GB832015A - Corrosion-inhibiting imidazolines - Google Patents

Abstract

Liquid hydrocarbon compositions comprise, as a corrosion inhibitor, an imidazoline derivative obtainable either by reacting sulphur, a phosphorus sulphide or a mixture of sulphur and phosphorus with an imidazoline of the general formula <FORM:0832015/III/1> and reacting the product with an alkylene oxide, or by reacting sulphur, a phosphorus sulphide or a mixture of sulphur and phosphorus with the reaction product of an alkylene oxide and an imidazoline as above defined, R representing an aliphatic hydrocarbon radical containing 8-32 carbon atoms and R11 a divalent hydrocarbon radical containing 1-8 carbon atoms. Sulphur is believed to become attached to a CH2 group in the ring. The alkylene oxides may contain 2-6 carbon atoms. The preferred alkylene oxide-imidazoline reaction products contain the amino group hydroxyethylated with 1-9 mols. of ethylene oxide. The hydrocarbons may be petroleum crudes or fractions thereof and the compositions may contain from 1 part per million to 1% by weight of the inhibitor. The inhibitors are stated to reduce corrosion of metal especially ferrous metal, caused by hydrocarbons existing in admixture with water and an acid or oxygen. Specific inhibitors described are (1) the product obtained by reacting aminoethyl-1-heptadeca-2-imidazoline with 3 mols. of ethylene oxide and then with 2 mols. of sulphur and (2) the product obtained by reacting the imidazoline named in (1) with 1/4 mol. P2S5 and then with 3 mols. of ethylene oxide and corrosion tests are described with one or other of these inhibitors in a petrol-water emulsion or in distillation of a petroleum crude. A comparative inhibitor described is obtained by reacting the imidazoline named in (1) with 3 mols. of ethylene oxide.ALSO:The invention comprises imidazoline derivatives obtainable either by reacting sulphur, a phosphorus sulphide or a mixture of sulphur and phosphorus with an imidazoline of the general formula <FORM:0832015/IV (b)/1> and reacting the product with an alkylene oxide, or by reacting sulphur, a phosphorus sulphide or a mixture of sulphur and phosphorus with the reaction product of an imidazoline of the above general formula and an alkylene oxide, R representing a C8-32 monovalent aliphatic hydrocarbon radical and R11 a divalent hydrocarbon radical containing 1-8 carbon atoms. It is believed that the sulphur becomes attached to a CH2 group in the nucleus. The reaction with the sulphur containing reagent may be effected by heat; when sulphur itself is used an aromatic solvent may be present. Alkylene oxides employed may contain 2-6 carbon atoms. The preferred imidazoline-alkylene oxide product is one in which the amino-group has been hydroxyethylated with 1-9 mols. of ethylene oxide. The final sulphurized products are useful as inhibitors (see Group III). In examples: (1) aminoethyl - 1 - heptadeca - 2 - imidazoline is condensed with 3 mols. of ethylene oxide in the presence of BF3 at 220-250 DEG C. and the product is reacted with 2 mols. of sulphur in boiling benzene solution and thereafter the solvent is evaporated off; (2) the imidazoline of (1) is heated with 1/4 mol. of P2S5 at 200 DEG C. and the product is condensed with 3 mols. of ethylene oxide at 220-230 DEG C. in the presence of BF3. Imidazolines of the above general formula are prepared by condensing acids of the formula RCOOH with triamines of the formula H2N.CH2CH2NH-R11-NH2 at 250-300 DEG C. until 2 mols. of water are removed.ALSO:Corrosion of metals, particularly of ferrous metals by liquid hydrocarbons, such as crude petroleum of fractions thereof, in the presence of water and acids or oxygen, is reduced by means of an imidazoline derivative obtainable either by reacting sulphur, a phosphorus sulphide or mixture of phosphorus and sulphur with an imidazoline of the general formula: <FORM:0832015/II/1> and reacting the product with an alkylene oxide, or by reacting sulphur, a phosphorus sulphide or a mixture of phosphorus and sulphur with the reaction product of an imidazoline of the above formula and an alkylene oxide, R being a C8-32 aliphatic hydrocarbon radial and R11 a divalent hydrocarbon radical containing 1-8 carbon atoms. Sulphur is believed to become attached to a CH2 group in the ring. The alkylene oxides may contain 2-6 carbon atoms and the preferred imidazoline-alkylene oxide reaction product contains the amino group hydroxy ethylated with 1-9 moles of ethylene oxide. The inhibitors may be present in the hydrocarbon oils in amounts of from 1 part per million to 1% by weight. Specified inhibitors are those obtained by reacting amino ethyl-1-heptadeca-2 imidazoline either with 3 moles of ethylene oxide and then 2 moles of sulphur or with 1/4 mil P2S5 and then 3 moles of ethylene oxide; tests are described illustrating their use in reducing corrosion of steel by an aqueous acidic petrol emulsion or by distilling vapours of a crude petroleum. The product obtained by reacting the above-named imidazoline with 3 moles of ethylene oxide is described as a comparative corrosion inhibitor.