A New Deactivation Mechanism of Sulfate-Promoted Iron Oxide

Abstract

The deactivation of sulfate-promoted iron oxide in the esterification of acetic acid and n-butanol was studied.

Sulfated Iron Oxide: A Proficient Catalyst for Esterification of Butanoic Acid with Glycerol

“…The endothermic peak at the temperature of 180 °C indicates the removal of physically adsorbed water from catalyst material, and the second endothermic peak at the higher temperature represents dehydroxylation which is also revealed by TGA. 14 DSC and TGA curves became stable after the temperature of 330 °C which shows the stability of the catalyst at high temperatures.…”

“…Catalyst calcined for 5 h (Figure 3c) has shown the bands at 1212, 1126, and 1031 cm −1 , confirming the SO and S−O symmetric and asymmetric vibrations, which are assigned for the chelating sulfate ions that are coordinated to the iron cation (Fe 3+ ). 14 These asymmetrical bands are due to the presence of free sulfate ions on the surface of the catalyst which has further resulted in the leaching of these ions in the reaction mixture. On the contrary, catalyst calcined for 7 h (Figure 3b) has shown the only explainable characteristic band at a subsequent wavenumber of 1128 cm −1 which indicates the presence of significant sulfate ions with Td symmetry.…”

“…Overall, there was a lack of simplicity in the proposed protocol. Recently, Shi et al 14 has presented the deactivation mechanism of sulfated iron oxide catalyst in the esterification of acetic acid and n-butanol. Nevertheless, again, the long preparation procedure, use of more resources, use of high catalyst amount, and leaching of catalyst have made it unfeasible to utilize extensively.…”

“…Among these, the employment of catalysts derived from iron oxides has increased due to their availability, nontoxicity, low cost, and ability to catalyze reactions at low temperature . However, previous research has diplayed the obstacles of its preparation due to the lengthy procedure and resources required, use of sulfuric acid, high amount of sulfate loading, leaching of sulfate ions, and low yield of desired products. − The approach for the evaluation of different iron precursors for the preparation of sulfated iron catalyst was described by Brown et al; however, some drawbacks existed including long preparation time (3–4 days), lower conversions, and the use of sulfuric acid for sulfation. Subsequently, Magnacca et al employed a multistep approach in the preparation of sulfated iron oxide with varying sulfate loading from 2 to 8 wt %.…”

Synthesis, characterization and properties of Ce-modified S2O82−/ZnAl2O4 solid acid catalysts

“…9 For example, Shi had reported that the catalytic activities of sulfatepromoted iron oxide dropped from 84.48% to 51.48% aer 10 recycles in the n-butyl acetate esterication. 27 In fact, deactivation is a general problem and a rather complicated phenomenon in heterogeneous catalysis, which is also the main problem faced by SO / ZnAl 2 O 4 -4 wt% Ce solid acid catalyst showed the obviously better reusability, which remained above 80% esterication even aer being used for six times. This result might be attribute to its excellent structural stability and excellent resistance to the loss of the sulfur species.…”