Continuous method for producing n-butyl(meth)acrylate including a catalyst recirculation process
The invention relates to a method for continuously producing n-butyl(meth)acrylate by reacting (meth)acrylic acid with n-butanol in the presence of an acid catalyst and a polymerization inhibitor. In a first embodiment, the method has the steps of: * carrying out an esterification within a reactor (A) comprising a column (B) installed thereon, wherein the components (meth)acrylic acid and n-butanol are used in a molar ratio ranging from 1.0:1.0 to 10:2.0, preferably 1.0:1.1 to 1.0:1.5, and the esterification is carried out at a temperature ranging from 80 to 150° C., preferably 100 to 130° C., and an absolute pressure ranging from 0.2 to 5.0 bar, preferably 0.4 to 1.5 bar, whereby a resulting reaction product ( 6 ) and a vapor flow are obtained at the head of the column (B), * discharging the vapor flow at the head of the column (B), * condensing the vapor flow in a condenser (C), thereby forming an organic phase, which is enriched with n-butyl(meth)acrylate, and an aqueous phase, * continuously separating the organic phase from the aqueous phase by means of a phase separator (D), * supplying the resulting reaction product ( 6 ) to a rectification column (E), * separating the azeotrope within the rectification column (E) consisting of: a) water and n-butyl(meth)acrylate, b) n-butanol and n-butyl(meth)acrylate, c) n-butanol and water, and d) n-butanol, n-butyl(meth)acrylate, and water, wherein the rectification column (E) is operated at a sump temperature ranging from 80 to 150° C. and at a temperature at the head ranging from 70 to 130° C. and an absolute pressure ranging from 0.2 to 5 bar, preferably 0.4 to 1.5 bar, * discharging a gas flow enriched with the azeotrope at the head of the rectification column (E), * condensing the gas flow in a condenser (F), thereby forming an organic phase, which is enriched with n-butyl(meth)acrylate, and an aqueous phase, * continuously separating the organic phase from the aqueous phase by means of a phase separator (G), * continuously discharging at least one part of the organic phase out of the phase separator (G), said discharged part of the n-butyl(meth)acrylate-enriched organic phase constituting the raw product flow ( 15 ), * discharging a high-boiling sump discharge ( 23 ) out of the sump of the rectification column (E), the mass flow ratio of the high-boiling sump discharge ( 23 ) to the (meth)acrylic acid supplied to the reactor (A) as a reactant ranging from 0.5 to 5, * supplying a high-boiling sub-flow ( 7 ) of the discharged high-boiling sump discharge ( 23 ) to a mixer (H), the mass flow ratio of the high-boiling sub-flow ( 7 ) to the high-boiling sump discharge ( 23 ) ranging from 0.01 to 0.5, preferably 0.05 to 0.08, * supplying a mixture ( 10 ) resulting from the mixer (H) to an extraction phase separator (I) arranged downstream thereof, and * continuously separating the mixture in the extraction phase separator (I), thereby obtaining an organic raffinate ( 11 ) and an aqueous catalyst-containing extract ( 12 ), said aqueous extract ( 12 ) being at least partly recirculated to the reactor (A) and/or the rectification column (E), wherein —a sub-flow of the aqueous phase ( 18 ) from the phase separator (G), —a sub-flow of the aqueous phase ( 26 ) from the phase separator (D) and/or —a sub-flow of the aqueous phase ( 5 ) from the phase separator (D) is supplied to the phase separator (G), and subsequently a sub-flow of the aqueous phase ( 18 ) from the phase separator (G) is supplied to the mixer (H). The mass flow ratio of the sub-flow of the aqueous phase ( 18 ) to the high-boiling sub-flow ( 7 ) of the discharged high-boiling sump discharge ( 23 ) ranges from 0.08 to 0.50, and the mass flow ratio of the sub-flow of the aqueous phase ( 5 ) to the high-boiling sub-flow ( 7 ) of the discharged high-boiling sump discharge ( 23 ) ranges from 0.08 to 0.50.
1 . A process for continuously preparing n-butyl (meth)acrylate by reacting (meth)acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor, comprising the steps of:
performing an esterification within a reactor A with a column B on top, where the (meth)acrylic acid and n-butanol components are in a molar ratio in the range from 1.0:1.0 to 1.0:2.0, and where the esterification takes place at a temperature in the range from 80 to 150° C., and at an absolute pressure in the range from 0.2 to 5.0 bar, as a result of which a resulting bottom reaction output is obtained, while a vapor stream is obtained at the top of the column B,
discharging the vapor stream at the top of the column B,
condensing the vapor stream in a condenser C to form an organic phase and an aqueous phase,
separating the organic phase from the aqueous phase by means of a phase separator D,
feeding the resulting reaction output into a rectification column E,
separating off the following azeotropes within the rectification column E:
a) water and n-butyl (meth)acrylate,
b) n-butanol and n-butyl (meth)acrylate,
c) n-butanol and water,
d) n-butanol, n-butyl (meth)acrylate and water,
where the rectification column E is operated at a bottom temperature in the range from 80 to 150° C. and at a temperature at the top in the range from 70 to 130° C. and at an absolute pressure in the range from 0.2 to 5 bar,
discharging a gas stream enriched by the azeotropes at the top of the rectification column E,
condensing the gas stream in a condenser F to form an n-butyl (meth)acrylate-enriched organic phase and an aqueous phase,
separating the organic phase from the aqueous phase by means of a phase separator G,
removing at least a portion of the organic phase from the phase separator G, where this removed portion of the n-butyl (meth)acrylate-enriched organic phase constitutes the crude product stream,
discharging a high boiler bottoms output from the bottom of the rectification column E, where the mass flow ratio between the high boiler bottoms output and the (meth)acrylic acid fed to the reactor A as reactant is in the range from 0.5 to 5,
feeding a high boiler substream of the discharged high boiler bottoms output into a mixer H, where the mass flow ratio between the high boiler substream and the high boiler bottoms output is in the range from 0.01 to 0.50,
feeding a mixture that results from the mixer H into a downstream extraction phase separator I,
separating off the mixture in the extraction phase separator I to obtain an organic raffinate and a catalyst-comprising aqueous extract, where the aqueous extract is recycled at least partly to the reactor A or to the rectification column E, wherein a substream of the organic raffinate is fed to a cleavage reactor J, where the mass flow ratio between the substream of the organic raffinate and the total mass flow rate of the organic raffinate is in the range from 0.1 to 1.0, and wherein
a substream of the aqueous phase from the phase separator G,
a substream of the aqueous phase from the phase separator D or
a substream of the aqueous phase from the phase separator D is fed to the phase separator G and then a substream of the aqueous phase from this phase separator G
is fed to the mixer H, where the mass flow ratio between the substream of the aqueous phase and the high boiler substream of the discharged high boiler bottoms output is in the range from 0.08 to 0.5, and where the mass flow ratio between the substream of the aqueous phase and the high boiler substream of the discharged high boiler bottoms output is in the range from 0.08 to 0.5.
2 . A process for continuously preparing n-butyl (meth)acrylate by reacting (meth)acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor, comprising the steps of:
performing an esterification in a reaction zone, where the reaction zone is in the bottom of a rectification column E, where the (meth)acrylic acid and n-butanol components are in a molar ratio in the range from 1.0:1.0 to 1.0:2.0, and where the esterification takes place at a temperature in the range from 80 to 150° C., and at an absolute pressure in the range from 0.2 to 5.0 bar,
separating off the following azeotropes that form as a result of the esterification:
a) water and n-butyl (meth)acrylate,
b) n-butanol and n-butyl (meth)acrylate,
c) n-butanol and water,
d) n-butanol, n-butyl (meth)acrylate and water,
where the removal also takes place by means of the rectification column E, which is operated at a bottom temperature in the range from 80 to 150° C. and at a temperature at the top in the range from 70 to 130° C. and at an absolute pressure in the range from 0.2 to 5 bar,
discharging a gas stream enriched by the azeotropes at the top of the rectification column E,
condensing the gas stream in a condenser F to form an n-butyl (meth)acrylate-enriched organic phase and an aqueous phase,
separating the organic phase from the aqueous phase by means of a phase separator G,
removing at least a portion of the organic phase and the phase separator G, where this removed portion of the n-butyl (meth)acrylate-enriched organic phase constitutes the crude product stream,
discharging a high boiler bottoms output from the bottom of the rectification column E, where the mass flow ratio between the high boiler bottoms output and the (meth)acrylic acid fed to the reaction zone as reactant is in the range from 0.05 to 0.5, feeding a high boiler substream of the discharged high boiler bottoms output into a mixer H, where the mass flow ratio between the high boiler substream and the high boiler bottoms output is in the range from 0.01 to 1.0,
feeding a mixture that results from the mixer H into a downstream extraction phase separator I,
separating off the mixture in the extraction phase separator I to obtain an organic raffinate and a catalyst-comprising aqueous extract, where the aqueous extract is recycled at least partly to the rectification column E, wherein a substream of the organic raffinate is fed to a cleavage reactor J, where the mass flow ratio between the substream of the organic raffinate and the total mass flow rate of the organic raffinate is in the range from 0.1 to 1.0, and wherein
a substream of the aqueous phase from the phase separator G is fed to the mixer H, where the mass flow ratio between the substream of the aqueous phase from the phase separator G and the high boiler substream of the discharged high boiler bottoms output is in the range from 0.08 to 0.5.
3 . The process according to claim 1 , wherein the resulting mixture from the mixer H is at a temperature in the range from 20 to 100° C. at the outlet of the mixer H.
4 . The process according to claim 1 , wherein a substream of the aqueous extract is returned to the reactor A, where the mass flow ratio between the substream of the aqueous extract and the total mass flow rate of the aqueous extract is in the range from 0.1 to 1.0.
5 . The process according to claim 1 , wherein there is added to the high boiler substream of the discharged high boiler bottoms output in the mixer H such a mass flow rate
of the substream of the aqueous phase from the phase separator G
or of the substream of the aqueous phase from the phase separator D
that a phase ratio between the aqueous extract to be obtained and the organic raffinate to be obtained in the range from 0.08 to 0.5 kg/kg is achieved.
6 . The process according to claim 1 , wherein a substream of the high boiler bottoms output is fed to the cleavage reactor J in a mass flow ratio to the high boiler substream of the high boiler bottoms output in the range from 0.0 to 10.0.
7 . The process according to claim 1 , wherein the high boiler bottoms output has a water content in the range from 0.1% to 10.0% by weight.
8 . The process according to claim 1 , wherein the high boiler bottoms output has a catalyst content in the range from 0.1% to 10.0% by weight.
9 . The process according to claim 1 , wherein the acidic catalyst comprises in the range from 0% to 100% by weight of p-toluenesulfonic acid.
10 . The process according to claim 1 , wherein the high boiler bottoms output is monophasic.
11 . The process according to claim 1 , wherein a substream of the organic phase from the phase separator G is returned to the rectification column E with a reflux ratio based on the organic phase in the range from 0.1 to 1.0, and a substream of the aqueous phase from the phase separator G with a reflux ratio based on the aqueous phase in the range from 1 to 10.
12 . The process according to claim 1 , wherein the acidic catalyst is present in a concentration in the range from 0.1% to 10.0% by weight in the resulting reaction output of the reactor A.
13 . The process according to claim 1 , wherein an external water is additionally added to the mixer H.