ion from a primary OH group of glyc-erol. 223,231 A similar mechanism was proposed manyyears ago for alcohol oxidation on Pt/C, involving asecond step, the transfer of a hydride ion to the Ptsurface (Scheme 11). 8,87,237 We consider it more feasible that the rate-deter-mining step is the cleavage of the C-H bond at theR-carbon atom. A similar mechanism is now generallyaccepted for Au electrodes (Scheme 12). 238 Despite thestructural differences between Au nanoparticles andan extended Au electrode surface, there are alsosimilarities, such as the critical role of aqueousalkaline medium and the absence of deactivation dueto decomposition products (CO and C x H y frag-ments). 239,240 An important question is the nature of active siteson Au nanoparticles. Electrooxidation of ethanol onAu nanoparticles supported on glassy carbon re-quired the partial coverage of Au surface by oxides. 241 Another analogy might be the model proposed for COoxidation. 219,242,243 According to this suggestion, theactive site consists of an ensemble of metallic Auatoms and a cationic Au

Oxidation of Alcohols with Molecular Oxygen on Solid Catalysts

It is well known that urbanization and industrialization have resulted in the rapidly increasing emissions of volatile organic compounds (VOCs), which are a major contributor to the formation of secondary pollutants (e.g., tropospheric ozone, PAN (peroxyacetyl nitrate), and secondary organic aerosols) and photochemical smog. The emission of these pollutants has led to a large decline in air quality in numerous regions around the world, which has ultimately led to concerns regarding their impact on human health and general well-being. Catalytic oxidation is regarded as one of the most promising strategies for VOC removal from industrial waste streams. This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades. It addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions. It also highlights the primary routes for catalyst deactivation and discusses protocols for their subsequent reactivation. Kinetic models and proposed oxidation mechanisms for representative VOCs are also provided. Typical catalytic reactors and oxidizers for industrial VOC destruction are further discussed. We believe that this Review will provide a great foundation and reference point for future design and development in this field.

/pdf/recent-advances-in-the-catalytic-oxidation-of-volatile-zw2c35dbg7.pdf

Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources.

State of the art and future challenges of zeolites as catalysts

E factors, green chemistry and catalysis: an odyssey

Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

/pdf/surface-chemistry-and-spectroscopy-of-chromium-in-inorganic-5dnw014r22.pdf

Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides.

In a process for oxidizing a hydrocarbon to the corresponding hydroperoxide, alcohol, ketone, carboxylic acid or dicarboxylic acid, a reaction medium comprising a hydrocarbon is contacted with an oxygen-containing gas in a reaction zone and in the presence of a catalyst comprising a cyclic imide. During the oxidation process, a portion of the reaction medium is continuously or intermittently removed from the reaction zone, is stripped of water and organic acid impurities and then returned to the reaction zone.

Oxidation of Hydrocarbons

The liquid phase ammoximation of cyclohexanone, ortho and para -hydroxyacetophenones (2-HAP and 4-HAP) with ammonia and hydrogen peroxide was investigated over titanium-silicalite-1 (TS-1), titanium-aluminum-beta (TiAl-Beta) and Ti-ZSM-48. The ammoximation of 4-HAP over TS-1 gave the corresponding oxime in 100% selectivity at 50% 4-HAP conversion. Under similar conditions, TiAl-Beta gave the oxime in 80% selectivity at 30% 4-HAP conversion. Ti-ZSM-48 afforded 17% 4-HAP conversion and 67% 4-HAP oxime selectivity. The ammoximation of 2-HAP occurred with 80% yield over TS-1 and with 40% yield over TiAl-Beta. Methanol as solvent and large excess of ammonia are preferred to perform ammoximation on TiAl-Beta.

Ammoximation of cyclohexanone and hydroxyaromatic ketones over titanium molecular sieves

http://iglesia.cchem.berkeley.edu/Publications/JournalofCatalysis_239_390_2006.pdf

Kinetics and mechanism of cyclohexane oxidation on MnAPO-5 catalysts ✩

energy occurred concurrently and at similar rates, indicating excellent agreement between these techniques. No H2 Oo r CO 2 were detected during treatment in H2 or CO, respectively, indicating that reduction from Me 3+ to Me 2+ occurred by introduction of protons. These protons are fully removed by treatment in O2 to 773 K, and O2-H2 redox cycles involving reversible proton formation suggest that cations reside within AlPO framework positions, in which protons reside as charge balancing cations at Me 2+ -O-P bridges. H2 consumption rates measured during H2-TPR could be accurately described by Arrhenius-type behavior, and H2/Me ratios showed that only a fraction of all Me cations undergo reversible redox cycles. This fraction was 0.86 for MnAPO-18 (atomic Mn/P ) 0.05); it decreased from 0.68 to 0.40 for MnAPO-5 as Mn/P ratios increased from 0.028 to 0.10. For CoAPO-18 with 0.028 Co/P and CoAPO-5 with 0.40 Co/P, the fractions of redox sites were 0.64 and 0.40, respectively. UV-visible spectra showed no detectable Me 3+ features after thermal treatment in H2. Thus, cations that do not undergo redox cycles remain as permanently divalent cations throughout O2-H2 cycles. The redox-active fraction also decreased during repeated H 2-O2 redox cycles above 773 K, indicating that redox cations convert into permanently divalent sites. This conversion coincides with the evolution of H2O during H2 treatments above 773 K. These findings together with the effects of Me/P ratio on the redox fraction are consistent with a mechanism in which OH groups at divalent framework cation sites recombine to form H2O and an oxygen vacancy. Cyclohexanol and cyclohexanone formation rates during liquid-phase cyclohexane oxidation with O2 on MnAPO-5 samples increased linearly with the number of redox-active sites, suggesting that elementary steps of cyclohexane oxidation involve cycling between Me 2+ and Me 3+ , and require cation sites able to reversibly form charge balancing cationic species.

/pdf/structural-and-functional-characterization-of-redox-mn-and-23b8imcs7x.pdf

Structural and functional characterization of redox Mn and Co sites in AlPO materials and their role in alkane oxidation catalysis

http://iglesia.cchem.berkeley.edu/publications/journalofcatalysis_245_316_2007.pdf

Jihad M. Dakka

Papers

Oxidation of Hydrocarbons

Ammoximation of cyclohexanone and hydroxyaromatic ketones over titanium molecular sieves

Kinetics and mechanism of cyclohexane oxidation on MnAPO-5 catalysts ✩

Structural and functional characterization of redox Mn and Co sites in AlPO materials and their role in alkane oxidation catalysis

Catalytic oxidation of n-hexane on Mn-exchanged zeolites: Turnover rates, regioselectivity, and spatial constraints