Maleic anhydride, from catalytic oxidation

Vanadium phosphorus oxides (VPO) are commercially used as catalysts for the s5mthesis of maleic anhydride from the partial oxidation of n-butane. The phase constitution and the morphology of the catalyst are found to be dependent on the preparation routes and the applied solvent [78]. Recently, a method to prepare VPO catalysts in aqueous solution at elevated temperature was reported [79]. In addition to the linear relationship between specific activity and surface area, a small group of catalysts exhibit enhanced activity, which could be due to the combination of a higher proportion of V phases in the bulk of vanadyl pyrophosphate (V0)2P207 catalyst [79, 80]. With high relevance to the catalytic properties, the microstructure characterisation of VPO therefore is of great importance. 

Other catalytic reactions carried out in fluidized-bed reactors are the oxidation of naphthalene to phthalic anhydride [2, 6, 80] the ammoxidation of isobutane to mcthacrylonitrilc [2] the synthesis of maleic anhydride from the naphtha cracker C4 fraction (Mitsubishi process [81, 82]) or from n-butane (ALMA process [83], [84]) the reaction of acetylene with acetic acid to vinyl acetate [2] the oxychlorination of ethylene to 1,2-di-chloroethane [2, 6, 85, 86] the chlorination of methane [2], the reaction of phenol with methanol to cresol and 2,6-xylenol [2, 87] the reaction of methanol to gasoline... 

A series of vanadium phosphate catalysts prepared by different routes and containing different phases were examined by Guliants and coworkers [23]. From this study it was concluded that the catalytically active phase is an active surface layer on VPP. Their experimental results showed VOPO4 phases to be detrimental to the performance of the catalyst. This was confirmed by Cavani and Trifiro, who suggested that V sites are responsible for the over-oxidation of maleic anhydride to carbon oxides [24]. 

We conclude therefore, that the Nb-Ti-V-P-oxide catalyst investigated is relatively active for the oxidation of paraffins, since it has a V/P ratio of only 1/12 as compared to a 1/1 ratio for (VO)2P207. Of course, we had hoped that the V in the NASICON structure would be sufficiently site isolated to yield products less oxidized than maleic anhydride from n-butane. However, unfortunately that does not appear to be the case. One explanation for this might be that there are still too many adjacent V atoms, i.e., (V-0-V) moieties, where n > 0. Nonetheless, the NASICON structure provides for some desired V site isolation, however, apparently not complete and hence not sufficient to achieve our desired catalytic goal. Another observed fact is, that the Nb-Ti-V-P-oxide under investigation shows an amorphous overlayer via TEM which is enriched in vanadium. The (V/P)s ,face > (V/P)pa icie- One can reason that at the temperature of 900 °C required to obtain the NASICON structure, the more... 

The V206-coated catalytic membrane was applied to the partial oxidation reaction to produce maleic anhydride from 1-butene. The maximum selectivity was 95% at 350 °C and the permeability of oxygen through the V20s-coated catalytic membrane was enhanced. More careful studies are needed about this permeability enhancement. 

Specifically excluded from this review are (1) industrial partial oxidation processes (e.g., maleic anhydride or ethylene oxide production), and (2) automotive catalytic oxidation. What principally distinguishes the catalytic oxidation processes considered herein from these two processes are (1) reactant (oxygen and hydrocarbon) concentration and pressure, and (2) temperature, respectively. 

The V-Mo-O oxides are well-known industrial catalysts for the synthesis of acrylic acid from acrolein and maleic anhydride from benzene more recently, V-P-0 systems are being utilized for maleic anhydride production from -butane. The V20s/Ti02 combination was employed for phthalic acid production from o-xylene. V-Fe-O catalyzes oxidation of polycyclic aromatic hydrocarbons to dicarboxylic acids and quinones. Methyl formate is produced by the oxidation of methanol over V-Ti-0 catalysts [58]. For many of these processes, it has been experimentally proved that the catalytic reaction follows a Mars-van Krevelen mechanism. The surface coverage with active oxygen 0 in the steady state of the redox reaction following Mars-van Krevelen mechanism is given by... 

Prior to 1975, benzene was catalytically oxidized to produce maleic anhydride, an intermediate in synthesis of polyester resins, lubricant additives, and agricultural chemicals. By 1986 all commercial maleic anhydride was derived from oxidation of / -butane. It is expected that / -butane will remain the feedstock of choice for both economic and environmental reasons. 

The production of acetic acid from n-butene mixture is a vapor-phase catalytic process. The oxidation reaction occurs at approximately 270°C over a titanium vanadate catalyst. A 70% acetic acid yield has been reported. The major by-products are carbon oxides (25%) and maleic anhydride (3%) ... 

For many years the catalytic air oxidation of benzene was the main source of maleic anhydride. Obviously, two carbons from each ring are wasted as carbon dioxide in this process. Although some is still made that way, most modem maleic anhydride plants are based on butane oxidation. Because butane is forecast to be plentiful and low-cost, new routes to four-carbon chemicals from maleic anhydride are under active development. 

V-P oxides are known to be efficient for the production of maleic anhydride (abbreviated as MA) from n-butane (1-3). A single-phase (VO2P2O7 has been inferred to be the active catalyst phase (4-6). In addition, the catalytic properties of (VO)2P207 varied depending on the microstructure of (VO)2P207 particles (7,8). Some claimed that the... 

Compound 87 (R = r-Bu, R = Ph, R = H) has been prepared by addition of tert-butylmagnesium chloride to 1-phenylphthalide (102) and subsequent dehydration with p-toluenesulfonic acid. It is described as a yellow oil with brilliant fluorescence under UV light, which on oxidation with sodium dichromate yields diketone 103. Compound 87 (R = /-Bu, R = Ph, R = H) with dimethyl acetylenedicarboxylategives 104(mp 128-129 C, 80%) on reduction 105 is obtained 105 is also accessible from 87 (R = <-Bu, R = Ph, R = H) and dimethyl maleate (mp 151-152°C, endo) a maleic anhydride adduct has also been described (mp 147.5-148°C, 83%). Diels-Alder adducts have been also prepared from the benzo[c]furan precursors 106 (R = CHjPh, R = H, Ph) in the presence of catalytic amounts of acid 107 (mp 141-142.5X, 70%) and 108 (mp 140-141.5°C, 49%) were obtained, which on catalytic hydrogenation (Pd/C) gave the exo isomers 109(110-1 irC) and 110(90-92°C, 125.5-127°C, dimorphism). The basis for these stereochemical assignments remains unclear, however. Compounds... 

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