Abstract: The invention relates to a process for preparing butadiene from n-butenes in n reactors R1 to Rn operated in parallel, wherein the process in the production phase of a reactor Rm in the n reactors comprises the steps: A) provision of a feed gas stream a1m comprising n-butenes; B) feeding of the feed gas stream a1m comprising n-butenes, an oxygen-comprising gas stream a2m and a substream d2m of an oxygen-comprising total recycle gas stream d2 into the oxidative dehydrogenation zone of the reactor and oxidative dehydrogenation of n-butenes to butadiene, giving a product gas substream bm comprising butadiene; C) combination of the product gas substream bm with further product gas substreams to form a total product gas stream b and cooling and compression of the total product gas stream b and condensation of at least part of the high-boiling secondary components, giving at least one aqueous condensate stream c1 and a gas stream c2 comprising butadiene; D) feeding of the gas stream c2 into an absorption zone an

Abstract: Process for preparing butadiene from n-butenes, which has a start-up phase and an operating phase and the operating phase of the process comprises the steps: A) provision of a feed gas stream a1 comprising n-butenes; B) introduction of the feed gas stream a1 comprising n-butenes, an oxygen-comprising gas stream a2 and an oxygen-comprising recycle gas stream d2 into at least one oxidative dehydrogenation zone and oxidative dehydrogenation of n-butenes to butadiene, giving a product gas stream b comprising butadiene; C) cooling and compression of the product gas stream b, giving at least one aqueous condensate stream c1 and a gas stream c2 comprising butadiene; D) introduction of the gas stream c2 into an absorption zone and separation of incondensable and low-boiling gas constituents as gas stream d from the gas stream c2 by absorption of the C4 hydrocarbons in an absorption medium, giving an absorption medium stream loaded with C4 hydrocarbons and the gas stream d, and recirculation of the gas stream d as re

Abstract: The invention relates to a process for preparing 1,3-butadiene from n-butenes, comprising the steps of: A) providing an input gas stream a comprising butanes, 1-butene, 2-butene and isobutene, with or without 1,3-butadiene, from a fluid catalytic cracking plant; B) removing isobutene from the input gas stream a, giving a stream b comprising butanes, 1-butene and 2-butene, with or without 1,3-butadiene; C) feeding the stream b comprising butanes, 1-butene and 2-butene and optionally an, oxygenous gas and optionally water vapor into at least one dehydrogenating zone and dehydrogenating 1-butene and 2-butene to 1,3-butadiene, giving a product gas stream c comprising 1,3-butadiene, butanes, 2-butene and water vapor, with or without oxygen, with low-boiling hydrocarbons, with high-boiling secondary components, with or without carbon oxides and with or without inert gases; D) cooling and compressing the product gas stream c, giving at least one aqueous condensate stream d1 and a gas stream d2 comprising 1,3-buta

Abstract: The invention relates to a process for preparing 1,3-butadiene from n-butenes, comprising the steps of: A) providing an input gas stream a comprising butanes, 1-butene, 2-butene and isobutene, with or without 1,3-butadiene, from a fluid catalytic cracking plant; B) removing isobutene from the input gas stream a, giving a stream b comprising butanes, 1-butene and 2-butene, with or without 1,3-butadiene; C) feeding the stream b comprising butanes, 1-butene and 2-butene and optionally an, oxygenous gas and optionally water vapor into at least one dehydrogenating zone and dehydrogenating 1-butene and 2-butene to 1,3-butadiene, giving a product gas stream c comprising 1,3-butadiene, butanes, 2-butene and water vapor, with or without oxygen, with low-boiling hydrocarbons, with high-boiling secondary components, with or without carbon oxides and with or without inert gases; D) cooling and compressing the product gas stream c, giving at least one aqueous condensate stream d1 and a gas stream d2 comprising 1,3-buta

Abstract: Process for producing a multimetal oxide catalyst comprising molybdenum, chromium and at least one further metal by mixing of a pulverulent multimetal oxide comprising molybdenum and at least one further metal but no chromium with pulverulent chromium(III) oxide and thermal treatment of the resulting pulverulent mixture in the presence of oxygen at a temperature in the range from 350° C. to 650° C.