硫酸化剂和制备方法对锆基固体酸催化剂的结构和性能的影响

The effect of sulfating agents and preparation methods on the structure and properties of zirconium-based solid acid catalysts

采用沉淀法制备ZrO2氧化物,用氯磺酸和硫酸对其进行改性制备了Zr基固体酸催化剂,以XRD、BET和NH3-FTIR等手段考察了制备条件对催化剂晶相结构和表面性质的影响,研究了催化剂结构与其对棕榈油酯化反应的催化活性之间的关系。NH3-FTIR表明催化剂表面有B酸和L酸中心的生成。硫酸化剂的种类及其引入顺序都将影响催化剂的晶相结构和孔结构。酸的引入将阻止ZrO2.nH2O在焙烧时直接向单斜相ZrO2转变,氯磺酸将使ZrO2.nH2O转变为四方相ZrO2,而硫酸将导致四方相ZrO2和Zr(SO4)2.5H2O的生成。以氯磺酸改性的四方相和单斜相ZrO2基催化剂均具有很高的催化酯化活性,比硫酸改性的S-Z固体酸催化活性高。CS-ZrO2固体酸催化活性最高,在醇油比6:1、催化剂用量7 wt%、温度338 K和常压下反应2 h,棕榈油的酯化率可达98.9%。

Zirconium-based solid acid catalysts, modified with chlorosulfonic acid and sulfuric acid, were prepared and characterized using XRD, BET and NH3-FTIR to investigate the effect of preparation conditions on the crystalline structure and surface properties of the catalysts. The relationship between the structure and the activity of the catalysts for the esterification of palm oil was studied. NH3-FTIR revealed that both Brφnsted acid sites and Lewis acid sites existed on the surface of zirconium-based catalysts. It was found that the kind and immersing order of sulfating agents affected the crystalline structure and pore structure. The transformation of ZrO2 · nH2O into monoclinic phase of zirconia in calcination at 823K, was hindered by the impregnation of sulfating agents onto ZrO2 [ nH2O. ZrO2 · nH2O was transformed to tetragonal phase of zirconia when it was modified with chlorosulfonic acid,and tetragonal phase of zirconia and Zr（ SO4 ）2 [ 5H2O would form when ZrO2 · nH2O was modified with sulfuric acid. Both tetragonal and monoclinic phase of zirconia modified by chlorosulfonic acid displayed higher catalytic activity for esterification than S-Z catalyst modified by sulfuric acid. High catalytic performances ,98.9% conversion of palm oil, with 6：1 of methanol/oil molar ratio and 7 wt% of catalyst at 338K within 2 h,was achieved over CS-ZrO2 solid acid catalyst.