Stability of novel eco-friendly sulfated metal oxide solid acid catalyst for esterification and condensation reaction

Abstract

<h2>Abstract</h2> In this paper, the metal oxide supports and active component precursors of SO₄²⁻/M_xO_y solid acid were screened, and S₂O₈²‐⁻/Cr₂O₃-Fe₂O₃ (S₂-CrFe) was prepared. The NH₃-TPD results showed that the solid acids loaded with S₂O₈²⁻ had stronger acidity than those loaded with SO₄²⁻, and the mixture of the two metal oxides could adjust the acidity of the solid acids. The optimum conditions for the preparation of S₂-CrFe were as follows: the mass ratio of Cr₂O₃ to Fe₂O₃ was 1:1, the concentration of ammonium persulfate solution was 1 mol/L, and the calcination temperature was 550 °C. The yield of esterification catalyzed by the solid acid obtained under these conditions was 91.2%. The stability of the new solid acid was investigated, and it was found that S₂-CrFe was easy to be deactivated, so it was considered to be modified by organosilane and lanthanum oxide. The experimental results showed that after the modified solid acid was recycled for four times, the yield of ethyl acetate was more than 60%.