Density Functional Theory Study on the Role of Ceria Addition in TixCe1–xO2 Adsorbents for Thiophene Adsorption

Guo, Jiahua; Janik, Michael J.; Song, Chunshan

doi:10.1021/jp2063996

Cited by 24 publications

(37 citation statements)

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“…However, the free energy of adsorption of an O 2 molecule on stoichiometric Ce-TiO 2 surfaces with water dissociatively Table 2. Energetics of the Adsorption Cycle on the Pure and Doped (001) Surface in eV a sulfoxide reaction energy [3] sulfoxide activation barrier [3] sulfone reaction energy [4] (0,0,1) migration energy [5] (1,0,1) migration energy [5] (1,0,0) migration energy [ a Reaction step labels refer to Figure 1. The final migration step reaction energy is given with the sulfone migrating to any of the three surfaces considered.…”

Section: Resultsmentioning

confidence: 99%

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Active Sites on Ti–Ce Mixed Metal Oxides for Reactive Adsorption of Thiophene and Its Derivatives: A DFT Study

et al. 2015

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Density functional theory was used to investigate the mechanistic aspects of the adsorption of sulfurcontaining compounds over Ti−Ce mixed metal oxides. We elucidate the promotional effect of the Ce dopant on TiO 2 and report the importance of oxygen vacancy-bound molecular oxygen as an active site on Ti−Ce mixed metal oxides for adsorption of thiophenic sulfur. The presence of surfaceactivated molecular oxygen leads to the oxidation of the sulfur, thus providing strongly bound sulfoxide and sulfone species. Ce doping of TiO 2 makes the oxidation process feasible both thermodynamically and kinetically. Surface oxygen vacancy sites act as catalytic sites in an adsorption cycle. DRIFTS results corroborate the presence of vacancy bound molecular oxygen. Our DFT calculations also examine thiophene and methyl-, dimethyl-, benzo-, and dibenzothiophenes adsorbed on TiO 2 and Ce-doped TiO 2 (001), (101), and (100) surfaces.

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Section: Resultsmentioning

confidence: 99%

“…The adsorption energy of molecular oxygen on stoichiometric TiO 2 and Ti-CeO 2 surfaces is close to 0 eV, 5,9 and the free energy of adsorption is significantly positive. Surface O vacancies, however, serve as active sites to trap O 2 and allow for subsequent adsorption for thiophene.…”

Section: Introductionmentioning

confidence: 86%

Active Sites on Ti–Ce Mixed Metal Oxides for Reactive Adsorption of Thiophene and Its Derivatives: A DFT Study

et al. 2015

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“…Computational studies suggested that chemisorbed oxygen species on the TiO 2 surface played an important role in promoting ADS, [14] thus suggesting highly selective adsorption through the formation of sulfoxide/sulfone species. [15] Our previous computational work [16] also suggested a number of possible effects of Ce addition to TiO 2 , although it only examined the adsorption thermodynamics and was inconclusive regarding the key impact of Ce addition. We hypothesized that the introduction of chemisorbed oxygen species during the ADS process could increase the sorption capacity for TiO 2 -CeO 2 mixed oxides.…”

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“…Pure anatase and Ce-doped anatase (001) surfaces were considered. A Ti 16 O 32 cell with four layers of TiO 2 was used for the calculation. The top two layers were relaxed during the optimization.…”

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Air‐Promoted Adsorptive Desulfurization over Ti_0.9Ce_0.1O₂ Mixed Oxides from Diesel Fuel under Ambient Conditions

et al. 2013

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Herein, we demonstrate the high-capacity adsorptive desulfurization of commercial diesel by using TiO 2 -CeO 2 mixed-oxide adsorbents with the addition of air to the fuel and we use density functional theory calculations to explain the unique chemical functionality of the absorbents by detailing a new catalytic adsorption mechanism. The ultra-deep desulfurization of diesel fuel has attracted widespread attention, owing to the stringent government regulations for sulfur content in the transportation fuels for the protection of the environment and human health.[1] Since 2006, US EPA regulations have required that the sulfur content in diesel fuel be lower than 15 parts per million by weight (ppmw). [1a,b] Moreover, diesel fuel has been considered as a preferable feedstock for some on-site and on-board fuel-cell applications, owing to its high energy density, ready availability with existing infrastructures, and safety in terms of its delivery and storage. However, sulfur concentrations higher than 1 ppmw lead to the poisoning of reforming catalysts, water-gas-shift catalysts in fuel processing, and electrodes of proton-exchange membrane fuel cells (PEMFCs).[2] Therefore, ultra-deep diesel desulfurization is an important research subject worldwide.[3]One energy-efficient desulfurization approach for producing ultra-clean fuels with sulfur concentrations < 1 ppmw is selective adsorption. Selective adsorption involves the preferential adsorption of organosulfur compounds onto a solid adsorbent. Another approach, adsorptive desulfurization (ADS), provides a promising path for decreasing the sulfur content to less than 1 ppmw under ambient or mild conditions without the use of H 2 . To date, several attempts have been made to develop adsorbents for the desulfurization of liquid fuels, including pcomplexation sorbents, [4] immobilized p-acceptor sorbents, [5] metal-organic frameworks (MOFs), [6] Ni-based sorbents, [7] graphene and oxygen-functionalized carbon sorbents, [8] and softacid-supported sorbents.[9] However, all of these sorbents have drawbacks for the selective ADS from current commercial diesel fuel for the production of ultra-clean fuel under ambient conditions. These challenges include: 1) weak adsorption affinity, owing to steric hindrance of the refractory alkylated sulfur compounds, [10] and 2) poor adsorption selectivity, owing to competitive adsorption between trace amounts of sulfur compounds (< 15 ppmw) and relatively large amounts of polyaromatics (5-10 wt. %).[11] Therefore, new ADS approaches have to be developed for selective ADS from commercial diesel fuel to achieve ultra-clean fuel with sulfur content below 1 ppmw.Metal oxides have been widely used in adsorption and separation processes, owing to their unique advantages, such as regenerability, controllable composition and functionalities, and tunable surface area and pore size. Metal oxides have shown great promise for hot-coal-gas desulfurization through high temperature sulfidation, [11, 12] yet their use in liquid-phase desulfurization ...

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A Novel Pd Precursor Loaded γ‐Al₂O₃ with Excellent Adsorbent Performance for Ultra‐Deep Adsorptive Desulfurization of Benzene

Xie

Dai

et al. 2023

Adv Funct Materials

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Fabricating highly water‐soluble and chlorine‐free precursors from Pd complexes remains challenging. Here, a novel Pd precursor (ammonium dinitrooxalato palladium(II) ((NH4)2[Pd(NO2)2(C2O4)]·2H2O)) is synthesized to address this challenge. Additionally, a Pd/Al2O3 adsorbent is prepared using γ‐Al2O3 as a base material to host Pd. The ligand action of the Pd complex forms single Pd atoms and Pd sub‐nano clusters on the surface of γ‐Al2O3. Pd/Al2O3‐4 as an adsorbent is evaluated using the benzene ultra‐deep desulfurization procedure, wherein thiophene is used as a probe molecule. The sulfur adsorption capacity of Pd/Al2O3‐4 is 1.76 mg g−1 for the ultra‐deep adsorptive desulfurization of benzene at a sulfur concentration of 50 ppm. The sulfur adsorption capacity of the new Pd/Al2O3‐4 adsorbent is 21.8% higher than that of a commercial Pd/Al2O3 adsorbent. In addition, the stability and durability of Pd/Al2O3‐4 are investigated at a sulfur concentration of 1 ppm. The Pd/Al2O3‐4 adsorbent achieves ≈100% thiophene removal after 434 h, which is 62 h more than the time required by the commercial Pd/Al2O3 adsorbent. The novel Pd precursor shows excellent potential for industrial applications, and the Pd/Al2O3‐4 adsorbent can be produced on a mass scale of 500 kg per batch.

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Density Functional Theory Study on the Role of Ceria Addition in Ti_xCe_1–xO₂ Adsorbents for Thiophene Adsorption

Cited by 24 publications

References 61 publications

Active Sites on Ti–Ce Mixed Metal Oxides for Reactive Adsorption of Thiophene and Its Derivatives: A DFT Study

Active Sites on Ti–Ce Mixed Metal Oxides for Reactive Adsorption of Thiophene and Its Derivatives: A DFT Study

Air‐Promoted Adsorptive Desulfurization over Ti_0.9Ce_0.1O₂ Mixed Oxides from Diesel Fuel under Ambient Conditions

A Novel Pd Precursor Loaded γ‐Al₂O₃ with Excellent Adsorbent Performance for Ultra‐Deep Adsorptive Desulfurization of Benzene

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Density Functional Theory Study on the Role of Ceria Addition in TixCe1–xO2 Adsorbents for Thiophene Adsorption

Cited by 24 publications

References 61 publications

Active Sites on Ti–Ce Mixed Metal Oxides for Reactive Adsorption of Thiophene and Its Derivatives: A DFT Study

Active Sites on Ti–Ce Mixed Metal Oxides for Reactive Adsorption of Thiophene and Its Derivatives: A DFT Study

Air‐Promoted Adsorptive Desulfurization over Ti0.9Ce0.1O2 Mixed Oxides from Diesel Fuel under Ambient Conditions

A Novel Pd Precursor Loaded γ‐Al2O3 with Excellent Adsorbent Performance for Ultra‐Deep Adsorptive Desulfurization of Benzene

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Density Functional Theory Study on the Role of Ceria Addition in Ti_xCe_1–xO₂ Adsorbents for Thiophene Adsorption

Air‐Promoted Adsorptive Desulfurization over Ti_0.9Ce_0.1O₂ Mixed Oxides from Diesel Fuel under Ambient Conditions

A Novel Pd Precursor Loaded γ‐Al₂O₃ with Excellent Adsorbent Performance for Ultra‐Deep Adsorptive Desulfurization of Benzene