改性杂多酸催化剂的制备及其在甲缩醛合成中的催化活性

Preparation of Supported Heteropolyacids and Cs Modified Salts and their Catalytic Performance in Methylal Synthesis

以Al2O3、SiO2、TiO2、ZrO2、ZrO2 SiO2为载体制备了负载型磷钨杂多酸催化剂及CsXH3-XPW12O40(X=1,1.5,2,2.5,3)磷钨杂多酸铯盐催化剂.考察了这些催化剂在甲醇与甲醛缩合制甲缩醛反应中的催化活性,结果表明:以SiO2、ZrO2、ZrO2 SiO2为载体制备的固载化杂多酸催化剂具有良好的催化活性,而Al2O3、TiO2负载的杂多酸催化剂活性很差.杂多酸铯盐CsxH3-xPW12O40的催化活性则随Cs+离子含量的增加而升高,Cs2.5H0.5PW12O40给出最高的甲缩醛产率;但当H+离子完全被Cs+离子取代后,催化活性显著下降.

Al2O3, SiO2, TiO2, ZrO2, ZrO2/SiO2supported H3PW12O40 and CsxH3-xPW12O40(x= 1, 1.5, 2, 2.5, 3) salts catalysts were prepared. Their catalytic activities in synthesis of methylal from methanol and formaldehyde were first evaluated. The results show that SiO2, ZrO2, and ZrO2/SiO2supported H3PW12O40 give higher activities than Al2O3, and TiO2supported catalysts. For Cs modified salts, the catalytic activities are found to increase with Cs+ ion contents. Cs2.5H0.5PW12O40 gives the highest activity with 40 % yield of methylal. However, when all H+ ions in H3PW12O40 are substituted by Cs+ ion, the activity decreases distinctly.