Acetic anhydride Liquid phase process

Homogeneous catalysts. With a homogeneous catalyst, the reaction proceeds entirely in the vapor or liquid phase. The catalyst may modify the reaction mechanism by participation in the reaction but is regenerated in a subsequent step. The catalyst is then free to promote further reaction. An example of such a homogeneous catalytic reaction is the production of acetic anhydride. In the first stage of the process, acetic acid is pyrolyzed to ketene in the gas phase at TOO C ... 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

The Acetaldehyde Oxidation Process. Liquid-phase catalytic oxidation of acetaldehyde (qv) can be directed by appropriate catalysts, such as transition metal salts of cobalt or manganese, to produce anhydride (26). Either ethyl acetate or acetic acid may be used as reaction solvent. The reaction proceeds according to the sequence... 

The hydrogenation of acetic anhydride was also performed in the vapor phase over a supported palladium catalyst resulting in acetaldehyde and acetic acid in high yields (36). To avoid recycling, the reactor was designed for complete reaction of acetic anhydride. Minor selectivity loss was found in formation of ethyl acetate (0.5-1.5%) and methane (0.5%). Typical reaction conditions were 160-200 C, 30-100 psi, with a hydrogen-anhydride ratio of 3 1 to 10 1. A similar catalyst was used in the liquid phase (37). The simplicity and high selectivity of this process is certainly attractive. 

Catalytic oxidation is the most important technology for the conversion of hydrocarbon feedstocks (olefins, aromatics and alkanes) to a variety of bulk industrial chemicals.1 In general, two types of processes are used heterogeneous, gas phase oxidation and homogeneous liquid phase oxidation. The former tend to involve supported metal or metal oxide catalysts e.g. in tne manufacture of ethylene oxide, acrylonitrile and maleic anhydride whilst the latter generally employ dissolved metal salts, e.g. in the production of terephthalic acid, benzoic acid, acetic acid, phenol and propylene oxide. 

The materials of construction of the radiant coil are highly heat-resistant steel alloys, such as Sicromal containing 25% Cr, 20% Ni, and 2% Si. Triethyl phosphate [78-40-0] catalyst is injected into the acetic acid vapor. Ammonia [7664-41-7] is added to the gas mixture leaving the furnace to neutralize the catalyst and thus prevent ketene and water from recombining. The crude ketene obtained from this process contains water, acetic acid, acetic anhydride, and 7 vol % other gases (mainly carbon monoxide [630-08-0], carbon dioxide [124-38-9], ethylene [74-85-1], and methane [74-82-8]). The gas mixture is chilled to less than 100°C to remove water, unconverted acetic acid, and the acetic anhydride formed as a liquid phase (52,53). 

The process takes place in two stages. Firstly acetaldehyde and acetic anhydride form ethylidene diacetate in liquid phase at 120-140 °C with FeCl3 as a catalyst ... 

The fibrous acetylation process is performed in the presence of a suitable liquid, such as benzene, in which the reaction product is insoluble and which thereby retains the fiber form. For fibrous acetylation vapor-phase treatment with acetic anhydride can also be used. Besides sulfuric acid, perchloric acid and zinc chloride have been used as catalysts. 

Acetic Acid. Acetic acid production in the United States has increased by large numbers in the last half century, since the monomer has many uses such as to make polymers for chewing gum, to use as a comonomer in industrial and trade coatings and paint, and so on. In the 1930s, a three-step synthesis process from ethylene through acid hydrolysis to ethanol followed by catalytic dehydrogenation of acetaldehyde and then a direct liquid-phase oxidation to acetic acid and acetic anhydride as co-products was used to produce acetic acid... 

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... 

Distillation with reaction, where the normal process is coupled with a liquid phase reaction, is also interesting and esterifications of certain alcohols with acids are typical industrial applications. These include, among others the homogeneously catalyzed butyl acetate process and the production of the plasticizer di-octyl-phthalate from phthalic anhydride and 2-ethyl-hexanol. However, the subject which involves both product formation and separation aspects has not usually been treated in the literature relating specifically to "mass transfer with reaction". 

The oxidation of pseudocumene to trimellitic anhydride can be carried out in the liquid-phase using cobalt/manganese salts and bromine compounds as catalysts in acetic acid Amoco process). 

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