Abstract: A process for the catalytic gas-phase oxidation of propene to acrylic acid, in which the reaction gas starting mixture is oxidized, with a high propene loading, in a first reaction stage, over a first fixed-bed catalyst which is housed in two successive reaction zones A, B, the reaction zone B being kept at a higher temperature than the reaction zone A, and the acrolein-containing product gas mixture of the first reaction stage is then oxidized in a second reaction stage, with a high acrolein loading, over a second fixed-bed catalyst which is housed in two successive reaction zones C, D, the reaction zone D being kept at a higher temperature than the reaction zone C.

Abstract: C2-C8-olefins are oligomerized in a process in which a stream of an olefin-containing hydrocarbon mixture is passed over a heterogeneous, nickel-containing oligomerization catalyst in n successive adiabatically operated reaction zones, where n?2, and the hydrocarbon mixture experiences a temperature increase 66 Treact in each reaction zone and the hydrocarbon mixture enters the first reaction zone at a temperature Tin and before entering each further reaction zone is cooled to a temperature which in each case may be up to 20° C. above or below Tin, and the relative catalyst volumes of the individual reaction zones are such that the difference in ?Treact between any two reaction zones is not more than 20° C.

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 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: The multimetal oxide materials essentially consisting of Mo12BiaX1bFecX2dX3eOy  (I) where: X1 is Co and/or Ni, X2 is Si and/or Al, X3 is an alkali metal, 0.3≦a≦1, 2≦b≦10, 0.5≦c≦10, 0≦d≦10, 0≦e≦0.5 and y is the absolute value of the number which, assuming charge neutrality, is obtained from the sum of the valences and the stoichiometric coefficients of the other elements, the crystalline fractions containing, in addition to &bgr;-X1MoO4 as the main component, Fe2(MoO4)3 as a secondary component and no MoO3.

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.

Abstract: Catalysts of the formula I?A.sub.a B.sub.b O.sub.x !.sub.p ?C.sub.c D.sub.d Fe.sub.e Co.sub.f E.sub.i F.sub.j O.sub.y !.sub.q I,whereA is bismuth, tellurium, antimony, tin and/or copper,B is molybdenum and/or tungsten,C is an alkali metal, thallium and/or samarium,D is an alkaline earth metal, nickel, copper, cobalt, manganese, zinc, tin, cerium, chromium, cadmium, molybdenum, bismuth and/or mercury,E is phosphorus, arsenic, boron and/or antimony,F is a rare-earth metal, vanadium and/or uranium,a is from 0.01 to 8,b is from 0.1 to 30,c is from 0 to 4,d is from 0 to 20,e is from 0 to 20,f is from 0 to 20,i is from 0 to 6,j is from 0 to 15,x and y are numbers determined by the valency and frequency of the elements other than oxygen in I, and p and q are numbers whose ratio p/q is in the range from 0.001 to 0.

Abstract: In a process for preparing acrolein, acrylic acid or a mixture thereof from propane, propane is partially dehydrogenated to propylene in a first stage, the product gas mixture resulting therefrom is, after separating off hydrogen and water vapor, used as feed to an oxidation reactor, the propylene formed in the dehydrogenation is partially oxidized in the oxidation reactor using molecular oxygen in the presence of non-dehydrogenated propane as inert diluent gas to give acrolein, acrylic acid or a mixture thereof and the propane present in the product gas mixture of the partial oxidation is subsequently recirculated to the dehydrogenation stage A.

Abstract: In a process for the continuous heterogeneously catalyzed gas-phase oxidation of propylene to acrolein, acrylic acid or a mixture thereof in an oxidation reactor whose feed gas mixture comprises, apart from propylene and molecular oxygen as oxidant, only at least one diluent gas which is essentially inert under the conditions of the heterogeneously catalyzed gas-phase oxidation and where, in continuous operation, at least a part of the essentially inert diluent gases present in the product gas mixture is separated off therefrom and is reused as a constituent of the feed gas mixture to the oxidation reactor, the essentially inert diluent gas mixture comprises more than 85% by volume of at least one saturated hydrocarbon having from 1 to 5 carbon atoms.

Abstract: Cesium based multimetal oxide compositions which are suitable as catalysts for the gas-phase-catalytic oxidative preparation of methacrolein from isobutene or tert-butanol or its methyl ether. The catalysts are characterized by increased selectivity for the formation of methacrolein. The catalysts have locally delimited regions of an oxide composition, preferably (Bi.sub.2 W.sub.2 O.sub.9), surrounded by the remaining constituents of the multimetal oxide.

Abstract: Multimetal oxide compositions having a two-phase structure and comprising molybdenum, hydrogen, one or more of the elements phosphorus, arsenic, boron, germanium and silicon, and their use for the preparation of methacrylic acid by gas-phase catalytic oxidation.

Abstract: A process for the gas phase catalytic oxidation of a C.sub.3-6 alkane, alkanol, alkene or alkenal using as a catalyst multimetal oxide compositions of the formula I, [X.sup.1.sub.a X.sup.2.sub.b O.sub.x ].sub.p [X.sup.3.sub.c X.sup.4.sub.d X.sup.5.sub.e X.sup.6.sub.f X.sup.7.sub.g X.sup.2.sub.h O.sub.y ].sub.q, where X.sup.1 is bismuth, tellurium, antimony, tin and/or copper, X.sup.2 is molybdenum and/or tungsten, X.sup.3 is an alkali metal, thallium and/or samarium, X.sup.4 is an alkaline earth metal, nickel, cobalt, copper, manganose, zinc, tin, cadmium and/or mercury, X.sup.6 is iron, chromium, cerium and/or vanadium, X.sup.6 is phosphorus, arsenic, boron and/or antimony, X.sup.7 is a rare-earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, geranium, lead, thorium and/or uranium, a is from 0.01 to 8, b is from 0.

Abstract: Multimetal oxide compositions of the formula I[X.sup.1.sub.a X.sup.2.sub.b O.sub.x ].sub.p [X.sup.3.sub.c X.sup.4.sub.d X.sup.5.sub.e X.sup.6.sub.f X.sup.7.sub.g X.sup.2.sub.h O.sub.y ].sub.q(I)whereX.sup.1 is bismuth, tellurium, antimony, tin and/or copper,X.sup.2 is molybdenum and/or tungsten,X.sup.3 is an alkali metal, thallium and/or samarium,X.sup.4 is an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and/or mercury,X.sup.5 is iron, chromium, cerium and/or vanadium,X.sup.6 is phosphorus, arsenic, boron and/or antimony,X.sup.7 is a rare-earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and/or uranium,a is from 0.01 to 8,b is from 0.

Abstract: A process for the catalytic gas-phase oxidation of acrolein to acrylic acid in a fixed-bed reactor with contacting tubes, at elevated temperature on catalytically active oxides with a conversion of acrolein for a single pass of .gtoreq.95%, wherein the reaction temperature in the flow direction along the contacting tubes in a first reaction zone before the starting reaction gases containing the reactants enter the contacting tubes is from 260.degree. to 300.degree. C. until an acrolein conversion of from 20 to 40% is reached, and the reaction temperature is subsequently reduced by a total of from 5.degree. to 40.degree. C., abruptly or successively in steps or continuously along the contacting tubes until a methacrolein conversion of .gtoreq.95% has been reached, with the proviso that the reaction temperature in this secondary reaction zone is not lower than 240.degree. C.

Abstract: A process for the catalytic gas-phase oxidation of methacrolein to methacrylic acid in a fixed-bed reactor with contacting tubes, at elevated temperature on catalytically active oxides with a conversion of methacrolein for a single pass of from 40 to 95 mol%, wherein the reaction temperature in the flow direction along the contacting tubes in a first reaction zone from entry of the starting reaction gases containing the reactants into the contacting tubes is from 280 to 340.degree. C. until a methacrolein conversion of from 20 to 40% is reached, and the reaction temperature is subsequently reduced by a total of from 5.degree. to 40.degree. C., abruptly or successively in steps or continuously along the contacting tubes until a methacrolein conversion of from 45 to 95% has been reached, with the proviso that the reaction temperature in this second reaction zone is not lower than 260.degree. C.