Abstract: Described herein is a process for preparing butane-1,4-diol by catalytic hydrogenation of butyne-1,4-diol in a reaction zone with hydrogen in the presence of a heterogeneous hydrogenation catalyst, in which the content of at least one gas selected from CO and CH4 in the offgas stream is measured and the content of the gas measured in the offgas stream is used for closed-loop control of the hydrogenation.

Abstract: Processes for decreasing fumaric acid deposits in preparing maleic anhydride by heterogeneously catalyzed oxidation of a hydrocarbon with molecular oxygen. Maleic anhydride is absorbed from the crude mixture in an absorbent in an absorption column and desorbed in a desorption column, the entirety or portion of absorbent depleted in maleic anhydride, for controlled precipitation of fumaric acid, being cooled and/or concentrated by evaporating a portion of absorbent such that the difference between the concentration of fumaric acid in the recycle stream at the outlet of the desorption column under existing conditions and the equilibrium concentration of fumaric acid according to the solubility curve after cooling and/or evaporation of a portion of absorbent is ?250 ppm by weight, and the fumaric acid precipitated as a solid is removed completely or partly from the absorbent recycling system and the fumaric acid-depleted absorbent is recycled completely or partly to the absorption column.

Abstract: What is described is a process for obtaining maleic anhydride by distillation from a solution of maleic anhydride in a high-boiling absorbent which has been obtained by gas phase oxidation of a hydrocarbon and at least partial absorption of the oxidation products into the absorbent, by i) introducing the solution into the side of a feed column with a rectifying section disposed above the feed point and a stripping section disposed below the feed point, ii) providing an upper combining column which communicates with the upper end of the rectifying section and a lower combining column which communicates with the lower end of the stripping section, iii) providing a draw column which communicates with the upper combining column and the lower combining column, iv) drawing maleic anhydride off as a side draw from the draw column, and drawing off compounds having a lower boiling point than maleic anhydride at the top of the upper combining column and the high-boiling absorbent at the bottom of the lower combining c

Abstract: The present invention relates to a process for preparing tetrahydrofuran by absorption of C4-dicarboxylic acids and/or derivatives thereof from a crude product mixture into an organic solvent or water as absorption medium, removal of the absorption medium, catalytic hydrogenation of the resulting C4-dicarboxylic acids and/or derivatives thereof and distillation of the water-comprising crude tetrahydrofuran in at least one distillation column, wherein THF-comprising waste streams from the distillation are catalytically hydrogenated with complete or partial recirculation to the process.

Abstract: A process for decreasing fumaric acid deposits in the preparation of maleic anhydride by heterogeneously catalyzed oxidation of a hydrocarbon with molecular oxygen, in which the maleic anhydride is absorbed from the crude product mixture in an absorbent in an absorption column and desorbed again in a desorption column, the entirety or a portion of the absorbent depleted in maleic anhydride, for controlled precipitation of fumaric acid, being cooled and/or concentrated by evaporating a portion of the absorbent to such an extent that the difference between the concentration of fumaric acid in the recycle stream at the outlet of the desorption column under the conditions existing there and the equilibrium concentration of fumaric acid according to the solubility curve after the cooling and/or evaporation of a portion of the absorbent is greater than or equal to 250 ppm by weight, and the fumaric acid precipitated as a solid is removed completely or partly from the absorbent recycling system and the fumaric acid-

Abstract: What is described is a process for obtaining maleic anhydride by distillation from a solution of maleic anhydride in a high-boiling absorbent which has been obtained by gas phase oxidation of a hydrocarbon and at least partial absorption of the oxidation products into the absorbent, by i) introducing the solution into the side of a feed column with a rectifying section disposed above the feed point and a stripping section disposed below the feed point, ii) providing an upper combining column which communicates with the upper end of the rectifying section and a lower combining column which communicates with the lower end of the stripping section, iii) providing a draw column which communicates with the upper combining column and the lower combining column, iv) drawing maleic anhydride off as a side draw from the draw column, and drawing off compounds having a lower boiling point than maleic anhydride at the top of the upper combining column and the high-boiling absorbent at the bottom of the lower combining c

Abstract: A process for preparing a vanadium, phosphorus, and oxygen catalyst precursor for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms, which comprises (a) reacting vanadium pentoxide with from 102 to 110% strength phosphoric acid in the presence of a primary or secondary, noncyclic or cyclic, unbranched or branched, saturated alcohol having from 3 to 6 carbon atoms in a temperature range from 80 to 160° C.; (b) isolating the precipitate formed; (c) setting an organic carbon content of ?1.1% by weight in the isolated precipitate by heat treatment in a temperature range from 250 to 350° C., the heat-treated product, following the addition of 3.0% by weight of graphite, giving a powder X-ray diffraction diagram which in the 2? region features a ratio of the height of the peak of any pyrophosphate phase present at 28.5° to the height of the peak due to the graphite at 26.6° of ?0.

Abstract: A process for preparing a vanadium, phosphorus, and oxygen catalyst precursor for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms, by reacting vanadium pentoxide (I) in the presence of a primary or secondary, noncyclic or cyclic, unbranched or branched, saturated alcohol having from 3 to 6 carbon atoms (II) with a pentavalent or trivalent phosphorus compound (III) in a temperature range from 80 to 160° C. with stirring and subsequently filtering the resultant suspension, in which (a) the way in which the phosphorus compound (III) and the vanadium pentoxide (I) are combined in the presence of the alcohol (II), (b) the action of a stirring power of from 0.01 to 0.6 W/kg suspension, and/or (c) the filtration at a temperature from 65° C. to 160° C.

Abstract: Process for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of hydrocarbons having at least four carbon atoms by means of oxygen-containing gases at from 350 to 500° C.

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 1n 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.

Abstract: Process for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of hydrocarbons having at least four carbon atoms by means of oxygen-containing gases at from 350 to 500° C.

Abstract: A process for preparing a vanadium, phosphorus, and oxygen catalyst precursor for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms, by reacting vanadium pentoxide (I) in the presence of a primary or secondary, noncyclic or cyclic, unbranched or branched, saturated alcohol having from 3 to 6 carbon atoms (II) with a pentavalent or trivalent phosphorus compound (III) in a temperature range from 80 to 160° C. with stirring and subsequently filtering the resultant suspension, in which (a) the way in which the phosphorus compound (III) and the vanadium pentoxide (I) are combined in the presence of the alcohol (II), (b) the action of a stirring power of from 0.01 to 0.6 W/kg suspension, and/or (c) the filtration at a temperature from 65° C. to 160° C.

Abstract: A process for preparing a vanadium, phosphorus, and oxygen catalyst precursor for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms, which comprises (a) reacting vanadium pentoxide with from 102 to 110% strength phosphoric acid in the presence of a primary or secondary, noncyclic or cyclic, unbranched or branched, saturated alcohol having from 3 to 6 carbon atoms in a temperature range from 80 to 160° C.; (b) isolating the precipitate formed; (c) setting an organic carbon content of ?1.1% by weight in the isolated precipitate by heat treatment in a temperature range from 250 to 350° C., the heat-treated product, following the addition of 3.0% by weight of graphite, giving a powder X-ray diffraction diagram which in the 2? region features a ratio of the height of the peak of any pyrophosphate phase present at 28.5° to the height of the peak due to the graphite at 26.6° of ?0.

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.

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: A vanadium-, phosphorus- and oxygen-containing catalyst for the preparation of maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon of at least four carbon atoms has a phosphorus/vanadium ratio of from 0.9 to 1.5, comprises particles having a mean diameter of at least 2 mm and has a composition which, using CuK&agr; radiation (&lgr;=1.54·10−10 m), gives a powder X-ray diffraction pattern which, in the 2&thgr; range from 10° to 70°, has a signal/background ratio of ≦10 for all diffraction lines which are attributable to a vanadium- and phosphorus-containing phase. Said catalyst is prepared and is used for the preparation of maleic anhydride.

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: A process for the selective preparation of acetic acid from a gaseous feed comprising ethane, ethylene or mixtures thereof plus oxygen at elevated temperature, which comprises bringing the gaseous feed into contact with a catalyst comprising the elements Mo, Pd, Re, X and Y in gram atom ratios a:b:c:d:e in combination with oxygenMo.sub.a Pd.sub.b Re.sub.c X.sub.d Y.sub.e (I)where the symbols X, Y have the following meanings:X=Cr, Mn, Nb, B, Ta, Ti, V and/or WY=Bi, Ce, Co, Cu, Te, Fe, Li, K, Na, Rb, Be, Mg, Ca, Sr, Ba, Ni, P, Pb, Sb, Si, Sn, Tl and/or U;the indices a, b, c, d and e are the gram atom ratios of the corresponding elements, wherea=1, b>0, c>0, d=0.05-2, e=0-3.