Paraffins liquid phase oxidations

Many other metal ions have been reported as catalysts for oxidations of paraffins or intermediates. Some of the more frequently mentioned ones include cerium, vanadium, molybdenum, nickel, titanium, and ruthenium [21, 77, 105, 106]. These are employed singly or in various combinations, including combinations with cobalt and/or manganese. Activators such as aldehydes or ketones are frequently used. The oxo forms of vanadium and molybdenum may very well have the heterolytic oxidation capability to catalyze the conversion of alcohols or hydroperoxides to carbonyl compounds (see the discussion of chromium, above). There is reported evidence that Ce can oxidize carbonyl compounds via an enol mechanism [107] (see discussion of manganese, above). Although little is reported about the effectiveness of these other catalysts for oxidation of paraffins to acetic acid, tests conducted by Hoechst Celanese have indicated that cerium salts are usable catalysts in liquid-phase oxidation of butane [108]. 

On the one hand, hydrocarbon oxidation is a model reaction which enables special features of these catalytic processes to be analyzed. In addition, this resembles, to a considerable extent, enzymatic catalysis it also proceeds at low temperatures with high selectivity and requires small quantities of catalyst [128]. There have been no systematic investigations of catalytic liquid-phase oxidation of paraffins by macromolecular complexes and the scarce data are presented mainly in patents. (Pd complexes bound to ion-exchange resins are highly active in hydrogen oxidation by air (see, for instance [129])). 

Among such oxidations, note that liquid-phase oxidations of solid paraffins in the presence of heterogeneous and colloidal forms of manganese are accompanied by a substantial increase (compared with homogeneous catalysis) in acid yield [3]. The effectiveness of n-paraffin oxidations by Co(III) macrocomplexes is high, but the selectivity is low the ratio between fatty acids, esters, ketones and alcohols is 3 3 3 1. Liquid-phase oxidations of paraffins proceed in the presence of Cu(II) and Mn(II) complexes boimd with copolymers of vinyl ether, P-pinene and maleic anhydride (Amberlite IRS-50) [130]. Oxidations of both linear and cyclic olefins have been studied more intensively. Oxidations of linear olefins proceed by a free-radical mechanism the accumulation of epoxides, ROOH, RCHO, ketones and RCOOH in the course of the reaction testifies to the chain character of these reactions. The main requirement for these processes is selectivity non-catalytic oxidation of propylene (at 423 K) results in the formation of more than 20 products. Acrylic acid is obtained by oxidation of propylene (in water at 338 K) in the presence of catalyst by two steps at first to acrolein, then to the acid with a selectivity up to 91%. Oxidation of ethylene by oxygen at 383 K in acetic acid in... 

In Japan, secondary alcohols for ethoxylation are also produced by Bashkirov oxidation of -paraffins (liquid phase, in the presence of boron oxides at around 160°C). Some ethoxylates are also sulphated, while olefins can be sulphonated with SO3 or converted to sodium alkanesulphonates directly by free-radical addition of sodium bisulphite ... 

It is also assumed that the oxidation of hydrocarbons is initiated by oxygen atoms formed by the thermal dissociation of a nitrogen oxide (NO) [3]. The use of gaseous initiation of liquid-phase oxidation of paraffins (127 "C), consisting of addition of NO to air at the beginning of the reaction, allows considerable shortening of the induction period for the oxidation [9], With a 30-minute initiation by air containing 0.35% NO, the induction period is 10 hours, as compared with 366 hours in the absence of the initiator. 

The paraffin wax is oxidized by air in a liquid phase process at 110-130°C. Catalysts for this radical reaction are cobalt or manganese salts [54]. The quality of the obtained mixture of homologous carboxylic acids is impaired by numerous byproducts such as aldehydes, ketones, lactones, esters, dicarboxylic acids, and other compounds. These are formed despite a partial conversion of the paraffin and necessitate an expensive workup of the reaction product [50,55]. 

Since previous papers (1, 2) describe details of the manufacturing process for secondary alcohols(SA) and their ethoxylates (SAE), only the outline of the process will be presented here. A mixture of secondary alcohols is obtained by liquid phase air-oxidation of normal paraffins in the presence of a boric acid catalyst(Figure 1). Although the existing commercial processes, as developed independently, comprise significantly different combinations of various unit processes, they are all based on this boric acid-modified oxidation of hydrocarbons(3). 

Solvent or fractional condensation methods, however, do not give complete separation from the anthracene of such substances as acridine, Ruorantln-enc, flnorene, pyrene, methyl-anthracene, chrysene, acenaphthene, high molecular weight paraffin hydrocarbons, etc., which are present in the crude anthracene press cake. During the subsequent oxidation of anthracene by the liquid phase method these substances result in the formation of impurities difficult to separate from the anthraquinoue and detracting considerably from its quality as a dye intermediate. 

Based on the experience of the I. G. Farbenindustrie with the liquid-phase catalyzed air oxidation of paraffin wax, a tentative scheme was proposed by KraucW for the oxidation mechanism. By this scheme, oxygen attacked the paraffin molecule toward the middle and not on the ends. This proposal was supported by the finding that a portion of the acids formed contains about half the number of carbon atoms as the original paraffin molecule and that the small amounts of carbon oxides and low-molecular-weight oxidation products preclude oxidation from one end of the large molecules to form the acids in the product. 

Scott [1,13], Hewett [14] and McKenna and Idleman [15] who modified aluminum oxide with silicone oil, liquid paraffin, and propylene carbonate were among the first to obtain positive results in separation improvement by adding stationary liquid phase to solid adsorbents. In all cases the separation of gases on a modified eiluminum oxide was more complete compared to separation on a non-modified sorbent. We note that the separation of C1-C4 gases on aluminum oxide F10 modified with propylene carbonate (21%) is sufficiently complete for all the compounds. Separation was carried out at 26 in a 9 m X 5 mm column filled with a modified adsorbent (fraction 60 to 90 mesh) [15]. The chromatogram (see Fig. 5-6) shows separation of C -C4 hydrocarbon gases. 

In typical slurry reactions like hydrogenations and oxidations the particle sizes are usually smaller than 200 yum and their concentration is less than 10 wt. percent. Under such conditions, the variations in k] a due to the presence of solids reported (31,69-72) do not commonly exceed 10 to 20 %. If the particles are small ( 50 pm) the suspended solid and the liquid behave as a pseudohomogeneous phase. This can be concluded from a study on the CO conversion reaction on a catalyst suspended in molten paraffin where no significant effect on and kj a could be observed (13,37). ... 

More than a century ago, Pickering [2] and Ramsden [3] investigated paraffin-water emulsions contains solid particles such as iron oxide, silicon dioxide, barium sulfate, and kaolin and discovered that these micron-sized colloids generate a resistant film at the interface between the two immiscible phases, inhibiting the coalescence of the emulsion drops. These so-called Pickering emulsions are formed by the self-assembly of colloidal particles at fluid-fluid interfaces in two-phase liquid systems (Fig. 1). 

One of the earliest separations in gas liquid chromatography was that of James et al. who used a mixture of hendecanol and liquid paraffin on celite using ammonia and the methyl amines as eluents in the order of their melting points. Other stationary phases used for this and for other similar separations include triethanolamine, a mixture of w-octadecane and n-hendecanol, and polyethylene oxide. Titration cell, the first detector designed specifically for gas chromatography, was used in these early studies of the separation of ammonia and ethylamines. More recently thermal conductivity cells have been used for the detection of these compounds. 

Stiff pastes usually are based on white soft paraffin. Sometimes a part of white soft paraffin is replaced by liquid paraffin to improve the applicability, as for example in zinc oxide pastes. Zinc oxide pastes contain wheat starch and zinc oxide as the solid phase. 

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