We have developed processes for the phase transfer catalyzed O-alkylation of 3-phenyl-1-propanol. Firstly a batch solid-liquid (S-L) implementation was tested with toluene solvent. By running the organic phase neat and with 6 mol equivalents of 50 w/w% NaOH (aq.) at ambient temperature, the conversion for a batch liquid-liquid (L-L) process was found to be as good as for the S-L process with a shorter reaction duration. A continuous countercurrent L-L process was also developed. The sustainability performance of the batch S-L, batch L-L and continuous L-L processes was compared at a design output of 100 te/a. The synergy of phase transfer catalysis and continuous processing demonstrated a number of green and sustainability benefits, i.e. higher energy efficiency, lower VOC emission, better volume efficiency, smaller processing inventory, smaller equipment footprint, lower product loss through waste and lower operating cost. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.