Vanadium pentoxide, catalyst

Fumaric acid is conveniently prepared by the oxidation of the inexpensive furfural with sodium chlorate in the presence of a vanadium pentoxide catalyst ... 

C. Fumaric acid from furfural. Place in a 1-litre three-necked flask, fitted with a reflux condenser, a mechanical stirrer and a thermometer, 112 5 g. of sodium chlorate, 250 ml. of water and 0 -5 g. of vanadium pentoxide catalyst (1), Set the stirrer in motion, heat the flask on an asbestos-centred wire gauze to 70-75°, and add 4 ml. of 50 g. (43 ml.) of technical furfural. As soon as the vigorous reaction commences (2) bvi not before, add the remainder of the furfural through a dropping funnel, inserted into the top of the condenser by means of a grooved cork, at such a rate that the vigorous reaction is maintained (25-30 minutes). Then heat the reaction mixture at 70-75° for 5-6 hours (3) and allow to stand overnight at the laboratory temperature. Filter the crystalline fumaric acid with suction, and wash it with a little cold water (4). Recrystallise the crude fumaric acid from about 300 ml. of iif-hydrochloric acid, and dry the crystals (26 g.) at 100°. The m.p. in a sealed capillary tube is 282-284°. A further recrystaUisation raises the m.p. to 286-287°. 

The vanadium pentoxide catalyst Is prepared as follows Suspend 5 g. of pure ammonium vanadate in 50 ml. of water and add slowly 7 5 ml. of pure concentrated hydrochloric acid. Allow the reddish-brown, semi-colloidal precipitate to settle (preferably overnight), decant the supernatant solution, and wash the precipitate several times by decantation. Finally, suspend the precipitate in 76 ml. of water and allow it to stand for 3 days. This treatment renders the precipitate granular and easy to 6lter. Filter the precipitate with suction, wash it several times with cold 5 p>er cent, sodium chloride solution to remove hydrochloric acid. Dry the product at 120° for 12 hours, grind it in a mortar to a fine powder, and heat again at 120° for 12 hours. The yield of catalyst is about 3 - 5 g. 

Vapor-phase oxidation over a promoted vanadium pentoxide catalyst gives a 90% yield of maleic anhydride [108-31-6] (139). Liquid-phase oxidation with a supported palladium catalyst gives 55% of succinic acid [110-15-6] (140). 

Chemically, 2,2,2-trifluoroethanol behaves as a typical alcohol. It can be converted to trifluoroacetaldehyde [75-90-1] or trifluoroacetic acid [76-05-1] by various oxidi2iag agents such as aqueous chlorine solutions (51) or oxygen ia the preseace of a vanadium pentoxide catalyst (52). Under basic conditions, it adds to tetrafluoroethylene and acetylene to give, respectively, 1,1,2,2-tetrafluoroethyl 2/2/2 -trifluoroethyl ether [406-78-0] (53) and... 

Oxidation of methanol to formaldehyde with vanadium pentoxide catalyst was first patented in 1921 (90), followed in 1933 by a patent for an iron oxide—molybdenum oxide catalyst (91), which is stiU the choice in the 1990s. Catalysts are improved by modification with small amounts of other metal oxides (92), support on inert carriers (93), and methods of preparation (94,95) and activation (96). In 1952, the first commercial plant using an iron—molybdenum oxide catalyst was put into operation (97). It is estimated that 70% of the new formaldehyde installed capacity is the metal oxide process (98). 

Oxidation. Benzene can be oxidized to a number of different products. Strong oxidizing agents such as permanganate or dichromate oxidize benzene to carbon dioxide and water under rigorous conditions. Benzene can be selectively oxidized in the vapor phase to maleic anhydride. The reaction occurs in the presence of air with a promoted vanadium pentoxide catalyst (11). Prior to 1986, this process provided most of the world s maleic anhydride [108-31 -6] C4H2O2. Currendy maleic anhydride is manufactured from the air oxidation of / -butane also employing a vanadium pentoxide catalyst. 

The ethyl ester is prepared in 60 per cent yield by passing ethyl lactate with air or oxygen over a vanadium pentoxide catalyst. Boehringer Sohn, U. S. pat. 1,614,195 (1927). [C. A. ai, 746 (1927).]... 

CAT-OX [Catalytic oxidation] An adaptation of the Contact process for making sulfuric acid, using the dilute sulfur dioxide in flue-gases. A conventional vanadium pentoxide catalyst is used. Developed by Monsanto Enviro-Chemical Systems, and operated in Pennsylvania and Illinois in the early 1970s. 

The process. A typical process for phthalic anhydride starts with mixing hor q-xylene vapor with excess preheated air in a ratio of 20 1 air to o-xylene by weight. The gaseous mixture is then fed to a reactor consisting of tubes packed with vanadium pentoxide catalyst on a silica gel. The reaction takes place at 800—1000°F. Like most oxidation reactions, this one is exothermic, and the heat of reaction must be removed from the tubes to maintain the reaction temperature. 

Sulfur dioxide combines with oxygen on heating and in the presence of a catalyst. This reaction proceeds at temperatures between 400 to 700°C with vanadium pentoxide catalyst to make sulfuric acid ... 

Vanadium pentoxide (V203)-based catalysts, for example, are extensively used in industry for a number of catalytic processes including the selective oxidation of aromatic hydrocarbons and transformation of SOj into SO3 [14,15]. The vanadium pentoxide catalysts are usually prepared in supported form on a proper... 

Kon, 109 Perkin, 108 n-Valeraldehyde, 322 n-Valeric acid, 354, 355,357,359,487 iso-Valeric acid, 354, 355 n-Valeronitrile, 408 Vanadium pentoxide catalyst, 463 Vapour pressure, 1, 2 of mixtures, 6-11 Veratraldehyde, 803, 804 Veratronitrile, 803, 804 Veronal, 1002, 1003 Vibro mixer, 65 Vinylacetio acid, 463, 465... 

Catalysts based on V2Os are particularly effective for the production of maleic acid anhydride. Pure V2Os, as well as several modified vanadium pentoxide catalysts, have been investigated. 

Vanadium pentoxide catalysts modified with P2Os or Sn02 were studied also by Ai and Suzuki [5,9,10], P2Os strongly reduces the activity as shown in Table 25 for a ratio of P/V = 1.6. At the same time, the formation of maleic anhydride is suppressed, and maximum selectivities for the... 

Sulphuric acid (98%) 400 000 tonnes Sulphur-burning process, followed by catalytic oxidation of S0-> (vanadium pentoxide catalyst). 

Most plants use reactors with various stages in order to cool the stream for the catalytic step. Conversion by a vanadium pentoxide catalyst deposited on a silicate support is the critical step in the process, in which the gaseous stream is passed over successive layers of catalyst. The gas mixture is then passed through an absorption tower. Oleum, the product, is a concentrated solution of sulfuric acid containing excess sulfur trioxide. 

Deactivation of catalysts is a major problem in o-xylene oxidation [6,7]. For this reaction, deactivation has been mainly attributed to the irreversible anatase - rutile transformation [2,3]. In fact, anatase was found to be the best support for vanadium pentoxide catalysts leading the presence of rutile to lower activities and selectivities [8,9], The anatase-rutile transition can take place at temperatures above 973 K [10] but it is known that the presence of vanadia promotes such transformation [11-14] which, in these conditions, can start at 773 K [14], Such temperatures are easily attained in industrial reactors due to the high exothermicity of o-xylene oxidation that can lead to the formation of temperature profiles lengthwise with pronounced maxima (hot spot) [1]. 

Example 8.8 Entropy production in a homogeneous chemical system The oxidation of sulfur dioxide to trioxide over a vanadium pentoxide catalyst is... 

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