Effective Demulsifier Research Articles

Wettability Control Mechanism of Highly Contaminated Hydrophilic Silica/Alumina Surfaces by Ethyl Cellulose

In a previous study (Feng et al. Langmuir2010, 26, 3050), a biodegradable ethyl cellulose (EC) was proven to be an effective demulsifier for water-in-diluted bitumen emulsions by flocculation-enhanced coalescence through the displacement of protective interfacial films. In the current study, the potential of EC in displacing the asphaltene or bitumen layers adsorbed on hydrophilic silica and alumina surfaces is investigated in an attempt to explore the applicability of EC as a chemical modifier to control the wettability of solids contaminated by heavy oils. The quartz crystal microbalance with dissipation (QCM-D) was used to determine the adsorption of EC on silica or alumina which has a thin layer of asphaltene contaminant (preadsorbed). For comparison, the adsorption of asphaltenes on silica or alumina which was preadsorbed with EC was also determined. The effect of EC on the wettability and morphology of the asphaltene- or bitumen-contaminated (coated) silica or alumina surfaces was determined by contact angle measurement and atomic force microscope (AFM) imaging. The measurements were conducted before and after soaking the asphaltene- or bitumen-coated silica and alumina wafers in EC-in-toluene solution. The results of QCM-D showed irreversible adsorption of asphaltenes on silica surface. However, EC was found to adsorb on and/or displace the irreversibly preadsorbed asphaltenes from silica and alumina surfaces. Atomic force microscope imaging confirmed a gradual displacement of the preadsorbed asphaltenes or bitumen by EC from silica wafer surfaces, in which the asphaltene/bitumen contaminants were forced into sporadic larger aggregates. After 7 h of contact with EC-in-toluene solutions, the majority of the silica substrate surfaces precontaminated by asphaltenes or bitumen were covered with EC. Correspondingly, the contact angle of water decreased from about 88° and 67° of the original asphaltene- and bitumen-coated surfaces, respectively, to final values in the range of 20–30° which are similar to that of the EC-coated surface. Effect of EC adsorption on increasing the wettability of chemically hydrophobized (silanized) silica surface with water contact angle from 80° to 100°, is more conservative, leading to an intermediate water contact angle of 60–70° due to its weak binding and different conformations of EC on hydrophobic surfaces from that on hydrophilic surfaces. These findings demonstrated the possibility of using EC to modify the wettability of hydrocarbon-contaminated inorganic solids (clays) to improve heavy oil processing.

Emulsion formation and stability during reversed micelle extraction

The formation of emulsions in the reversed micelle extraction of proteins from filtered broth is a major problem which can significantly increase the cost of downstream separation. In this work the effect of some aqueous phase constituents such as buffer salts, other added cations, phospholipids and five molecular-weight fractions (fractionated using ultrafiltration membranes) of a fermentation broth of Bacillus stearothermophilus on emulsion formation and stability of a water-AOT-isooctane reversed micelle extraction system were examined. The parameters used for the determination of emulsion stability were the settling time and interfacial tension, and this varied from 33 mN/m for pure water-isooctane to around 1 mN/m for high AOT concentrations (>100 mmol/dm 3 ). K + ions of the buffer solution, as well as K + ions and Na + ions from added salts had a destabilising effect on a water-AOT-isooctane emulsion. This effect was found to be greatest for the K + ions, possibly due to their smaller hydrated radius compared with the other ions, and reduced the phase separation time with 50 mmol/dm 3 AOT from 500 min to less than 5 min. The phospholipids phosphatidylcholine and phosphatidylinositol were also found to be effective demulsifiers, with phosphatidylcholine having a slightly greater effect. Albumin and β-galactosidase both exhibited a strong emulsifying effect on a surfactant-free water-isooctane system, but were capable of strongly reducing emulsification in the presence of AOT. High molecular weight fractions (>30 kDa) of the B stearothermophilus fermentation broth had a much stronger tendency to form emulsions than MW fractions <30 kDa, while the 30-50 kDa MW fraction had the best demulsifying effect, reducing the separation time to 75 min. Demulsifying properties of the components tested were attributed to the competition of these compounds with AOT for control of the aqueous-organic interface leading to a less stable mixed interfacial layer.

Distribution of Demulsifiers between Crude Oil and Water phases

Using a radiosoptopic tracer to measure the concentration of demulsifiers,we studied the distribution regularity of demulsifiers between crude oil and water phases under different temperatures and found that the dewatering rate is related to the partition coefficient of demulsifier, which is quite sensitive to the variation of temperature According to the experimental results, we hold that an effective demulsifier should possess a relatively high partition coefTicient.

Molecular dynamics simulation of isopropyl naphthalene sulfonate at the water/heptane interface

Stable water-in-crude oil (w/o) emulsions occur at many stages during the production and processing of crude oil. The breaking of these emulsions is an essential step, frequently carried out by the addition of chemical demulsifiers. The stability of any surfactant-stabilized emulsion is strongly dependent on the nature of the interfacial film, which provides a resistance to either flocculation or coalescence, towards the final equilibrium state of phase separation. Thus, effective demulsifiers must be capable of displacing preformed, rigid, incompressible interfacial films, and/or significantly reducing the rate of build-up of the surfactant layer. This work presents the results of molecular dynamics simulations of a flat section for a w/o interface covered by a nonionic surfactant, either pure or contaminated by an anionic demulsifier. The simulation of aqueous and oleic solutions of surfactant and demulsifier were also performed by using 3D amorphous cells with 3D periodicity, while the interface was modeled by a 3D layered cell establishing 2D periodic boundary conditions. This made it possible to demonstrate changes in the amphiphile bimolecular interactions and diffusion properties at the w/o interface once the demulsifier is adsorbed, which could be related to the loss of stability of the surfactant film.

STUDY OF DEMULSIFICATION OF WATER-IN-CRUDE OIL EMULSION

ABSTRACT Demulsification of water-in-crude oil emulsion was studied at two different salinities, 0.5% and 10% sodium chloride, using five different nonionic surfactants. Equilibrium crude oil-water interfacial tension was measured with drop volume method. Low molecular weight surfactants were found to be completely ineffective as demulsifiers. Three surfactants which were effective demulsifiers, exhibited good interfacial activity, surface adsorption and surface pressure. The performance of the demulsifiers changed with change in salinity of aqueous phase. Surfactants effective as demulsifiers reduced surface tension of water by more than 25 dynes-cm-1. For a given crude oil-water system, the surfactant which developed surface pressure in excess of 15 dynes-cm-1 was found to be good demulsifier for that system. Based upon these studies, a physical model of demulsification has been proposed

Measurement of dielectric constant of oilfield emulsions and its application to emulsion resolution

The trial-and-error method of choosing an optimum demulsifier out of a wide variety of demulsifiers to effectively treat a given oilfield water-in-oil emulsion is time-consuming. To minimize this, the use of the dielectric constant as a criterion for screening, ranking and selection of demulsifiers for emulsion resolution was investigated. Dielectric constants of emulsions and demulsifiers were measured using a portable capacitance meter (Harris Model), while bottle tests were conducted according to API specification. The results show that the dielectric constants can be used effectively to screen and rank demulsifiers while a confirmatory bottle test is conducted on the best demulsifiers to assist in the rapid selection of the most effective demulsifiers. This procedure will save time and cost in the petroleum industry. On the basis of this study, a stage-by-stage screening procedure is presented.

Emulsion stability and demulsification during the direct extraction of penicillin broth

In this article, we present the factors which influence the stability of the emulsion forming under the circumstances of the direct extraction of penicillin fermentation broth and the conditions of demulsification. A laboratory method has been developed for testing demulsifiers and a quantitative evaluation of the properties determining the separation of phases has been worked out as well. It has been found that an emulsion of oil in water (o/w) forms and that this is very stable; it can be broken only by the presence of demulsifier and by using a field of centrifugal force. We have discovered that the most effective demulsifiers are cation-active surfactants for 1-4 g/L broth concentration. Furthermore, it is advantageous if the demulsifier contains a nonionic surfactant and wetting agent as well. From the 19 surface-active compounds studied in the laboratory, we found that the NADAR 107 A and ARMOGARD D-5306 demulsifiers contained the best properties for the extraction of the penicillin broth.

The formulation of an effective demulsifier for oil spill emulsions

The formation of stable sea water-in-crude oil emulsions after an oil spill was first reported after the Torrey Canyon wreck in 1967. The problem of handling this stable water (65%)-in-oil (35%) emulsion rather than oil is evidenced in the additional expensive on-site storage requirement as well as the handling difficulty with the viscous semi-solid emulsion. This paper details the results of an R&D program that has established the mechanism for the formation of this emulsion. This insight enabled a specific effective chemical demulsifier to be formulated. A treatment technique was devised that entails injecting the demulsifier into the oil spill emulsion as it is skimmed from the water surface. The emulsion is then rapidly separated into water-free oil and a clean-water phase that can be decanted back into the sea. Full-scale tests were successfully conducted by JBF Scientific Corp. using two types of commercial JBF DIP skimmers in a small concrete lined pond.

Cation-active demulsifiers based on fatty acids

1. Monoesters of triethanolamine and caproic, pelargonic, myristic, and palmitic acids have been synthesized and their physicochemical characteristics have been determined; these compounds have not been described previously in the literature. 2. New, highly effective cation-active demulsifiers have been synthesized for the first time and have been studied. 3. It has been found that the maximum demulsifying capability is that of the quaternary ammonium salts obtained from C8-C11 fatty acids.

Method for selecting a demulsifier

1. Demulsifiers for treating oil in a field of power-frequency currents may be selected by comparing the optimum desalting and dehydrating capacities of a number of demulsifiers by the thermochemical method. 2. The most effective nonionogenic demulsifiers for preparing Kotur-Tepe oil are as follows: alkylphenols, containing 10–14 ethylene oxide groups in the molecule (OP-10, KAUFE-14), hydroxyethylated monoalkylphenols of the DFOE type, containing 17.5–22 ethylene oxide groups in the molecule, OZhK, and OPS; the most effective ionogenic demulsifiers are katapin A and katapin K.