Evaluation of Analytical Procedures in the Determination of Trace Metals in Heavy Crude Oils by Flame Atomic Absorption Spectrophotometry

Mahmood M Barbooti

doi:10.4236/ajac.2015.64031

Abstract

In the present work, four trace metals, V, Ni, Cu and Fe, have been determined in five crude oil samples of Eastern Baghdad area, Iraq by flame atomic absorption spectrophotometry. The crude oils are characterized with API gravity values in the range, 25 - 15. The V/Ni ratios for the studied crudes were in the range 3.7 to 5.4 and indicated a typical of the sapropelic-type organic matter. The Ni and V contents were correlated with API gravity where an increase of metal contents with the decrease in the API values could be observed. The plots of V and Ni versus sulfur indicated linear correlation. This is attributed to the increase of porphyrinic structures of the metals. The method of direct dilution (DD) with organic solvent and the standard addition (SA) were evaluated as compared with standard dry ashing-acid dissolution (DA). In most cases the DD method gave V and Ni concentrations that are higher than DA and for the heavier crude oil (API = 15) the DD results were significantly smaller than those of the DA method. The SA method can be a good solution to determine the trace metals in heavy crude oils provided that the addition must not exceed the levels of the metal concentration in the diluted samples.

Highlights

The determination of metals in crude oils and its products is important for exploration, production and refiningHow to cite this paper: Barbooti, M.M. (2015) Evaluation of Analytical Procedures in the Determination of Trace Metals in Heavy Crude Oils by Flame Atomic Absorption Spectrophotometry
The distribution of trace metals in crude oils may be utilized to clarify potential genetic relationships between oils obtained from reservoirs in specific geologic provinces [1]
The trace metal contents of the crude oil samples were determined following their DA in triplicates and shown

Summary

Introduction

The determination of metals in crude oils and its products is important for exploration, production and refiningHow to cite this paper: Barbooti, M.M. (2015) Evaluation of Analytical Procedures in the Determination of Trace Metals in Heavy Crude Oils by Flame Atomic Absorption Spectrophotometry. (2015) Evaluation of Analytical Procedures in the Determination of Trace Metals in Heavy Crude Oils by Flame Atomic Absorption Spectrophotometry. For heavy crude oil upgrading, the high metals levels necessitate the processing to be costly, either through the high costs of hydrogen addition or high yield loss due to carbon rejection [6]. This process in turn requires the availability of reliable method for metal determination. The crude oil samples are characterized with a dominance of V over Ni with a V/Ni ratio of 3.7 to 5.4 which is indicative of typical of the sapropelic-type organic matter generating oil [24] Such range of V/Ni ratio is typical of Arab crude oils [29]. Both metals are related with API gravity with a power equation and the correlation coefficients were 0.8845 and 0.9794, respectively

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Methods

Conclusion