OPTIMIZATION OF DEMULSIFIER FORMULATION …

1 Brazilian Journal of Chemical ISSN 0104-6632. Printed in Brazil Engineering Vol. 32, No. 01, pp. 107 - 118, January - March, 2015. OPTIMIZATION OF DEMULSIFIER . FORMULATION FOR SEPARATION OF WATER. FROM CRUDE OIL EMULSIONS. P. Hajivand and A. Vaziri*. Department of Chemical Engineering , Faculty of Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran. Phone: + 98 21 22014520 Fax: + 98 21 22014519, E-mail: (Submitted: June 9, 2013 ; Revised: October 26, 2013 ; Accepted: December 9, 2013). Abstract - In this study, various water-soluble and oil-soluble demulsifiers were selected for separation of water from crude oil emulsions and their productivity measured using the Bottle-test method at 70 C and 10. ppm concentration. The best ones among 23 demulsifiers examined through the screening process were fatty alcohol ethoxylate, triethanol amine and urea from the water-soluble group and Basororol E2032, Basorol PDB 9935 and TOMAC from the oil-soluble category.

2 Furthermore, the present study investigated the factors effective for demulsification such as temperature, concentration, pH, salinity and modifiers. It was found that the separation improves with increasing DEMULSIFIER concentration, increasing salt content, increasing temperature up to 80 C, keeping the pH values between 5-9. Adding solvent modifiers proved unnecessary. Two formulations were prepared based on suggested optimal concentrations of DEMULSIFIER content by experimental design using Qualitec 4 and these proved to be highly effective in treating real and synthetic emulsions. Keywords: Crude oil; DEMULSIFIER ; Water-in-oil emulsion; FORMULATION . INTRODUCTION emulsions (Sjoblom et al., 2005; Ramalho et al., 2010). Naturally occurring emulsifiers are concen- Water-in-oil emulsions are formed during pro- trated in the higher-boiling polar fraction of the duction of crude oil, which is often accompanied by crude oil (Jones et al.)

3 , 1978; Strassner, 1968;. water. Under the production conditions, a proportion Kimbler et al., 1966; Borba, 1990; Kokal and Al- of this water is usually intimately dispersed through- juraid, 1999; Svetgoff, 1989; Eley et al., 1998). out the crude oil as small droplets. In order to mini- These include asphaltenes, resins, and oil-soluble mize the production problems related to crude oil organic acids ( naphthenic, carboxylic) and bases, emulsions and environmental concerns, petroleum which are the main constituents of the interfacial operators need to prevent the formation of or break films surrounding the water droplets and that provide down these emulsions. The emulsification of water emulsion stability. in oil is normally difficult due to the immiscibility Asphaltenes are dark brown to black friable solids between these two liquid phases. However, shear with no definite melting point. They consist of con- mixing imposed on the fluids during production and densed aromatic sheets with alkyl and cyclic side the existence of natural surfactants in the petro- chains and heteroatoms (nitrogen, oxygen, sulfur).

4 Leum's composition contribute to formation of such and trace metals like vanadium and nickel scattered *To whom correspondence should be addressed 108 P. Hajivand and A. Vaziri throughout (Daaou et al., 2009). These molecules more stable at lower ionic strength of the aqueous can have 30 or more carbons, and they are usually phase. considered to be the heaviest and the most polar In the present study, the focus is on the investiga- components of the petroleum, but recent work shows tion of the effect of pH values, temperature, salinity that the average molecular weight of asphaltenes and alcohol modifiers on the stability of an Iranian extracted with n-heptane is about 750 g/mol crude oil emulsion. In addition, the influence of a (Groezin and Mullins, 2007) and surprisingly, lower wide range of chemical demulsifiers on destabiliza- values (around 400 g/mol) have also been found tion of the emulsion is studied in order to better un- (Honse et al.)

5 , 2012). They are characterized by a derstand the water-in-oil emulsion behavior. Qualitec relatively constant hydrogen/carbon ratio of 4, an experimental design software, was used to with a specific gravity near one; however, the nature achieve an optimized FORMULATION for water separa- of asphaltenes in crude oil is still a subject of debate. tion. These experiments were done by bottle test Asphaltenes are believed to exist in the oil as a col- method, which is the most common method for loidal suspension and to be stabilized by resins ad- evaluating the amount of water separated from wa- sorbed on their surface (Leontaritis and Mansoori, ter-in-oil emulsion (Mat, 2006). 1998). In this regard, the resins act as peptizing agents for asphaltenes and together form clusters called micelles. These micelles or colloids contain EXPERIMENTAL SECTION. most of the polar material found in the crude oil and possess surface-active properties (interfacial active Crude Oil Characterization material).

6 They in turn result from sulfur, nitrogen, oxygen, and metal-containing entities in asphaltene Crude oils used for these sets of experiments are molecules that form polar groups such as aldehydes, from two fields, Omidie and Ahwaz heavy crude oil. carbonyls, carboxylic acids, amines, and amides, and Their physical characteristics are shown in Table 1. play a key role in stabilizing emulsions. Resins are Chemical properties play important roles in the sta- complex high-molecular-weight compounds that are bility of crude oil emulsion. Table 1 shows that the not soluble in ethylacetate but soluble in n-heptane. oil from the Omidie field is more stable than the It appears that the asphaltene-resin ratio in crude oil latter as a result of combining four interfacial active is responsible for the type of film formed (solid or agents in the crude oil. mobile) and, therefore, is directly linked to the sta- bility of the emulsion (Strassener, 1968; Borba, Table 1: Chemical characteristics of crude oils.)

7 1990). There are numerous parameters that contribute to Crude oils Omidie Ahwaz the stability of the interfacial film and as a result to Chemical analysis emulsion stability, such as water pH and the additive Density (kg/m3 in 15 C) 884. content (Poteau et al., 2005; Fortuny et al., 2007; Salt content (g/m3) 16 14. Daaou et al., 2011), but these effects show different Asphaltene (%w/w) behavior for various oil origins (Strassner, 1968; Resin (%w/w) 20. Pathak and Kumar, 1995; McLean and Kilpatrick, Wax (%w/w) 15 1997a; Goldszal et al., 2002). For example, Daou et Solid part (%w/w) al. (2011) studied the effect of pH on Algerian crude Saturated Hydrocarbon (%w/w) 40 oil emulsions and suggested that a neutral medium is Aromatic Hydrocarbon (%w/w) more efficient than an acidic or basic environment for stabilizing the emulsions. Fortuny et al. (2007) Materials and Equipment studied the effects of salinity, temperature, water content and pH on the stability of crude oil emul- The chemicals and methods used in this study are sions based on microwave treatment and showed chosen based on suitability and economic feasibility.

8 That, in emulsions containing high water contents, the The demulsifiers used in this study are shown in rate of demulsification is high, except when high pH Table 2. The majority of the chemicals used in this and salt content were simultaneously involved. Ad- study were supplied from Merck, BASF and Kavosh ditionally, Moradi et al. (2011) studied the impact of Kimia Kerman companies. Table 3 presents the list salinity on crude oil/water emulsions by measuring of solvents used to increase the pour point and solu- the droplet-size distribution visualized by an optical bility of solid and viscous demulsifiers. The ho- microscopy method, and found that emulsions are mogenizer used in this study is Silent Crusher M. Brazilian Journal of Chemical Engineering OPTIMIZATION of DEMULSIFIER FORMULATION for Separation of Water from Crude Oil Emulsions 109. manufactured by Heidolph and the incubator is sion was prepared by mixing n-heptane (analytical Gerhardt, Model THO 500.)

9 Grade) and Toluene (7:3 V/V); 2 grams of asphalte- nes are added to a liter of the synthetic crude oil; the Table 2: Types of chemical demulsifiers. resultant solution is then mixed with water in a 4:1. No. Name Supplier (volumetric) ratio, resulting in a very stable W/O. 1 Urea Kavosh Kimia Kerman emulsion, as was expected (Bhattacharyya, 1992). 2 Polyethylene glycol Kavosh Kimia Kerman The phases were next mixed using a homogenizer at 3 Diethylene glycol Kavosh Kimia Kerman a speed of 15000 rpm for 6 minutes to get a stable 4 Propylene glycol Kavosh Kimia Kerman 5 Fatty alcohol ethoxylate Shazand Petrochemical emulsion. The experiments were repeated three times Company and the reported results are the mean value of each 6 Monoethylene glycol Kavosh Kimia Kerman result obtained. Relative errors in estimating the 7 Kavosh Kimia Kerman 8 Triethanolamine Kavosh Kimia Kerman volume of the separated water phase are around 3%.

10 9 2-Ethyl hexyl acrylate Merck for all procedures and steps. 10 Methacrylic acid Merck 11 Sodium dodecyl sulfate Sigma-Aldrich Extraction of Asphaltene ( ). 12 Butyl acrylate Merck 13 Acrylic acid anhydrous Merck Crude oil was dispersed in n-pentane or n-heptane 14 Methyl methacrylate Merck at a concentration of 1:5 (v/v). The mixture was then 15 Basorol PDB 9946 BASF company 16 Basorol PDB 9947 BASF company sonicated in an ultrasonic bath for 45 minutes and 17 Basorol PDB 9935 BASF company left to settle overnight. After settling, the mixture 18 Basorol PDB 9955 BASF company was sonicated again for 20 minutes. The precipitated 19 Basorol E 2032 BASF company 20 Basorol E 9350 BASF company asphaltenes were filtered on medium porosity 21 Naphthalene Fluka chemika (Hunktell grade 392) filter paper. The collected as- 22 Methyl trioctyl ammonium Merck phaltenes were mixed again with a 1:2 volume ratio chloride (TOMAC) of original crude to n-pentane or n-heptane, soni- 23 Dioctylamine Merck 24 VZB 1413 Kavosh Kimia Kerman cated for 45 minutes and left overnight.