Abstract: A process for preparing ketones by so-called “crossed aldol condensation” of a ketone with an aldehyde in the presence of a catalyst system consisting of approximately equimolar amounts of a secondary amine and of a carboxylic acid containing at least 2 C atoms, to form an &agr;,&bgr;-unsaturated ketone, and, where appropriate, subsequent catalytic hydrogenation.

Abstract: In a process for the preparation of methylglyoxal dimethyl acetal from methylglyoxal and methanol in the presence of an acidic ion exchanger, water is introduced in an amount sufficient to form an acidic reaction mixture in which the acetal product and water form an azeotropic mixture, with or without the retention of some methanol reactant. After subjecting a single phase acidic reaction mixture to an azeotropic distillation, it will separate into two distinct liquid phases with a simple recovery of the acetal product from the aqueous phase.

Abstract: The fixed-bed catalyst comprises palladium and selenium or tellurium or a mixture of selenium and tellurium on a silicon dioxide support and has a BET surface area of from 80 to 380 m2/g and a pore volume of from 0.6 to 0.95 cm3/g in the pore diameter range from 3 nm to 300 &mgr;m, with from 80 to 95% of the pore volume being in the pore diameter range from 10 to 100 nm. It is prepared by impregnating a silicon dioxide support with a solution of a palladium compound and a selenium compound or tellurium compound or a mixture of a selenium compound and a tellurium compound, drying it and reducing it in the presence of hydrogen. The catalyst is used, in particular, for isomerizing 3-buten-1-ol compounds.

Abstract: 3,7-Dimethyl-2,6-octadien-1-al of formula I is prepared continuously by: thermally cleaving, in the presence or absence of an acid catalyst, 3-methyl-2-buten-1-al diprenyl acetal of formula II: thereby eliminating 3-methyl-2-buten-1-ol of formula III and yielding cis/trans-prenyl 3-methylbutadienyl ether of formula IV: thermally rearranging the resultant butadienyl ether of formula IV thereby yielding 2,4,4-trimethyl-3-formyl-1,5-hexadiene of formula V: subsequently rearranging intermediate (V) thereby yielding citral product of formula I, which comprises: as the reaction proceeds, continuously distilling the reaction mixture thereby continuously removing prenol, which is formed by degradation of acetal II, and the intermediates of formula IV and V and any citral product which is formed during the reaction; and thermally rearranging said intermediates of formula IV and V at a temperature of 100-200° C.

Abstract: The invention relates to a process for the selective liquid-phase hydrogenation of .alpha.,.beta.-unsaturated carbonyl compounds of the formula I, ##STR1## where R.sub.1 is hydrogen or an organic radical, and R.sub.2, R.sub.3 and R.sub.4, independently of one another, are hydrogen or a C.sub.1 -- to C.sub.4 --alkyl group, to saturated carbonyl compounds of the formula II ##STR2## using hydrogen in the presence of a pulverulent palladium and/or rhodium catalyst and in the presence of an organic base. The process is carried out in a packed bubble column reactor (1, 2) with product recycling (11, 17) and circulating hydrogen gas (4, 15, 16). It is particularly suitable for the selective hydrogenation of citral to citronellal.

Abstract: In a process for carrying out an exothermal reaction, selected from the addition reaction of organomagnesium halide compounds to carbonyl compounds and the ensuing hydrolysis of the addition product, a considerable fraction of the heat liberated during the reaction is removed by evaporation of the solvent.

Abstract: A process for preparing glyoxal monoacetals of the formula I, ##STR1## where R.sup.1 and R.sup.2, which can be identical or different, are C.sub.1 -C.sub.4 alkyl or C.sub.2 -C.sub.4 alkenyl involves reacting a mixture of glyoxal and glyoxal bisacetals of the formula II, ##STR2## where R.sup.1 and R.sup.2 have the meaning given above, with an excess of an alcohol of the formula R.sup.1 OH or R.sup.2 OH or mixtures of these in the presence of an acid catalyst until reaction equilibrium is achieved.

Abstract: In a process for the catalytic hydrogenation of 2,5- and 2,3-dihydrofuran with hydrogen to give tetrahydrofuran, use is made of a catalyst in which a metal or a plurality of metals have been deposited by vapor deposition or sputtering on a metal wire mesh or a metal foil as support.

Abstract: Catalytic reactions are carried out in a reactor which contains a liquid phase in which at least one catalyst is suspended, and which may additionally contain a gas phase, by a process in which the liquid phase and, if present, also the gas phase are fed, at least partly, through an apparatus having orifices or channels in the reactor, the hydraulic diameter of which orifices or channels is from 0.5 to 20 mm, preferably from 1 to 10 mm, particularly preferably from 1 to 3 mm.

Abstract: A dividing wall column for separating a mixture into 3 or more fractions by distillation is described, where at least one dividing wall is detachably attached within the dividing wall column.

Abstract: To compensate the bypassing, at the edges, of the liquid flowing downward in a distillation column, in order to achieve optimum mass transfer with the ascending vapor, a specific nonuniform distribution of the liquid trickling density over the column cross-section is established including the steps of establishing a nonuniform distribution of the liquid trickling density over the column cross-section in the distillation column and adjusting the liquid trickling density in the wall regions, said nonuniform distribution being achieved bya) arranging a number of outlet orifices or the diameter of the outlet orifices of a liquid distributor orb) arranging baffles in the stripping sections at height intervals from 0.1 to 2 m, in the case of dumped packings with baffles which project into the column space from the wall by about from 0.

Abstract: In a distillation column for separating a liquid mixture into a plurality of pure fractions, the distillation column being divided into 2 parts, a feed part and a take-off part, in its middle region by a separation effective in the longitudinal direction, the separation consists of two walls with a gas space in between, the distance between the two walls being from 1 to 50 mm, preferably from 3 to 10 mm.

Abstract: Small amounts of a medium-boiling fraction are removed from a liquid mixture by distillation using a distillation column (main column) having a rectifying part and a stripping part, the liquid mixture containing relatively large amounts of lower-boiling and higher-boiling components, and the rectifying part being connected to the upper end of a second distillation column (side column) and the stripping part to the lower end of the said column, and the medium-boiling fraction being removed in vapor or liquid form from its middle section, by a process in which the concentration of the medium-boiling fraction in the liquid mixture is less than 2%, preferably less than 0.1%, and the amount of vapor passed into the lower end of the side column from the main column is 1-20%, preferably 3-10%, based on the amount of vapor in the main column at the relevant point.

Abstract: Organic iodine compounds are separated from carbonylation products of methanol, methyl acetate and dimethyl ether and from mixtures of such carbonylation products by a process wherein the iodine compounds are removed by liquid phase extraction with a non-aromatic hydrocarbon.

Abstract: 1,3-Butadiene is isolated from a C.sub.4 -hydrocarbon mixture containing 1,3-butadiene and small amount of propyne and C.sub.5 -hydrocarbons by extractive distillation with a selective solvent and subsequent distillative purification of the crude 1,3-butadiene obtained in the extractive distillation.

Abstract: Distillative separation of liquid mixtures of one or more water-insoluble substances which have boiling points higher than that of water and one or more substances which have boiling points lower than that of water or which form azeotropes having boiling points lower than that of water, wherein the mixture to be distilled is mixed with a quantity of water such that the boiling point of the water under the pressure applied limits the bottom temperature of the mixture of substances to be separated.

Abstract: Formamide is prepared continuously from methyl formate and ammonia, pure methanol being recovered, by a process wherein(a) the reaction of methyl formate and ammonia is carried out predominantly in the liquid phase in the upper region of a reaction column R having a total of from 15 to 30 theoretical plates,(b) the methanol formed in this reaction is removed, together with small amounts of formamide, from the column or the evaporator in vaporus form at the level of plates 1-5 (counted from the bottom),(c) the formamide is removed from this methanol/formamide mixture, together with small amounts of methanol, in a distillation column D1 and recycled to R, and(d) the small amounts of methanol contained in the bottom product from R, which substantially consists of formamide and in this column should be at from 110.degree. to 130.degree. C., are separated off in a distillation column D2.

Abstract: Formic acid is recovered, by distillation, from its mixtures with solvents of the general formula I ##STR1## where R.sup.1 is hydrogen, methyl, ethyl or vinyl and R.sup.2 and R.sup.3 are each alkyl, cycloalkyl, aryl or aralkyl, or R.sup.2 and R.sup.3 together form a 1,4- or 1,5-alkylene group, in each case of not more than 8 carbon atoms, with the provisos that the sum of the number of carbon atoms in R.sup.2 and R.sup.3 is 7 to 14 and that only one of these radicals is aryl, by a method in which the distillation is carried out in the presence of a carboxamide II which is selected from the group consisting of formamide, acetamide, propionamide and the same compounds substituted by N-methyl or N,N-dimethyl, and which has a boiling point lower than that of the solvent I.

Abstract: Ethanol is prepared by hydrogenating acetic acid under superatmospheric pressure and at elevated temperatures by a process wherein a predominantly cobalt-containing catalyst is used and acetic acid and hydrogen are passed through the reactor, at from 210.degree. to 330.degree. C. and under from 10 to 350 bar, under conditions such that a liquid phase in not formed during this procedure.

Abstract: A process for separating off organic iodine compounds from acetaldehyde-free carbonylation products of methanol, methyl acetate and dimethyl ether by removing the iodine compounds by azeotropic distillation with a hydrocarbon having a boiling point, under atmospheric pressure, of 25-55.degree. C.