Method for preparing 3-methylthiopropionaldehyde

1. A method for continuously preparing 3-methylthiopropionaldehyde, the method comprising:

reacting methyl mercaptan with acrolein to obtain the 3-methylthiopropionaldehyde,

wherein deviations in a stoichiometry of the methyl mercaptan to the acrolein during the reacting to obtain the 3-methylthiopropionaldehyde are compensated for by supplying or forming 1,3-bis(methylthio)-1-propanol, and

wherein:

if the methyl mercaptan is present in excess with respect to the acrolein, an excess methyl mercaptan is converted to the 1,3-bis(methylthio)-1-propanol with the 3-methylthiopropionaldehyde, wherein the 1,3-bis(methylthio)-1-propanol formed is intermediately stored,

or

if the acrolein is present in excess with respect to the methyl mercaptan, the 1,3-bis(methylthio)-1-propanol is supplied to the reacting of the methyl mercaptan with the acrolein, wherein a molar amount of intermediately stored 1,3-bis(methylthio)-1-propanol to be supplied is at least as large as an amount of an excess acrolein.

2. The method according to claim 1 , wherein a molar ratio of the methyl mercaptan to the 3-methylthiopropionaldehyde during the reacting to obtain the 1,3-bis(methylthio)-1-propanol is from 0.1:1 (mol/mol) to 1:1 (mol/mol).

3. The method according to claim 1 , wherein an excess acrolein is present and the excess acrolein is reacted with the 1,3-bis(methylthio)-1-propanol to obtain the 3-methylthiopropionaldehyde.

4. The method according to claim 1 , wherein a portion of a stream comprising the methyl mercaptan is branched off before the reacting to obtain the 3-methylthiopropionaldehyde and is supplied to the forming of the 1,3-bis(methylthio)-1-propanol by reacting the 3-methylthiopropionaldehyde with the methyl mercaptan.

5. The method according to claim 1 , wherein a minimum stream of the methyl mercaptan is branched off before the reacting to obtain the 3-methylthiopropionaldehyde and

in parallel, a minimum stream of the 1,3-bis(methylthio)-1-propanol is supplied to the reacting of the methyl mercaptan with the acrolein.

6. The method according to claim 1 , wherein, if the acrolein is present in excess with respect to the methyl mercaptan, intermediately stored 1,3-bis(methylthio)-1-propanol is supplied to the reacting of the methyl mercaptan with the acrolein and is reacted with an excess acrolein to obtain the 3-methylthiopropionaldehyde.

7. The method according to claim 1 , wherein a molar amount of 1,3-bis(methylthio)-1-propanol supplied is at least as large as an amount of an excess acrolein.

8. The method according to claim 6 , wherein unreacted 1,3-bis(methylthio)-1-propanol is recovered.

9. The method according to claim 8 , wherein the 1,3-bis(methylthio)-1-propanol recovered is intermediately stored.

10. The method according to claim 8 , wherein, if the acrolein is present in excess with respect to the methyl mercaptan, a stream with an excess acrolein is branched off before the reacting to obtain the 3-methylthiopropionaldehyde and is reacted with the unreacted 1,3-bis(methylthio)-1-propanol separated from a product mixture to obtain the 3-methylthiopropionaldehyde.

11. The method according to claim 8 , wherein equal amounts of the unreacted 1,3-bis(methylthio)-1-propanol separated from a product mixture and the acrolein are reacted to obtain the 3-methylthiopropionaldhyde.

12. A method for storing methyl mercaptan and/or 3-methylthiopropionaldehyde, the method comprising:

storing the methyl mercaptan and/or 3-methylthiopropionaldehyde in form of 1,3-bis(methylthio)-1-propanol,

wherein the 1,3-bis(methylthio)-1-propanol originates from and/or is supplied to a process for continuously preparing the 3-methylthiopropionaldehyde,

wherein the process comprises:

reacting methyl mercaptan with acrolein to obtain the 3-methylthiopropionaldehyde,

wherein deviations in the stoichiometry of the methyl mercaptan to the acrolein in the reacting to obtain the 3-methylthiopropionaldehyde are compensated for by supplying or forming the 1,3-bis(methylthio)-1-propanol, and

wherein:

if the methyl mercaptan is present in excess with respect to the acrolein, an excess methyl mercaptan is converted to the 1,3-bis(methylthio)-1-propanol with the 3-methylthiopropionaldehyde, wherein the 1,3-bis(methylthio)-1-propanol formed is intermediately stored,

or

if the acrolein is present in excess with respect to the methyl mercaptan, the 1,3-bis(methylthio)-1-propanol is supplied during the reacting of the methyl mercaptan with the acrolein, wherein a molar amount of intermediately stored 1,3-bis(methylthio)-1-propanol to be supplied is at least as large as an amount of excess acrolein.