Hydrogenation particle size

Viitanen (1993) developed a mathematical model to analyze the polarization behavior of the electrode under various conditions, in terms of physically measurable properties such as exchange current density, diffusivity of hydrogen, particle size of alloy, void fraction and electrode size. 

Hafnium hydride is brittle and easily cmshed to very fine particle sizes. It is usually produced as an intermediate in the process of making hafnium powder from massive hafnium metal. The hydrogen can be removed by high vacuum pumping above 600°C. 

The available surface area of the catalyst gready affects the rate of a hydrogenation reaction. The surface area is dependent on both the amount of catalyst used and the surface characteristics of the catalyst. Generally, a large surface area is desired to minimize the amount of catalyst needed. This can be accomphshed by using either a catalyst with a small particle size or one with a porous surface. Catalysts with a small particle size, however, can be difficult to recover from the material being reduced. Therefore, larger particle size catalyst with a porous surface is often preferred. A common example of such a catalyst is Raney nickel. 

The gels precipitated as described above are not useful in ion-exchange systems because their fine size impedes fluid flow and allows particulate entrainment. Controlled larger-sized particles of zirconium phosphate are obtained by first producing the desired particle size zirconium hydrous oxide by sol—gel techniques or by controlled precipitation of zirconium basic sulfate. These active, very slightly soluble compounds are then slurried in phosphoric acid to produce zirconium bis (monohydrogen phosphate) and subsequently sodium zirconium hydrogen phosphate pentahydrate with the desired hydrauhc characteristics (213,214). 

It is reported that beryllium powder, of unspecified particle size, will burn in air at 1 200°C and react with nitrogen at 500 C Fluorine appears to attack beryllium at room temperature, and the other halogens, nitrogen dioxide and hydrogen sulphide are said to attack it at elevated temperatures ... 

The time required for the hydrogenation will depend on several factors, such as the speed of shaking, activity and particle size of the catalyst. In the experiments run on ethyl p-nitro-phenylacetate the submitters have found that the time required varied from about 2 to 4 hours. 

As particle size decreases, hydrogen leakage decreases and hot spot temperature in the bed is higher. Thus the smaller particle size has greater activity (see Table VI). A kinetic system which defines the reaction in terms of CO and C02 methanation and CO shift conversion was used to determine the activity (see last column of Table VI). 

Carlson, The Effect of Particle Size-Surface Area and Oxygen on the Hydrogen Content of Titanium Hydrides , Ref 160, p 616. See also related paper on p 50 of Ref 160 124) F.W. 

The presence of catalysts markedly changes the deflagration rate. The greatest rate increase is produced by copper chromite, a well-known hydrogenation catalyst. Some additives which catalyze the process at higher pressures may inhibit it strongly at lower pressures. The catalyst effect is related to catalyst particle-size and concentration, but these factors have not been studied extensively. 

K2C03 3 H202 contains hydrogen peroxide of crystallization and the solid phase decomposition involves the production of the free radicals OH and HOi, detected by EPR measurements [661]. a—Time curves were sigmoid and E = 138 kJ mole-1 for reactions in the range 333—348 K. The reaction rate was more rapid in vacuum than in nitrogen, possibly through an effect on rate of escape of product water, and was also determined by particle size. From microscopic observations, it was concluded that centres of decomposition were related to the distribution of dislocations in the reactant particles. 

The 4-CBA s concentration that is left in the system is of most interest in industrialization. For this reason, the dependence of the rate of 4-CBA disappearance on reaction conditions was carefully investigated. Reaction conditions included hydrogen atmosphere, temperature and catalyst particle size. It is believed that the hydrogen atmosphere... 

Although hydrogenation of 4-CBA over Pd/C is very fast, there is strong diffusion resistance. Furthermore, apparent kinetic equations on different catalyst particle sizes have been obtained from experimental data. 

Industrially, the perfluoroalkyl iodides by telomerization are mostly made by a batch system using peroxide initiators. However, the difficulty of mass production, and the production of hydrogen-containing byproducts in the process are disadvantageous [4]. In this study, a continuous process for the preparation of perfluoroalkyl iodides over nanosized metal catalysts in gas phase and the effects of the particle size on the catalytic activities of different the preparation methods and active metals were considered. 

The amount of hydrogen chloride captured as sodium chloride was proportional to square root of time and sodium diffusion coefficients in glass cullets calculated were 2.9 - 3.9xl0 m /s at 823K. Also, chlorine-firee char can be produced by steam decomposition, even though particle size issue remains. 

The methane conversion and hydrogen yield were investigated as a function of with respect to methane flow rate and both of the two were very high more than 90%. Particle size and sinface area of synthesized carbon were strongly dependent on methane flow rate. Hydrogen produced finm thermal plasma can be applied to fuel cell due to its high purity and carbon black can be applied for the synthesis of rubber industry. 

In the case of a FCB with small particles, the emulsion phase expands [5, 6, 7] when the bed is fluidized. This would make the bed sensitive to the decrease in the gas volume in the emulsion phase. If this assumption is true, we can postulate that the fluidization quality is hardly affected by the gas-volume reduction when the particles, which induce a small emulsion phase expansion, are used. The emulsion phase expansion decreases with increasing particle size and density [6]. In the present study, therefore, the particles used were larger and heavier than that generally used in the FCB. We carried out the hydrogenation of CO2 in a... 

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