Abstract: Particle fiber agglomerates comprise fibers having the structure of individual fibers, fiber bundles, fiber tufts or mixtures thereof with firmly adhering particles.

Abstract: A process for producing solids by precipitation in a mixer to form a mixture of solid and liquid, where the starting materials are fed into a mixing apparatus which has essentially a rotationally symmetrical mixing chamber which has a rotor disposed therein and is formed by a peripheral wall and two end walls, and where a) the starting materials are each fed to at least one inlet opening in the peripheral wall of the mixing chamber, and b) the solid-containing mixture which is formed is removed from at least one outlet opening in the peripheral wall of the mixing chamber.

Abstract: Catalysts comprising iron and potassium and, if desired, further elements, which catalysts are suitable for dehydrogenating hydrocarbons to give the corresponding olefinically unsaturated hydrocarbons, are prepared by calcining a finely divided dry or aqueous mixture of an iron compound with a potassium compound and, if desired, compounds of further elements in a first step that agglomerates having a diameter of from 5 to 50 .mu.m and formed from smaller individual particles are obtained and, in a second step, preferably after shaping, calcining it at from 300 to 1000.degree. C., with the maximum calcination temperature in the second step preferably being at least 30.degree. below the calcination temperature in the first step. The catalysts thus prepared are useful, in particular, for dehydrogenating ethylbenzene to give styrene.

Abstract: Catalysts for the oxidation of sulfur dioxide to sulfur trioxide, consisting of a silica-based carrier and, applied on this, an active substance containing vanadium and alkali metal compounds, are prepared by dissolving vanadium pentoxide in an alkali solution, acidifying the solution with sulfuric acid, mixing the acidified solution with the carrier, molding the mixture and drying and calcining the molding. To obtain mechanically stable catalysts, a dissolved alkali metal silicate and/or silica sol are added to the alkaline solution before acidification, the latter process is carried out at below 35.degree. C. and the solution is then immediately incorporated into the carrier. The resulting moist crumbly material contains from 2 to 6% by weight of V.sub.2 O.sub.5, from 35 to 45% by weight of H.sub.2 O and from 15 to 50% by weight of SiO.sub.2. From 5 to 25% by weight of the total silica content originates from the dissolved alkali metal silicate and/or silica sol.

Abstract: A process for the manufacture of symmetrical dialkylureas by reacting monoalkylamines with CO.sub.2 at an elevated temperature and under superatmospheric pressure, in which the unconverted starting materials, water and the by-products formed in the reaction zone, as well as alkylamine alkylcarbamate, after thermal decomposition into monoalkylamine, CO.sub.2 and water, are separated from the dialkylurea formed, and thereafter a part of the unconverted starting materials plus by-products, with or without water, may or may not be recycled to the reaction zone, before isolating an aqueous solution, containing monoalkylamines, CO.sub.2 and other by-products, which solution is treated with alkali metal hydroxide solution in a column, the monoalkylamine, after separation from carbon dioxide and water, being recycled to the reaction zone. The dialkylureas obtained contain not more than 1% of monoalkylurea and 1% of trialkylurea, and may be used as starting materials for various syntheses.