Abstract: The present invention relates to a catalyst system for oxidation of o-xylene and/or naphthalene to phthalic anhydride (PA) comprising at least four catalyst zones arranged in succession in the reaction tube and filled with catalysts of different chemical composition wherein the active material of the catalysts comprise vanadium and titanium dioxide and the active material of the catalyst in the last catalyst zone towards the reactor outlet has an antimony content (calculated as antimony trioxide) between 0.7 to 3.0 wt. %.

Abstract: The invention relates to shaped catalyst bodies for the oxidation of SO2 to SO3, which comprise vanadium, at least one alkali metal and sulfate on a silicon dioxide support material, wherein the shaped body has the shape of a cylinder having 3 or 4 hollow-cylindrical convexities, obtainable by extrusion of a catalyst precursor composition comprising vanadium, at least one alkali metal and sulfate on a silicon dioxide support material through the opening of an extrusion tool, wherein the opening of the extrusion tool has a cross section formed by 3 or 4 partly overlapping rings whose midpoints lie essentially on a circular line having a diameter of y, wherein the rings are bounded by an outer line lying on a circle having an external diameter x1 and an inner line lying on a circle having an internal diameter x2.

Abstract: The invention relates to shaped catalyst bodies for the oxidation of SO2 to SO3, which comprise vanadium, at least one alkali metal and sulfate on a silicon dioxide support material, wherein the shaped body has the shape of a cylinder having 3 or 4 hollow-cylindrical convexities, obtainable by extrusion of a catalyst precursor composition comprising vanadium, at least one alkali metal and sulfate on a silicon dioxide support material through the opening of an extrusion tool, wherein the opening of the extrusion tool has a cross section formed by 3 or 4 partly overlapping rings whose midpoints lie essentially on a circular line having a diameter of y, wherein the rings are bounded by an outer line lying on a circle having an external diameter x1 and an inner line lying on a circle having an internal diameter x2.

Abstract: The present invention relates to a catalyst system for oxidation of o-xylene and/or naphthalene to phthalic anhydride (PA), comprising a plurality of catalyst zones arranged in succession in the reaction tube, which has been produced using antimony trioxide consisting predominantly of the senarmontite modification of which all primary crystallites have a size of less than 200 nm. The present invention further relates to a process for gas phase oxidation, in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst system which comprises a plurality of catalyst zones arranged in succession in the reaction tube and which has been produced using an antimony trioxide consisting predominantly of the senarmontite modification with a median primary crystallite size of less than 200 nm.

Abstract: The present invention relates to a catalyst system for oxidation of o-xylene and/or naphthalene to phthalic anhydride (PA), comprising a plurality of catalyst zones arranged in succession in the reaction tube, which have been produced using antimony trioxide comprising a noticeable proportion of senarmontite wherein some of the primary crystallites have a size of less than 200 nm. The present invention further relates to a process for gas phase oxidation, in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst system which comprises a plurality of catalyst zones arranged in succession in the reaction tube and which has been produced using an antimony trioxide comprising a noticeable proportion of senarmontite wherein some of the primary crystallites have a size of less than 200 nm.

Abstract: The present invention relates to a process for preparing phthalic anhydride by gas phase oxidation of aromatic hydrocarbons, in which a gas stream comprising at least one aromatic hydrocarbon and molecular oxygen is passed continuously over a thermostatted catalyst and the supply of the at least one aromatic hydrocarbon to the catalyst is temporarily interrupted after putting the catalyst on stream.

Abstract: The present invention relates to a catalyst for the epoxidation of alkenes, comprising silver, rhenium, cesium, lithium, tungsten and sulfur on a support. The present invention further relates to a process for producing the catalyst and the use of the catalyst for the oxidation of alkylenes to alkylene oxides. In addition, the present invention relates to a process for preparing ethylene oxide from ethylene, which comprises the oxidation of ethylene with oxygen in the presence of said catalyst.

Abstract: A process for preparing carboxylic acids and/or carboxylic anhydrides by gas phase oxidation of aromatic hydrocarbons, in which a gas stream comprising at least one aromatic hydrocarbon and molecular oxygen is passed continuously over a catalyst thermostatted by a heat carrier medium, which comprises keeping the temperature of the heat carrier medium constant during the startup of the reactor for at least 24 hours, during which neither the loading of the gas stream with hydrocarbons nor the gas stream volume is increased by more than 3%.

Abstract: The present invention relates to a catalyst system for oxidation of o-xylene and/or naphthalene to phthalic anhydride (PA), comprising a plurality of catalyst zones arranged in succession in the reaction tube, which have been produced using antimony trioxide comprising a noticeable proportion of senarmontite wherein some of the primary crystallites have a size of less than 200 nm. The present invention further relates to a process for gas phase oxidation, in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst system which comprises a plurality of catalyst zones arranged in succession in the reaction tube and which has been produced using an antimony trioxide comprising a noticeable proportion of senarmontite wherein some of the primary crystallites have a size of less than 200 nm.

Abstract: The present invention relates to a catalyst system for oxidation of o-xylene and/or naphthalene to phthalic anhydride (PA), comprising a plurality of catalyst zones arranged in succession in the reaction tube, which has been produced using antimony trioxide consisting predominantly of the senarmontite modification of which all primary crystallites have a size of less than 200 nm. The present invention further relates to a process for gas phase oxidation, in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst system which comprises a plurality of catalyst zones arranged in succession in the reaction tube and which has been produced using an antimony trioxide consisting predominantly of the senarmontite modification with a median primary crystallite size of less than 200 nm.

Abstract: A process for preparing carboxylic acids and/or carboxylic anhydrides by gas phase oxidation of aromatic hydrocarbons, in which a gas stream comprising at least one aromatic hydrocarbon and molecular oxygen is passed continuously over a catalyst thermostatted by a heat carrier medium, which comprises keeping the temperature of the heat carrier medium constant during the startup of the reactor for at least 24 hours, during which neither the loading of the gas stream with hydrocarbons nor the gas stream volume is increased by more than 3%.

Abstract: The present invention relates to a process for preparing phthalic anhydride by gas phase oxidation of aromatic hydrocarbons, in which a gas stream comprising at least one aromatic hydrocarbon and molecular oxygen is passed continuously over a thermostatted catalyst and the supply of the at least one aromatic hydrocarbon to the catalyst is temporarily interrupted after putting the catalyst on stream.

Abstract: The present invention relates to a catalyst for the oxidation of o-xylene and/or naphthalene to phthalic anhydride, which has a plurality of catalyst zones which are arranged in series in the reaction tube and have been produced using an antimony trioxide which comprises a significant proportion of valentinite. The present invention further relates to a process for gas-phase oxidation, in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst produced using an antimony trioxide which comprises a significant proportion of valentinite.

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 catalyst for preparing carboxylic acids and/or carboxylic anhydrides, which has a plurality of catalyst zones arranged in series and has been produced using a vanadium antimonate having a maximum content of crystalline valentinite of 5% by weight. The present invention further relates to a process for gas-phase oxidation in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst which has a plurality of catalyst zones arranged in series and has been produced using a vanadium antimonate having a maximum content of crystalline valentinite of 5% by weight.

Abstract: In a process for controlling a gas phase oxidation reactor for preparation of phthalic anhydride, by passing a gas stream which comprises an aromatic hydrocarbon and molecular oxygen through a multitude of reaction tubes arranged in the gas phase oxidation reactor, each of which comprises a bed of at least one catalyst and the temperature of which can be controlled by means of a heat transfer medium, at least one control parameter is measured and correcting interventions for control of the control parameter are determined, the at least one control parameter comprising the phthalic anhydride yield and the correcting parameter used being the temperature of the heat carrier medium. Over at least 90% of the lifetime of the catalyst, the change in the correcting parameter is limited to a maximum of 0.5 K within a period of 30 days. In this way, the cumulated phthalic anhydride yield over the lifetime of the catalyst is maximized.

Abstract: The present invention relates to a multilayer catalyst for preparing phthalic anhydride which has a plurality of catalyst layers arranged in succession in the reaction tube, with the individual catalyst layers having alkali metal contents which decrease in the flow direction. The present invention further relates to a process for the oxidation of naphthalene or o-xylene/naphthalene mixtures over such a multilayer catalyst and the use of such multilayer catalysts for the oxidation of naphthalene or o-xylene/naphthalene mixtures to phthalic anhydride.

Abstract: The present invention relates to a catalyst system for preparing carboxylic acids and/or carboxylic anhydrides, which system comprises a plurality of superposed catalyst layers arranged in a reaction tube, where vanadium antimonate is introduced into the active material in at least one of the catalyst layers. The present invention further relates to a process for gas-phase oxidation, in which a gaseous stream comprising at least one hydrocarbon and molecular oxygen is passed through a plurality of catalyst layers and the maximum hot spot temperature is below 425° C.

Abstract: The present invention relates to a catalyst for preparing carboxylic acids and/or carboxylic anhydrides, which has a plurality of catalyst zones arranged in series and has been produced using a vanadium antimonate having a maximum content of crystalline valentinite of 5% by weight. The present invention further relates to a process for gas-phase oxidation in which a gas stream comprising at least one hydrocarbon and molecular oxygen is passed through a catalyst which has a plurality of catalyst zones arranged in series and has been produced using a vanadium antimonate having a maximum content of crystalline valentinite of 5% by weight.

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.