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Hintyağı sekonder esterinin oluşumunun ve parçalanmasının incelenmesi

Esterification of castor oil with oleic acid and splitting of castor oil secondary ester

  1. Tez No: 14403
  2. Yazar: LEVENT DANDİK
  3. Danışmanlar: DOÇ.DR. A. TUNCER ERCİYES
  4. Tez Türü: Yüksek Lisans
  5. Konular: Kimya Mühendisliği, Chemical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1991
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 36

Özet

ÖZET Bu çalışmada hintyağının oleik asit ile verdiği esterleşme re aksiyonu ve oluşan sekonder esterin i sı sal parçalanma reaksiyonu re aksiyon kinetiği açısından incelenmiştir. Her iki reaksiyon farklı şartlarda yürütülerek hız ifadelerinin belirlenmesine çalışılmıştır. Esterleşme reaksiyonu 20000, 225°C ve 250°C de katalizör varlığında ve katalizörsüz olarak yürütülmüştür. Kalay klorür katalizörü var- 9" ? -den reaksiyon kinetiğine uymaktadır. Diğer taraftan sekonder este rin ısısal parçalanma reaksiyonu 26Û°C, 270°C ve 280°C de katalizör varlığında ve katalizörsüz olarak gerçekleştirilmiştir. Parçalanma reaksiyonunda çinko oksit, p-toluensülfonik asit ve sülfirik asit katalizör olarak kullanılmıştır. Isısal parçalanma reaksiyonları uygulanan her koşulda birinci mertebe reaksiyon kinetiğine uymakta dır. Yapılan bu kinetik çalışmalardan sonra parçalanma ürününden çıkarak kuruyan yağ sentezi yapılmıştır. iv

Özet (Çeviri)

ESTERIFICATION OF CASTOR OIL WITH OLEIC ACID AND SPLITTING OF CASTOR OIL SECONDARY ESTER SUMMARY In this study, esterification of castor oil with oleic acid and the thermal decomposition of the resulting ester product was inves tigated in view of reaction kinetics. For the determination of rate equations, both reactions were carried out under different conditions. Esterification process was conducted at 200°C, 225°C and 250°C with and without catalyst. Catalysts used in the first reaction were po tassium hydroxide, p-toluenesulfonic acid and tin chloride (SnCİ2- 2H2O). On the other hand pyrolysis of castor oil ester was also performed under different conditions. In this case, the reaction temperatures wera260°C, 270°C, 280°C and the splitting catalysts were zinc oxide, p-toluenesulfonic acid and sulfuric acid. In addition, the pyrolysis mixture was evaluated in the preparation of a drying oil. Before going into detail, it would be better to give a brief information at this point on the structure and the industrially im portance of castor oil. Castor oil consists largely of glycerides of ricinoleic acid (12-hydroxy octadecenoic acid). The presence of hydroxyl group in addition to an olefinic linkage in this predominating fatty acid provides castor oil many reaction possibilities. The diagram given below shows the fundamental structure of castor oil and its functions in these reactions. Among these reactions, esterification occupies very important place in the manufacture of industrially useful materials. For in stance, in the manufacture of non-drying alkyd resin, castor oil is esterified with phthalic anhydride. Additionaly, secondary esters of castor oil formed with drying oil fatty acids were also studied in order to obtain a material with drying oil properties. Another reaction which finds technical applications is the splitting (pyroly sis) of secondary ricinoleyl ester linkages. In connection with this, fatty acid esters of castor oil, as well as acetylated castor oil, were reported earlier as the starting material in the manufac ture of dehydrated castor oil. It is well known that dehydrated castor oil can be prepared by one of the following three methods: 1- Catalytic method which utilized directly castor oil Dehydration of estolides formed by esterification of castor oil fatty acids by themselves. 3- Dehydration of castor oil second ry esters,In the catalytic method, castor oil is heated under a vacuum at a temperature in the range of 230-250°C in the presence of a catalyst until water is no longer evolved. Solubility charecteris- tics change during dehydration. The starting castor oil is soluble in methanol and insoluble in petroleum ether; as dehydration prog resses the product becomes insoluble in alcohol and soluble in hydrocarbon solvents. CASTOH OIL WW 928 5 CHEMICAL REACTIONS OF CASTOR OIL In the second method, dehydration of castor oil can be accomp lished by combination of esterification and pyrolysis of the ester. In the original Scheiber process, which is no longer used commer cially, castor fatty acids were prepared by saponification of the whole oil and after acidification the isolated acids were heated under esterification conditions. Polyesters, termed estolides, are formed by the condensation reaction between the carboxyl group of one molecule of ricinoleic acid and the hydroxyl group of anot her. With continued heating the initial polyester prolyzes to form dehydrated castor fatty acids containing approximately 50% conjugated dienoic acids. Finaly the dehydrated castor acids are reesterified with glycerol (on another polyol if desired). The extensive processing involving the steps of fat splitting, esteri- fication-dehydration, and reesterification makes Scheiber process dehydrated castor oil uneconomic. VIThe third method for dehydration utilizes the original Schetber concept and features complete esteri fi cation of the hydroxyl groups with a stochiometric amount of a suitable organic acid to form an essentially neutral ester, followed by an increase in temperature to pyrolyze the ester and form dehydrated castor oil and regenerate the added organic acid. Pyrolysis occurs in the temperature range 250-300°C, and when castor oil is heated with substantially less than the stochiometric quantity of acid, esterification and pyrolysis occur simultaneously to yield the dehydrated oil. Acids used in the chemical dehydration method include acetic acid, 18-carbon fatty acids including ricinoleic acid, phthalic anhydride, and rosin. In all these works esterification of castor oil with fatty acids and pyrolysis of resulting ester product were not studied in respect of reaction kinetics. However closely related to the esterification of castor oil with fatty acids is the condensation reaction between ricinoleic acid molecules, the product being estolides. In the ki netic study, this reaction was found to be second order. Additio- na^y» pyrolysis of the estolides was found previously to be first order reaction. In the present study esterification of castor oil with oleic acid and the pyrolysis of castor oil ester thus formed was investi gated in respect of reaction kinetics. Esterification reaction followed third order kinetics in all cases with the exception of tin chloride catalyzed reaction. The reactions using tin Chloride as catalyst followed second order kine tics. In the Table 1, rate constant and the activation energy for each case were given. Pyrolysis reactions were found to be first order in all cases. Rate constants and activation energy was given in following table!..In the last stage of the study pyrolysis mixture was evaluated in the preperation of a synthetic oil with dying oil properties. In the drying tests on this synthetic oil satisfactory result were obtained. vnTable 1 Rate constants and activation energies for the esterification of castor oil with oleic acid under different conditions. *The units of rate constants for tin chloride-catalyzed reactions are (wt.per.)" (min)~ Table 2 Rate constants and activation energies for the thermal de composition of castor oil secondry ester under difffent conditions. Conjugated dienoic acid contents of the pyrolysis mixture were determined by U.V. absorption method. The results are calculated in Table 3. As can be seen the catalysts used in the reaction were not superior to one another in their effect on the formation of conjuga tion. In the drying time determination tests conducted with different dryer amount the results given in Table 4 were obtained. vmTable 3 Dienoic Acid Contents of the Pyrolysis Mixture Konjugated Dienoic Acid Catalyst. 26QOC 270°C280°C 16.19 15.42 16.58 18.15 IX

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