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Catalytic conditioning

On metals in particular, the dependence of the radiation absorption by surface species on the orientation of the electrical vector can be fiilly exploited by using one of the several polarization techniques developed over the past few decades [27, 28, 29 and 30], The idea behind all those approaches is to acquire the p-to-s polarized light intensity ratio during each single IR interferometer scan since the adsorbate only absorbs the p-polarized component, that spectral ratio provides absorbance infonnation for the surface species exclusively. Polarization-modulation mediods provide the added advantage of being able to discriminate between the signals due to adsorbates and those from gas or liquid molecules. Thanks to this, RAIRS data on species chemisorbed on metals have been successfidly acquired in situ under catalytic conditions [31], and even in electrochemical cells [32]. [Pg.1782]

Reduction of metal oxides with hydrogen is of interest in the metals refining industry (94,95) (see Metallurgy). Hydrogen is also used to reduce sulfites to sulfides in one step in the removal of SO2 pollutants (see Airpollution) (96). Hydrogen reacts directiy with SO2 under catalytic conditions to produce elemental sulfur and H2S (97—98). Under certain conditions, hydrogen reacts with nitric oxide, an atmospheric poUutant and contributor to photochemical smog, to produce N2 ... [Pg.416]

A convenient synthesis of organochlorosilanes from organosilanes is achieved by reaction with inorganic chlorides of Hg, Pt, V, Cr, Mo, Pd, Se, Bi, Fe, Sn, Cu, and even C. The last compounds, tin tetrachloride, copper(II) chloride, and, under catalytic conditions, carbon tetrachloride (117,118), are most widely used. [Pg.27]

The process can be modified to give predominandy or solely /-butyl alcohol. Thus, /-butyl hydroperoxide (and /-butyl alcohol) produced by oxidation of isobutane in the first step of the process can be decomposed under controlled, catalytic conditions to give gasoline grade /-butyl alcohol (GTBA) in high selectivity (19—22). [Pg.357]

In the following reaction under phase catalytic conditions... [Pg.187]

Hydrochlorination of Ethylene. The exothermic vapor-phase reaction between ethylene [74-85-1] and hydrogen chloride [7647-01-0] can be carried out at 130—250°C under a variety of catalytic conditions. Yields are reported to be greater than 90% of theoretical (14). [Pg.2]

Hydrogen cyanide adds to an olefinic double bond most readily when an adjacent activating group is present in the molecule, eg, carbonyl or cyano groups. In these cases, a Michael addition proceeds readily under basic catalysis, as with acrylonitrile (qv) to yield succinonitnle [110-61-2], C4H4N2, iu high yield (13). Formation of acrylonitrile by addition across the acetylenic bond can be accompHshed under catalytic conditions (see Acetylene-DERIVED chemicals). [Pg.376]

Direct halogenation of quinoxaline appears to be of limited value but pyrazine may be chlorinated in the vapor phase to give monochloropyrazine at 400 °C or at lower temperatures under catalytic conditions 72AHC(14)99, and at higher temperatures tetra-chloropyrazine formation occurs in high yields. Mention has already been made of direct chlorination (see Section 2.14.2.1) of phenazine. [Pg.176]

Advantages of the in situ generation include ease of isolation and ee upgrades of crystalline products. Table 1.6.1 shows the beneficial effect of performing the AE reaction under catalytic conditions as well as in situ derivatization. [Pg.54]

It has been proposed that protonation or complex formation at the 2-nitrogen atom of 14 would enhance the polarization of the r,6 -7i system and facilitate the rearrangement leading to new C-C bond formation. The equilibrium between the arylhydrazone and its ene-hydrazine tautomer is continuously promoted to the right by the irreversible rearomatization in stage II of the process. The indolization of arylhydrazones on heating in the presence of (or absence of) solvent under non-catalytic conditions can be rationalized by the formation of the transient intermediate 14 (R = H). Under these thermal conditions, the equilibrium is continuously pushed to the right in favor of indole formation. Some commonly used catalysts in this process are summarized in Table 3.4.1. [Pg.118]

Since the revised Biginelli mechanism was reported in 1997, numerous papers have appeared addressing improvements and variations of this reaction. The improvements include Lewis acid catalysis, protic acid catalysis, non-catalytic conditions, and heterogeneous catalysis. In addition, microwave irradiation (MWI) has been exploited to increase the reaction rates and yields. [Pg.511]

Many transition metal-catalyzed reactions have already been studied in ionic liquids. In several cases, significant differences in activity and selectivity from their counterparts in conventional organic media have been observed (see Section 5.2.4). However, almost all attempts so far to explain the special reactivity of catalysts in ionic liquids have been based on product analysis. Even if it is correct to argue that a catalyst is more active because it produces more product, this is not the type of explanation that can help in the development of a more general understanding of what happens to a transition metal complex under catalytic conditions in a certain ionic liquid. Clearly, much more spectroscopic and analytical work is needed to provide better understanding of the nature of an active catalytic species in ionic liquids and to explain some of the observed ionic liquid effects on a rational, molecular level. [Pg.226]

Ethylene can be oxidized to a variety of useful chemicals. The oxidation products depend primarily on the catalyst used and the reaction conditions. Ethylene oxide is the most important oxidation product of ethylene. Acetaldehyde and vinyl acetate are also oxidation products obtained from ethylene under special catalytic conditions. [Pg.189]

The reason for the decrease in the enantiomeric excess observed in changing from stoichiometric to catalytic conditions was demonstrated to be due to a second catalytic cycle in which the chiral... [Pg.681]

The catalytic conditions (aqueous concentrated sodium hydroxide and tetraalkylammonium catalyst) are very useful in generating dihalo-carbenes from the corresponding haloforms. Dichlorocarbene thus generated reacts with alkenes to give high yields of dichlorocyclopropane derivatives,16 even in cases where other methods have failed,17 and with some hydrocarbons to yield dicholromethyl derivatives.18 Similar conditions are suited for the formation and reactions of dibromocar-benc,19 bromofluoro- and chlorofluorocarbene,20 and chlorothiophenoxy carbene,21 as well as the Michael addition of trichloromethyl carbanion to unsaturated nitriles, esters, and sulfones.22... [Pg.93]

The Ziegler process produces linear alcohols with an even number of carbon atoms and is based on the polymerization of ethylene under catalytic conditions, generally with triethylaluminum as in the Alfol and the Ethyl processes. The distribution of alkyl chains depends on the version of the process employed but the alcohols obtained after fractionation can be equivalent to those obtained from fats and oils or have purpose-made distributions depending on the fractionation conditions. [Pg.225]

Table I. Attempts to Prepare Hexachlorodibenzo- -dioxins Under Catalytic Conditions"... Table I. Attempts to Prepare Hexachlorodibenzo- -dioxins Under Catalytic Conditions"...
The use of excess lithium LiDBB in reductive lithiations is a drawback for preparative-scale reactions. A modification of Yus procedure [72, 73] allowed for the generation of a-alkoxylithium reagents under catalytic conditions [45] (Scheme 35). Slow addition of the phenyl sulfide 185 to a suspension of lithium... [Pg.87]

Table 1 shows a summary of the apparent activation energies for various catalytic conditions. The apparent activation energy of HDPE mixed with pure MCM-41 is significantly lower than that of HDPE only, indicating that pure MCM-41 is likely to demonstrate catalytic activity. As the A1 content increased, the apparent activation energy significantly decreased. Al-MCM-41-P demonstrated activation energies lower than those demonstrated by Al-MCM-41 -D at the same Si/Al. [Pg.439]

Catalytic conditions described in footnote d, but the poison (Hg or CS2) was added after 3.75 h of reaction. [Pg.434]

Entries 6 to 9 involve reactions conducted under catalytic conditions. Entry 6 uses a lanthanide catalyst that is active in aqueous solution. Entries 7 and 8 are examples of the use of (Cp)2Ti(03SCF3)2 as a Lewis acid. Entry 9 illustrates the TMS triflate-MABR catalytic combination. [Pg.86]

B, the initial rate constants are diminished, in contrast to those observed for the catalytic system (61). The reasons for the different effects of protein B on the two reactions with Hox are unknown. With Hox from M. capsulatus (Bath), activities of only —10% of the values observed under optimal catalytic conditions were found with the H202 shunt pathway, assuming specific activities to be greater than 200 mU/mg (59). As a consequence of the poor yields observed, the effect of protein B on the system was not investigated further. [Pg.272]

Figure 7.6 STM images (100 x 100) A2 of Pt(lll) under different catalytic conditions 7 (a) 20 mTorr H2 (b) 20mTorr H2 and 20mTorr C2H4 (c) 20mTorr H2 plus 20mTorr C2H4 and 2.5mTorr CO(g). The CO added induced the formation of a ( /l9 x /l9) R23.4° structure in (c). In (d) are shown two rotational domains of the /T9 structure. (Reproduced from Ref. 7). Figure 7.6 STM images (100 x 100) A2 of Pt(lll) under different catalytic conditions 7 (a) 20 mTorr H2 (b) 20mTorr H2 and 20mTorr C2H4 (c) 20mTorr H2 plus 20mTorr C2H4 and 2.5mTorr CO(g). The CO added induced the formation of a ( /l9 x /l9) R23.4° structure in (c). In (d) are shown two rotational domains of the /T9 structure. (Reproduced from Ref. 7).

See other pages where Catalytic conditioning is mentioned: [Pg.26]    [Pg.482]    [Pg.188]    [Pg.269]    [Pg.195]    [Pg.311]    [Pg.689]    [Pg.226]    [Pg.46]    [Pg.128]    [Pg.61]    [Pg.81]    [Pg.431]    [Pg.481]    [Pg.294]    [Pg.305]    [Pg.32]    [Pg.211]    [Pg.214]    [Pg.230]    [Pg.304]    [Pg.304]    [Pg.306]    [Pg.311]    [Pg.689]    [Pg.693]    [Pg.121]    [Pg.8]   
See also in sourсe #XX -- [ Pg.352 ]




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Catalytic conditions

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