Abstract: A process is described for selectively hydrogenating citronellal to citronellol in which a liquid phase, in which the citronellal is dissolved and particles of a catalyst are suspended which is capable of preferentially hydrogenating carbon-oxygen double bonds over carbon—carbon double bonds, is conducted through a device which inhibits the transport of the catalyst particles in the presence of a hydrogen-containing gas.

Abstract: A process is described for selectively hydrogenating citronellal to citronellol in which a liquid phase, in which the citronellal is dissolved and particles of a catalyst are suspended which is capable of preferentially hydrogenating carbon-oxygen double bonds over carbon-carbon double bonds, is conducted through a device which inhibits the transport of the catalyst particles in the presence of a hydrogen-containing gas.

Abstract: The present invention relates to a continuous process for the preparation of unsaturated acetals by reacting olefinically unsaturated aliphatic compounds with allyl alcohols in a reaction column, where the reactants are only partially reacted in the reaction column, the resulting acetal is concentrated in at least two successive evaporation stages, and the recovered reactants are returned to the reaction column.

Abstract: An &agr;,&bgr;-unsaturated carbonyl compound of formula (I) where R1 is saturated C1-40-hydrocarbyl or a substituted or unsubstituted aromatic radical containing moiety, and R2, R3 and R4, independently of one another, are hydrogen or a C1- to C4-alkyl group, is selectively hydrogenated in the liquid phase to a saturated carbonyl compound of formula (II) with hydrogen in the presence of a pulverulent palladium and/or rhodium catalyst and in the presence of an organic base, by conducting the hydrogenation in a packed bubble column reactor in which product is recycled and hydrogen gas is recirculated.

Abstract: The present invention relates to a continuous process for the preparation of unsaturated acetals by reacting olefinically unsaturated aliphatic compounds with allyl alcohols in a reaction column, where the reactants are only partially reacted in the reaction column, the resulting acetal is concentrated in at least two successive evaporation stages, and the recovered reactants are returned to the reaction column.

Abstract: The process for the preparation of carbonyl compounds of the formula I where R1 and R2 are a hydrocarbon radical, or R1 and R2 together are an unsubstituted or substituted alkylene group, and X is ═O or two alkoxy groups, comprises oxidizing alcohols of the formula II  where R1 to R2 and X are as defined above, with oxygen in the gaseous phase a) at temperatures of from 270 to 600° C. on silver coated catalysts which comprise an abrasion-resistant coating of metallic silver on a core of inert support material, or b) at temperatures of from 450 to 750° C. on silver crystals and/or copper crystals having a particle size of from 0.1 to 2.5 mm for a residence time of at most 0.1 second. Also claimed is an advantageous overall process for the preparation of &agr;-diketones, preferably diacetal, from the corresponding ketone, in particular methyl ethyl ketone, via the carbonyl compounds of the formula I where X is two alkoxy groups.

Abstract: The process for the preparation of carbonyl compounds of the formula I where R1 and R2 are a hydrocarbon radical, or R1 and R2 together are an unsubstituted or substituted alkylene group, and X is=O or two alkoxy groups, comprises oxidizing alcohols of the formula II where R1 to R2 and X are as defined above, with oxygen in the gaseous phase a) at temperatures of from 270 to 600° C. on silver coated catalysts which comprise an abrasion-resistant coating of metallic silver on a core of inert support material, or b) at temperatures of from 450 to 750° C. on silver crystals and/or copper crystals having a particle size of from 0.1 to 2.5 mm for a residence time of at most 0.1 second. Also claimed is an advantageous overall process for the preparation of &agr;-diketones, preferably diacetal, from the corresponding ketone, in particular methyl ethyl ketone, via the carbonyl compounds of the formula I where X is two alkoxy groups.

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: A process for continuous industrial production of unsaturated aliphatic aldehydes having a boiling range from 95 to 136.degree. C. by oxidative dehydrogenation of the corresponding alcohols with an oxygen-comprising gas over a supported catalyst consisting of copper, silver and/or gold on an inert support in a tube bundle reactor, rapid cooling of the reaction gases and removal of the aldehydes from the resulting condensate with recycling of the unconverted alcohols comprisesa) vaporizing the alcohol,b) admixing the alcohol vapor with an oxygen-comprising gas,c) initially passing the resulting oxygen-comprising alcohol vapor at above the dew point of the alcohol but below the commencement temperature of the reaction through a layer of one of the abovementioned supported catalysts which is at least 0.5 cm in thickness and only thend) reacting the oxygen-comprising alcohol vapor at from 300 to 600.degree. C.

Abstract: The preparation of 3-alkoxycarbonyl propenals and 3-dialkoxymethyl propenals of the general formulae Ia and Ib respectively: ##STR1## (R.sup.1 =C.sub.1 -C.sub.3 -alkyl group; R.sup.2 and R.sup.3 =hydrogen, methyl, or ethyl; and R.sup.4 and R.sup.5 =C.sub.1 -C.sub.4 -alkyl groups, which may be joined to form a 5-membered or 6-membered ring), is effected by reacting a corresponding alcohol of the general formula IIa or IIb ##STR2## with oxygen or an oxygen-containing gas in the gas phase in the presence of a metal from Group IB of the Periodic Table or a compound of one such metal acting as catalyst.The target products serve as intermediates for the synthesis of carotenoids.

Abstract: In a tube bundle reactor for carrying out catalytic organic reactions in the gas phase, comprising reaction tubes (A) arranged between tubesheets (B), the reaction tubes have an inside diameter ranging from 0.5 to 3 cm, the ratio of reaction tube length to inside diameter ranges from 2 to 10, and the reaction tubes (A) are surrounded by a fluid heat transport medium flowing in the crosswise direction; said tube bundle reactor is useful in particular in exothermic organic reactions.

Abstract: The preparation of bicyclic enol-ethers (I) ##STR1## (where n is from 3 to 12, and R.sup.1, R.sup.2 and R.sup.3 may be H or C.sub.1 --C.sub.4 -alkyl) by free radical adduct formation of CHR.sup.1 =CR.sup.2 --CHR.sup.3 --O--R.sup.4 (III)(where R.sup.4 is tert.-butyl, tetrahydrofuran-2-yl or tetrahydropyran-2-yl) with a cyclic ketone (IV) ##STR2## followed by acid-catalyzed cyclization, and novel compounds II ##STR3## The compounds (I) and (II) are intermediates for the synthesis of musk-like fragrances.

Abstract: A process for the production of cyanuric acid in which urea and an inert solvent are passed into a reaction zone in which pyrolysis of the urea with the formation of cyanuric acid takes place at 200.degree. to 300.degree.C, from 50 to 760 mm and a space-time yield of from 0.1 to 2 kg of cyanuric acid per liter of reaction volume per hour, and the cyanuric acid is separated in a crystal separation zone and freed from solvent in a falling film evaporator.