Effect of initial solution apparent pH on the performance of submerged hybrid system for the p-nitrophenol hydrogenation

Coupling nanocatalysis with ceramic membrane separation can solve the problem of nanocatalyst separation in situ from a reaction mixture. A submerged hybrid system combining nanocatalysis and ceramic membrane separation was designed for the liquid phase hydrogenation of p-nitrophenol to p-aminophenol, and the effect of initial solution apparent pH (pH_a) on the performance of submerged hybrid system was investigated in detail. It is demonstrated that as the initial solution pH_a is adjusted from 4.5 to 7.5, the catalytic stability of nano-sized nickel is remarkably improved, possibly because the formation of impurity on the nickel surface can be restrained at weak alkaline condition, while the catalytic activity and selectively almost do not change. The membrane permeability is not affected significantly by the initial solution pH_a.