2.3. Preparation of DDP
The cost of production in the industrialization of CaCO3 was an
important parameter. The cost of dodecyl dihydrogen phosphate
(DDP) made by researchers was low. P2O5 was added into H3PO4
solution (the H3PO4 concentration is about 85%) under constant stirring
at 50 °C. The solution was stirred for 1 h, then octadecyl alcohol
(C18H37OH) was introduced into the system. Meanwhile N2 was
bubbled into the suspension in order that C18H37OH was not oxidized
and the vapor was removed. After improving the temperature to 80 °C,
the esterification reaction was maintained for 4 h, following an extra
P2O5 that was put into the system in batches as complement to increase
the yield of octadecyl dihydrogen phosphate (C18H37OPO3H2). The
resulting suspension was used as organic substrate.