Conversion activity

Or conversely, active radicals can be obtained by irradiating certain metal—metal bonded species ... 

In contrast to the hydrolysis of prochiral esters performed in aqueous solutions, the enzymatic acylation of prochiral diols is usually carried out in an inert organic solvent such as hexane, ether, toluene, or ethyl acetate. In order to increase the reaction rate and the degree of conversion, activated esters such as vinyl carboxylates are often used as acylating agents. The vinyl alcohol formed as a result of transesterification tautomerizes to acetaldehyde, making the reaction practically irreversible. The presence of a bulky substituent in the 2-position helps the enzyme to discriminate between enantiotopic faces as a result the enzymatic acylation of prochiral 2-benzoxy-l,3-propanediol (34) proceeds with excellent selectivity (ee > 96%) (49). In the case of the 2-methyl substituted diol (33) the selectivity is only moderate (50). 

It has been reported that below about 370°C, sulfur oxides reversibly inhibit CO conversion activity. This inhibition is greater at lower temperatures. CO conversion activity returns to normal shortly after removal of the sulfur from the exhaust (44). Above about 315°C, sulfur oxides react with the high surface area oxides to disperse the precious-metal catalytic agents and irreversibly poison CO conversion activity. 

Besides, without addictive AICI3 as a crystal conversion agent, phase composition of most neogenic Ti02 particles was anatase in our experiment. Conversions active energy finm anatase to rutile was 460 kJ/mol [5], with temperature arose, crystal conversion rate as well as mass fraction of rutile would increase [6,7]. Hence, after a lot of heat accumulated, phase composition of particle-sintered layer was rutile. 

The surface properties of three types of methanation catalysts obtained by oxidation of selected Intermetallics were examined In relation to their CO conversion activity. The first type (Ni Si, N1 A1 ) which corresponds to active phase-supporl iX the coXventionally prepared catalyst Is little affected by the oxidation treatment. The surface Nl is oxidized and relatively more abundant In the active solids. The second type (active phase-promoter ex Ni Th ) is extensively decomposed on oxidation. The transformation of these alloys Is accompanied by a surface enrichment in Nl. 

Correlation Between Surface Structure and CO Conversion Activity... 

Before any attempt to establish a correlation between the surface structure of the oxidized alloys and their CO conversion activity one must stress that the surface composition of the samples under reaction conditions may not necessarily be Identical to that determined from ESCA data. Moreover, surface nickel content estimates from ESCA relative Intensity measurements are at best seml-quantlta-tlve. This can be readily rationalized If one takes Into consideration ESCA finite escape depth, the dependence of ESCA Intensity ratio... 

Figure 5 Correlation between surface composition and CO conversion activity of oxidized Nij Sl alloys...

Variation of CO conversion activity ( ) and CO sorption capacities ( ) as a function of bulk nickel content. 

Variation of CO conversion activity as a function of bulk nickel content. 

Catalyst % Dispersion of Ir CO conversion Activation energy (kJ/mol) for COz formation Activation energy (kJ/mol) for H2 formation... 

Conversely, activated methylene compounds undergo an addition reaction across the C=N bond of imines. For example, benzylic ketones react with benzylidene anilines to from P-aminoketones [35], whereas the analogous reaction of diphenyl-methylene-protected a-amino esters, and nitriles, produces a disastereomeric mixture of the A-protected a,p-diamino esters, and nitriles [36, 37]. 

Conversely, active constituents may have cooperative effects and together act in an additive or synergistic (supra-additive) manner. In such cases, it would be better to consume the whole plant or extract, because the combination of constituents would give a greater effect than one alone. Thus, to blindly advocate either the use of whole herb or refined single constituents is naive. To fully know what is best for the desired effect, herbs must be considered on a case-by-case basis and the nature of the interactions between the chemical constituents must be carefully considered. Not only must we understand what the plant s chemical constituents do, we must also investigate how they interact. The Use of Herbal Medicine The Current Prevalence of Alternative Medicine... 

Computed results from this model are compared to actual kiln performance in Table VI and the operating conditions taken from kiln samples are given in Table VII. There are no unit factors or adjustable parameters in this model. As with the explicit model, all kinetic data are determined from laboratory experiments. Values of the frequency factors and activation energies are given in Table VIII. Diffusivity values are also included. The amount of fast coke was determined from Eq. (49). With the exception of the T-B (5/12) survey, the agreement between observed and computed values of CO, CO2, and O2 is very good considering that there are no adjustable parameters used to fit the model to each kiln. In the kiln survey T-212/10, the CO conversion activity of the catalyst has been considerably deactivated and a different frequency factor was used in this simulation. 

Light hydrocarbons (Ci to C4) and aromatics (mainly Ce to Ce) were produced by ZSM-5 due to the the conversion of olefins and paraffins. Thus,these results provide evidence for cracking of olefins, paraffins and cyclization of olefins by ZSM-5 at 500 C. The steam deactivated ZSM-5 catalyst exhibited reduced olefin conversion and negligible paraffin conversion activity. 

Fig. 34. Relationship between conversion activity and average catalyst pore diameter (Plumail et al., 1983).

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