Bwiti, imines are formed by the reaction of an amine with a carbonyl compound with the simultaneous removal of water, for example
* by azeotropic distillation (what Ritter said, ref.: J. Chem. Soc. (1958), p 2209),
* by the addition of a drying agent such as
- anhydrous sodium sulphate (ref.: J. Org. Chem. (1978) vol 43, p 2907)
- anhydrous potassium carbonate (ref.: J. Org. Chem. (1974) vol 39, p 3104)
* by the addition of molecular sieves (ref.: Recl. Trav. Chim. Pays-Bas (1972) vol 91 p 605)
* by the use of titanium(IV)chloride (ref.: J. Org. Chem. (1967) vol 32, p 3246
If the amine and the carbonyl compound are both aliphatic, the imines tend to decompose or polimerise; in these cases their further reaction is carried out without delay. When one or both of the reagents is aromatic, the imines are quite stable.
Check out:
https://www.thevespiary.org/rhodium/Rhodium/chemistry/pcp/imine_synth.html#Examplepce
Here they use KOH as drying agent.
I suggest using a drying agent to condense cyclohexanone and n-butylamine, it seems to be more convenient / less suspicious.
Here 's the J. Org. Chem. (1978) vol 43, p 2907 procedure:
2-methylpropanal (72 g, 1 mol) is added dropwise and with stirring during 2 hours to t-butylamine (73 g, 1 mol). During the addition the temperature rises from 25 to 40 °C and an aqueous layer separates near the end of the addition. The organic layer separates near the end of the addition. The organic layer is treated with anhydrous potassium carbonate (15g), stirred at 25 °C for 17 hours, and then decanted on to barium oxide (12 g). After the mixture has been stirred for 10 hours, it is filtered and the organic filtrate is distilled to separate the imine as a colourless liquid, b.p. 56 °C / 75 mm Hg, 88.3 g (70 %).
Use a good oil pump to distill under vacuum, so that the imine doesn't decompose.