Abstract: Reactions between at least two fluid reactants are performed in a reactor comprising wall elements (1), slot-shaped reaction spaces (3) and cavities (5) for conducting a fluid heat-carrier through. Depending on the process and throughput, a modular structural design is chosen wherein an arbitrary number of wall elements (1) are assembled to a right-parallelepipedal block (24), the reaction spaces (3) are formed between lateral surfaces (2) of right-parallelepipedal wall elements (1), the reactants are introduced into the reaction spaces (3) from edge regions of one side of the block (24) and are conducted through the reaction spaces (3) in parallel flows and the fluid heat-carrier is conducted through the tubular cavities (5) extending in the interior of the wall elements (1).

Abstract: Silicon-titanium mixed oxide powder prepared by flame hydrolysis, having a ratio by weight of silicon dioxide/titanium dioxide, which is greater on the surface of the primary particles than that within the total primary particle. It is prepared by a flame hydrolysis process, in that a stream consisting of a vaporous titanium dioxide precursor and oxygen or an oxygen-containing gas and hydrogen, and a second stream consisting of a vaporous silicon dioxide precursor and a carrier gas consisting of oxygen, an oxygen-containing gas and/or an inert gas, are guided separately into the reaction chamber of a burner such as is known for the preparation of pyrogenic oxides, and are burnt here, the solid mixed oxide powder and hot gases are subsequently cooled, and the gases are separated from the solid. The powder may be used, for example, for the preparation of sunscreen preparations.

Abstract: Pyrogenically prepared titanium dioxide doped by means of an aerosol contains an oxide from the group zinc oxide, platinum oxide, magnesium oxide and/or aluminium oxide as the doping component. It is prepared as follows: in the pyrogenic preparation of titanium dioxide, a metal salt solution is atomised to form an aerosol and injected into the production stream. The titanium dioxide may be used as a photocatalyst or as a UV adsorber or in processes for purification of waste water or waste air/gases.

Abstract: Aluminium oxide doped with a divalent metal oxide, produced by flame hydrolysis and which has no spinell structures or alpha-aluminium detectable in an x-ray diffractogram. It is produced by a pyrogenic process in which, during the flame hydrolysis of aluminium halogenides, an aerosol, which contains an aqueous solution of a divalent metal salt is added to the gas mixture. The doped aluminium oxides can be used in aqueous dispersions for chemical-mechanical polishing.

Abstract: Iron oxide-silicon dioxide-titanium dioxide mixed oxide is produced by burning vaporizable compounds of iron, silicon and titanium together in a hydrogen/oxygen flame. The mixed oxides may be used as UV absorbers in cosmetics.

Abstract: Pyrogenically prepared titanium dioxide doped by means of an aerosol contains an oxide from the group zinc oxide, platinum oxide, magnesium oxide and/or aluminium oxide as the doping component. It is prepared as follows: in the pyrogenic preparation of titanium dioxide, a metal salt solution is atomised to form an aerosol and injected into the production stream. The titanium dioxide may be used as a photocatalyst or as a UV adsorber.

Abstract: A process for the preparation of doped, pyrogenically prepared titanium dioxide is described. The titanium dioxide is doped with zinc oxide, platinum oxide, magnesium oxide, or aluminium oxide, by injecting an aerosol of the oxide into the production stream. The doped titanium dioxide may be used as a photocatalyst or UV absorber.

Abstract: Silicon-titanium mixed oxide powder prepared by flame hydrolysis, having a ratio by weight of silicon dioxide/titanium dioxide, which is greater on the surface of the primary particles than that within the total primary particle. It is prepared by a flame hydrolysis process, in that a stream consisting of a vaporous titanium dioxide precursor and oxygen or an oxygen-containing gas and hydrogen, and a second stream consisting of a vaporous silicon dioxide precursor and a carrier gas consisting of oxygen, an oxygen-containing gas and/or an inert gas, are guided separately into the reaction chamber of a burner such as is known for the preparation of pyrogenic oxides, and are burnt here, the solid mixed oxide powder and hot gases are subsequently cooled, and the gases are separated from the solid. The powder may be used, for example, for the preparation of sunscreen preparations.

Abstract: Iron oxide-silicon dioxide-titanium dioxide mixed oxide is produced by burning vapourable compounds of iron, silicon and titanium together in a hydrogen/oxygen flame.

Abstract: Iron oxide-silicon dioxide-titanium dioxide mixed oxide is produced by burning vapourable compounds of iron, silicon and titanium together in a hydrogen/oxygen flame. The mixed oxides may be used as UV absorbers in cosmetics.

Abstract: A process for photocatalytic removal of organic substances from waste waters, wherein by way of photocatalyst use is made of granulates based on pyrogenically prepared titanium dioxide having the following physicochemical characteristic data: Mean grain diameter: 10 to 150 &mgr;m BET surface: 25 to 100 m2/g pH value: 3 to 6 Compacted bulk density: 100 to 1,200 g/l.

Abstract: Iron oxide-silicon dioxide-titanium dioxide mixed oxide is produced by burning vapourable compounds of iron, silicon and titanium together in a hydrogen/oxygen flame. They are used as UV absorbers in cosmetics.

Abstract: A process for the direct synthesis of hydrogen peroxide from hydrogen and oxygen is carried out in the presence of a noble metal catalyst. The selectivity for H2 and/or the maximum H2O2 concentration can be increased by using a catalyst of palladium or at least two metals selected from Group VIII and Group I of the Periodic Table of Elements, which catalyst has been produced by spray pyrolysis or flame pyrolysis.

Abstract: Reactions between at least two fluid reactants are performed in a reactor comprising wall elements (1), slot-shaped reaction spaces (3) and cavities (5) for conducting a fluid heatcarrier through. Depending on the process and throughput, a modular structural design is chosen wherein an arbitrary number of wall elements (1) are assembled to a right-parallelepipedal block (24), the reaction spaces (3) are formed between lateral surfaces (2) of right-parallelepipedal wall elements (1), the reactants are introduced into the reaction spaces (3) from edge regions of one side of the block (24) and are conducted through the reaction spaces (3) in parallel flows and the fluid heat-carrier is conducted through the tubular cavities (5) extending in the interior of the wall elements (1).

Abstract: A process for photocatalytic removal of organic substances from waste waters, wherein by way of photocatalyst use is made of granulates based on pyrogenically prepared titanium dioxide having the following physicochemical characteristic data: 1 Mean grain diameter: 10 to 150 &mgr;m BET surface: 25 to 100 m2/g pH value: 3 to 6 Compacted bulk density: 100 to 1,200 g/l.

Abstract: Pyrogenically prepared titanium dioxide doped by means of an aerosol contains an oxide from the group zinc oxide, platinum oxide, magnesium oxide and/or aluminum oxide as the doping component.

Abstract: The invention is relative to a method of producing hydrogen peroxide by direct synthesis in which hydrogen and oxygen are reacted in the presence of a heterogeneous, carrier-free or carrier-bound catalyst containing at least one noble metal in the presence or absence of a solvent and to a catalyst for carrying out the method.

Abstract: An aqueous solution of hydrogen peroxide is produced by direct synthesis from hydrogen and oxygen in the presence of a heterogeneous catalyst. According to the invention, a gas mixture comprising H.sub.2 and O.sub.2, essentially saturated or supersaturated with water (=containing fog) is fed into a reactor containing the catalyst. The volume ratio of the gas mixture fed in (standard liters per hour) to liquid removed (liters per hour) is adjusted to a value equal to or greater than 15,000, especially 20,000 to 50,000, and the gas mixture leaving the reactor is recycled after replenishment with H.sub.2, O.sub.2, and H.sub.2 O vapor. Solutions with high H.sub.2 O.sub.2 concentration can be obtained according to the invention without additional concentration.