GB719832A - Improvements in or relating to selective adsorption of non-polar hydrocarbons - Google Patents

Abstract

A hydrocarbon is selectively adsorbed from a liquid mixture of non-polar hydrocarbons containing minor amounts of polar compounds by treating with silica gel which has been treated with a silane of the formula RkHmSiXn, where R is an alkyl, cycloalkyl, aryl, alkoxy, cycloalkoxy or aryloxy radical and at least one R contains at least 3 carbon atoms, X is a halogen or amino radical, k and n are whole numbers from 1 to 3, and m is a whole number from 0 to 2, the sum of k, n and m being 4, said silane being soluble in pentane at room temperature to the extent of at least 1 per cent by weight. Such a silica gel has reduced affinity for polar compounds such as water and organic sulphur, oxygen or nitrogen compounds present in hydrocarbon mixtures such as gasoline, kerosene, gas and lubricating oils and therefore maintains its activity when used to separate constituent, e.g. unsaturated, hydrocarbons. The silanes include diamino silanes having 2 R radicals, each of which is an alkoxy group of from 4-18 carbon atoms, e.g. a butoxy octadecoxy diamino silane, and trichlorsilanes, where R is an alkyl group of 5-8 carbon atoms. Preferably no hydrogen atoms attached to the silicon are present. Other silanes specified are propyl, amyl or octyl silicon trichloride; corresponding dichlor and monochlor silanes, the other chlorine atoms being replaced by hydrocarbon groups such as methyl, butyl, octyl or benzyl; similar compounds wherein hydrocarbonoxy replaces hydrocarbon, bromine replaces chlorine or amino replaces chlorine. Silica gel, desirably after drying, may be treated with the silane, preferably as a 0.5-15 per cent solution in a hydrocarbon, e.g. pentane or benzene. Heating to about 200 DEG F. or higher fixes the silane, and excess may be removed by solvents. The adsorbent is used as a fixed or moving bed in known manner. Examples describe the treatment of silica gel with tert.-butoxy octadecoxy or di-tert.-butoxy diamino silane, amyl, octyl or phenyl trichlor silane, and compare the water repellency and selectivity for aromatic hydrocarbons with the untreated gel. Separation of aromatics from a naphtha fraction in a cyclic process, naphtha being followed by benzene to displace aromatics, is also described.ALSO:A hydrocarbon is selectively adsorbed from a liquid mixture of non-polar hydrocarbons containing minor amounts of polar compounds by treating with silica gel which has been treated with a silane of the formula Rk Hm Si Xn where R is an alkyl, cycloalkyl, aryl, alkoxy, cycloalkoxy or aryloxy radical and at least one R contains at least 3 carbon atoms, X is a halogen or amino radical, k and n are whole numbers from 1 to 3, and m is a whole number from 0 to 2, the sum of k, n, and m being 4, said silane being soluble in pentane at room temperature to the extent of at least 1 per cent. by weight. Such a silica gel has reduced affinity for polar compounds such as water and organic sulphur, oxygen or nitrogen compounds present in hydrocarbon mixtures, such as gasoline, kerosene, gas and lubricating oils and therefore maintains its activity when used to separate constituent, e.g. unsaturated, hydrocarbons. The silanes include diamino silanes having 2 R radicals each of which is an alkoxy group of from 4-18 carbon atoms, e.g. a butoxy octadecoxy diamino silane, and trichlorsilanes where R is an alkyl group of 5-8 carbon atoms. Preferably no hydrogen atoms attached to the silicon are present. Other silanes specified are propyl, amyl or octyl silicon trichloride; corresponding dichlor and monochlor silanes, the other chlorine atoms being replaced by hydrocarbon groups such as methyl, butyl, octyl or benzyl; similar compounds wherein hydrocarbonoxy replaces hydrocarbon, bromine replaces chlorine or amino replaces chlorine. Silica gel, desirably after drying, may be treated with the silane, preferably as a 0.5-15 per cent. solution in a hydrocarbon, e.g. pentane or benzene. Heating to about 200 DEG F. or higher fixes the silane, and excess may be removed by solvents. The adsorbent is used as a fixed or moving bed in known manner. Examples describe the treatment of silica gel with tert. butoxy octadecoxy or di-tert. butoxy diamino silane, amyl, octyl or phenyl trichlor silane, and compare the water repellency and selectivity for aromatic hydrocarbons with the untreated gel. Separation of aromatics from a naphtha fraction in a cyclic process, naphtha being followed by benzene to displace aromatics, is also described.