Browsing by Author "Erdem, Beyhan"

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Adsorption of light green and brilliant yellow anionic dyes using amino functionalized magnetic silica (Fe 3 O 4 @SiO 2 @NH 2) nanocomposite
(Taylor, 2019-01-01) Erdem, Beyhan; Avşar, Saliha Buşra; Erdem, Sezer; Tekin, Nalan; ERDEM, BEYHAN; Avşar, Saliha Buşra; ERDEM, SEZER; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; AAI-1238-2021; AAI-1248-2021; CDX-3142-2022
Fe3O4@SiO2@NH2 nanocomposite was prepared for highly effective adsorption of two anionic dyes one of which is triarylmethane dye (light green, LG) and the other is azo dye (brilliant yellow, BY). The characterization results demonstrated that superparamagnetic Fe3O4 nanoparticles were covered with silica and functionalized with amino groups successfully without losing magnetic character. The effects of adsorbent dosage, contact time, pH, temperature, and dye molecular structure on the adsorption were investigated. Acidic pH was better for both LG and BY, on the other hand, alkaline pH was favorable to some extent for LG in comparison with BY due to the contribution of stacking effect in addition to electrostatic attraction. Kinetic data demonstrated that the driving force for adsorption process could be explained by pseudo-second order mechanism in both systems. The equilibrium data were more compatible with Langmuir isotherm than those of Freundlich isotherm and the maximum adsorption capacities of Fe3O4@SiO2@NH2 calculated from Langmuir isotherm model for LG and BY at 30 degrees C and natural pH of the solution were 40.2 and 35.5 mg g(-1). Thermodynamic calculations related to temperature dependence demonstrated that the adsorption process was spontaneous and exothermic.
B-SBA-15-SO3H: A versatile mesoporous catalyst
(Springer, 2017) Erdem, Beyhan; Azko, Çağla; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; AAI-1238-2021; 14023997200; 57193125976
Novel approach was developed towards the synthesis of heterogeneous mesoporous B-SBA-15-SO3H acid catalysts. That is: B-SBA-15 materials were hydrothermally synthesized by using three different boron sources (boric acid, trisiopropylborate and potassium borohydride) and then post-synthetically functionalized with sulfonic acid to test their catalytic activity for the esterification of propionic acid with methanol. Mesoporous and amorphous character of the materials as well as the incorporation of the boron into the framework were verified by XRD, N-2-adsorption/desorption, ICP-OES, SEM and FT-IR techniques. All of the boron incorporated acid catalysts showed better activity than pure SBA-15-SO3H for methyl propionate synthesis. Combining the advantageous of hydrothermal synthesis and post functionalization, the obtained B-SBA-15-SO3H catalysts should present versatile catalytic properties in terms of both catalytic activity and reusability. Boron incorporation and post functionalization encourage the structural configuration, since the grafted catalytically active groups may experience similar environments and be isolated from each other.
Bifunctional Fe-SBA-15-SO3H mesoporous catalysts with different Si/Fe molar ratios: Synthesis, characterization and catalytic activity
(Wiley-V C H Verlag, 2013-05) Öksüzoglu, Ramis Mustafa; Çıtak, Alime; Erdem, Sezer; Erdem, Beyhan; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Anabilim Dalı.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Anabilim Dalı.; AAI-1238-2021; AAI-1248-2021; 13805689400; 14023997200
Bifunctional Fe-SBA-15-SO3H mesoporous materials with different Si/Fe molar ratios (3, 5, and 7) have been synthesized via a simple direct hydrothermal method and characterized by XRD, N-2-adsorption/desorption, TG/DTG and FT-IR techniques, and used as solid acid catalysts in the esterification of lactic acid with methanol. XRD and N-2 sorption characterizations show successful iron doping within the mesoporous channels of SBA-15-SO3H. The FT-IR and TG/DTG characterizations also reveal the presence of iron. With the incorporation of Fe ions into the SBA-15-SO3H, the acid sites substantially increased because of the self-separated acidity of the hydrolysis of Fe3+ solutions. However, in the Si/Fe = 3 molar ratio, the catalytic conversion decreased which is caused by the reduced cooperation effect between the acid pairs due to the weakened hydrogen bonds and collapse of the pore structure. This further suggests that the mesoporous structure decreases with the decrease in Si/Fe ratio.
Bor katkılı mezogözenekli fonksiyonelleştirilmiş sba-15 sentezi, karakterizasyonu ve katalitik uygulamaları
(Uludağ Üniversitesi, 2017-07-13) Tüfekçi, Çağla Azko; Erdem, Beyhan; Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/Kimya Anabilim Dalı.
Artan sıkı çevre şartları ve ekonomik faktörler nedeniyle ayrıca etkin ayrılma, atıkların azalması ve ürünlerin basitçe saflaştırılması gibi özelliklerinden dolayı katı asit katalizörlerinin kullanımına büyük ilgi gösterilmektedir. Katı asit katalizörleri santrifüj ve filtrasyon gibi geleneksel ayırma teknikleriyle kolayca reaksiyon ortamından ayrılabilirler ve tekrar kullanımları mümkün olduğundan ekonomik ve çevre açısından bir avantaj daha sağlamaktadırlar. Bu çalışmada bor katarak hazırlanan SBA-15’ lere sülfonik asit fonksiyonel gruplarına sahip katı asit katalizörlerini elde etmek üzere uygun organoalkoksisilanlar eklenerek yeni bir katı asit katalizörünün hazırlanması amaçlanmıştır. Böylelikle katı asit katalizörün, yüksek kararlılık ve çok sayıda kuvvetli proton asit bölgelerine sahip olacağı beklendiğinden katalitik uygulamalarda seçimlilik ve aktiviteyi arttıracağı öngörülmüştür. Numunelerin mezogözenekliliği, amorf karakteri ve borun yapıdaki varlığı XRD, N2-adsorpsiyon/desorpsiyon, FT-IR, SEM ve ICP/OES gibi karakterizasyon yöntemleriyle ispatlanmıştır. Katalizörlerin model reaksiyon olarak seçilen propiyonik asit-metanol esterleşmesinde katalitik aktivite ve tekrar kullanılabilirlik açısından etkili olduğu gözlenmiştir. Ayrıca büyük gözenek çapları nedeniyle palmitik asit-metanol ve oleik asit-metanol gibi uzun zincirli yağ asitlerinin esterleşmesinde daha fazla seçimlik sergilemiştir. Böylece literatüre yeni ve çok yönlü katalizörler kazandırılmıştır.
Catalytic applications of large pore sulfonic acid-functionalized SBA-15 mesoporous silica for esterification
(De Gruyter Poland, 2018-01) Öksüzoğlu, Ramis Mustafa; Erdem, Beyhan; Erdem, Sezer; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-1803-9400; 0000-0003-1119-9863; AAI-1238-2021; AAI-1248-2021; 14023997200; 13805689400
We report the preparation of pore expanded and sulfonic acid functionalized mesoporous silica catalysts by using different kinds of swelling agents such as 1,3,5-trimethyl benzene (TMB), n-decane (D), n-tridecane (TD), and n-hexadecane (HD) at two different ratios of swelling agent/surfactant. Non-swelled mesoporous silica catalyst, SBA-15-SO3H, was also prepared for comparison. The performance of the sulfonic acid functionalized solid acid catalysts by using one-pot synthesis procedure was evaluated in terms of their catalytic activity in the esterification of propionic acid with methanol. The catalysts have been characterized by X-ray diffraction to investigate the phase transition between the hexagonally packed arrangement of cylindrical pores and mesocellular silica foams (MCF), and N-2 adsorption/desorption technique in terms of pore size and distributions. It was concluded from the XRD and N-2 adsorption/desorption analyses that hexagonally packed and cylindrical pore structure is maintained only for low ratio of swelling agent/surfactant and the increase of the dimension of a template micelle is accompanied by an increase in structural disruption, which was attributed to the phase transition from highly ordered hexagonal arrangement to mesocellular foam (MCF) phase with large nodded pore structures rather than cylindrical pores. Among the different swelling agents, TMB and D were found to be effective for the increase in pore diameter (up to 8 and 7.8 nm), whereas, TD and HD (6.6 nm) are effective to maintain the ordered X-ray diffraction patterns resulting mesoporous materials without giving enlargement of pore diameter in comparison with TMB and D. Pore expanded catalysts, SBA-15-SO3H-TMB-0.1 and SBA-15-SO3H-D-0.1, exhibit 68 and 43% enhancement in turnover frequency toward propionic acid methanol esterification, respectively, over non :swelled SBA-15-SO3H, despite possessing similar acid strengths. The increased activity especially for SBA-15-SO3H-TM B-0.1 and SBA-15-SO3H-D-0.1 likely reflects the accessibility to the active sulfonic acid sites as well as acidity.
Cationic surfactant templated synthesis of magnetic mesoporous nanocomposites for efficient removal of Light Green
(Korean Institute Chemical Engineers, 2021-06-22) Erdem, Beyhan; Erdem, Sezer; Tekin, Nalan; ERDEM, BEYHAN; ERDEM, SEZER; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü; AAI-1238-2021; AAI-1248-2021
Fe3O4-SiO2-NH2, Fe3O4-CTABSiO(2)-NH2 and Fe3O4-SiO2-CTABSiO(2)-NH2 magnetic adsorbents were successfully prepared and could be used effectively for the adsorption of Light Green from aqueous solutions. Unlike the first sample, mesoporous silica coatings were created using cetyltrimethylammoniumbromide micelles as molecular templates on superparamagnetic iron oxide in one sample, and on silica-coated iron oxide in the other sample to improve the adsorptive properties of the nanocomposites. The characterization by FT-IR, SEM/EDX, Zeta-potential, XRD, VSM, and N-2-adsorption/desorption confirmed the production of mesoporous silica layer. Although coating processes with both silica and mesoporous silica layers led to a vaguely decrease in saturation magnetization of the Fe3O4-SiO2-CTABSiO(2)-NH2, the nanoparticles were protected with silica coatings for environment conditions and made more suitable for subsequent amino functionalization. The results determined from Batch adsorption experiments fitted to Langmuir isotherm model with maximum adsorption capacity (q(max)) equal to 56.18, 196.08 and 227.27 mg g(-1), for Fe3O4-SiO2-NH2, Fe3O4-CTABSiO(2)-NH2 and Fe3O4-SiO2-CTABSiO(2)-NH2, respectively, and it was seen from the kinetic results, the LG adsorption was identified by pseudo-second-order kinetics, revealing that LG adsorption process is homogeneous, monolayer and based on chemical interactions. According to the results, both silica and mesoporous silica coating strategy can play crucial role in improving the adsorptive properties of nanocomposites.
Comparative influence of adsorption assisted magnetic mesoporous TiO2 photocatalyst for the removal of methylene blue and rhodamine B
(Springer, 2023-04-01) Öksüzoğlu, Ramis Mustafa; Erdem, Beyhan; ERDEM, SEZER; ERDEM, BEYHAN; Erdem, Sezer; Sevinç, Samet; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Kimya Bölümü.; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0574-5170; ABB-3036-2021
In this study, magnetically separable Fe3O4-SiO2-mesoTiO(2) nanocomposite has been synthesized for photodegradation of Methylene Blue (MB) and Rhodamine B (RhB) cationic dyes which have complex aromatic structures and are difficult to degrade into harmless products. By XRD analysis, it was determined that the magnetite phase of Fe3O4 was protected after coating with SiO2 interlayer and mesoTiO(2) shell, and the anatase phase of TiO2 was formed. According to the N-2-adsorption/desorption and VSM results, Fe3O4-SiO2-mesoTiO(2) nanocomposite has a surface area of 197.8 m(2)/g, pore volume of 0.34 cm(3)/g and a pore size of 3.4 nm and has 3.8 emu/g saturation magnetization and negligible remnant magnetization and coercivity, which indicates its mesoporous and superparamagnetic character. The adsorption ability of RhB (16.86%) is lower than MB (23.32%), nevertheless, the photodegradation activity of RhB (99.06%) is higher than that of MB (97.52%). Photodegradation kinetics follows the pseudo-first order and the rate constants of photocatalytic reactions were calculated as 0.0422 and 0.0719 min(-1) for MB and RhB, respectively. While the lower adsorption feature of RhB was resulted from steric hindrance, the higher photodegradation rate was explained by more radical scavenging effect. MB prefers to face the photocatalyst surface, whereas RhB prefers to focus on the aqueous phase, and based on scavenge results, RhB is more likely to encounter photoactive species (H2O2, h(+) and center dot O-2(-)) than that of MB with center dot O-2(-) being the dominant active species. The synthesized Fe3O4-SiO2-mesoTiO(2) photocatalyst could be reused three times with negligible photocatalytic loss in the photodegradation of both dyes.
Determination of steric effect on the esterification of different alcohols with propanoic acid over cation-exchange resin catalyst Dowex 50Wx4
(Walter De Gruyter Gmbh, 2011) Erdem, Beyhan; Cebe, Mustafa; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Anabilim Dalı.; AAI-1238-2021; 14023997200; 6506210722
This paper describes the application of LFER in the form of Taft correlation to understand the mechanism of the esterification of propanoic acid with different alcohols over heterogeneous catalyst, Dowex 50Wx4. The rate constant (k(1)) in the rate equation decreases with change of alcohols in the order methanol, ethanol, n-propyl, n-butyl, n-pentyl, iso-butyl, iso-propyl and sec-butyl (2-buthanol). The reaction of propanoic acid with alcohols fits the Taft equation, log k(1)/k(CH3) = 1.0061 E-s - 0.0012, which implies that the steric effect of the substituent governs that reaction and the mechanism is similar between the different alcohols. The experimental results were modelled according to a simple second-order model. It was found that the equilibrium constant of this reaction does not depend on the structure of the organic alcohols, and has for 333 K the value 4.04.
Direct and postsynthetic functionalization of mesoporous B-SBA-15-SO3H acid catalyst and application to methyl propionate esterification
(Polish Acad Sciences Inst Physics, 2017) Öksüzoğlu, R. M.; Erdem, Beyhan; Azko, Q.; Erdem, Sezer; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAI-1238-2021; AAI-1248-2021; 14023997200; 57196450981; 13805689400
Organic functionality can be added to mesoporous silicates in two ways: either by covalent grafting (postsynthetic) of various functional groups onto the channel walls or by incorporating functionalities directly during the synthesis (one-pot). If the grafted catalytically active groups experience similar environments and are isolated from each other, catalysis process is greatly facilitated. For this purpose, boric acid, as boron source, was added into the initial reaction mixture and then acid functionalization was performed by post and direct method. The obtained acid catalysts were tested in the esterification of propionic acid with methanol and the activity of these new materials was compared to that of SBA-15-SO3H. Boron addition has facilitated the methyl propionate esterification for both postsynthetic and direct functionalized acid catalyst. Boron incorporated and postsynthetic functionalized mesoporous acid catalyst has highly enhanced the esterification reaction, compared to direct functionalized acid catalyst. The post functionalization method seems to be superior to one-pot functionalization method for preparation of mesoporous acid catalysts.
Effect of calcination temperature on the structural and magnetic properties of Ni/SBA-15 nanocomposite
(Springer, 2015-06-01) Erdem, Sezer; Erdem, Beyhan; Öksüzoğlu, Ramis Mustafa; Çitak, Alime; ERDEM, SEZER; ERDEM, BEYHAN; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü; AAI-1238-2021; AAI-1248-2021
The effect of calcination temperature on the structural and magnetic properties of Ni/SBA-15 nanocomposite prepared by reductant-impregnation method was studied using SBA-15 mesoporous silica as support. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometry, N-2 adsorption/desorption (BET and BJH), vibrating sample magnetometer, and FT-IR. Characterization results showed the presence of crystalline phases characteristics of the Ni and/or NiO, and that the structural characteristics of the support were maintained after the impregnation of nickel ions followed by calcinations. Calcination process helps in crystallization and formation of the desired phase such as well crystalline NiO and Ni nano-particles. Moreover, this heat resulted in significant effects on different properties of the products such as the crystallite size, homogeneity, particle distribution, porosity, surface area and the sintering process. Magnetic measurements suggested that the magnetic properties in nanocomposites is probably the sum of two contributions: superparamagnetic and ferromagnetic one depending on the calcination temperature. Calcination at high temperatures affects both of the structural and magnetic properties of Ni/SBA-15. Because the location of the Ni particles depends on the pore size of the support, the uniformity of particle size was related to the interaction between the Ni particles and support.
Esterleşme reaksiyon mekanizmalarında kinetik, katalitik ve termodinamik parametrelerin deneysel yöntemlerle izlenmesi ve irdelenmesi
(Uludağ Üniversitesi, 2007-07-04) Erdem, Beyhan; Cebe, Mustafa; Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/Kimya Anabilim Dalı.
Esterleşme reaksiyonlarının dönüşümlerinin yavaş bir reaksiyon hızıyla ve tersinir reaksiyonların varlığıyla sınırlı oldukları bilinmektedir. Reaksiyon hızını arttırmak için katı asit katalizatörlerinin kullanımı homojen asit katalizatörlere göre sahip oldukları avantajlar nedeniyle oldukça dikkat çekmektedir. Taşıyıcı iyon olarak katalizatör iyonunu içeren iyon değiştirici reçineler kullanılarak homojen kataliz kabullenmesi yapılabilir. Çünkü reaksiyon mekanizması ve kinetik mertebe homojen katalizinkiler şeklinde belirlenmiştir. Bu çalışmada, metil alkol ile asetik asit ve n-amil alkol ile propiyonik asit arasındaki esterleşmeler model reaksiyon olarak seçilmiştir. Çalışmanın amacı, ikinci mertebe homojen reaksiyona göre korele edilmiş hız sabitlerine bağlı olarak her bir model reaksiyonu analiz etmede kullanılan volumetrik, kromatografik ve refraktometrik metodların tekrarlanabilirlik sıralamasını belirlemektir. Ayrıca karıştırma hızı, katalizatör konsantrasyonu, tanecik büyüklüğü, divinilbenzen içeriği, sıcaklık, mol oranı ve farklı katalizatör gibi reaksiyon hızını etkileyen önemli değişkenler çalışılmıştır. Makro gözenekli (Ambelyst-15) ve mikro gözenekli (Dowex 50W, Amberlite IR-120) reçine katalizatörleri için aktivasyon enerjileri, reaksiyon entalpi ve entropi değerleri hesaplanmıştır. Bu yöntemlerin duyarlılık sıralaması şöyle belirlenmiştir: volumetrik > kromatografik > refraktometrik. Ayrıca kurutulduktan sonra katalizatör olarak kullanılan reçineler arasında Dowex 50Wx2’ nin mikro gözenekli olmasına rağmen en etkili reçine olduğu bulunmuştur.
Fonksiyonelleştirilmiş manyetik nanopartiküllerin sentezi ve boyar madde adsorpsiyonunda kullanılması
(Bursa Uludağ Üniversitesi, 2019-10-18) Karakelle, Saliha Büşra Avşar; Erdem, Beyhan; Bursa Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/Kimya Anabilim Dalı.; 0000-0001-9471-4634
Bu çalışmada, ilk olarak birlikte çöktürme yöntemiyle süperparamanyetik Fe3O4 nanopartikülleri hazırlanmıştır. İkinci olarak bu nanopartiküller havayla oksitlenmeyi önlemek ve ileri fonksiyonelleştirmeye hazır hale getirmek için silika (SiO2) ile kaplanmıştır. Son olarak, amino grupları silanizasyon reaksiyonu aracılığıyla aminopropil trietoksisilan (APTES) kullanarak silika kaplı Fe3O4 nanopartiküllerine kovalent olarak aşılanmıştır. Sonuç malzeme, Fe3O4@SiO2@NH2, X-Işını Kırınımı (XRD), Geçirimli Elektron Mikroskobu (TEM), Taramalı Elektron Mikroskobu/Enerji Dağılımlı X-Işını Spektroskopisi (SEM/EDX), Zeta Potansiyeli ve Fourier Transformu Kırmızı Ötesi Spektroskopisi (FT-IR) teknikleriyle karakterize edildikten sonra biri triarilmetan boya (Light Green, LG) diğeri azo boya (Brilliant Yellow, BY) olan iki anyonik boyanın etkin adsorpsiyonunda kullanılmıştır. Adsorban dozu, temas süresi, pH, sıcaklık ve boyaların moleküler yapılarının adsorpsiyon üzerindeki etkileri araştırılmıştır. Asidik pH hem LG hem de BY için daha uygundur. Adsorpsiyon, BY ile karşılaştırıldığında elektrostatik çekime ilaveten birikme etkileri nedeniyle LG ile bir dereceye kadar daha iyidir. Her iki sistemde de kinetik veriler adsorpsiyon sürecinde yürütücü kuvvetin yalancı ikinci mertebe ile açıklanabileceğini göstermiştir. Denge verileri Langmuir izotermi ile Freundlich izotermine göre daha uyumludur ve 30 oC' de, doğal çözelti pH' larında LG ve BY için hesaplanan maksimum adsorpsiyon kapasiteleri sırasıyla 40,2 ve 35,5 mg/g olarak belirlenmiştir. Termodinamik hesaplamalar adsorpsiyon prosesinin kendiliğinden ve ekzotermik olduğunu göstermiştir. Ayrıca Fe3O4@SiO2@NH2, her iki boya için en az üç döngüde iyi bir giderim etkinliği göstermiştir.
Heterogeneous catalysed esterification of propionic acid with n-amyl alcohol over a microporous cation-exchange resin dowex 50wx4
(Walter De Gruyter GMBH, 2010) İzci, Alime; Erdem, Beyhan; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; AAI-1238-2021; 14023997200
Kinetics of heterogeneous catalysed esterification of propionic acid with n-amyl alcohol was studied with a microporous cation-exchange resin catalyst. Dowex 50Wx4, in a stirred batch reactor to synthesise amyl propionate. Effects of various parameters such as speed of agitation, catalyst loading, and reaction temperature on reaction rate were investigated. The equilibrium conversion of propionic acid increased with in catalyst loading and reaction temperature. Stirrer speed had virtually no effect on the reaction rate under the experimental conditions. The apparent activation energy was found to be 43.167 kJmol(-1) for the formation of amyl propionate and the equilibrium constant, which is independent of temperature ranging from 318 to 348 K. was found to be 4.05. It was also observed that the initial reaction rate decreased with water concentrations and increased with that of acid and increased with that of alcohol linearly. The reaction was found to occur between an adsorbed acid molecule and a molecule of alcohol in the bulk and it was concluded that the reaction mechanism can be represented by Eley-Rideal model.
High-surface-area SBA-15-SO3H with enhanced catalytic activity by the addition of poly(ethylene glycol)
(Springer, 2013-10) Öksüzoğlu, Ramis Mustafa; Çıtak, Alime; Erdem, Beyhan; Erdem, Sezer; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Anabilim Dalı.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Anabilim Dalı.; AAI-1248-2021; AAI-1238-2021; 14023997200; 13805689400
The influence of poly(ethylene glycol) (PEG) and synthesis temperature in the synthesis of SBA-15-SO3H was investigated to evaluate the catalytic activity in the esterification of propionic acid with methanol. The catalysts were characterized by means of surface and structure analyses; X-ray diffraction, FT-IR, scanning electron microscopy, Thermo-gravimetric and N-2 adsorption/desorption techniques. It was found that, by the addition of PEG, the surface area and porosity of SBA-15-SO3H increased, while the structure and size of mesopores remained unchanged. Nitrogen sorption measurements indicate that PEG introduces additional pores into the pore walls of SBA-15-SO3H. Thus, a simple way of improving the porosity of mesoporous SBA-15-SO3H was presented that could enhance transport of substrates through the porous system and allow the generation of stable mesoporous replicas, important for catalytic applications and also beneficial for replication and nanocasting purposes.
Kinetics of esterification of propionic acid with n-amyl alcohol in the presence of cation exchange resins
(Korean Institute Chemical Engineers, 2006) Erdem, Beyhan; Cebe, Mustafa; Uludağ Üniversitesi/Fen Edebiyet Fakültesi/Kimya Bölümü.; AAI-1238-2021; 14023997200; 6506210722
Esterifications of n-amyl alcohol with propionic acid catalyzed by macroporous (Amberlyst-15) and microporous (Dowex 50 W and Amberlite IR-120) polymeric ion-ex6hange resins were carried out between 333-348 K. When these catalysts were used as commercially available, Amberlyst-15 was observed to be the most effective catalyst with respect to rate constants, but after drying it became the less effective one. The reaction rate increased with increase in catalyst concentration and reaction temperature. Stirrer speed and different mesh sizes had virtually no effect on the rate under the experimental conditions. The effect of divinylbenzene content was examined for the micro porous resin Dowex 50 W, and the results showed that the propionic acid conversion decreased as the divinylbenzene content was increased. The rate data were correlated with a second-order homogeneous reaction model. The apparent activation energies, reaction enthalpies and entropy values were calculated for each catalyst. Reaction monitoring is simple and fast by volumetric method and the reproducibility of this method was the order of +/- %2.54.
Magnetic mesoporous silica nanocomposite for biodiesel production
(Polish Acad Sciences Inst Physics, 2017-09) Öksüzoğlu, R. M.; Erdem, Sezer; Avşar, Saliha Büşra; Erdem, Beyhan; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; AAI-1248-2021; AAI-1238-2021; 13805689400; 57196458837; 14023997200
Ordered mesoporous silicas can be utilized as support because of having large surface area, tunable porosity, uniform pore size distribution, high thermal stability and modifiable properties. However, these materials introduce separation problems in liquid-phase processes. We have prepared Fe3O4-SBA-15-SO3H solid acid catalyst by combining the properties of a magnetic material and the mesoporous character of silica. The sulfonic acid functionalized solid acid catalyst, containing both magnetic nanoparticles and mesoporous silica, is not only separable but also stable under hydrothermal conditions, which are usually employed for biodiesel production. Esterification of oleic acid with methanol for biodiesel production was carried out effectively and 75% conversion of ester was approximately reached within six hours in the presence of Fe3O4-SBA-15-SO3H magnetic solid acid catalyst. In addition, the catalyst could be separated from the reaction system by applying external magnetic field and reused without deactivation.
Magnetic nano-sized solid acid catalyst bearing sulfonic acid groups for biodiesel synthesis
(De Gruyter Poland Sp Z. O. O., 2018-05-04) Öksüzoǧlu, Ramis Mustafa; Erdem, Sezer; Erdem, Beyhan; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; AAI-1238-2021; AAI-1248-2021; 13805689400; 14023997200
In our approach for magnetic iron oxide nanoparticles surface modification, the fabrication of an inorganic shell, consisting of silica by the deposition of preformed colloids onto the nanoparticle surface and functionalization of these particles, was realized. The magnetic nanoparticles, non-coated and coated with silica layer by Stober method, are functionalized with chlorosulfonic acid. The magnetic nanoparticles (MNPs), in size of 10-13 nm, could be used as acid catalyst in biodiesel production and show superparamagnetic character. The prepared nanoparticles were characterized by different methods including XRD, EDX, FT-IR and VSM. The catalytic activity of the coated and non-coated solid acids was examined in palmitic acid-methanol esterification as an industrial reaction for biodiesel synthesis. Although thin silica layer results in only a minor obstacle with respect to magnetism, it can accelerate the mass transportation due to its relatively porous structure and magnetic core may be more stable in the acidic reaction medium by means of covering process. Accordingly, coating strategy can be efficient way for allowing applications of MNPs in acid catalyzed esterification.
Manyetik mezogözenekli çok işlevli nanokompozit sentezi, karakterizasyonu ve uygulamaları
(Bursa Uludağ Üniversitesi, 2022-05-31) İşcan, Kübra Bilgin; Erdem, Beyhan; Bursa Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/Kimya Anabilim Dalı.; 0000-0001-6765-8227
Endüstriyel organik atık su drenajlarından ve petrol sızıntılarından kaynaklanan su kirliliği insan sağlığına ve hayvanların yaşam alanlarına ciddi şekilde zarar verdiğinden, suda çözünür ve/veya çözünmeyen kirleticilerin uzaklaştırılması çok önemlidir. Çok işlevli manyetik mezogözenekli nanokompozitler, çoklu bağlanma bölgeleri, yüksek yüzey alanı, manyetik ayırma ve yüzeyin modifiye edilebilmesi gibi dikkate değer özellikleri nedeniyle suda çözünen ve/veya çözünmeyen kirleticilerin uzaklaştırılması için umut vadeden malzemelerdir. Çalışmada, bu amaca yönelik, matris olarak mezogözenekli silika SBA-15, takviye elemanı olarak manyetik ayırmayı sağlayan manyetit (Fe3O4), fonksiyonelleştirme elemanı olarak çoklu bağlanma yerleri sağlayan polidopamin (PDA) ve modifiye edici olarak hidrofobiklik kazandıran viniltrietoksisilan (VTES) ve oktadesilamin (ODA) kullanılarak çok işlevli manyetik mezogözenekli nanokompozitler tasarlanmıştır: Fe3O4@PDA@SBA-15 ve SBA-15-Fe3O4-PDA-ODA. Yüzey modifikasyonundan önce suda çözünür katyonik boyar madde Malachite Green (MG) gideriminde Fe3O4@PDA@SBA-15 nanokompozitinin adsorpsiyon kapasitesi 71,92 mg g-1 olarak belirlenirken, SBA-15-Fe3O4-PDA nanokompozitinin adsorpsiyon kapasitesi 138,08 mg g-1 değerinde bulunmuştur. VTES ve ODA modifikasyonundan sonra suda çözünmeyen kirletici olan yağ gideriminde, Fe3O4@PDA@SBA-15@VTES nanokompozitinin kapasitesi 8,83 g g-1 olarak belirlenirken, SBA-15-Fe3O4-PDA-ODA nanokompozitinin kapasitesi 40,28 g g-1 değerindedir. Manyetik nanokompozitler adsorpsiyon işleminden sonra, bir mıknatıs ile sudan kolayca ayrılıp basit rejenerasyon prosesleri ile 3 kez tekrar kullanılabilmiş ve giderim kapasitlerinde belirgin bir düşme gözlenmemiştir. Üstelik yapısal, manyetik ve yüzey özellikleri karakterize edilen nanokompozitlerden SBA-15-Fe3O4-PDA-ODA suda çözünen MG ve çözünmeyen yağ kirleticilerin aynı süreçte giderilmesinde de başarılı adsorpsiyon özelliği sergilemiştir. Hazırlanan çok işlevli manyetik mezogözenekli nanokompozitler, kolay ve düşük maaliyetli üretim prosedürü, kaytonik boya ve yağın seçici olarak kontrol edilebilir uzaklaştırma yeteneği sayesinde suda çözünen ve çözünmeyen kirleticiler için çevre temizleme sürecinin işlevselliğini arttırmaktadır.
Manyetik mezogözenekli TiO2 fotokatalizörlerinin hazırlanması ve uygulama alanları
(Bursa Uludağ Üniversitesi, 2022-09-01) Sevinç, Samet; Erdem, Beyhan; Bursa Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/Kimya Anabilim Dalı.; 0000-0002-1754-4720
Organik boyarmaddelerin neden olduğu su kirliliği insan sağlığı ve doğal çevreyi tehdit eden ciddi bir problem olmuştur. Metilen Mavisi (MM) ve Rodamin B (RB) gibi sıklıkla kullanılan katyonik boyalar, kompleks aromatik yapıya sahiptirler ve zararsız ürünlere parçalanmaları oldukça zordur. Bu çalışmada, MM ve RB boyaları için iyi bir fotokatalitik bozunma performansı gösteren ve manyetik olarak ayrılabilen Fe3O4-SiO2-mezoTiO2 nanokompoziti hazırlanmıştır. Bu amaçla, ilk olarak birlikte çöktürme yöntemi kullanılarak süperparamanyetik Fe3O4 nanoparçacıkları sentezlenmiştir. İkinci olarak bu Fe3O4 nanoparçacıklarının hava ile oksitlenmesini ve TiO2’nin fotokatalitik performansının azalmasını önlemek için Fe3O4 nanoparçacıklarının etrafında Stöber yöntemiyle bazik ortamda SiO2 ara katmanı oluşturulmuştur. Son olarak silika kaplı nanoparçacıklar yüzey aktif madde şablonu kullanılarak sol-jel sentez yöntemiyle mezogözenekli TiO2 tabakası ile kaplanmıştır. Elde edilen Fe3O4, Fe3O4-SiO2 ve Fe3O4-SiO2-mezoTiO2 örnekleri, X-Işını Kırınımı (XRD), Taramalı Elektron Mikroskobu (SEM), Titreşimli Örnek Manyetometresi (VSM), Fourier Transformu Kırmızı Ötesi Spektroskopisi (FT-IR), N2-adsorpsiyon/desorpsiyon teknikleriyle yapısal, morfolojik ve manyetik özellikleri açısından karakterize edilmiştir. Oda sıcaklığında, UV ışıması altında (368 nm), doğal çözelti pH'larında, 50 mg fotokatalizör ilavesi ile MM ve RB organik boyarmaddeleri 120 dk süre sonunda sırasıyla % 97,52 ve % 99,06 fotobozunmaya uğramıştır. Her iki boya için de reaksiyon hız sabitleri belirlenmiş ve yalancı birinci dereceden hız eşitliğine uyduğunu gösteren iyi bir doğrusallık sergilemiştir. Fotokatalizörün reaksiyon mekanizması bir dizi radikal tutucu etkisi incelenerek MM ve RB organik boyarmaddeleri için açıklanmıştır. Ayrıca, mıknatısla ayrılabilen ve geri kazanılabilen manyetik mezogözenekli TiO2 fotokatalizörü, fotokatalitik aktivite kaybı olmaksızın üç kez tekrar kullanılabilmiştir.
Multifunctional magnetic mesoporous nanocomposites towards multiple applications in dye and oil adsorption
(Springer, 2021-04-09) Erdem, Beyhan; İşcan, Kübra Bilgin; ERDEM, BEYHAN; İşcan, Kübra Bilgin; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü; 0000-0001-6765-8227; AAI-1238-2021; FDK-4016-2022
Multifunctional magnetic mesoporous nanocomposites are promising materials to remove the various pollutants from water due to the remarkable properties such as multiple binding sites, high surface area, and magnetic separation. Herein, we have developed a versatile nanocomposite, in which polydopamine (PDA) coated Fe3O4 nanoparticles are introduced during the synthesis of SBA-15 matrix for the first time to enhance adsorptive properties of hydrophilic magnetic mesoporous nanocomposite by combining the properties of high surface area, magnetization, and capability of interacting with more functional groups in one material. The resulting nanocomposite, Fe3O4@PDA@SBA-15, has been proved to be the effective sorbent for the removal of cationic dye, which can be ascribed to the functional groups of grafted PDA and the textural features of matrix SBA-15. On the other hand, after chemical modification via silanization of vinyltriethoxysilane (VTES), Fe3O4@PDA@SBA-15 nanocomposite turned to be a hydrophobic material, Fe3O4@PDA@SBA-15@VTES, which can adsorb oil with high adsorption capacity which could reach 8.83 times of its own weight. Moreover, both nanocomposites could be recycled by facile washing and drying processes. The materials provide a simple strategy for the preparation of multifunctional magnetic mesoporous nanocomposites satisfying various applications in water treatment.