More π complexation

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Recent π complexation articles
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Desulfurization of Gasoline over Nanoporous Nickel-Loaded Y-Type Zeolite at Ambient Conditions
Majid Dastanian and Fakhry Seyedeyn-Azad*
Chemical Engineering Department, Engineering Faculty, University of Isfahan, Isfahan, Iran
Ind. Eng. Chem. Res., Article ASAP
DOI: 10.1021/ie100941s
Publication Date (Web): October 11, 2010
Copyright © 2010 American Chemical Society
* To whom correspondence should be addressed. E-mail: fsazad@eng.ui.ac.ir or fsazad@hotmail.com.
AbstractDesulfurization of heavy straight-run gasoline (HSRG) was accomplished over Ni(II)−Y zeolite. Na−Y zeolite, a nanoporous adsorbent, was synthesized and ion-exchanged with NH4NO3 to obtain NH4−Y zeolite. The obtained material was then converted to H−Y zeolite by calcination. Ni−Y zeolite was prepared by solid-state ion exchange (SSIE) of H−Y zeolite using Ni(NO3)2•6H2O. The breakthrough curve for desulfurization of HSRG containing about 140 ppmw of sulfur compounds was obtained in a batch reactor at ambient conditions. The effects of temperature, Ni content in the zeolite framework, and aging of the zeolite on the desulfurization process were investigated. Ni−Y zeolite exhibited a high capability for the desulfurization of gasoline at ambient conditions.
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Adsorptive Desulfurization by Copper Species within Confined Space
Hang Tian, Lin-Bing Sun, Xue-Lin Song, Xiao-Qin Liu*, Yu Yin, and Gu-Se He
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China
Langmuir, Article ASAP
DOI: 10.1021/la101856d
Publication Date (Web): September 30, 2010
Copyright © 2010 American Chemical Society
*Corresponding author. Telephone: +86-25-83587178; fax: +86-25-83587191; e-mail: liuxq@njut.edu.cn.
Abstract
Copper species were incorporated into SBA-15 by solid-state grinding precursor with as-prepared mesoporous silica (SPA). The obtained materials (CuAS) were well-characterized by XRD, TEM, N2 adsorption, H2-TPR, IR, and TG and compared with the material derived from calcined SBA-15 (CuCS). Surprisingly, CuO up to 6.7 mmol•g−1 can be highly dispersed on SBA-15 by use of SPA strategy. Such CuO forms a smooth layer coated on the internal walls of SBA-15, which contributes to the spatial order and results in less-blocked mesopores. However, the aggregation of CuO takes place in CuCS material containing 6.7 mmol•g−1 copper, which generates large CuO particles of 21.4 nm outside the mesopores. We reveal that the high dispersion extent of CuO is ascribed to the abundant silanols, as well as the confined space between template and silica walls provided by as-prepared SBA-15. The SPA strategy allows template removal and precursor conversion in one step, avoids the repeated calcination in conventional modification process, and saves time and energy. We also demonstrate that the CuAS material after autoreduction exhibits much better adsorptive desulfurization capacity than CuCS. Moreover, the adsorption capacity of regenerated adsorbent can be recovered completely.
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Catalysis Today
doi:10.1016/j.cattod.2010.08.020 How to Cite or Link Using DOI
Copyright © 2010 Elsevier B.V. All rights reserved.
Formaldehyde activation by Cu(I) and Ag(I) sites in ZSM-5: ETS-NOCV analysis of charge transfer processes
E. Broclawika, J. Załuckab, P. Kozyrab, M. Mitorajb and J. Datkab
broclawi@chemia.uj.edu.pl
a Institute of Catalysis, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Krakow, Poland
b Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060 Krakow, Poland
Abstract
Adsorption and activation of formaldehyde molecule by copper and silver sites in ZSM-5 was studied by combined QM/MM methodology. ETS-NOCV analysis was applied to decompose the deformation density (the difference between electron densities of composed systems and non-interacting fragments) into independent density flow channels. The analysis disclosed that the bonding of formaldehyde by the metal site may be described in terms of lone pair donation from carbonyl oxygen to the metal and π*-backdonation from metal d orbitals to antibonding orbital of CO. The former one is responsible for the formation of coordinate bond (“dative covalent”) and the latter one for the activation of carbonyl bond. Cu(I) site is more efficient with respect to both processes than Ag(I) one. Zeolitic environment is shown to weaken the bond between formaldehyde and M(I) with respect to free cations for both metals whereas it enhances π*-backdonation in the case of copper and diminishes π*-backdonation in the case of silver. Calculated red-shifts of CO frequencies agree well with the IR-measured ones and correlate with the degree of π*-backdonation which rationalizes as well very good performance of Cu(I) site compared to Ag(I) as the role of zeolitic framework in modifying exchanged cation properties.
Keywords: QM/MM modeling; Cu(I) and Ag(I) sites in MFI; Formaldehyde activation; Electron density transfer channels; ETS-NOCV analysis
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Fuel Processing Technology
doi:10.1016/j.fuproc.2010.08.018
Copyright © 2010 Elsevier B.V. All rights reserved.
COSMO-RS based predictions for the desulphurization of diesel oil using ionic liquids: Effect of cation and anion combination
R. Anantharaja and Tamal Banerjee, a,
tamalb@iitg.ernet.in
a Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
Abstract
Ionic Liquids ILs provide an important alternative in removing aromatic sulphur compounds by Liquid–Liquid Extraction (LLE). A total of 28 anions and 6 cations resulting in 168 possible combinations were screened via COSMO-RS (COnductor Like Screening MOdel for Real Solvents). Initially benchmarking was performed to predict the infinite dilution activity coefficients of thiophene in ionic liquids. Comparison with literature values involving 8 ILs with 20 points gave the average root mean square deviation (RMS) to be 11%. Thereafter artificial simulated diesel, aromatic sulphur compound and the cation and anion combination was used to predict the capacity (C) and selectivity (S) at infinite dilution. In general the selectivities were found to decrease in the following order: thiophene (4–24) > benzothiophene (2–12)> dibenzothiophene (1–7). The different hetero atom (N,S,O) and its location in the cation structure strongly influenced the selectivity and capacity at infinite dilution for all the three aromatic sulphur compounds. It was found that the cation without the aromatic ring combined with anions having sterical shielding effect such as [SCN], [CH3SO3], [CH3COO], [Cl], and [Br] proved to be the most favourable IL for desulphurization. [EMMOR][SCN] proved to be the most viable IL for the removal of all the three aromatic sulphur compounds.
Keywords: COSMO-RS; Ionic liquids; Thiophene; Benzothiophene; Dibenzothiophene; Desulphurization
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