Constant adsorption

The relative reactivities obtained by the method of competitive reactions corresponded to the values of the separately obtained rate and adsorption constants. The reactivities obtained by the competitive method differ, of course, from the ratio of the rates of the separately studied single reactions this difference increases with the difference in the values of the adsorption coefficients of competing substances. 

Table 1.2 Calculated heats of adsorption and adsorption constants for various hydrocarbons in zeolites with different channel dimensions.

From plotting of 1/r versus 1/C, the reaction rate constant, k and adsorption constant, K can be obtained. Fig. 3 indicates that photocatalytic decomposition of 4-NP is in good agreement with L-H model. In the present work, the values of k and K in the presence of H2O2 were found to be higher than those in the absence of H2O2, as shown in Table 1. 

Table 1. Rate constant (k) and adsorption constant (K) for the photocatalytic decomposition of 4-NP on Ti02/Cr-Ti-MCM-41 in visible light...

In the present study, the HDN of decahydroq unohne (DHQ) was studied over NiMo(P)/Al20.T catalysts in the presence and absence of H2S. The reaction took place at 593 K and 3.0 MPa, thus allowing us to observe the most important reaction intermediate, propylcyclohexylamine, and to calculate the kinetic constants from the experimental results. Rate and adsorption constants for the different reaction steps were determined by separate and by combined HDN studies of DHQ and cyclohexene. 

The reaction path DHQ THQl- OPA HC must be taken into account to explain the promotional effect of phosphorus in the absence of H2S. A strong promotional effect of phosphorus has been observed for the HDN of OPA over NiMo/AhOa catalysts, which could be explained by the larger adsorption constant of OPA on the P-containing catalyst. The HDN activity of OPA was even higher in the absence of H2S (16). 

At small space times, the C5 hydrocarbons could not account for all the PA converted, although no PA was found in the reactor outlet a similar observation was reported by La Vopa and Satterfield (17). But at higher space time the C5 hydrocarbons do account for more than 90% of the PA converted. Thus only the data at very high space time were used to calculate Kn (Fig. 5). The adsorption constants of DHQ were obtained in the same way. The mass balance of DHQ and CHE was always good. The resulting adsorption constants are given in Table 4. 

The present results show that the separate steps in an HDN reaction network can not be Imnped together into one kinetic equation. The intermediate reactions may take place on different catal ic sites which differ in their ability to bind reactants, intermediates, and products. Phosphorus was foimd to modify the rate constants as well as the adsorption constants of the HDN reaction steps, indicating that it changes both the number and nature of the active sites of NiMo/AlaOa catalysts. 

The crucial reaction intermediate PCHA in the HDN network of quinohne-type compounds has been clearly observed. Formation of cis-PCHA was faster than that of trans-PCHA, but isomerization was relatively rapid. The presence of H2S in the reaction stream favours the cleavage of the first C-N bond in DHQ, but slows down the C-N bond cleavage in PCHA. The presence of H2S decreases the adsorption constants of DHQ and NH.i. It is concluded that 40% of the HDN reaction of DHQ takes place through the reaction path of DHQ- THQl->OPA —>HC at 593 K and 3.0 MPa in the absence of H2S, while less than 10% takes place in the presence of H2S. 

TABLE 2 Distribution Constants and Interfacial Adsorption Constants of 5-Br-PADAP (HL) at 25°C... 

Adsorption constant at two interfaces PPb distance discriminant analysis Parts per billion... 

Kinetic orders in CO oxidation on M/A1203 can be explained by the classical Langmuir-Hinshelwood expression for the rate equation, as a function of the rate constant k, the adsorption constants K and the partial pressures P ... 

Choice of soil type and adsorption constants are less critical than choice of application dates. 

The adsorption plateaus on this solid, determined with each of the surfactants (Table II) and the individual CMC values, were used to calculate the adsorption constants input in the model. Figure 3 compares the total adsorption (sulfonate + NP 30 EO) of the pseudo-binary system investigated as a function of the initial sulfonate fraction of the mixtures under two types of conditions (1) on the powder solid, batch testing with a solid/liquid ratio, S/L = 0.25 g/cc (2) in the porous medium made from the same solid, for which this solid ratio is much higher (S/L = 4.0 g/cc). 

Here, K is the multiple adsorption constant, C is a relative polymer concentration defined by... 

G Relative polymer adsorption density defined by Equation 8 i An integer—the number of bound segments on a given molecule K Primary adsorption constant... 

In a typical pulse experiment, a pulse of known size, shape and composition is introduced to a reactor, preferably one with a simple flow pattern, either plug flow or well mixed. The response to the perturbation is then measured behind the reactor. A thermal conductivity detector can be used to compare the shape of the peaks before and after the reactor. This is usually done in the case of non-reacting systems, and moment analysis of the response curve can give information on diffusivities, mass transfer coefficients and adsorption constants. The typical pulse experiment in a reacting system traditionally uses GC analysis by leading the effluent from the reactor directly into a gas chromatographic column. This method yields conversions and selectivities for the total pulse, the time coordinate is lost. 

Often a term for an inert substance may be required in the equation for tfv. Also, one or more of the other terms can be left out, thus giving rise to another rate equation for analysis. For instance, hydrogen, although a reaction participant, often is relatively slightly adsorbed. In such cases, analysis with the complete denominator will not necesssarily give zero for the adsorption constant of the otherwise omittable substance. One of the cases may be preferable statistically. 

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