Characterization of O/W Pickering emulsion by NMR (original) (raw)
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Methods for Droplet Size Distribution Determination of Water-in- oil Emulsions using Low-Field NMR
A method using Pulsed Field Gradient Nuclear Magnetic Resonance PFG-NMR for water-incrude oil emulsion droplet size determination has been optimized and compared with optical microscope for validation. The method applies a combination of Pulsed-Field Gradient (PFG) NMR, Stimulated Echo (STE), and Carr-Purcell-Meimboom-Gill (CPMG) sequences for measuring diffusion, resolving oil and water signal and for measuring the attenuation due to a distribution in T 2 values. This returns the droplet size distributions of water-in-oil emulsions within a minute. No prior assumption is made on the shape of the droplet size distribution, which enables the method to resolve for instance bimodal distributions. To validate this method, three different crude oils were used in the experiment. The emulsions prepared had water cuts from 10 to 40 %. The correlation between PFG-NMR and optical microscopy was good for the emulsions. Any potential discrepancies between the two techniques are discussed, so are the limitations and advantages of the methods.
NMR Self-Diffusion Studies of the Water and the Oil Components in a W/O/W Emulsion
Journal of Colloid and Interface Science, 1997
With regard to fundamental aspects of multiple emulsions, The application of the pulsed field gradient NMR technique to a relatively little is known. The aim of the work presented double emulsion is presented. This method determines the diffusion here is to apply pulsed field gradient (PFG) NMR techniques behavior of the different components of the emulsion. The details of (14-16) to a W/O/W emulsion. With this approach one the system studied, which is of the W/O/W type, have been taken from measures the mean displacements of the constituents of the the literature. Information obtained pertains to the size distribution of emulsion, the values of which convey information with rethe water droplets in both the starting emulsion and the double emulgard to the structure and dynamics of the emulsions. Thus sion. In addition, the different phenomena that govern the oil diffusion one may use the technique to study structural aspects of in both systems have been identified and discussed. ᭧ 1997 Academic Press emulsions such as the droplet size distribution (17) as well
Droplet Size Distribution in Water-Crude Oil Emulsions by Low-Field NMR
Journal of the Brazilian Chemical Society
This paper reports the droplet size distribution (DSD) measurements in 28 W/O (water/oil) crude oil emulsions prepared with two Brazilian oils (medium and heavy) under different shear conditions using both 10 g L-1 NaCl solution and water production by low field nuclear magnetic resonance (NMR, 2.2 MHz). The PFGSTE (pulsed-field gradient-stimulated echo) pulse sequence applied was able to separate the crude oil emulsion signal for both medium and heavy oil even for low dispersed phase content (1.51 wt.%) and took into account only the aqueous phase signal. All emulsions exhibited an average diameter smaller than 5.5 μm because of the severe shear conditions. Despite the difficult processing of the S24 (6.48 wt.%) emulsion signal, good agreement was achieved between low field NMR and low-angle laser light scattering (LALLS) results. Finally, the paramagnetic ions in the water production did not affect the NMR measurements, demonstrating its applicability for analyzing real emulsions.
Characterization of emulsions by NMR methods
Journal of Colloid and Interface Science, 1991
Pulsed-gradient spin-echo NMR experiments are performed on emulsions stabilized by nonionic, cationic, and anionic surfactants. The mean displacements during the measuring time of the liquid inside the emulsion droplets are of the same order of magnitude or larger than the diameter of the droplet, and as a consequence the molecules undergo restricted diffusion. Murday and Cotts' equation for restricted diffusion inside spherical cavities can be fitted to the experimental data using the bulk diffusion coefficient value for the liquid. The continuous medium gives normal diffusion coefficients, slightly reduced due to obstruction effects of the emulsion droplets. For some cases the stimulated spin-echo technique must be used to evaluate the diffusion coefficients as short T2's make it difficult to perform experiments with the ordinary PGSE sequence, The approach can be used in dilute and nondilute systems to infer information about the droplet size and size distribution and whether a particular emulsion is of the O/W or the W/O type.
The measurement of droplet size distribution of water-oil emulsion through NMR method
2016
The effects of water/oil volume ratio, type and concentration of demulsifier, water salinity and mixing speed on the average water droplets size in water-oil emulsion are evaluated at different times through NMR measurements.The type and concentration of demulsifier have the greatest effects on the average droplet size with 38% and 31.5%, respectively. The water/oil volume ratio, water salinity and mixing speed are significant factors with 13.1%, 7.5% and 5.71%, respectively. The commercial demulsifier Break 6754 has the greater influenceon the average droplet size compared to the acrylic acid. The water droplets size increases upon increasing the concentration of demulsifier, the water volume ratio and the salinity of water and decreases upon increasing the mixing speed.
Journal of Colloid and Interface Science, 2007
This paper describes a proton nuclear magnetic resonance (NMR) technique, pulsed field gradient with diffusion editing (PFG-DE), to quantify drop size distributions of brine/crude oil emulsions. The drop size distributions obtained from this technique were compared to results from the traditional pulsed field gradient (PFG) technique. The PFG-DE technique provides both transverse relaxation (T 2 ) and drop size distributions simultaneously. In addition, the PFG-DE technique does not assume a form of the drop size distribution. An algorithm for the selection of the optimal parameters to use in a PFG-DE measurement is described in this paper. The PFG-DE technique is shown to have the ability to resolve drop size distributions when the T 2 distribution of the emulsified brine overlaps either the crude oil or the bulk brine T 2 distribution. Finally, the PFG-DE technique is shown to have the ability to resolve a bimodal drop size distribution. Published by Elsevier Inc.
Emulsion Stability Studied by Nuclear Magnetic Resonance (NMR)
Energy & Fuels, 2010
A method using low-field nuclear magnetic resonance (NMR) for measurement of water-in-crude oil emulsion stability has been optimized and compared to light transmission measurements. Two NMR sequences have been used; one of them applies a diffusion T 2-weighted profile measurement sequence, which can return a water profile of an emulsion within 30 s. The stability of the emulsions was compared by studying emulsions in parallel in Turbiscan and NMR. Three different crude oils were used in the experiment. The emulsions prepared had water cut at 50%. The correlation between NMR and Turbiscan regarding the free water formation was good for the emulsions. The potential limitations and advantages of the technique are discussed.
Advances in Colloid and Interface Science, 2003
The procedure proposed by Packer and Rees (J. Colloid Interface Sci. 40 (1972) 206) to interpret pulsed field gradient spin-echo (PGSE) experiments on emulsions is commonly used to resolve for the distribution of droplet sizes via nuclear magnetic resonance (NMR). Nevertheless, such procedure is based on several assumptions that may restrict its applicability in many practical cases. Among such constrains, (a) the amplitude of the spin-echo (signal) must be influenced solely by the drop phase, and not by the continuous phase; and (b) the shape of the drop size distribution must be assumed a priori. This article discusses new theory to interpret results from PGSE experiments and a novel procedure that couples diffusion measurements (PGSE) with transverse relaxation rate experiments (the so-called CPMG sequence) to overcome the above limitations. Results from experiments on emulsions of water dispersed in several crude oils are reported to demonstrate that the combined CPMG-PGSE method renders drop size distributions with arbitrary shape, the wateryoil ratio of the emulsion and the rate of decay of magnetization at the interfaces, i.e. the surface relaxivity. It is also shown that the procedure allows screening if the dispersion is oil-inwater (oyw) or water-in-oil (wyo) in a straightforward manner and that it is suitable to evaluate stability of emulsions. ᮊ
Langmuir, 2010
Self-diffusion NMR is used to investigate monodispersed oil in water emulsions and the subsequent gel formed by removing the water through evaporation. The radius of the oil droplets in the emulsions is measured using a number of diffusion methods based on the measurement of the mean squared displacement of the oil, water, and tracer molecules. The results are consistent with the known size of the emulsions. Bragg-like reflections due to the restricted diffusion of the water around the oil droplets are observed due to the low polydispersity of the emulsions and the dense packing. The resulting data are fitted to a pore glass model to give the diameter of both the pools of interstitial water and the oil droplets. In the gel, information on the residual three-dimensional structure is obtained using the short time behavior of the effective diffusion coefficient to give the surface to volume ratio of the residual protein network structure. The values for the surface to volume ratio are found to be consistent with the expected increase of the surface area of monodisperse droplets forming a gel network. At long diffusion observation times, the permeability of the network structure is investigated by diffusion NMR to give a complete picture of the colloidal system considered.
Industrial & Engineering Chemistry Research, 2019
Emulsified water droplets must be extracted from crude oil for economical and transport purposes, which is achievable by chemical demulsification. Four different chemicals were tested on water-incrude oil emulsions using a newly developed NMR method. Droplet size distributions were mapped at the beginning and end of experimentation. In addition, slice selections (soft RF pulses) were used to isolate the signal from residual droplets within the separated oil phase to study coalescence patterns in the emulsion bulk. The NMR could also return rapid continuous brine profiles for analysis of sedimentation rates and free water appearance kinetics. The residual water content was isolated by strong bi-polar gradient suppression, thereby allowing focus on the smaller droplets still emulsified in the top region in the brine profiles. Optimum concentrations were found for each chemical, and blends of several chemical demulsifiers were noticeably more efficient than the single component demulsifiers in this study.