In this study, a
metal–organic framework, namely, Zn3(BTC)2 (BTC = 1,3,5-benzenetricaboxylic acid),
was solvothermally synthesized and employed as a catalyst for biodiesel
production from degummed vegetable oil via a one-step transesterification
and esterification reaction. The resulting Zn3(BTC)2 particles exhibit a well-defined triclinic structure with
an average size of about 1.2 μm, high specific surface area
of 1176 m2/g, and thermal stability up to 300 °C.
The response surface methodology–Box–Behnken design
(RSM–BBD) was employed to identify the optimal reaction conditions
and to model the biodiesel yield in relation to three important parameters,
namely, the methanol/oil molar ratio (4:1–8:1), temperature
(45–65 °C), and time (1.5–4.5 h). Under the optimized
reaction conditions (i.e., 6:1 methanol/oil molar ratio, 65 °C,
4.5 h), the maximum biodiesel yield reached 89.89% in a 1 wt % catalyst,
which agreed very well with the quadratic polynomial model’s
prediction (89.96%). The intrinsic catalytic activity of Zn3(BTC)2, expressed as the turnover frequency, was found
to be superior to that of other MOF catalysts applied in the transesterification
and esterification reactions. The reusability study showed that the
as-synthesized Zn3(BTC)2 catalyst exhibited
good stability upon three consecutive reuses without a noticeable
decrease in the methyl ester yield (∼4%) and any appreciable
metal leaching (<5%). Furthermore, a preliminary technoeconomic
analysis showed that the total direct operating cost for the kilogram-scale
production of Zn3(BTC)2 is estimated to be US$50,
which may sound economically attractive.