Surface influencing factors

The catalyst activity depends not only on the chemical composition but also on the diffusion properties of the catalyst material and on the size and shape of the catalyst pellets because transport limitations through the gas boundary layer around the pellets and through the porous material reduce the overall reaction rate. The influence of gas film restrictions, which depends on the pellet size and gas velocity, is usually low in sulphuric acid converters. The effective diffusivity in the catalyst depends on the porosity, the pore size distribution, and the tortuosity of the pore system. It may be improved in the design of the carrier by e.g. increasing the porosity or the pore size, but usually such improvements will also lead to a reduction of mechanical strength. The effect of transport restrictions is normally expressed as an effectiveness factor q defined as the ratio between observed reaction rate for a catalyst pellet and the intrinsic reaction rate, i.e. the hypothetical reaction rate if bulk or surface conditions (temperature, pressure, concentrations) prevailed throughout the pellet [11], For particles with the same intrinsic reaction rate and the same pore system, the surface effectiveness factor only depends on an equivalent particle diameter given by... 

The influence of Ca2+, Mg2+, CT, S042-, phosphate, silicate, phthlate, and salicylate on the oxidation of Mn(II) in the presence of y-FeOOH can be explained, at least qualitatively, in terms of the effect these ions have on the binding of Mn(II) to the y-FeOOH surface. The factors that most strongly influence Mn(II) oxidation on y-FeOOH are pH, temperature, y-FeOOH concentration, ionic strength, [Mg2+] and [Cl-]. 

From the mean crystalline diameter of ca 4 pm and the diameter of a C.00 molecule (ca 1 nm), one can estimate that only a fraction of ca 0.0015 of the (Y>o molecules is located at the surface of the particles. Assuming that effective polarization transfer only occurs for C60 molecules located at the surface, one concludes that the observed signal enhancement of 15 5% corresponds to a polarization enhancement factor of ca 100 30. However, it should be noted that this simple estimation neglects the influence of spin diffusion which can lead to a transport of spin polarization into the bulk, resulting in a lower surface enhancement factor. 

Physical and numerical models are created describing the d3mamics of turbulent combustion in heterogeneous mixtures of gas with polydispersed particles. The models take into account the thermal destruction of particles, chemistry in the gas phase, and heterogeneous oxidation on the surface influenced by both diffusive and kinetic factors. The models are validated against independent experiments and enable the determination of peculiarities of turbulent combustion of polydispersed mixtures. 

Rate Influencing Factor Porous Catalyst Particle Catalyst Coated Surface Burning of a Droplet of Fuel Cells and Simple Living Creatures... 

The synthesis and characterization of the structural defects within aluminosilicate mesoporous materials were provided. We further discussed the fascinating adsorption-desorption hysteresis behaviors and the influencing factors in the formation of the structural defects. However, mesoporous MCM-41 can act as catalyst support for many catalytic reactions, especially involve bulk oiganic molecules, due to its large surface area and pore size. The ability to synthetically control the connectivity of the mesoporous materials may have important applications in catalysis. 

Specific management practices influence triazine runoff and leaching, including fertilizer type, tillage crop residues, and previous crop history, as well as triazine application, formulation, and placement (Baker and Mickelson, 1994). Tillage systems affect various soil properties, such as soil moisture, temperature, pH, organic matter, water flow, and microbial populations, especially at and near the soil surface. These factors can affect transformation, retention, and transport of herbicides in soil. Interactions of and compensations between these processes can influence our prediction of triazine transport in soil. Therefore, triazine movement is usually studied under one management practice at a time. 

The second application concerned aspects of UHV technology. In UHV systems at equilibrium, the predominant gas load arises from the outgassing of internal surfaces. The factors influencing outgassing, including adsorption/desorption, were discussed (Examples 6.10-6.12). Outgassing from the interior of materials (diffusive outgassing), which can arise with both metallic- and non-metallic materials exposed to vacuum, was quantified in Examples 6.13-6.15. 

In catalysis, one of the key concepts to understand catalytic action is the so-called active sites [28], The essential concept behind this term is the fact that catalytic activity in solids is restricted to specific sites in the catalyst surface. Another factor influencing catalytic activity is the geometric factor, that is, a properly spaced array of atoms on the solid surface, named Balandin multiplets,... 

The presence of an oriented oxide and the type of orientation are determined to a marked extent by the nature of the metal surface. Two factors in particular, the presence or absence of contaminating materials and the topography of the metal surface, have a very strong influence on the oxide formation. The presence of a contaminant in many cases leads to the formation of a randomly oriented polycrystalline oxide rather than an oriented one. A faceted or terraced surface can lead to the formation of orientations which are different from those found on a macroscopically smooth surface. It is obviously important to have well prepared and characterized surfaces if epitaxial studies are to have any real meaning. Despite this, there has been a notable lack of attention to this point and some authors have made no indication at all of the nature of the metal surface. 

Rozwadowska, A., Isemer, H-J., 1998. Solar radiation fluxes at the surface of the Baltic Proper. Part 1 mean annual cycle and influencing factors. Oceanologia, 40, 307-330. 

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