Adsorption - A Tool in the Preparation of High-Purity Saturated Hydrocarbons

Abstract

Mixtures of isomeric saturated hydrocarbons, including geometric isomers, can be separated by adsorption on silica gel or activated carbon; activated alumina gives very little separation. Data are given on the separation of many binary synthetic mixtures, including paraffin-paraffin, paraffin-naphthene, and naphthene-naphthene types.Most of these systems give S-type isotherms on silica gel and U-type isotherms on carbon. The effect of hydrocarbon type and molecular weight on adsorbability is discussed. The theoretical basis for the results obtained is considered; they may be reasonably explained in terms of DURING the past decade the use of adsorbents, particularly silica gel, for the separation of hydrocarbons of different chemical types has become rather widespread. Previous work has shown that for hydrocarbons of similar molecular weight, the adsorbability, in general, increases with the number of double bonds per molecule. Thus, for example, small amounts of olefins or aromatics are removed from saturated hydrocarbons by percolation through silica gel.Silica gel has also been used where it has been desired to remove small amounts of nonhydrocarbon impurity from hydrocarbons.

Petroleum Hydrocarbons

“…Also, the fractionation of these components is unsymmetrical and, in both cases, the first portion of the filtrate contains the least strongly adsorbed component in a substantially pure condition; the last part of the hydrocarbon portion of the filtrate consists of a mixture which is substantially nonfractionating. The occurrence of nonfractionating mixtures is not uncommon with hydrocarbon systems as has also been observed by Hirschler and Amon (5). In terms of the theory previously given, the separation factor for a nonfractionating mixture is unity.…”

Simulated Moving Bed Technology: Overview and Use in Biorefineries

“…There is not much literature on adsorbate-adsorbent interaction. The only literature available is covered in patents [13][14][15][16][17][18][19][20][21]. With the little that has been established it has been concluded that the selection of adsorbent is more of an art than science.…”

“…As a rule of thumb silica and alumina are used for polar components. Equilibrium data published in the literature [13][14][15][16][17][18][19][20] can be used to identify a suitable adsorbent. The order of affinity of various chemical species is; saturated hydrocarbons, aromatic hydrocarbon, halogenated hydrocarbons, ethers, esters, ketones, amines, alcohols, carboxylic acids [10].…”

“…For non-polar components the widely used adsorbent is activated carbon or modified silica. Equilibrium data is available in the literature for activated carbon [13,14,[18][19][20]. Polymeric resins are mostly used in the pharmaceutical and food industry.…”

Adsorption

“…was described by Lindeboom (105). In the field of hydrocarbons, Hirschler and Amon (76) found that the highest purity was obtained for 2,3,3-trimethylpentane and 2,3,3-trimethylbutane as compared to all other methods of purification. They studied the adsorption of isomeric hydrocarbons, including geometrical isomers and binary mixtures of paraffin-paraffin, paraffin-naphthene, and naphthene-naphthene types, and recommended it as a general method of separation.…”