Patent GB-645826-A (GB)
Title: A process for refining hydrocarbon oil
IPC: C10G17/06
Filed: 1946-12-04
Abstract: <PICT:0645826/III/1> Mineral oils are refined by introducing, in a primary treating stage, fresh concentrated sulphuric acid, or suitably concentrated sulphuric acid from a subsequent stage or a suitable mixture of both into a stream of oil to be refined, causing the acid to act upon the oil at a temperature not exceeding 20 DEG C. for a period not exceeding four minutes, whereby only the more unstable components of the oil are dissolved by the acid, while substantially avoiding water yielding reactions between these components and the acid, then passing the oil and acid mixture through a centrifuge to separate the mixture into two phases, one of which is pre-refined oil and the other an acid solution of the more unstable components of the oil, then subjecting the pre-refined oil to further treatment in two or more subsequent stages in each of which acid is added and the mixture separated by centrifuging into refined oil and an acid solution containing the less unstable and soluble components of the oil, the overall movements of the acid and oil relative to each other being countercurrent in the treatment stages following the primary treating stage.  The acid introduced in the first stage may constitute not more than 30 per cent by weight of the total acid used in the process which total may be 1-20 (usually 5-12) per p  cent by weight of the oil.  When refining viscous oils the oils may be mixed with an inert diluent of lower viscosity than the oil itself and having a final boiling point sufficiently below the initial boiling point of the oil to be treated to enable the diluent to be removed from the oil by fractional distillation. The solvent may be a light paraffinic hydrocarbon or a mixture of such hydrocarbons, added in such a proportion-preferably not more than 25 per cent-that the viscosity of the mixture does not exceed 75 cst. In the illustrated example of the invention the oil to be refined is fed through a pipe 1 into a mixer 2 where it is mixed with a small proportion of concentrated sulphuric acid entering the mixer through a pipe 3 and/or 33, during 1-4 minutes.  The mixture is then passed through a pipe 4 to a centrifuge 5 where the acid extract solution is separated from the oil and discharged through a pipe 6 into a tank 7. The pre-refined oil from the centrifuge 5 is passed to a second mixer 12 where it is once more treated with sulphuric acid and from whence the mixture passes to a centrifuge 14 where the acid extract solution is separated from the oil and discharged through a pipe 15.  The oil passes to a mixer 17 where the acid treatment is repeated and the acid-oil mixture is passed to a centrifuge 19, whence the separated oil is taken to a mixer 21.  Here the final acid treatment takes place and the mixture is separated in a centrifuge 23, from which the raffinate is discharged through a pipe 24.  The acid extract solution discharged from the centrifuge 23 is conducted to the mixer 17 and that from the centrifuge 19 to the mixer 12 to be finally discharged from the centrifuge 14 into the pipe 15 from whence part of the acid extract solution passes to the tank 27, the remainder being conducted to the mixer 2.  In continuous operation the extract solution in the tank 27 may be regenerated by treatment with a solvent for the hydrocarbons, the solvent entering through a pipe 28.  The hydrocarbon solution is drawn off through a pipe 29 and is passed to a distillation plant for recovery of the solvent and the hydrocarbon extract, while the recovered concentrated acid is passed through piping 30 and 31 to the mixer 21.  Fresh acid to make up for losses is supplied through a pipe 32.  The mixer 2 is also connected, by means of the pipe 33, to the fresh acid supply pipe 32 so that fresh acid can be used when starting up the plant.  The acid extract solution in tank 7 is diluted with water supplied by pipe 8 causing the solution to separate into an oil phase which is discharged through a pipe 9 and a dilute sulphuric acid phase containing sulphonic acids which is discharged through pipe 10 and usually discarded.  The Specification as open to inspection under Sect. 91 refers also to the treatment of mineral oil products and the use of an acid refining agent such as chloro-sulphonic acid or fluorosulphonic acid.  No limit is imposed on the temperature or time during the first stage of the treatment of the oil with the acid refining agent, neither is the separation of the oil and the acid refining agent restricted to the passage of the mixture of the two through a centrifuge.  This subject-matter does not appear in the Specification as accepted.