Patent GB-702876-A (GB)
Title: Improvements in the separation of acetylene from gaseous mixtures
IPC: C07C7/11
Filed: 1952-05-02
Abstract: <PICT:0702876/IV(b)/1> Acetylene is recovered from a gas containing the same by contacting the gas in an absorbing zone with an organic solvent having selective absorbing power for acetylene, removing the solvent from the absorbing zone and stripping it from the dissolved gases by heating and/or applying reduced pressure, wherein the solvent prior to the stripping process is led through a rectifying column in counter-current to the gas obtained in the stripping zone, and a stream of substantially pure acetylene is withdrawn at a point between the bottom and top of the rectifying column.  The gases arriving at the top of the rectifying column may be combined with the acetylene containing gas to be treated by the above process.  The solvent stripped of acetylene may be recycled to the absorbing zone. The stream of substantially pure acetylene may be further treated by contact with such an amount of organic solvent having selective dissolving for acetylene as is insufficient for dissolving the acetylene contained in the stream, e.g. the amount of solvent may be sufficient for dissolving the impurities better soluble than acetylene contained in said stream but insufficient for dissolving the whole of the acetylene, and the solvent may be branched off from the solvent stripped of acetylene prior to its return to the absorbing zone.  When the solvent thus used is stripped of the gases dissolved therein it may be recycled for contact with the substantially pure acetylene; the solvent may be led in a separate cycle with separate stripping.  The organic solvent may be an aliphatic carbonyl compound, e.g. an aliphatic ketone boiling above 100 DEG C., or an acetal of said carbonyl compound or of an aliphatic aldehyde, an aliphatic ether in particular an ether containing a hydrophilic group, e.g. a hydroxy group such as is contained in a glycol monoalkyl ether, a carboxylic acid ester containing a further hydrophilic group in the acid or in the alcohol radical, e.g. a lactic acid ester or a glycol monoester of a lower carboxylic acid, a lactone, e.g. g -butyrolactone or a homologue thereof, an acid amide in particular an alkylated acid amide such as a dialkyl formamide, an alkylated urea, a bis-dialkyl amide of a dicarboxylic acid and in particular a lactam such as a pyrrolidone or an N-alkyl or N-aryl derivative thereof or a corresponding homologous lactam.  In the Figure, the acetylene containing gas, either under normal pressure or under a pressure of a few atmospheres, enters through pipe A into a compressor B and then into the absorber C where it is contacted with the selective solvent preferably in counter current.  The solvent enters from pipe D and leaves the absorber C through pipe F, while the tail gas leaves through pipe E and may be subjected to a washing treatment to remove any traces of solvent vapour.  The solvent containing acetylene flows through pipe F into a rectifying column G which is preferably a multiplate column and then flows to the stripper H one or more of which may be used.  The gas from the stripper is led through pipe J into the bottom of the rectifying tower G so that it streams upward in counter current to the solvent coming from the absorber C.  Part of the acetylene contained in this gas leaves the rectifying column through line K accompanied by the impurities more difficulty soluble than acetylene.  Line K joins A so that the gas is again subjected to the purification process.  A stream of substantially pure acetylene is withdrawn through line L. The acetylene thus obtained may be further purified in washing column M where the solvent enters at the top and leaves at N, and the acetylene is withdrawn through line P.  The solvent stripped of gases leaves the desorber H through line S and is returned through line D to the absorber C after having been cooled to the absorbing temperature.  If the acetylene is to be further purified, part of the solvent coming from line S is branched off through line T to flow through line O into the washer M.  The impurities better soluble than acetylene are withdrawn through line R.  In the example, acetylene is extracted from an acetylene containing gas with g -butyrolactone.