Research On Catalytic Synthesis Of Citrate Ester By Several Solid Acid Catalysts

In this work, various solid acid catalysts were synthesized and characterized. The article reported that trioctyl citrate (TOC) was synthesized using citric acid and n-trioctyl as reaetants in the presence of solid acid as catalyst.Pillared super solid acid catalysts of (NH₄)2SO₄/Al-MMT, (NH₄)2SO₄/Al-PGS, SO₄^2-/Al-MMT, SO₄^2-/Fe-MMT, SO₄^2-/Fe-PGS were prepared by ion exchange and modified with sulfuric acid or (NH₄)2SO₄. Trioctyl citrate is synthesized using them as catalyst. Especially, it's reached to 97% when SO₄^2-/Fe-MMT are used as the catalyst. Without any treatment for over 5 times, the yield of trioctyl citrate fell to 87% for SO₄^2-/Fe-MMT. In particular, the catalyst can be easily seperated and recycled, it has high catalytic capability without environmental pollution. Thus, it is a kind of solid acid catalyst.Using cetyltrimethyl ammonium bromide as a template, mesoporous TiO₂ was synthesized by hydrothermal method. Solid superacid (SO₄^2-/Ti-TMS) was prepared by wet impregnation method with sulfuric acid. Trioctyl citrate is synthesized using SO₄^2-/Ti-TMS as catalyst. It was founded that the esterification yield could up to 97.9% when the molar ratio of citrate acid to octanol is 1:4, the weight of catalyst is 0.2 g and reaction time is 5 h at 170℃. Without any treatment for over 5 times, the advantage of this catalyst was high catalytic capability and good reusability. SO₄^2-/Ti-TMS was studied in the synthesis of tributyl citrate, esterification of citric acid was 94.4%.Mesostructured aluminium-silicon was studied and was impregnated with sulfuric acid. Its catalytic activity in the synthesis of trioctyl citrate was investigated.The method of copolymerization and sulfation modification on pillared clay were studied to prepare mixing Fe/Al pillared clay solid superacid, marked SO₄^2-/Fe/Al-MMT. The use of SO₄^2-/Fe/Al-MMT on the catalytic synthesis of trioctyl citrate was studied. The best effects is the molar ratio of citrate acid to octanol is 1:5, the weight of catalyst is 10% of citrate acid and reaction time is 5 h at 160℃, the yield of trioctyl citrate can be reached to 96.6%.