Patent GB-1088415-A (GB)
Title: Stabilization of alkylleads
IPC: C10L1/10
Filed: 1964-10-30
Abstract: A fuel for use in an internal combustion engine may contain a thermally stabilized alkyl-lead composition consisting essentially of (a) a tetra-alkyl-lead compound or a mixture of tetra-alkyl-lead compounds of which compound or compounds at least 10% of the alkyl groups are methyl, the remaining alkyl groups, when the percentage of methyl groups is less than 100%, being ethyl; (b) ethylene dibromide or propylene dibromide or a mixture thereof as essentially the sole halohydrocarbon ingredient; and (c) a hydrocarbon having a boiling point of from 90 DEG  C. to 150 DEG  C. The dibromide is present in a proportion of from 0.2 to 2.0 moles per mole of tetra-alkyl-lead when from 10 to 15% of the alkyl groups are methyl groups, in a proportion of from 0.2 to 0.8 moles when from 20 to 90% of the alkyl groups are methyl groups, and in a proportion of from 0.1 to 0.8 moles when the alkyl groups are all methyl groups; the hydrocarbon is present in a proportion of from 2 to 40 parts by weight per 100 parts by weight of tetra-alkyl-lead when from 10 to 90% of the alkyl groups are methyl groups, preferably in a proportion of from 5 to 30 parts by weight per 100 parts by weight of tetra-alkyl-lead when from 10 to 15% of the alkyl groups are methyl groups, and in a proportion of from 15 to 40 parts by weight per 100 parts by weight of tetra-alkyl-lead when the alkyl groups are all methyl groups.  The hydrocarbon is either an alkane hydrocarbon, for example 2-methylhexane, 2,2,4 - trimethylpentane, n - octane or n-nonane, or a mononuclear aromatic hydrocarbon containing only aromatic unsaturation, for example toluene, xylene or ethyl benzene; in addition to these preferred hydrocarbons, the Specification lists other suitable hydrocarbons and hydrocarbon mixtures.  The dibromide constituent may include a minor proportion of 1,1-dibromoethane. The composition may include other stabilizer materials, for example 2-methyl - 2,4 - pentanediol, 2 - ethyl - 1,3-hexanediol, styrene, furfural and resorcinol.ALSO:A thermally stabilized alkyl-lead composition consists essentially of (a) a tetra-alkyl-lead compound or a mixture of tetra-alkyl-lead compounds of which compound or compounds at least 10% of the alkyl groups are methyl, the remaining alkyl groups, when the percentage of methyl groups is less than 100%, being ethyl, (b) ethylene dibromide or propylene dibromide or a mixture thereof as essentially the sole halo-hydrocarbon ingredient, and (c) a hydrocarbon having a boiling point of from 90 DEG  to 150 DEG  C.  The dibromide is present in a proportion of from 0.2 to 2.0 (preferably from 0.5 to 1.0) moles per mole of tetra-alkyl-lead when from 10 to 15% of the alkyl groups are methyl groups, in a proportion of from 0.2 to 0.8 moles when from 20 to 90% of the alkyl groups are methyl groups, and in a proportion of from 0.1 to 0.8 (preferably from 0.5 to 0.6) moles when the alkyl groups are all methyl groups; the hydrocarbon is present in a proportion of from 2 to 40 parts by weight per 100 parts by weight of tetra-alkyl-lead when from 10 to 90% of the alkyl groups are methyl groups, preferably in a proportion of from 5 to 30 parts by weight per 100 parts by weight of tetra-alkyl-lead when from 10 to 15% of the alkyl groups are methyl groups, and in a proportion of from 15 to 40 (preferably from 20 to 30) parts by weight per 100 parts by weight of tetra-alkyl-lead when the alkyl groups are all methyl groups.  The hydrocarbon is either an alkane hydrocarbon, for example 2-methylhexane, 2,2,4-trimethylpentane, n-octane or n-nonane, or a mononuclear aromatic hydrocarbon containing only aromatic unsaturation, for example toluene, xylene or ethyl benzene; in addition to these preferred hydrocarbons, the Specification lists other suitable hydrocarbons and hydrocarbon mixtures.  The dibromide constituent may include a minor proportion of 1,1-dibromo-ethane. The alkyl-lead composition may include other stabilizer materials, for example styrene, furfural, resorcinol, 2-methyl-2,4-pentanediol and 2-ethyl-1,3-hexanediol.  The alkyl-lead composition may be prepared by reacting a sodium-lead alloy with a methyl halide or with ethyl chloride and a methyl halide in a suitable ratio, the methyl halide preferably being methyl chloride, in the presence of a catalyst and separating the product from the reaction mass in the presence of the dibromide and the hydrocarbon, at least the dibromide having been added to the reaction mass after the reaction has taken place; the catalyst may be trimethyl aluminium, triethyl aluminium, methyl aluminium sesquichloride or a catalyst disclosed in Specification 1,018,218. Alternatively, the alkyl-lead composition may be prepared by effecting an interchange of ethyl and methyl groups in a methyl-ethyl mixed alkyl-lead compound in the presence of a redistribution catalyst, for example aluminium chloride, when the alkyl-lead compound is formulated with the dibromide and the hydrocarbon; a mixture of tetramethyl-lead and tetraethyl-lead thus may be treated to produce the five possible different methyl and ethyl tetra-alkyl-lead compounds.  The alkyl-lead composition, the tendency of which to decompose at a temperature of from 100 DEG  C. to 195 DEG  C. is inhibited, may be included in a fuel for use in an internal combustion engine.