Conventional carrier

The use of a monolithic stirred reactor for carrying out enzyme-catalyzed reactions is presented. Enzyme-loaded monoliths were employed as stirrer blades. The ceramic monoliths were functionalized with conventional carrier materials carbon, chitosan, and polyethylenimine (PEI). The different nature of the carriers with respect to porosity and surface chemistry allows tuning of the support for different enzymes and for use under specific conditions. The model reactions performed in this study demonstrate the benefits of tuning the carrier material to both enzyme and reaction conditions. This is a must to successfully intensify biocatalytic processes. The results show that the monolithic stirrer reactor can be effectively employed in both mass transfer limited and kinetically limited regimes. 

Figure 3.2 Variations in the relative degree of transit pulse dispersion in the case of conventional carrier transport. The specimen thickness is least for the broken curve and greatest for the dotted curve.

We have some preliminary results indicating that reason 3 is the likely explanation for conventional carrier membranes. 

This experiment demonstrates application of a batch process in which multiple samples are analyzed simultaneously with a quality control (QC) sample. For yield measurement, 90Sr tracer is added to the QC sample this is an alternative to the conventional carrier yield determination described in Experiment 13. This substitution of external for internal tracer yield measurement requires great care in processing as similarly as possible all samples in a batch. Any deviation of the individual yield from the QC-sample yield by more than 10% will be detected by measuring the recovered weight of the strontium carrier, and should stimulate examination of the procedure for irregular losses. 

The photoluminescence of lattice oxide ions of transition-metal oxides mixed or supported on conventional carriers has also been reported (160b). The luminescence is shown to occur from oxo complexes (M04)" (M = V, Mo, W, Cr) in which the transition-metal ion exists in a high oxidation state with a d° electronic configuration. Since the d orbitals of the transition-metal ion are not occupied and therefore the d-d transitions impossible, S0 -)-S charge-transfer electronic transitions occur in the oxo complexes upon absorption of light. The result is that an electron is transferred from a filled molecular orbital localized mainly on the O2 anions to a d orbital of the transition-metal ion. This leads to the formation of an excited singlet electronic state S, with two unpaired electrons, in which the total electron spin,... 

Dye cycles using INTEX CARRIER 37 are not expected to be different from conventional carriers. Carpet has been dyed successfully for one hour at the boil. 

CINDYE DAC-999 is a unique product for dyeing polyester atmospherically or under pressure which has no odor and no adverse toxicological properties when compared to conventional carriers,... 

Interpretation of fundamental transport parameters in terms of rate constants for the simple carrier and for the conventional carrier... 

Parameter Simple-carrier interpretation Conventional-carrier interpretation... 

Fourth model for facilitated diffusion the conventional carrier... 

The simple carrier of Fig. 6 is the simplest model which can account for the range of experimental data commonly found for transport systems. Yet surprisingly, it is not the model that is conventionally used in transport studies. The most commonly used model is some or other form of Fig. 7. In contrast to the simple carrier, the model of Fig. 7, the conventional carrier, assumes that there exist two forms of the carrier-substrate complex, ES, and ES2, and that these can interconvert by the transitions with rate constants g, and g2- Now, our experience with the simple- and complex-pore models should lead to an awareness of the problems in making such an assumption. The transition between ES, and ES2 is precisely such a transition as cannot be identified by steady-state experiments, if the carrier can complex with only one species of transportable substrate. Lieb and Stein [2] have worked out the full kinetic analysis of the conventional carrier model. The derived unidirectional flux equation is exactly equivalent to that derived for the simple carrier Eqn. 30, although the experimentally determinable parameters involving K and R terms have different meanings in terms of the rate constants (the b, /, g and k terms). The appropriate values for the K and R terms in terms of the rate constants are listed in column 3 of Table 3. Thus the simple carrier and the conventional carrier behave identically in... 

Fig. 7. The conventional carrier. Formal representation of the kinetic scheme. Symbols as in Figs. 5 and 6.

People who have worked many years in the transport field have strong intuitive feelings for the correctness of the conventional carrier model. It seems perfectly natural to assume that the substrate-carrier complex formed at one face of the membrane does undergo a transition to a complex which breaks down at the opposite face. Nevertheless, steady-state kinetic experiments cannot justify this assumption and the simpler model yields decidedly simpler kinetic expressions and to a heightened awareness as to the molecular interpretation of the measurable kinetic parameters, as we proceed to discuss. 

If one wishes to adopt the conventional carrier model, then the corresponding result is (from Table 3) 1 /k2 > 1 /b + 1 /g2 + g / ig2- Thus the resistance experienced by the free carrier during the transition across the membrane is greater than both of the following the resistance for the transition of the carrier-substrate complex across the membrane, or its breakdown at the cis face to liberate free carrier. 

To obtain the kinetic equations describing countertransport we will have to solve the carrier model for the situation in which two substrates S and P are present across the membrane, both of them capable of interacting with the carrier. The relevant formal model is given in Fig. 9, where we have used the diagram representing the simple carrier or in Fig. 10 where the representation is that of the conventional carrier. To solve the mathematics, we write a steady-state equation for each of the forms involving carrier and the two substrates and a conservation equation ex-... 

Fig. 10. Two substrates using the conventional carrier. Formal representation of the kinetic. scheme. Symbols as in Figs. 8 and 10, with the addition of rate constants /ii and /12 for the interconversion of the two forms of the substrate P-carrier complex EP, and EPj.

A similar catalytic system based on finely dispersed PVP-stabilized Pt-nanoclusters supported on conventional carriers and modified with Cnd accomplished the enantioselective hydrogenation of 2,2,2-trifluoroacetophe-none into the (R)-alcohol at 20 bar hydrogen in a mixture of o-dichloroben-zene and ethanol (Zhang et al. The same catalyst was not very effective in the asymmetric decomposition-hydrogenation of racemic 3-hydroxybutan-2-one. The enantiomeric excess reached a maximum ee > 40% at a molar ratio of the modifier to reactant of about 1 650 in dichloromethane-ethanol solvent (Zuo et al. ). 

The nature of the carrier gas strongly affects the separation of model mixtures. A six-component mixture of hydrocarbon gases can be separated completely on sodium zeolite at a column temperature of 20 C with carbon dioxide, whereas the conventional carrier gases such as hydrocarbon and helium are not able to separate this mixture (see Fig. 5-28). It is interesting to note that, in contrast to carbon dioxide, use of helium or nitrogen as carrier gas with this form of zeolite does not result in a temperature inversion of the elution order propane-ethylene and butane-propylene, i.e., an unsaturated compound is eluted after the corresponding saturated compound at any column temperature. 

Main processes occurring in the conversion of solid fuels using conventional carrier materials [and hence requiring H2O or CO2 as gasification agent (a)] versus CLOU carriers which release gaseous oxygen into the reactor (b). 

The high load catalyst is, on the contrary, supported on a half cylinder support, which has a higher geometric specific surface area with respect to the conventional carriers this means that it is possible to introduce a larger amount of active mass into the reactor, without increasing the thickness of the catalytic layer, as reported in Table 14.2. ... 

Cellular ceramic supports are proposed as an attractive alternative to conventional carriers (generally spheres, extradates or pellets) for solid catalysts. They are of two types (i) monolith honeycomb made of small parallel squared channels (about 1 mm size) displaying a catalytic wall (400 channels per square inch or cpsi) or (ii) monolith foam presenting small blocks of pores (30 pores per inch or ppi). These materials are specifically manufactured by CTI Company (Ceramiques Techniques et Industrielles, Salindres, France) or Coming Company. 

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