(19)

(11)

EP 0 491 887 A1

(12)

(43) Date of publication: 01.07.1992 Bulletin 1992/27 (21) Application number: 91910367.0 (22) Date of filing: 05.06.1991

(51) International Patent Classification (IPC):  C07B 53/ 00( . ) C07H 9/ 06( . ) C07B 57/ 00( . ) C07H 13/ 12( . ) (86) International application number: PCT/GB1991/000894 (87) International publication number: WO 1991/018910 (12.12.1991 Gazette 1991/28)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU NL SE (30) Priority: 07.06.1990 GB 19900012682 (71) Applicant: THE BRITISH PETROLEUM COMPANY P.L.C. London EC2M 7BA (GB)

(72) Inventors: BANKS, Malcolm, Robert Edinburgh EH10 4LX (GB) CADOGAN, John, Ivan, George Richmond, Surrey TW10 6RN (GB) DAWSON, Ian, Michael Edinburgh EH8 9QB (GB) GOSNEY, Ian Edingburgh EH3 6RH (GB) HODGSON, Philip, Kenneth, Gordon Walton-on-Thames, Surrey KT12 1EL (GB) (74) Representative: Dodding, Robert Anthony  BP INTERNATIONAL LIMITED Patents Division Chertsey Road Sunbury-on-Thames Middlesex, TW16 7LN Sunbury-on-Thames Middlesex, TW16 7LN (GB)