原位法制备H_3PW_(12)O_(40)/SiO_2催化剂及其催化性能

Preparation of 12-tungstophosphoric acid/SiO_2 catalyst by in-situ method and its catalytic performance

用原位合成法制备了不同固载量的磷钨酸催化剂H3PW12O40/SiO2作催化剂,通过FT-IR、XRD等手段对催化剂进行表征。结果表明,在煅烧温度为200℃,活化时间为4h,H3PW12O40负载量为20%时,原位法制备的催化剂在载体孔壁中高度分散的磷钨酸仍然保持了Keggin特征结构,且与SiO2材料的表面羟基存在一定的化学相互作用。对苯甲醛1,2-丙二醇缩醛合成的催化性能研究表明,固定苯甲醛用量为0.2mol,在n(苯甲醛)∶n(1,2-丙二醇)=1∶1.5,催化剂的用量占反应物料总质量1.0%,环己烷用量为8mL,反应时间为60min条件下,产品收率可达88.5%。催化剂使用5次以后,催化活性仍然保持在接近51.7%。

The different loading catalysts of 12-tungstophosphoric acid/SiO2 were prepared by in-situ method. The structure and properties of the catalysts were characterized by FT-IR spectroscopy,X-ray diffraction.It was found that the catalyst containing 20 % H3 PW12 O40 by calcination at 200 ℃ for 4 h showed a higher catalyt-ic activity.The results show that the 12-tungstophoaphoric acid highly dispersed in hole of SiO2 still keeps the Keggin structure,and has certain chemical interaction with surface hydroxy for SiO2 .The catalytic properties of synthetic benzaldehyde 1,2-propanediol acetal show that H3PW12 O40/SiO2 catalyst have high catalytic activity. The optimum conditions are：molar ratio of benzaldehyde to 1 ,2-propylene was 1∶1 .5 ,the mass ratio of the catalyst used to the reactants was 1 .0%,the volume of cyclohexane as the water-carrying agent was 8 mL,and the reaction time was 60 min,the yield of its can reach 88.5%,and show excellent reusabity.