Abstract:
The present application relates to a process for reacting a composition I comprising at least one aldehyde with hydrogen in the presence of a catalyst in at least one main reactor and at least one postreactor, wherein at least 50% of the fresh hydrogen fed to the reaction system is fed into at least one postreactor. In a preferred embodiment, composition I comprises at least one further organic compound.
Abstract:
A process for working up by distillation the crude products obtained in the process according to DE-A 196 07 954 and containing 1,6-hexanediol (HDO), 1,5-pentanediol (PDO) or caprolactone (CLO) in order to obtain the corresponding pure products, the working-up by distillation being carried out in each case in a dividing wall column (TK) in which a dividing wall (T) is arranged in the longitudinal direction of the column with formation of an upper common column region (1), a lower common column region (6), a feed section (2, 4) having a rectification section (2) and stripping section (4), and a take-off section (3, 5) having a stripping section (3) and rectification section (5), with feeding of the respective crude product HDO, PLO or CLO in the middle region of the feed section (2, 4) and removal of the high boiler fraction (C) from the bottom of the column, of the low boiler fraction (A) via the top of the column and of the medium boiler fraction (B) from the middle region of the take-off section (3, 5), or in thermally coupled columns.
Abstract:
The present invention relates to a process for preparing 5-alkoxy-substituted oxazoles, in particular for preparing 4-methyl-5-alkoxy-substituted oxazoles and also a process for preparing pyridoxine derivatives.
Abstract:
The present invention relates to a process for continuously preparing 5-alkoxy-substituted oxazoles, in particular for continuously preparing 4-methyl-5-alkoxy-substituted oxazoles and also a process for preparing pyridoxine derivatives.
Abstract:
A process is disclosed for the purification, by distillation, of trimethylolpropane originating from the hydrogenation of 2,2-dimethylolbutanal, said process including the following steps: (a) reaction of n-butyraldehyde with formaldehyde in the presence of catalytic amounts of a tertiary amine, and hydrogenation of the resulting mixture to give a mixture containing trimethylolpropane; (b) separation of water, methanol, trialkylamine and/or trialkylammonium formate by distillation; (c) heating of the residue obtained in (b) under reduced pressure to a temperature at which TMP is volatile and compounds boiling above TMP are cleaved, in order to separate off, by distillation, TMP and compounds more volatile than TMP; (d) distillation of the distillate obtained in (c) in order to separate off the more volatile compounds and recover pure TMP; and (e) optional distillation of the TMP obtained in (d) in order to recover TMP with a low APHA color index. A process is also disclosed in which trialkylammonium formate is distilled under mild conditions from crude mixtures of polyhydric alcohols, predominantly trimethylolpropane.
Abstract:
A process for purifying crude piperidines of the formula I ##STR1## where R.sup.1 to R.sup.4 are C.sub.1 -C.sub.6 -alkyl, or R.sup.1 and R.sup.2 and/or R.sup.3 and R.sup.4 together are a CH.sub.2 -chain of 2 to 5 carbons, which comprises, in a first step, removing high-boiling substances and, if present, water from the crude piperidines by distillation; in a second step, adding from 0.01 to 5% by weight, based on the product of the first step, as a reducing agent; and, in a third step, isolating the piperidines by distillation.
Abstract:
A process for the separation of ortho-, meta- and para-tolunitrile from ternary mixtures of isomers entails removing ortho-tolunitrile from these mixtures by distillation under pressures of from 10.sup.2 and 10.sup.5 Pa and with a reflux ratio of from 1:1 to 200:1, and distilling the remaining binary mixture of meta- and para-tolunitrile to concentrate to more than 75 mol-% para-tolunitrile, and freezing out the paratolunitrile at below 26.degree. C., and a process for the preparation of suitable ternary mixtures of isomers entails isomerization of pure ortho-, meta- or para-tolunitrile or mixtures thereof at from 380.degree. to 580.degree. C. on zeolite catalysts.