Alkanes selected properties

Methane, ethane, and propane are the first three members of the alkane hydrocarbon series having the composition, Selected properties of these... 

For the non-oxidative activation of light alkanes, the direct alkylation of toluene with ethane was chosen as an industrially relevant model reaction. The catalytic performance of ZSM-5 zeolites, which are good catalysts for this model reaction, was compared to the one of zeolite MCM-22, which is used in industry for the alkylation of aromatics with alkenes in the liquid phase. The catalytic experiments were carried out in a fixed-bed reactor and in a batch reactor. The results show that the shape-selective properties of zeolite ZSM-5 are more appropriate to favor the dehydroalkylation reaction, whereas on zeolite MCM-22 with its large cavities in the pore system and half-cavities on the external surface the thermodynamically favored side reaction with its large transition state, the disproportionation of toluene, prevails. 

TABLE 22.1 Selected Properties of the First Ten Normal Alkanes... 

The alkanes play a very important role in the chromatography of mid-sized nonpolar or slightly polar molecules. With the alkanes, analyte solubility is increased and, due to the low UV cutoff, the lowest detection limits at the lowest operating wavelengths are possible. The addition of small percentages of polar mobile phase modifiers facilitates elution and offers unique selectivity properties. 

Zeolite NU-87, if containing Bronsted-acid sites, is an active catalyst for a large variety of acid catalyzed reactions hke toluene disproportionation, alkylation of benzene with ethylene, amination of methanol to methylamines etc. [51]. Moreover, it was found to possess interesting shape selective properties in the conversion of m-xylene [52] and of polynuclear aromatics, e.g. methylnaphtha-lenes [53]. On non-acidic (i.e. Cs+-exchanged) zeolite NU-87, loaded with small amounts of platinum, n-alkanes like n-hexane or n-octane can be dehydrocycliz-ed in high yields to the corresponding aromatics [54]. 

In 1975 M. Randic proposed a topological index that was designed so that its magnitude parallels selected properties of alkanes, such as the boiling points. The connectivity index is a bond additive quantity. First, the bonds in a molecule... 

Suslick et al found that the porphyrinic MOF, PIZA-3, is capable to heterogeneously oxidize a range of linear and cyclic alkanes and epoxidize cyclic alkenes. The oxidation performance is moderate, which is similar to the homogeneous or heterogeneous Mffi Lporphyrin catalysts. Since PIZA-3 did not have shape-selective property in the reaction, the authors concluded that the catalysis occurred on the exterior surface instead of inside the pores. Their hypothesis was proved by subsequent control experiment. They added the bases that are too peripherally bulky to... 

Appendix 1 lists selected physical properties for repre sentative alkanes as well as members of other families of organic compounds... 

With comprehensive GC, we can now choose a rational set of columns that should be able to tune the separation. If we accept that each column has an approximate isovolatility property at the time when solutes are transferred from one column to the other, then separation on the second column will largely arise due to the selective phase interactions. We need only then select a second column that is able to resolve the compound classes of interest, such as a phase that separates aromatic from aliphatic compounds. If it can also separate normal and isoalkanes from cyclic alkanes, then we should be able to achieve second-dimension resolution of all major classes of compounds in petroleum samples. A useful column set is a low polarity 5 % phenyl polysiloxane first column, coupled to a higher phenyl-substituted polysiloxane, such as a 50 % phenyl-type phase. The latter column has the ability to selectively retain aromatic components. 

Methane is the first memher of the alkane series and is the main component of natural gas. It is also a hy-product in all gas streams from processing crude oils. It is a colorless, odorless gas that is lighter than air. Table 2-1 shows selected physical properties of C1-C4 paraffinic hydro-carhon gases. 

Abstract In this chapter, selected results obtained so far on Fe(II) spin crossover compounds of 1,2,4-triazole, isoxazole and tetrazole derivatives are summarized and analysed. These materials include the only compounds known to have Fe(II)N6 spin crossover chromophores consisting of six chemically identical heterocyclic ligands. Particular attention is paid to the coordination modes for substituted 1,2,4-triazole derivatives towards Fe(II) resulting in polynuclear and mononuclear compounds exhibiting Fe(II) spin transitions. Furthermore, the physical properties of mononuclear Fe(II) isoxazole and 1-alkyl-tetrazole compounds are discussed in relation to their structures. It will also be shown that the use of a,p- and a,C0-bis(tetrazol-l-yl)alkane type ligands allowed a novel strategy towards obtaining polynuclear Fe(II) spin crossover materials. 

A variety of solid acids besides zeolites have been tested as alkylation catalysts. Sulfated zirconia and related materials have drawn considerable attention because of what was initially thought to be their superacidic nature and their well-demonstrated ability to isomerize short linear alkanes at temperatures below 423 K. Corma et al. (188) compared sulfated zirconia and zeolite BEA at reaction temperatures of 273 and 323 K in isobutane/2-butene alkylation. While BEA catalyzed mainly dimerization at 273 K, the sulfated zirconia exhibited a high selectivity to TMPs. At 323 K, on the other hand, zeolite BEA produced more TMPs than sulfated zirconia, which under these conditions produced mainly cracked products with 65 wt% selectivity. The TMP/DMH ratio was always higher for the sulfated zirconia sample. These distinctive differences in the product distribution were attributed to the much stronger acid sites in sulfated zirconia than in zeolite BEA, but today one would question this suggestion because of evidence that the sulfated zirconia catalyst is not strongly acidic, being active for alkane isomerization because of a combination of acidic character and redox properties that help initiate hydrocarbon conversions (189). The time-on-stream behavior was more favorable for BEA, which deactivated at a lower rate than sulfated zirconia. Whether differences in the adsorption of the feed and product molecules influenced the performance was not discussed. 

Perfluorinated alkanes and cycloalkanes are prepared from the corresponding hydrocarbons, either by electrochemical fluorination or by cobalt trifluoride fluo-rination [3], Many perfluorinated solvents are available commercially covering a wide selection of boiling points and densities. Some examples of perfluorinated solvents are listed in Table 3.1 together with their key physical properties. 

Martinez, R., Gonzalez, J.A., de la Fuenta, LG., and Cobos, J.C. Thermodynamic properties of n-alkoxyethanols + organic solvent mixtures. XIV. Liquid-liquid equilibria of systems containing 2-(2-ethoxyethoxy)ethanol and selected alkanes. J. Chem. Eng. Data, 45(6) 1036-1039, 2000. 

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