Reduction-deposition

The deposition-reduction (DR) method is based on the weak electrostatic interactions of polymer surfaces with the oppositely charged Au(III) complex ions, leading to the reduction of Au(III) exclusively on the polymer surfaces. Appropriate anionic or cationic Au(III) precursors are chosen based on the zeta potentials of polymer supports (Figure 3.6) [43]. 

Figure 3.6 Schematic representation of deposition-reduction (DR) method (a) positiveiy charged supports and (b) negativeiy charged supports.

Figure 7. Gold NPs directly deposited on PVC microbeads by deposition-reduction method.

We have recently deposited directly onto activated carbons and polymer microbeads by deposition-reduction method and have found that gold NPs on pol5mers exhibit remarkably high catalytic activity, which may exceed those of Au/activated carbons and Au/ fine Ce02. The type of polymers and their functional groups are critical to the catalytic activity. 

Bio-ethanol is attracting growing interests in relation to the shift of raw materials from petroleum to biomass. A pioneering work by Christensen is that over MgAl203 support gold is much more selective to acetic acid than palladium and platinum in the aerobic oxidation of ethanol in water in a batch reactor. Figure 32 shows that selectivity to acetic acid exceeds 80% [99]. In contrast, Au/Si02 catalysts prepared by deposition reduction... 

Highly active Au catalysts can be prepared by an appropriate selection of preparation methods such as co-precipitation (CP), deposition-precipitation (DP), deposition-reduction (DR) and solid grinding (SG) with dimethyl Au(III) acetylacetonate, depending on the kind of support materials and reactions targeted. 

TABLE LXXXIII. DEPOSITION (REDUCTION) POTENTIALS FOB SIMPLE AND COMPLEX... 

Jantzen PT, Connor KE, DiCarlo G, Wenk GL, Wallace JL, Rojiani AM, Coppola D, Morgan D, Gordon MN (2002) Microglial activation and beta -amyloid deposit reduction caused by a nitric oxide-releasing nonsteroidal anti-inflammatory drug in amyloid precursor protein plus presenilin-1 transgenic mice. J Neurosci 22 2246-2254. 

The design and formulation of abatement strategies to achieve cost effective deposition reductions employs theoretical models to unravel the complex processes which link NO, emissions to oxidised nitrogen deposition in Europe. Many uncertainties still remain in these theoretical studies and it is therefore important to demonstrate that any abatement strategy developed is robust to changes in understanding of the processes involved. 

Similarly, when powdery aluminum substrates are used, due to the porosity of deposited Cu and dissolution of Al, hollow copper particles can be obtained, as illustrated in Fig. 3. These results strongly suggest that there is a difference between the rates of dissolution (oxidation of less noble metal) and deposition (reduction of more noble metal). 

Table 4.14 Deposit reduction of a heavy-duty diesel engine oil containing antioxidant B in the Caterpillar 1N diesel engine test...

Temp. °C Weight gain2 ng/cm Exposure Conditions Weight gain2 ng/cm Temp. °C Time h Carbon uptak rpg/an Deposition Reduction Factor (a) Temp. °C Time h Weight gaii ng/cm (b) Deposition Reduction Factor (a) ... 

Temp °C Time h Sulphur content % (a) Temp C Time h Acetone pressure Still Carbon uptake % (a) Deposition reduction factor (c) Sulphur content after exposure % (a)... 

Weight gain during lOOOh oxidation In CO, at 600 0 Deposition exposure conditions Sulphur uptak ug/cm Carbon uptakg mg/cm Deposition reduction factor a... 

Sulphur bearing Partial pressure (atm) Exposure Sulphur. uptake Carbon) uptake % Deposition reduction factor ... 

Vitry (France) Screen tube deposits Reduced deposits. Reduction in soot blowing requirements... 

Alternatives to aqueous processing or dry or nonaqueous processing techniques have heen tried hut none, until recently, have been used on a true industrial scale for fuel reprocessing. Examples of these include separations based on (1) differences in volatility of the hahdes, especially fluorine compounds (2) molten salt (liquid-liquid) extraction where fuel dissolved in a molten salt is then contacted with a heat resistant low volatility second phase such as 100% TBP or a liquid metal and, (3) electrorefining, where controlling the cell potential results in removal of a metal from a molten salt by the selective deposition (reduction) on a cathode. 

The deposition reduction (DR) method was used in an initial attempt to deposit nanogold on the surfaces of BP a solution of HAUCI4 in methanol was added to a turbid solution of BP in methanol, followed by filtration, dispersion in methanol, and reduction with NaBH4. However, nanogold was not deposited on the surface. The zeta potential of the support is negative (-33.24 mV), so AuCl4 hardly binds to the surface. To overcome this difficulty, we used polyethyleneimine (PEI) as a binder for nanogold deposition. ... 

In general, electrowinning (EW) is commonly used to produce atomic Zn, Ni, and Cu from their their ionic solutions. The common reactions involved in producing metals by electrolytic deposition (reduction), provided that impurities codeposition is absent and that the electrochemical cell walls and anodes do not dissolve, are... 

Vapor Deposition Reduction of chemical vapors, e.g. nickel carbonyl, produces a... 

However, as understanding of the basic ecological effects of acid depositions improves, it is becoming apparent that emission abatement to achieve the necessaiy deposition reductions, in some areas, will be called for that are considerably in excess of those envisaged by the existing international agreements. To take one example, it has been estimated that a reduction of approximately 75 per cent in S deposition (from approximately 80 keq km yr to approximately 20 keq km ... 

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