Abstract: A dividing wall column is described which includes the following segments: a) an upper column region (1), b) an enrichment section (2) of the feed section, c) a stripping section (4) of the feed section, d) an upper part (3) of the offtake section, e) a lower part (5) of the offtake section, f) an intermediate region (9) of the feed section, g) an intermediate region (10) of the offtake section and h) a lower column region (6). The dividing wall column has a dividing wall (7) is located vertically between the segments b) (2) and d) (3) and between the segments c) (4) and e) (5). The segments b) (2), d) (3), c) (4) and e) (5) have separation-active internals, Segment b (2) has a cross-sectional area Ab which is at least 10% smaller than the cross-sectional area Ad of segment d) (3), and segment c) has a cross-sectional area Ac which is at least 10% greater than the cross-sectional area Ae of segment e) (5).

Abstract: A dividing wall column comprises the following segments: a) an upper column region (1), b) an enrichment section (2) of the feed section, c) a stripping section (4) of the feed section, d) an upper part (3) of the offtake section, e) a lower part (5) of the offtake section, f) an intermediate region (9) of the feed section, g) an intermediate region (10) of the offtake section and h) a lower column region (6). For the purposes of the present invention, it is essential that the dividing wall (7) is located vertically between the segments b) (2) and d) (3) and between the segments c) (4) and e) (5), the segments b) (2), d) (3), c) (4) and e) (5) have separation-active internals and the cross-sectional area Ab of the segment b) (2) is at least 10% smaller than the cross-sectional area Ad of segment d) (3), and the cross-sectional area Ac of the segment c) (4) is at least 10% greater than the cross-sectional area Ae of segment e) (5).

Abstract: The invention relates to a process for the preparation of L-ascorbic acid, in which free 2-keto-L-gulonic acid or C3-C10-alkyl 2-keto-L-gulonate is lactonized under acidic conditions in the presence of a water-miscible solvent and where this solvent in situ forms a solvent in which the ascorbic acid formed is poorly soluble.

Abstract: C1-C10-alkyl 2-keto-L-gulonates are prepared by esterifying 2-keto-L-gulonic acid or diacetone-2-keto-L-gulonic acid with a C1-C10-alcohol in the presence of an acidic catalyst by a process in which the esterification is carried out in a liquid film on a hot surface with simultaneous removal of water.

Abstract: The invention relates to a process for the preparation of L-ascorbic acid, in which free 2-keto-L-gulonic acid or C3-C10-alkyl 2-keto-L-gulonate is lactonized under acidic conditions in the presence of a water-miscible solvent and where this solvent in situ forms a solvent in which the ascorbic acid formed is poorly soluble.

Abstract: A reflection column which contains liquid distributors having at least 500 drip points/m2, which are arranged at an angle of about 90° C. to cloth layers of packing elements located immediately therebelow; and a combination of insulation and protective heating. The column is advantageously used for the rectification of mixtures of high-boiling air- or temperature-sensitive substances requiring effective separation efficiency.

Abstract: A process for preparing high-purity phytantriol, that includes rectifying the phytantriol which is obtained and is contaminated with lower and/or higher boiling byproducts under medium vacuum in rectification columns containing metal cloth packings with ordered structure using channel liquid distributors with a minimum of 500 drip points/m2, which are arranged at an angle of 90° to the cloth layers of the packing elements located directly below the distributors, in which 2 or more of the packing elements underneath the liquid distributors have only a small height, which ensure absolute exclusion of air and a strictly adiabatic procedure. The preparation of high-purity phytantriol takes place particularly advantageously when the phytantriol which is contaminated with byproducts is a phytantriol which has been obtained by reacting isophytol with performic acid and subsequently hydrolyzing the product formed in the reaction with alkaline agents in a manner known per se.

Abstract: A process for separating a liquid mixture of at least two components A and B which form an azeotrope with one another, optionally together with further components, comprises (i) distilling the mixture to be separated in the presence of an auxiliary H which with each of the two components A and B forms a binary azeotrope AH or BH which has a boiling point lower than that of H, and (ii) isolating an A,H-containing fraction which is depleted in B compared to the mixture to be separated and a B,H-containing fraction which is depleted in A compared to the mixture to be separated.

Abstract: A process for preparing alkali metal salts of L-ascorbic acid comprising the following steps: a) esterifying 2-keto-L-gulonic acid or diacetone-2-keto-L-gulonic acid with a C1-C10-alkohol in the presence of an acid catalyst, b) rearranging the resultant 2-keto-L-gulonic acid C1-C10-alkyl ester in the presence of an alkali metal C1-C10-alkoxide, comprises carrying out each of the process steps a) and b) continuously.

Abstract: Process for isolating pure substances from of mixtures of high-boiling air- and/or temperature-sensitive substances which require a high separation efficiency, by rectification under medium vacuum in columns containing metal cloth packings with ordered structure using channel liquid distributors with 500 or more drip points/m.sup.2, which are arranged at an angle of 90.degree. to the cloth layers of the packing elements located immediately below the distributors, in which two or more of the packing elements underneath the liquid distributors have only a very small height, which ensure virtual exclusion of air and are designed so that no heat exchange through the column wall can take place during the rectification. The patent also relates to packed columns which can be used for this process and to the use of this process and these columns for the final purification of vitamin E acetate by distillation.

Abstract: A process for preparing 2,5,6-trimethyl-2-cyclohexen-1-one by reacting diethyl ketone with crotonaldehyde or a compound which is converted under the chosen reaction conditions into crotonaldehyde, in the presence of basic agents at elevated temperature, which comprisesa) simultaneously pumping one mole of crotonaldehyde or one mole of a compound which is converted under the reaction conditions into crotonaldehyde, about 5 to 30 moles of diethyl ketone and the aqueous solution or suspension of a strong base, through separate lines or at least partly in the form of a suitable mixture, continuously into a pressure vessel, which is heated where appropriate and which ensures vigorous mixing, in such a way thatb) the reaction temperature is between 150.degree. C. and 350.degree. C., and the average residence time in the pressure vessel is only about 0.1 second to 20 minutes.

Abstract: Packing elements with a low pressure drop for mass transfer column internals of the internal diameter of the column and of a height of from 40 to 300 mm made of dimensionally stable layers, which have an ordered structure and are in mutual contact, of cloth material or cloth-like material with a specific surface area of from 100 to 2000 m.sup.2 /m.sup.3, whereina) the shaped layers of cloth material or cloth-like material, preferably made of metal cloth, which are in mutual contact are arranged so that they form a multiplicity of narrow flow channels, preferably virtually triangular, virtually rectangular or else virtually equilateral hexagonal flow channels, in which the angle of inclination of the serration of the individual cloth layers of the packing to the column axis is only 0 to 25.degree., preferably 3 to 14.degree.

Abstract: A process for preparing polyenecarbonyl compounds having a high all-E content and their acetals or ketals by aldol condensation or Horner-Emmons reaction comprises carrying out the reaction, for the purposes of the preferred formation of a double bond of E configuration and in order to maintain the E configuration of the double bonds in the stating compounds as completely as possible, in the presence of oxygen or an oxygen-inert gas mixture or nitric oxide or a nitric oxide-inert gas mixture and/or in the presence of specific stable radicals and/or in the presence of quinones or quinone derivatives.

Abstract: Veratryl cyanide is prepared by chloromethylating veratrol in solution in toluene and then reacting the resulting veratryl chloride with from 1 to 5 moles of an alkali metal cyanide, by a process in which the toluene from the chloromethylation is not removed for the reaction with cyanide, and from 3 to 25% by weight, based on veratryl chloride, of water, from 5 to 50% by weight, based on toluene, of a ketone of 3 to 6 carbon atoms and from 0.1 to 10% by weight, based on veratryl chloride, of a phase transfer catalyst are added before the reaction with cyanide.