Researcher:
Dizaji, Azam Khodadadi

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Azam Khodadadi

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Dizaji

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Dizaji, Azam Khodadadi

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2020 - 20213

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    Enhancement in pervaporative performance of PDMS membrane for separation of styrene from wastewater by hybridizing with reduced graphene oxide
    (Academic Press Ltd- Elsevier Science Ltd, 2020) Majooni, Y.; Mortaheb, Hamid Reza; Department of Chemical and Biological Engineering; Dizaji, Azam Khodadadi; Researcher; Department of Chemical and Biological Engineering; College of Engineering; N/A
    The removal of styrene from wastewater by pervaporation was investigated by using composite PDMS membranes filled with reduced graphene oxide on PES support layers. Graphene oxide was synthesized through modified Hummers' method and then chemically reduced. The filler was characterized by TEM, SEM, XRD, and AFM. The top layers with different PDMS molecular weights were cast on the PES supports, which were prepared by phase inversion method. The characterizations of prepared membranes were investigated by SEM, AFM, contact angle measurement, TGA, and DSC. It was observed that presence of the filler in the polymeric matrix controls the swelling of the membrane and enhances its solubility parameter in favor of styrene. Moreover, it significantly improves the thermal stability of the membranes. The mechanism of separation in the process was found to be affected mainly by enhancing in the membrane's solubility rather than in its diffusivity. The pervaporative performance of prepared membranes showed their great affinity toward styrene so that the separation factor of the optimum membrane (M2/S) was increased about 250% (600.4 in comparison to 241.4 for the unfilled membrane) while its total flux was decreased from 772.5 g m(-2).h(-1) for the unfilled membrane to 321.9 g m(-2).h(-1). Increasing the molecular weight of PDMS lowered the optimal rGO content due to the complexity of the diffusion path and occupation of free volume by longer polymer chains. Accordingly, a lower total flux (124.7 g for high MW compared to 718.0 g m(-2).h(-1) for low MW) and higher separation factor (822.5 m(-2).h(-1) for high MW compared to 230.8 for low MW) were yielded for the same filler content (0.1 wt% rGO).
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    MCM-41-supported tungstophosphoric acid as an acid function for dimethyl ether synthesis from CO2 hydrogenation
    (Pergamon-Elsevier Science Ltd, 2021) N/A; Department of Chemical and Biological Engineering; N/A; Department of Chemical and Biological Engineering; Şeker, Betül; Dizaji, Azam Khodadadi; Balcı, Volkan; Uzun, Alper; Researcher; Researcher; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 59917
    We mixed an MCM-41-supported tungstophosphoric acid (TPA) catalyst with a commercial CuO-ZnO Al2O3 methanol synthesis catalyst (MSC) and optimized the mixing ratios/reaction conditions towards high performance in dimethyl ether (DME) synthesis by CO2 hydrogenation. First, a series of TPA/MCM41 catalysts were synthesized at a TPA loading of 30, 40, 60, and 80 wt% and characterized by combining various techniques. The results of X-ray fluorescence spectroscopy confirmed the loading of stoichiometric TPA amounts in each TPA/MCM-41 catalyst, while the N-2 adsorption-desorption measurements and the scanning transmission electron microscopy images were showing the decoration of MCM-41 pores with TPA clusters. X-ray diffraction and infrared spectroscopy results identified some structural distortions in TPA clusters especially at relatively low loadings and the results of temperature programmed desorption of ammonia measurements quantified the consequences of these changes in TPA structure on the acid properties. The optimized TPA loading in TPA/MCM-41 was 60 wt% with CuO-ZnO Al2O3:TPA/MCM-41 = 4:1 at 40 000 mL CO2 g(cat)(-1) h(-1) and H-2:CO2 = 3:1 at 250 degrees C and 45 bar. At these conditions, the rate was 1551.5 gDME kg(cat)(-1) h(-1), to the best of our knowledge, the highest rate for the direct DME synthesis from CO2 hydrogenation in a single-pass reactor. This performance was originated from the high density of acid sites in TPA/MCM-41 owing to exceptionally high surface area of MCM-41 offering a monolayer dispersion of TPA even at a TPA loading of 60 wt%. These results present a broad potential of TPA/MCM-41 as an acid function in the catalyst mixture for the single-pass DME synthesis from CO2 hydrogenation, especially if used together with an MSC specifically designed for CO2 hydrogenation.
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    PublicationOpen Access
    Nanocrystalline cobalt-nickel-boron (metal boride) catalysts for efficient hydrogen production from the hydrolysis of sodium borohydride
    (Elsevier, 2021) N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Paksoy, Aybike; Altıntaş, Zerrin; Khoshsima, Sina; Öztulum, Samira Fatma Kurtoğlu; Dizaji, Azam Khodadadi; Uzun, Alper; Balcı, Özge; Researcher; Researcher; Faculty Member; Researcher; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; N/A; N/A; N/A; N/A; N/A; 59917; 295531
    Innovative metal boride nanocatalysts containing crystalline Co-Ni based binary/ternary boride phases were synthesized and used in the hydrolysis of NaBH4. All the as-prepared catalysts were in high-purity with average particle sizes ranging between similar to 51 and 94 nm and consisting of different crystalline phases (e.g. CoB, Co2B, Co5B16, NiB, Ni4B3, Ni2Co0-67B0.33). The synergetic effect of the different binary/ternary boride phases in the composite catalysts had a positive role on the catalytic performances thus, while the binary boride containing phases of unstable cobalt borides or single Ni4B3 were not showing any catalytic activity. The Co-Ni-B based catalyst containing crystalline phases of CoB-Ni4B3 exhibited the highest H-2 production rate (500.0 mL H-2 min(-1) g(cat)(-1)), with an apparent activation energy of 32.7 kJ/mol. The recyclability evaluations showed that the catalyst provides stability even after the 5th cycle. The results suggested that the composite structures demonstrate favorable catalytic properties compared to those of their single components and they can be used as alternative and stable catalysts for efficient hydrogen production from sodium borohydride.