Nanostructured Carbon–Metal Oxide Hybrids as Amphiphilic Emulsion Catalysts

Abstract

Nanohybrids composed of "onion-like" carbon, single-walled (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) fused to silica or alumina particles have been compared as stabilizers of water/oil emulsions and interfacial catalysts. The amphiphilic character of these nanohybrids makes them effective in stabilizing emulsions (up to 85 % of total volume) comprising of small droplets (less than 40 μm). Furthermore, these nanohybrids have been used as supports for transition metal particles (palladium and copper) to catalyze reactions at the water/oil interface. Three different reaction systems have been conducted in the emulsions to demonstrate the principle: 1) hydrogenation of phenanthrene; 2) hydrogenation of glutaraldehyde and benzaldehyde; 3) oxidation of tetralin. Comparison of the maximum conversions achieved in emulsions as opposed to the single phase, together with much better control of selectivity in the two-phase system shows the benefits of using these nanohybrid catalysts.

Phase‐Reversal Emulsion Catalysis with CNT–TiO2 Nanohybrids for the Selective Oxidation of Benzyl Alcohol

“…Recently, emulsion catalysis has received considerable attention as a highly efficient catalysis technique, because of its great potential in oxidation desulfurization,1 alcohol oxidation,2 alkene epoxidation,3 aldehyde hydrogenation,4 and biofuel upgrade reactions 5. Up to now, various emulsifiers, including surfactants1b, c, 6 and solid nanoparticles,2–5, 7 have been used in the emulsion system and tested as emulsion catalysts.…”

Oil-in-water Pickering emulsions stabilized with functionalized multi-walled carbon nanotube/silica nanohybrids in the presence of high concentrations of cations in water

“…In this respect, nanotechnology, as a leading edge and promising technology, has recently attracted the attention of many scientists. Various strategies have so far been proposed for implementation of this technology in EOR processes, among which are the use of polymeric nanocomposites [5,6], synthesis and application of emulsions and micro-emulsions in EOR process [7][8][9], the use of nanocatalysts in water and oil interface within oil reservoirs [10][11][12], employing nano-surfactants [13,14], and the injection of metallic nanomaterials into the oil reservoirs [15]. The diversity in these listed efforts to integrate nanotechnology in EOR processes can be attributed to the following factors: (A) intense diversity in the type of oil and its reservoirs, (B) diversity in EOR mechanisms and methods, (C) the area in nanotechnology application is still in its infancy and the effectiveness of each proposed method has to be proved in practical terms.…”

“…structure and metal oxides have favorable catalytic properties, and their nanohybrids would inevitably inherit the catalytic properties [12]. Generally, the multi-walled carbon nanotube (MWCNT)/silica nanohybrids can be synthesized through the following two methods: the implementation of silica structures in MWCNT formation reaction [17], and incorporating MWCNT in the reaction to form silica structure.…”

Preference of Nano porous graphene to Single-Walled Carbon Nanotube (SWCNT) for preparing Silica Nano hybrid Pickering Emulsion for potential Chemical Enhanced Oil Recovery (C-EOR)

“…Therefore, we anticipate that the SWCNT-silica combination o ers a unique structure that can o er great exibility in controlling the surface wettability by adjusting the carbon/silica ratio. Thus, it is possible to modify the distributions of partitioning coe cients between oil and water [4].…”