Journal of Applied and Industrial Sciences, 2014, 2 (1): 14-18, ISSN: (PRINT), ISSN: (ONLINE)

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1 Research Article 14 Separation of Naphthenic Acid from Sudanese Crude Oil Using Local Activated Clays. Saad, O.M* 1, Gasmelseed, G.A 2 and Hamid,A.H.M 3, (1-3) University, Of Science and Technology, Sudan, Department of Chemical Engineering. 1.* osmanmsaad@gmail.com gurashigar@hotmail.com hamidmustafa5@gmail.com. (Received: December 04, 2013; Accepted: January 29, 2014) Abstract: The acidity of Sudanese crude oil (mainly naphthenic acids) was reduced by activated local clays; the clays were activated by concentrated sodium hydroxide. The total acid number (TAN) of Fula high acid crude was (8.51 m KOH/g), and the TAN of Nile blend was (1.06 mg KOH/g), which can be reduced to (6.27 mg KOH/g) and (1.05 mg KOH/g) respectively, by activated clay of 3M NaOH composed mainly of muscovite as be explained by X-RD analysis. Index terms: Naphthenic acid (NA), Local clays, Total acid number, Sour crude, Corrosion. I. INTRODUCTION The greater growth of high TAN crude oil production and the increasing price of light sweet crudes encouraged refineries to raise the quality of sour crude to achieve maximum prices. Crude oil, is a complex mixture of organic compounds predominately composed of hydrocarbons, and often contains large amounts of other compounds such as organic and inorganic sulfur species, chlorides and nitrogen compounds, trace metals and naphthenic acids [1]. Total acid number, (TAN), is a quantitative measure of the naphthenic acid,(na). TAN is defined as the amount of potassium hydroxide (KOH) in milligram that required to neutralize one gram of the Crude oil Sample [2]. Naphthenic acids are a mixture of cyclo-paraffins with alkyl side chains ending with a carboxylic group. The low-molecular-weight naphthenic acids (8 12 carbons) are compounds having either a cyclopentane or a cyclohexane ring with a carboxyalkyl side chain. These compounds are normally found in middle distillates such as kerosine and gas oil. High boiling napthenic acids from the lube oils are monocarboxylic acids, (Cl4-Cl9) with an average of 2.6 rings. Naphthenic acids constitute about 50 wt% of the total acidic compounds in crude oils. Naphthenic-based crudes contain a higher percentage of naphthenic acids. Consequently, it is more economical to isolate these acids from naphthenic-based crudes [3]. Naphthenic acids are classified as carboxylic monoacids of the general formula RCOOH, where R represents any cycloaliphatic structure. Generally, the term naphthenic acid is used to account for all carboxylic acids present in crude oil, including acyclic and aromatic acids. Nearly all crude oils contain some naphthenic acids. Heavy crudes from geologically young formations have the highest acid content while paraffinic crudes usually have low acid content [4]. The corrosivity of naphthenic acids is significantly increased when the TAN is greater than 0.5mgKOH/g [5]. Organic acids in crude oil mainly consist of aliphatic acids, naphthenic acid, (NA), Phenols, Mercaptans, etc. And naphthenic acids, (NA), commonly comprise 85m% of acidic species in crude [6]. The general formula of acidic species in crude oil can be represented as C n H 2n +ZO 2 [7]. A Paper entitled aliphatic acids and monocyclic naphthenic acids accounted for a large proportion in petroleum carboxylic acids of the Dar crude. In their study they described Dar crude as a low-sulfur, highly acidic, and paraffinic-base crude oil with a low yield of light fractions and a high yield of heavy fraction. The researchers characterized the naphthenic acids of Sudanese crude sample as a typical monocarboxylic acids compounds (fatty acid and naphthenic acid). The majority of the naphthenic acid is tworing naphthenic acids with carbon number 26 to 34 [8]. When NA containing crude oils are processed in refineries, corrosion may occur, this type of attack is called naphthenic acid corrosion [9]. This type of corrosion is a well known problem and a major concern in crude oil processing. NAs present in crude oils are considered only to be a part of the problem and simple measures of corrosivity based on the TAN are insufficient [10]. The aim and objective of this research work is to separate naphthenic acid from sour crude oil through adsorption of the acid by local activated clays. II. MATERIALS AND METHODS Materials Sodium hydroxide (NaOH) with concentrations 2Mand 3M. Sudanese local clays were collected, from Omdurman province area. Distilled water. Crude oil f, Khartoum Refinery Company (KRC). Equipments Sieve shaker, electrical balance, and a digital thermometer, magnetic stirrer rating system, mortar and pestle electric oven, filter medium, and others.

2 15 Samples Preparation Three different samples of local clays denoted by (X,Y and Z) were collected,then were ground using a mortar and pestle to reduce the size as a fine particles., the small fine powder particle was passed through a sieves shaker mesh of 60 Mesh number. 40 grams of each Sudanese local prepared clays samples were weighted in three beakers, different concentration of Sodium hydroxide (KOH) exactly (0M, 2M,3M) were added to each beaker, when the sample was completely wetted with the alkaline solutions, the mixtures of alkali and clay was transferred into three necks round bottom flask. The temperature of the system was ad justified to be in the range of (80-90) C 0 and the time of activation was ad justified to be (3Hrs) for each sample. The settled activated samples were filtrated by using Buckner funnel, and then washed by using distilled water for three times. The activated sample were allowed to be dried over night by using normal electrical furnace at temp of 105C o. Finally the dried samples were ground and weighted. The activated samples were added to Sudanese High acid crude (Fula crude), and Nile blend crude. X-RD analysis shows that sample (X) is Muscovite; sample (Y) is also Muscovite, and sample (Z) is found to be Ziolite. Measurement Procedure of TAN: Following the procedure of ASTM standard method D664, the in-lab TAN measurement method was developed briefly, this measurement involves a non-aqueous acid-base potentiometric titration using a specific solvent mixture including toluene 50.0%, iso-propanol 49.5% and water 0.5% (v/v) which to dissolves the oil samples. A mv/ph meter (Oakton PH510 Series) was used to record the potential change. The major operation steps consist of the followings: Preparation of potassium acid phthalate (KHC 8 H 4 O 4 or KHP) standard solution heat KHP in oven at 80 C for about 10hrs to remove moisture. Accurately weigh the heated KHP and dissolve it into CO 2 -free pure water in a flask. Add water to the graduation of the flask and then calculate the mole concentration of the prepared solution. Preparation of alcoholic potassium hydroxide solution Add 6g of KOH to approximately 1L of anhydrous iso-propanol. Boil gently for 30min to increase the solubility of KOH in the solution. Store the solution overnight and then standardize the solution with the prepared KHP solution. Standardization of alcoholic KOH solution Standardize the solution with potentiometric titration of weighed quantities of KHP dissolved in CO 2 -free water. Preparation of oil sample Dissolve 1-5g oil sample in 125ml titration solvent (500ml toluene/495ml anhydrous iso-propanol/5ml water), filter the sample and transfer the prepared solution to a 250ml beaker, which is used as the titration vessel. Titration of KOH to oil sample Add suitable amount of KOH alcoholic solution and wait until a constant potential has been observed, then record the solution used and meter readings. When the sample was titrated close to the inflection point, add less drops of KOH and record the meter carefully. For each set of samples, make a blank titration of the titration solvent. 2 III. RESULTS AND DISCUSSION Three different samples of local clays denoted by ( X, Y and Z) were activated with different concentrations of sodium hydroxide of ( zero M, 2M,3M) for each sample. Then these were added to the crude oil to reduce their acidity. According to the results obtained from Tables(1-4) and Figures (1-4), different dosing of samples ( X0,X 2,3,and X 3,3), ( Y0,Y 2,3,and Y 3,3) and ( Z0, Z 2,3,and Z 3,3), were added to the high acid crude oil as acid reducing agent,to remove their naphthenic acid and to reduce their total acid number (TAN)., the experiments were taken place at the main laboratory of Khartoum Refinery Company (KRC), Sudan. It was found that, the TAN of Fula high acid crude was (8.51 mg KOH/g),and the TAN of Nile blend was (1.06 mg KOH/g),when the activated sample of the local clays were added to the high acid crude oil (Fula crude). It was found that the acidity of the crude oil was gradually decreased,for sample X ( X0,X 2,3,and X 3,3), the acidity of the crude oil was found to be ( 8.08,7.70 and 6.86 mg KOH/g ), for sample Y( Y0,Y 2,3,and Y 3,3) the acidity of the crude oil was found to be (8.01, 6.49 and 6.27 mg KOH/g) respectively, for sample Z( Z0,Z 2,3,and Z 3,3) the acidity of the crude oil was found to be (8.48, 7.37, and 7.18 mg KOH/g ) respectively. This shows that sample (Y3,3) has good ability to reduce the oil acidity by( TAN=6.27 mg KOH/g ) than sample (X3,3) ( TAN= 6.86 mg KOH/g ) and sample (X3,3) has good ability to reduce the oil acidity by( TAN=6.86 mg KOH/g ) than sample (Z3,3) ( TAN= 7.18 mg KOH/g ). So from this point of view it is useful to use sample (Y3,3) as reducing agent for high crude acidity. The acidity of Nile blend crude (1.06 mg KOH/g) was reduced to (1.05) when using sample (Y3,3).X- RD analysis shows that sample (X), is Muscovite, sample (Y),is also (Muscovite), and sample (Z) was found to be (Ziolite). The above results are in agreement with results of early studies carried out by the Author [11]. The following figures show the relationship between acid value and alkali concentrations:

3 16 Table (1) Sample(X): Fula crude, TAN=8.51mgKOH/g. Sample X0 X2,3 X3,3 Acid results Wt % of clay Figure (1).Acid results VS Alkali Concentration, Sample (X). Table (2) Sample(Y): Fula crude, TAN=8.51mgKOH/g. Sample Y0 Y2,3 Y3,3 Acid results Wt % of clay Figure (2). Acid results VS Alkali Concentration, Sample (X).

4 17 Table (3) Sample (Z): Fula crude, TAN=8.51mgKOH/g. Sample Z0 Z2,3 Z3,3 Acid results Wt% of clay Figure (3). Acid results VS Alkali Concentration, Sample (Z). Table (4) Sample (Y): Nile blend crude, TAN=1.06mgKOH/g. Sample Y0 Y2,3 Y3,3 Acid results Wt% of clay Figure (4).Acid results VS Alkali Concentration, Sample (Y).

5 18 IV. CONCLUSION From the above results, Muscovite clays have high ability to reduce the (TAN) of sour crude oil and to remove Naphthenic acids (NAs) than the Ziolite clay. The method of adsorption naphthenic acid by using local activated clays is proved to be efficient and effective process, but the problem of spent clay is yet to be investigated. Alkali activation of clay is recommended to aid further reduction in cost of activation as the cost of sodium hydroxide is much less than that of sulphuric acid which sells for about 150% the price of sodium hydroxide by weight. V. ACKNOWLEDGEMENTS The authors wish to thank the College of graduate studies and scientific research, of Karrary University, for their support and provision of funds. This research is made in partial fulfillment of the requirements for the degree of Ph.D. in Chemical Engineering at Karrary University. REFRENCES [1]. B. Region, in: API Proceedings, vol.11, Russia, 1930, P.102. [2].Annual Book of ASTM Standards. Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration (1999)p [3]. Lochte, H. L. and Littman, E. R., Petroleum Acids and Bases, Chemical Publishing Company, Inc., 1955, p [4]. Brient, J. A., Wessner, P. J. and Doyle, M. N., Naphthenic Acids, in Encyclopedia of Chemical Technology, Ki Othmer, Editor. 1995, John Wiley & Sons: New York. p [5]. Zhou Jianlong, Lixiaogang, Cheng Xueggun, et al. progress in research on mechanism and controlling of Naphthenic Acids Corrosion at high temperature [J].Chinese Corrosion and protection,2009,30(1):1-6. [7]. Zhang Qundan, Tiam Songbai, Hugan Shaokai, et.al Research in separation, Characterization and Corrosion of Naphthenic acid [J]. Chinese Corrosion and Petroleum in Petrochemical industry, 2010, 27(1). [8]. Wang Zhehua, et al.distribution of Carboxilicacids in Sudanese Dar Crude oil, [J]. China Petroleum and Petrochemical Technology,2011,Vol.13.No.4 pp [9]. Laredo, G.C., C.R. López, R.E. Álvarez, J.J. Castillo, and J.L. Cano, Identification of naphthenic acids and other corrosivity-related characteristics in crude oil and vacuum gas. [10]. Tomczyk, N.A., R.E. Winans, J.H. Shinn, and R.C. Robinson, on the nature and origin of acidic species in petroleum. 1. Detailed acidic type distribution in a California crude oil. Energy and Fuels, (6): p [11]. Osman, M.S, 2010, Production of Bleaching Earth From Local Clays, M.sc thesis, University of Gezira, Sudan.