Azeotrop metilal/metanol karışımlarının pervaporasyon prosesi ile saflaştırılması
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2022
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info:eu-repo/semantics/openAccess
Özet
Dimetoksimetan olarak da bilinen metilal (CH3-O-CH2-O-CH3), endüstride "yeşil" bir çözücü olarak kabul edilmektedir. Polimerler, reçineler, yapıştırıcılar, dizel yakıt katkı maddeleri ve böcek ilaçları gibi çeşitli uygulamalarda kullanılan önemli bir ara maddedir. Metilal genellikle metanol ve formaldehitin katalitik reaksiyonuyla sentezlenir. Sentez sırasında metilal ve metanol, minimum kaynama noktasına sahip azeotropik bir karışım oluşturur. Azeotropik karışımlar basit damıtma ile ayrılamaz. Bu karışımları ayırmak için kullanılan geleneksel yöntemler genellikle çok maliyetli, enerji yoğun işlemlerdir ve ek kimyasallar gerektirir. Bu noktada pervaporasyon işlemi önemli bir alternatiftir. Pervaporasyon, düşük enerji tüketimi, kolay kullanımı, düşük maliyeti ve yüksek seçiciliği nedeniyle son zamanlarda büyük ilgi görmektedir. Bu tez çalışmasında, azeotropik metilal/metanol karışımlarının hibrit membranlardaki etkisi incelenmiştir. Bu amaçla laboratuvarda 1,2-bis (trietoksisilil) etan (BTEE) katkılı PVA/PVP hibrit membranlar ve ZnO nanopartikül katkılı CA/PVP ve ZnO nanopartikül katkılı CA/PVA hibrit membranları sentezlenmiştir. Sentezlenen membranlar taramalı elektron mikroskobu (SEM), fourier dönüşümlü kızılötesi spektroskopisi (FTIR), termogravimetrik analiz (TGA) ve temas açısı testleri ile karakterize edilmiş ve membranların şişme davranışları incelenmiştir. Pervaporasyon ile ayırma işlemi sonucunda elde edilen geçen akım gaz kromotografisi cihazı kullanılarak analiz edilmiştir. Metilal/metanol karışımlarının pervaporasyon ile ayırma performansına üç farklı parametrenin etkisi incelenmiştir. Bunlar, polimerik membrana eklenen BTEE katkı oranı, beslemedeki metanol oranı ve uygulama sıcaklığının etkisidir. Çalışma sonucunda, membran içerisine eklenen BTEE katkısının artması akıyı artırmıştır ve katkısız blend membrana kıyasla BTEE eklenmesiyle seçicilik sonsuz değerde elde edilmiştir. Bu da toplam akı değerlerinin metanol akımına eşit olduğunu gösterir. Sıcaklığın artması ise akıyı artırmış ancak seçiciliği azaltmıştır. BTEE katkılı PVA/PVP hibrit membranlarında en yüksek akı değerleri 30 C sıcaklık ve %50 metanol içeren beslemede 1,444 kg/m2h olarak bulunmuştur ancak bu değerde seçicilik azalmıştır. Sentezlenen ZnO katkılı hibrit membranlarda ise PVP'nin varlığından oluşan membranın kırılganlığı pervaporasyon deneylerinin uygulanmasına engel olmuştur. Bu nedenle ZnO katkılı CA/PVA hibrit membranlar sentezlenerek membranların ayırma performansı incelenmiştir. %2 ZnO katkılı CA/PVA hibrit membranda akı değerinin 0,109 kg/m2h olduğu bulunmuş ve geçen toplam akının da metanol olduğu tespit edilmiştir.
Methylal (CH3-O-CH2-O-CH3), also known as dimethoxymethane, is accepted as a "green" solvent in the industry. It is an important intermediate used in various applications such as polymers, resins, adhesives, diesel fuel additives, and insecticides. Methylal is usually synthesized by the catalytic reaction of methanol and formaldehyde. During synthesis, methylal and methanol form an azeotropic mixture with a minimum boiling point. Azeotropic mixtures cannot be separated by simple distillation. Conventional methods, which are used to separate these mixtures, are generally very costly, energy-intensive processes and require additional chemicals. At this point, the pervaporation process is an important alternative. Recently, pervaporation has attracted great attention due to its low energy consumption, easy usage, low cost, and high selectivity. In this thesis, the effect of azeotropic methylal/methanol mixtures on hybrid membranes was investigated. For this purpose, 1,2-bis(triethoxysilyl) ethane (BTEE) doped PVA/PVP hybrid membranes and ZnO nanoparticle doped CA/PVP and ZnO nanoparticle doped CA/PVA hybrid membranes were synthesized in the laboratory. The synthesized membranes were characterized by SEM, FT-IR, TGA and contact angle tests, and membrane swelling activities were investigated. Gas chromatography was used to analyze the flux obtained as a result of pervaporation. Three different parameters were examined to examine the separation performance of methylal/methanol mixtures by pervaporation process. These are the BTEE additive ratio added to the polymeric membrane, the methanol ratio in the feed and the effect of the application temperature. As a result of the study, the increase of BTEE additive added into the membrane increased the flux and the selectivity is infinite with the addition of BTEE compared to the blend membrane. This shows that the total flux values are equal to the passing methanol flux. Increasing the temperature increased the flux but decreased the selectivity. In BTEE doped PVA/PVP hybrid membranes, the highest flux values were found as 1.444 kg/m2h in the feed containing 50% methanol at 30 °C, but the selectivity at this value decreased. The fragility of the membrane due to the presence of PVP in the synthesized ZnO doped hybrid membranes prevented the pervaporation experiments from being performed. Therefore, the separation performance of the membranes was investigated by synthesizing ZnO doped CA/PVA hybrid membranes. The flux value in the 2% ZnO doped CA/PVA hybrid membrane was found to be 0.109 kg/m2h and the total flux passing through was determined to be methanol.
Methylal (CH3-O-CH2-O-CH3), also known as dimethoxymethane, is accepted as a "green" solvent in the industry. It is an important intermediate used in various applications such as polymers, resins, adhesives, diesel fuel additives, and insecticides. Methylal is usually synthesized by the catalytic reaction of methanol and formaldehyde. During synthesis, methylal and methanol form an azeotropic mixture with a minimum boiling point. Azeotropic mixtures cannot be separated by simple distillation. Conventional methods, which are used to separate these mixtures, are generally very costly, energy-intensive processes and require additional chemicals. At this point, the pervaporation process is an important alternative. Recently, pervaporation has attracted great attention due to its low energy consumption, easy usage, low cost, and high selectivity. In this thesis, the effect of azeotropic methylal/methanol mixtures on hybrid membranes was investigated. For this purpose, 1,2-bis(triethoxysilyl) ethane (BTEE) doped PVA/PVP hybrid membranes and ZnO nanoparticle doped CA/PVP and ZnO nanoparticle doped CA/PVA hybrid membranes were synthesized in the laboratory. The synthesized membranes were characterized by SEM, FT-IR, TGA and contact angle tests, and membrane swelling activities were investigated. Gas chromatography was used to analyze the flux obtained as a result of pervaporation. Three different parameters were examined to examine the separation performance of methylal/methanol mixtures by pervaporation process. These are the BTEE additive ratio added to the polymeric membrane, the methanol ratio in the feed and the effect of the application temperature. As a result of the study, the increase of BTEE additive added into the membrane increased the flux and the selectivity is infinite with the addition of BTEE compared to the blend membrane. This shows that the total flux values are equal to the passing methanol flux. Increasing the temperature increased the flux but decreased the selectivity. In BTEE doped PVA/PVP hybrid membranes, the highest flux values were found as 1.444 kg/m2h in the feed containing 50% methanol at 30 °C, but the selectivity at this value decreased. The fragility of the membrane due to the presence of PVP in the synthesized ZnO doped hybrid membranes prevented the pervaporation experiments from being performed. Therefore, the separation performance of the membranes was investigated by synthesizing ZnO doped CA/PVA hybrid membranes. The flux value in the 2% ZnO doped CA/PVA hybrid membrane was found to be 0.109 kg/m2h and the total flux passing through was determined to be methanol.
