Role of Local Structure on Catalytic Reactivity: Comparison of Methanol Oxidation by Aqueous Bioinorganic Enzyme Mimic (Vanadium Haloperoxidase) and Vanadia-Based Heterogeneous Catalyst (Supported VO4/SiO2)

Yalcin, Ozgen
Erwin, Julie E. Molinari
Gerceker, Duygu
Önal, Işık
Wachs, Israel E.
Although enzymes perform redox reactions at milder reaction conditions than heterogeneous solid catalysts, the origin of this reactivity difference still needs to be resolved. In the present study, the mechanisms and kinetics of methanol oxidation by the aqueous bioinorganic vanadium haloperoxidase (VHPO) enzyme mimic and the heterogeneous solid oxide supported VO4/SiO2 catalyst operating in the gas-solid reaction are compared in order to address the origin of the different reactivities. The molecular level chemical transformations during methanol oxidation by the aqueous VHPO enzyme mimic, possessing the oxo-peroxo O=VO2(-O-C) functionalities, and heterogeneous supported VO4/SiO2 catalysts, containing isolated vanadyl O=V(-O-Si)(3) sites, were monitored with time-resolved in situ vibrational spectroscopy (Raman and IR). Both catalytic reactions proceed via the same methoxy (V-OCH3) reaction intermediate formed upon methanol chemisorption at the bridging V-O-C/V-O-Si bonds. The difference in reactivity is related to the much lower activation energy for breaking the C-H bond of the V-OCH3 intermediate, the rate-determining step, by the highly reactive vanadium peroxo VO2 sites only present for bioinorganic enzyme mimics and absent from heterogeneous catalysts under reaction conditions.


Effect of H2O and SO2 on the activity of Pd/TiO2 catalysts in catalytic reduction of NO with methane in the presence of oxygen
MITOME, Junko; Karakaş, Gürkan; Bryan, Kimberly A.; Ozkan, Umit S. (1998-06-18)
Effect of H2O and SO2 on the NO reduction activity of the Pd/titania catalysts was examined in the NO+CH4+O-2 reaction. Steady-state and transient response experiments were performed using a tubular flow reactor. Isotopically labeled methane, (CH4)-C-13, was used in studying the transient behavior of the catalytic system. Reactor effluents were analyzed by using gas chromatography, mass spectrometry, and chemiluminescense techniques. Steady-state reaction experiments showed that the catalyst has a high acti...
KOCAK, HI; ARAS, L (Elsevier BV, 1990-07-01)
The solution behaviour of Na, Ba, Zn and Al ionomers of methyl methacrylate-methacrylic acid copolymer (P(MMA-MAA)) with different ion contents has been studied by viscosity and dipole moment measurements. Two solvents with different character are chosen for viscosity measurements: dioxane (ε = 2.22) and acetone (ε = 20.7). The expected polyelectrolyte behaviour of the ionomers in acetone is reflected by the viscometric measurements. Mean squared dipole moment 〈μ2〉 values are calculated over a temperature r...
Effect of sodium carbonate on carbothermic formation of hexagonal boron nitride
Akyıldız, Uğur; Sevinç, Naci; Department of Metallurgical and Materials Engineering (2010)
Effect of Na2CO3 on formation of hexagonal boron nitride (h-BN) by carbothermic method has been studied by subjecting B2O3-C and Na2CO3-added B2O3-C mixtures to N2 (g) atmosphere. Na2CO3 amount in the mixtures was changed in the range of 0-40 wt. %. Time and temperature were used as experimental variables. Reaction products were analyzed by XRD and scanning electron microscope. Na2CO3 was found to increase both the amount and the particle size of h-BN similar to CaCO3 [1]. Na2CO3 was found to be less effect...
Effect of thermal treatment on secondary structure and conformational change of mushroom polyphenol oxidase (PPO) as food quality related enzyme: A FTIR study
Baltacioglu, Hande; Bayındırlı, Alev; Severcan, Mete; Severcan, Feride (2015-11-15)
In order to understand the conformational changes of polyphenol oxidase (PPO), which is a food quality related enzyme, after thermal treatment, secondary structure changes of the enzyme were analyzed by using Fourier Transform Infrared (FTIR) spectroscopy and compared with the change in enzyme activity in the temperature range of 25-80 degrees C. Fourier self-deconvolution, neural network (NN) and curve-fitting analysis were applied to the amide I band of FTIR spectra for detail analysis of secondary struct...
Effect of protein aggregation in the aqueous phase on the binding of membrane proteins to membranes
Doebler, R; Basaran, N; Goldston, H; Holloway, PW (Elsevier BV, 1999-02-01)
Analysis of the binding of hydrophobic peptides or proteins to membranes generally assumes that the solute is monomeric in both the aqueous phase and the membrane. Simulations were performed to examine the effect of solute self-association in the aqueous phase on the binding of monomeric solute to lipid vesicles. Aggregation lowered the initial concentration of monomeric solute, which was then maintained at a relatively constant value at the expense of the aggregated solute, as the lipid concentration was i...
Citation Formats
O. Yalcin, J. E. M. Erwin, D. Gerceker, I. Önal, and I. E. Wachs, “Role of Local Structure on Catalytic Reactivity: Comparison of Methanol Oxidation by Aqueous Bioinorganic Enzyme Mimic (Vanadium Haloperoxidase) and Vanadia-Based Heterogeneous Catalyst (Supported VO4/SiO2),” ACS CATALYSIS, pp. 1566–1574, 2020, Accessed: 00, 2020. [Online]. Available: