制备了一系列金属离子修饰的磷钨酸盐(MXH3-2 XPW12O40,M=Zn,Cu,Cs,Ag)催化剂,并将磷钨酸银盐(Ag3PW12O40)用于水解葡萄糖制备乙酰丙酸的实验中。采用FTIR、XRD、SEM和EPMA等技术对磷钨酸盐性能进行了表征,并分析了磷钨酸银盐催化剂在反应前后结构和表面元素相对含量的变化。考察了反应温度、反应时间、催化剂用量和葡萄糖浓度等对乙酰丙酸得率的影响。结果表明:合成的磷钨酸盐具有磷钨酸的Keggin结构,并且Ag3PW12O40催化剂在多次使用后Keggin结构没有被破坏。在催化合成反应中,在反应温度200℃、反应时间2h、Ag3PW12O40催化剂用量0.7g和葡萄糖浓度40g.L-1的条件下,乙酰丙酸的最大得率可达到81.61%,催化剂可重复利用。
A series of metal-modified heteropolyacid salt catalysts(MXH3-2XPW12O40,M=Zn,Cu,Cs,Ag)were prepared,and the solid heteropolyacid salt Ag3W12O40 was used in hydrolysis of glucose to produce levulinic acid.The surface structures of different heteropolyacid salt catalysts were characterized by means of FTIR,XRD.The surface structures and element relative mass content change of the fresh and used Ag3W12O40 catalyst were also analyzed by means of FTIR,XRD,SEM and EPMA.The effects of such factors as reaction temperature,reaction time,amount of catalyst and glucose concentration on the yield of levulinic acid were investigated.Experimental results showed that the MXH3-2XPW12O40 heteropolyacid salt catalysts kept primary Keggin structure,and Ag3W12O40 catalyst had the structure of Keggin after reuse for several times.It was found that the highest yield of levulinic acid was 81.61%(mole) under the conditions of reaction temperature 200℃,reaction time 2 h,Ag3PW12O40 catalyst dosage 0.7 g and glucose concentration 40 g·L-1.The catalyst could be used repeatedly.