Patent GB-776436-A (GB)
Title: Process for the continuous production of synthetic lubricating oil
IPC: C10G50/02
Filed: 1953-06-17
Abstract: Normally liquid aliphatic olefinic hydrocarbons are polymerized by passing together with a contact oil upwardly through a substantially vertical reaction zone, the contact oil comprising or consisting of addition compounds of aluminium chloride with a hydrocarbon or hydrocarbons, and intimately admixing the olefinic hydrocarbons with the contact oil in a horizontal direction in the reaction zone in such manner as substantially to avoid an intermixing in the vertical direction, whereby olefinic hydrocarbons at any level of the reaction zone are substantially at the same stage of polymerization.  The reaction zone is preferably a cylindrical vessel or tube whose length is great relative to its internal diameter, e.g. the length may be 100 times the diameter.  Two or more such reaction zones may be connected in series.  Admixing of the olefinic hydrocarbons and contact oil may be effected by a stirrer extending over the total length of the reaction vessel and having on its axis horizontal plates at short distances apart.  Additionally, small blade stirrers may be provided between the individual plates.  A preferred stirring means comprises a rotating cylindrical body provided axially of the reaction zone and of a length not substantially less than the reaction zone.  For reaction tubes of 20 mm. diameter, the distance between the surface of the stirrer and the tube wall is preferably less than 5 mm.  The olefinic starting material may be obtained by thermal cracking of petroleum paraffinic hydrocarbons or waxes, or by hydrogenation of carbon monoxide, e.g. by the recycle synthesis over an iron catalyst. The feedstock may be given a pretreatment by passing over aluminium oxide at 350 DEG  C. to remove oxygen-containing compounds. The olefines used should generally have less than 18 carbon atoms. The synthesis is preferably effected with equal volumes of olefinic hydrocarbon and contact oil at 15-110 DEG C. with a residence time in the reaction zone of 3-15 hours, a time of not more than 6 hours being generally sufficient.  The product is removed from the upper part of the reaction vessel and passed into one or more settling vessels wherein it separates into two layers. The upper layer contains the polymerized product and is worked up by distillation after removal of residual aluminium chloride and after neutralization.  The lower layer consists of contact oil which is recycled to the reaction zone.  A portion of the contact oil, preferably 1-8 per cent of the contact oil in the synthesis, is continuously or intermittently withdrawn and replaced by unused or freshly prepared contact oil.  When operating with several reactors in series, the reaction may be transferred, without passing through a settling vessel, from one reactor directly into the next, whilst each reactor is maintained at a different temperature.  It is also possible to provide each of these reactors with a separate contact oil cycle, fresh contact oil being passed into the last stage whilst the corresponding amount of contact oil is withdrawn from the last reactor and passed to the preceding reactor, and so on.  By effecting the synthesis in a single reactor at 60-90 DEG  C. for 3-6 hours with equal volumes of olefine and contact oil, 1-2 per cent of contact oil being replaced by fresh contact oil per hour, a residual oil is obtained after distillation which boils at above 200 DEG  C. at 5 mm. and has a viscosity at 50 DEG  C. of 8-12 DEG  Engler.  For higher viscosity oils, two or more reactors are used in series with concurrent flow of olefines and contact oil through the reactors. The temperature in the first reactor is 15-25 DEG  C. and the residence time 8-12 hours.  The temperature in the second reactor is 50 DEG  C. for 1-3 hours.  From 3-5 per cent of the contact oil is replaced per hour.  For oils of low viscosity, two or more reactors are connected in series, each having a separate contact oil cycle.  The temperature in all the reactors is 90-110 DEG  C. with a residence time of 3-6 hours.  About 1 per cent of contact oil is replaced per hour.  Fresh contact oil may be prepared by reacting a portion of the olefinic starting material with aluminium chloride, or with hydrogen chloride and aluminium, at 40-100 DEG  C., preferably at 50-70 DEG  C.  The reaction mixture separates, on settling, into a lower layer of contact oil and an upper layer of hydrocarbons.  The saturated hydrocarbon byproducts of the polymerization process may be used instead of the olefines to produce the fresh contact oil.  The used contact oil withdrawn from the polymerization process may be worked up by extracting the lubricating oil constituents with hydrocarbons or by decomposing in water.  The used contact oil may also be employed for a pre-treatment of the olefinic starting material to remove diolefines and oxygen-containing compounds.  In examples, the starting material comprises hydrocarbon fractions obtained by hydrogenation of carbon monoxide, or by thermal cracking of paraffins obtained by hydrogenation of carbon monoxide, and is pretreated by passing over alumina at 350 DEG  C.  In Examples (1), (4), (5) and (6), the apparatus comprises two series-connected glass tubes in which a cylindrical stirrer rotates, the olefines and contact oil being fed to the base of the first tube and passing directly from the top of the tube to the base of the second tube; in Example (2), four series-connected tubes are used in the same way; in (3) two series-connected tubes are used, each having a separate contact oil cycle, the product from the first stage passing into one of two settling vessels alternately and the product from the second stage passing into one of two receivers. In all examples, the upper layer from the final settling vessel is fractionated by vacuum distillation giving first runnings consisting of saturated hydrocarbons, and a lubricating oil fraction.  The examples also describe in detail the production of contact oil from (a) olefines and aluminium chloride; (b) olefines, hydrogen chloride and aluminium; (c) saturated hydrocarbons and aluminium chloride; (d) saturated hydrocarbons, hydrogen chloride and aluminium.