Separation and identification of porphyrin biomarkers from a heavy crude oil Zaap-1 offshore well, Sonda de Campeche, México

Abstract

The task to isolate metalloporphyrin compounds from crude oils is difficult, especially from reservoirs; the existence of well-known complexes homologous series type etioporphyrin (E), deoxophyloerythroetioporphyrin (DPEP), tetrahydrobenzodeoxoerythroetioporpyrin (THBD), benzoetio- porphyrin(BE) and benzodeoxoerythroetioporphyrin (BD) of vanadyl and nickel porphyrins, compounds found in crude oils around the world makes it hard. This includes natural porphyrins found in Mexican crude oils such as Ixtal-101, Zaap-1 and Ceh-1 from Sonda de Campeche, México, were the vanadyl porphyrins mixtures of the main series Etio and DPEP have also been reported elsewhere [14]. The objective of this investigation was to isolate porphyrins isomers from a single heavy crude oil from the Sonda de Campeche area, in México, and is based on the modified reversed-phase high-performance liquid chromatography method (RP-HPLC) [9, 11, 12]. Forty vanadyl porphyrin isomers, such as nickel porphyrin complexes were successfully isolated for the first time from heavy crude oil Zaap-1, through an exhaustive work which included a process of demetallization of vanadyl porphyrins to transmetallization to nickel porphyrins, in agreement with other methods [9, 11, 12, 14]. Further purification was achieved by thin-layer chromatography (TLC) with small glass chromatographic columns, packed with silica gel; then the purified isomers were analyzed and identified by electron impact mass spectrometry (EI-MS), providing the following results: from the Etio series seven isomers C 27 E , C 28 E , C 29 E , C 30 E , C 31 E , C 32 E , C 33 E were identified. From DPEP series six isomers C 29 D , C 30 D , C 31 D , C 32 D , C 33 D , C 34 D were identified; from the BD series it was identified only 1 isomer of vanadyl from BD.