Researcher: Yousefzadeh, Hamed
Loading...
Name Variants
Yousefzadeh, Hamed
Email Address
Birth Date
5 results
Search Results
Now showing 1 - 5 of 5
Publication Metadata only Supercritical fluid reactive deposition: a process intensification technique for synthesis of nanostructured materials(Elsevier, 2022) Eriş, Gamze; Uzunlar, Erdal; N/A; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Yousefzadeh, Hamed; Akgün, Işık Sena; Barım, Şansım Bengisu; Sarı, Tarık Bercan; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Researcher; Researcher; PhD Student; Researcher; Faculty Member; Department of Chemical and Biological Engineering; N/A; N/A; N/A; N/A; N/A; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); N/A; N/A; N/A; Graduate School of Sciences and Engineering; N/A; College of Engineering; N/A; N/A; N/A; N/A; N/A; 29633Supercritical fluid reactive deposition (SFRD) is a promising process intensification technique for synthesis of a wide variety of nanostructured materials. The enhanced mass transfer characteristics of supercritical fluids (SCFs) coupled with high solubilities of reducing gases in SCFs provide many advantages related to equipment size and time minimization over conventional techniques. Among SCFs, the emphasis has been placed on supercritical CO2 (scCO(2)) which is non-toxic, cheap and leaves no residue on the treated medium. Moreover, in SFRD, multiple processes such as dissolution, adsorption, reaction, and purification are combined in a single piece of equipment which is an excellent example of process integration for process intensification. In this review, the fundamental thermodynamic and kinetic aspects of the technology are described in detail. The studies in the literature on synthesis of a wide variety of nanostructured materials including supported nanoparticles, films, and ion-exchanged zeolites by SFRD are reviewed and summarized. The applications of these materials as catalysts and sensors are described. The review hopes to lead to further studies on further development of this technology for a wide variety of applications.Publication Metadata only Supercritical ion exchange: a new method to synthesize copper exchanged zeolites(Elsevier, 2022) Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Yousefzadeh, Hamed; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; College of Engineering; College of Engineering; N/A; N/A; 29633A new technique termed Supercritical Ion Exchange (SCIE) was developed and used to synthesize Cu-mordenite (Cu-MORS). The ion exchange takes place between the Cu complex (Copper(II)trifluoroacetylacetonate) dissolved in supercritical CO2 (scCO(2)) and the extraframework protons in mordenite zeolite without requiring an aqueous phase. The occurrence of the ion exchange reaction was demonstrated by using H-1 NMR analysis of the high-pressure fluid phase samples and by visual inspection of the fluid phase color change during the synthesis. SCIE resulted in selective ion-exchange inferred by the equilibrium isotherm. The prepared catalysts were used for the stepwise direct methane to methanol (sDMTM) process and results showed that methanol productivity increased linearly with increasing Cu loading up to a certain Cu wt%. Cu-MORS displayed 16% higher methanol productivity as compared to Cu-MORA (prepared by aqueous ion exchange) with the same Cu loading. The results demonstrated the importance of site selective ion-exchange for zeolite catalysis.Publication Metadata only Stepwise conversion of methane to methanol over Cu-mordenite prepared by supercritical and aqueous ion exchange routes and quantification of active Cu species by H2-TPR(Elsevier B.V., 2023) Sushkevich, Vitaly; van Bokhoven, Jeroen A.; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Erkey, Can; Yousefzadeh, Hamed; Bozbağ, Selmi Erim; Faculty Member; Researcher; Researcher; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; College of Engineering; College of Engineering; 29633; N/A; N/ACopper-exchanged mordenite prepared by supercritical ion exchange (SCIE) and aqueous ion exchange (AIE) were investigated in stepwise conversion of methane to methanol. Increasing the oxygen activation temperature and methane reaction time enhances the methanol yield of copper-exchanged mordenite prepared by SCIE (Cu-MORS). The reducibility of Cu-MORS was compared with those of Cu-MORA prepared by aqueous ion exchange (AIE) using H2-TPR. It was demonstrated for the first time that deconvoluted H2-TPR profile coupled with effects of Cu loading and oxygen activation temperature on methanol yield data can be used to distinguish the active Cu sites from inactive ones based on their reduction temperature. The copper species responsible for methane activation were found to be reduced below 150 °C by H2 in both Cu-MORS and Cu-MORA. From the stoichiometry of the reaction of H2 with Cu2+ species, the average number of copper atoms of active sites were calculated as 2.07 and 2.80 for Cu-MORS and Cu-MORA, respectively. Differences in structure of copper species caused by the synthesis routes were also detected by in-situ FTIR upon NO adsorption indicating a higher susceptibility of Cu-MORS towards autoreduction. The results demonstrated the potential of TPR based methods to identify copper active sites and suggested the importance of site selective ion exchange in order to controllably synthesize active Cu species in zeolites. © 2022 The AuthorsPublication Open Access CO2 absorption into primary and secondary amine aqueous solutions with and without copper ions in a bubble column(TÜBİTAK, 2022) Güler, Cansu; Uzunlar, Erdal; Department of Chemical and Biological Engineering; Erkey, Can; Yousefzadeh, Hamed; Faculty Member; Researcher; Department of Chemical and Biological Engineering; College of Engineering; 29633; N/AChemical absorption of CO2 into aqueous amine solutions using a nonstirred bubble column was experimentally investigated. The performance of CO2 absorption of four different primary and secondary amines including monoethanolamine (MEA), piperazine (PZ), 2-piperidineethanol (2PE), and homopiperazine (HPZ) were compared. The effects of initial concentration of amine, the inlet mole fraction of CO2, and solution temperature on the rate of CO2 absorption and CO2 loading (mol CO2/mol amine) were studied in the range of 0.02–1 M, 0.10–0.15, and 25–40 °C, respectively. The effect of the presence of copper ions in the amine solution on CO2 loading was also studied. By comparison of the breakthrough curves of the amines at different operational conditions, it was revealed that the shortest and longest time for the appearance of the breakthrough point was observed for MEA and HPZ solutions, respectively. CO2 loading of MEA, 2PE, PZ, and HPZ aqueous solutions at 25 °C, 0.2 M of initial concentration of amine, and 0.15 of inlet mole fraction of CO2 were 1.06, 1.14, 1.13, and 1.18 mol CO2/mol amine, respectively. By decreasing the inlet mole fraction of CO2 from 0.15 to 0.10, CO2 loading slightly decreased. As the initial concentration of amine and temperature decreased, CO2 loading increased. Also, the presence of copper ions in the absorbent solution resulted in a decrease in the CO2 loading of MEA and HPZ aqueous solutions. In case of PZ and 2PE amines, adding copper ions led to precipitation even at low copper ion concentrations.Publication Open Access A remarkable class of nanocomposites: aerogel supported bimetallic nanoparticles(Frontiers, 2020) Özbakır, Yaprak; Department of Chemical and Biological Engineering; Güneş, Hande; Barım, Şansım Bengisu; Yousefzadeh, Hamed; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 29633Aerogels are a unique class of materials due to their low density, high porosity, high surface area, and an open and interconnected pore structure. Aerogels can be organic, inorganic and hybrid with a plethora of surface chemistries. Aerogel-based products for thermal insulation are already in the market and many studies are being conducted in many laboratories around the world to develop aerogel-based products for other applications including catalysis, adsorption, separations, and drug delivery. On the other hand, bimetallic nanoparticles dispersed on high surface area carriers, which have superior properties compared to their monometallic counterparts, are used or are in development for a wide variety of applications in catalysis, optics, sensing, detection, and medicine. Investigations on using aerogels as high surface area carriers for dispersing bimetallic nanoparticles are leading to development of new composite materials with outstanding properties due to the remarkable properties of aerogels. The review focuses on the techniques to synthesize these materials, their properties, the techniques to tune their pore properties and surface chemistry and the applications of these materials.