Patent GB-760365-A (GB)
Title: Processes for the removal of wax from mineral oils
IPC: B60C15/06
Filed: 1954-06-11
Abstract: 760,365. Dewaxing mineral oils. NAAMLOOZE VENNOOTSCHAP DE BATAAF.. SCHE PETROLEUM MAATSCHAPPIJ. June 11, 1954 [June 15, 1953], No. 17303/54. Drawings to Specification. Class 91. Distillate mineral lubricating oil fractions and residual mineral lubricating oil fractions are dewaxed in turn in the same dewaxing plant, which is operated continuously, a solvent mixture consisting of a solvent and an anti-solvent possessing different average volatilities being cycled at an approximately constant rate through the system, and the recovery of the solvent mixture following dewaxing being effected by a plurality of sequential vaporization steps. The relative proportions of solvent and anti-solvent in the solvent mixture are adjusted immediately after beginning the dewaxing of the distillate fractions so that the solvent mixture is best suited to dewax distillate fractions and the relative proportions are again adjusted towards the end of the dewaxing of the distillate fractions so that the solvent mixture is again best suited to dewax residual fractions. Assuming the solvent mixture to consist of components A and B, the adjustment of the relative proportions of these in the solvent mixture is effected as follows:-The sequence of vaporization steps is arranged so that solvent mixture rich in A can, as desired, be diverted from one or some such steps to a storage zone Sa and solvent mixture rich in B can, as desired be diverted from other such vaporization steps to a storage zone Sb. The concentration of A in the circulating solvent mixture is increased at the beginning of the dewaxing of the distillate fractions by adding solvent mixture from Sa until the desired increase is attained and, at the same time, diverting a solvent mixture as described above to Sb. The concentration of B in the circulating solvent mixture is increased towards the end of the dewaxing of the distillate fractions by adding solvent mixture from Sb until the desired increase is attained and, at the same time, diverting a solvent mixture as described to Sa.. Apparatus for carrying out the process is described. The distillate fractions may include raffinates from the solvent extraction of mineral lubricating oil distillate fractions. Similarly, the residual fractions may include raffinates from the solvent extraction of deasphaltized short residues, which short residues have been obtained from the vacuum distillation of wax-containing mineral oil crudes or topped crude mineral oil stocks. Both solvent and anti-solvent may consist of a plurality of substances. Suitable solvent mixtures are benzene (solvent), and furfural (anti-solvent); benzene (solvent), and acetone (anti-solvent); toluene- and - benzene (solvent), and methyl ethyl ketone (anti-solvent); toluene (solvent), and methyl isobutyl ketone (anti-solvent); or liquid sulphur dioxide (solvent) and dichlorethylene (anti-solvent). In an example, the process is applied to the dewaxing in turn of a solvent-extracted mineral lubricating oil distillate and of a raffinate obtained by solvent extracting a deasphalted petroleum short residue, the solvent mixture being a blend of toluene and methyl ethyl ketone.