ABSTRACT
Engelhard Titanium Silicate-2 (ETS-2), a sodium nanotitanate, was surface functionalized by ion exchanging the solid with copper and chromium ions. The ability of this bi-metallic adsorbent to remove H2S at elevated temperatures was assessed using a dynamic breakthrough system and contrasted against an analogous mixed metal oxide, Cu-Cr-O. Unlike Cu-Cr-O, the H2S capacity for Cu-Cr-ETS-2 remains unchanged from 350 °C up to 950 °C. Using ETS-2 as a support for the metals increased the adsorbents surface area and improved its sulfur capacity from 35 mg H2S/g for Cu-Cr-O to 61 mg H2S/g adsorbent for CuCr-ETS-2. The consistent presence of Cu9S5 on the sulfided adsorbents suggests that chromium effectively stabilizes the copper against reduction to metallic copper up to temperatures as high as 950 °C.
ABSTRACT
A mixed-matrix membrane composed of polydimethylsiloxane (PDMS) as the continuous phase and clinoptilolite, a naturally occurring zeolite, as the active phase has been used to decrease the conductivity of water by more than 80% across the membrane. Testing was carried out using a cross-flow configuration at temperatures as high as 160 °C using a constant transmembrane pressure of 8 bar. The simple fabrication method for the membrane, the durability of the system under the test conditions, and a suitable flux rate make such membranes promising candidates for industrial wastewater treatment.
Subject(s)
Dimethylpolysiloxanes/chemistry , Hot Temperature , Membranes, Artificial , Water/chemistry , Zeolites/chemistry , Pressure , Water Softening/methodsABSTRACT
ETS-10, a mixed octahedral/tetrahedral titanosilicate molecular sieve, has a unique architecture where its 0.8 nm pores are lined exclusively with silicon which imparts a high degree of chemical stability, yet the anionic framework can be modified by cation exchange. In this work, the hydrogen-exchanged form of ETS-10 was impregnated with monoethanolamine and the thermal stability and CO2 adsorption characteristics were analyzed. The surface area of the material was characterized by N2 physisorption, the thermal stability of the material assessed through TG-MS experiments, the CO2 capacity was measured via static volumetric adsorption experiments, and the influence of moisture as a carbamate promoter was investigated through a series of gravimetric CO2 adsorption/desorption cycling experiments. Several measurements converge on ~7 wt% monoethanolamine loading which occupies about half of the available pore volume of the sieve. The results suggest that the monoethanolamine is so effectively retained by the molecular sieve that, while the amine is effectively immobilized, under both humid and dry process streams the monoethanolamine is either chemically or sterically hindered and is unable to react measurable quantities of CO2.
ABSTRACT
Titanium silicate molecular sieves contain structural units that are fundamentally different from classical aluminosilicates. In addition to ordered octahedral titanium chains, members of the zorite family contain pentagonal titanium units which project into the main adsorption channels of the framework. We report that the effective pore size of these materials can be controlled by substituting halogens at the O7 sites that cap the pentagonal pyramids projecting into the channel. The quantity and type of halogen used determines the adsorptive properties of the molecular sieve. Barium exchange stabilizes these materials over a wide temperature range (nominally 200-400 degrees C). The barium-exchanged materials do not contract appreciably with calcination, as is observed in related Molecular Gate materials, and thus halogen content can control the pore size of the materials. This new approach to pore size control may have important implications for the purification of multiple classes of compounds, including light hydrocarbons and permanent gases.
