@article{sullivan_zaki_sjoblom_kilpatrick_2007, title={The stability of water-in-crude and model oil emulsions}, volume={85}, number={6}, journal={Canadian Journal of Chemical Engineering}, author={Sullivan, A. P. and Zaki, N. N. and Sjoblom, J. and Kilpatrick, P. K.}, year={2007}, pages={793–807} }
 @article{zaki_carbonell_kilpatrick_2003, title={A novel process for demulsification of water-in-crude oil emulsions by dense carbon dioxide}, volume={42}, ISSN={["0888-5885"]}, DOI={10.1021/ie0303597}, abstractNote={CO2 was used to break several water-in-crude oil and water-in-model oil emulsions stabilized by asphaltenic films. The stability of asphaltenic films in model oils having varying H/C ratios (aromaticities) was also studied upon contact with liquid or supercritical CO2. The efficacy and kinetics of demulsification appeared to be enhanced with increased CO2 density and mole fraction. The proposed mechanism by which CO2 destabilizes water-in-crude oil emulsions involves asphaltene flocculation and precipitation. The emulsions break by flocculating the adsorbed asphaltenes, leading to film defects, film thinning, film rupture, and water coalescence. The various factors influencing asphaltene precipitation and emulsion destabilization were studied in model solvent systems containing asphaltenes and resins. Increasing CO2 pressure, residence time, temperature, and degree of mixing were found to increase the rate of asphaltene precipitation. Asphaltene precipitation by CO2 was found to increase in the presence o...}, number={25}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Zaki, NN and Carbonell, RG and Kilpatrick, PK}, year={2003}, month={Dec}, pages={6661–6672} }
 @misc{zaki_kilpatrick_carbonell_2003, title={Methods of demulsifying emulsions using carbon dioxide}, volume={6,566,410}, number={2003 May 20}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Zaki, N. N. and Kilpatrick, P. K. and Carbonell, R. G.}, year={2003}, month={May} }
 @article{poindexter_zaki_kilpatrick_marsh_emmons_2002, title={Factors contributing to petroleum foaming. 1. Crude oil systems}, volume={16}, ISSN={["1520-5029"]}, DOI={10.1021/ef010224i}, abstractNote={Gas/oil separation can often be accompanied by unwanted foaming. To study this phenomenon, 20 crude oils were subjected to low-pressure foaming experiments. Eleven of the crudes were from offshore platforms where foaming occurs regularly. Two foaming parameters, foam volume (or foamability) and collapse slope (i.e. the rate of foam collapse in the absence of sparge gas), were compared with several crude oil properties, namely, density, bulk viscosity, surface tension, asphaltene and resin content, asphaltene and resin molecular weight, and asphaltene and resin heteroatom content. For asphaltenic crudes, collapse slope was found to correlate with asphaltene content as well as several other crude oil properties:  density, viscosity, and surface tension. Foam volume did not relate to any asphaltenic crude oil property. However, for crudes having little to no asphaltenes, foam volume, not collapse slope, strongly related to crude oil surface tension. For low asphaltenic crudes, results further indicate that r...}, number={3}, journal={ENERGY & FUELS}, author={Poindexter, MK and Zaki, NN and Kilpatrick, PK and Marsh, SC and Emmons, DH}, year={2002}, pages={700–710} }
 @article{zaki_poindexter_kilpatrick_2002, title={Factors contributing to petroleum foaming. 2. Synthetic crude oil systems}, volume={16}, ISSN={["0887-0624"]}, DOI={10.1021/ef010225a}, abstractNote={The influence of petroleum asphaltenes and resins on stabilizing model oil foams comprised of light mineral oil mixed with toluene (minerol) was investigated. Two factors contribute significantly to foam volume and stability:  bulk viscosity and asphaltene state of aggregation. An increase in bulk viscosity was found to increase foam stability as gauged by the total time required for a foam to collapse. Asphaltene aggregation is governed primarily by the solvent aromaticity and resin/asphaltene (R/A) ratio. There is a threshold size in the state of asphaltene aggregation above which the ability of these aggregates to stabilize foams is markedly reduced. This appears to be closely related to asphaltene flocculation and precipitation at compositions beyond the solubility limit of the asphaltenes. Solvent systems generating the highest foam volume were found to reduce the air-oil surface tension to the greatest extent. Addition of an asphaltene dispersant increased the foamability of asphaltenes in minerol a...}, number={3}, journal={ENERGY & FUELS}, author={Zaki, NN and Poindexter, MK and Kilpatrick, PK}, year={2002}, pages={711–717} }
 @article{zaki_butz_kessel_2001, title={Rheology, particle size distribution, and asphaltene deposition of viscous asphaltic crude oil-in-water emulsions for pipeline transportation}, volume={19}, ISSN={["1532-2459"]}, DOI={10.1081/LFT-100000774}, abstractNote={The rheology of an asphaltic heavy crude oil-in-water emulsions stabilized by an anionic (RN) and a nonionic (TEP) surfactants individually or in a mixture has been studied. The investigated crude oil has a non-Newtonian, time dependent, shear thickening, rheopectic behavior with a relatively high yield stress. The relatively high yield stress of this crude oil is attributed to the presence of a relatively high asphaltene and resins content. The viscosity ofhe crude oil decreases when it is emulsified with synthetic formation water in the form of an oil-in-water type of emulsion using a nonionic or an anionic surfactant. It has been found that, the maximum oil content required for forming an oil-in-water emulsion of acceptable viscosity is the 60% oil-containing emulsion. However, the 70% oil-containing emulsion is not an oil-in-water type of emulsion but it is rather a complicated mixture of oil-in-water-in-oil type of emulsion. The presence of the anionic and the nonionic surfactants together has a synergistic effect in decreasing the total surfactant concentration required to stabilize the emulsion and to form low viscosity emulsion. It has been emphasized that the nonionic surfactant has a positive contribution in forming emulsions with low viscosity. Meanwhile, the anionic surfactant contributes in stabilizing the emulsion at lower concentrations. Flocculation point measurements showed that the added surfactants caused no sign of asphaltene deposition. This implies that it is safe to use the investigated surfactants in forming oil-in-water emulsion for viscous asphaltic crude oils without any fear of asphaltene deposition.}, number={3-4}, journal={PETROLEUM SCIENCE AND TECHNOLOGY}, author={Zaki, N and Butz, T and Kessel, D}, year={2001}, pages={425–435} }
 @article{zaki_schorling_rahimian_2000, title={Effect of asphaltene and resins on the stability of water-in-waxy oil emulsions}, volume={18}, ISSN={["1091-6466"]}, DOI={10.1080/10916460008949884}, abstractNote={ABSTRACT Asphaltene, resins and paraffin waxes, their mutual interactions and their influence on the stability of water-in-oil emulsions have been studied. 20 wt % paraffin wax dissolved in decalin was used to model the waxy crude oil. Asphaltene and resins separated from a crude oil were used to stabilize the water-in-oil emulsions. Synthetic formation water was utilized as the aqueous phase of the emulsion. The emulsion stability increased with increasing the concentration of asphaltene with a subsequent decrease in the average particle size distribution of the emulsion. Resins alone are not capable of stabilizing the emulsion, however, in the presence of asphaltene they form very stable emulsions. Dynamic viscosity and pour point measurements provided evidence for resins-paraffin waxes interactions. Asphaltene in the form of solid aggregates form suitable nuclei for the wax crystallites to build over with a mechanism similar to that of paraffin wax crystal-modifiers. As asphaltene are polar in nature they are derived at the oil/water interface which was proved by the ability of asphaltene to reduce oil/water interfacial tension. Consequently, nucleation of the wax crystallites by asphaltene and resins at the interface will add to the thickness of the oil-water interfacial film and hence increase the stability of the emulsion.}, number={7-8}, journal={PETROLEUM SCIENCE AND TECHNOLOGY}, author={Zaki, N and Schorling, PC and Rahimian, I}, year={2000}, pages={945–963} }
 @article{zaki_maysour_abdel-azim_2000, title={Polyoxyalkylenated amines for breaking of water-in-oil emulsions stabilized by asphaltenes and clay}, volume={18}, ISSN={["1091-6466"]}, DOI={10.1080/10916460008949888}, abstractNote={ABSTRACT The main objective of this paper is lo emphasize the efficiency of synthesized polyo.xyalkylenated amines (PPPEA) having different hydiophilic-lipophilic balance (HLB) values in breaking synthetic water-iu-benzene emulsions stabilized by both pelroleum asphaltenes and clay (EAC). It was found that the presence of clay and asphaltenes in a certain ratio (1:1 summing 0 5 wt / vol. % with respect to the total emulsion volume ) offers maximum emulsion stability. This was attributed to the effect of asphaltenes in converting water-wet particles (such as clay) into oil-wet panicles, which then act as emulsifying agents for waler-in-oil emulsions. This explains the synergistic effect resulting from the mutual interactions between asphaltenes and clay in stabilizing Eac. It was found that the most efficient demulsifiers for breaking Eac are the aromatic PPPEA having low HLB. This is attributed to the capability of the aromatic PPPEA demulsifiers lo form well developed interactions with the aromatic asphaltenes. This enhanced interaction will drag the asphaltenes and clay from the interlace increasing the demulsification efficiency.}, number={9-10}, journal={PETROLEUM SCIENCE AND TECHNOLOGY}, author={Zaki, NN and Maysour, NES and Abdel-Azim, AAA}, year={2000}, pages={1009–1025} }
 @article{zaki_ahmed_nassar_2000, title={Sodium lignin sulfonate to stabilize heavy crude oil-in-water emulsions for pipeline transportation}, volume={18}, ISSN={["1532-2459"]}, DOI={10.1080/10916460008949898}, abstractNote={ABSTRACT The efficiency of sodium lignin sulfonate (SLS) as an anionic surfactant derived from waste wood pulping industry in stabilizing an Egyptian heavy crude oil (Geisum)-in-water emulsions for pipeline transportation has been investigated. The stability and rheology of the emulsions stabilized by SLS or with a nonionic surfactant nonyl phenol diethylenetriamine formaldehyde ethoxylate (NDFE) individually or in a mixture have been studied. It has been found that the dynamic shear viscosity of the crude oil decreases substantially when it is emulsified with water in the form of an oil-in-water type of emulsion. The stability of the oil-in-water emulsion increases as the surfactant concentration increases. Potable water and saline water containing different molar concentrations of NaCI have been used to study the effect of aqueous phase salinity on the stability and viscosity of the emulsion. Surfactant dissolved in saline water has been utilized to find out the possibility of injecting the surfactant into a well bore to effect emulsification in the pump or tubing for enhancing the production of heavy crude oils as oil-in-water emulsion. The study revealed that, the viscosity of the emulsion containing potable water is always less than that containing saline water and the viscosity increases as the salt content increased.}, number={9-10}, journal={PETROLEUM SCIENCE AND TECHNOLOGY}, author={Zaki, NN and Ahmed, NS and Nassar, AM}, year={2000}, pages={1175–1193} }
 @article{ahmed_nassar_zaki_gharieb_1999, title={Stability and rheology of heavy crude oil-in-water emulsion stabilized by an anionic-nonionic surfactant mixture}, volume={17}, ISSN={["1091-6466"]}, DOI={10.1080/10916469908949734}, abstractNote={ABSTRACT The stability and rheology of an Egyptian Heavy crude oil-in-water emulsions stabilized by an anionic (TDS) and a nonionic (NPE) surfactants individually or in a mixture have been studied. The study reveals that, the viscosity of the crude oil decreases when it is emulsified with water in the form of an oil-in-water type of emulsion. The stability of the oil-in-water emulsion increases as the surfactant concentration and speed of mixing of the emulsion increases. Fresh water and synthetic formation water have been used to study the effect of aqueous phase salinity on the stability and viscosity of the emulsion. Surfactant dissolved in synthetic formation water has been utilized to find out the possibility of injecting the surfactant into a well bore to effect emulsification in the pump or tubing for enhancing the production of heavy crude oils as oil-in-water emulsion. The study revealed that, the viscosity of the emulsion containing fresh water is always less than that containing formation water...}, number={5-6}, journal={PETROLEUM SCIENCE AND TECHNOLOGY}, author={Ahmed, NS and Nassar, AM and Zaki, NN and Gharieb, KH}, year={1999}, pages={553–576} }
 @article{abdel-azim_zaki_maysour_1998, title={Polyoxyalkylenated amines for breaking water-in-oil emulsions: Effect of structural variations on the demulsification efficiency}, volume={9}, ISSN={["1042-7147"]}, DOI={10.1002/(SICI)1099-1581(199802)9:2<159::AID-PAT757>3.0.CO;2-K}, abstractNote={In the present work, different aliphatic and aromatic amines were ethoxylated after a previous propoxylation (PPPEA) with different degrees of propoxylation and ethoxylation in order to obtain polymeric surfactants having different hydrophilic–lipophilic balance (HLB) values. The influence of the structural variations in the prepared PPPEA on their efficiency as demulsifiers for water-in-oil emulsions was investigated. Synthetic water-in-benzene emulsions stabilized by petroleum asphaltenes was utilized for the completion of this study. The actual propylene oxide (PO)–ethylene oxide (EO) ratios of the PPPEA under investigation was elucidated via 1H NMR spectroscopy. It was found that each demulsifier practices a maximum demulsification efficiency at an optimum concentration. At this concentration, the demulsifiers’ molecules were believed to form a monolayer by adsorbance at the benzene–water interface. The influences of the number of aromatic rings in the molecule, the degree of substitution in the aromatic rings, the number of amine groups, the number of PO–EO chains and HLB on the demulsification efficiency were accomplished. © 1998 John Wiley & Sons, Ltd.}, number={2}, journal={POLYMERS FOR ADVANCED TECHNOLOGIES}, author={Abdel-Azim, AAA and Zaki, NN and Maysour, NES}, year={1998}, month={Feb}, pages={159–166} }
 @article{alsabagh_zaki_badawi_1997, title={Effect of binary surfactant mixtures on the stability of asphalt emulsions}, volume={69}, ISSN={["0268-2575"]}, DOI={10.1002/(SICI)1097-4660(199707)69:3<350::AID-JCTB699>3.0.CO;2-7}, abstractNote={The interfacial tension (IFT) of different asphalt components (aromatics, waxes, resins and asphaltenes) as 10% solutions in kerosene against different surfactant solution systems has been measured. The data revealed that both asphaltenes and waxes increased the IFT while aromatics and resins decreased it. The former two components are believed to destabilize asphalt emulsions, on the other hand, the latter two components facilitate asphalt emulsion formation and stability. A correlation between the rheological properties of the prepared asphalt emulsions by different binary and single surfactants mixtures and the stability of the emulsion was investigated. The flow curves of the different emulsion formulations clarified that the rheograms were found to attain plastic properties. The yield values, τ B and plastic, and apparent viscosities, ζ pl and ζ app respectively, were determined from these plots. The results showed that the enhancement of the rheological properties of the asphalt emulsions using different binary surfactant systems were in the following order: dodecyl benzene sulfonic acid sodium salt (DDBS-Na)/decyl phenol ethoxylate e.o. = 15 (DPE-15)> 1,1' (lauryl amido)-propyl ammonium chloride (LAPAC)/DPE-15 > DPE-15 > DDBS-Na > LAPAC. On the other hand, the order of emulsion stability is as follows: LAPAC > DDBS-Na/DPE-15 > DPE-15 > DDBS-Na. The effect of the aqueous phase salinity up to 5% NaCl concentration on the stability of asphalt emulsions stabilized by different surfactant solutions systems is discussed.}, number={3}, journal={JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY}, author={AlSabagh, AM and Zaki, NN and Badawi, AFM}, year={1997}, month={Jul}, pages={350–356} }
 @article{zaki_al-sabagh_1997, title={The efficiency of polyalkyl phenols polyalkylenepolyamines formaldehyde ethoxylates as demulsifiers for water-in-crude oil emulsions}, volume={34}, number={1}, journal={Tenside, Surfactants, Detergents}, author={Zaki, N. N. and Al-Sabagh, A. M.}, year={1997}, pages={12–17} }
 @misc{zaki_kilpatrick_carbonell, title={Methods of deresinating crude oils using carbon dioxide}, volume={7,622,035}, number={1999 Nov. 24}, author={Zaki, N. N. and Kilpatrick, P. K. and Carbonell, R. G.} }