Surfactant catalytic hydrogen production

LO-CAT A process for removing hydrogen sulfide and organic sulfur compounds from petroleum fractions by air oxidation in a cyclic catalytic process similar to the Stretford process. The aqueous solution contains iron, two proprietary chelating agents, a biocide, and a surfactant the formulation is known as ARI-310. The sulfur product is removed as a slurry. Developed in 1972 by Air Resources (now ARI Technologies) and first commercialized in 1976. Over 125 units were operating in 1996. An improved version, LO-CAT II, was announced in 1991. 

Wai and collaborators have succeeded in the hydrogenation of arenes with Rh nanopartides in a water-in-supercritical CO2 emulsion [33]. The catalytic system was prepared by mixing an aqueous solution of RhCls and a mixture of surfactants containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and a co-surfactant perfluoropolyetherphosphate (PFPE-PO4). The introduction of dihydrogen in the reactor allowed the formation of Rh(0) colloids with a mean size in the range 3-5 nm which led to the reduction of naphthalene to tetraline and that of phenol to cyclohexanol as major products. 

Palladium on charcoal, as the most simple Pd(0)-species, is capable of catalysing the coupling of aryl halides to produce biaiyls. The molecular hydrogen is also a suitable stoichiometric reductant, compatible with Pd-C, which converts the Pd(Il) back to the catalytically active Pd(0)-species as illustrated in the method J. The reactions have been conducted in water in the presence of nonionic surfactant, PEG-400, to provide the water soluble forms, e.g. micelles, of hydrophobic substrates such as chlorobenzene. Due to the nature of reductant, molecular hydrogen, the reactions were performed in an autoclave under pressure of hydrogen (4 atm.). This reaction is apparently an important basis for environmental friendly, inexpensive and economic process for scale-up production of symmetrical biaryls, however, the formation of dehalogenated products (up to 45%) is still an unsolved side-reaction. 

Asymmetric epoxidation of terminal alkenes with hydrogen peroxide was optimized with electron-poor chiral Pt(II) complexes bearing a pentafluorophenyl residue, as described in Section 23.3.1.6. The same catal3rtic system was made more sustainable by the employment of water as the solvent under micellar conditions. Surfactant optimization revealed the preferential use of neutral species like Triton-XIOO to solubihze both the catalyst and substrates. In several cases an increase of the asymmetric induction was observed (Scheme 23.43). The use of an aqueous phase and the strong affinity of the catalyst for the micelle allowed the recycling of the catalytic system by means of phase separation and extraction of the reaction products using an apolar solvent (hexane). The aqueous phase containing the catalyst was reused for up to three cycles with no loss of activity or selectivity. 

Branched-chain alcohols were used extensively for surfactant manufacture prior to the changeover to the more readily biodegradable hnear products. They were usually derived from polypropylenes by the oxo process, which involves catalytic addition of carbon monoxide and hydrogen to the double bond in a sequence of reactions. Thus the tetrapropylene derivative is nominally a C13 alcohol, as highly branched as the original raw material. 

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