Patent GB-745858-A (GB)
Title: Improvements in or relating to chemical processes and apparatus therefor
IPC: C07F9/165
Filed: 1953-10-07
Abstract: Dithiophosphoric acid esters are prepared by circulating in a closed system a slurry of a phosphorus sulphide in a liquid containing an organic hydroxy compound, e.g. an alcohol, and a major proportion of an inert liquid, e.g. the reaction product, introducing one of the reactants at a rate such that at all points of the system the amount of phosphorus sulphide is in excess of that required for complete reaction, and withdrawing the product at about its rate of formation (see Group III).  As described the addition of phosphorus sulphide is automatically controlled (see Group XXXV) according to the density of the slurry, and the alcohol feed is maintained constant.  Phosphorus pentasulphide is the preferred reagent, but the di-, trisesqui-, and heptasulphides may also be used.  Suitable alcohols are (a) aliphatic monohydric alcohols ranging from methyl alcohol to octadecyl alcohol; (b) cycloaliphatic monohydric alcohols including cyclopropanol, cyclohexanol and its alkyl derivatives, cycloheptanol, hydrogenated naphthols, tetrahydrofurfuryl alcohol, hydrogenated phenols, bornyl alcohols, menthyl alcohols, and cholesterol; (c) terpineol, cyclobutyl and cyclohexyl carbinols, hydrogenated benzo- and acetophenone; (d) aliphatic and cycloaliphatic dihydric alcohols from ethylene glycol to decandiols, hexahydro-hydroquinone, and hexahydro-resorcinol; (e) glycerol, pentaerythritol, and tetramethylol cyclohexanol.ALSO:A reaction between a solid and a liquid to form a liquid product is carried out by circulating a slurry 1 of the solid in a liquid, the major portion of which is inert to the reaction, from reactor 2 through separator 12, pump 14, and line 9, back to the reactor, and introducing one of the reactants at a rate such that at all points of the circulating system the amount of solid reagent is in excess of that required for complete reaction; a jacket surround <PICT:0745858/III/1> ing the reactor 2 maintains the required temperature and liquid product is withdrawn by decantation from separator 12.  The inert liquid may be the reaction product.  The amount of solid is suitably at least four and not more than twenty times the minimum amount for reaction.  As shown solid reactant is introduced from hopper 4 and liquid reactant at 8; the product collects in receiver 13; if the inert liquid is other than the reaction product, it is separated in flash evaporator 60, condensed in cooler 18, and returned to the reactor.  Gas given off during the process also passes through cooler 18 via lines 14A, 15, 16, 21. A stirrer 3 is provided in reactor 2, and a weir 10 maintains the level of the slurry constant.  Two nitrogen probes 23 are arranged in reactor 2, one in the gas space and the other at the bottom of the reactor.  These probes lead to a densometer (Fig. 2, not shown), for measuring the density of the slurry; if the specific gravity of the solid reagent is greater than that of the liquid reagent, the measurement indicates the relative proportions of solid and liquid in reactor 2.  By means of an electrical circuit (see Group XXXV) changes in density automatically control operation of motor M and thus the amount of solid fed to reactor 2.  Alternatively pneumatic and hydraulic control systems may be provided, for example to control the liquid reagent feed while maintaining the solid feed constant.  The reaction of a phosphorus sulphide with an organic hydroxy compound, e.g. an alcohol, to form a dithiophosphoric acid ester, is described (see Group IV(b)).