Preparation, Characterization Of Solid Superacid And Its Application In Resin Deep Processing

Acidic catalyst which is widely used in many important chemicals, plays an important role in recent chemical industry, however, it can also cause environmental pollution; thus it is an effective way to protect the environment by researching and developing new types of environmental friendly catalysts SO42-/MxOy solid superacids. Because acidic catalyst has the ability to activate acid catalytic reaction under mild conditions, and it possesses the properties of simple preparation, high reactivity, good selectivity, and merits of introducing less side reactions, no corrosion to the reactor, no pollution, easy regeneration and reusability, acidic catalyst has become the hotspot in the field of catalytical science, and it could be applied in organic reactions instead of traditional acidic catalysts.In this paper, The series of modified solid superacid SO₄^2-/SnO₂ were prepared by transition metals(Ni, Fe, Co) which possess empty orbits, The acid strength and structure of the solid super acids were characterized by FT IR, XRD, TG-DTA, XPS and BET. Furthermore, theα-terpineol was synthesized by hydration reaction ofα-pinene, catalyzed by solid superacid of nickel modified SO₄^2-/SnO₂; the influencing factors of the hydration have been discussed. The results obtained from experiments and studies were given as follows:(1) Using esterification of acetic acid and n-butanol as evaluation method, catalytic activity of these superacids prepared in different conditions such as different calcination temperature, different concentrations of nickel ion and different calcination times have been researched. By orthogonal experiments we have educed the optimum catalytic conditions of Ni/SO₄^2-/SnO₂: calcination temperature is 500℃concentration of nickel ion is 0.5 mol/L, and calcination time is 2 h. The temperature of calcine is the maximal influencing factor for catalytic activity of catalysts.(2) The physical property such as acid center, structure of crystal, sulfur content, and elemental form of the materials Ni/SO₄^2-/SnO₂ were characterized by FT IR, XRD, TG-DTA and XPS. Using the analysis of FT IR spectra, we knew that on the solid surface, sulfuric group was combined to metal via chelation and bridging connection, forming the main catalytic center. The XRD results showed that tetragonal SnO₂ appeared on the surface of the samples. When the calcination temperature increased, the crystal of tetragonal SnO2 was perfected gradually. The results of TG-DTA showed that the nickel modification can enhance catalytic activity more and exhibit better stability than the catalyst without modification. XPS indicated that the maximum Valence of S (+6) on the samples surface, and the first requisite to have strong activity as solid super acids is S (+6).(3) Deactivation and regeneration of the catalyst were studied. The main reason of deactivation was that the active centers of catalyst covered by adsorbed organic materials and loss of SO42-. The deactivated catalyst could be regenerated by calcining after impregnation.(4) Theα-terpineol was synthesized by hydration reaction ofα-pinene, catalyzed by solid superacid of nickel modified SO₄^2-/SnO₂. The influencing factors of the hydration have been discussed, furthermore the optimum reaction conditions were that the molar ratio ofα-pinene, chloroacetic acid to H2O was 1:1:2, the optimum temperature was 70℃, reaction time was 10 h, and the mass fraction of catalyst was 6%(related to the weight ofα-pinene). Under this condition, the conversion ofα-pinene is over 100%, the selectivity ofα-terpineol is 73.3%. The catalyst has high catalytic activity and selectivity. The result showed that it could significantly increase the conversion and selectivity ofα-pinene by including nickel to the catalyst SO₄^2-/SnO₂.(5) The catalysts Co/SO₄^2-/SnO₂ and Fe/SO₄^2-/SnO₂ were prepared via impregnation and deposition method. Their catalytic activity was testified by esterification of acetic acid and n-butanol, and the best preparation conditions were obtained, the physical properties of catalyst were investigated by FT IR, XRD and TG-DTA.(6) The experiments showed the catalyst SO₄^2-/SnO₂ was well modified by metallic ions, Activity of SO₄^2-/SnO₂ catalysts modified by various metallic ions in esterification of acetic acid and n-butanol was in the order of Ni/SO₄^2-/SnO₂>Fe/SO₄^2-/SnO₂>Co/SO42-- SnO2>SO₄^2-/SnO₂, the results showed Ni/SO₄^2-/SnO₂ had better thermal stability than Fe/SO₄^2-/SnO₂ and Co/SO₄^2-/SnO₂.