Researcher:
Bozkurt, Özge Deniz

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PhD Student

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Özge Deniz

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Bozkurt

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Bozkurt, Özge Deniz

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2015 - 20204

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    Alternative fuel additives from glycerol by etherification with isobutene: structure-performance relationships in solid catalysts
    (Elsevier, 2015) Tunç, F. Meliz; Bağlar, Nur; Çelebi, Serdar; Günbaş, I. Doğan; N/A; Department of Chemical and Biological Engineering; Bozkurt, Özge Deniz; Uzun, Alper; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of Engineering; N/A; 59917
    The expansion of biodiesel industry is expected to introduce over three million tons of glycerol into the market in 2020. Various routes have been proposed to produce glycerol-based value-added products to sustain renewable glycerol and biodiesel industries. One of these routes is the catalytic etherification of glycerol with isobutene for producing fuel oxygenate glycerol ethers as an alternative to today's petroleum based oxygenates. The products of the etherification of glycerol with isobutene are mono-, di-, and tri-tertiary butyl ethers of glycerol (MTBG, DTBG, and TTBG) and dimers of isobutene (DIE). Among these, DTBG and TTBG are the desired products for fuel blends because of their better blending properties. Different heterogeneous catalysts including acidic ion exchange resins (e.g. Amberlyst 15 and 36), sulfonated wide pore zeolites (e.g. zeolite Beta and Y), sulfonated mesoporous silica (e.g. MCM-41 and SBA-15) and some functionalized porous materials (e.g. sulfonated peanut shell, sulfonated aerogel, sulfonated graphene, spherical silica supported Hyflon) have been proved to demonstrate superior catalytic activity with complete glycerol conversion and over 90 mol% selectivity to the desired ethers. Here, we review the studies on glycerol etherification with isobutene from 1990s to the first half of 2015 specifically focusing on structure-performance relationships in heterogeneous catalysts. (C) 2015 Elsevier B.V. All rights reserved.
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    Screening of solid acid catalysts for etherification of glycerol with isobutene under identical conditions
    (Elsevier, 2020) Baglar, Nur; Celebi, Serdar; N/A; Department of Chemical and Biological Engineering; Bozkurt, Özge Deniz; Uzun, Alper; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 59917
    We compared the performance of more than 70 solid acid catalysts with Bronsted acid function for the etherification of glycerol with isobutene under identical reaction conditions of 75 degrees C, 10 bar, 6 h and with an isobutene/glycerol molar ratio of 3/1. The catalysts were selected from a wide range of solid acid catalysts including ion exchange resins, zeolites, silica, and heteropolyacids, and their counterparts modified by simple treatments, with more than half of them being investigated for the first time for this reaction. For the modified commercial acid catalysts, the desired glycerol tertiary butyl ether (DTBGE and TTBGE) selectivity improved from 75 to 87 wt% upon partial cation exchange of the sulfonic acid protons in AmberlystT type ion exchange resins with Na+ cations; from 66 to 85 wt% by hydrothermal steam treatment of zeolite H-Y (SiO2/Al2O3 = 80); and from 75 to 80 wt% with partial La+-exchange of zeolite H-Beta (SiO2/Al2O3 = 300), all at high (90-100%) glycerol conversion. Impregnation of the heteropolyacids, tungstosilicic acid (TSA) and tungstophosphoric acid (TPA), on silica at a loading of 50 wt% provided a glycerol conversion of higher than 65 wt% and with a desired ether selectivity in the range of 62 to 76 wt%. In general, total ether selectivity increased with decreasing acid capacity for ion exchange resins, while the desired ether selectivity was enhanced with increasing acid strength for zeolites and supported heteropolyacids on mesoporous silica. Data present a detailed guideline for the selection of solid acid catalysts for the etherification of glycerol with isobutene.
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    Assessment of acid strength in sodium-exchanged resin catalysts: consequences on glycerol etherification with isobutene in batch and flow reactors
    (Elsevier Science Bv, 2019) Department of Chemical and Biological Engineering; N/A; Uzun, Alper; Bozkurt, Özge Deniz; Faculty Member; PhD Student; 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); College of Engineering; Graduate School of Sciences and Engineering; 59917; N/A
    Consequences of a decrease in the number of acid sites by the cation exchange on the acid strength of the resin catalysts were assessed using ammonia as a probe molecule. IR spectra illustrated that v(N-H) bands on NH3-saturated Amberlyst 15 (TM) shift linearly to higher frequencies with an increase in the degree of sodium exchange associated with an increase in the Bronsted acid strength. These results were further confirmed by density functional theory calculations illustrating that the deprotonation energy of a sulfonated styrene group decreases upon Na+-exchange on its neighboring counterparts. Consequences of these changes in acid strength were investigated on glycerol etherification with isobutene. Batch reactor measurements at high conversions illustrated that selectivity to desired glycerol ethers increases as that of isobutene dimerization is suppressed with an increase in acid strength. The effects of acid strength on the complex reaction network were further investigated using a once-through flow reactor specifically focusing on low conversions. These measurements showed that mono-tert-butyl glycerol ether and di-isobutene were the primary products on pristine Amberlyst 15 (TM), while di-and tri-tert-butyl glycerol ethers also become a primary product on sodium-exchanged counterpart catalysts.
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    Compatibility of di- and tri-tert-butyl glycerol ethers with gasoline
    (Elsevier, 2019) Yılmaz, Fatih; Bağlar, Nur; Çelebi, Serdar; N/A; Department of Chemical and Biological Engineering; Bozkurt, Özge Deniz; Uzun, Alper; 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); Graduate School of Sciences and Engineering; College of Engineering; N/A; 59917
    Di- and tri-tert-butyl glycerol ethers (DTBGE and TTBGE) can be produced at high yields via etherification of glycerol with isobutene over cost effective and commercially available solid acid catalysts. These ethers have a potential to replace methyl-tert-butyl ether, an environmentally unfriendly gasoline oxygenate. In this study, we first synthesized fuel additive mixtures consisting of different concentrations of DTBGE and TTBGE and then determined the fuel characteristics of the fuel surrogates prepared by blending these mixtures with a reference gasoline fuel. Density, kinematic viscosity, and water solubility of the GTBE mixtures dropped with increasing TTBGE concentration, corresponding to a decrease in the number of hydroxyl groups in the ether mixtures. Blending 3.45 vol% GTBE in gasoline resulted in an increase in octane number from 95 to 96 and a decrease in vapor pressure from 57 to 55 kPa, whereas density and oxidation stability of the GTBE-gasoline blends remained within the fuel specifications. Results indicated that DTBGE alone is not compatible with gasoline, there is a need of TTBGE content in the fuel blends for better compatibility. We then compared the power and emissions by conducting fuel performance tests in an engine dynamometer using the reference gasoline, 3.45 vol% MTBE-blended gasoline, and 3.45 vol% GTBE-blended gasoline (34 wt% TTBGE, 62 wt% DTBGE, 1 wt% MTBGE, and 3 wt% isobutene oligomers). Our results illustrate that GTBE is an alternative gasoline additive to MTBE as their blends provide similar torque values, specific fuel consumption, and mean emissions of CO2, CO, NOx, and total hydrocarbon emissions (THC).