Binary desorption

The binary desorption kinetics of 5% ethane and 5% propane in the same particle is investigated at a higher temperature of 60 C, 1 atm. The desorption kinetics predicted by the models (lines) and the experimental data (symbols) are presented in Figure 8. Similar phenomena as above are observed. The simulated uptake using the MPSD model agrees well with the experimental data of ethane. Some deviations are observed for the propane uptake. 

Fig. 7. Binary desorption kinetics of ethane and propane onto Norit activated carbon of...

Eight variants of the DD reaction mechanism, described by Eqs. (21-25) have been simulated. The simplest approach is to neglect B2 desorption in Eq. (22) and the reaction between AB species (Eq. (25)). For this case, an IPT is observed at the critical point Tib, = 2/3. Thus this variant of the model has a zero-width reaction window and the trivial critical point is given by the stoichiometry of the reaction. For Tb2 < T1B2 the surface becomes poisoned by a binary compound of (A -I- AB) species and the lattice cannot be completely covered because of the dimer adsorption requirement of a... 

A different picture was obtained in the case of the reference Pt—BaAy-A Oj (1/20/100 w/w) sample (Figure 6.12). In the case of the TPD experiment performed after NO, adsorption at 350°C, the decomposition of stored NO, species was observed only above 350°C. Evolution of NO and 02 was observed in this case, along with minor quantities of N02 [25,28,33,35], Complete desorption of NO, was attained already slightly below 600°C. As in the case of the binary Ba/y-Al203 sample, the data hence indicate that nitrates formed upon N0/02 adsorption at 350°C followed by He purge at the same temperature, did not appreciably decompose below the adsorption temperature during the TPD run under inert atmosphere. 

Figure 5. TLC retention factor Rp for poly(methyl methacrylate) on silicagel, as a function of the elution strength of binary solvent (carbontetrachloride, CCl )/ displacer (1,4-dioxane) mixtures. Note the steep increase in Rj, at Efj w 0.38, indicating a sharp adsorption/ desorption transition.

A six-port valve was used in both manual and semi-automated SPME interfaces and PEEK tubing used to connect the HPLC system to the SPME probe. A Cohesive HTLC 2300 with dual pumps along with a Sciex API 3000 mass spectrometer was used for LC/MS/MS and a Symmetry Shield RP-18 (5 ji, 50 x 2.1 mm) for HPLC. A quaternary pump with flow switching was used for desorption chamber flushing along with MS make-up flow and a binary pump for LC/MS/MS. Acetoni-trile/0.1% acetic acid in water (90 10, solvent B) and 10 90 acetonitrile/0.1% aqueous acetic acid (solvent A) were used, with 10% B for 0.5 min ramped to 90% B in 2 min and held at this concentration for 1.5 min before returning to 10% B for 1 min at a flow rate of 0.5 mL/min. 

In a scheme complementary to the one just presented where thiols are removed by reductive desorption of thiols, molecules can also be removed during stripping of a UPD layer. This was demonstrated by Shimazu et al. [221] where an alkane thiol SAM was deposited onto a Au(l 11) that had been modified with Pb. Oxidative stripping of the lead also caused thiols to be removed. The empty sites were then subsequently filled with mercaptopropionic acid (MPA). A remarkable result is that the binary SAMs exhibit only one desorption peak. From this it was concluded that a well-mixed layer forms that is very different from the mixed SAM obtained by adsorption from solution containing both types of thiols. In this case the layer exhibits singlecomponent domains that are refiected by two desorption peaks. 

In a later study of the same series of binary catalysts, Mukerjee and McBreen showed that the restructuring accompanying the desorption of ad-... 

Tracer diffusivities are often determined using the thin-source method. Self-diffusivities are often obtained from the diffusion couple and the sorption methods. Chemical diffusivities (including interdiffusivity, effective binary diffusivity, and multicomponent diffusivity matrix) may be obtained from the diffusion-couple, sorption, desorption, or crystal dissolution method. 

If n solvated nonpolar ligands simultaneously interact with the solvated peptide, then the binary complex that forms can be represented by the equilibrium shown in eq 6. When the concentration and thus the surface tension of the organic solvent reaches a critical value, then the partially solvated peptide P(+cDo)is bound to the RPC stationary phase will desorb and become re-solvated to generate the species P(+ DO)i,m- Thus, overall desorption can be represented as ... 

In the voltammogram of Au(lll) modified with binary SAM of 1-undecanethiol and 11-mercaptoundecanoic acid, only one reductive desorption peak was formed for any value of mixing ratio of both thiols [139]. Such a response suggests that both thiols are well mixed in the SAM. 

Only a few binary hydrides like VH2 or NbH2 show reasonable hydrogen desorption pressures at temperatures suitable for most technological applications. Therefore, thermodynamic tuning of metal hydrides was, and still is, an important challenge to be faced. 

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