Pinene, adsorption

Although the turpentine is largely desulfurized in the stripping stage and again in the fractionation stages, many appHcations for a- and P-pinene requite further desulfurization. Such methods involve adsorption on carbon, hypochlorite treatment, hydrogen peroxide treatment, treatment with metals, or a combination of techniques (6—15). 

The MIL-supported POM eatalysts were eharaeterized by elemental analysis, XRD, N2 adsorption, and FT-IR-speetroseopy, whieh indieated the preservation of both MIL and POM structures after immobilization. The eomposite M-POM/MIL-101 materials demonstrated fairly good catalytie performanee in a-pinene allylie oxidation (81-84 % verbenol/verbenone seleetivity at 15-25 % substrate eonversion) and earyophyllene epoxidation (100 % selectivity at 88 % conversion) with green oxidants - H2O2 (Ti-POM) and O2 (Co-POM) [126]. 

Figure 34 shows the results for alcohol (methanol, ethanol, 1-propanol and 1-butanol), ketone (acetone and diacetyl), terpene (pinene and linalool), aldehyde (n-nonyl aldehyde) and ester (acetic acid n-amyl ester and n-butyric acid ethyl ester) of various concentrations. Because of the linear characteristics of the CTL-based sensor, the plots are located in a similar region for a certain type of gas of various concentrations where the Henry-type adsorption isotherm holds. Thus, we can identify these gases with various concentrations by simple data-processing. 

The adsorptive separation of pinenes on Zeolites is reported.303 The C-6 and C-7 13C n.m.r. chemical shifts in bicyclo[3,l,l]heptanes support other known conformational evidence and confirm that cls-pinane and ds-myrtanol (209 X = OH) have a bridged-boat conformation, that trans-myrtanol has a bridged-chair conformation, and that trans-2-pinanol and myrtenol (210 X = OH) have Y-shaped conformations verbenone (211 R R2 = O), and trans-verbenol (211 R1 = H, R2 = OH) give anomalous results which may be due to a conjugation effect the bridged-chair... 

The catalytic hydrogenation of a double bond involves the adsorption of the alkene on a metal surface and the transfer of hydrogen from the surface to the double bond. Typical catalysts are finely divided forms of nickel, platinum or palladium, the latter often supported on an inert carrier such as charcoal or barium sulfate. Hydrogenations are carried out in solution, with the hydrogen at atmospheric or higher pressure. The addition of hydrogen is typically cis and from the less-hindered face of the molecule (e.g. the hydrogenation of a-pinene, 3.1). 

The blocking of pores by PVC impregnation was carried out by treatment of the active carbons with suspensions of PVC in alcohol under reflux followed by carbonization at 600°C. This resulted in the deposition of appreciable amounts of carbonaceous material into the microporous structure causing a reduction in pore dimensions and producing carbon molecular sieves. These MSC were found to permit the adsorption of smaller molecules such as benzene or cyclohexane but prevented the adsorption of larger molecules such as isooctane and a-pinene. 

It appears that the adsorption of sulfur takes place in the narrow necks of the pores and reduces dimensions of the entrances to the pore cavity. An adsorption up to 1.6% of sulfur does not sufficiently reduce the pore entrance diameter to make it inaccessible to benzene molecule. However, when larger amounts of sulfur are retained, a fraction of the pores becomes inaccessible to even benzene molecules (molecular diam. 0.37 nm). This was further supported by the adsorption isotherms of organic molecules with larger molecular dimensions such as cyclohexane (mol. diam. 0.48 nm), n.heptane (mol. diam. 0.675 nm), isooctane (mol. diam. 0.68 nm), and a-pinene (mol. diam 0.80 nm). The adsorption of these molecules was found to decrease considerably... 

In order to examine that the adsorption of isooctane and a-pinene was a diflnsion-conlrolled process, adsorption isotherms were determined at two different temperatures. It is interesting to note (Figure 4.12) that the adsorption of both isooctane and a-pinene increased with an increase in the tanperature of adsorption, indicating that the adsorption was an activated process. This also indicated that the width of pore constrictions was only slightly greater than the diameter of these adsorbates so that the molecule experienced a very strong attractive force as it reached the constriction, and this delayed its entry into the pore cavity. The increase in the temperature of... 

FIGURE 4.12 (a) Absorption isotherms of iso-octane vapours on Saran charcoal at different temperatures, (b) Absorption isotherms of iso-octane vapors on Saran-120 at different temperatures. (c) Absorption isotherms of a-pinene vapors on Saran charcoal at different temperatures, (d) Adsorption isotherms of a-pinene vapors on Saran-120 charcoal at different temperatures. (After Bansal, R.C. and Dhami, T.L., Carbon, 18, 207, 1980. With permission.)... 

FIGURE 5.10 Reverse-flow sorption trap (a) and the chromatogram of a 42-component mixture in an air sample collected with the device (b). The three adsorption beds are graded bed A is the weakest absorber and C is the strongest (largest surface area) adsorber. The flow direction is reversed between sample collection and injection. Compounds are 1, acetaldehyde 2, methyl alcohol 3, n-pentane 4, isoprene 5, acetone 6, ethyl alcohol 7, 2-propyl alcohol 8, n-hexane 9, butanone 10, ethylacetate 11, 1-propyl alcohol 12, 2-butyl alcohol 13, trichloromethane 14, benzene 15, isooctane 16, n-heptane 17, 2-pentanone 18, 2,5-drmethylfuran 19, 1-butylalcohol 20, tolnene 21, n-octane 22, hexanal 23, butylacetate 24, ethylbenzene 25, m-xylene 26, n-nonane 27, o-xylene 28, cumene 29, a-pinene 30, -pinene 31, n-decane 32, 1,2,4-trimethylbenzene 33, benzaldehyde 34, d-limonene 35, 1,2,3-trimethylbenzene 36, 1,2-dichlorobenzene 38, n-dodecane 39, 3-pentanone 40, 1-pentyl alcohol 41, 2-heptanone 42, n-undecane. 

In a further study, a series of CMS was prepared from coconut shells by carbonization and activation with carbon dioxide (De Salazar et al., 2000). This series was characterized by carbon dioxide adsorption at 273 K and by immersion calorimetry using liquids with different molecular sizes, dichloromethane (0.33 nm), benzene (0.37 nm), cyclohexane (0.48 nm), 2,2-dimethylbutane (0.56 nm) and a-pinene (0.7 nm). Immersion data were analyzed following the two methods described above. A graphitized carbon black, V3G, with a BET surface area of 62 m g (N2,77 K), was used as a non-porous reference to obtain the area enthalpy of immersion of a carbonaceous surface into the different liquids. With these values, and the enthalpies of immersion of the CMS into the dilferent liquids, the surface areas accessible to the liquids were obtained. These are plotted in Figure 4.50 as a function of the molecular dimension samples are identified by a number that indicates their activation time (De Salazar et al., 2000). 

The porosity of CMS is studied by adsorption of N2 (77 K) and CO2 (273 K) to determine volumes of total and narrow microporosity, respectively, and by immersion calorimetry of the carbons into liquids with different moleeular dimensions (dichloromethane, 0.33 nm benzene, 0.37 nm eyclohexane, 0.48nm 2,2-dimethylbutane, 0.56 nm and a-pinene, 0.70 nm). Adsorption kineties were studied for two-gas mixtures, nitrogen-oxygen and methane-carbon dioxide, and separation abilities were studied using columns packed with the corresponding CMS. 

The two sets of activated charcoals studied here, were already characterized by gas adsorption (8) and immersion microcalorimetry into pure liquids (methanol, benzene, cyclohexane, n-hexane and a-pinene) (9). The main results from nitrogen adsorption are summarized in Table I. 

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