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Precious metal catalysts hydrogenation

Brosha E, Choi Jong-Ho, Davey J, Garzon F, Hamon C, Piela B, Ramsey J, Uribe F and Zelenay P (2005) Non-Precious Metal Catalysts, Hydrogen, Fuel Cells Infrastructure Technologies Program, 2005 Annual Review, Washington, DC, May 23-27, 2005. [Pg.104]

Dry reduced nickel catalyst protected by fat is the most common catalyst for the hydrogenation of fatty acids. The composition of this type of catalyst is about 25% nickel, 25% inert carrier, and 50% soHd fat. Manufacturers of this catalyst include Calsicat (Mallinckrodt), Harshaw (Engelhard), United Catalysts (Sud Chemie), and Unichema. Other catalysts that stiH have some place in fatty acid hydrogenation are so-called wet reduced nickel catalysts (formate catalysts), Raney nickel catalysts, and precious metal catalysts, primarily palladium on carbon. The spent nickel catalysts are usually sent to a broker who seUs them for recovery of nickel value. Spent palladium catalysts are usually returned to the catalyst suppHer for credit of palladium value. [Pg.91]

Ultradeep desulfurization of fuel oils is used for producing not only clean fuels but also sulfur-free hydrogen used in fuel-cell systems, in which the hydrogen can be produced potentially through the reforming of fuel oils. Fuel-cell systems must be run with little-to-no sulfur content, because sulfur can irreversibly poison the precious metal catalysts and electrodes used [12]. [Pg.146]

Complex 5 was more active than the well-known precious-metal catalysts (palladium on activated carbon Pd/C, the Wilkinson catalyst RhCl(PPh3)3, and Crabtree s catalyst [lr(cod)(PCy3)py]PFg) and the analogous Ai-coordinated Fe complexes 6-8 [29] for the hydrogenation of 1-hexene (Table 2). In mechanistic studies, the NMR data revealed that 5 was converted into the dihydrogen complex 9 via the monodinitrogen complex under hydrogen atmosphere (Scheme 4). [Pg.31]

Table 2 Comparison of iron complexes with transition precious-metal catalysts for the hydrogenation of 1-hexene... Table 2 Comparison of iron complexes with transition precious-metal catalysts for the hydrogenation of 1-hexene...
Hydrogenation of substrates having a polar multiple C-heteroatom bond such as ketones or aldehydes has attracted significant attention because the alcohols obtained by this hydrogenation are important building blocks. Usually ruthenium, rhodium, and iridium catalysts are used in these reactions [32-36]. Nowadays, it is expected that an iron catalyst is becoming an alternative material to these precious-metal catalysts. [Pg.35]

Precious metal catalysts have shown to be effective for the desulfurization of the steri-cally hindered compounds. One example is given with a commercial catalyst using both, palladium and platinum [23]. The high activity of these metals towards hydrogenation would result in aromatic saturation reactions, and consequently an increase in operating costs (not only for the catalyst cost but also for the increase in hydrogen uptake). [Pg.21]

The reverse reaction, namely hydrogenation, has also frequently been used to decrease the degree of unsaturation present in macrocyclic systems - typically converting imine linkages to amine groups. Such hydrogenations have usually been performed catalytically (for example, using H2 in the presence of Raney nickel or a precious metal catalyst) or by means of chemical reductants such as sodium borohydride. [Pg.220]

The highest demands made on the purity of the produced hydrogen are for its use in fuel cells, since even the slightest trace of carbon monoxide impedes the functioning of the precious metal catalyst in the fuel cell.10 For the platinum used in hydrogen fuel... [Pg.296]

Aqueous phase reforming of glycerol in several studies by Dumesic and co-workers has been reported [270, 275, 277, 282, 289, 292, 294, 319]. The first catalysts that they reported were platinum-based materials which operate at relatively moderate temperatures (220-280 °C) and pressures that prevent steam formation. Catalyst performances are stable for a long period. The gas stream contains low levels of CO, while the major reaction intermediates detected in the liquid phase include ethanol, 1,2-pro-panediol, methanol, 1-propanol, propionic acid, acetone, propionaldehyde and lactic acid. Novel tin-promoted Raney nickel catalysts were subsequently developed. The catalytic performance of these non-precious metal catalysts is comparable to that of more costly platinum-based systems for the production of hydrogen from glycerol. [Pg.222]

Figure 1731. Fluidized bed reactor processes for the conversion of petroleum fractions, (a) Exxon Model IV fluid catalytic cracking (FCC) unit sketch and operating parameters. (Hetsroni, Handbook of Multiphase Systems, McGraw-Hill, New York, 1982). (b) A modem FCC unit utilizing active zeolite catalysts the reaction occurs primarily in the riser which can be as high as 45 m. (c) Fluidized bed hydroformer in which straight chain molecules are converted into branched ones in the presence of hydrogen at a pressure of 1500 atm. The process has been largely superseded by fixed bed units employing precious metal catalysts (Hetsroni, loc. cit.). (d) A fluidized bed coking process units have been built with capacities of 400-12,000 tons/day. Figure 1731. Fluidized bed reactor processes for the conversion of petroleum fractions, (a) Exxon Model IV fluid catalytic cracking (FCC) unit sketch and operating parameters. (Hetsroni, Handbook of Multiphase Systems, McGraw-Hill, New York, 1982). (b) A modem FCC unit utilizing active zeolite catalysts the reaction occurs primarily in the riser which can be as high as 45 m. (c) Fluidized bed hydroformer in which straight chain molecules are converted into branched ones in the presence of hydrogen at a pressure of 1500 atm. The process has been largely superseded by fixed bed units employing precious metal catalysts (Hetsroni, loc. cit.). (d) A fluidized bed coking process units have been built with capacities of 400-12,000 tons/day.
To date, the best studied modified systems are Pt catalysts inhibited with sulfur compounds, morpholine or phosphorous compounds (ref. 5). Raney nickel modified with dicyandiamide has also been reported to be able to hydrogenate aromatic chloronitro compounds with very good selectivities and activities. Since nickel is an attractive alternative to precious metal catalysts we decided to search for other types of inhibitors and to investigate the stage at which dehaiogenation occurs. [Pg.321]

A large number of heterogeneous catalysts have been tested under screening conditions (reaction parameters 60 °C, linoleic acid ethyl ester at an LHSV of 30 L/h, and a fixed carbon dioxide and hydrogen flow) to identify a suitable fixed-bed catalyst. We investigated a number of catalyst parameters such as palladium and platinum as precious metal (both in the form of supported metal and as immobilized metal complex catalysts), precious-metal content, precious-metal distribution (egg shell vs. uniform distribution), catalyst particle size, and different supports (activated carbon, alumina, Deloxan , silica, and titania). We found that Deloxan-supported precious-metal catalysts are at least two times more active than traditional supported precious-metal fixed-bed catalysts at a comparable particle size and precious-metal content. Experimental results are shown in Table 14.1 for supported palladium catalysts. The Deloxan-supported catalysts also led to superior linoleate selectivity and a lower cis/trans isomerization rate was found. The explanation for the superior behavior of Deloxan-supported precious-metal catalysts can be found in their unique chemical and physical properties—for example, high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions (Wieland and Panster, 1995). The majority of our work has therefore focused on Deloxan-supported precious-metal catalysts. [Pg.231]

Iso-Kel process a fixed-bed, vapor-phase isomerization process using a precious metal catalyst and external hydrogen. [Pg.439]

TABLE 1. Perspective non- precious metals catalysts for hydrogen oxidation... [Pg.178]

The Selectoxo process (Engelhard) reduces the hydrogen consumption of the methanation system, as well as the inert gas content of the purified synthesis gas fed to the synthesis loop. After low-temperature shift conversion, the cooled raw gas is mixed with the stoichiometric quantity of air or oxygen needed to convert the carbon monoxide to carbon dioxide. The mixture is then passed through a precious-metal catalyst at 40-135 °C to accomplish this selective oxidation [740]-[743], The carbon dioxide formed by the Selectoxo reaction adds only slightly to the load on the downstream carbon dioxide absorption system. [Pg.136]

Recently, extensive efforts have been made to synthesize liquid hydrocarbons from biomass feedstocks. In 2004, Dumesic and co-workers reported that a clean stream of alkanes could be produced by aqueous phase reforming of sorbitol over a bifunctional catalyst. The sugar is repeatedly dehydrated using a solid acid catalyst and then hydrogenated using a precious metal catalyst such... [Pg.113]

Copper catalysts are cheaper and work just as well as the precious metal catalysts. However, complete removal of catalyst from the hydrogenated oil is never possible. Copper, present in the oil even at very low concentrations (less than 0.05 ppm) can cause rapid hydrolysis in the oil during frying. [Pg.2006]

Ammonium nitrate solution is reduced to hydroxylamine phosphate with hydrogen under pressure on a suspended precious metal catalyst (substrate activated charcoal) in the presence of phosphoric acid (HPO Hydroxylamine Phosphate Oxime) ... [Pg.52]


See other pages where Precious metal catalysts hydrogenation is mentioned: [Pg.208]    [Pg.238]    [Pg.559]    [Pg.529]    [Pg.111]    [Pg.111]    [Pg.38]    [Pg.110]    [Pg.405]    [Pg.578]    [Pg.351]    [Pg.19]    [Pg.7]    [Pg.57]    [Pg.33]    [Pg.234]    [Pg.230]    [Pg.348]    [Pg.137]    [Pg.309]    [Pg.19]    [Pg.111]    [Pg.111]    [Pg.2006]    [Pg.591]    [Pg.51]    [Pg.63]    [Pg.326]   
See also in sourсe #XX -- [ Pg.414 ]




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