Adsorption phenol hydrogenation

In the above equations the symbols A, B, C, D designate phenol, hydrogen, cyclohexanone and cyclohexanol. Table 5.7 presents the model parameters at 423 K and 1 atm. The model takes into account the effect of the products on the reaction rate in the region of higher conversion. This feature is particularly useful for describing the product distribution in consecutive catalytic-type reactions. Note that the adsorption coefficients are different in the two reactions. Following the authors, this assumption, physically unlikely, was considered only to increase the accuracy of modeling. 

Analytical methods used for determining DNOC in environmental samples are given in Table 6-2. Most of the methods for products, waters, soils, and sludges rely on extraction of DNOC from an acidified matrix acidification minimizes dissociation of the phenolic hydrogen and thus facilitates extraction into an organic solvent or adsorption onto a solid phase extraction medium. The influence of pH on the adsorption of DNOC to humic materials in coal waste waters has been studied (Porschmann and Stottmeister 1993) and significant adsorption was found to occur at pH 7 but not... 

EELS spectra of the adsorbed layers formed from HQ or BQ solutions were very similar [Figs. 42(a) and (b)], indicating formation of a common horizontally oriented adsorbed state. Also shown in Fig. 42 are the locations of the principal mid-IR bands of solid HQ and BQ. The virtual absence of the OH stretches (3260 cm1) from the EELS spectra of adsorbed layers formed at HQ concentrations below 1 mM indicates that the phenolic hydrogens are lost during adsorption [eqn. (33)]. 

Covering a supported metal catalyst with a thin liquid film that differs from the bulk solvent affects both the reaction rate and selectivityTreating a Pd/C catalyst with 2M KOH before using it in a phenol hydrogenation with a heptane solvent gave cyclohexanone in 97% yield. Apparently, the distribution of phenol and phenolate ions between the thin aqueous film around the catalyst and the bulk hydrocarbon solvent enhanced the adsorption of the phenolate ion on the catalyst and the facile transfer of the neutral cyclohexanone to the heptane after the selective hydrogenation was completed (Figure 17.1). 

Mahata, N.. and Vishwanathan, V., Dependency of phenol hydrogenation activity on hydrogen chemisorption over supported palladium catalysts, Adsorpt. Sci. Technol.. 15(3), 165-172 (1997). 

From the results of this kinetic study and from the values of the adsorption coefficients listed in Table IX, it can be judged that both reactions of crotonaldehyde as well as the reaction of butyraldehyde proceed on identical sites of the catalytic surface. The hydrogenation of crotyl alcohol and its isomerization, which follow different kinetics, most likely proceed on other sites of the surface. From the form of the integral experimental dependences in Fig. 9 it may be assumed, for similar reasons as in the hy-drodemethylation of xylenes (p. 31) or in the hydrogenation of phenol, that the adsorption or desorption of the reaction components are most likely faster processes than surface reactions. 

In contrast to the minimal activity in infrared reflection studies the technique of inelastic electron tunneling spectroscopy (IETS) recently has contributed a large amount of information on monolayer adsorption of organic molecules on smooth metal oxide surfaces,Q),aluminum oxide layers on evaporated aluminum. These results indicate that a variety of organic molecules with acidic hydrogens, such as carboxylic acids and phenols chemisorb on aluminum Oxide overlayers by proton dissociation - 1 — and that monolayer coverage can be attained quite repro-ducibly by solution doping techniques. - The IETS technique is sensitive to both infrared and Raman modes. — However, almost no examples exist in which Raman il and or infrared spectra have been taken for an adsorbate/substrate system for which IETS spectra have been observed. 

MWCNTs were functionalized with iron phthalocyanines (FePc) to improve the sensitivity towards hydrogen peroxide. A highly sensitive glucose sensor with an FePc-MWCNT electrode based on the immobilization of GOx on poly(o-amino-phenol) (POAP)-electropolymerized electrode surface [219]. A hemin-modified MWCNT electrode to be used as a novel 02 sensor was obtained by adsorption of hemin at MWCNTs and the electrochemical properties of the electrode were characterized by cyclic voltammetry [220]. 

Many substituted phenols have been electroreduced at Pt electrodes in ethanol-water mixtures [14] or in acid (0.05 M H2S04 or 2 M HC104) solutions [15], leading to cyclohexanols with a current efficiency close to 100%. The reaction appears to proceed via a surface process involving the adsorption of phenols and hydrogen atoms formed at the cathode. As cyclohexanols are biocompatible, these substituted phenols can be degraded by... 

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