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The energy costs associated with ethane-ethylene separation could be significantly reduced by the development of alternatives to cryodistillation. This work examined ethylene recovery by equilibrium adsorption on two types of titanosilicate molecular sieve adsorbents, Na-ETS-10 and Zn-RPZ. A practical adsorptive separation of industrial process gas, with a measured binary bed selectivity for ethylene over ethane of approximately 5 at 25C and 1 atm, was demonstrated using Na-ETS-10 as the adsorbent. The effects of different binder systems and separation flow rates on the mass transfer properties of Na-ETS-10 were examined in order to optimize the separation. High pressure and low temperature, similar to the working conditions in ethylene production plants, were found to increase the separation factor for these materials. Thermal, steam and microwave desorption methods were compared, and microwave desorption was determined to be the most efficient option for ethylene/ethane desorption and Na-ETS-10 regeneration. / Chemical Engineering

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The processes of development of nuclear weapons resulted in accumulation of thousands of curies of high-level radioactive waste. Liquid waste produced in the US has been stored in carbon steel tanks in highly alkaline (1-3 M NaOH, 6 M sodium salts) media for fifty years and leakage has occurred. One of the approaches to the solution of the problem of radioactive waste is to adsorb the nuclides on highly selective ion-exchange material, solidify in a glass matrix and dispose in a geological formation. The use of the ion-exchange technology is limited by the time of the sorbent-solution contact required to reduce the activity of the streams to acceptable levels. Inorganic ion-exchangers are promising materials due to their high radiation stability, extreme selectivity, and compatibility with the glass matrix. The contact time can be reduced by improving selectivities, kinetics, and capacities of the materials towards the target ions. This can be accomplished in part through understanding of the origin of ion-exchange selectivity. Crystalline zeotypes with minerals sitinakite (ideal formula Na2Ti2O3SiO4??2H2O) and pharmacosiderite (HM3(TO)4(GeO4)x(SiO4)3-x M = Cs+, Na+, K+, T=Nb5+, Ge4+, Ti4+) structures are excellent candidates for selectivity studies because of their ion-exchange properties tunable by alterations of synthetic procedures, and isomorphous framework substitution. The Nb-substitution in titanium sites reduces the framework charge, whereas Ge substitution decreases the unit cell size if in titanium sites and increases if it in silicon sites. The compounds were hydrothermally synthesized in Ti/Si, Ti/Nb/Si, Ti/Ge/Si forms and characterized by structural and ion-exchange studies. The 25% Nb substitution in titanosilicate sitinakite resulted in enhanced selectivity for cesium and additional bond formation of cesium within the channel. The selectivity for cesium in germanium substituted pharmacosiderite also was correlated with the coordination environment within the channel. In the advanced stages of this study semi-crystalline (sodium nonatitanate) and amorphous (monosodium titanate) materials also were considered because of their remarkable strontium selectivity. In situ X-ray diffraction techniques revealed that the sodium nonatitanate precedes the formation of the TS phase in hydrothermal synthesis. This knowledge allowed us to design and synthesize material for combined cesium and strontium removal.

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