Membrane total yield calculations

Table VII. Total-Yield Calculations on the Membrane Reactor...

Ustyugov et al. measured the total unsaturated vapour pressure of selenium-tellurium mixtures with a quartz membrane manometer. The partial pressures of Sc2(g), Tc2(g), and TeSe(g) were calculated from a knowledge of the total pressure, the amounts of substance taken, and the equilibrium constants for the side-reactions with formation of the 864, See, Seg, Te, and Te4 gaseous species. From the partial pressures presented it is found that the minor species contribute, in total, to less than 10% of the total pressure. The results can be expressed by log A °((V.48), T) = 0.6270 - 368.4 7 . A third law evaluation of these data yields A //° ((V.48), 298.15 K) = (0.1 0.2) kJ-moU. ... 

A model for a similar membrane reactor, shown schematically on the top of Figure 5.15, has been developed by Harold et al [5.54] to simulate reactant and products concentrations in parallel-consecutive reaction networks. The membrane reactor compartments on either side of the membrane were assumed to be completely stirred with no pressure gradient across the membrane. The model reaction studied is of relevance to hydrocarbon partial oxidation reactions, where the intermediate oxidation product can further react with oxygen to produce the undesirable total combustion products. Here the goal is to maximize the yield of the intermediate desired product. The calculation results... 

The information given to this point about glycolysis, the citric acid cycle, and the electron transport chain almost makes it possible to calculate the ATP yield from the total oxidation of 1 mol of glucose. However, one more factor must be considered. NADH produced in the cytoplasm during glycolysis does not pass through the mitochondrial membrane to the site of the electron transport chain. Brain and muscle cells employ a transport mechanism... 

Economic evaluation - one main challenge is to bring MES out of the laboratory to technical application. At the early stage of the development, a rough calculation should at least include the assessment of needed productivities at the given fixed and variable costs (e.g., for reactor, electrodes, membranes, reaction medium, pretreatment of the gas). The volumetric productivities (space-time yields), final product concentrations, and total process times determine the overall process performance. These parameters should be used to define operational windows for the production of bulk chemicals. Furthermore, this theoretical approach allows the identification of limiting process parameters. 

There are several sources of discrepancy there is a lack of information about the tortuosity t (> 1) the deviation of the pores from circularity the existence of dead-end pores, etc. In the calculation, the membrane thickness of 0.2 pm refers to a thin skin on top of the total membrane of substantial thickness (100-300 pm). The rest of the membrane has pores that are orders of magnitude larger (with very little hydraulic resistance), and its porosity is also much higher (as much as 0.3-0.6). Such membranes are called asymmetric membranes when the membrane is prepared from one material. Often they are prepared from two different materials to yield a composite membrane. 

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