Asphaltene stability - nonscanning NIR technique: World Congress on Emulsion 2010

Contribution to the 5th world congress on emulsion CME
12 - 14 October, Lyon, France

A comparative study of asphaltene precipitation/flocculation by a new non-scanning NIR-technique in accordance with ASTM D 7061

St. Küchler, T. Sobisch, A. Uhl, D. Lerche

LUM

Rudower Chaussee 29 (OWZ) 12489 Berlin / Germany

info@lum-gmbh.de, www.lum-gmbh.com

Abstract

Asphaltenes and its derivatives, which are present in crude oil emulsions , may create severe technical and economical problems when they precipitate. Especially the flocculation of asphaltenes in heavy fuel oils may cause severe problems, including reservoir plugging, fouling of production facilities, altering wettability and poisoning refinary catalysts. Therefore the prediction and prevention of asphaltene flocculation is a crucial task for technical and laboratory staff in R&D, QC and production.

From the various methods that have been suggested over the years to serve this task the ASTM D 7061-05a has become an industrial standard to quantify and predict asphaltene flocculation in crude oils and heavy fuels.

In this contribution a non-scanning NIR-technique will be applied to measure asphaltene stability according to ASTM D 7061-05a by space and time resolved extinction (transmission) profiles (STEP-Technology). This apparatus (LUMiReader®, LUM GmbH) has the capability to measure simultaneously in 3 channels at tontrolled temperature up to 60°C.

Nine different crude oils with and without inhibitor were studied.

For direct comparison the same samples have been analyzed by the scanning apparatus described in the ASTM D 7061-05a.

The Separability Numbers, calculated from the measurements with the non-scanning NIR-apparatus, range from 0.2 to 15 showing a very good reproducibility and a very good agreement with the scanning technique. The applied non-scanning NIR-apparatus therefore is able to serve the broad spectra of crude oils in the market.

Keywords: Crude oil, heavy fuel oil, Induced Phase Separation of Asphaltene, Separability Number, STEP-Technology

test for long term stability - bottom focused back scattering World Congress on Emulsion 2010

Contribution to the 5th world congress on emulsion CME
12 - 14 October, Lyon, France

Easing formulation of emulsions and test for long term stability using bottom focussed back scattering

T. Sobisch, U. Rietz, D. Lerche

LUM

Rudower Chaussee 29 (OWZ) 12489 Berlin / Germany

info@lum-gmbh.de, www.lum-gmbh.com

Abstract

Selection of efficient emulsifiers, their optimum concentration and of the processing conditions is a demanding and time consuming process. Evaluation of emulsion stability can be eased when focussing on the changes in droplet concentration right at the bottom part of the emulsion samples. Furthermore the level of the back scattering signal is directly related to the dispersion degree. Thus the initial back scattering signal can be used to compare emulsification quality and to detect loss in dispersity due to aging.

A new multisample approach using light backscattering signals is presented. It allows for fast measurement of stability and/or demixing phenomena and separation kinetics of up to 8 different samples simultaneously, by monitoring the concentration change in a very small region of interest at the bottom of the sample cell.

The method was applied to trace the optimum emulsifier concentrations for silicone oil emulsions to evaluate the influence of processing intensity. Further the method was used to detect the very first changes of sample dispersity after accelerated aging.

Results demonstrate that bottom focussed back scattering can be applied as tool in every day formulation work and that during accelerated aging tests the method can serve as a sensitive measure of loss of dispersion integrity.

Keywords: formulation, emulsifier selection, processing conditions, accelerated aging, bottom focussed back scattering

Inclined creaming, speeding-up stability evaluation - World Congress on Emulsion 2010

-->Contribution to the 5th world congress on emulsion CME
12 - 14 October, Lyon, France

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Speeding up the evaluation of emulsion stability during normal storage conditions

T. Sobisch, D. Lerche

LUM

Rudower Chaussee 29 (OWZ) 12489 Berlin / Germany

info@lum-gmbh.de, www.lum-gmbh.com

Abstract

The principle of inclined settling is often used in separation technology to increase capacity and efficiency of settling aggregates. The Boycott effect is also applied in clinical tests to speed-up the evaluation of blood samples.

To answer the question whether this approach can also be used to speed up the evaluation of emulsion stability tests were carried out with colloidal stable emulsions (stable against aggregation and coalescence) and flocculated emulsions.

The LUMiReader instrument (LUM, Germany) can measure space and time resolved extinction (transmission) profiles (STEP technology) in multiple channels using near infrared (NIR) or visible light. This way it measures changes in turbidity and the movement of the boundary towards the supernatant. Even more the angle of inclination can be varied between 0 and 30° from the vertical.

Investigations on creaming as function of angel of inclination were carried out on nonflocculated silicone oil-in-water emulsions varying the oil concentration and on flocculated silicone oil-in-water emulsions at different electrolyte concentration.

The same principle behaviour as in case of monodisperse colloidal stable silica was found for the polydisperse colloidal stable (nonflocculated) emulsion. In this case ‘inclined creaming’ proceeds. At 30° inclination the creaming can be accelerated by a factor of about 9, i.e. the necessary time for stability evaluation can be shortened accordingly.

The creaming rate dependence on inclination is rather unpredictable for flocculated network forming emulsions. A maximum in creaming rate was observed around 25° inclination. In case of the emulsion with 0.5 M NaCl this relates to an enhancement factor of over 25, however, for 0.75 M NaCl it is only slightly higher than 1.

Keywords: enhanced creaming, Boycott effect, emulsion stability, creaming velocity, salt induced flocculation

Rapid emulsifier selection, emulsion stability, reformulation - World Congress on Emulsion 2010

Contribution to the 5th world congress on emulsion CME
12 - 14 October, Lyon, France

Rapid emulsifier selection and evaluation of emulsion stability for reformulation

T. Sobisch, D. Lerche, LUM

Rudower Chaussee 29 (OWZ) 12489 Berlin / Germany

info@lum-gmbh.de, www.lum-gmbh.com

Abstract

Selection of emulsifiers and evaluation of emulsion stability is a frequent task. This relates to practical issues like formulation of emulsions, optimization of preparation conditions, quality control, shelf life estimation and breaking of emulsions. Due to European legislation (REACH) many companies are facing the problem to replace proven components in their formulations (low volume speciality compounds or problematic chemicals). This also applies to emulsifiers and emulsion based products.

A multisample technique based on analytical centrifugation is presented which allows for an accelerated study of creaming, sedimentation and of separation of oil and water phases. Not only information on the extent of phase separation is provided but also the kinetics are measured directly in-situ.

The method was applied to check for alternatives to nonyl phenol based surfactants as emulsifiers for silicone oil emulsions. Different commercial products were evaluated. It proved to be a very efficient screening method, which can be also applied in every day formulation work.

Due to the multisample approach one centrifugal run with 12 different samples was sufficient to identify more environmentally benign emulsifiers with identical or better performance. In a second run the efficiency of emulsifier combinations was tested. The primary destabilization mechanism for all emulsions was creaming, however, most emulsions showed phase inversion when a critical phase ratio was reached inside the cream layer. By increasing the polarity of the alternative emulsifiers the risk of phase inversion could be rigorously reduced.

Keywords: reformulation, REACH, emulsifier selection, silicon oil-in-water emulsions, creaming kinetics, analytical centrifugation

Surfactant adsorption kinetics - emulsion stability, World Congress on Emulsion 2010

Contribution to the 5th world congress on emulsion CME
12 - 14 October, Lyon, France

Interrelation between surfactant adsorption kinetics, interfacial rheology and emulsion stability

T. Sobisch1, N. Mucic2, J. Krägel2, A.V. Makievski3, R. Miller² and D. Lerche1

1 LUM GmbH, Rudower Chaussee 29 (OWZ) 12489 Berlin / Germany
info@lum-gmbh.de, www.lum-gmbh.com
² MPI für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, 14424 Potsdam / Germany
3 SINTERFACE Technologies, Volmerstrasse 5, 12489 Berlin / Germany


Abstract
The right choice of emulsifier is an ongoing challenge in emulsion technology. The time scale of the emulsification process has a strong impact on the emulsifier efficiency, which can only become effective if the adsorption kinetics are fast enough to avoid coalescence of freshly formed droplets. Additionally, the interfacial rheology at the oil-water interface determines the final emulsion stability.
The interrelation between surfactant adsorption kinetics, interfacial rheology and emulsion stability was investigated in model systems paraffin oil / water / nonionic surfactants, where the EO-chain length was varied.
The kinetics and thermodynamic properties of the surfactants at the oil/water interface were measured by using drop profile analysis tensiometry. The same tool is applied for the investigation of the interfacial dilational rheology by recording the interfacial tension response to harmonic area compressions-expansions of the studied drop.
Emulsions were prepared with a dissolver type homogenizer. Stability of emulsions was investigated as function of time of processing, surfactant concentration and HLB value using multisample analytical centrifugation. Not only the extent of phase separation but also the kinetics are directly measured in-situ.
Emulsion stability increases with time of emulsification. The emulsifier with 5 EO units is far more effective than that with 12 EO units. Adsorption equilibrium at the interface is reached in seconds. The kinetics of adsorption show clearly a depletion effect of surfactant molecules from the aqueous phase, which is especially pronounced for the emulsifier with 5 EO units. Nevertheless, at higher surfactant concentration the interfacial tension is lower for the more lipophilic surfactant.


Keywords: emulsion stability, adsorption layer properties, analytical centrifugation, emulsion preparation, emulsifier selection, oil-in-water