多级孔沸石催化合成聚甲氧基二甲醚

Synthesis of polyoxymethylene dimethyl ethers catalyzed by hierarchical zeolite

采用碱处理法改性纳米ZSM-5沸石,采用XRD、FTIR、SEM、NH3-TPD和N2吸附-脱附法对其进行了表征,并将其用于催化甲缩醛与三聚甲醛合成聚甲氧基二甲醚(PODEn,n为聚合度)的反应,考察了碱浓度对催化剂性能的影响。实验结果表明,碱处理对催化剂的晶体结构、孔结构和酸性产生不同程度的影响。适宜的碱浓度不仅对ZSM-5沸石的晶体结构无破坏作用,还可形成多级孔结构,同时提高酸量。与未改性的ZSM-5沸石相比,采用0.8 mol/L的NaOH溶液处理的ZSM-5沸石催化性能最优,目的产物PODE3-5的收率提高了14.4%,初始反应速率加快了1.33倍,催化活性显著提高。

A series of alkali-treated nanocrystal ZSM-5 zeolites were prepared and characterized by XRD,FTIR,SEM,NH3-TPD,N2 adsorption-desorption. The effect of the alkali concentration on the catalytic performances of the catalysts in synthesis of polyoxymethylene dimethyl ethers(PODEn,n represents degree of polymerization) with dimethoxymethane and trioxymethylene was investigated. The results showed that alkali treatment had different effects on the crystal structure,textural and acidity properties of ZSM-5 zeolite. An appropriate alkali concentration not only had no destructive effect on the crystal structure of ZSM-5 zeolite but also was conductive to the forming of a hierarchical pore structure and the increase of acid sites. Compared with untreated zeolite,the ZSM-5 zeolite treated with 0.8 mol/L of NaOH solution had best catalytic performance. The yield of PODE3-5 was increased by 14.4% and the initial reaction rate was increased by 1.33 times,the catalytic performance was signi?cantly improved.