Knoevenagel condensation converts an aldehyde or ketone & an activated methylene (e.g. a malonic diester) to a substituted alkene using an amine base as a catalyst. The reaction starts with deprotonation of the methylene by the base to give a resonance stabilized enolate. The amine also reacts with the aldehyde or ketone to form an iminium ion intermediate, which then gets attacked by the enolate. The intermediate compound formed gets deprotonated by the base to give another enolate while the amine of the intermediate gets protonated. A rearrangement then follows which frees the amine base, regenerates the catalyst, and gives the final alkene product.

I taught Organic Chemistry (3) few times in the past & I am not aware of acidic catalysis for this reaction. If there is new discovery, then I expect the use of weak organic acid such as CH3COOH.

ketones also can be subjected to knoevenagel condensation. Catalytic system of piperidine along with acetic acid is well known for this reaction. this reaction proceeds via Ionoc liquid formation in-situ. You can refer the following papers.

10.1021/acs.jpcb.7b03191

for lewis acid catalysed knoevenagel condensation

• 10.1081/SCC-120025194