Abstract: A process for charging a reactor with a fixed catalyst bed which comprises at least one annular shaped support catalyst body K, in which, before the charging, fragments formed in the preparation of the shaped catalyst bodies K are removed by screening.

Abstract: What is described is a process for starting up a gas phase oxidation reactor for oxidation of o-xylene to phthalic anhydride, said reactor comprising at least one catalyst layer and being temperature-controllable by means of a heat carrier medium, wherein a) the catalyst layer is interrupted by a moderator layer which is less catalytically active than the catalyst layer or is catalytically inactive, b) a gas stream is passed through the reactor with an initial loading of o-xylene and at an initial temperature of the heat transfer medium, c) the loading of the gas stream is increased to a target loading and, in parallel, the temperature of the heat transfer medium is lowered to an operating temperature. The introduction of the moderator layer allows the loading to be increased more rapidly and the startup time to be shortened.

Abstract: The present invention relates to a process for gas-phase oxidation, in which a gaseous stream comprising an aromatic hydrocarbon and molecular oxygen is passed through two or more catalyst zones. Furthermore, the present invention relates to a catalyst system for gas-phase reaction using a preliminary zone.

Abstract: The present invention relates to a process for gas-phase oxidation, in which a gaseous stream comprising an aromatic hydrocarbon and molecular oxygen is passed through two or more catalyst zones. Furthermore, the present invention relates to a catalyst system for gas-phase reaction using a preliminary zone.

Abstract: A process for preparing a vanadium, phosphorus, and oxygen comprising catalyst precursor for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms, which comprises (a) reacting vanadium pentoxide with 102% to 110% strength phosphoric acid in the presence of isobutanol and optionally of a primary or secondary, noncyclic or cyclic, unbranched or branched, saturated alcohol having 3 to 6 carbon atoms in a temperature range from 80 to 160° C.; (b) isolating the precipitate formed; (c) (i) drying the isolated precipitate down to a residual isobutanol content of less than 5% by weight; (ii) then passing a gas which in addition to one or more inert gases comprises 0.1% to 9% by volume of oxygen through the dried precipitate, directly or after isolation, in the temperature range from 130° C. to 200° C.

Abstract: A process for gas phase oxidation in which a gaseous stream which comprises at least one aromatic hydrocarbon and molecular oxygen is passed through one or more catalyst layers, wherein a moderator layer is arranged between two catalyst layers arranged in succession in flow direction of the gaseous stream, the moderator layer being less catalytically active than the catalysts adjacent upstream and downstream or being catalytically inactive. The desired oxidation products are obtained in high yield over prolonged periods.

Abstract: The catalytically active mass of a catalyst molded body comprises a multi-element oxide containing vanadium and phosphorus. The specific pore volume PV (in ml/g) of the catalyst molded body, the bulk density p of the catalyst molded body (in kg/l), the geometric surface area Ageo (in mm2), and the geometric volume Vgeo (in mm3) of the catalyst molded body satisfy the condition 0.275<PV·?·Ageo/Vgeo. In a method for producing maleic acid anhydride by heterogeneously catalytic gas phase oxidation of a hydrocarbon, the catalyst molded body allows a lower pressure loss and a high yield.

Abstract: The invention relates to a catalyst molded body for preparing maleic anhydride by gas-phase oxidation of a hydrocarbon having at least four carbon atoms using a catalytically active composition contains vanadium, phosphorus and oxygen, where the shaped catalyst body has an essentially cylindrical body having a longitudinal axis, wherein the cylindrical body has at least two parallel internal holes which are essentially parallel to the cylinder axis of the body and go right through the body. The catalyst molded body has a large outer surface area, a lower pressure loss and sufficient mechanical stability.

Abstract: The invention relates to a process for preparing potassium and potassium compounds

Abstract: A process for introducing annular coated catalysts K into a reaction tube of a tube bundle reactor, in which adhering pairs of annular coated catalysts K formed in the preparation of the annular coated catalysts K, before the introduction thereof into the reaction tube, are removed at least partly from the annular coated catalysts K.

Abstract: A catalyst for gas phase oxidations comprises an inert support and a catalytically active material which comprises vanadium oxide and titanium dioxide and has been applied thereto. The titanium dioxide has a content of sulfur compounds, calculated as S, of less than 1000 ppm and a content of calcium compounds, calculated as Ca, of less than 150 ppm. The catalyst has a relatively high activity and/or selectivity and thus enables relatively high yields of the desired target product, for example phthalic anhydride. Also described is a process for preparing phthalic anhydride, wherein a gas stream which comprises molecular oxygen and o-xylene, naphthalene or mixtures thereof is contacted with the catalyst.

Abstract: What is described is a process for starting up a gas phase oxidation reactor for oxidation of o-xylene to phthalic anhydride, said reactor comprising at least one catalyst layer and being temperature-controllable by means of a heat carrier medium, wherein a) the catalyst layer is interrupted by a moderator layer which is less catalytically active than the catalyst layer or is catalytically inactive, b) a gas stream is passed through the reactor with an initial loading of o-xylene and at an initial temperature of the heat transfer medium, c) the loading of the gas stream is increased to a target loading and, in parallel, the temperature of the heat transfer medium is lowered to an operating temperature. The introduction of the moderator layer allows the loading to be increased more rapidly and the startup time to be shortened.

Abstract: What is described is a method for starting a gas phase oxidation reactor that contains a bed of a first catalyst whose active material comprises a catalytically active silver-vanadium oxide bronze, and at least one bed of a second catalyst whose catalytically active material comprises vanadium pentoxide and titanium dioxide, and whose temperature is controllable by means of a heat transfer medium. In the operating state, a gas stream which comprises a loading cop of a hydrocarbon and molecular oxygen is passed through the reactor over the bed of the first and second catalyst at a temperature Top of the heat transfer medium. For the startup, a) a gas stream is passed through the reactor with a starting loading c0 which is less than cop, and at a starting temperature T0 of the heat transfer medium which is less than Top, and b) the temperature of the heat transfer medium is brought to Top and the loading of the gas stream to cop.

Abstract: The present invention relates to a process for gas-phase oxidation, in which a gaseous stream comprising an aromatic hydrocarbon and molecular oxygen is passed through two or more catalyst zones. Furthermore, the present invention relates to a catalyst system for gas-phase reaction using a preliminary zone.

Abstract: Catalyst systems for preparing carboxylic acids and/or anhydrides, the catalyst system comprising a reaction zone and a layered catalyst, the reaction zone comprises a gas inlet region and a gas outlet region, the layered catalyst comprises an active composition and one or more middle layers, one or more first layers disposed on a side of the one or more middle layers toward the gas inlet region, and one or more second layers on a side of the one or more middle layers toward the gas outlet region, wherein the active composition content of one or more of the middle catalyst layers, based on total mass of the layered catalyst, is lower than the active composition content of the one or more first catalyst layers and is lower than one or more second catalyst layers; and processes for gas phase oxidation employing a layered catalyst of the present invention.

Abstract: The present invention relates to a catalyst system for preparing carboxylic acids and/or carboxylic anhydrides which has at least three catalyst layers arranged one on top of the other in the reaction tube, with the proviso that the most inactive catalyst layer is preceded in the upstream direction by a more active catalyst layer. The invention further relates to a process for gas phase oxidation in which a gaseous stream which comprises one hydrocarbon and molecular oxygen is passed through a plurality of catalyst layers, the least active catalyst layer being upstream of a more active catalyst layer.

Abstract: A process for gas phase oxidation in which a gaseous stream which comprises at least one aromatic hydrocarbon and molecular oxygen is passed through one or more catalyst layers, wherein a moderator layer is arranged between two catalyst layers arranged in succession in flow direction of the gaseous stream, the moderator layer being less catalytically active than the catalysts adjacent upstream and downstream or being catalytically inactive. The desired oxidation products are obtained in high yield over prolonged periods.

Abstract: The present invention relates to a catalyst system for preparing carboxylic acids and/or carboxylic anhydrides which has at least four catalyst layers arranged one on top of another in the reaction tube, the ratio of the bed lengths of the more selective catalyst layers to the bed lengths of the more active catalyst layers being between 1.4 and 2. The present invention further relates to a process for gas phase oxidation in which a gaseous stream which comprises a hydrocarbon and molecular oxygen is passed through a plurality of catalyst layers, the ratio of the bed lengths of the more selective catalyst layers to the bed lengths of the more active catalyst layers being between 1.4 and 2.

Abstract: A process for introducing annular coated catalysts K into a reaction tube of a tube bundle reactor, in which adhering pairs of annular coated catalysts K formed in the preparation of the annular coated catalysts K, before the introduction thereof into the reaction tube, are removed at least partly from the annular coated catalysts K.

Abstract: A process for charging a reactor with a fixed catalyst bed which comprises at least one annular shaped support catalyst body K, in which, before the charging, fragments formed in the preparation of the shaped catalyst bodies K are removed by screening.