Pentane isotherm

The shapes of these isotherms are controlled by surface heterogeneity, and thus provide a means of deducing the various modes of interfacial attraction presented by the substrates. Isotherms of pentane on unsized IM6 before and after plasma treatment are congruent. Pentane interacts only by dispersion force attraction, as does methylene iodide the registry of these isotherms is predicted by the similarity in ft obtained from wetting measurements. Pentane isotherms serve as a reference with which to assess the effect of additional modes of solid/vapor interaction with acidic and basic probes. 

Fig. ni-18. Adsorption isotherm for n-pentane and -octane at 15°C. The dotted curve shows the hypothetical isotherm above P/Pq = 1, and the arrows mark the T values corresponding to a monolayer. (From Refs. 128, 129.)... 

Fig. 2.17 The adsorption of pentane on different adsorbents, (a) Effect of the nature of the adsorbent on the shape of the isotherm (each isotherm is labelled with the name of the adsorbent), (b) Dependence of ajpentane) on the value of parameter C. (Courtesy Kiselev and Eltekov. )...

The strength of dispersion interaction of a solid with a gas molecule is determined not only by the chemical composition of the surface of the solid, but also by the surface density of the force centres. If therefore this surface density can be sufficiently reduced by the pre-adsorption of a suitable substance, the isotherm may be converted from Type II to Type III. An example is rutile, modified by the pre-adsorption of a monolayer of ethanol the isotherm of pentane, which is of Type II on the unmodified rutile (Fig. 5.3, curve A), changes to Type III on the treated sample (cf. Fig. 5.3 curve B). Similar results were found with hexane-l-ol as pre-adsorbate. Another example is the pre-adsorption of amyl alcohol on a quartz powder... 

The IsoSiv process is an isobaric, isothermal adsorption technique used to separate n-paraffins from gas oils. The operation conditions are approximately 370°C and 100 psi. Desorption is achieved using n-pentane or n-hexane. The solvent is easily distilled from the heavier n-paraffins and then recycled. 

A thirty-plate bubble-cap column is to be used to remove n-pentane from a solvent oil by means of steam stripping. The inlet oil contains 6 kmol of n-pentane/100 kmol of pure oil and it is desired to reduce the solute content of 0.1 kmol/100 kmol of solvent. Assuming isothermal operation and an overall plate efficiency of 30 per cent, what is the specific steam consumption, that is kmol of steam required/kmol of solvent oil treated, and the ratio of the specific and minimum steam consumptions. How many plates would be required if this ratio is 2.0 ... 

NaY yields a compietely reversible type I isotherm, characteristic of micropore filling common in many zeolites. However, USY-B and DAY yield an isotherm close to type IV. Similar differences in adsorption isotherms were observed for n-hexane, cyclohexane, n-pentane and benzene. Furthermore, many of the isotherms measured on DAY zeolites showed hysteresis loops (Figure 6). 

For propane, n-pentane and n-hexane the differential heats of adsorption over FER dropped more rapidly, right after 1 molecule was adsorbed per Bronsted acid site. Similar results were obtained with TON. In contrast, with MOR and FAU the drop in the differential heats of adsorption for n-alkanes occurred at lower coverages, indicating that only a certain fraction of the Bronsted acid sites were accessible to the adsorbing alkane probe molecules. With MFI the drop did not occur until 2 molecules of n-alkane were adsorbed per Bronsted acid site, suggesting perhaps a higher stoichiometry of about two n-alkanes per Bronsted acid site. In the cases of i-butane and i-pentane the drop occurred around one alkane per Bronsted acid site. Finally, n-butane adsorption isotherms measured over TON framework type catalysts having three different A1 contents (Si/Al2 = 90, 104, 128) showed Henry coefficients to increase with increase in the A1 content [5], Based... 

Figure 6 shows the isotherms of the samples using different alkanes as expander. Except the sample obtained with nonane, the adsorption-desorption isotherms of all other compounds are type IV, characteristic of mesoporous materials according to the BDDT classification [21], Isotherms can be decomposed in three parts the formation of the monolayer, a sharp increase characteristic of the capillary condensation of nitrogen within the mesopores and finally a plateau indicating the saturation of the samples. From pentane to decane the relative pressure at which the capillary condensation occurs, increases from 0 30 to 0.60, indicating that the value of the pore diameter increases when the alkane chain length is raised since the p/po position of the inflection point is related to the pore diameter. From undecane, this value decreases to reach 0.40 for dodecane We can conclude that the value of the pore diameter drops from decane to dodecane... 

The amount of theoretical and experimental research focused on the interaction, equilibrium and dynamical properties of noble, simple and polyatomic gases within quasi-one-dimensional nanotubes is still limited [6-13]. Experimental adsorption isotherms have been reported for simple gases (Ar,N2) and alkanes (methane [11], ethane [12], propane-butane-pentane [13]) in monodisperse nanotubes of aluminophosphates. It is expected that similar experiment could be carried out soon in bundles of monodispersed carbon nanotubes. 

Figure 2-20 gives the pres sure-volume diagram for a mixture of n-pentane and n-heptane, showing several isotherms and the saturation envelope.4 Notice that at lower temperatures the changes in slope of the isotherms at the dew points are almost nonexistent. Also notice that the critical point is not at the top of the saturation envelope as it was for pure substances. 

Replot two isotherms of the data given in Figure 2-37 as pressure against composition in weight percent. Use temperatures of 75°F and 300°F. This is called a pressure-composition diagram. Label the bubble-point lines and dew-point lines. 2-23. Determine the compositions and quantities of gas and liquid when 10 lb moles of a mixture of 55 mole percent methane, 20 mole percent propane and 25 mole percent n-pentane is brought to equilibrium at 160°F and 1500 psia. 

Figure 3. Sorption of n-pentane on 5A at 523 K (a) comparison of the experimental uptake with the best fit obtained by the present model (b) uptake with no internal heat transfer resistance and (c) uptake for an isothermal case.

The proposed model for non-isothermal sorption kinetics can quantitatively describe uptake0data for adsorption of i-octane on 13X and n-pentane on 5A zeolites. The study indicates that the principal resistance to mass transfer for these systems may be confined at the surface of the zeolite crystals. It is also found that the internal thermal resistance of the assemblage of the micron size zeolite crystals used in the kinetic test is significant which produces a substantial thermal gradient within the assemblage and slows down the heat dissipation from it. 

The accuracy of the pressure and temperature measurements was verified by measuring the vapor pressure curves and critical points for pentane and for toluene. Vapor pressures were measured by observing the formation of a liquid phase as pentane or toluene was injected into the constant-volume view cell under isothermal conditions. The observation of critical opalescence was used to determine the critical point. The measured vapor pressures and critical points are given in Table I. Vapor pressures deviate from... 

Film Thickness Oven Carrier Injection Detector 60m x 0.32 mm I.D. J WP/N 123-1063 1.0 micron 35 C (Isothermal) Helium 34 cm/sec 1.0 uL Split 1 50 FID 2. Propylene Oxide 3. Isopropanol 4. VInytidene Chloride 5. Dlmethoxy Methane 6. Nftromethane 7. Methyl Ethyl Ketone 8. 2-Methyl Pentane 9. Butylene Oxide 10. 2-Butanol 11. 1,1,1-Trichtoroethane... 

The early work of Kiselev (1957) revealed that the adsorption isotherms of n-pentane and n-hexane on non-porous quartz were intermediate in character between Types II and m. Values of C(BET) <10 were obtained and the differential enthalpies of adsorption decreased steeply at low surface coverage. More recently, the isotherms of isobutane (at 261 K) and neopentane (at 273 K) on TK800 have been found to be of a similar shape (Carrott et al., 1988 Carrott and Sing, 1989). Unlike those of benzene, these alkane isotherms do not undergo a pronounced change of shape as a result of surface dehydroxylation. This is consistent with the non-specific nature of their molecular interactions (see Chapter 1). 

There will be an isotherm similar to ABCD for each temperature. The complete P-V diagram for the i-pentane, w-heptane S3retem containing 52.4 weight per cent w-heptane is shown in Figure 24. The critical point is the point where the bubble-point line and dew-point line meet. This is equivalent to the statement that the intensive properties of the coexisting liquid and vapor phases are identical at the critical point. Consequently, the liquid and tiie vapor are indistinguishable at the critical pressure and temperature, The critical... 

---