分子筛催化剂催化合成聚甲氧基二甲醚

摘要

Synthesis of polyoxymethylene dimethyl ethers was carried out on HMCM-22 , Al-YNU-1 and MOR zeolites by the condensation of trioxane and methanol or methylal. The crystal structures and surface acidity of the catalysts were characterized by XRD, SEM and NH3-TPD. It was found that DMM2~8 selectivity was influenced by the acid strength and density of zeolites and reaction conditions. HMCM-22 showed much higher selectivity to DMM2~8 than Al-YNU-1 and MOR. Under the optimal conditions, the DMM2~8 selectivity reached 65. 1% and 90. 6% in ME/TRIox and DMM/TRIox systems respectively. It was shown that the moderately strong acid sites were probably responsible for the formation of long chain DMMn , while the strong acid sites werefor DMM.%以甲醇、甲缩醛和三聚甲醛为原料,考察了分子筛孔道结构、晶粒粒径、酸性及反应体系对合成聚甲氧基二甲醚反应性能的影响,并筛选出最佳反应条件。结果表明,HMCM-22分子筛具有良好的催化性能。在最佳反应条件下,以甲醇与三聚甲醛为原料,DMM2~8的选择性为65.1%；而以甲缩醛和三聚甲醛为原料,DMM2~8的选择性则达到90.6%。 NH3-TPD结果表明,弱酸位有利于三聚甲醛解聚为甲醛,中强酸位促进长链分子生成,而强酸位导致DMM为主要产物。