Abstract:
The invention relates to a process for the oxidative dehydrogenation of n-butenes to butadiene, which comprises two or more production steps (i) and at least one regeneration step (ii) and in which (i) a starting gas mixture comprising n-butenes is mixed with an oxygen-comprising gas in a production step and the mixed gas is brought into contact with a multimetal oxide catalyst which comprises at least molybdenum and a further metal and is arranged in a fixed catalyst bed at a temperature of from 220 to 490° C. in a fixed-bed reactor, with a product gas mixture comprising at least butadiene, oxygen and water vapor being obtained at the outlet of the fixed-bed reactor, and (ii) the multimetal oxide catalyst is regenerated in a regeneration step by passing an oxygen-comprising regeneration gas mixture over the fixed catalyst bed at a temperature of from 200 to 450° C. and burning off the carbon deposited on the catalyst, with a regeneration step (ii) being carried out between two production steps (i), wherein the oxygen content in the product gas mixture at the outlet of the fixed-bed reactor is at least 5% by volume and the duration of a production step (i) is not more than 1000 hours.
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-butadiene, butanes, 2-butene and water vapor, with or without oxygen, with low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases; Ea) removing uncondensable and low-boiling gas constituents comprising low-boiling hydrocarbons, with or without oxygen, with or without carbon oxides and with or without inert gases, as gas stream e2 from the gas stream d2 by absorbing the C4 hydrocarbons comprising 1,3-butadiene, butanes and 2-butene in an absorbent, giving an absorbent stream laden with C4 hydrocarbons and the gas stream e2, and Eb) subsequently desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 hydrocarbon stream e1; F) separating the C4 hydrocarbon stream e1 by extractive distillation with a 1,3-butadiene-selective solvent into a stream f1 comprising 1,3-butadiene and the selective solvent and a stream f2 comprising butanes and 2-butene, wherein at least 90% of the 1-butene present in stream b is converted in step C) and a product stream f2 comprising butanes and 2-butene is obtained in step F.
Abstract:
A process for preparing butadiene from n-butenes, comprising the steps of A) providing an input gas stream a1 comprising n-butenes; B) feeding the input gas stream a1 comprising n-butenes, an oxygenous gas and an oxygenous cycle gas stream a2 into at least one oxidative dehydrogenation zone and oxidatively dehydrogenating n-butenes to butadiene, giving a product gas stream b comprising butadiene, unconverted n-butenes, steam, oxygen, low-boiling hydrocarbons and high-boiling secondary components, with or without carbon oxides and with or without inert gases; Ca) cooling the product gas stream b and optionally at least partly removing high-boiling secondary components and steam, giving a product gas stream b′, Cb) compressing and cooling the product gas stream b′ in at least one compression and cooling stage, giving at least one aqueous condensate stream c1 and one gas stream c2 comprising butadiene, n-butenes, steam, oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases, Da) absorbing the C4 hydrocarbons comprising butadiene and n-butenes in an aromatic hydrocarbon solvent as an absorbent and removing uncondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, any carbon oxides, aromatic hydrocarbon solvent and any inert gases as gas stream d2 from the gas stream c2, giving an absorbent stream laden with C4 hydrocarbons and the gas stream d2, and then desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream d1, Db) at least partly recycling the gas stream d2 as cycle gas stream a2 into the oxidative dehydrogenation zone, wherein the content of aromatic hydrocarbon solvent in the cycle gas stream a2 is limited to less than 1% by volume.
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.
Abstract:
The invention relates to a process for preparing butadiene from n-butenes, comprising the steps of: A) providing an input gas stream a comprising n-butenes, B) feeding the input gas stream a comprising n-butenes and a gas containing at least oxygen into at least one oxidative dehydrogenation zone and oxidatively dehydrogenating n-butenes to butadiene, giving a product gas stream b comprising butadiene, unconverted n-butenes, water vapor, oxygen, low-boiling hydrocarbons and high-boiling secondary components, with or without carbon oxides and with or without inert gases; Ca) cooling the product gas stream b by contacting with a cooling medium in at least one cooling zone, the cooling medium being at least partly recycled and having an aqueous phase and an organic phase of an organic solvent, wherein the organic solvent is selected from the group consisting of toluene, o-, m- and p-xylene, mesitylene, mono-, di- and triethylbenzene, mono-, di- and triisopropylbenzene and mixtures thereof, and the mass ratio of the aqueous phase to the organic phase in the cooling medium when it is fed into the cooling zones prior to the contacting with the product gas stream being from 0.015:1 to 10:1, Cb) compressing the cooled product gas stream b which may have been depleted of high-boiling secondary components in at least one compression stage, giving at least one aqueous condensate stream c1 and one gas stream c2 comprising butadiene, n-butenes, water vapor, oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases; D) removing uncondensable and low-boiling gas constituents comprising oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases, as gas stream d2 from the gas stream c2 by absorbing the C4 hydrocarbons comprising butadiene and n-butenes in an absorbent, giving an absorbent stream laden with C4 hydrocarbons and the gas stream d2, and then desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream d1, E) separating the C4 product stream d1 by extractive distillation with a butadiene-selective solvent into a stream e1 comprising butadiene and the selective solvent and a stream e2 comprising n-butenes; F) distilling the stream e1 comprising butadiene and the selective solvent into a stream f1 consisting essentially of the selective solvent and a stream f2 comprising butadiene.
Abstract:
A process for oxidative dehydrogenation of n-butenes to 1,3-butadiene in a fixed-bed reactor (R), which comprises at least two production steps (i) and at least one regeneration step (ii), and in which in a production step (i), a starting gas mixture (1) comprising the n-butenes is mixed with an oxygen-comprising gas (2) and brought into contact with a heterogeneous, particulate multimetal oxide catalyst comprising molybdenum and at least one further metal as active composition in the fixed-bed reactor (R) and in a regeneration step (ii), the heterogeneous, particulate multimetal oxide catalyst comprising molybdenum and at least one further metal as active composition is regenerated by passing an oxygen-comprising regeneration gas mixture over it and burning off the carbonaceous material deposited on the multimetal oxide catalyst, where a regeneration step (ii) is carried out between two production steps (i) and where a product gas stream (6) which comprises 1,3-butadiene and additionally unreacted n-butenes, oxygen, water and further secondary components, in particular carbon monoxide, carbon dioxide, inert gases, in particular nitrogen, high-boiling hydrocarbons, i.e. hydrocarbons having a boiling point of 95° C. or above at a pressure of one atmosphere, optionally hydrogen and optionally oxygenates is obtained in the production step (i) in the fixed-bed reactor (R) and is fed as such or after one or more intermediate steps as stream (11) to an absorption column (K) in which an absorption is carried out at a pressure in the range from 3.5 to 20 bar by means of a high-boiling absorption medium (13) which becomes loaded with the C4-hydrocarbons from the product gas stream (6) or the stream (11) and is taken off as loaded solvent stream (14) from the bottom of the absorption column (K) to give an overhead stream (12) comprising oxygen, low-boiling hydrocarbons, i.e. hydrocarbons having a boiling point of less than 95° C. at a pressure of one atmosphere, residues of C4-hydrocarbons, residues of high-boiling hydrocarbons, i.e. hydrocarbons having a boiling point of 95° C. or above at a pressure of one atmosphere, optionally inert gases, in particular nitrogen, optionally carbon oxides and optionally water vapor, and is partly or completely recycled as recycle stream to the fixed-bed reactor (R), wherein at the end of each production step (i), the introduction of the oxygen-comprising gas (2) into the reactor (R) is throttled back or shut off and the production step (i) is continued until the oxygen concentration in the overhead stream (12) has decreased to 5% by volume, based on the total volume of the overhead stream (12), whereupon the introduction of the gas stream (1) comprising the n-butenes and also the introduction of the oxygen-comprising gas (2) is shut off, if this has not already been done at the end of the production step (i), at which point the production step (i) is complete and the regeneration step (ii) is started by the overhead stream (12) from the absorption column (K) functioning as oxygen-comprising regeneration gas mixture or substream of the oxygen-comprising regeneration gas mixture, is proposed.
Abstract:
The invention relates to a process for preparing butadiene from n-butenes, comprising the steps of: A) providing an input gas stream a comprising n-butenes, B) feeding the input gas stream a comprising n-butenes and a gas containing at least oxygen into at least one oxidative dehydrogenation zone and oxidatively dehydrogenating n-butenes to butadiene, giving a product gas stream b comprising butadiene, unconverted n-butenes, water vapor, oxygen, low-boiling hydrocarbons and high-boiling secondary components, with or without carbon oxides and with or without inert gases; Ca) cooling the product gas stream b by contacting with a cooling medium in at least one cooling zone, the cooling medium being at least partly recycled and having an aqueous phase and an organic phase, Cb) compressing the cooled product gas stream b which may have been depleted of high-boiling secondary components in at least one compression stage, giving at least one aqueous condensate stream c1 and one gas stream c2 comprising butadiene, n-butenes, water vapor, oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases; D) removing uncondensable and low-boiling gas constituents comprising oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases, as gas stream d2 from the gas stream c2 by absorbing the C4 hydrocarbons comprising butadiene and n-butenes in an absorbent, giving an absorbent stream laden with C4 hydrocarbons and the gas stream d2, and then desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream d1, E) separating the C4 product stream d1 by extractive distillation with a butadiene-selective solvent into a stream e1 comprising butadiene and the selective solvent and a stream e2 comprising n-butenes; F) distilling the stream e1 comprising butadiene and the selective solvent into a stream f1 consisting essentially of the selective solvent and a stream f2 comprising butadiene, wherein stage Cb) comprises at least two compression stages Cba) and at least two cooling stages Cbb) configured in the form of quench columns, the cooling in the cooling stages being effected by direct contacting with a biphasic cooling medium having an aqueous phase and an organic phase.
Abstract:
The invention relates to a process for preparing butadiene from n-butenes having a start-up phase and an operating phase, wherein the process in the operating phase 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, of an oxygen-comprising gas stream a2 and of 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, unreacted n-butenes, water vapor, oxygen, low-boiling hydrocarbons, high-boiling secondary components, possibly carbon oxides and possibly inert gases; C) cooling and compression of the 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, n-butenes, water vapor, oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases; D) introduction of the gas stream c2 into an absorption zone and separation of incondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases as gas stream d from the gas stream c2 by absorption of the C4-hydrocarbons comprising butadiene and n-butenes in an absorption medium, giving an absorption medium stream loaded with C4-hydrocarbons and the gas stream d, and recirculation, optionally after separating off a purge gas stream p, of the gas stream d as recycle gas stream d2 to the oxidative dehydrogenation zone; and the start-up phase comprises the steps: i) introduction of the oxygen-comprising gas stream and an inert gas stream into the dehydrogenation zone in such a ratio that the oxygen content of the recycle gas stream d2 corresponds to from 30 to 80% of the oxygen content of the recycle gas stream d2 in the operating phase; ii) setting of the recycle gas stream d2 to at least 70% of the volume flow of the recycle gas in the operating phase; iii) optional introduction, at an initial oxygen content of the recycle gas stream d2 of from 30 to 80% of the oxygen content of the recycle gas stream d2 in the operating phase, of a steam stream a3 into the dehydrogenation zone; iv) introduction, at an initial oxygen content of the recycle gas stream d2 of from 30 to 80% of the oxygen content of the recycle gas stream d2 in the operating phase, of an oxygen-comprising gas stream a2′ and a butene-comprising feed gas stream a1′ having a smaller volume flow than in the operating phase in a ratio k=a2′/a1′ and raising of the volume flow of the gas streams a1′ and a2′ until the volume flows of the gas streams a1 and a2 in the operating phase are obtained, with the recycle gas stream d2 being at least 70% and not more than 120% of the volume flow in the operating phase.
Abstract:
The invention relates to a process for preparing butadiene from n-butenes, comprising the steps of: A) providing an input gas stream a comprising n-butenes; B) feeding the input gas stream a comprising n-butenes and an oxygenous gas into at least one oxidative dehydrogenation zone and oxidatively dehydrogenating n-butenes to butadiene, giving a product gas stream b comprising butadiene, unconverted n-butenes, water vapor, oxygen, low-boiling hydrocarbons and high-boiling secondary components, with or without carbon oxides and with or without inert gases; Ca) cooling the product gas stream b by contacting it with a coolant and condensing at least a portion of the high-boiling secondary components; Cb) compressing the remaining product gas stream b in at least one compression stage, giving at least one aqueous condensate stream c1 and one gas stream c2 comprising butadiene, n-butenes, water vapor, oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases; Da) removing uncondensable and low-boiling gas constituents comprising oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases, as gas stream d2 from the gas stream c2 by absorbing the C4 hydrocarbons comprising butadiene and n-butenes in an absorbent, giving an absorbent stream laden with C4 hydrocarbons and the gas stream d2, and Db) subsequently desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream d1, which comprises additionally feeding in a methane-comprising gas stream at at least one point in the process section comprising steps B), Ca), Cb) and Da) in such amounts that the formation of an explosive gas mixture in step Da) is avoided.