Abstract: A process for preparing impact-modified styrene polymers (HIPS) omprises anionic polymerization of styrene in the presence of a rubber in one or more polymerization reactors in succession. The rubber is prepared in solution in an immediately upstream process. The heat of polymerization is utilized to remove the solvent for the rubber, this solvent having a boiling point lower than those of styrene and ethylbenzene, from at least one of the polymerization reactors via distillation with distillative cooling, and the solvent is reintroduced into the process of rubber preparation.

Abstract: Alkenylaromatics are produced by catalytic oxidative dehydrogenation of alkylaromatics employing a redox catalyst which is bismuth oxide, in combination with an additive compound of an alkali metal and/or an alkaline earth metal, on a titanium diooxide carrier. In a first reaction step, an alkylaromatic starting material is oxidatively dehydrogenated with the redox catalyst in the absence of molecular oxygen with attending reduction of the redox catalyst. In a second reaction step, the reduced redox catalyst is reoxidized with an oxygen-containing gas.

Abstract: In a process for preparing olefinically unsaturated compounds such as styrene by oxidative dehydrogenation of corresponding hydrocarbons using a previously oxidized oxygen transferer acting as catalyst in the absence of molecular oxygen and reoxidation of the oxygen transferer in at least two reactors, the dehydrogenation and regeneration takes place alternately in time in the two reactors and the reactors are connected to one another in terms of heat via heat exchangers and a common circuit for heat transfer medium.

Abstract: A process for the dehydrogenation of ethylbenzene to styrene with input of heat by a heat-transfer medium on a dehydrogenation catalyst which is essentially located in a tube bundle, wherein the heat-transfer medium flows countercurrently to the reaction mixture in the region of the tube bundle, and, if required, another reaction chamber is located downstream of the tube bundle and is provided with a catalyst for adiabatic reaction.

Abstract: A process for the preparation of olefinically unsaturated compounds by catalytic oxidation, ie oxidative dehydrogenation by transferring oxygen from a previously oxidized oxygen carrier acting as catalyst, in the absence of molecular oxygen, the catalyst being regenerated after exhaustion, wherein, during the operating phase of the catalyst (oxidation/dehydration partial step), the residence time, space velocity and/or temperature of the reactants in the reactor is/are adjusted, ie, controlled, continuously or in discrete steps, in a manner appropiate to the momentary state of activity of the redox catalyst by adjusting--continuously or stepwise--the residence time of the reactants in the freshly regenerated catalyst (ie at the commencement of the reaction) to a shorter time, and/or the temperature to a lower value, than the corresponding parameter(s) in the partially reduced catalyst.

Abstract: A regenerative process for the preparation of olefinically unsaturated compounds by oxidation/dehydrogenation of selectively oxidizable hydrocarbons over an oxygen carrier acting as catalyst, in the absence of molecular oxygen, alternating (in repeated cycles) with regeneration of the spent oxygen carrier with a gaseous molecular oxidizing agent, in which the spent (reduced) catalyst is cooled, prior to introduction of the regenerating gas, to a temperature which is below the temperature of the reaction, regeneration being controlled in such a manner that the highest temperature occurring during regeneration does not exceed the temperature of reaction at which dehydrogenation is commenced.

Abstract: Apparatus, in particular reactor for carrying out endothermic catalytically promoted gas-phase reactions, which has, arranged one on top of the other or one inside the other in a common jacket, a tube-bundle heat exchanger 1 consisting of a plurality of parallel tubes provided with baffles 1a securing a flow of the heat exchanging medium in a direction transverse to the axis of said tubes, a reaction space 6 which preferably widens conically upward, has a base and is intended for holding a catalyst bed, a tube-bundle heat exchanger 2 to which material flows laterally and which is provided with baffles 2a, a reaction space 4 which has a base, is closed at the top by a gas dome and is intended for holding a catalyst bed, a central tube 3 for connecting the outer space of the heat exchanger 1 to the gas space above the reaction space 4, and inlet and outlet means for a heating or cooling gas (c) and inlet and outlet means (a or b) for the fresh gas or reaction mixture, respectively.

Abstract: A process for the preparation of iron-, potassium- and cerium-containing catalysts for the dehydrogenation of hydrocarbons from the same spent catalysts (regeneration) by grinding and, if necessary, purifying the spent material, restoring the original activity by adjusting the composition and restoring the external shape comprises adding to the ground material an effective amount of potassium and such an amount of cerium that the total amount of cerium is greater than the amount originally present.