The
H2S breakthrough capacity of copper-exchanged Engelhard
Titanosilicate-2 (ETS-2) was measured at temperatures up to 950 °C
and it was found that the adsorbent efficiency remains unchanged across
the entire temperature range. Below 750 °C, the adsorption capacity
at breakthrough is 0.7 mol of H2S per mole of copper while
above 750 °C the capacity of the adsorbent is halved. The change
in H2S capacity is due to Cu2+ reduction by
the H2 which is formed through the thermal dissociation
of H2S. The adsorbent shows good potential for use over
a wide range of operating temperatures in H2S scrubbing
processes.
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.
A comparative study between nanotitanate doped with different metals (copper, copper−chromium, and cerium) is executed under gasification conditions in order to investigate their maximum H 2 S removal ability and their breakthrough behavior. Therefore, the sorbent is placed in a fixed-bed reactor and exposed to the H 2 S containing gas flow at temperatures ranging from 75 to 950 °C. Online analysis is done by a mass spectrometer. The sorbents are also tested by the offline analytical techniques X-ray diffraction (XRD) and scanning electron microscopy (SEM) after the experiments to provide detailed information about their elemental and crystalline composition. The results indicate Cu-ETS-2 as the most effective H 2 S-scrubber among the tested sorbents. The lowest H 2 S concentration in the outlet gas is always achieved in water rich gas. Additionally, the H 2 S capacity is nearly always higher for the water rich gas than in the hydrogen rich gas.
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.
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