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Data Update

Data Update. ---------------Transesterification of triglyceride with methanol at different temperatures. Shuli Yan 20080205. Outline. Introduction Experiment Catalyst structure Effect of temperature on methyl esters formation Kinetics of soybean oil to methyl esters. Homogenous catalysis

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Data Update

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  1. Data Update ---------------Transesterification of triglyceride with methanol at different temperatures Shuli Yan 20080205

  2. Outline • Introduction • Experiment • Catalyst structure • Effect of temperature on methyl esters formation • Kinetics of soybean oil to methyl esters • Homogenous catalysis • Heterogeneous catalysis

  3. Introduction • Transesterification of vegetable oil with alcohol for biodiesel production • Homogeneous catalysis • Heterogeneous catalysis Strong acid or alkaline catalysts such as HCl, NaOH

  4. Introduction • Kinetics of transesterification catalyzed by homogenous catalysts • Dufek studied the kinetics of acid-catalyzed transesterication of 9(10)-carboxystearic acid and its mono- and di-methyl esters. • Freedman et al. firstly reported transesterication reaction of soybean oil and other vegetable oils with alcohols, and examined in their study were the effects of the type of alcohol, molar ratio, type and amount of catalyst and reaction temperature on rate constants and kinetic order. • Noureddin and Zhu studied the effects of mixing of soybean oil with methanol on its kinetics model of transesterication.

  5. Introduction • Kinetics of transesterification catalyzed by heterogonous catalysts very little information concerning the kinetics of heterogeneously catalytic transesterification • Our goal: • studying the use of the heterogeneously ZnxLayOz catalyzed transesterification reaction in batch stirred tank reactors for biodiesel production • developing a kinetic model based on a three step ‘Eley–Rideal’ type mechanism to simulate the transesetrification process.

  6. Experiments • Catalyst preparation and characterization • Homogeneous-coprecipitation method using urea as precipitant Prepare a mixture solution of Zn(NO3)2 , La(NO3)3 andurea Heat to 100 oC and hold for 6 hr Stirred with magnetic stirrer Filter/unfilter Dry at 150 oC for 8 hr Use step-rise calcination method at 250 (2hr), 300 (2hr), 350 (2hr), 400 (2hr), 450 oC (8hr), • SEM/EDS

  7. Experiments • Transesterification Molar ratio of methanol to soybean oil-----------------42:1 Catalyst dosage----------------------2.3 %(wt) Stir speed------------------------------490 rpm

  8. Catalyst structure • SEM/EDS

  9. Catalyst structure • SEM/EDS

  10. Catalyst structure • SEM/EDS

  11. Catalyst structure • SEM/EDS

  12. Effect of temperature on methyl esters formation Reaction conditions: ZnxLayOz, catalyst dosage is 2.3% (wt), Molar ratio of methanol to oil is 42:1, Stir speed is about 490 rpm Temperature was raised by step method. And when getting to the at target temperature point, it was hold for 1min Fig. 5 Methyl esters yield at different temperature

  13. Effect of temperature on methyl esters formation Reaction conditions: ZnxLayOz, catalyst dosage is 2.3% (wt), Molar ratio of methanol to oil is 42:1, stir speed is about 490 rpm. Fig. 6 Effect the temperature on the methyl esters formation

  14. Kinetic model • Assumptions: • The slurry batch reactor was perfectly mixed • Only methanol molecule adsorb on the surface of catalyst • Surface chemical reaction is the rate-determing step • pKa (Methanol: 15.54 Natural oil: 3.55 ) • Molecular size (Methanol: 0.33 nm Natural oil: 2 nm) • Heterolytically dissociate

  15. Fig. 7 Transesterification reaction Fig. 8 Methanol dissociates heterolytically on acid and base sites of ZnO surface. Kinetic model

  16. CA A AB CB B RDS khet fast QA Kinetic model • Eley-Rideal bimolecular surface reactions An adsorbed molecule may react directly with an impinging molecule by a collisional mechanism Fig. 9 Eley-Rideal mechanism

  17. （1） Kinetic model • Elementary reactions based on Eley-Rideal-type mechanism • Adsorption Where A is methanol molecule and S is an adsorption site on the surface Where is methanol molecule concentration on the surface of catalyst, bA is the adsorption coefficient, is the fraction of surface empty sites, CA is the concentration of methanol.

  18. （2） Kinetic model • Elementary reactions based on Eley-Rideal-type mechanism 2. Surface reaction Where B is tri-, di-, and mono-glyceride molecule, DS is an adsorpted di-, and mono-glyceride molecule on catalyst surface, Where k2 and k-2 is the reaction rate constants, Cc is the concentration of FAME

  19. （3） Kinetic model • Elementary reactions based on Eley-Rideal-type mechanism 3. Desorption Di-, mono-glyceride and glycerin desorbs from catalyst surface Where is di-, mono-glycerie and glycerine molecule concentration on the surface of catalyst, bD is the adsorption coefficient, CD is the concentration of di-, mono-glycerie and glycerine .

  20. （4） （5） Kinetic model According to steps 1 , 2 and 3, we can get Because of Then

  21. >> （6） （7） Kinetic model Where Because tri-, di- mono-glyceride and glycerin have low adsorption, Then

  22. （8） Kinetic model Because the final product glycerine will separate from reaction mixture, we assume that step 2 is unreversible. When methanol concentration is kept constant, （9） Where

  23. Kinetic model • The rate constant of transesterification reaction Table 1 the reaction rate constant of transesetrification

  24. Kinetic model • Arrhenius equation E = 16.4 KJ/mol Fig. 10 The temperature dependency of the reaction rate constants

  25. （1） （2） （3） （4） （5） Fig. 11 Mechanism of ZnO-catalyzed transesterification of triglyceride with methanol

  26. Conclusion • A multiporous catalyst • 170 oC • A kinetic model was developed based on a three-step E-R type of mechanism. • First order reaction as a function of the concentration of triglyceride • E = 16.37KJ/mol

  27. Future work Investigate the influence of some kinetic parameters on transesterification such as molar ratio of methanol to oil, catalyst amount

  28. Thank you!

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