Abstract
Synthesis of di-t-butyl-polysulfide from isobutene, hydrogen sulfide and sulfur was carried out over solid base catalysts such as alkali metal and alkaline earth metal oxides loaded on alumina. The performance of the solid base catalysts was compared with that of dicyclohexylamine(liquid catalyst). Alkali metal and alkaline earth metal oxide catalysts were prepared by loading the metal oxide on γ-Al2O3 by the impregnation or ion exchange methods. The reactions were carried out at 120-135°C and 0.3-3 MPa with an autoclave and a semi-batch reaction system in which the mixed gas of isobutene and hydrogen sulfide was bubbled through molten sulfur and the catalyst packed in the autoclave. Liquid products were analyzed with mass spectrometry, X-ray fluorescence spectrometry, HPLC, FT-IR, 1H-NMR and 13C-NMR. The results showed that di-t-butyl-polysulfide was formed in the reactions over all catalysts. The number of bridging sulfurs in the polysulfide was 3 to 9, and an average number of sulfur bridges was 4.5 to 5.5. The distribution of bridging sulfurs in the polysulfide formed over solid base catalyst was almost the same as that for the polysulfide formed over the liquid amine catalyst. Polysulfide yield increased with higher metal loading up to about 0.5 mmol/g-Al2O3 for alkali metal catalysts, and up to about 0.3 mmol/g-Al2O3 for alkaline earth metal catalysts. Further increases in metal loading up to about 1.5 mmol/g-Al2O3 had little effect on the polysulfide yield. The addition of polysulfide to the reaction system considerably increased the reaction rate. The promotion effect was probably due to an increase in solubility of the gaseous reactants in the miscible phase of molten sulfur and polysulfide.
