Synthesis, Charaterization And Catalytic Properties Of Nobel MOR/MCM-41 Composite Molecular Sieve

Hydrothermal stable MOR/MCM-41 composite sieve was prepared by a desilication method:MOR was firstly dealuminized in an oxalic acid,and the Si/AI molar ratio of MOR is effected by the time of dealuminizaion.Oxalic acid could remove the impurities and amorphous aluminum but keep the basic structure of MOR.And then pre-dissolved in sodium metasilicate to yield a mixture containing the MOR zeolitic fragments.We studied the desilication condition of MOR with orthogonal experiment,and the optimal condition:the alkalinity of sodium metasilicate is 20.4 wt%,the temperature is 60℃,the time is 120 min.The mixture and the oligomeric silicon speicies derived from the hydrolysis of sodium metasilicate were used as silicon and aluminium sources to synthesize the micro-mesoporous composite molecular sieve(MMC) with hexadecyltrimethylammonium bromide(CTAB) as the template.The XRD patterns and TEM images showed the MOR has been completely dissolved, and MMC possessed MCM-41-like structure.N₂ adsorption/desorption and IR spectra demonstrated that fragments with zeolitic structure were present in the walls of MMC,and MMC exhibited bimodal micro-mesopore distributions.The pyridine adsorption IR indicated both of Bronsted and Lewis acid sites existed on the surface of MMC,whereas the surface silanol groups were significantly decreased.Compared with A1-MCM-41,hydrothermal stability of MMC was significantly improved,which could be the results of the introduction of the MOR zeolitic fragments to the walls of MMC,the increased wall thickness,and the decrease of surface silanol groups.The catalytic properties of the composite were studied by alkylation of benzene and 1-dodecene, and showed well activity and selectivity,which would substitute HF as a novel friendly-environment catalyst.