Hydrogenolysis of N-Benzylcyclohexylamine: A Support Specific ‘Nano Effect’

Abstract

The hydrogenolysis of N-benzylcyclohexylamine (NBCA) was carried out at low temperature and pressure using series of Pd/SiO₂ catalysts having Pd contents between 0.5 and 10%. Three different silica supports were used, two of them having pore diameters of 60A and 40A and one an amorphous material. In the hydrogenolysis of NBCA over the Pd/SiO₂ (60A) series of catalysts there was a slight increase in the reaction rate on gong from the 10% Pd to the 2% Pd catalysts. This was followed by significant rate increases using the 1% Pd, 0.75% Pd and 0.5% Pd catalysts. It is proposed that this unexpectedly large rate increase observed using the catalysts having the smallest Pd particles was the result of a true ‘nano effect’. The rates of debenzylations run over the Pd/SiO₂ (40A) series of catalysts steadily increased with the use of the 10% Pd to the 2% Pd catalysts, a trend observed for some Structure Sensitive reactions, though, in this case, there was also a rate decrease using the 1% Pd catalyst even though the Pd particles in this catalyst were smaller than the others. No relationship was observed between reaction rate and Pd composition of the amorphous silica supported catalysts. It is commonly accepted that the nano effect is the result of an interaction between the small catalyst particles and the support so the electronic character of the support could have an influence on the surface electrons of the catalyst and, thus, modify its reaction capabilities.

Graphical Abstract