Acid ion exchange resin Amberlyst
46 (A46) was used for the
experiments. It demonstrated high mechanical and chemical stability over several esterification cycles. A46 is a copolymer of styrene cross-linked with divinylbenzene (DVB) with sulphuric type
acid groups in the form of spherical beads (Fig. 1). The amount of
crosslinking determines its main physical characteristics (surface
area and pore size distribution) (Table 3) [32]. The higher the
DVB amount added during the copolymerization, the higher the
reticulation degree and, as a consequence, the smaller the pores.
The amount of DVB plays a major role in controlling the physical
features of these catalysts (Table 3). The strongASO3H acid groups
formed on the resin during the sulphonation step are the active
sites responsible for the esterification of the FFA.