Determination of Naphthenic Acid Profile in Ghana s Jubilee Oil Using Gas Chromatography-Mass Spectrometry

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Determination of Naphthenic Acid Profile in Ghana s Jubilee Oil Using Gas Chromatography-Mass Spectrometry A thesis presented to the DEPARTMENT OF NUCLEAR SCIENCES AND APPLICATIONS, SCHOOL OF NUCLEAR AND
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Determination of Naphthenic Acid Profile in Ghana s Jubilee Oil Using Gas Chromatography-Mass Spectrometry A thesis presented to the DEPARTMENT OF NUCLEAR SCIENCES AND APPLICATIONS, SCHOOL OF NUCLEAR AND ALLIED SCIENCES, COLLEGE OF BASIC AND APPLIED SCIENCES, UNIVERSITY OF GHANA By Ian Osuteye Jnr [ID NUMBER: ] BSc. (Ghana), 2011 IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF PHILOSOPHY DEGREE IN NUCLEAR AND RADIOCHEMISTRY JULY, 2015 i Table of Contents DECLARATION... v DEDICATION... vi ACKNOWLEDGMENT... vii LIST OF TABLES... viii LIST OF ABBREVIATIONS... xi ABSTRACT xiii CHAPTER ONE... 1 INTRODUCTION Background to the Study Research Problem Research Objectives Main Objective Specific Objectives... 6 CHAPTER TWO... 7 LITERATURE REVIEW NAPHTHENIC ACIDS OVERVIEW Naphthenic Acid Chemistry Sources of Naphthenic Acids Raw Ore and Crude Oils Aqueous Presence Coal Ecological complications Methodological Challenges Analytical Methods Naphthenic acid extraction ii 2.2.2 Quantification Analysis Physico-chemical Parameters CHAPTER THREE METHODOLOGY Ghana s Crude Oil Jubilee Oil Location of Ghana s Jubilee oil field Geology of the Oilfields Collection of Crude Oil Samples Analysis of Crude Oil Samples Physico-Chemical Parameters Determination of Sulphur Content Using X-ray Fluorescence Spectrometry (XRF) Determination of Flashpoint Using Pensky-Martens Closed Cup Method Determination of Water Content Using the Dean and Stark Method Determination of Pour point Determination of Density by Hydrometer Method Determination of Total Acid Number (TAN) Using Colour-Indicator Titration Determination of Viscosity Using Viscometers Determination of Naphthenic Acids Extraction of Naphthenic Acids ( NA s) from Crude Oil Sample Extraction of NA CHAPTER FOUR RESULTS AND DISCUSSION Physico-chemical Parameters American Petroleum Institute (API) Gravity Sulphur Content Water Content Flashpoint iii 4.1.5 Pour Point Viscosity Total Acid Number (TAN) Low Resolution GC-MS profile of Naphthenic Acid in Ghana s Jubilee Crude Relationship Between Physico-chemical Parameters and Naphthenic Acids Sulphur content and Naphthenic acid Total Acid Number (TAN), Sulphur content and Naphthenic acid 68 CHAPTER FIVE CONCLUSION AND RECOMMENDATION Conclusion Recommendations REFERENCES APPENDICES iv DECLARATION I, Ian Osuteye Jnr., do declare hereby that the work presented in this dissertation was carried out by me at the Department of Nuclear Science and Applications, School of Nuclear and Allied Sciences, College of Basic and Applied Sciences, University of Ghana, Legon, under the supervision of Dr. Dennis Kpakpo Adotey and Dr. Kwaku Kyeremeh. Signed... OSUTEYE IAN JNR (STUDENT) DATE... Signed... DR. DENNIS K. ADOTEY (SUPERVISOR) Signed... DR. KWAKU KYEREMEH (SUPERVISOR) DATE... DATE. v DEDICATION This work is dedicated to my Visionary Father, Mr. Osuteye Ian (Snr.) and my Cherished Mother, Mrs. Mercy Osuteye, whose Prayers, Encouragement, Mentoring, Assistance and Hardwork have pivoted me this far. vi ACKNOWLEDGMENT My sincere gratitude goes to the Almighty God Jehovah for taking me through this Institution and for his guidance in making this project a success. I am also grateful for the good will and generosity of my supervisors; Dr. Dennis Kpakpo Adotey and Dr. Kwaku Kyeremeh for their outstanding efforts in supervising me through their strong willed perseverance, sense of fairness and openness they exhibited. It is through them that the nucleus of this work was drawn. I also wish to extend the warmest of gratitude to Mr. Ian Osuteye Snr, Mrs. Mercy Osuteye, Ms Elaine Osuteye and Ms Naa Norkor Osuteye, whose support and prayer has brought me this far. I will also like to thank the staff of Ghana Standards Authority (GSA), especially Mr. Samuel Adu, Mr. Samuel Kofi Mensah, Ms Millicent Kusi and Mr. Paul Osei-Fosu who assisted me in the analysis of my samples at the Petroleum and Pesticide Residue Laboratories.Finally, I would like to acknowledge the debt I owe my course mates and colleagues for their immense contribution towards this work especially Philip Odonkor, Charles Ansre, David Larbi, Suraj Sam Issaka, Randy Boateng, Maruf Abubakar, Abdullah Suhini, John Gyenfie, Frank Boakye-Antwi and Sylvester Ewordu. I would also like to express my appreciation to Mr. Samuel Larbi of Tema Oil Refinery (TOR). Their commitment, ideas and enthusiasm drove me to the completion of this work. Thanks also to Mr. Clemence Yao Baba (Headmaster, Our Lady of Mercy Senior High School, Tema), for his support and perceptive advice. vii LIST OF TABLES Table 2.1 Molecular weights (M.W) of different z series and n families of Naphthenic Acids (C n H 2n+Z O 2 )... 9 Table 2.2 Physical and Chemical Properties of Naphthenic Acids Table 2.3 Industrial uses of Naphthenic acids Table 4.2 Country of origin of crude oils Appendix Table A Titre Values for Total Acid Number Table B Sulphur Content measurement (XRF) Table C Data on some Crudes in the world viii LIST OF FIGURES Fig 2.1 Examples of classical structure of NAs... 8 Fig 3.1 A map showing the eleven blocks auctioned in Ghana s offshore waters Fig 3.2 A map showing the geographical position of the Jubilee oil field Fig 3.3a FPSO crude oil in sample container Fig 3.3b Bonny light crude oil in sample container Fig 3.4a Sulphur meter RX 620 SA Fig 3.4b Jigs for sample preparation Fig 3.4c Sample being prepared using jigs Fig 3.5a Pensky-Martens closed cup apparatus Fig 3.5b Fire application in the sample test cup during Flashpoint determination Fig 3.6a Dean and Stark set-up Fig 3.6b Glass trap at point of insertion with glass still Fig 3.6c Reflux condenser at point of insertion with Glass trap Fig 3.7a SETA Cloud and Pour point refrigerator Fig 3.7b Crude oil in a test jar with thermometer for analysis Fig 3.7c Pour point determination in progress Fig 3.9a Determination of reference temperature of crude oil sample Fig 3.9b Density etermination of crude oil sample Fig 3.9c Density determination of distilled water Fig 3.10 Schematic Diagram of TAN determination Fig 3.11a Weighed and labelled test sample Fig 3.11b Standard Reagents Fig 3.11d Titrands Fig 3.11c Titration with std. alc. KOH Fig 3.12a Viscometer apparatus Fig 3.12b Viscometer Fig 3.13 Flow chart of the extraction, derivatization and sample clean-up of NA Fig 3.14a Separatory funnel for extraction of NA ix LIST OF FIGURES (CONT.) Fig 3.14b Concentrating hexane phase using rotary evaporator Fig 3.14c Concentrate extract Fig 3.14d Set-up for esterification reaction Fig 3.14e Glass vials containing extract and ester for GC-MS analysis Fig 3.14f GC-MS instrument Fig 4.1 Comparison of API gravity of Jubilee and Bonny light crudes to other crudes in the world...55 Fig 4.2 Comparison of Specific Gravity of Jubilee and Bonny light crudes to other crudes in the world Fig 4.3 Comparison of the Sulphur content in Jubilee and Bonny light crudes to other crudes in the world Fig 4.4 Comparison of Pour Point of Jubilee and Bonny light crudes to other crudes in the world Fig 4.5 Comparison of the Kinetic Viscosities of Jubilee and Bonny light crudes to other crudes in the world Fig 4.6 Comparison of the TAN of Jubilee and Bonny light crudes to other crudes in the world Fig 4.7 Naphthenic Acid peaks and analysis from MS Work Station software Fig 4.8 Schematic diagram of the fragmentation patterns and their corresponding masses Fig 4.9 A chromatogram of the esterified hexane extract Fig 4.10 A chromatogram of the hexane extract x LIST OF ABBREVIATIONS ASTM American Society for Testing and Materials API American Petroleum Institute DCM Dichloromethane EPA Environmental Protection Agency ESI-FTICR-MS Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry FH Hexane Fraction FPSO Floating, Production, Storage and Offloading FTIR Fourier Transform Infra-red Spectrometer GC-MS Gas Chromatography-Mass Spectrometer GSS Ghana Statistical Service GNPC Ghana National Petroleum Company KV Kinematic Viscosity LREI GC-MS Low Resolution Electron Ionization Gas Chromatography Mass Spectrometer NA Naphthenic Acid NFPA National Fire and Protection Association xi LIST OF ABBREVIATIONS (CONT) OSPW Oil Sand Processed Water PP Pour Point RD Relative Density SC Sulphur Content SG Specific Gravity TAN Total Acid Number USEIA United States Energy Information Administration UV-Vis Ultraviolet-Visible xii ABSTRACT Crude oil is the life-blood of the global economy. Its importance stems from the fact that it is a base product for a wide variety of goods [Drugs, Plastics, Liquefied Petroleum Gas (LPG)]. The oil discovery (over 3 billion barrel reserves in hydrocarbon and gas), about 60 km offshore between the Deepwater Tano and Cape Three Points Block in South western Ghana is a valuable natural asset and it has the potential of boosting the Ghanaian economy. During petroleum processing, various waste products are generated. One of such products is Naphthenic acids (NA). Naphthenic acids are organic acids naturally occurring in crude oil and a constituent of waste associated with oil refinery. Naphthenic acids serve as biomarkers for identification of the source of crude oil. The presence of Naphthenic acid in the aquatic environment causes toxic effects due to their weak biodegradable nature; the toxicity of Naphthenic acids depends on the class of Naphthenic acids present in the crude oil. The study assessed the profile of Naphthenic acids in Ghana s Jubilee crude oil using Low Resolution Electron Impact Gas Chromatography Mass Spectrometry (LREI-GCMS) after isolation of Naphthenic acids in the Jubilee oil by a modified Kupchan s Partitioning Process. The Mass Spectrometric (MS) Work Station Software was used for the identification of the Naphthenic acids present in the Jubilee crude oil. The quality of the Jubilee oil was also evaluated through the use of some key physico-chemical parameters [Total Acid Number (TAN), Sulphur Content, Viscosity, Pour Point, Flashpoint, Water Content and Densities] based on the American Standards for Testing and Materials (ASTM, 2007). The Total Acid Number was determined by Colorimetric Titration (ASTM D974); Sulphur Content by X-ray Fluorescent Spectrometry (ASTM D4294); Pour Point by the use of the SETA cloud and xiii Pour Point Refrigerator Technique (ASTM D97); Viscosity by Gravity Timed Method (ASTM D445); Density by the Hydrometer Method (ASTM D1298); Flashpoints by the Pensky-Martens Closed Cup Method (ASTM D93); and Water Content by Distillation (ASTM D95). The results for the physico-chemical analysis revealed that, the Jubilee crude has a Flashpoint of 80.5 ⁰C, Density of ⁰API, Pour point of -15 ⁰C and Sulphur content of wt%. The Total Acid Number (TAN) for the Jubilee crude oil was 0.58 mg KOH/g crude; Viscosity of cst at 50 ⁰C and a negligible Water content. Based on National Fire Protection Association (NFPA 30) and American Petroleum Institute (API) classification standards, the results for the physico-chemical parameters indicates that Ghana s Jubilee is combustible, light and sweet crude with relatively high Acid content, low Pour point and Viscosity. The analysed (using MS Work Station Software) LREI-GCMS chromatogram identified two Naphthenic acids, a couple of homologues belonging to the monocyclic ring family(z = 2). The m z peaks of these acids were found at and These masses correspond to molecular formulas (C 10 H 17 O 2 ) and (C 18 H 17 O 2 ) respectively. The Naphthenic acids were identified as Metaethyl-3-cyclopentylpropanoic acid, (C 10 H 17 O 2 ) and Metaethyl-3- cyclopentylbutanoic acid, (C 11 H 20 O 2 ) xiv CHAPTER ONE INTRODUCTION 1.1 BACKGROUND TO THE STUDY Crude oil is the life-blood of the global economy. Crude oil has been regarded as one of the important non-financial commodities in the world and it supplies 40 percent (40%) of the world s total energy needs (more than any other single commodity) [Hubbard, 1998]. Crude oil s importance stems from the fact that it is the base product for a number of indispensable goods, including gasoline, automobile components, liquefied petroleum gas (LPGs), medicines, polyesters, household interiors, jet fuel and plastics (Khaleef, 2011). Due to the pre-eminent role of crude in the global economy, crude oil makes for great investment. Ghana discovered oil in 2007 in commercial quantities. The oil deposits which have a total proven reserve of about 3 billion barrels (480,000,000 mᵌ) are found in four main regions of sedimentary basins: Tano-Cape Three Points Basin (Western Region), Saltpond/Central Basin (Central Region), Accra-Keta Basin (Eastern Region) and the Voltarian Basin (Northern Region). The oil field, named Jubilee, is located 60 km offshore between the Deepwater Tano and Cape Three Point block. Commercial production of the Jubilee crude oil started in The production is centered about 85,000 barrels per day (13,500 mᵌ/d) [Kokutse, 2007; Owusu and Nyantakyi, 2013]. 1 Crude oil is not homogenous and its characteristics vary widely from oilfield to oilfield, from well to well in the same oilfield; the depth of the well, and the year of production. There is therefore the need for constant monitoring of the physicochemical properties of the crude oil including the Sulphur content, Flash Point, Water Content, Pour Point, Density, Total Acid Number (TAN) and Viscosity (Cao, 1992). Understanding the physicochemical properties of crude oil is essential for quality assessment, formulation process such as production, refinery, storage, transportation, environmental behaviour monitoring and effects. Additionally, knowledge of the physico-chemical properties provide valuable insight into pressing environmental concerns globally because of toxic effects when crude oil invades aquatic ecosystems either from accidental spills or normal commercial activities (Martnez-Jernimo and Villase Cor, 2005). Naphthenic acids are natural constituents of petroleum, where they were thought to have evolved from anaerobic microbial degradation of petroleum hydrocarbons (Tissot and Welte, 1978; Meredith et al., 2000; Watson et al., 2002). These are primarily the organic acids in crude oil (Meredith et al., 2000). Naphthenic acids account for as much as 4% of raw petroleum by weight (Barrow et al., 2003). Naphthenic Acids (NA) are a complex mixture of alkyl-substituted acyclic and cycloaliphatic carboxylic acids with the general chemical formula CnH 2 n+ Z O 2, (where n indicates the carbon number and z is a negative even integer signifying hydrogen deficiency (Holowento et al., 2002). 2 During petroleum processing, various waste products are generated. One of such products is Naphthenic acids (NA). NAs are responsible for certain problems observed in the refining of oil, such as the deactivation of the heterogeneous catalysts used in the refineries and their contribution to the salt deposits in the pipelines [(RCOO) 2 Ca] {Nordli et al., 1991}. They are also the primary toxicants in wastewaters associated with oil refineries and oil sands extraction (Avinash, 2013). Naphthenic acids might enter surface water systems through mechanisms such as groundwater mixing, erosion of riverbank oil deposits in oil-producing regions and processes involved in the enhanced recovery of crude oil (Brient et al., 1995). NA s act as natural emulsion stabilizers during degasification in oil production (Sjoblom et al., 2000). Their presence induces the decrease of the interfacial tension required for the formation of a stable emulsion. The chemical structure and the amount of NA s have an important role in regard to the interfacial tension (ɣ) values (Saab et al., 2005). They have surfactant properties and are the natural components in most petroleum sources including the bitumen present in the oil sands (Schramm et al., 2000; Lochte et al., 1955; Brient et al., 1995; Fan, 1991). NA s are considered as biomarkers related to oil maturation and biodegradation level of oil reservoir, because they are weakly biodegradable (Meredith et al., 2000; Headley et al., 2002; Dzidic et al., 1988). The NA s are also useful for fingerprinting fuel spills in the environment because they are more resistant to weathering than the non-polar alkane, isoprenoid, and alkylcyclohexane hydrocarbons (Rostad & Hostettler, 2007). Naphthenic acids can be solubilized to produce metal salts (e.g., sodium and copper naphthenates) that have industrial applications such as surfactants and fungicides for wood preservation (Davis, 3 1967; Herman et al., 1994; St. John et al., 1998). They are used in textiles, emulsifiers, paint driers, and adhesion promoters in the manufacture of tyres (Brient et al., 1995). Knowledge of the physicochemical properties and naphthenic acid profile of the Jubilee oil is essential in assessing the impact of the oil on aquatic habitat and refinery environments. Data on the naphthenic acid profile in Ghana s Jubilee is scarce and almost non-existent. It is therefore imperative that the naphthenic acids profile in Ghana s crude oil is characterized, as well as its physicochemical properties in order to provide reliable and accurate data, to enable governmental agencies like the Ghana National Petroleum Corporation (GNPC), Non-Governmental Organizations (with interest in oil exploration) and Environmental Protection Agency (EPA) regulate the activities of the oil exploration companies. In addition, such data will help interested agencies estimate the potential harmful effects of Naphthenic acids in the aquatic environment and the cost to be incurred during the refinery of the crude oil. Naphthenic acids in crude oil differ from one origin to another. Knowledge of the acid origin, their extraction, the quantitative and structural study, the phase equilibria of the water-oil-carboxylic acid systems, and the interfacial activity is required to better understand the organic acid chemistry (Saab et al., 2005). Further, toxic action and corrosivity is determined by the structure of the naphthenic acid, hence identifying the type of naphthenic acid present in crude oil and the amount is essential (Lo et al., 2006; Hsu et al., 2000). 4 1.2 RESEARCH PROBLEM The production of Jubilee crude oil holds the promise of boosting the economy of Ghana. A survey conducted by Reuters show that Ghana s economy could grow at about 14.7 % in 2011; one of the world s fastest growth rates, boosted by oil production (Ndaba, 2010). This will result in development in infrastructures in areas near the oilfield as well as provide manpower to meet the demands of production and possible refinery of the oil increasing government revenues by a quarter. It is going to impact local businesses and enhance tourism in suburbs of the oil field (Asafu-Adjaye, 2010). However production of the oil has risk associated with it; such as oil spillage, fire hazards, and corrosion of refinery units and emissions of poisonous gases. These risks can be highly toxic and can cause a long-lasting, damaging impact to surrounding neighbourhoods, waterways, commercial, agriculture and industrial areas. This proposed research aspires to explore some properties of the crude oil that affect production units, pollute the environment and pose health hazards to workers and the public. To achieve this, physico-chemical parameters of Ghana s Jubilee oil will be assessed to generate data. The data generated will help in the formulation of appropriate policy interventions to safeguard workers, indigenes, equipment, the environment and the ecosystem at large. 5 1.3 RESEARCH OBJECTIVES Main Objective The study endeavours to assess the naphthenic acid profile and to characterize the classes of naphthenic acids in Ghana s Jubilee oil Specific Objectives (a) To classify the quality of Ghana s Jubilee oil based on its physico-chemical properties compared with global standards. (b) To determine the naphthenic acids in Ghana s Jubilee oil using Gas Chromatography coupled with Mass Spectro
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