Structure direction in microporous materials: Synthesis and characterization of ferrierite catalysts and novel phosphate molecular sieves.

摘要

Templating in non-aqueous, fluoride mediated syntheses of ferrierite and novel gallium and aluminum phosphates useful for the isomerization of n-butene and deNO{dollar}sb{lcub}rm x{rcub}{dollar} catalysis were investigated using diffraction, computational and spectroscopic techniques.; A synthesis of large single crystals of ferrierite and dodecasil-3C were identified. Single crystal X-ray diffraction, MAS NMR techniques, Raman and IR techniques were used to study the final crystalline products and intermediate gels. Both of the amines present in the synthesis, pyridine and propylamine, seem to have different roles in the growth of ferrierite. Ferrierite, formed under kinetic control, seems to nucleate from a propylammonium species while growth of the crystal is controlled by pyridine during the latter stages of the reaction. Computational studies suggest that the differences in framework stabilities and organic binding energies are not responsible for the transformation of ferrierite into dodecasil-3C, the thermodynamic phase in the reaction. The entropy from the diffusion of the organic species back into solution during the reaction must be enough to initiate the dissolution of the ferrierite and nucleation of dodecasil-3C.; Isomorphous substitution of both main group and transition metals are necessary to generate the Bronsted acid sites necessary for zeolite catalysis. Aluminum substitution into the framework is possible by directly adding reactive aluminum sources to the ferrierite synthesis. The incorporation of aluminum into ferrierite has two main consequences; firstly, propylammonium cations partially charge compensate for the charge on the framework; secondly, two types of pyridine are present in the channels of these aluminosilicate materials. The range of Si/A1 ratios for this topology has now been expanded from purely siliceous to Si/A1 = 3.5, which is lower than naturally occurring ferrierites. Other metals that were able to be incorporated are Ga, Ti, V, Fe, Cr, Ge, B and Mn. Catalysis studies of H{dollar}sp+{dollar}-ferrierite from these fluoride-based syntheses show the same activity for the isomerization of n-butene as commercial ferrierite catalysts. These catalysts also show excellent deNO{dollar}sb{lcub}rm x{rcub}{dollar} activity after ion exchange with Cu and are better than commercially available ferrierite catalysts.; Since the growth of siliceous ferrierite uses two organic structure directing agents, the concept of cooperative-templating was extended into the phosphate systems. New structures ranging from hydrogen-bonded chains, layers and large pore microporous materials were synthesized in the {dollar}rm Gasb2Osb3{dollar}-{dollar}rm Psb20sb5{dollar}-HF phase field. Incredibly, both structure directing agents are incorporated into the channel systems of these materials. Synergistic structure direction using two organic molecules seems to be useful in controlling the shape and size of the pores by carefully choosing the solvent and additional amine. This concept can be extended into any system where organic amines are being used to direct the formation of inorganic frameworks.