Abstract
The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels. However, its application is seriously hindered by the instability of Cu(I), which is easily oxidized to Cu(II) even under atmospheric environment due to the coexistence of moisture and oxygen. Here, we report the adjustment of zeolite microenvironment from hydrophilic to superhydrophobic status by coating polydimethylsiloxane (yielding Cu(I)Y@P), which isolates moisture entering the pores and subsequently stabilizes Cu(I) despite the presence of oxygen. Cu(I) in Cu(I)Y@P is stable upon exposure to humid atmosphere for 6 months, while almost all Cu(I) is oxidized to Cu(II) in Cu(I)Y for only 2 weeks. The optimized Cu(I)Y@P material after moisture exposure can remove 532 μmol g−1 of thiophene and is much superior to Cu(I)Y (116 μmol g−1), regardless of similar uptakes for unexposed adsorbents. Remarkably, Cu(I)Y@P shows excellent adsorption capacity of desulfurization for water-containing model fuel.
Highlights
The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels
The results show that Cu(I) in Cu(I)Y@P is stable upon exposure to humid atmosphere with 75% relative humidity (RH) for 4320 h (6 months), while almost all Cu(I) is oxidized to Cu(II) in uncoated Cu(I)Y for only 336 h (2 weeks)
These results prove that the superhydrophobic microenvironment effectively prevents instable Cu(I) sites from oxidizing and retains the high activity of PDS-coated Cu (I)Y upon exposure to humid atmosphere
Summary
The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels. It has been demonstrated that Cu (I)-exchanged Y zeolite, namely Cu(I)Y, exhibits unique faujasite (FAU) pore structure, stable inorganic frameworks, and abundant Cu(I) sites[31] These properties endow Cu(I)Y with good ADS performance with regard to uptake and selectivity, making it highly promising for deep desulfurization of transportation fuels[32]. The water content of BP commercial diesels is in the range of 100 and 500 ppmw (parts per million by weight)[35] Such water in fuels accelerates the oxidation of Cu(I), and competes with thiophenic sulfur compounds to interact with active sites in adsorbents[36]. We report a strategy of tailoring the Cu(I)Y microenvironment from hydrophilic to superhydrophobic by coating polydimethylsiloxane (PDS), producing the materials denoted as
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