Effects of Morphology and Surface Properties of Copper Oxide on the Removal of Hydrogen Sulfide from Gaseous Streams

Abstract

This work studies the effects of microscopic shape, crystallinity, and purity for the chemical reaction of CuO nanoparticles with hydrogen sulfide (H 2 S) to form copper sulfide. Several CuO nanomaterials were prepared via various synthesis techniques, including sol-gel, precipitation, hydrothermal synthesis in the presence of a polymer/surfactant, hydrolysis, and electrospinning, using different copper precursors (nitrate and acetate) and thermal treatment conditions (623 to 1023 K). The synthesized materials, which had different morphologies (flower-like, nanobelt-like, petal-like, spherical, and nanofibers) and physiochemical chemical properties (e.g., crystallite size, surface area and pore volume), were tested for their performance as low-temperature H 2 S sorbents in fixed-bed experiments at 294 K and 1 atm. Despite ostensible differences between the various properties of the tested sorbents, a strong linear relationship was recognized between the sorbents' sulfur removal capacity and crystallite size, independent of changes in the materials' microscopic shape and porosity. Specifically, it was observed that CuO materials with crystallite sizes larger than 26 nm exhibited low sulfur uptake capacities (less than 0.5 wt%) whereas capacity increased linearly (from 0.5 wt% to 12 wt%) with decreasing crystallite sizes for materials with CuO crystallites from 26 nm to 5 nm. In addition, the effect of residual carbon on CuO surfaces was also probed in this study, for the first time, showing that amorphous carbon inherently imparted by the use of a polymer, Polyvinylpyrrolidone (PVP) or poly(ethylene oxide) (PEO), or a surfactant, Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123), in the synthesis procedure inhibits reaction and deleteriously impacts the H 2 S uptake capacity. This trend demonstrates that sorption capacity is strongly influenced by crystallite size and is independent of microscopic shape, surface area and mesopore structure. First principles atomistic simulations explain which surface O anions are most reactive and supportive to the observations.

Lanthanum induced lattice strain improves hydrogen sulfide capacities of copper oxide adsorbents

“…La was chosen because of its large cationic radius (R La /R Cu ≈ 1.5) compared to the more commonly studied additives such as zinc, nickel and cobalt (R x /R Cu ≈ 1.0). This difference in cationic radius is expected to introduce disruptions to the CuO lattice, 23,26 which would cause the formation of O‐atoms that are more reactive with adsorbed surface species, 27 similar to previous studies that have found similar disruptions to the ([Mn, Zn]Fe 2 O 4 , ZnMnO 3 ) lattice by the presence of Mn increases the sulfur sorption of a Fe‐Mn‐Zn‐Ti mixed oxide 28 …”

“…In summary, the laboratory‐based characterization showed that CuO‐La‐2, compared to CuO‐La‐1, features larger crystals but has a higher inclusion of La throughout the CuO phase. These results suggest that the improvement in sulfur uptake by CuO‐La‐2, compared to CuO‐La‐1, is related to a higher concentration of La dopants which induce lattice expansion and strain, which have been previously identified as a means to increase H 2 S capacity of CuO adsorbents 22,23,25 …”

“…The sulfidation of copper oxide is associated with a unit‐cell volume expansion (60%) that disrupts lattice structure of the remaining CuO phase at the CuO‐CuS interface 25 . This disruption is likely a critical factor for the overall extent of sulfidation, and explains, in part, the apparent lack of correlation between capacity and textural properties 22–23 …”

“…CuO‐1 is a commercially produced material (HiFUEL W230; lot number L04Y006; 63.5 wt.% CuO, 25 wt.% ZnO, and 10 wt.% Al 2 O 3 ) purchased from Alfa Aesar. This sample was used as a reference for comparison with the lanthanum containing samples and was studied in previous work 23,24 …”

Hydrogen Sulfide Adsorption by Iron Oxides and Their Polymer Composites: A Case-Study Application to Biogas Purification

“…As in commercial products such as SulfaTreat ® [ 38 ], copper (II) oxide (CuO) was added to Fe 2 O 3 in some samples during the preparation of pellets to enhance the adsorption capacity of the solid phase [ 39 ]. The copper oxide was selected among other possible metal oxides as its sorbent properties towards H 2 S are well known in the literature [ 40 ]. Three different kinds of pellets were produced containing 5%, 10% and 15% w / w CuO in the mixture, respectively.…”