| 摘要 |
<p>#CMT# #/CMT# Preparing acrolein and/or acrylic acid from propane comprises supplying two gaseous, propane-containing current to a first reaction zone A, under the formation of a reaction gas A; introducing the reaction gas A to a reaction zone A, supplying molecular oxygen and removing the product gas containing propylene, propane and water vapor; separating water vapor from the product gas A; feeding oxidation reactor with a reaction gas B containing propane, propylene and molecular oxygen and subjecting propylene to heterogeneously catalyzed, partial gas-phase oxidation. #CMT# : #/CMT# Preparation of acrolein and/or acrylic acid from propane comprises: (a) supplying at least two gaseous, propane-containing current (where one contains at least a fresh propane) to a first reaction zone A, under the formation of a reaction gas A; introducing the reaction gas A in the reaction zone A, formed through at least a catalyst bed by means of partial heterogeneous catalytic dehydrogenation of propane, molecular hydrogen and propylene, supplying molecular oxygen to the reaction zone A, where the molecular oxygen oxidizes a partial quantity of molecular hydrogen contained in the reaction gas A to form water vapor in the reaction zone A, and removing the product gas containing propylene, propane and water vapor, from the reaction zone A; (b) partially or completely separating, optionally in a first separation zone I, the water vapor contained in the product gas A by means of condensation incorporating indirect and/or direct cooling of the product gas A, while leaving behind a product gas Aa; (c) using the product gas A or Aa along with the supply of molecular oxygen, in a reaction zone B, for feeding at least an oxidation reactor with a reaction gas B containing propane, propylene and molecular oxygen, and subjecting the propylene contained in the reactor to heterogeneously catalyzed, partial gas-phase oxidation to form acrolein and/or acrylic acid as end product, and product gas B containing non-converted propane; (d) discharging the product gas B from the reaction zone B and separating the end product in a second separation zone II, while leaving behind a residual gas containing propane; (e) optionally reintroducing the partial quantity of the residual gas exhibiting the same composition of the residual gas as a propane-containing feed stream into the reaction zone A; (f) partially or completely separating the water vapor and/or the molecular hydrogen, in a separation zone III, which are possibly contained previously in the residual gas that is not fedback into the reaction zone A, by means of condensation and membrane separation processes respectively, and taking up the contained propane from the residual gas by absorption in an organic solvent under the formation of an absorbed substance that contains propane; and (g) separating the propane, in a separation zone IV, from the absorbed substance and reintroducing as propane-containing feed stream into the reaction zone A, where in the reaction zone A, at least lot of molecular hydrogen is oxidized to form water vapor, so that the hydrogen quantity that is oxidized in the reaction zone A to form water vapor amounts to at least 20 mol.% of the quantity of molecular hydrogen that is formed in the reaction zone A. #CMT#USE : #/CMT# Acrylic acid is a basic chemical useful as a monomer in the preparation of polymers, e.g. as a binding agent in an aqueous dispersion medium. Acrolein is used as an important intermediate product in the production of glutardialdehyde, methionine, 1,3-propanediol, 3-picoline, folic acid and acrylic acid. #CMT#ADVANTAGE : #/CMT# The process is feasible. #CMT#INSTRUMENTATION AND TESTING : #/CMT# Preferred Components: The reaction zone A comprises at least a partitioned, multi-stage fixed bed catalytic reactor. The reaction zone A is adiabatically designed. #CMT#ORGANIC CHEMISTRY : #/CMT# Preferred Process: At least a part of the heat energy produced by the oxidation of molecular hydrogen in the reaction zone A is used for heating up of the feed streams supplied to the reaction zone A by indirect heat exchange with reaction gas A and/or product gas A as heat transfer medium. The quantity of hydrogen oxidized in the reaction zone A to water vapor is at least 30 (preferably 40) mol.% or 20-90 (preferably 30-70) mol.% of the quantity of molecular hydrogen formed in the reaction zone A. The reaction gas B optionally contains molecular hydrogen. The product gas A removed from the reaction zone A is used as feed stream in the oxidation reactor in the reaction zone B. In the separation zone I, at least 5 (preferably 50) mol.% or 5-98 mol.% of water vapor contained in the product gas A is separated by means of condensation. The working pressure in the reaction zone A is greater than 1-5 bar. The working pressures in the various zone of the procedure is determined at the entrance of the respective zone, where the working pressure of reaction zone A is greater than separation zone I, which is greater than reaction zone B, which is greater than separation zone II, which is greater than separation zone III, which is greater than separation zone IV, which is greater than reaction zone A. In the reaction zone A, molecular hydrogen is oxidized with molecular oxygen not before 90 (preferably 65) mol.% of the totally formed molecular hydrogen is formed in the reaction zone A. In a separation zone I, the water vapor contained in the product gas is at least partially separated, and this separation is caused by indirect and direct cooling of the product gas. A partial quantity of the residual gas that exhibits the composition of the residual gas is fedback as a propane-containing feed stream into the reaction zone A, and the residual gas contains molecular oxygen. The molecular oxygen supplied to the reaction zone A is supplied as a component of air or gas, which does not contain more than 50 vol.% of components that are different from molecular oxygen. The separation of propane from the absorbed substance is carried out in the separation zone IV by means of stripping with a water vapor-containing gas, and the strip gas laden with propane is fedback as propane-containing feed stream into the reaction zone A. In a single passage through the reaction zone A, 10-40 mol.% of the total propane that is supplied to the reaction zone A is dehydrogenated in the reaction zone A. The reaction gas A formed in the reaction zone A contains 50-80 (preferably 55-80) vol.% or 30-50 vol.% of propane, 0.1-20 vol.% or 15-30 vol.% of propylene, 0-10 (preferably 2-10) vol.% of hydrogen, 1-5 vol.% or 0-1 vol.% of oxygen, 0-20 vol.% or 0-35 vol.% of nitrogen and 5-15 vol.% or 10-25 vol.% of hydrogen peroxide. The product gas A is cooled by indirect heat exchange with the propane-containing feed stream, which is separated in the separation zone IV and fedback into the reaction zone A. The heterogeneously catalyzed gas-phase partial oxidation is a double-stage partial oxidation of propylene to acrylic acid. The reaction gas supplied to the second oxidation stage contains 3-25 vol.% of acrolein, 5-65 vol.% of molecular oxygen, 6-70 vol.% of propane, 0-20 vol.% of hydrogen, 8-65 vol.% of hydrogen peroxide and 0-70 vol.% of nitrogen. The residual gas contains 1-20 vol.% of hydrogen peroxide, 0-80 vol.% of nitrogen, 10-90 vol.% of propane, 0-20 vol.% of hydrogen, 0-10 vol.% of oxygen, 1-20 vol.% of carbon dioxide and >= 0-5 vol.% of carbon monoxide. The propane-containing feed stream, which is separated from the separation zone IV and fedback into the reaction zone A, contains 80-99 mol.% of propane, 0-5 mol.% of propylene and 0-20 mol.% of hydrogen peroxide. A partial quantity of the residual gas that exhibits the composition of the residual gas is fedback as a propane- containing feed stream into the reaction zone A, and the partial quantity of the residual gas is 10 wt.%, based on the total amount of residual gas. The molecular oxygen supplied to the reaction zone B is supplied as a part of a gas, which does not contain more than 50 vol.% of components that are different from molecular oxygen. The molecular oxygen supplied to the reaction zone B is also supplied as a component of air. #CMT#EXAMPLE : #/CMT# The reaction gas (A) (7.30 Nm 3>/h) containing propane (61.22 vol.%), propylene (12.17 vol.%), ethylene (0.86 vol.%), methane (2.56 vol.%), hydrogen (3.78 vol.%), oxygen (2.10 vol.%), water (12.08 vol.%), carbon monoxide (0.38 vol.%) and carbon dioxide (3.35 vol.%) was contacted to a catalyst bed and heated at 400[deg]C and 2.13 bar. Further molecular oxygen was added at 139[deg]C and 2.33 bar, and the product gas containing propane (42.19 vol.%), propylene (22.79 vol.%), ethylene (1.14 vol.%), methane (3.42 vol.%), hydrogen (5.28 vol.%), water (20.32 vol.%) and carbon dioxide (3.36 vol.%) was removed at 551[deg]C and 2.05 bar. Further a reaction gas (B) containing propane (37.01 vol.%), propylene (19.99 vol.%), ethylene (0.99 vol.%), methane (2.99 vol.%), hydrogen (4.63 vol.%), oxygen (26.79 vol.%), water (3.14 vol.%) and carbon dioxide (2.95 vol.%) was added. The reaction gas B was led into a first oxidation step at 335[deg]C, and second oxidation step at 270[deg]C and 1.55 bar. The obtained mixture was cooled to 113[deg]C, using propane as coolant and the propane was separated using the propane wash column.</p> |
