Use of completely mixed flow-through systems : Hydrolysis of phenyl picolinate
Experimental equipment was developed to study the hydrolysis of environmentally relevant compounds in completely mixed flow-through reactors. The hydrolysis of a carboxylic acid ester, phenyl picolinate (PhP), was investigated in homogeneous solutions and in the presence of titanium dioxide particles. In the absence of solids, the hydrolysis of PhP is dominated by the acid-catalyzed reaction below pH 4 and by the base-catalyzed reaction above pH 5, while the neutral hydrolysis is of minor importance across the whole pH range investigated (2 < pH < 8 ). However, in presence of 10 g of TiO2 L-1 (≃420 m2 surface area L-1 ), the neutral, surface-catalyzed reaction dominated the overall hydrolysis process in the entire range from pH 2 to pH 9. Steady-state rates of the heterogeneous hydrolysis were about 1 order of magnitude slower in completely mixed flow-through systems than initial hydrolysis rates in batch systems. This was attributed to reaction products occupying reactive sites at the mineral surface, th...