Having established methods for the esterification of FFAs over
solid supported acid catalyst, and transesterification of triglycerides
over polymer bound NHC catalyst5, an integrated system to convert oils and fats into biodiesel was developed. The ZrCl4/Ph-SBA-15
column, and the NHC catalyst5were connected in series with an
intermediate drying column containing ground 3 A molecular
sieves. The synthesis of biodiesel in continuousflow was tested
using a variety of feedstocks from vegetable oils and animal fats
(Table 3). While a systematic examination of the impact of FFA on
performance was not undertaken this study allowed materials with
as little as 0.4% FFA (Entry 1) through to 1e2% FFA (Entries 8,9) to be
examined. In all cases, complete conversion of the feedstock to the
monoalkyl ester was observed and products were obtained in excellent yields (Table 3, entries 1e9), thus the system was robust
across a range of application specific conditions.
The stability and recyclability of the catalysts was demonstrated
by the use of a single batch of ZrCl4/Ph-SBA-15 catalyst for all
feedstocks tested (Table 3, entries 1e9). The NHC catalyst column
was regenerated in-line every three runs by pumping a solution of
KO
t
Bu (2 equiv) over 30 min. In addition, the reaction with beef fat
was run on 30 g (35.5 mmol) scale using freshly prepared catalysts,
resulting in a 96% isolated yield of biodiesel