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Shell-and-tube reactor for preparing maleic anhydride

IP.com Disclosure Number: IPCOM000195608D
Publication Date: 2010-May-07
Document File: 7 page(s) / 29K

Publishing Venue

The IP.com Prior Art Database

Abstract

The present publication refers to an apparatus for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a feed stream comprising hydrocarbons having at least 4 carbon atoms per molecule, which comprises a reactor having a bundle of reaction tubes into which a solid-state catalyst over which the exothermic reaction of the feed stream with an oxygen-comprising gas stream takes place has been introduced and also one or more pumps and one or more heat exchangers which are located outside the reactor and through which a heat transfer medium formed by a salt melt flows through the intermediate space in the reactor between the reaction tubes and takes up the heat of reaction, with the temperature of the salt melt being in the range from 350 to 480°C, wherein the reaction tubes are made of a heat-resistant alloy steel which comprises either at least 0.5% by weight of chromium or at least 0.25% by weight of molybdenum or at least 0.5% by weight of chromium and at least 0.25% by weight of molybdenum, is proposed.

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(Gerhard Olbert, Dr. Hans-Jürgen Bassler, Dr. Michael Steiniger, BASF SE, 67067 Ludwigshafen, Germany)

The publication relates to an apparatus comprising a shell-and-tube reactor for preparing maleic anhydride (hereinafter referred to as MAn for short) by heterogeneously catalyzed gas-phase oxidation of hydrocarbons having at least four carbon atoms by means of oxygen-comprising gases in the presence of a volatile phosphorus compound over a catalyst comprising vanadium, phosphorus and oxygen.

MAn is mainly used in the production of unsaturated polyester resins which are used as composites in the construction and automobile industry. In addition, MAn is an important intermediate in the synthesis of gamma-butyrolactone, tetrahydrofuran and 1,4-butanediol, which are in turn used as solvents or, for example, are processed further to form polymers such as polytetrahydrofuran or polyvinylpyrrolidone.

The preparation of MAn by heterogeneously catalyzed gas-phase oxidation of hydrocarbons having at least four carbon atoms by means of oxygen in a shell- and-tube reactor over a solid-state catalyst is generally known and is described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, 1999 Electronic Release, Chapter "MALEIC AND FUMARIC ACID - Maleic Anhydride". In general, benzene or C4-hydrocarbons such as 1,3-butadiene, n-butenes or n- butane are used for this purpose.

Preference is given to using solid-state catalysts comprising vanadium, phosphorus and oxygen as active composition.

The catalysts comprising vanadium, phosphorus and oxygen, which are hereinafter referred to as "VPO catalysts", are used in unpromoted or promoted form.

The conversion of the hydrocarbons into MAn over such VPO catalysts proceeds strongly exothermically.

These gas-phase reactions are usually carried out at reaction temperatures in the range from 390°C to 500°C.

Reactors in which these strongly exothermic heterogeneously catalyzed gas- phase reactions can be carried out on an industrial scale are described, for example, in EP 1 882 518 A2.

These are shell-and-tube reactors in which the reaction tubes filled with the VPO catalyst are arranged vertically and a heat transfer medium flows around the outsides of the reaction tubes.

To control the temperature of the strongly exothermic gas-phase reaction in the reaction tubes, use is made of heat transfer media comprising, for example, liquid salt melts. Mixtures of alkali metal nitrates and alkali metal nitrites, for example

Shell-and-tube reactor for preparing maleic anhydride

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potassium nitrate, sodium nitrite and sodium nitrate, having a preferably eutectic composition have been found to be particularly useful.

Although the use of such salt melts at temperatures up to 620°C would be conceivable, the temperature of the salt melt is limited to about 450°C-480°C. This takes account of both the thermal stability of the salt mixture and also the requirements i...