Surfactants branched

The basic flow sheet for the flotation-concentration of nonsulfide minerals is essentially the same as that for treating sulfides but the family of reagents used is different. The reagents utilized for nonsulfide mineral concentrations by flotation are usually fatty acids or their salts (RCOOH, RCOOM), sulfonates (RSO M), sulfates (RSO M), where M is usually Na or K, and R represents a linear, branched, or cycHc hydrocarbon chain and amines [R2N(R)3]A where R and R are hydrocarbon chains and A is an anion such as Cl or Br . Collectors for most nonsulfides can be selected on the basis of their isoelectric points. Thus at pH > pH p cationic surfactants are suitable collectors whereas at lower pH values anion-type collectors are selected as illustrated in Figure 10 (28). Figure 13 shows an iron ore flotation flow sheet as a representative of high volume oxide flotation practice. 

Cosurfactant requirements can be minimized usiag a surfactant having a short-branched hydrophobe or a branched-alkyl substituent on an aromatic group (232,234) and a long ethoxy group chain (234). Blends of surfactants optimized for seawater or reservoir brine salinity include linear alkyl xylene sulfonate—alcohol ether sulfate mixtures (235). 

The odd-carbon stmcture and the extent of branching provide amyl alcohols with unique physical and solubiUty properties and often offer ideal properties for solvent, surfactant, extraction, gasoline additive, and fragrance appHcations. Amyl alcohols have been produced by various commercial processes ia past years. Today the most important iadustrial process is low pressure rhodium-cataly2ed hydroformylation (oxo process) of butenes. 

Miscellaneous Derivatives. Fimehc acid is used as an intermediate in some pharmaceuticals and in aroma chemicals ethylene brassylate is a synthetic musk (114). Salts of the diacids have shown utUity as surfactants and as corrosion inhibitors. The alkaline, ammonium, or organoamine salts of glutaric acid (115) or C-5—C-16 diacids (116) are useflil as noncorrosive components for antifreeze formulations, as are methylene azelaic acid and its alkah metal salt (117). Salts derived from C-21 diacids are used primarily as surfactants and find apphcation in detergents, fabric softeners, metal working fluids, and lubricants (118). The salts of the unsaturated C-20 diacid also exhibit anticorrosion properties, and the sodium salts of the branched C-20 diacids have the abUity to complex heavy metals from dilute aqueous solutions (88). 

Alkyl benzene sulfonates (ABS). Branched-chain anionic surfactants. Slow to biodegrade. Seldom used. 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

Effect of hydrophobe carbon number on AOS calcium tolerance. The hydrophobe chain branching and the di monosulfonate ratio were held constant in these experiments (5-7% branching and 5-7% disulfonate). Increasing AOS carbon number from 14-16 to 16-18 and finally to 20-24 greatly decreases the calcium ion tolerance of AOS see Fig. 3. Addition of less than 200 ppm calcium ion reduced the transmittance of an AOS 2024 surfactant to less than 10% of its initial value. Addition of more than 300 ppm calcium ion was required to reduce AOS 1618 solution transmittance by a similar amount. AOS 1416 was the most calcium-tolerant surfactant. Approximately 400 ppm calcium ion was required to reduce the transmittance of AOS 1416 solution to 10% of its initial value. 

Comparison of the first three surfactants in Table 7 shows that calcium ion tolerance decreases in the order AOS 2024 > IOS 2024 > VOS 2024. Olefin branching increases in the order AO 2024 < IO 2024 < VO 2024. The values of the di monosulfonate ratio and the average carbon number for the... 

Comparison of the second (IOS 2024) and last (linear IOS 2024) surfactants in Table 7 shows that the calcium ion tolerance of the linear hydrophobe surfactant is significantly greater than that of the partially branched hydrophobe surfactant. While branching was reduced substantially (33% to 6.6%) in going from IOS 2024 to linear IOS 2024, the hydrophobe carbon number and the disulfonate content of the surfactant were held constant. 

A study over a broader range of disulfonate monosulfonate ratios was then conducted with a series of AOS 2024 surfactants. Results are shown in Fig. 5. The carbon number and hydrophobe branching were held constant. The AS HAS ratio was 75 25. At a disulfonate monosulfonate ratio (D M) of 7 93, addition of less than 200 ppm calcium ion decreased solution transmittance to less than 10% of its initial value. When the disulfonate content of AOS 2024 was increased to 38 wt % (di monosulfonate ratio of 38 62), slightly more than 1000 ppm calcium ion was required to reduce solution transmittance to less than 10% of its initial value. When the surfactant consisted predominantly of disulfonate (di monosulfonate ratio of 84 16), the addition of more than 41,000 ppm calcium ion reduced the transmittance by less than 5% from its initial value. 

The presence of calcium and magnesium ions increases the adsorption of the surfactants at the water-air interface and leads to a corresponding lowering of the surface tension at the CMC as shown by the data in Table 4. A C16 branched AOS gives a lower surface tension than a linear C16 AOS this too is in agreement with other model studies and theoretical predictions [42, and Sec. 2 on interfacial tension). 

Entry Surfactant Parent olefin % branching Di monosul fonate (mol ratio) Aqueous phase Oil phase Interfacial tension (dynes/cm)... 

These samples differed slightly in the degree of hydrophobe branching. Although the difference in hydrophobe branching is small, it may be worthy of note that the more branched surfactant provided the lower IFT value. 

IOS 1518 is more highly branched than AOS (entry 7, Table 16). IOS 1518 also has the sulfonate group and the carbon-carbon double bond in different relative positions than AOS 1618. IOS 1518 exhibits a significantly lower adsorption than AOS 1618. Study of Table 16 shows that the molecular weights of these two surfactants are quite similar. The AOS 1618 does have a higher di monosulfonate ratio. 

Surfactant Substrate olefin (% branching) Unsulfonated organic material (wt %)b Foam half-life (min)... 

The direct reaction of 1-alkenes with strong sulfonating agents leads to surface-active anionic mixtures containing both alkenesulfonates and hydroxyalkane sulfonates as major products, together with small amounts of disulfonate components, unreacted material, and miscellaneous minor products (alkanes, branched or internal alkenes, secondary alcohols, sulfonate esters, and sultones). Collectively this final process mixture is called a-olefinsulfonate (AOS). The relative proportions of these components are known to be an important determinant of the physical and chemical properties of the surfactant [2]. 

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