Industrial applications of cationic surfactants

One other industrial application of cationic drag reducing additives is found in oil and gas production where cetyltrimethylammonium salicylate and cetyl pyridinium salicylate have been found simultaneously to reduce drag and inhibit corrosion of tubular steel injection lines [86]. 

Gas hydrate inhibitors. Gas hydrates, solid water clathrates containing small hydrocarbons, are problematic for oil and gas production because they can precipitate and cause line blockage. Simple cationic surfactants containing at least two butyl groups were previously developed to inhibit formation of gas hydrate precipitates in gas production lines [87]. However, similar to the situation with cationic drag reduction additives, poor toxicity profiles prevent widespread commercial acceptance. Ester quaternaries with structures somewhat similar to those used in fabric care have been claimed as hydrate inhibitors [88 ]. Additionally, certain alkylether quaternary compounds, e.g. C12-C14 alkyl polyethoxy oxypropyl tributyl ammonium bromide, were shown to have hydrate inhibition properties [89]. 

Fuel applications. Bitumen, the residuum of petroleum distillation, is gaining interest as a low cost fuel. The main problem with bitumen as a fuel is handling the viscous, almost solid product. This issue has been addressed by emulsifying molten bitumen in water using cationic surfactants such as tallow alkyl propanediamine [92] and salts of similar amines with fatty acids [93]. The emulsions thus prepared are pumpable and useful as fuels for stationary burning such as in power generation facilities. 

A microemulsion fuel suitable for use in diesel engines has been prepared from diesel fuel, ethanol, traces of water and cationic surfactants as emulsifiers, plus other additives [94]. Suitable cationic surfactants are alkyl polyamines and their alkoxylates. The fuels benefit from improved lubricity. 

Biocidal applications. The use of quaternary ammonium salts in disinfecting systems for household and industrial cleaners has been known for many years [95, 96]. Alkyl-benzyldimethyl quaternaries, alkyltrimethyl quaternaries, and dialkyldimethyl quaternaries are the more commonly used biocidal quaternary ammonium salts [16]. Recently, dialkyldimethyl quaternary ammonium salts have received renewed attention as potential wood preservatives to replace the heavy metal types [97]. Metal-free wood preservative formulations containing dialkyldimethyl ammonium salts with non-halide anions, such as carboxylates, borates, and carbonates, have been developed [98, 99]. 

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