Process for preparing 3-methylthiopropionaldehyde
A process for preparing 3-methylthiopropionaldehyde, by a) providing a liquid stream with methyl mercaptan and/or the hemi thioacetal formed from 3-methylthiopropionaldehyde and methyl mercaptan; b) providing an acrolein with a vapor stream, where the major part of the vapor stream is acrolein, and the pressure of the vapor stream is lower than atmospheric pressure; c) introducing the liquid stream with methyl mercaptan and/or the hemi thioacetal formed from 3-methylthiopropionaldehyde and methyl mercaptan of a) and the acrolein with a vapor stream of b) into a reaction unit with a vapor-liquid mixing device, and d) reacting acrolein with methyl mercaptan and/or the hemi thioacetal formed from 3-methylthiopropionaldehyde and methyl mercaptan in the reaction unit of c) to give a 3-methylthiopropionaldehyde product mixture.
1 . A process for preparing 3-methylthiopropionaldehyde, the process comprising:
(a) providing a liquid stream comprising methyl mercaptan and/or a hemi thioacetal formed from 3-methylthiopropionaldehyde and methyl mercaptan;
(b) providing a vapor stream comprising acrolein in major part, a pressure of the stream being lower than atmospheric pressure;
(c) introducing the liquid stream from the providing (a) and the vapor stream from the providing (b) into a reaction unit with a vapor-liquid mixing device; and
(d) reacting the acrolein with the methyl mercaptan and/or the hemi thioacetal formed from 3-methylthiopropionaldehyde and the methyl mercaptan in the reaction unit of the introducing (c) to give a product mixture comprising 3-methylthiopropionaldehyde.
2 . The process of claim 1 , wherein the vapor stream of the providing (b) comprises the acrolein in at least 70 wt. %.
3 . The process of claim 1 , wherein the pressure of the vapor stream of the providing (b) is in a range of from 300 to 950 mbara.
4 . The process of claim 1 , wherein the introducing (c) comprises mixing the liquid stream of the providing (a) and the vapor stream of the providing (b) in the vapor-liquid mixing device of the introducing (c).
5 . The process of claim 1 , wherein the pressure of the vapor stream of the providing (b) is generated in the vapor-liquid mixing device of the introducing (c) and/or by a vacuum generating device downstream of the reaction unit of the introducing (c).
6 . The process of claim 1 , wherein a temperature in the reacting (d) is higher than a condensation temperature of acrolein in the vapor stream of the providing (b).
7 . The process of claim 1 , wherein a temperature of the liquid stream in the reacting (d) is in a range of from 50 to 90° C.
8 . The process of claim 1 , wherein a temperature of the vapor stream in the introducing (b) is in a range of from 20 to less than 50° C.
9 . The process of claim 1 , wherein the liquid stream of the introducing (a) further comprises:
a solvent having a boiling temperature which is at least 20° C. higher than a boiling temperature of acrolein.
10 . The process of claim 1 , further comprising:
(e1) scrubbing acrolein and/or methyl mercaptan, if contained in an off-gas from the reaction of the reacting (d), with a solvent having a boiling temperature which is at least 20° C. higher than a boiling temperature of acrolein, to give a second liquid stream comprising acrolein and/or methyl mercaptan; and
(e2) feeding the second liquid stream, obtained in the scrubbing (e1) to the introducing (c) and/or to the reacting (d).
11 . The process of claim 1 , wherein the liquid stream of the introducing (a) further comprises a solvent, and
wherein the solvent is 3-methylthiopropionaldehyde.
12 . The process of claim 1 , further comprising:
(f1) withdrawing the product mixture obtained in the reacting (d) as a product stream, comprising 3-methylthiopropionaldehyde, from the reaction unit;
(f2) feeding at least a part of the product stream from the withdrawing (f1) to a heat exchanger to provide a tempered product comprising stream; and
(f3) feeding a part of the tempered product stream from the feeding (f2) to the reaction unit or mixing a part of the tempered product stream from the feeding (f2) with methyl mercaptan and/or the hemi thioacetal formed from 3-methylthiopropionaldehyde and methyl mercaptan to provide the liquid stream.
13 . The process of claim 12 , wherein the product stream is tempered in the feeding (f2) to a temperature in a range from 20 to 40° C.
14 . The process of claim 1 , wherein, when the liquid stream of the providing (a) further comprises a solvent different from the 3-methylthiopropionaldehyde, the process further comprises:
separating the solvent from the product mixture obtained from the reacting (d).
15 . The process of claim 1 , wherein a molar ratio of the methyl mercaptan and/or the hemi thioacetal formed from methyl mercaptan and 3-methylthiopropionaldehyde to the acrolein in the introducing (c) and/or reacting (d) is less than 1.
16 . The process of claim 1 , wherein the pressure of the acrolein comprising vapor stream of the providing (b) ranges is in a range of from 300 to 800 mbara.
17 . The process of claim 1 , wherein the pressure of the acrolein comprising vapor stream of the providing (b) ranges is in a range of from 600 to 950 mbara.
18 . The process of claim 1 , wherein the pressure of the acrolein comprising vapor stream of the providing (b) ranges is in a range of from 300 to 600 mbara.
19 . The process of claim 1 , wherein the vapor stream of the providing (b) comprises the acrolein in at least 70 wt. %, and
wherein the pressure of the vapor stream of the providing (b) is in a range of from 300 to 950 mbara.
20 . The process of claim 1 , wherein the vapor stream of the providing (b) comprises the acrolein in at least 70 wt. %,
wherein the pressure of the vapor stream of the providing (b) is in a range of from 300 to 950 mbara, and
wherein a temperature of the liquid stream in the reacting (d) is in a range of from 50 to 90° C.