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Title: Computational study of redox reactions in transition metal compounds
Author: Pelekanaki, P.
ISNI:       0000 0004 8502 2750
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2015
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Redox processes taking place at transition metal (TM) ions embedded in inorganic matrices are industrially important, as they are relevant in many technological applications including heterogeneous catalysis, and hence the present computational study focuses on catalytic redox reactions. Of particular importance for oxidation reactions are the microporous aluminophos- phate catalysts (AlPOs) in which Al ions can be replaced by redox-active TMs. We focus on the aerobic oxidation of linear alkanes catalysed by Mn-doped AlPO-5 and AlPO-34. Firstly we compare the results deriving from the use of different functionals (GGA and hybrid exchange functionals). Calculated reaction and activation energies vary by changing the exchange and correlation functionals used in DFT. The rationale is that redox processes change the electronic configuration and number of d-electrons of the TM ions, and hence are expected to be affected by the self-interaction error (SIE) of local DFT functionals. The orbital-dependent solution obtained by inclusion of exact exchange in hybrid-exchange functionals corrects for the SIE. Since there are no experimental investigations to compare our results, we then calculated the Li intercalation potential of LiMPO4 (M=Mn or Fe) using the same functionals as during the delithiation of LiMPO4, the redox chemistry is the same exploited in MnAlPO-5. Amounts of HF exchange between 20-35%, give Li intercalation potential closer to the experimental value. Moreover, we examine the oxidation of primary and secondary carbon atoms of linear alkanes (propane and hexane), and we compare the energetics in different MnAlPOs. We show that the pore size on AlPO-5 is too large to impose structural constraints while the smaller AlPO framework with the use of a longer alkanes can impose some constraints without, however, reversing the relative reactivity of carbon atoms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available