Patent GB-1089218-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 alkyllead composition substantially free from organic bromine-containing compounds and comprising (a) a tetraalkyllead compound or a mixture of tetraalkyllead 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) from 1.3 to 1.8, preferably from 1.5 to 1.7, moles of ethylene dichloride or propylene dichloride or a mixture thereof per mole of tetraalkyllead, and (c) at least 2 parts by weight of a hydrocarbon per 100 parts by weight of tetraalkyllead.  The hydrocarbon, which has a boiling point of from 90 DEG  to 150 DEG  C., is either on alkane hydrocarbon, for example 2-methylhexane, 2,2,4-trimethyl-pentane, n-octane or n-nonane, or a mono-nuclear 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 dichloride constituent may include a minor proportion of 1,1-dichloroethane. 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 alkyllead composition substantially free from organic bromine-containing compounds comprises (a) a tetraalkyllead compound or a mixture of tetraalkyllead 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) from 1.3 to 1.8, preferably from 1.5 to 1.7, moles of ethylene dichloride or propylene dichloride or a mixture thereof per mole of tetraalkyllead, and (c) at least 2 parts by weight of a hydrocarbon per 100 parts by weight of tetraalkyllead. The hydrocarbon, which has a boiling point of from 90 DEG  to 150 DEG  C., 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.  When the tetraalkyllead component is wholly tetramethyllead, preferably from 15 to 40, and advantageously from 20 to 30, parts by weight of hydrocarbon are present per 100 parts by weight of tetraalkyllead; when fron 10 to 90% of the alkyl groups of the tetraalkyllead component are methyl groups, i.e. when this component consists, for example, of tetramethyllead and tetraalkyllead or of the five possible methyl and ethyl tetraalkyllead compounds, preferably from 2 to 40, and advantageously from 5 to 30, parts by weight of hydrocarbon are present per 100 parts by weight of tetraalkyllead.  The dichloride constituent may include a minor proportion of 1,1-dichloroethane.  The alkyllead composition may include other stabilizer materials, for example styrene, furfural, resorcinol, 2-methyl-2,4-pentanediol and 2-ethyl-1,3-hexanediol.  The alkyllead 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 dichloride and the hydrocarbon, at least the dichloride 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 alkyllead composition may be prepared by effecting an interchange of methyl and ethyl groups in a methyl-ethyl mixed alkyllead compound in the presence of a redistribution catalyst, for example aluminium chloride, when the alkyllead compound is formulated with the dichloride and the hydrocarbon; a mixture of tetramethyllead and tetraethyllead thus may be treated to produce the five possible different methyl and ethyl tetraalkyllead compounds.  The alkyllead composition, the tendency of which to decompose at a temperature of from 100 DEG  to 195 DEG  C. is inhibited, may be included in a fuel for use in an internal combustion engine.