Process for the energy-efficient production of alkali metal alkoxides

A process for producing at least one alkali metal alkoxide of formula MAOR, wherein R is a C1 to C6 hydrocarbon radical, and wherein MA is sodium or potassium, the process comprising:

• (a1) reacting a reactant stream SAE1 comprising ROH with a reactant stream SAE2 comprising MAOH, in countercurrent at a pressure p3A and a temperature T3A in a first reactive rectification column RRA, to afford a crude product RPA comprising MAOR, water, the ROH, and the MAOH, wherein R is a C1 to C5 hydrocarbon radical, and MA is sodium or potassium, and
• withdrawing a bottoms product stream SAP comprising the ROH and the MAOR at a lower end of the first reactive rectification column RRA, and withdrawing a vapour stream SAB comprising the water and the ROH at an upper end of the first reactive rectification column RRA, and
• (a2) optionally, simultaneously with and spatially separate from (a1), reacting a reactant stream SBE1 comprising ROH with a reactant stream SBE2 comprising MBOH, in countercurrent at a pressure pam and a temperature T3B in a second reactive rectification column RRB, to afford a crude product RPB comprising MBOR, water, the ROH, and the MBOH, wherein MB is sodium or potassium, and
• withdrawing a bottoms product stream SBP comprising the ROH and the MBOR at a lower end of the second reactive rectification column RRB, and withdrawing a vapour stream SBB comprising the water and the ROH at an upper end of the second reactive rectification column RRB,
• (b) passing the vapour stream SAB into a first rectification column RD1, and, if (a2) is performed, the vapour stream SBB is also passed into the first rectification column RD1 in admixture with the vapour stream SAB or separately from the vapour stream SAB, to obtain a mixture GRD1 comprising water and ROH in the first rectification column RD1,
• (c) separating the mixture GRD1 or the vapour stream SAB in the first rectification column RD1 at a pressure p1 and a temperature T1, into an ROH-comprising vapour stream SRDB1 at an upper end of the first rectification column RD1, and a bottoms stream SRDS1 comprising water and ROH at a lower end of the first rectification column RD1,
• (d) passing the bottoms stream SRDS1 completely or partially into a second rectification column RD2, to obtain a mixture GRD2 comprising water and ROH in the second rectification column RD2,
• (e) separating the mixture GRD2 at a pressure p2 and a temperature T2, into an ROH-comprising vapour stream SRDB2 at a top of the second rectification column RD2, and a bottoms stream SRDS2 comprising water at a lower end of the second rectification column RD2, and
• (f) transferring energy from the vapour stream SRDB2 to the mixture GRD1 or to the vapour stream SAB in the first rectification column RD1,
• wherein p2>p1, p2>p3A, and wherein if (a2) is performed, p2>p3B.