M. Oluş Özbek

• PhD
• Professor (Associate) at Gebze Technical University

CO and H-2 (co-)adsorption, direct and H-assisted CO activation, and surface carbon hydrogenation were investigated on C-terminated chi-Fe5C2(0 0 1) surfaces. Periodic DFT simulations at different surface carbon contents on the carbide surface showed that CO adsorbs preferably linearly on Fe top sites; CO and H-2 adsorptions being stable. The perfe...

This work investigates the CO adsorption on the metallic Cu(100) surface using periodic DFT computations. CO adsorption was studied at varying coverages from 1/16 ML to 1/1 ML for a combination of adsorption positions (4-fold, bridge and top). The results showed that adsorption energies are coverage dependent, however, not enough to identify the ad...

This study investigates the H2 adsorption on Cu⁺, Ni²⁺ and Co²⁺‐exchanged SSZ‐13 (CHA) and SSZ‐39 (AEI) using periodic DFT computations. The most stable Cu⁺ position was found to be the 6‐membered‐ring window for both zeolites. Similarly, for the investigated Ni²⁺ and Co²⁺ loadings on 6‐membered‐ring windows, the third nearest neighbor Al positions...

CO adsorption on the Cu(211) surface was investigated using energy, geometry and vibrational data, which were produced through periodic DFT computations. Adsorption on the (111) terrace, as well as the previously reported top and bridge sites of the step-edges, was studied at 0.25, 0.33, 0.50, 0.66, 0.75, and 1.00 monolayer (ML) CO coverage. Result...

Hydrogen adsorption on Co2+ and Ni2+ exchanged Ultrastable-Y (US–Y) and ZSM-5 are investigated experimentally at 298 K and up to 50 bar as well as theoretically. The experimentally calculated initial isosteric heat of H2 adsorption values are between −28 and −32 kJ/mol for Ni2+-ZSM-5, -16 kJ/mol for Co2+-ZSM-5, -23 kJ/mol for Ni2+-US-Y and −18 kJ/m...

“We study H2 adsorption on Cu⁺‐, Ni²⁺‐ and Co²⁺‐exchanged SSZ‐13 (CHA) and SSZ‐39 (AEI) zeolites using periodic DFT computations. CHA and AEI frameworks have two possible cation sites and a higher symmetry compared to ZSM‐5 (MFI), allowing for computational studies to also consider effects of high‐symmetry periodic frameworks such as electrostatic...

The Front Cover illustrates the application of ion‐exchanged zeolites for hydrogen storage in the fuel cell vehicles. The different zoom levels show hydrogen molecule adsorbed on the extra‐framework cations (Cu+, Co2+, or Ni2+) in CHA and AEI frameworks. Different levels of detail also represent our atomic level understanding and solution to a macr...

Article History Abstract − One of the critical problems in wet-stock management is inaccurate (poor) tank calibration that masks the leakages from the underground storage tanks (USTs). Moreover, obtaining the correct tank parameters or re-calibration is an expensive procedure if not impossible. This study aims to prevent the masking effect of sever...

The adsorption and decomposition of ethanol on Rh(100) was studied as a model reaction to understand the role of C-OH functionalities in the surface chemistry of biomass-derived molecules. A combination of experimental surface science and computational techniques was used: (i) temperature programmed reaction spectroscopy (TPRS), reflection absorpti...

Propylene epoxidation is investigated on RuO2(110) and oxygen added RuO2-Oot(110) surfaces by periodic DFT computational method. The desired product propylene oxide (PO) as well as the undesired products acetone (AC) or propionaldehyde (PA) form on both surfaces through either surface intermediate oxometallopropylene (OMMP) or direct oxygen inserti...

It is important to understand the interaction of C-OH and C=O functional groups of sugar with a catalytically active metal surface for selectively converting of biomass-derived molecules into useful chemicals. Glycolaldehyde (HOCH2CHO), with its C-OH and C=O functional groups, is the smallest molecule to model aspects of the chemistry of sugars on...

Formation of CHx(O) monomers and C1 products (CH4, CH2O, and CH3OH) on C-terminated χ-Fe5C2(001) (Hägg carbide) surfaces of different carbon contents was investigated using periodic DFT simulations. Methane (CH4) as well as monomer (CHx) formation follows a Mars-van Krevelen-like cycle starting with the hydrogenation of surface carbidic carbon, whi...

A control strategy is developed to control molecular weight of recycled poly(ethylene terephthalate), PET, to overcome its degradation through an extrusion process. To obtain dynamic model of a twin screw extruder, steady-state, and unsteady-state experiments were performed. Discrete convolution models between inputs and outputs were obtained. Proc...

The effect of co-adsorbed Cs and Cl on the selectivity of ethylene epoxidation was studied computationally on an Ag2O(0 0 1) surface model. Cl blocks the oxygen vacant sites and prevents oxometallacycle (OMC) formation, which is responsible for aldehyde formation on the oxide surface. Cl also prevents unfavorable surface reconstruction induced by c...

Today ethylene oxide can be produced industrially with ~90 % selectivity through the epoxidation of ethylene over silver catalyst. The past decades there has been a substantial increase in the understanding of the molecular chemistry that leads to high selectivity catalysis. Especially the discovery of an oxometallacycle intermediate that produces...

Ethylene epoxidation was studied as a function of oxygen coverage; for three different surfaces (111), (100) and (110) of three different IB metals using periodical DFT calculations. Oxygen coverage dependence was tested for 11, 25 and 33 % surface oxygen on Ag(111) surface. Calculations showed that increasing oxygen amount increased the exothermic...

The activities of Cu2O(001), Ag2O(001), and Au2O(001) surfaces for direct ethylene epoxidation and alternative paths for EO isomerization are studied. Among these three oxide surfaces, only Ag2O(001) surface enables direct path without a barrier. Au2O cannot regenerate surface oxygen, and overall reaction on Cu2O is endothermic. Furthermore, ring o...

How bizarre: There are two different reaction paths towards formation of ethylene oxide (EO); in addition to that via an oxometallacycle (OMC) intermediate, silver oxide-catalyzed epoxidation of ethylene with surface oxygen, which can occur on an oxide phase as long as no oxygen vacancies are present, is possible. This path is established computati...

It is demonstrated that, on a silver oxide surface, direct formation of ethylene oxide (EO) through the reaction between gas phase ethylene and surface oxygen is possible. The direct reaction channel produces EO selectively without competing with acetaldehyde (AA) formation. The oxometallacycle (OMC) forms on an oxygen vacant surface and reduces EO...

Water and ammonia adsorption mechanisms on anatase TiO2 (001) slab surface are investigated by means of periodic DFT approach. Molecular and dissociative adsorption energies for water are calculated to be − 15 kcal/mol and − 32 kcal/mol, respectively. Similarly, molecular and dissociative adsorption energies of ammonia on the same surface are found...

Introduction Although a great amount of effort has been put in ethylene oxidation catalysis during the last decade, this is not the case for propylene epoxidation. Theoretical studies in this subject have considered silver [1,2] and copper [2] surfaces. However, experiments have shown that using only silver and/or copper catalysts results in comple...