分子筛催化剂催化合成聚甲氧基二甲醚

Synthesis of polyoxymethylene dimethyl ethers over zeolite catalysts

摘要: 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，DMM_2~8的选择性为65.1%；而以甲缩醛和三聚甲醛为原料，DMM_2~8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。

Abstract: 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 DMM_2~8 selectivity was influenced by the acid strength and density of zeolites and reaction conditions. HMCM-22 showed much higher selectivity to DMM_2~8 than Al-YNU-1 and MOR. Under the optimal conditions, the DMM_2~8 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 DMM_n, while the strong acid sites werefor DMM.