Abstract:
Beschrieben wird ein Verfahren zum Anfahren eines Gasphasenoxidationsreaktors, der ein Bett eines ersten Katalysators, dessen aktive Masse eine katalytisch aktive Silber-Vanadiumoxid-Bronze enthält, und wenigstens ein Bett eines zweiten Katalysators umfasst, dessen katalytisch aktive Masse Vanadiumpentoxid und Titandioxid enthält, und der mittels eines Wärmetransfermediums temperierbar ist. Im Betriebszustand leitet man einen Gasstrom, der eine Beladung C op eines Kohlenwasserstoffs und molekularen Sauerstoff umfasst, bei einer Temperatur T op des Wärmetransfermediums über das Bett des ersten und zweiten Katalysators durch den Reaktor. Zum Anfahren leitet man a) einen Gasstrom mit einer Anfangsbeladung C o , die kleiner ist als C op , und bei einer Anfangstemperatur T o des Wärmetransfermediums, die kleiner ist als T op , durch den Reaktor und bringt b) die Temperatur des Wärmetransfermediums auf T op und die Beladung des Gasstroms auf C op . Das Verfahren vereint eine kurze Anfahrzeit ohne Überschreiten von Emissions- bzw. Qualitätsvorgaben, lange Katalysatorlebensdauer, hohe Ausbeute und geringe Bildung von Nebenprodukten.
Abstract:
The invention relates to a catalyst having a catalytically active substance, which contains a phase A and a phase B in the form of three-dimensionally extended delimited areas, phase A being a silver-vanadium bronze and phase B being a mixed oxide phase based on titanium dioxide and vanadium pentoxide. The catalyst is used for producing aldehydes, carboxylic acids and/or carboxylic acid anhydrides from aromatic or heteroaromatic hydrocarbons by gas-phase oxidation.
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 another in the reaction tube, with the proviso that the least active catalyst layer is preceded upstream by at least one more active catalyst layer in flow direction. The 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 least active catalyst layer being preceded upstream in flow direction by a more active catalyst layer.
Abstract:
A method for production of a catalyst for gas phase oxidations is disclosed, whereby a suspension of Ti02 and V205 particles is applied to a fluidised inert support, wherein at least 90 vol. % of the V205 particles have a diameter of 20 μm or less and at least 95 vol. % of the V205 particles have a diameter of 30 μm or less. The defined particle size distribution of the V205 permits a high coating efficiency.
Abstract:
Disclosed is a method for producing a catalyst containing vanadium, phosphorus, and oxygen, which is used for oxidizing the gas phase of a hydrocarbon having at least four carbon atoms to maleic anhydride. According to the inventive method, a corresponding catalyst precursor which contains vanadium, phosphorus, and oxygen and is provided with particles having an average diameter of at least 2 mm is converted into a catalytically active form by means of calcination, and a flow of the catalyst precursor is transported on a conveyor belt across at least one calcination area over a distance ln at an essentially steady speed in order to be calcinated. The variation over time of the gas temperature in relation to the set point value amounts to ≤ 5 °C at each position in the area of the flow of the catalyst precursor, which lies within the second half ln/2 of the calcination area, while the local difference in the gas temperature between any positions in the area of the flow of the catalyst precursor, which is located within the second half ln/2 of the calcination area, amounts to ≤ 5 °C.
Abstract:
The invention relates to a method for start-up of oxidation catalysts, characterised in that the catalyst is started up at a temperature of 360 °C to 400 °C, with an air supply of 1.0 to 3.5 Nm3/h and a hydrocarbon loading of 20 to 65 g/Nm3 with formation of a hot spot in the first 7 to 20 % of the catalyst bed at a temperature of 390 °C to less than 450 °C.
Abstract:
The invention relates to a method for producing a catalyst-precursor containing vanadium, phosphorous and oxygen for the production of maleic acid anhydride by means of heterogeneous catalytic gas phase oxidation of a hydrocarbon having at least four hydrocarbon atoms, wherein (a) vanadium pentoxide is reacted with 102 - 110 % phosphorous acid in a temperature range of between 80 - 160 °C in the presence of a primary or secondary, non-cyclic or cyclic, non-branched or branched, saturated alcohol having 3 - 6 carbon atoms; (b) the formed deposit is isolated; (c) a content of organic carbon of = 1.1 wt. % is adjusted in the insulated deposit by tempering in a temperature range of between 250 - 350 °C, whereby the tempered product produces a powder-x ray diffraction diagram after the addition of 3.0 wt. % graphite, said diagram having a peak height ratio of the peak in the 2?-range of = 0,1 of a possibly existing pyrophosphate phase at 28.5° to the peak at 26.6° emerging from the graphite and, d) the tempered product obtained from step c) is formed to obtain particles having an average diameter of at least 2mm. The invention also relates to a catalyst-precursor obtained according to said method for producing a catalyst from the catalyst-precursor, a catalyst which can be obtained according to said method, in addition to a method for producing maleic acid anhydride on said catalyst.
Abstract:
The invention relates to a catalyst system for producing carboxylic acids and/or carboxylic acid anhydrides, said system having at least three catalysts layers that are situated one above the other in the reaction tube, with the proviso that the active mass fraction, in relation to the total mass of the catalyst, of one or more of the central catalyst layers is lower than the active mass fraction of one or more of the upper catalyst layers lying on the gas inlet side and is lower than the active mass fraction of one or more of the lower catalyst layers lying on the gas outlet side. The invention also relates to a method for gas phase oxidation using said catalyst system.