Marco Taramasso

Gas-Chromatographic Investigations on Dimethyldioctadecyl Ammonium Derivatives of Different Clay Minerals

The gas-chromatographic behaviour (selectivity performance for cyclohexanebenzene and m-, p-xylenes pairs separation) of dimethyldioctadecylammonium complexes with kaolinite, fire-clay, halloysite, attapulgite, hectorite and various montmorillonites, nontronites and vermiculites has been investigated. The obtained data indicate the influence of specific surface and charge density on relative retention value (α), and of substitution location (tetrahedral versus octahedral sheet) within the clay lattice on selectivity. Hence, derivatives with nontronites and vermiculites, that is the clay minerals where the principal lattice substitutions are predominantly occurring within the tetrahedral sheet and possessing the highest surface charge density, are very effective sorbents for gas-chromatographic use. The application of gas-chromatography as investigation tool of clays surface is suggested.

The organic complexes of the clay minerals and their use in gas chromatography

Abstract The physical properties, selectivity, efficiency, and preparation of organic derivatives of clay minerals is discussed and the possible applications in gas chromatography are studied. The paper is a review of some unpublished work and also refers to work already published (Chromatographia, (1969) 239-242 and 551-553)

Sieving effects of hormites in gas-adsorption chromatography

Abstract Sepiolite, a clay mineral of the hormite group characterized by a porous lattice, was tested as a stationary phase in gas chromatography. The adsorbent is homogeneous and is able to separate molecules on the basis of steric factors. Oxygen, nitrogen, methane and carbon monoxide are easily separated at −78°; carbon dioxide is eluted with a symmetric peak at room temperature. A simple ballistic programme is able to perform the complete resolution of all the above components with a short column (80 cm long). As the specific interactions are weak, sepiolite may be applied to the separation of liquid hydrocarbons on the basis of their geometric configurations. The elution order for the paraffins is: doubly branched alkanes, singly branched alkanes, straightchain alkanes. The resolution between cis and trans forms of disubstituted cycloalkanes is very high. The values for the efficiency and symmetry are such that the use of sepiolite in gas-solid chromatography is considered to be practical.

Adsorbents for gas-solid chromatography prepared by epitaxial modification of clay minerals with quaternary ammonium ions

Abstract The epitaxial growth of a phase over a heterogeneous crystalline matrix is proposed in order to obtain homogeneous adsorbents able to show both steric effects and specific interactions. The properties required by both phases in order to produce stable derivatives are examined. Examples are given of the epitaxial modification of mica-type layered silicates with N-alkylpyridinium and n-alkylammonium ions. Some unpublished and published results are reviewed for derivatives containing dimethyldiotadecylammonium and trimethylhexadecylammonium ions.

Considerations for the design of a rotating unit for continuous production by gas chromatography and its applications

Abstract An apparatus for a continous gas chromatographic process is presented; its principles of operation have already been described by M. Taramasso et al. 1–6 The main features of the process are: efficiency at least equal to tht of an analytical column, possibility of obtaining several components at the same time or a single peak in many traps, with a high-grade central fraction, and feed rates up to 400 ml/h.

Selective adsorption properties of the surfaces of attapulgite and sepiolite

Abstract Representative samples of sepiolite and attapulgite, clay minerals of the hormite group characterized by a porous lattice, were tested as stationary phases in gas—solid chromatography. The selectivity and efficiency of such adsorbents are largely dependent upon differences in surface geometry and homogeneity. In gas analysis, the most interesting application of hormites appears to be the possibility of separating O 2 , N 2 , CO, CH 4 , CO 2 and light hydrocarbons by using a single short column. Configurational and steric isomers are easily resolved on hormites. The selectivity towards isomeric alkanes may be related to the different sizes of the open channels on the external surface of such minerals. The resolution between cis and trans forms of disubstituted cycloalkanes is very high. For instance, there is a complete separation of all the dimethylcyclopentane isomers, and very high relative volatilities are shown by the cis and trans forms of dimethylcyclohexanes. Efficiency values are such that the use of hormites in gas—solid chromatography has proved to be practical.

Preparative scale gas chromatography by a laboratory rotating unit : iv. separation of close boiling mixtures and crude reaction products

Abstract The effectiveness of preparative scale gas chromatography in the resolution of close boiling mixtures is compared with laboratory fractional distillation. Some examples of separations of close boiling hydrocarbon mixtures and crude reaction products are reported; these show the versatility, the high purity levels and the remarkable feed rates obtainable with the rotating unit. Moreover two examples are reported in which, by the use of a larger gas chromatographic apparatus, exceptionally high feed rates are obtained.