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Werner Steck

Helmut Jakusch

Werner Loeser

Manfred Ohlinger

Peter Rudolf

Eberhard Koester

Wilhelm Sarnecki

Rainer Feser

Guenter Vaeth

Christof Jaeckh

Laszlo Marosi

Jenoe Kovacs

Gerd Wunsch

Paul Deigner

Horst Autzen

Ekkehard Schwab

Helmut Lermer

Werner Huebner

Rudolf Brodt

Matthias Schwarzmann

Harald Rust

Karl Uhl

Hans Henning Schneehage

Herbert Haberkorn

Volker Arndt

Franz Merger

Toni Dockner

Hardo Siegel

Werner Balz

Helmut Auweter

Hermann Roller

Herbert Motz

Roland Falk

Eduard Schoenafinger

Franz-Josef Mueller

Michael W Mueller

Norbert Mueller

Joachim Stabenow

Eckhard Hetzel

Peter Felleisen

Heinz Stritzinger

Gunther Mair

Gerhard Fritz

Friedrich Domas

Fritz Naeumann

Manfred Steuerwald

Klaus-Dieter Hoppe

Werner Stumpfi

Werner Senkpiel

Karl Mahler

Udo Kullmann

Hans-Juergen Becker

Hans H Reich

Kalus-Dieter Hoppe

Dieter Graw

Kurt Weinacht

Hansjoerg Siegle

Bernd Meyer

Wilhelm Schloesser

A method of isomerizing propargyl alcohol to acrolein, wherein propargyl alcohol is rearranged in the gas phase at a temperature of from 300.degree. to 550.degree. C. and a pressure of from 0.01 to 50 bar and in contact with a heterogeneous catalyst containing alkaline-reacting metal ions, and the use of propargyl alcohol as a depot substance for the liberation of acrolein.

Process for the preparation of acrolein

A process for the preparation of mixtures of isomeric cresols with a molar ratio of para- to meta-cresol of from 0.6:1 to 10:1 by isomerization of cresol mixtures or ortho- and/or metal-cresol on zeolite catalysts of the pentasil type in the gas phase at from 300.degree. to 600.degree. C. under from 0.01 to 50 bar entails the mean particle size of the zeolite catalyst being at leat 3 .mu.m, and the selectivity in the established test for the disproportionation of ethylbenzene to diethylbenzene isomers being at least 60% for para-diethylbenzene.

Preparation of mixtures of isomeric cresols with a molar ratio of para-

Acicular ferromagnetic chromium dioxide is stabilized by treatment with an alkali metal hydroxide in an aqueous alkaline suspension at elevated temperatures.

Stabilization of acicular ferromagnetic chromium dioxide

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.

Separation of ortho-, meta- and para-tolunitrile from ternary mixtures

Hydroxybenzaldehydes of the formula (I) are prepared from a benzaldehyde of the formula (II) or its acetal, in which R.sup.1 in the R.sup.1 O-phenyl ether group is an alkyl, cycloalkyl, alkylcycloalkyl or alkylaryl radical, R.sup.2 is H or OH or is identical to R.sup.1 and one or more R.sup.1 O-phenyl ether groups are ortho, meta or para to the aldehyde function, by a process in which a benzaldehyde of the formula (II) or its acetal, in which R.sup.1 and R.sup.2 have the abovementioned meanings and one or more R.sup.1 O-phenyl ether groups occupy the abovementioned position with respect to the aldehyde function, is converted into a hydroxybenzaldehyde of the formula (I) in the presence of water over a zeolite as a heterogeneous catalyst. ##STR1## The catalysts used are, in particular, zeolites of the pentasil type.

Preparation of hydroxybenzaldehydes

Acicular, ferromagnetic metal particles which essentially consist of iron and have a nickel content of not more than 0.4% by weight and high values for coercive force and magnetization, and a process for the preparation of these particles. The particles further include zinc, phosphorus in the form of phosphate ions, and silicon in the form of SiO.sub.2.

Acicular, ferromagnetic metal particles essentially consisting of iron,

Ferromagnetic metal particles of substantially iron are prepared by starting from an acicular .alpha.-FeOOH, applying a shape-stabilizing finish to the particle surface, heating at 500.degree.-850.degree. C. and subsequently reducing with gaseous reducing agents at 200.degree.-500.degree. C. to the metal, and starting .alpha.-FeOOH being prepared in the presence of zinc and phosphate ions.

Preparation of acicular ferromagnetic metal particles of substantially

Finely divided, acicular and pore-free .alpha.-Fe.sub.2 O.sub.3 is prepared from iron(III) salts in the presence of one or more organic substances which form complexes with iron(III) ions, in alkaline suspension, at from 80.degree. to 250.degree. C.

Preparation of acicular .alpha.-Fe.sub.2 O.sub.3

Superparamagnetic solid particles of the general formula I

Superparamagnetic solid particles

Ferromagnetic chromium dioxide is improved by subjecting chromium dioxide materials prepared by a known method to an additional heat treatment.

Preparation of ferromagnetic chromium dioxide

Acicular .alpha.-Fe.sub.2 O.sub.3 is prepared from iron(III) salts by heating an alkaline aqueous suspension of iron(III) hydroxide in the presence of one or more organic substances which form complexes with iron(III) ions to a temperature of 100.degree. C. or less.

Preparation of acicular alpha-Fe.sub.2 O.sub.3

Acicular, magnetic iron oxide consisting of a core of gamma-iron(III) oxide and a ferrite shell containing a total of from 0.4 to 12% by weight of cobalt(II) ions and from 0.1 to 15% by weight of iron(II) ions, the percentages being based on the total amount of magnetic material, is prepared by a process in which an iron(II) hydroxide precipitate is applied to the gamma-iron(III) oxide core in a first stage and an iron-(II)/cobalt hydroxide precipitate is applied to the said core in a second stage, and the core is then converted to the ferrite shell by oxidation.

Preparation of cobalt-containing, acicular, magnetic iron oxides

The preparation of acicular ferrimagnetic iron oxides which contain cobalt and phosphate ions and, if desired, further additives, and their use for manufacturing magnetic recording media.

Preparation of acicular cobalt-containing ferrimagnetic iron oxides

A process for the preparation of cobalt-containing isotropic magnetic iron oxides which are based on gamma-iron(III) oxide, contain from 2 to 7% by weight of cobalt(II) ions and less than 2% by weight of Fe(II) ions, the percentages in each case being based on the iron oxide, and have a particle length of from 0.08 to 0.30 .mu.m, a length/width ratio of from 1.5 to 3.5:1 and a specific remanent magnetization after saturation of not less than 60 nTm.sup.3 /g.

Preparation of cobalt-containing isotropic magnetic iron oxides

Acicular metal particles consisting essentially of iron are prepared by reducing .alpha.-iron(III) oxide obtained--by dehydration--from acicular iron(III) oxide hydroxide prepared in the presence of phosphate ions and having a shape-stabilizing surface coating.

Preparation of acicular ferromagnetic metal particles consisting

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