Hoechst Aktiengesellschaft

Other

Daimlerchrysler Corporation

Rohm Gmbh

Friedrich-Alexander-Universitat Erlangen-Nürnberg

Daimler Ag

Gerhard Emig

Karl-Friedrich Muck

Karlheinz Burg

Michael Hoffmockel

Gunter Sextro

Frank Kern

Horst-Philipp Beck

Gunther Wiesgickl

Benno Kruger

Kolja Rebstock

Klaus Langerbeins

Horst Linn

Wolfgang Ruppert

Ruediger Jelitte

Otto Watzenberger

Volker Wunder

Nadejda Popovska

Helmut Gerhard

A method for manufacturing coated short fibers, in which the short fibers are coated in a reactor with at least one coating agent. The method includes exposing a short fiber bundle having a coating or a plastic matrix to a high-frequency field which dissolves the coating or the plastic matrix. The fiber bundle is separated into individual fibers and are coated by chemical vapor deposition on all sides by at least one coating agent present in a gas phase. A combination of mechanical and microwave treatment is preferably provided to loosen the short fiber bundles.

Method for manufacturing coated short fibers

The process serves for the preparation of trioxane from formaldehyde in the gas phase in the presence of a tungstomolybdophosphoric acid of the composition H.sub.3 PW.sub.n Mo.sub.m O.sub.40 .multidot.xH.sub.2 O (n=4-8, m=12-n; x=0-32) as catalyst.

Process for preparing trioxane

In a process for the preparation of trioxane from formaldehyde in the gas phase in the presence of a catalyst, the catalyst employed is 11-molybdo-1-vanadophosphoric acid, H.sub.4 PVMo.sub.11 O.sub.40 .multidot.n H.sub.2 O (n=0-32). Advantages of this process are, inter alia, high space-time yields and the suppression of byproducts.

Process for the preparation of trioxane

A process for the catalytic preparation of trioxane from formaldehyde in the gas phase employs a catalyst comprising vanadyl hydrogenphosphate hemihydrate which may be unactivated or activated by steam. No byproducts were obtained in the process and the space-time yield is high. Deposits in the reactor do not occur.

The invention relates to the stabilization of the activity and/or the reactivation of molybdoheteropoly acid catalysts in vapor-phase oxidations, such as the oxidehydrogenation of isobutyric acid or its lower esters to methacrylic acid or its lower esters, by means of an oxidizing treatment of the catalyst in which compounds of catalyst constituents are added, at temperatures ranging from 200.degree. to 400.degree. C., with an oxygen-containing gas. The inventive activation measures can be carried out either during the catalytic vapor-phase reaction, such as oxihydrogenation in particular, or intermittently to alternate therewith, and optionally also physically separated in part from each other.

Method for the catalytic vapor phase oxydehydrogenation of isobutyric

Silicate catalysts which can be employed for selective oxidation reactions of organic substances, a process for the preparation of these catalysts and their use are described. The catalyst is distinguished by high long-term activity, by the reaction temperature required for the reaction being lower in comparison with catalysts composed of pure silver and by higher conversions and selectivities in the oxidative dehydrogenation of alkanols in comparison with pure silver or silver on supports.

Catalyst for selective oxidation reactions

A process for the preparation of carbonyl compounds by the oxydehydrogenation of (C.sub.1 -C.sub.4)-alcohols is carried out at a temperature from 400.degree. to 700.degree. C. in the presence of a silicate catalyst which has been doped with silver and silver ions. By means of the process carried out at relatively low temperatures, for example, are that high yields are achieved, the content of carbon monoxide is low and the product gas contains, apart from carbon dioxide, no further determinable by-products and has a low water/formaldehyde ratio.

Process for the preparation of carbonyl compounds

The process dehydrogenates methanol in the presence of a catalyst based on aluminum oxide, alkali metal aluminate and/or alkaline earth metal aluminate with the exclusion of oxygen at a temperature of 650.degree. to 1050.degree. C. in a reactor whose inner wall is composed entirely or partly of aluminum oxide. The process gives anhydrous formaldehyde which contains only very minor impurities.

Growing community of inventors

Erlangen, Germany

Gerhard Emig