Surfactant molecules are tested as water-in-crude emulsion breakers to attain the quickest separation rate in the so-called “proportional regime”. A concept of demulsifier performance is proposed on the basis of the required demulsifier concentration to offset the effect of a given amount of asphaltenes. The experimental evidence allows one to rank the tested products and relate their performance to their hydrophilicity and molecular weight. Some evidence indicates that the presence of acids in the crude makes it easier to break emulsions and suggests that so-called “extended surfactants” can significantly shorten the demulsifying process.

Anionic extended surfactants of the alkyl polypropylene oxide sulfate type are found to obey the linear correlation lnS = k ACN for optimum formulation (three-phase behavior) of ionic surfactant-oil-water systems, with a k value essentially the same as for n-alkyl sulfates. The addition of n-pentanol produces a shift in optimum formulation without significant change in k. An increase in temperature is found to produce a decrease in surfactant hydrophilicity, which is opposite to the expected behavior of anionic species. This trend, which is typical of nonionic surfactant behavior, is probably due to the partial hydration of the very first propylene oxide units which are located close to the anionic head group.

Two families of extended surfactants were prepared with the same head groups (carboxylate, sulfate, disodium phosphate) and different intermediate spacer structures. In one there was an average of 7 propylene oxide groups on the side of the tail and an average of 7 ethylene oxide groups on the side of the head, to produce a sequence of two different polarity segments. In the other case the spacer contained the same average numbers of propylene and ethylene oxide groups but in some homogeneous arrangement. The intermediate spacer structure, without ionic head group and in the cases of the carboxylate and sulfate extended surfactants, had a packing density reduction which is associated to the homogeneously alkoxide arrangement in the spacer. Such an arrangement was found to produce about 20% more surface area at the interface, apparently because it results in some plumpness due to the spacer folding to remain close to the interface. Both the critical micelle concentration and occupied interfacial area of the extended surfactant increased with the ionization of the anionic group associated with the electrostatic repulsion effect.

Following a new four-step route, we prepared a family of "extended" glucidoamphiphiles from Dglucose, D-galactose, and xylitol in which the n-dodecyl chain is attached to the glucidic moiety by the linkage Z = O-Et-O-Et-O-(α-PP-O-) n , where -O-(α-PP-O-) n is a poly-(α-propyloxy) commercial oligomeric mixture (with average length n = 6, 10, and 14). This amphiphilic behavior study showed that (i) the glucose derivative exhibits water solubility and hydrophilic-lipophilic balance values that are close to those found for the glucose compound with Z = -O-(α-PP-O-) n (without the Et-O-Et group), (ii) all these compounds are more strongly hydrophilic than the corresponding glucidic derivatives with Z = O, (iii) the increase of the poly-(α-propyloxy) chain length from ñ = 6 to ñ = 14 tends to reduce the hydrophilicity slightly.In a companion paper (1) comparing of the surfactant properties of 3-O-n-dodecyl-D-glucopyranose (23) and its "extended" homolog 3-O-n-dodecyl-O-(α-PP-O-) n -D-glucopyranose (8) in which (α-PP-O-) n = poly-(α-propyloxy) with ñ = 6, we showed that compound 8 exhibited a 100-fold increase in water solubility and a four-unit increase in hydrophiliclipophilic balance (HLB) with respect to compound 23. These results stimulated us to prepare and study the properties of the structural analogs of 8 with different glucidic moieties and of variable poly-(α-propyloxy) length. Before proceeding further, we tried to analyze the reasons for the low overall yield (10%) encountered in the synthesis of the "extended" species 8 along a six-step route (Scheme 1). This was obviously a consequence of the key step e, which required an activated substrate with a leaving group (OMs) linked to a primary carbon to introduce the glucose derivative 6. In the starting oligomeric mixture, 1, there was a secondary carbon at one of the extremities and a primary carbon at the other. Therefore, we first protected this position regiospecifically by a trityl group (step a). Subsequently, the alkyl chain, R, was introduced at the terminal secondary carbon with n-dodecyl bromide (step b). To obtain the activated intermediate, 5, the trityl group was then removed (step c) to introduce the mesylate group (step d), which was substituted by 1,2:5,6-di-O-isopropylidene-α-D-glucopyranose (6). Final desacetalation (step f ) produced the expected compound 8.In the present paper, we describe an alternative four-step route to attain slightly different "extended" glucidoamphiphiles such as compound 18 (Scheme 2), in which a diethyloxy group is introduced between the glucidic moiety and the poly-(α-propyloxy) spacer arm. This strategy is applied in preparing the corresponding D-glucose, D-galactose, and DL-xylitol derivatives with poly-(α-propyloxy) oligomers having an average degree of condensation, ñ, ranging from 6 to 14. This new "extended" glucidoamphiphile family includes enough members that some conclusions can be drawn on the influence of the di-ethyloxy group, the poly-(α-propyloxy) oligomer chain length, and the glucidic moiety on the ...

We prepared a new nonionic surfactant, 8, in which the n-dodecyl chain is attached at the C-3 carbon of the D-glucose-based glucopyranose moiety by the linkage Z = -O-(α-PP-O) n with -O-(α-PP-O) n being a commercial poly-(αpropyloxy) oligomeric mixture (with average ñ = 6). This amphiphilic behavior study showed that, when compared to the reference compound 3-O-dodecyl-D-glucopyranose (Z = O), compound 8 exhibits (i) a water solubility that is 100-fold higher, (ii) a hydrophilic-lipophilic balance value increase from 8.5 to 12.6 units, and (iii) a slighly lower critical micelle concentration. SCHEME 2 a, Trityl (Tr) chloride (1.5 equiv), pyridine, reflux, 3 h (95%) 9; b, n-C 12 H 25 -Br (1.1 equiv), KOH (2.2 equiv), 4:1 toluene/dimethylsulfoxide (DMSO), room temperature (RT) 72 h (60%) 9; c, 4:1 AcOH/H 2 O, 100°C, 1 h 30 min (93%) 9; d, mesyl (Ms) chloride (1.1 equiv), 1:1 toluene/triethylamine, RT 72 h (60%); e, 6 (1.6 equiv), KOH (3.2 equiv), 4:1 toluene/DMSO, RT 72 h (52%); f, 9:1 CF 3 COOH/H 2 O, RT 30 min, twice (58%).

New extended anionic surfactants with a carboxylate or sulfate polar head were synthesized from polypropoxylated alcohols, and their structures were confirmed by 1 H and 13 C nuclear magnetic resonance analysis. The extended surfactant critical micelle concentration was found to decrease with the length of the polypropylene glycol spacer. Surfactants containing a diethylene glycol link to the head group exhibited a higher critical micelle concentration than did their nondiethoxylated homologs.

Carboxylate derivatives of cardanol and anacardic acids, which are the main phenolic components of cashew nut shell oil were prepared and tested as anionic surfactants. They lower the surface tension, exhibit a critical micelle concentration, and produce microemulsions in mixtures with dodecyl sulfate. The values of their characteristic parameters in the hydrophilic-lipophilic deviation scale attained by the unidimensional formulation scan method typify them as hydrophilic surfactants.

A new class of extended surfactants was prepared in which the spacer arm between the polar portion and the hydrophobic alkyl chain was a polymer of propylene glycol with an average length of six propylene oxide units. The polar head was a single or double xylitol moiety or a xylitol molecule with carboxylic acid functionality. Surfactants containing double xylitol polar head groups showed a much higher critical micelle concentration value than surfactants with a single polar head.Paper no. S1456 in JSD 8, 193-198 (April 2005).