Abstract: A process for the preparation of acrylic acid or methacrylic acid is described, in which propane or isobutane is reacted with molecular oxygen in the gas phase in a fluidized-bed reactor containing a catalyst, the catalyst containing a multimetal oxide comprising molybdenum, tellurium and/or antimony, vanadium and niobium, and a catalyst activator which comprises at least one tellurium compound being added to the reactor during the reaction.

Abstract: Reactor membranes for used in oxidation reactions of hydrocarbons involving oxygen comprising a selective oxidation catalyst on a mixed conducting, oxide ion selective ceramic membrane of the composition (Sr1-xCax)1-yAyMn1-zBzO3-&dgr;, where A is Ba, Pb, Na, K, Y, an element of the lanthanide group or a combination thereof, B is Mg, Al, Ga, In, Sn, an element of the 3d or 4d period or a combination thereof, x is from 0.2 to 0.8, y is from 0 to 0.4, z is from 0 to 0.6, and &dgr; is a number, dependent on x, y and z, that renders the composition charge neutral.

Abstract: In a process for the preparation of acrylic acid by heterogeneously catalyzed gas-phase oxidation of propene with molecular oxygen in a reaction zone, the catalytically active material is a multimetal oxide which contains the elements Mo, V, Te and/or Sb and has a specific structure.

Abstract: The invention relates to a method for producing acrylic acid by the heterogeneously catalysed gas-phase oxidation of propane on a multi-metal oxide mass, said mass containing the elements Mo, V, Te and/or Sb and having a specific X-ray diffractogram.

Abstract: The invention relates to a catalyst which contains a catalytically active quantity of at least one oxygen-containing molybdenum and/or wolfram compound on an oxidic support material and which has been calcinated at temperatures of 400 to 900° C. after the precursor compound of the catalytically active compounds have been applied to the support material or to a support material precursor. The transport pores for this catalyst each have a diameter of >25 nm and a volume of at least 50 mm3/g. The catalyst contains x &mgr;mol (wolfram and/or molybdenum)/m2 molybdenum and/or wolfram, with 10.1<x<20.9 in relation to the finished catalyst, with the oxidic support material having a BET surface area of 135 to 220 m2/g. Catalysts of this type are characterized by an acidity of at least 70 &mgr;mol/g at pKs<−3 in the dry state and are therfore very active. The invention also relates to a method for producing a catalyst of this type and to the preferred use thereof.

Abstract: In a process for the preparation of acrolein or acrylic acid or a mixture thereof from propane, the propane is subjected, in a first reaction stage, to a partial dehydrogenation under heterogeneous catalysis to give propene, of the components contained in the product gas mixture formed in the first reaction stage other than propene and propane at least a portion of the molecular hydrogen present is then separated off from said mixture and the product gas mixture is then used for the preparation of acrolein and/or acrylic acid by gas-phase catalytic propylene oxidation, molecular nitrogen being present for diluting the reaction gas mixture during the propylene oxidation.

Abstract: A catalyst used in a process for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms by means of oxygen-containing gases comprises a catalytically active composition comprising vanadium, phosphorus and oxygen and has a essentially hollow cylindrical structure in which (a) the ratio of the height h to the diameter of the continuous hole d2 is not more than 1.5 and (b) the ratio of the geometric surface area Ageo to the geometric volume Vgeo is at least 2 mm−1.

Abstract: In a process for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of hydrocarbons having at least four carbon atoms using oxygen-containing gases in the presence of a volatile phosphorus compound over a catalyst comprising vanadium, phosphorus and oxygen in a shell-and-tube reactor unit having at least two successive cooled reaction zones, the temperature of the first reaction zone is from 350 to 450° C. and the temperature of the second and further reaction zones is from 350 to 480° C. and the temperature difference between the hottest reaction zone and the coolest reaction zone is at least 2° C.

Abstract: In a process for heterogeneously catalyzed gas-phase oxidation, a reaction gas starting mixture comprising propane, molecular oxygen and, if desired, inert gas is passed at from 300 to 500° C. over a fixed-bed catalyst.

Abstract: A process for the catalytic gas-phase oxidation of propene to acrylic acid, in which the reaction gas starting mixture is oxidized, with an increased propene loading, in a first reaction stage, over a first fixed-bed catalyst and then the acrolein-containing product gas mixture of the first reaction stage is oxidized, in a second reaction stage, with an increased acrolein loading, over a second fixed-bed catalyst, the catalyst moldings in both reaction stages having an annular geometry.

Abstract: In a process for the preparation of acrolein and/or acrylic acid from propane, the propane is subjected, in a first reaction stage, to a partial oxydehydrogenation with molecular oxygen under homogeneous and/or heterogeneous catalysis to give propene and the product gas mixture formed in the first reaction stage is then used for the preparation of acrolein and/or acrylic acid by gas-phase catalytic propene oxidation.

Abstract: In a process for the preparation of acrolein and/or acrylic acid from propane, the propane is subjected, in a first reaction stage, to an oxydehydrogenation with molecular oxygen under homogeneous and/or heterogeneous catalysis to give propene and the product gas mixture formed in the first reaction stage is then used for the preparation of acrolein and/or acrylic acid by gas-phase catalytic propene oxidation.

Abstract: In a process for the catalytic gas-phase oxidation of acrolein to acrylic acid, the reaction gas starting mixture is passed, with an acrolein loading of ≧150 l (s.t.p.)/l.h, over a fixed-bed catalyst which is housed in two spatially successive reaction zones A, B, the reaction zone B being kept at a higher temperature than the reaction zone A.

Abstract: In a process for the catalytic gas-phase oxidation of propene to acrolein, the reaction gas starting mixture is passed with a propene loading of ≧160 l(S.T.P.)/l·h over a fixed-bed catalyst which is housed in two spatially successive reaction zones A,B, the reaction zone B being kept at a higher temperature than the reaction zone A.

Abstract: In a process for the preparation of acrolein and/or acrylic acid from propane, the propane is subjected, in a first reaction stage, to a partial oxydehydrogenation with molecular oxygen under homogeneous and/or heterogeneous catalysis to give propene and the product gas mixture formed in the first reaction stage is then used for the preparation of acrolein and/or acrylic acid by gas-phase catalytic propene oxidation.

Abstract: In an industrial process for the heterogeneously catalyzed gas-phase oxidation of propane with molecular oxygen to give acrolein, the feed gas mixture having an initial undiluted molar ratio of the reactants propane:O2 of 7:3 is diluted with the reactant propane and, if desired, inert gases in such a way that the feed gas mixture comprises more than 70% by volume of propane and at least 5% by volume of O2.

Abstract: Multimetal oxides containing Mo, V and at least one of the elements W, Nb, Ti, Zr, Hf, Ta, Cr, Si and Ge and having a special three-dimensional atomic arrangement are used in catalysts for the catalytic gas-phase oxidation of organic compounds.

Abstract: A coated catalyst which consists of a hollow cylindrical carrier and a catalytically active oxide material applied to the outer surface of the carrier, the applied catalytically active oxide material being applied in a coat thickness of from 10 to 1000 &mgr;m, and having a specific catalytic surface area of from 20 to 30 m2/g and an abrasion of <10, preferably <5, particularly preferably <0.5, % by weight in the turntable abrasion test.

Abstract: Multimetal oxide materials containing molybdenum, vanadium, copper and one or more of the elements tungsten, niobium, tantalum, chromium and cerium and having a multiphase structure, and their use for the preparation of acrylic acid from acrolein by gas-phase catalytic oxidation, and oxometallates of the HT Cu molybdate structure type which contain Cu, Mo and at least one of the elements W, V, Nb and Ta.

Abstract: In a process for the continuous heterogeneously catalyzed gas-phase partial oxidation of an organic compound in an oxidation reactor, whose feed gas mixture comprises, apart from the organic compound to be partially oxidized and molecular oxygen as oxidant, at least one diluent gas which is essentially inert under the conditions of the heterogeneously catalyzed gas-phase partial oxidation, where the essentially inert diluent gas consists partly of combustible gases, after passage through the oxidation reactor, the combustible constituents of the inert diluent gas present in the product gas stream leaving the oxidation reactor are not recirculated to the heterogeneously catalyzed gas-phase partial oxidation, but are put to further use for the purposes of another chemical reaction.