HZSM-5分子筛用于合成聚甲醛二甲基醚

摘要

Polyoxymethylene dimethyl ethers (PODEn) were synthesized using methanol (MeOH) and trioxymethylene (TRI) as raw materials. Catalytic performance of acidic molecular sieve HZSM-5 catalyst and PODE, selectivity were found to be strongly dependent on silica/alumina ratio, particle size, phosphorus modified and etc. A series of HZSM-5 zeolite samples modified with various contents of phosphorus were prepared by impregnation with an ammonium dihydrogen phosphate. The crystal structure, pore structure, and surface acidity of the catalyst were studied by various characterization techniques such as X-ray diffraction, N2-adsorption, and temperature-programmed de-sorption of NH3. Under the mild reaction conditions of 130℃ and raw materials mass ratio MeOH/TRI = 2, methanol conversion and the PODEn (n = 2-5) selectivity were 95.2% and 62.9%, respectively, by using the Pd-modified HZSM-5 catalyst with the optimum conditions (molar ratio of Si to Al was 50, particle size was 5 μm, low-P2O5 content (w = 0-6%) for the preparation). Catalytic performance of HZSM-5 was higher than that of reference commercial catalysts.%以磷酸二氢铵为前驱体,使用浸渍法制备了一系列不同磷含量改性的HZSM-5分子筛,并结合X射线衍射、N2吸附和氨程序升温脱附等表征结果探讨了催化剂硅/铝比、粒径尺寸、晶体结构、孔结构及表面酸性对其催化甲醇和三聚甲缩反应生成聚甲醛二甲基醚(PODEn)反应性能的影响,同时与商业催化剂进行了比较.结果表明,硅铝比为50,粒径尺寸为5 μm,P2O5含量较低(0～6％)的HZSM-5分子筛表现出较高的催化活性和PODEn选择性.在130℃,原料甲醇和三聚甲醛的质量比为2∶1的优化条件下反应时,三聚甲醛转化率可达到95.2％,PODEn(n=2～5)的选择性为62.9％,略好于商业催化剂.