S_2O_8~(2-)/ZrO_2-SiO_2固体超强酸的合成及其催化合成硬脂酸正丁酯

以五水硝酸锆和九水硅酸钠为锆源和硅源、过硫酸铵为浸渍液,采用共沉淀法制备了S2O82-/ZrO2-SiO2固体超强酸催化剂,并对催化剂进行了XRD,FTIR,SEM表征。以硬脂酸和正丁醇酯化合成硬脂酸正丁酯反应为探针,考察了催化剂制备条件和反应条件对酯化反应的影响。表征结果显示,SiO2的引入延迟了ZrO2的晶化和晶相的转化,当焙烧温度为550℃时,催化剂中四方晶型ZrO2结构和单斜晶型ZrO2结构同时存在,催化剂表面呈针状。在n(硝酸锆)∶n(硅酸钠)=2.0∶1.5、浸渍液过硫酸铵浓度0.5 mol/L、浸渍时间2 h、焙烧温度450℃、焙烧时间3 h的条件下制备的S2O82-/ZrO2-SiO2固体超强酸的催化活性较好。酯化反应的适宜条件为:硬脂酸用量5.7 g、n(硬脂酸)∶n(正丁醇)=1∶3、催化剂用量0.2 g、反应温度120℃、反应时间2.5 h;在此条件下,酯化率可达98.3%。

Preparation of S2O82-/ZrO2-SiO2 Solid Super Acid Catalyst and Its Activity in Synthesis of Butyl Stearate

Solid super acid catalysts S2O82-/ZrO2-SiO2 were prepared by co-precipitation from zirconium(Ⅳ) nitrate and sodium silicate and then impregnation with ammonium persulfate solution,and characterized by means of XRD,FTIR and SEM.The catalytic activity of the catalysts in the esterification of stearic acid and butanol to butyl stearate was investigated.The effects of the catalyst preparation conditions and the esterification reaction conditions on the catalyst activity were studied.The results showed that adding SiO2into ZrO2retarded the crystallization and phase transformation of ZrO2.When the calcination temperature was at 550 ℃,tetragonal ZrO2and monoclinic ZrO2coexisted in the catalysts,and there were some needle-like crystals coated on the surface of the catalysts.Under the catalyst preparation conditions of n(Zr(NO3)4)∶n(Na2SiO3) 2.0∶1.5,(NH4)2S2O8 impregnating solution concentration 0.5 mol/L,impregnating time 2 h,calcination temperature 450 ℃ and calcination time 3 h,the catalytic activity of the S2O82-/ZrO2-SiO2catalyst was high,and estirification rate was up to 98.3% under the optimal esterification conditions of stearic acid dosage 5.7 g,n(stearic acid)∶n(butanol) 1∶3,catalyst dosage 0.2 g,reaction temperature 120 ℃ and reaction time 2.5 h.