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Esterlesme reaksiyonlarının dönüsümlerinin yavas bir reaksiyon hızıyla vetersinir reaksiyonların varlıgıyla sınırlı oldukları bilinmektedir. Reaksiyon hızınıarttırmak için katı asit katalizatörlerinin kullanımı homojen asit katalizatörlere göresahip oldukları avantajlar nedeniyle oldukça dikkat çekmektedir. Tasıyıcı iyon olarakkatalizatör iyonunu içeren iyon degistirici reçineler kullanılarak homojen katalizkabullenmesi yapılabilir. Çünkü reaksiyon mekanizması ve kinetik mertebe homojenkatalizinkiler seklinde belirlenmistir.Bu çalısmada, metil alkol ile asetik asit ve n-amil alkol ile propiyonik asitarasındaki esterlesmeler model reaksiyon olarak seçilmistir. Çalısmanın amacı, ikincimertebe homojen reaksiyona göre korele edilmis hız sabitlerine baglı olarak her birmodel reaksiyonu analiz etmede kullanılan volumetrik, kromatografik ve refraktometrikmetodların tekrarlanabilirlik sıralamasını belirlemektir. Ayrıca karıstırma hızı,katalizatör konsantrasyonu, tanecik büyüklügü, divinilbenzen içerigi, sıcaklık, mol oranıve farklı katalizatör gibi reaksiyon hızını etkileyen önemli degiskenler çalısılmıstır.Makro gözenekli (Ambelyst-15) ve mikro gözenekli (Dowex 50W, Amberlite IR-120)reçine katalizatörleri için aktivasyon enerjileri, reaksiyon entalpi ve entropi degerlerihesaplanmıstır.Bu yöntemlerin duyarlılık sıralaması söyle belirlenmistir: volumetrik >kromatografik > refraktometrik. Ayrıca kurutulduktan sonra katalizatör olarakkullanılan reçineler arasında Dowex 50Wx2' nin mikro gözenekli olmasına ragmen enetkili reçine oldugu bulunmustur.Anahtar Kelimeler: Esterlesme, kinetik, iyon degistirici reçineler, propiyonik asit, namilalkol, asetik asit, metil alkol. Conversions for the esterification reactions have long been known to be limitedby a slow reaction rate and the existence of reversible reactions. To accelerate thereaction rate, the use of solid acid catalysts has received great attention because ofhaving advantages compared to homogeneous acid catalysts. Homogeneous catalysiscan be accepted by using ion-exchange resins containing the catalyst ion as their counterions. Because the reaction mechanisms and kinetic orders have been determined asthose of homogeneous catalysis.In the present study the esterifications of acetic acid with methyl alcohol andpropionic acid with n-amyl alcohol were chosen as model reactions. The aim of thisstudy is to find that the reproducibility order of volumetric, chromatographic andrefractometric methods used in analysis of the each model reaction according to rateconstants correlated with a second-order homogeneous reaction. Furthermore, theimportant variables such as stirring speed, catalyst concentration, particle size,divinylbenzene content, temperature, mole ratio, different catalysts affecting the rate ofthe reaction were studied. The apparent activation energies, reaction enthalpies andentropy values were calculated for macroporous (Amberlyst-15) and microporous resin(Dowex 50W, Amberlite IR-120) catalysts.The sensitivity order of these methods was determined as follows: volumetric>chromatographic > refractometric. In addition that Dowex 50Wx2 was found the mosteffective one among the resins used as catalysts after being dried, although it is amicroporous resin.Key Words: Esterification, kinetic, ion exchange resins, propionic acid, n-amylalcohol, acetic acid, methyl alcohol. 167

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. Removal of water-soluble and/or insoluble pollutants is very important since water pollution resulted from industrial organic waste water drains and oil spills seriously harms human health and animal habitats. Multifunctional magnetic mesoporous nanocomposites are promising materials for the removal of water-soluble and/or insoluble pollutants due to the remarkable properties such as changeable surface properties, multiple binding sites, high surface area and magnetic separation. In this study, for that purpose, multifunctional magnetic nanocomposites Fe3O4@PDA@SBA-15@VTES and SBA-15-Fe3O4-PDA-ODA were designed by using mesoporous silica SBA-15 as matrix, magnetite (Fe3O4) providing magnetic separation as reinforcement, polydopamine (PDA) providing multiple bonding sites as functionalization element, and vinyltriethoxysilane (VTES) and octadecylamine (ODA) providing hydrophobicity as a modifier. The adsorption capacity of SBA-15-Fe3O4-PDA nanocomposite was determined as 138.08 mg g-1, while the adsorption capacity of Fe3O4@PDA@SBA-15 nanocomposite was determined as 71.92 mg g-1 for the removal of water-soluble cationic dye Malachite Green (MG) before surface modification. After VTES and ODA modification, for removal of oil which is a water-insoluble pollutant, the capacity of SBA-15-Fe3O4-PDA-ODA nanocomposite was determined 40.28 times of its own weight, while the capacity of Fe3O4@PDA@SBA-15@VTES nanocomposite was determined 8.83 times of its own weight. The magnetic nanocomposites could be easily separated from the water with an external magnet after the adsorption process and reused 3 times with simple regeneration processes, and no significant decrease was observed in their removal capacities. Moreover, SBA-15-Fe3O4-PDA-ODA from nanocomposites characterized by structural, magnetic and surface properties also exhibited successful adsorption properties in removal of water-soluble MG and water-insoluble oil pollutants in the same process. The prepared multifunctional magnetic mesoporous nanocomposites increase the functionality of the environmental cleaning process for water-soluble and insoluble pollutants, due to an easy and low cost production, selectively controllable removal ability of cationic dye and oil. YÖK 100/2000 Bursu

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. In this study, firstly superparamagnetic Fe3O4 nanoparticles were prepared by co-precipitation method. Secondly, these nanoparticles were covered with silica (SiO2) layer to protect them from oxidation by air and to prepare them ready for further functionalization. Finally, the amino groups were covalently grafted to the silica coated superparamagnetic Fe3O4 nanoparticles by using aminopropyl triethoxysilane (APTES) through silanization reaction. After being characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy/Energy Dispersed X-Ray (SEM/EDX), Vibrational Sample Magnetometer (VSM), Zeta Potential and Fourier Transform Infra-Red Spectroscopy (FT-IR) techniques, the resultant material, Fe3O4@SiO2@NH2, was used 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 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. Adsorption was more 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 calculated for LG and BY at 30 0C and natural pH of the solution were 40,2 and 35,5mg/g, respectively. Thermodynamic calculations demonstrated that the adsorption process was spontaneous and exothermic. Fe3O4@SiO2@NH2 also showed good removal efficiency for both dyes at least over three cycles. Bursalı Tekstil San. ve Tic. A.Ş

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. In this study, firstly superparamagnetic Fe3O4 nanoparticles were prepared by co-precipitation method. Secondly, these nanoparticles were covered with silica (SiO2) layer to protect them from oxidation by air and to prepare them ready for further functionalization. Finally, the amino groups were covalently grafted to the silica coated superparamagnetic Fe3O4 nanoparticles by using aminopropyl triethoxysilane (APTES) through silanization reaction. After being characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy/Energy Dispersed X-Ray (SEM/EDX), Vibrational Sample Magnetometer (VSM), Zeta Potential and Fourier Transform Infra-Red Spectroscopy (FT-IR) techniques, the resultant material, Fe3O4@SiO2@NH2, was used 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 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. Adsorption was more 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 calculated for LG and BY at 30 0C and natural pH of the solution were 40,2 and 35,5mg/g, respectively. Thermodynamic calculations demonstrated that the adsorption process was spontaneous and exothermic. Fe3O4@SiO2@NH2 also showed good removal efficiency for both dyes at least over three cycles. 106

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. Due to the increasingly stringent environmental conditions and economic factors, great interest has also been shown in the use of solid acid catalysts due to their efficient separation, reduction of waste and simple purification of the products. Solid acid catalysts can be easily separated from the reaction medium by conventional separation techniques such as centrifugation and filtration, and provide an economic and environmental advantage as far as they are reusable. In this work, it was aimed to prepare a new solid acid catalyst by adding suitable organoalkoxysilanes to obtain solid acid catalysts with SBA-15 sulfonic acid functional groups prepared by boron addition. Thus, it is envisaged that the solid acid catalyst will increase selectivity and activity in catalytic applications as it is expected to have high stability and a large number of strong protonic acid sites. Mesoporosity and the amorphous character of the samples and the presence of boron have been proven by means of characterization techniques such as XRD, N2-adsorpstion/desorption, FT-IR, SEM ve ICP/OES. The catalysts were observed to be effective in terms of catalytic activity and reusability in the esterification of propionic acid-methanol selected as a model reaction. Furthermore, they also exhibit greater selectivity in the esterification of long chain fatty acids with methanol such as palmitic acid-methanol and oleic acid-methanol due to their large pore diameters. Thus, new and versatile catalysts have been gained to the literature.

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.

3rd International Conference on Computational and Experimental Science and Engineering (ICCESEN) -- OCT 19-24, 2016 -- Antalya, TURKEY, WOS: 000412881200098, 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., Commission of Scientific Research Projects of Uludag University [OUAP(F)-2015/21, KUAP(F)-2014/33], This work was supported by The Commission of Scientific Research Projects of Uludag University, Project number: OUAP(F)-2015/21 and KUAP(F)-2014/33.

3rd International Conference on Computational and Experimental Science and Engineering (ICCESEN) -- OCT 19-24, 2016 -- Antalya, TURKEY, WOS: 000413982900062, SBA-15-SO3H supported tungstophosphoric acid (TPA, H3PW12O40) mesoporous materials were synthesized by impregnation of TPA into the hydrothermally synthesized SBA-15-SO3H and the catalytic performances were compared for the esterification reaction. The physical and chemical properties of the catalysts were characterized by XRD, SEM/EDX, FT-IR and N-2 adsorption/desorption techniques. The characterization results show that TPA/SBA-15-SO3H retained the typical mesoporous structure of SBA-15-SO3H. The experimental results indicated that TPA/SBA-15-SO3H is a more efficient catalyst than SBA-15-O3H for the esterification reaction. The higher activity of TPA/SBA-15-SO3H compared with that of SBA-15-SO3H was consistent with the material having the low pKa value, confirming that the esterification rate was mostly dependent on the acid strength of the additional functional groups of solid acid catalyst. Accordingly, the reason for the catalytic activity difference was simply explicated by the effect of TPA, having low pKa value, affecting the pore structure and the total acidity.

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 santrifrüj ve filtrasyon gibi geleneksel ayırma teknikleriyle kolayca reaksiyon ortamından ayrılabilirler ve tekrar kullanımları mümkün olduğundan ekonomik ve çevre açısından bir avantaj daha sağlamaktadırlar. Bu amaçla bor katarak hazırladığımız SBA-15' lere sülfonik asit fonksiyonel gruplarına sahip katı asit katalizörlerini elde etmek üzere uygun organoalkoksisilanlar eklenerek yeni bir katı asit katalizörünün hazırlanması amaçlanmaktadır. Böylelikle katı asit katalizör, yüksek kararlılık ve çok sayıda kuvvetli protonik asit bölgelerine sahip olacağından katalitik uygulamalarda seçimlilik ve aktiviteyi arttıracaktır. Sentezlenen katı asit katalizörleri FTIR, BET/BJH, SEM ve XRD metotlarıyla karakterize Due to the increasingly stringent environmental conditions and economic factors, great interest has also been shown in the use of solid acid catalysts due to their efficient separation, reduction of waste and simple purification of the products. Solid acid catalysts can be easily separated from the reaction medium by conventional separation techniques such as centrifugation and filtration, and provide an economic and environmental advantage as far as they are reusable. For this purpose, it is aimed to prepare a new solid acid catalyst by adding suitable organoalkoxysilanes to obtain solid acid catalysts having sulfonic acid functional groups of SBA-15 which we prepared by boron addition. Thus, the solid acid catalyst will increase selectivity and activity in catalytic applications since it will have high stability and a large number of strong protonic acid sites. The synthesized solid acid catalysts were characterized by FTIR, BET / BJH, SEM and XRD methods and were tested in the esterification reaction as catalyst. 88

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.

Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly(EGDMA-VTAZ-SO 3 H), is evaluated in the esterification of lactic acid with methanol. From nitrogen physisorption data, high surface area (220 m 2 /g) and type IV isotherm are obtained. Conversion measurements indicate a stronger interaction of poly(EGDMA-VTAZ-20%SO 3 H) with water molecules than that occurring in poly(EGDMA-VTAZ-10%SO 3 H). Hence, the higher catalytic activity of poly(EGDMA-VTAZ-10%SO 3 H) is related to the more hydrophobic microenvironment of –SO 3 H sites, which reduces the acid site deactivation associated with adsorption of water generated during the reaction. Moreover, apparent activation energy is found to be 48.02 kJ mol −1 , which can be comparable with the literature values.

WOS: 000301320500021, PubMed ID: 22197058, Mesoporous silica SBA-15 has been synthesized and functionalized by one-step synthesis method to widen their various application possibilities. In this study, phenyltrimethoxysilane (PTMS), 3-mercapto-propyltrimethoxysilane (MPTMS) and trimethoxypropylsilane (TMPS) were used as silane precursors for the functionalization, and after treated with HCl solution, their catalytic activities were evaluated in the lactic acid-methanol esterification. The presence of anchoring of functional groups on SBA-15 was proved by XRD, FT-IR, BET surface area and pore size distributions. Good catalytic activity was observed especially for SBA-15-SO3H-MPTMS, and the catalytic activity order was determined as follows: SBA-15SO(3)H-MPTMS > SBA-15-TMPS > SBA-15-PTMS, which is directly associated with the surface area, pore size and pore volume. As compared with homogeneous catalyst, SBA-15-SO3H-MPTMS heterogeneous catalyst shows remarkable performance, such as separation, recovery and reusability

Sulfonic acid functionalized poly (ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly (EGDMA–VTAZ–SO3H) (average diameter 1.0–1.5 mm), was found to be efficient solid acid catalyst for the esterification of methanol and propionic acid under heterogeneous reaction conditions. The pristine polymer, poly (EGDMA–VTAZ), was produced by suspension polymerization and then proton-conducting polymer was obtained by blending of poly (EGDMA–VTAZ) with different percentage of H2SO4 solutions. The protonation of aromatic heterocyclic rings was proved with Fourier-transform infrared spectroscopy (FT-IR). Thermo gravimetric (TG) analysis showed that the catalyst is thermally stable up to 573 K. The surface morphology of the catalyst was characterized by scanning electron microscopy (SEM). Poly (EGDMA–VTAZ–SO3H) beads can be regenerated and reused, so this provides a potential application. It has a rate constant which exceeds that of Amberlyst-15 by a factor of about four at 333 K. As for the reaction equilibrium constant (Ke), which is independent of temperature ranging from 318 to 343 K, was determined to be 3.16. The apparent activation energy was found to be 41.6 kJ mol−1 for poly (EGDMA–VTAZ–SO3H).

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 (k1) 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 k1/kCH3= 1.0061 Es- 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.

Summary Esterification of methyl alcohol with acetic acid catalysed by commercially available polymeric ion-exchange resins Amberlyst-15, Dowex 50W and Amberlite IR-120 was carried out in the temperature ranging between 323–338K. Mesh sizes and divinylbenzene contents had virtually no effect on the rate the data of which were correlated with a second-order homogeneous reaction. The samples were analysed with gas chromatography, refractometry and volumetry. The reproducibilities were the order of ±2.89%, ±5.07% and the order of ±6.58% respectively for the volumetric, chromatographic and refractometric methods.