| 摘要 |
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) andin 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) whichcomprises 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-butenesand 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. |
