Effect of rare earth modification on structure and catalytic properties of SO42-/ZrO2 solid acid catalyst
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摘要: 采用共沉淀法和浸渍法在不同条件下制备了稀土-SO42-/ZrO2系列固体酸催化剂。使用废油脂与甲醇的酯交换反应评价了催化剂活性,并通过X射线衍射、红外光谱、比表面积测定表征方法考察了催化剂结构和性能的关系。结果表明,La摩尔掺杂量4%、焙烧温度600℃时制得的SO42-/ZrO2-La2O3催化剂活性最高,此时脂肪酸甲酯的产率为64.68%,且具有较好的重复使用性。稀土的引入使活性四方相ZrO2更加稳定,600℃焙烧使催化剂既具有较多活性四方相ZrO2,又具有较大比表面积,从而提高了催化剂活性。催化剂中形成了固体超强酸结构,且改性后酸强度增大,催化剂活性中心数目增加。Abstract: The rare earth-promoted SO42-/ZrO2 solid super acid catalyst was prepared by the co-precipitation and impregnation method under different conditions. The catalytic properties of the samples were evaluated through transesterification of waste oil and methanol and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and BET surface area measurement. The results showed that among all the prepared samples the one that was calcined at 600℃ with La doping 4% had the highest production rate of 64.68%. An analysis of XRD patterns revealed that the incorporation of rare earth into tetragonal zirconia stabilizes the compound, and the calcination at 600℃ increases the reactivity of the catalyst by producing a greater fraction of active tetragonal zirconia with a larger surface area. It could be seen from the FT-IR spectra that super acid structures were formed in the catalysts and the acidity was strengthened remarkably and the activated centre of the catalyst were increased.
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Key words:
- solid super acid /
- rare earth elements /
- biodiesel /
- transesterification /
- calcination temperature
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