Continuous method for producing n-butyl(meth)acrylate including a catalyst recirculation process

Abstract

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 () 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 () 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 (), * discharging a high-boiling sump discharge () out of the sump of the rectification column (E), the mass flow ratio of the high-boiling sump discharge () 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 () of the discharged high-boiling sump discharge () to a mixer (H), the mass flow ratio of the high-boiling sub-flow () to the high-boiling sump discharge () ranging from 0.01 to 0.5, preferably 0.05 to 0.08, * supplying a mixture () 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 () and an aqueous catalyst-containing extract (), said aqueous extract () being at least partly recirculated to the reactor (A) and/or the rectification column (E), wherein —a sub-flow of the aqueous phase () from the phase separator (G), —a sub-flow of the aqueous phase () from the phase separator (D) and/or —a sub-flow of the aqueous phase () from the phase separator (D) is supplied to the phase separator (G), and subsequently a sub-flow of the aqueous phase () from the phase separator (G) is supplied to the mixer (H). The mass flow ratio of the sub-flow of the aqueous phase () to the high-boiling sub-flow () of the discharged high-boiling sump discharge () ranges from 0.08 to 0.50, and the mass flow ratio of the sub-flow of the aqueous phase () to the high-boiling sub-flow () of the discharged high-boiling sump discharge () ranges from 0.08 to 0.50.