Limitations transport

Types of biocatalyst Biocatalyst scheme Production requirements Characteristics  

Washed whole cell with permeable membrane X X X MF 

For the biocatalyst schemes, the symbol Q l represents the first enzyme relevant as biocatalyst in the 

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The expression for the mass-transport-limiting current density may be employed together with the Nemst equation to deduce the complete current-potential response in a solution containing only oxidized or reduced species... 

Skovborg, P. and Rasmussen, P., 1994. A mass transport limited model for the growth of methane and ethane gas hydrates. Chemical Engineering Science, 49(8), 1131-1143. 

It is not unusual for the full chemical potential of a reaction to be diminished by slower transport processes (i.e., to be transport limited). In fast liquid phase enzyme reactions, mechanical stirring rates can have a strong influence on the observed kinetics that may be limited by the rate of contacting of the reactants and enzymes. Most heterogeneous catalytic reactions take... 

Ideally, separators would present no resistance to ion transport. In practice, some resistance must be tolerated. Still, the resistance of the separator is usually insignificant relative to the transport limitations in the electrodes. Separator permeability is typically characterized by air permeability. The Gurley number expresses the time required for a specific amount of air to pass through a specific area of separator under a specific pressure (e.g., 10 mL through 1 in2 (6.45 cm2) at 2.3 cm Hg). This measurement depends on porosity, pore size, thickness, and tortuosity according to Eq. (1) [17] ... 

Fig. 22. Mass transport limitation and CO breakthrough in a monolith with high intrinsic catalystic activity.

The first-order and second-order kinetics of desorption are by far the most common and practically considered cases. Less than first-order desorption kinetics indicates multilayer adsorption or transport limited desorption (101). An actual significance of the third-order kinetics in desorption has been found recently by Goymour and King (102, 103). 

A fundamental distinction among landscapes is whether the net sediment flux (the total load carried by the river) is limited by the ability of erosional processes to carry sediment (transport-limited environments) or the availability of erodible material (weathering-limited environments). In general, soil-mantled landscapes can... 

The erosion process on slopes can be envisioned as a continuum between the weathering-limited and transport-limited extremes (Carson and Kirkby, 1972 Stallard, 1985,1995a). Erosion is classified as transport limited when the rate of supply of material by weathering exceeds the capacity of transport processes to remove the material. Erosion is weathering limited when the capacity of the transport process exceeds the rate at which material is generated by weath-... 

In contrast, under transport-limited conditions, weathering rates are ultimately limited by the formation of soils that are sufficiently thick or impermeable to restrict free access by water to unweathered material. Erosion rates... 

Table 9-2 Erosion regimes, features, and processes associated with transport-limited and weatherine-limited erosion...

Weathering limited potential transport processes greater than weathering supply. Transport limited supply by weathering greater than the capacity of transport processes to remove material (until weathering is slowed by feedback). 

When soil thickness is at the stable value (F), erosion is transport limited. Chemical weathering is also transport limited. This is, however, not because of reaction kinetics instead this limitation is primarily controlled by physical factors, most probably, restricted access of water to the primary minerals. 

In transport-limited conditions, however, susceptibility is not so important due to the isolating effect of thick soils. In the extreme situation of a flat landscape lowering at a uniform rate, the erosional contribution by a particular rock type should be related only to the area exposed. Solids would be cation-deficient. 

In regions where erosion is transport limited, weathering rates are controlled by the supply of reactive fluids to unstable minerals. This is controlled by soil properties, regional base level, and ultimately, sea level. 

Each concentration can be evaluated assuming no mass transport limitation and the usual priorities for the distribution of the emulsifier polymer particles > aqueous phase > micelles (12). The... 

Scale-up to the industrial scale is only achievable and economical reasonable in stirred or airlift systems. To achieve high cell densities optimal nutrient supply is necessary. Therefore transport limitations have to be avoided by good mixing of cells (microcarrier) and medium. This movement caused by stirrer or aeration leads to mechanical forces evoking severe cell damage or cell death [3,4]. 

Phase transfer catalysts these have been around for about 40 years and were developed as a means of increasing the rates and yields of reactions in which the reactants are in two separate phases. In these cases poor mass transport often limits the reaction. Phase transfer catalysts act by transporting the reactants from one phase into another, thus overcoming mass-transport limitations. 

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