a catalyst in the autocatalytic electroless copper-plating process. The copper layer covered the entire surface of the paper sheet after 5 min of metallization, favorably affecting the electrical properties of this material by lowering the surface resistivity. The deposited copper layer was further characterized by good adhesive strength and high susceptibility to deformation.

Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides

As an important moiety in natural products, N,O-acetal has attracted wide attention in the past few years. An efficient method to construct N,O-acetal has been developed. Using silver catalyst, cyclobutenediones were smoothly converted to the corresponding γ-aminobutenolides in the presence of formamides, in which cyclobutenediones likely proceed with a key decarbonylative [3 + 2] cycloaddition process. In this way, a series of products with varied substituents were isolated in moderate yield and fully characterized.

Improvement of Propylene Epoxidation Caused by Silver Plasmon Excitation by UV-LED Irradiation on a Sodium-Modified Silver Catalyst Supported on Strontium Carbonate

The effect that UV-LED irradiation exerted on a sodium-modified silver catalyst supported on strontium carbonate (Ag-Na/SrCO3) was examined during an epoxidation of propylene to propylene oxide. Based on our previous study, we used Ag(56)-Na(1)/SrCO3 in this study. The numbers in parentheses refer to the weight percentage of silver and sodium. Although this catalyst system did not contain typical photocatalysts such as titanium oxide or tungsten oxide, UV-LED irradiation of Ag(56)-Na(1)/SrCO3 resulted in an evident improvement in the selectivity and yield of propylene oxide. Such an advantageous effect of UV-LED irradiation could not be discussed based on the bandgap used in photocatalysts and, therefore, we proposed a mechanism based on the plasmon excitation of silver, which could be accomplished using the irradiation wavelength of UV-LED to produce electrons. Since the lifespan of these electrons is expected to be short, it is difficult to place them into direct contact with the gas phase of oxygen. Once the generated electrons move to SrCO3, however, the lifespan is improved, which could allow suitable contact with oxygen in the gas phase to form active oxygen. If the oxygen is active for epoxidation as hydrogen peroxide, this could explain the improvement in activity from UV-LED irradiation.