GB712644A - Improvements in or relating to manufacture of tetraethyllead - Google Patents

Abstract

<PICT:0712644/IV (b)/1> Tetraethyl lead is prepared by a continuous process which comprises feeding an alkali metal alloy of lead and a liquid ethyl ester of an inorganic acid to a reaction zone in excess over the quantity required to form tetraethyl lead, and agitating the mixture sufficiently to maintain the reacting and reacted solids in nonuniform distribution in a liquid so that the concentration of solids decreases from the bottom of the reactor upwards, the liquid comprising a solution of tetraethyl lead in the ethylating agent, said liquid being of uniform composition throughout the reaction zone, and withdrawing at a point remote from the bottom of the reaction zone a slurry of solids in the liquid, said solids being more highly ethylated or contain more reacted solids than the solids at the bottom of the reactor. The ethylating agent may be ethyl chloride, bromide or iodide, or diethyl sulphate. The alloy may be fed to the reactor as a comminuted solid or as a liquid. Monosodium-lead alloy is the preferred lead alloy although other lead alloys may be used, e.g. the disodium-lead alloy or other lead alloys containing greater or smaller proportions of sodium. Other alkali metals may replace or partially replace sodium in the lead alloys, e.g. potassium may be present. Ethyl chloride and monosodium-lead alloy may be fed to the reaction zone in the proportion of at least 2 parts by weight of ethyl chloride to 1 part by weight of alloy, the preferred point at which the slurry of solids is withdrawn being in the upper 50 per cent of the total depth of the reaction mass so that a liquid to solids weight ratio within the reaction zone of at least 3 : 1 to 5 : 1 is obtained. A suitable apparatus for carrying out the process is shown in the Figure. Ethyl chloride is fed from tank 2 through pipe 3 and the alloy is fed from hopper 4 via the pressurized chamber 5 and conveyer 8 into the reactor 1, both the hopper and pressurized chamber having an inert gas atmosphere. The reactor is fitted with a jacket 23 for a heat transfer media introduced through line 24 and discharged from 25. Propeller type agitators 29, 30 and 31 and bottom plate element 32 are mounted on shaft 33. The ethylated mixture is discharged through one or more nozzles 131, 132, 133, 134, 135 and 136 into the solids-liquid separator 16, the solids being removed through line 17 and the liquid phase is removed through line 18 for the recovery of tetraethyl lead. In an example, tetraethyl lead is prepared from ethyl chloride and monosodium-lead alloy in the apparatus illustrated in the Figure.