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Alcohol dehydration model

Numerous applications of this theory have been made in calculating confidence intervals for parameter estimates in nonlinear kinetic models, such as typified in Table III (P2). The use of confidence regions is typified in Fig. 13 (M7) for the alcohol dehydration model... [Pg.128]

The transformation of a cyclopentanol/cyclohexanone mixture allows us to estimate simultaneously the acidity and the basicity of catalysts. Two reactions take place the hydrogen transfer (HT) on basic sites and the alcohol dehydration (DEH) on acid sites. This reaction was carried out at two temperatures over four aluminas. Theta alumina seems to be the most basic of the aluminas tested. Correlation between model reaction and IR study were also discussed. [Pg.221]

If the nonlinear estimation procedure is carefully applied, a minimum in the sums-of-squares surface can usually be achieved. However, because of the fitting flexibility generally obtainable with these nonlinear models, it is seldom advantageous to fit a large number of models to a set of data and to try to eliminate inadequate models on the basis of lack of fit (see Section IV). For example, thirty models were fitted to the alcohol dehydration data just discussed (K2). As is evident from the residual mean squares of Table II, approximately two-thirds of the models exhibit an acceptable fit of the data... [Pg.118]

Consider again the 500°F data for the alcohol dehydration just discussed. Equations (84)—(88) arose from Eq. (80). A similar set of equations can be generated from Eq. (81) (K5). Let us examine the two models through an analysis of their intrinsic parameters. [Pg.146]

Let us consider the data taken by Laible (LI) on the dehydration of normal hexyl alcohol at 450°F over a silica alumina catalyst. The single- and dualsite surface reaction controlled models applying to alcohol dehydration were discussed in Section V,A,2. We now consider, however, the functional forms given, for example, by Eq. (84), as probably being capable of describing the data, but do not restrict the Ct and C2 plots to a linear pressure dependence as before. Rather, we obtain an empirical pressure dependence from the... [Pg.166]

Different approaches to the kinetics of alcohol dehydration were attempted by two groups of authors [118,119]. In one case, it has been assumed that the active surface of alumina is formed either by free hydroxyl groups or by surface alkoxyl groups. The rate equation was then derived on the basis of the steady-state assumption a good fit to the experimental data was obtained [1118]. The second model was based on the fact that water influences the adsorption of an alcohol and diminishes the available surface. The surface concentrations of tert-butanol and water were taken from independent adsorption measurements and put into the first-order rate equation a good description of integral conversion data was achieved [119]. [Pg.285]

Figure 1.7 Typical zero-order and corresponding second-derivative electronic absorption spectra of ethanol-reconstituted lipid/chloroform extracts of autoxidized model polyunsaturated fatty-acid compounds and inflammatory synovial fluid obtained after (1) reduction with NaBH4 and (2) dehydration with alcoholic H2S04- (a) Methyl linoleate subsequent to autoxidation in air at ambient temperature for a period of 72 h (—), or exposure to a Fenton reaction system containing EDTA (5.75 x 10 mol/dm ), H2O2 (1.14 X 10 mol/dm ) and Fe(ll) (5.75 x IO mol/dm ) as an aqueous suspension (—) (b) as (a) but with methyl linolenate (c) untreated rheumatoid knee-joint synovial fluid. Figure 1.7 Typical zero-order and corresponding second-derivative electronic absorption spectra of ethanol-reconstituted lipid/chloroform extracts of autoxidized model polyunsaturated fatty-acid compounds and inflammatory synovial fluid obtained after (1) reduction with NaBH4 and (2) dehydration with alcoholic H2S04- (a) Methyl linoleate subsequent to autoxidation in air at ambient temperature for a period of 72 h (—), or exposure to a Fenton reaction system containing EDTA (5.75 x 10 mol/dm ), H2O2 (1.14 X 10 mol/dm ) and Fe(ll) (5.75 x IO mol/dm ) as an aqueous suspension (—) (b) as (a) but with methyl linolenate (c) untreated rheumatoid knee-joint synovial fluid.
This method has been applied (M5) for modeling the vapor-phase rate of dehydration of secondary butyl alcohol to the olefin over a commercial silica-alumina cracking catalyst. Integral reactor data are available at 400, 450, and 500°F. Two models considered for describing this reaction are the single site... [Pg.143]

When any hyperbolic model is written in terms of fractional conversions instead of partial pressures, two groupings of terms inherently arise within the denominator These two groupings will be called the intrinsic parameters Cx and C2. For example, when data are taken for the olefinic dehydration of a pure alcohol feed to a reactor, Eq. (80) becomes... [Pg.145]

An exhaustive review of dehydration reactions has been written recently by Winfield (3) and most of the relevant literature can be found there. The purpose of this chapter is to review some recent developments and to point out the resemblance of alumina-catalyzed dehydration of alcohols to solvolytic reactions. It will be demonstrated that by careful selection of model compounds, such as olefins and alcohols, it is possible to throw light on the catalytic action of alumina and to reveal the presence of active catalytic sites. [Pg.50]

The structure effects on rate in the catalytic dehydration of alcohols on acidic catalysts also have been elucidated by quantum-chemical modeling of the adsorption complex in a series of alcohols R CH(OH)-CH3, using a proton as a simple model of the catalyst 69). It has been found that the protonation of the hydroxyl group causes an increasing weakening of the C—O bond in the order R = CHj, C2H5, /-C3H7, This corresponds... [Pg.169]

These relations seem to be valid for the dehydration of primary alcohols, but secondary and tertiary alcohols may need other combinations of acidic and basic sites. It has been observed that the dehydration of tert-butanol was more sensitive to the presence of strongly acidic sites than the reaction of methanol, but both processes required basic sites [8]. All this is in accordance with the dynamic model of elimination mechanisms presented in Sect. 2.1, which allows transition from El to E2 or further to ElcB according to the structure of the reactant and the nature of the catalyst. [Pg.294]

Reactions studied include dehydrations of alcohols, double bond shifts in olefins, isomerization of hydrocarbons, racemization of optically active compounds, etc.. In the literature a rather rigid separation is made between a Brested acid, which is actually a proton donor, and a Lewis acid, which works as a hydride abstractor. We may illustrate this difference by using the double bond shift in olefins as the model reaction. [Pg.2]

Use of Model Alcohols in Mechanistic Studies. - Much use has been made of model alcohols of various types in order to elucidate the detailed mechanism of dehydration, and in so doing, most catalysts have been compared with either alumina or thoria representing respectively E1/E2 and ElcB mechanisms. [Pg.155]

Thomke has used model alcohols very effectively in his studies of dehydration mechanisms. For several oxides including thoria a number of deuteriated butanols were employed including d,l erthro(threo)-[3- Y i -butan-2-ol(a), [l,l,l,2,3,3- H6]butan-2-ol (b), and [2- Hi]butan-2-ol (c). [Pg.159]

It has been shown by quantum mechanical modelling, that in dehydration the alcohol is activated by interaction of the oxygen atom with the electrophilic species, namely a proton, and that the most activated of the /3-hydrogens is that which is awft -periplanar with respect to the hydroxyl-group. ... [Pg.160]

Siddan and Narayan also employed 7-AI2O3 and Th02 for the dehydration of a number of model alcohols and observed that if the basicity of the alumina was increased by Na -ion doping, 7-elimination was enhanced using both neopentyl and pinacolyl alcohol. It appeared that as the alumina became less acidic and more basic, there was a shift from El/E2-like behaviour to an ElcB-type mechanism, which manifested itself in a concerted 7-elimination (Scheme 10 for neopentyl alcohol A,B = acid, base sites respectively reproduced by permission from J. Catal, 1979, 59, 405). This tendency was also observed by use of erythrof f/ireo)-3-methylpentan-2-ol. [Pg.161]


See other pages where Alcohol dehydration model is mentioned: [Pg.118]    [Pg.811]    [Pg.341]    [Pg.126]    [Pg.187]    [Pg.156]    [Pg.403]    [Pg.268]    [Pg.130]    [Pg.1128]    [Pg.1060]    [Pg.283]    [Pg.210]    [Pg.379]    [Pg.145]    [Pg.150]    [Pg.7]    [Pg.288]    [Pg.2913]    [Pg.306]    [Pg.141]    [Pg.164]    [Pg.156]    [Pg.904]    [Pg.533]   
See also in sourсe #XX -- [ Pg.107 ]




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