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Catalytic phase

However, there may be good reasons why a catalyst should not consist of particles that are too small, as we saw in the beginning of this chapter, e.g. to avoid pressure gradients in the reactor. Based on an analysis such as the above, one can decide whether it makes sense to use support particles that contain a homogeneous distribution of the catalytic phase. With expensive noble metals, one might perhaps decide to use an egg-shell type of arrangement, where the noble metal is only present on the outside of the particles. [Pg.211]

The reduction steps on active Co sites are strongly affected by activated hydrogen transferred from promoter metal particles (Pt and Ru). Several indications for the existence and importance of hetero-bimetallic centers have been obtained.63 [Cp Co(CO)2] in the presence of PEt3 and Mel catalyzes the carbonylation of methanol with initial rates up to 44 mol L 1 h 1 before decaying to a second catalytic phase with rates of 3 mol L 1 h-1.64 HOAc-AcOMe mixtures were prepared by reaction of MeOH with CO in the presence of Co(II) acetate, iodine, and additional Pt or Pd salts, e.g., [(Ph3P)2PdCl2] at 120-80 °C and 160-250 atm.65... [Pg.148]

The catalytic phase can again be divided into the following processes ... [Pg.103]

Raffinate-II typically consists of40 % 1-butene, 40 % 2-butene and 20 % butane isomers. [RhH(CO)(TPPTS)3] does not catalyze the hydroformylation of internal olefins, neither their isomerization to terminal alkenes. It follows, that in addition to the 20 % butane in the feed, the 2-butene content will not react either. Following separation of the aqueous catalyts phase and the organic phase of aldehydes, the latter is freed from dissolved 2-butene and butane with a counter flow of synthesis gas. The crude aldehyde mixture is fractionated to yield n-valeraldehyde (95 %) and isovaleraldehyde (5 %) which are then oxidized to valeric add. Esters of n-valeric acid are used as lubricants. Unreacted butenes (mostly 2-butene) are hydroformylated and hydrogenated in a high pressure cobalt-catalyzed process to a mixture of isomeric amyl alcohols, while the remaining unreactive components (mostly butane) are used for power generation. Production of valeraldehydes was 12.000 t in 1995 [8] and was expected to increase later. [Pg.112]

Special mention should be made of organobimetallic catalytic phases where one or more of the organic fragments have chiral characteristics. In this case, by using SOMC/M techniques, heterogeneous chiral catalysts of very good quality in terms of chemo- and enantioselectivity, as well as good stability and reuse capability, have been obtained [45, 46]. [Pg.242]

The results for PtSn-BM and PtSn-OM catalysts (Figure 6.15) indicate that the addition of tin substantially improves their stability, almost inhibiting the deactivation processes. In the case of PtSn-OM, no deactivation is observed and only a slight loss in the conversion level is observed in the case of PtSn-BM. Nevertheless, in the latter case, catalyst regeneration in air at 773 K allows the original catalytic phase to be obtained, since it recovers its initial activity and selectivity. [Pg.273]

Further, the development of miniaturized devices for the generation of power and/ or heat is discussed here as it represents an emerging field of application of catalytic combustion. Due to the presence of the catalytic phase, the microcombustors have the potential to operate at significantly lower temperatures and higher surface-to-volume ratios than non-catalytic microcombustors. This makes them a viable solution for the development of miniaturized power devices as an alternative to batteries. [Pg.364]

Early studies in this field [35, 36] indicated that a high surface-to-volume ratio, which represents a hurdle for gas-phase combustion, is instead an advantage for catalytic combustion. In fact the small scale enhances considerably the rate of gas-solid mass transfer, which favors the kinetics of the combustion process and compensates for the short residence time. Also, as is well established for large-scale systems, the presence of a catalytic phase allows for stable combustion at significantly lower temperature than traditional homogeneous burners [55, 56]. This makes the design and operation of microcombustors more fiexible. Several recent studies have explored the potential of catalytic microcombustors using H2 [37, 38, 50], methane [37], propane [52,53,57] and mixtures of H2 with propane [57], butane [38,47,52] and dimethyl ether [52]. [Pg.374]

HRP/IL phase. The electrical conductivity of the PANI films prepared by solvent casting from the aqueous solutions showed a relatively high and similar value even after the fifth run (Fig. 12), which demonstrates the validity of our approach and the ease of recyclability and reuse of the enzyme inside the IL. For the PEDOT, the process of recovery and reuse was successfully repeated up to ten times using the same HRP/EDOT catalytic phase (Fig. 13), further confirming the success of the synthetic approach and the ease of recyclability and reuse of the enzyme inside the EDOT monomer phase. [Pg.17]

Rhone-Poulenc operates another biphasic process, the hydrogenation of a, 8-unsaturated aldehydes (64). The catalyst is readily made from hydrated RuC13 and tppts in water. The hydrogenation of various reactants (cinna-maldehyde, crotonaldehyde, or prenal) proceeds smoothly at low temperatures and under moderate partial pressures. It is possible to recycle the aqueous catalytic phase. The process is said to operate in a pilot plant, but the capacities are not known. [Pg.500]

The nucleophilic nature of the alkanes is also shown by the influence of the acidity level on their solubility. Torek and co-workers90 have investigated the composition of the catalytic phase obtained when w-pentane or w-hexane is thoroughly mixed with HF-SbF5 in an autoclave under hydrogen pressure [Eq. (5.41)]. The total amount of hydrocarbon in the catalytic phase (dissolved ions and neutrals) was obtained by extraction with excess of methylcyclopentane. The amount of physically dissolved... [Pg.524]

Figure 5.11. Variation of the composition of the catalytic phase as a function of the SbF5 concentration in the n-pentane isomerization in HF—SbF5.90 T — 15°C, pm = 5 bars, volume of the catalytic phase = 57 ml. , Mass of C5+, o, mass of C5H (Freon-113 extract) a, % weight of Cs+ + C5H (methylcyclopentane extract). Figure 5.11. Variation of the composition of the catalytic phase as a function of the SbF5 concentration in the n-pentane isomerization in HF—SbF5.90 T — 15°C, pm = 5 bars, volume of the catalytic phase = 57 ml. , Mass of C5+, o, mass of C5H (Freon-113 extract) a, % weight of Cs+ + C5H (methylcyclopentane extract).
The detailed kinetic study of this system shows that after the initial period during which the catalytic phase is formed, the experimental rate constant of isomerization K ... [Pg.527]

From an evaluation of the catalytic efficiency of 3-5 using standard catalytic phase-transfer benzylation of 1, it was found that all compounds had the ability to catalyze this phase-transfer benzylation, and in all cases the (S)-isomer of the benzylated imine 2a was formed in excess (Scheme 4.3). The 1,3-phenyl-linked dimeric PTC 4 showed the highest enantioselectivity among the three dimeric PTCs. The order of enantioselectivity of the three PTCs, along with the monomeric PTC M, was as follows 1,3-dimeric PTC 4 > 1,4-dimeric PTC 5 = monomeric PTC M 1,2-dimeric... [Pg.53]

The catalytic phase-transfer alkylation of 18 with l-chloro-4-iodobutane afforded the adduct (S)-201 in 88% yield and excellent 99% ee. Subsequent conversion of this intermediate (S)-20p into the final product (S)-39 was accomplished in high yield (the overall yield starting from 18 was 77%). [Pg.27]

Many practical catalysts consist of one or several active components, deposited on a high surface area support, whose purpose is the dispersion of the catalytically active component or components and their stabilization against sintering. In some cases, the support is passive in other cases, the support is not inert it is also part of the catalyst, combining oth functions, that is, the support and the active catalytic phases [56],... [Pg.429]

Thermally induced deactivation of catalysts is a particularly difficult problem in high-temperature catalytic reactions. Thermal deactivation may result from one or a combination of the following (i) loss of catalytic surface area due to crystallite growth of the catalytic phase, (ii) loss of support area due to support collapse, (iii) reactions/transformations of catalytic phases to noncatalytic phases, and/or (iv) loss of active material by vaporization or volatilization. The first two processes are typically referred to as "sintering." Sintering, solid-state reactions, and vaporization processes generally take place at high reaction temperatures (e.g. > 500°C), and their rates depend upon temperature, reaction atmosphere, and catalyst formulation. While one of these processes may dominate under specific conditions in specified catalyst systems, more often than not, they occur simultaneously and are coupled processes. [Pg.1]

ROLE OF SPILLOVER SPECIES IN PROTECTING CATALYTIC PHASES AGAINST HARMFUL DEACTIVATING TRANSFORMATIONS... [Pg.122]

The previous part of this section makes clear that, unless a method is found to directly prepare a catalytic phase (usually an oxide) containing all the wanted metallic elements, and in the required proportions, some more indirect method should be selected. In general, however, direct preparation from the gas or liquid phase will be impossible for the reasons given above. It becomes necessary to resort to a two-step or multiple-step approach using at least one solid precursor. [Pg.67]

One of the more popular techniques for producing dispersed-phase catalysts involves the use of water- or oil-soluble catalyst precursors. Small amounts of the water-soluble catalyst precursor are added to the coal-vehicle feed and are subsequently converted to a highly dispersed, insoluble catalytic phase. The reaction... [Pg.289]


See other pages where Catalytic phase is mentioned: [Pg.509]    [Pg.174]    [Pg.288]    [Pg.26]    [Pg.89]    [Pg.148]    [Pg.1396]    [Pg.19]    [Pg.126]    [Pg.381]    [Pg.448]    [Pg.288]    [Pg.355]    [Pg.309]    [Pg.192]    [Pg.185]    [Pg.481]    [Pg.509]    [Pg.312]    [Pg.525]    [Pg.527]    [Pg.528]    [Pg.50]    [Pg.118]    [Pg.341]    [Pg.63]    [Pg.69]    [Pg.173]   
See also in sourсe #XX -- [ Pg.190 ]




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Alkylation catalytic phase-transfer

Analysis of Three-Phase Catalytic Reactions

Application Catalytic Three-Phase Hydrogenation of Citral in the Monolith Reactor

Asymmetric epoxidation catalyzed by novel azacrown ether-type chiral quaternary ammonium salts under phase-transfer catalytic conditions

Asymmetric epoxidation under phase-transfer catalytic

Catalytic Oxidation by Nitrous Oxide in the Gas Phase

Catalytic Reactions Involving Three Phases

Catalytic active phases, single

Catalytic asymmetric phase-transfer

Catalytic asymmetric phase-transfer Mannich-type reaction

Catalytic asymmetric phase-transfer Michael addition

Catalytic asymmetric phase-transfer alkylation

Catalytic cracking liquid-phase reactions

Catalytic cracking vapor-phase reactions

Catalytic enantioselective phase-transfer

Catalytic enantioselective phase-transfer alkylation

Catalytic gas-phase reactions

Catalytic liquid phase oxidations with

Catalytic multi-phase systems

Catalytic phase material

Catalytic reactions in liquid phase

Catalytic reactions, phase transfer

Catalytic two phase reactions

Catalytic two-phase systems

Catalytic vapor-phase

Catalytic with hydrogen peroxide under phase

Chiral catalytic phase transfer

Composite Catalytic Phases

Continuous catalytic hydrogenation liquid-phase

Continuous catalytic hydrogenation vapor-phase

Counter-phase Transfer Catalytic Reactions

Effects of organic solvents on other phase-transfer catalytic reactions

Gas-phase heterogeneous catalytic

Gas-phase heterogeneous catalytic reactions

Heterogeneous catalytic processes phases

Hydrogenation vapor phase catalytic

Kinetics of Catalytic Hydrogenations in the Liquid Phase

Liquid phase catalytic processing

Liquid-Phase Catalytic Oxidations with Perovskites and Related Mixed Oxides

Liquid-phase catalytic hydrogenation

Liquid-phase catalytic oxidations

Microreactors for Catalytic Gas-Phase Reactions

Multi-phase catalytic membrane

Multi-phase catalytic membrane reactions

Multi-phase catalytic membrane reactors

Other effects on the phase-transfer catalytic reactions

Phase catalytic conditions

Phase catalytic enantioselective

Phase-transfer catalytic oxidation

Phase-transfer catalytic oxidation medium

Porous solid catalytic phase

Reaction vapor-phase catalytic

Reactors for Catalytic Gas-Phase Reactions

Reactors for catalytic gas phase processes

Reactors three phase catalytic

Single-phase catalytic microreactors

Three-Phase Catalytic Membrane Reactors

Three-phase Catalytic Reactions (G-L-S)

Three-phase Catalytic Reactors for Fine-chemicals Production

Three-phase catalytic reactors continuous

Three-phase catalytic reactors reactor efficiency

Two-Phase Catalytic Reactors

Two-Phase Fixed Bed Catalytic Reactors with

Vapor-phase catalytic hydrogenation, aniline

Vapor-phase catalytic hydrogenation, aniline manufacture

Yield, phase transfer catalytic reactions

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