H_3PW_(12)O_(40)@C催化剂的原位合成及催化乙酸与正丁醇酯化反应

In-situ synthesis and catalytic properties of H_3PW_(12)O_(40)@C for esterification reaction of acetic acid with n-butanol

以磷钨酸和蔗糖为原料,采用原位合成法制备出活性炭包覆Keggin结构的磷钨酸催化剂30%(w)H_3PW_(12)O_(40)@C,通过正交实验探索出所制备的30%(w)H_3PW_(12)O_(40)@C催化剂催化乙酸和正丁醇液相合成乙酸正丁酯反应的最优工艺条件。采用FTIR,XRD,EDS,SEM,TG-DSC等方法对C包覆前后及重复使用前后的催化剂进行表征。表征结果显示,H3PW12O40较均匀地包覆在C球上,且C包覆后H_3PW_(12)O_(40)仍保持Keggin结构;催化剂使用过程中加剧了团聚,减小了有效比表面积,活性组分发生了溶脱,同时表面吸附了部分有机物;回收催化剂和新鲜催化剂热稳定性能非常相似,但回收催化剂失重率相对增加。正交实验结果表明,在反应温度为125℃、催化剂用量为0.6 g(占反应物总量4.43%(w))、醇酸摩尔比为1∶1、反应时间为3.0 h的最优工艺条件下,酯化率可达97.3%;催化剂重复使用到第5次时,酯化率仍可达77.8%。

The activated carbon-coated Keggin-type phosphotungstic acid（30%（w）H3PW12O40@C） catalyst was prepared from phosphotungstic acid and sucrose by in-situ synthesis method. The synthesis of n-butyl acetate from acetic acid and n-butanol with 30%（w）H3PW12O40@C as catalyst was studied and the optimum technical conditions were determined by orthogonal experiment. The catalysts were characterized by FTIR,XRD,EDS,SEM and TG-DSC before and after carbon-coated and reuse. The characterization results showed that H3PW12O40 was evenly distributed on active carbon and still kept Keggin structure after carbon-coated. The agglomeration of the catalyst was increased,the active surface area of the catalyst was decreased,the dissolution of active ingredient and the adsorption of some organic compounds on the surface were observed during the use of the catalyst. The thermal stability of the recovery catalyst and the fresh catalyst was very similar,but the loss rate of recovery catalyst was relatively increased. The orthogonal experiment results showed that the esterification ratio could attain 97.3% under the optimum technical conditions as follows：the reaction temperature was 125 ℃,the amount of catalyst was 0.6 g（accounting for 4.43%（w） of the total reactants）,the molar ratio of n-butanol to acetic acid was 1∶1 and the reaction time was 3.0 h. The esterification ratio still attained 77.8% when the catalyst was reused for 5 times.