Liquid selective oxidation

Leclerc, A, Alame, M., Schweich, D., Pouteau, P., Delattre, C., and de Bellefon, C. (2008) Gas-liquid selective oxidations with oxygen under explosive conditions in a micro-structured reactor. Lab Chip, 8 (5), 814-817. 

Gas-liquid selective oxidations with oxygen under explosive conditions in a micro-structured reactor. Lab Chip, 8 (5), 814-817. 

Ethylbenzene Hydroperoxide Process. Figure 4 shows the process flow sheet for production of propylene oxide and styrene via the use of ethylbenzene hydroperoxide (EBHP). Liquid-phase oxidation of ethylbenzene with air or oxygen occurs at 206—275 kPa (30—40 psia) and 140—150°C, and 2—2.5 h are required for a 10—15% conversion to the hydroperoxide. Recycle of an inert gas, such as nitrogen, is used to control reactor temperature. Impurities ia the ethylbenzene, such as water, are controlled to minimize decomposition of the hydroperoxide product and are sometimes added to enhance product formation. Selectivity to by-products include 8—10% acetophenone, 5—7% 1-phenylethanol, and <1% organic acids. EBHP is concentrated to 30—35% by distillation. The overhead ethylbenzene is recycled back to the oxidation reactor (170—172). 

It was quite recently reported that La can be electrodeposited from chloroaluminate ionic liquids [25]. Whereas only AlLa alloys can be obtained from the pure liquid, the addition of excess LiCl and small quantities of thionyl chloride (SOCI2) to a LaCl3-sat-urated melt allows the deposition of elemental La, but the electrodissolution seems to be somewhat Idnetically hindered. This result could perhaps be interesting for coating purposes, as elemental La can normally only be deposited in high-temperature molten salts, which require much more difficult experimental or technical conditions. Furthermore, La and Ce electrodeposition would be important, as their oxides have interesting catalytic activity as, for instance, oxidation catalysts. A controlled deposition of thin metal layers followed by selective oxidation could perhaps produce cat-alytically active thin layers interesting for fuel cells or waste gas treatment. 

Volume 16 Volume 1 7 Liquid-phase Oxidation Gas-phase Combustion Section 7. SELECTED ELEMENTARY REACTIONS (1 volume)... 

Liquid phase oxidation reaction of acetaldehyde with Mn acetate catalyst can be considered as pseudo first order irreversible reaction with respect to oxygen, and the reaction occurred in liquid film. The value of kinetic constant as follow k/ = 6.64.10 exp(-12709/RT), k2 = 244.17 exp(-1.8/RT) and Lj = 3.11.10 exp(-13639/RT) m. kmor. s. The conversion can be increased by increasing gas flow rate and temperature, however the effect of impeller rotation on the conversion is not significant. The highest conversion 32.5% was obtained at the rotation speed of 900 rpm, temperature 55 C, and gas flow rate 10" m. s. The selectivity of acetic acid was affected by impeller rotation speed, gas flow rate and temperature. The highest selectivity of acetic acid was 70.5% at 500 rpm rotation speed, temperature of 55 C... 

Beside their use in equilibrium-restricted reactions, CMRs have been also proposed for very different applications [6], like selective oxidation and oxidative dehydrogenation of hydrocarbons they may also act as active contactor in gas or gas-liquid reactions. 

There is not much to be said about the use of micro reactors for bulk chemicals and commodities. Worz et al. are so far the only ones who have disclosed their work on the potential of micro-structured reactors for the optimization of chemical processes performed on a large scale ofindustrial relevance [110,112,154,288-290]. This included a fast exothermic liquid/liquid two-phase reaction, which was used for the industrial production of a vitamin intermediate product, and a selective oxidation reaction for an intermediate, a substituted formaldehyde derivative. 

The liquid-phase oxidation of glycerol was carried out by using carbon-supported gold particles of different sizes (2.7 2 nm) which were prepared by a colloidal route [120]. Indeed, a particle-size effect was observed because the selectivity to glyceric acid was increased to 75% with smaller particle sizes (4)ptmimn = 3.7 nm). 

Figure 31 shows that among metal oxide supports, TOF markedly changes depending on not only the kind of metal oxides but also on their size [98]. Especially, fine particles of Ce02 with mean diameter of 5 nm present the highest catalytic activity. On the other hand, Prati and her coworkers [31] reported that gold NPs supported on activated carbons are very active and selective in the liquid phase oxidation of various alcohols. 

Au/C was established to be a good candidate for selective oxidation carried out in liquid phase showing a higher resistance to poisoning with respect to classical Pd-or Pt-based catalysts [40]. The reaction pathway for glycerol oxidation (Scheme 1) is complicated as consecutive or parallel reactions could take place. Moreover, in the presence of a base interconversion between different products through keto-enolic equilibria could be possible. 

The TS-1 catalysed hydroxylation of phenol to a 1 1 mixture of catechol and hydroquinone (Fig. 2.16) was commercialized by Enichem (Romano et ai, 1990). This process offers definite advantages, such as higher selectivities at higher phenol conversions, compared to other catalytic systems. It also illustrates another interesting development the use of solid, recyclable catalysts for liquid phase (oxidation) processes to minimize waste production even further. 

One of the exciting results to come out of heterogeneous catalysis research since the early 1980s is the discovery and development of catalysts that employ hydrogen peroxide to selectively oxidize organic compounds at low temperatures in the liquid phase. These catalysts are based on titanium, and the important discovery was a way to isolate titanium in framework locations of the inner cavities of zeolites (molecular sieves). Thus, mild oxidations may be run in water or water-soluble solvents. Practicing organic chemists now have a way to catalytically oxidize benzene to phenols alkanes to alcohols and ketones primary alcohols to aldehydes, acids, esters, and acetals secondary alcohols to ketones primary amines to oximes secondary amines to hydroxyl-amines and tertiary amines to amine oxides. 

Chelation of zeolite Mn2+ by N-containing ligands gives rise to good heterogeneous liquid-phase oxidation catalysts. Mn(lI)Salen Y catalyzes the selective... 

AM Ivanov. Role of Aldehydes in Selective Liquid-Phase Oxidation of Alkylaromatic Compounds and Oils. Thesis Dissertation, LPI, Leningrad, 1980 [in Russian],... 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

The activity of elemental carbon as a metal-free catalyst is well established for a couple of reactions, however, most literature still deals with the support properties of this material. The discovery of nanostructured carbons in most cases led to an increased performance for the abovementioned reasons, thus these systems attracted remarkable research interest within the last years. The most prominent reaction is the oxidative dehydrogenation (ODH) of ethylbenzene and other hydrocarbons in the gas phase, which will be introduced in a separate chapter. The conversion of alcohols as well as the catalytic properties of graphene oxide for liquid phase selective oxidations will also be discussed in more detail. The third section reviews individually reported catalytic effects of nanocarbons in organic reactions, as well as selected inorganic reactions. 

L. Prati and M. Rossi, Gold on carbon as a new catalyst for selective liquid phase oxidation of diols, J. Catal. 176(2), 552-560 (1998). 

C. Bianchi, F. Porta, L. Prati, and M. Rossi, Selective liquid phase oxidation using gold catalysts. Top. Catal. 13(3), 231-236 (2000). 

The heme enzyme chloroperoxidase (CPO), produced by the marine fungus Caldariomycesfumago, is a versatile enzyme which exhibits a broad spectrum of chemical reactivities and it is recognized as a most promising biocatalyst for synthetic applications. Recently, pure (R)-phenyl methylsulfoxide (ee > 99 %) was prepared by chemo- and stereo-selective oxidation of phenyl methylsulfide with CPO in citrate buffer-ionic liquid mixtures. ... 

Etard reagents (chromyl chloride and some derivatives) suffer from the problem that occasionally they can exhibit a lack of selectivity and low yields. They are useful in the selective oxidation of aromatic side-chains to a carbonyl group, aldehyde or ketone but in many instances, the formation of the initial complex is slow and yields are low because of difficulties in the work-up which lead to undesired over-reaction. Attempts have been made to solve the problems by the use of sonication [134]. A simple preparation of the liquid reagent was proposed and the Etard reaction itself together with the hydrolytic step were conducted under sonication, with some success (Scheme 3.25). 

Supported Polyoxometalate-Based Heterogeneous Catalysis for Liquid Phase Selective Oxidations... 

Polyoxometalates undoubtedly have enormous catalytic potential in liquid phase selective oxidation of organic compounds. Various strategies for immobilization of POMs on solid matrices have been developed during the past two decades and opened new opportunities for practical applications. The most developed and widely used technique is electrostatic... 

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