Patent GB-880915-A (GB)
Title: A continuous process for preparing an aliphatic ether
IPC: C10L1/02
Filed: 1959-09-21
Abstract: Aliphatic ethers containing 6 to 10 carbon atoms are prepared by a continuous process comprising reacting water with a C3-5 aliphatic olefin or a C3-5 aliphatic olefin containing hydrocarbon mixture (in which the said olefin is essentially the only hydrocarbon hydratable to form an ether) in the presence of a substantially constant concentration of sulphuric acid in a hydration zone (in which the amount of olefin or olefin containing mixture introduced is such that the defined LHSV ratio does not exceed about 25), in which direct hydration is effected under such conditions of temperature, pressure and feed rate of the olefin or olefin containing hydrocarbon mixture that an organic phase comprising unreacted olefin is formed in the hydration zone, and a substantial part of this phase is liquid or pseudo liquid and acts as a selective solvent for the reaction products; separating the liquid organic phase and aqueous acid phase that are present in the hydration zone under conditions that maintain the organic phase liquid or pseudo liquid; treating the separated organic phase under hydrolysis conditions with water; separating the organic and aqueous phases present in the resulting hydrolysis mixture and recovering the C6-10 aliphatic ether from the separated organic phase.  The LHSV ratio is the volume of the liquid hydrocarbon feed per volume of sulphuric acid catalyst per hour.  The expression "pseudo liquid" denotes that when the reaction is effected at a temperature above the critical temperature of the olefin or olefin-containing hydrocarbons, the pressure and feed rate are such that the density of the liquid olefin or hydrocarbon mixture is maintained at or above the density of the material at the critical point.  The hydration is suitably effected with a hydrocarbon feed containing at least 25 mol. per cent. of the olefine and sulphuric acid of at least 35% concentration on a hydrocarbon-free basis, at temperatures of 60 DEG C. to 150 DEG C., and at elevated pressure where necessary.  The organic phase formed comprises unchanged hydrocarbon, ether and minor amounts of alcohol, mono- and di-alkyl sulphates and olefin polymer.  Hydrolysis of this phase is preferably effected at the temperature and pressure obtaining in the hydration but may be effected in the vapour phase.  Generally, an amount of water in excess of that required to hydolyse the alkyl sulphates is used. The aqueous acid phase so formed comprising sulphuric acid and some alcohol is preferably used as the source of water for the hydration thereby obviating the need for make-up acid in that stage. In an example, described with reference to suitable apparatus, a C3 cut of hydrocarbons, being predominantly of propylene, is reacted with 70% sulphuric acid at about 120 DEG C. under 900-950 p.s.i.g. pressure in continuous fashion as above described, with recycling of the aqueous phase from the hydration hydrolysis stage to the hydration stage.  Data is given showing suitable minimum pressures for the reaction of propylene at various other temperatures in the liquid or pseudo-liquid state.