| Popis: |
The complete isolation of monomethylalkanes from complex hydrocarbon mixtures is demonstrated. The technique is based on the molecular sieve properties of silicalite, a recently synthesized zeolite. Silicalite provides a direct isolation, ca. 40% pure, of the monomethylalkanes, which are sorbed by silicalite but, unlike the n-alkanes, are excluded from Linde 5A molecular sieve. The use of these two sieves thus provides a shape-selective window, approximately 1 A wide. The final purification to ca. 98% or more is obtained using bidimensional preparative gas chromatography (GC). Based on the findings, a new and more rapid method for n-alkane determination is now possible. The high selectivity, reversibility and high thermal stability of silicalite are major advantages. Column chromatography with silicalite separates the 2-, 3- and 4-methylalkane isomers with sample loads 100,000-fold higher than capillary GC. |
