Abstract: A process for the long-term operation of a heterogeneously catalyzed partial gas phase oxidation of an organic starting compound, in which the reaction gas input mixture is partially oxidized over a fixed catalyst bed which is accommodated in two successive temperature zones A, B whose temperature is changed with increasing operating time such that the initially lower temperature increases and the difference between the two temperatures decreases.

Abstract: A process for long-term operation of a heterogeneously catalyzed partial gas phase oxidation of propene to acrolein, in which the propene present in the reaction gas input mixture is partially oxidized as this gas mixture passes through the fixed catalyst bed which is accommodated in two spatially successive temperature zones A, B, and, in long-term operation, as a measure to counteract the reduction in the quality of the fixed catalyst bed, the temperature of at least one of the two temperature zones is increased such that the difference TB?TA becomes increasingly greater, where TB is the temperature of temperature zone B, and TA the temperature of temperature zone A.

Abstract: A process for preparing acrylic acid from methanol and acetic acid, in which, in a reaction zone A, the methanol is partially oxidized to formaldehyde in a heterogeneously catalyzed gas phase reaction, the product gas mixture A obtained and an acetic acid source are used to obtain a reaction gas input mixture B which comprises acetic acid and formaldehyde and has the acetic acid in excess over the formaldehyde, and the formaldehyde present in reaction gas input mixture B is aldol-condensed to acrylic acid under heterogeneous catalysis in a reaction zone B with acetic acid present in reaction gas input mixture B, and unconverted acetic acid still present alongside the acrylic acid target product in the product gas mixture B obtained is removed therefrom, and the acetic acid removed is recycled into the production of reaction gas input mixture B.

Abstract: A process for preparing a multielement oxide composition comprising the element iron in oxidic form, in which the source of the elemental constituent of iron used is an aqueous iron nitrate solution whose preparation comprises the melting of a solid hydrate of iron nitrate.

Abstract: A process for operating a continuous removal of a target product X in the form of fine crystals of a liquid phase P comprising the target product X and constituents other than the target product X by cooling suspension crystallization in the secondary chamber of an indirect heat exchanger to which liquid phase P flows continuously with simultaneous continuous flow through the primary chamber of the indirect heat exchanger with a coolant, and continuous withdrawal of a crystal suspension S having a degree of crystallization Y from the secondary chamber in two operating states I and II, wherein the coolant temperature is lower, the mass flow of liquid phase P is greater and the molar proportion of the constituents other than the target product X in the liquid phase P in operating state II is greater than in operating state I.

Abstract: A process for starting-up a heterogeneously catalyzed partial gas phase oxidation of acrolein to acrylic acid or of methacrolein to methacrylic acid over a fixed catalyst bed disposed in a tube bundle reactor cooled by a heat exchange medium, wherein the temperature of the heat exchange medium is ?290° C. and the temperature of that reactor plate surface which faces the reaction gas entry mixture and the temperature of the reaction gas entry mixture itself are ?285° C.

Abstract: An eggshell catalyst consisting of a hollow cylindrical support body of length 2 to 10 mm, external diameter 4 to 10 mm and wall thickness 1 to 4 mm, and an eggshell, applied to the outer surface of the support body, of catalytically active oxide material of the general formula I, Mo12V2 to 4W0 to 3Cu0.8 to 1.5X10 to 4X20 to 40On??(I) in which the variables are each defined as follows: X1=one or more elements of the alkali metals and alkaline earth metals; X2=one or more elements from the group of Si, Al, Ti and Zr; and n=the stoichiometric coefficient of the element oxygen, which is determined by the stoichiometric coefficients of the elements other than oxygen and the charges thereof in I.

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 continuously removing a target product X in the form of fine crystals from a liquid phase P comprising the target product X and constituents other than the target product X by cooling suspension crystallization in the secondary chamber, into which the liquid phase P flows continuously, of an indirect heat exchanger with simultaneous continuous flow of a coolant through the primary chamber of the indirect heat exchanger and continuous withdrawal of a crystal suspension S having a degree of crystallization Y from the secondary chamber, in which the degree of crystallization Y is adjusted on the basis of a heat balance conducted continuously with the aid of a process computer.

Abstract: A process for preparing (meth)acrolein by heterogeneously catalyzed gas phase partial oxidation of a precursor compound, in which the reaction gas mixture which comprises at least 3% by volume of precursor compound is passed through a fresh fixed catalyst bed whose active material is a multielement oxide which comprises the elements Mo, Fe and Bi and at least one of the elements Ni and Co, and the fixed catalyst bed is loaded with at least 40 l (STP)/l·h of precursor compound, and the precursor compound is converted to an extent of at least 90 mol %, wherein, over the first 8000 operating hours, during X=10 to 500 operating hours, the highest temperature of the reaction gas mixture in the fixed catalyst bed is 400 to 450° C. and, during the remaining 8000?X operating hours, is 300 to <400° C., and the loading of the fixed catalyst bed with organic precursor compound, averaged over the time, for the X=10 to 500 operating hours is greater than for the 8000?X operating hours.

Abstract: A process for starting up a separating process for purifying removal of acrylic acid crystals from a suspension S of crystals thereof in mother liquor with a hydraulic wash column which has a crystal melt circuit including crystal melt space, and a process space and a distributor space which are separated by an end with passages connecting the two spaces, in which the crystal bed is formed for the first time by first filling the crystal melt circuit and, at least partly, the process space with an acrylic acid-comprising startup liquid whose acrylic acid crystal formation temperature is less than or equal to the temperature of the suspension S increased by 15° C.

Abstract: A process for purifying removal of acrylic acid, methacrylic acid, N-vinylpyrrolidone or p-xylene crystals from their suspension in mother liquor by means of a wash column with forced transport, whose shell of the process chamber is a metal wall, the wash column additionally being enveloped by a thermal insulation material having a water vapor barrier and a specific heat flow of >0.1 W/m2 and <10 W/m2 flowing into the process chamber through the metal wall of the wash column.

Abstract: A process for preparing at least one partial oxidation and/or ammoxidation product of a hydrocarbon by partially dehydrogenating at least one saturated hydrocarbon H under heterogeneous catalysis and using the resulting product gas mixture A, which comprises the partially dehydrogenated hydrocarbon H, as such or in modified form for heterogeneously catalyzed partial oxidation and/or ammoxidation of the partially dehydrogenated hydrocarbon present in the product gas mixture A, said process including at least one mechanical separating operation inserted between the product gas mixture A and the heterogeneously catalyzed partial oxidation and/or ammoxidation.

Abstract: A process for the long-term operation of a heterogeneously catalyzed partial gas phase oxidation of an organic starting compound, in which the reaction gas input mixture is partially oxidized over a fixed catalyst bed which is accommodated in two successive temperature zones A, B whose temperature is changed with increasing operating time such that the initially lower temperature increases and the difference between the two temperatures decreases.

Abstract: A process for preparing acrolein or acrylic acid or a mixture thereof as the target product from propane, in which propane is partially dehydrogenated under heterogeneous catalysis in a reaction zone A, molecular hydrogen formed is at least partly combusted to water, any water present in the product gas A formed in reaction zone A is removed therefrom and product gas A is otherwise used to charge a reaction zone B in which propylene formed in reaction zone A is partially oxidized in the presence of remaining propane to give the target product. The target product is removed from the product gas B formed in reaction zone B and propane present in the remaining residual gas is absorbed therefrom into a solvent and, after release from the absorbate, recycled into reaction zone A.

Abstract: A process for removal of a crude acrylic acid from a product gas mixture which comprises glyoxal as a by-product from a heterogeneously catalyzed partial gas phase oxidation of at least one C3 precursor compound, which comprises the absorption of the acrylic acid in a high-boiling absorbent and the rectificative workup of the resulting adsorbate, and in which absorbent present in the bottoms liquid withdrawn from the bottom space of the absorption column is distilled off in a distillation unit and recycled into the absorption, before high boilers which remain are discharged, and in which the glyoxal content of the crude acrylic acid is reduced by restricting the high boiler residence time in the distillation unit.

Abstract: A process for continuous heterogeneously catalyzed partial dehydrogenation of at least one hydrocarbon to be dehydrogenated in a reactor which is manufactured from a composite material which consists, on its side in contact with the reaction chamber, of a steel B with specific elemental composition which, on its side facing away from the reaction chamber, either directly or via an intermediate layer of copper, or of nickel, or of copper and nickel, is plated onto a steel A with specific elemental composition, and also partial oxidations of the dehydrogenated hydrocarbon and the reactor itself.

Abstract: A process for the long-term operation of a heterogeneously catalyzed partial gas phase oxidation of an organic starting compound, in which the reaction gas input mixture is partially oxidized over a fixed catalyst bed which is accommodated in two successive temperature zones A, B whose temperature is changed with increasing operating time such that the initially lower temperature increases and the difference between the two temperatures decreases.

Abstract: A process for continuous heterogeneously catalyzed partial dehydrogenation of at least one hydrocarbon to be dehydrogenated in a reactor which is manufactured from a composite material which consists, on its side in contact with the reaction chamber, of a steel B with specific elemental composition which, on its side facing away from the reaction chamber, either directly or via an intermediate layer of copper, or of nickel, or of copper and nickel, is plated onto a steel A with specific elemental composition, and also partial oxidations of the dehydrogenated hydrocarbon and the reactor itself.

Abstract: A process for heterogeneously catalyzed partial dehydrogenation of a hydrocarbon, in which a reaction gas mixture input stream comprising the hydrocarbon to be dehydrogenated is conducted through a fixed catalyst bed disposed in a shaft and the reaction gas mixture input stream is obtained in the shaft by metering an input gas II comprising molecular oxygen upstream of the fixed catalyst bed into an input gas stream I which comprises molecular hydrogen and the hydrocarbon to be dehydrogenated and is flowing within the shaft toward the fixed catalyst bed.