Patent GB-1015268-A (GB)
Title: Improvements in and relating to the production of tetramethyllead
IPC: C07F7/24
Filed: 1963-08-19
Abstract: Tetramethyllead is prepared by the reaction of a sodium lead alloy with methyl chloride in the presence of a catalyst system including an aluminium containing component and an organic compound having at least one glycol ether group. The aluminium containing component used in proportions of 0.04-0.25 weight per cent based on the alloy may be a hydrocarbon aluminium compound having up to 10 carbon atoms per radical e.g. trimethyl aluminium triethylaluminium ethyl and methyl aluminium sesquichloride diethyl aluminium chloride ethyl aluminium chloride tri-n-propyl aluminium tri-n-butyl aluminium tri-isobutyl aluminium diisobutyl aluminium hydride triphenyl aluminium trioctyl aluminium diethylaluminium hydride and diethyl aluminium ethoxide or finely divided aluminium metal or an aluminium trihalide.  The hydrocarbon aluminium compound may be formed in situ by the reaction of an aluminium trihalide and a hydrocarbon metal compound e.g. from AlCl3 and Et4Pb. The glycol ether component in proportions of 1/4 mole to 5 moles per g. atom of aluminium, may be dihydrocarbon ethers of lower polyethylene glycols, i.e. those having up to 7 glycol residues per molecule, cyclic diethers, particularly those having two carbon atoms separating the ethereal oxygen atoms, and dialkoxy lower alkanes or mixtures thereof.  Hydrocarbon radicals may be aryl, cycloalkyl, alkaryl, aralkyl and particularly alkyl with up to ten carbon atoms per radical.  Specified examples of the glycol ethers are the diethyl, methyl ethyl, dimethyl, dipropyl, dibutyl, dihexyl and cyclohexyl ethyl ethers of diethylene glycol, the dimethyl, methyl ethyl, phenyl ethyl and cyclohexyl methyl ethers of ethylene glycol, the cyclopentyl butyl ether of triethylene glycol, the dimethyl and diphenyl ethers of tetraethylene glycol, dioxolane, 1:4-dioxane, methyl dioxolane and 2-methyl-1,4-dioxane.  The components of the catalyst may be added to the reaction vessel containing the finely divided alloy, particularly the monosodium lead alloy, separately in either order, or together after prior mixing, or one or both components may be added portionwise at intervals.  An inert liquid hydrocarbon, e.g. toluene, 2,2,4-trimethyl hexane or 1,2-dimethylbenzene, in proportions of 1/25 to 1/5 by weight based on the alloy, may also be present.  The temperature of the mixture is raised to at least 65 DEG  C., at least the stoichiometric quantity of methyl chloride is added, at once or portionwise, and reaction takes place at 85-110 DEG  C. for 1 to 7 hours.  Tetramethyllead is recovered from the reaction mass after cooling.ALSO:A catalyst for the preparation of tetramethyl lead by reaction of a sodium-lead alloy with methyl chloride includes an aluminium-containing component and an organic compound having at least one glycol ether group.  The aluminium-containing component may be an organo-aluminium compound such as a tri-alkyl aluminium, alkyl aluminium halide, alkyl aluminium alkoxide, alkyl aluminium hydride or triaryl aluminium, or finely divided aluminium metal, or an aluminium trihalide.  The glycol ether component, in proportions of 0,25-5 moles per g. atom of aluminium, may be the dehydrocarbon ether of a polyethylene glycol having up to 7 glycol residues per molecule, a cyclic diether, particularly one having 2 carbon atoms separating the ethereal oxygen atoms, a dialkoxy lower alkane or a mixture thereof.  The hydrocarbon radical may be aryl, cycloalkyl, alkaryl, aralkyl and particularly alkyl with up to 10 carbon atoms per radical.  The catalyst components may be introduced separately, in either order, or together after prior mixing, or one or both components may be added portionwise at intervals.  When the aluminium-containing component is a hydrocarbon aluminium compound, this may be formed in situ by the reaction of an aluminium trihalide and a hydrocarbon metal compound e.g. tetraethyl lead.