Silbernagel, Rita Marie (2016-05). Tetravalent Metal Phosphonate-Phosphate Hybrids as Catalyst Supports and Ion Exchange Materials. Doctoral Dissertation.
This work centers on recycling of Rh catalysts and utilizing ion exchange to separate nuclear waste. In the area of Rh-type catalyst supports, non-porous zirconium phosphate nanoplatelets (ZrP) were utilized to provide sufficient outside surface area while still being easily separable from the reaction mixtures. First, a phosphine linker containing an ethoxysilyl group, (EtO)3Si(CH2)3PPh2, is reacted with ZrP. Addition of Wilkinson's catalyst ClRh(PPh3)3 to the phosphine-modified ZrP gives the immobilized catalyst. In the absence of pore diffusion, the catalytic hydrogenation of 1-dodecene using the Rhtype immobilized catalyst proceeds with unprecedented speed and the catalyst can be recovered and recycled 15 times. New materials were synthesized that are comprised of Zr/Sn phosphonate-phosphate hybrids. The general formula for these materials is M(O3PC6H4PO3)1-x/2(APO4)xonH2O, where M = Zr^4+, Sn^4+; A = H, Na, K; and x = 0, 0.5, 0.8, 1.0, 1.33, 1.6. These materials have a preference for ions of high charge (3+, 4+) over those with lower charge (1+, 2+). From this charge-based affinity and pH modification, separations can be achieved with Nd^3+/Cs^+ separation factors >= 100. The stability of these materials to 3.18 MGy gamma radiation was also observed with performance and structure retained. Greater than 99% removal of radioactive Am(III) from solution was obtained. Similar materials have also been utilized to explore rare earth recovery from Compact Fluorescent Lamps and Cr(VI) removal from wastewater solutions.