Patent GB-1069537-A (GB)
Title: Process for the separation of mixtures of more readily and less readily soluble compounds
IPC: C07C7/10
Filed: 1964-09-28
Abstract: A selective solvent for use in separating mixtures is a heterocyclic 5-membered ring compound having a pentavalent phosphorus atom and four carbons in the ring, the phosphorus atom also carrying an oxygen or sulphur atom linked by a double bond. The remaining valency of the phosphorus may be satisfied by a substituted or unsubstituted alkyl, alkaryl, aralkyl or aryl bound direct or via an oxygen, sulphur or nitrogen atom and the carbons in the ring may also contain such groups.  The ring may be saturated (phospholidines or phospholanes) or contain one double bond (phospholines). Specified are 1-oxo-1-methyl-, -1-ethyl-, -1-propyl-, -1-butyl-, -1-phenyl-, the corresponding alkyloxy or aryloxy compound, and the corresponding -3-methyl-, -3-ethyl-, and -3,4-dimethyl-substituted derivatives of -1-N,N-dialkylamino-phospholines and the corresponding phospholidines and thio compounds.  They preferably boil between 250 DEG  and 500 DEG  C.  Up to 10% wt. of water, based on dry solvent, may be added. Solvent extraction of mixtures containing hydrocarbons can be effected to separate more soluble from less soluble hydrocarbons or more polar compounds from hydrocarbons, e.g. phenols, cresols, thiophenes, from benzene or mercaptans or alkyl sulphides from hydrocarbon oil fractions.  Hydrocarbon solubility decreases in the order aromatics, cyclo-olefines, naphthenes, olefines, paraffins and pure aromatic hydrocarbons may be separated, e.g. from reformates, or oil fractions may be separated into aromatic-rich or non-aromatic-rich fractions. In separating hydrocarbons a solvent to oil weight ratio of 1-10:1 is used.  Conventional procedure is used preferably using a counter-solvent and stripping lesser soluble materials from the extract and recycling these before recovering the more soluble.  Extractive distillation may be used to recover aromatic hydrocarbons from liquid product separated from coke oven gases, e.g. using 0.5-20 parts by volume of solvent per part of mixture.  Acidic components are removed from gases, e.g. H2S, COS, SO2 and/or CO2 from natural gas, synthesis gas or refinery or flue gases.  The phosphorus compound is preferably used mixed with an amine, e.g. ethanolamine, diethanolamine, dimethanolamine, di-n-propanolamine, diisopropanolamine or dibutanolamines and also in the presence of 1-25% wt. of water based on the solvent mixture which may contain 5-70% wt. of amine and 30-95% wt. of phosphorus compound. Absorption is effected at 20-125 DEG  C. and 5-50 atm. abs. preferably in a rectified absorption column, i.e. heated, e.g. by a steam coil at the bottom, and the acidic compounds are stripped from the solvent at increased temperature and reduced pressure.  Gaseous hydrocarbons may also be separated, e.g. butadiene from gas mixtures also containing olefines and/or paraffins, using a countercurrent absorption process with these phosphorus compound solvents. missing page 242ALSO:A selective solvent for use in separating mixtures is a heterocyclic 5-membered ring compound having a phosphorus atom and four carbons in the ring, the phosphorus atom also carrying an oxygen or sulphur atom linked by a covalent bond.  The remaining valency of the phosphorus may be satisfied by a substituted or unsubstituted alkyl, alkaryl, aralkyl or aryl bound direct or via an oxygen, sulphur or nitrogen atom and the carbons in the ring may also contain such groups.  The ring may be saturated (phospholidines or phospholanes) or contain one double bond (phospholines).  Specified are 1-oxo-1-methyl-, -1-ethyl-, -1-propyl-, - 1 - butyl -, - 1 - phenyl -, the corresponding alkloxy or aryloxy compound, and the corresponding -3-methyl-, -3-ethyl-, and -3,4-dimethyl-substituted derivatives of -1-N,N-dialkylamino-phospholines and the corresponding phospholidines and thio compounds.  They preferably boil between 250 DEG  and 500 DEG  C.  Up to 10% wt. of water, based on dry solvent, may be added.  Solvent extraction of mixtures containing hydrocarbons can be effected to separate more polar compounds from hydrocarbons, e.g. phenols, cresols, thiophenes, from benzene or mercaptans or alkyl sulphides from hydrocarbon oil fractions.  An example describes the separation of pentyl mercaptan from heptane.ALSO:A selected solvent for use in separating gaseous mixtures is a heterocyclic 5-membered ring compound having a pentavalent phosphorus atom and four carbons in the ring, the phosphorus atom also carrying an oxygen or sulphur atom linked by a double bond. The remaining valency of the phosphorus may be satisfied by a substituted or unsubstituted alkyl, alkaryl, aralkyl or aryl bound direct or via an oxygen, sulphur or nitrogen atom and the carbons in the ring may also contain such groups.  The ring may be saturated (phosholidines or phospholanes) or contain one double bond (phospholines).  Specified are 1-oxo-1-methyl-, -1-ethyl-, -1-propyl-, -1-butyl-, -1-phenyl-, the corresponding alkloxy or aryloxy compound, and the corresponding -3-methyl-, -3-ethyl-, and -3,4-dimethylsubstituted derivatives of -1-N,N-dialkylaminophospholines and the corresponding phospholidines and thio compounds.  They preferably boil between 250 and 500 DEG C. Up to 10% wt. of water, based on dry solvent, may be added.  Acidic components may be removed from gases e.g. H2S, COS, SO2 and/or CO2 from natural gas, synthesis gas or refinery or flue gases.  The phosphorus compound is preferably used mixed with an amine e.g. ethanolamine, diethanolamine, dimethanolamine, di-n-propanolamine, diisopropanolamine or dibutanolamines and also in the presence of 1-25% wt. of water based on the solvent mixture which may contain 5-70% wt. of amine and 30-95% wt. of phosphorus compound.  Absorption is effected at 20-125 DEG C and 5-50 atm. abs. preferably in a rectified absorption column, i.e. heated, e.g. by a steam coil at the bottom, and the acidic compounds are stripped from the solvent at increased temperature and reduced pressure.  Gaseous hydrocarbons may also be separated, e.g. butadiene from gas mixtures also containing olefins and/or paraffins, using a counter-current absorption process with these phosphorus compound solvents.