Heterogeneous Tin Catalysts Applied to the Esterification and Transesterification Reactions

Table 8

Properties of 30% wt. SO₄²⁻/Fe₂O₃-SnO₂ catalysts obtained from iron(III) different precursors FeCl₃ (1), Fe(NO₃)₃ (2), and Fe₂(SO₄)₃ (3) calcined at 500°C and conversion of FFA esterification^a,b [33].

30% wt. SO4^2−/Fe2O3-SnO2 catalyst	BET surface area (m^2/g)	Pore volume (cm^3/g)	𝐸𝑖 (mV)	NAS (meq./g)	FFA Conversion (%)^b
Precursor (1)	84.9	0.17	+394	1.18	70.3
Precursor (2)	67.4	0.11	+380	0.96	64.0
Precursor (3)	86.0	0.18	+402	1.20	72.1

^a𝐸_𝑖: initial electrode potentional indicates the maximum acid strength of the sites; NAS: acid site numbers.
^bReaction conditions: 250 rpm, 25 mL of methanol 25 mL of crude palm oil (10.2 wt.% of FFA) was added, followed by methanol (45 mL), 1 g of catalyst, 3 hours, 80°C.