Tham khảo tài liệu 'biodiesel feedstocks and processing technologies part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Biodiesel Production with Solid Catalysts 349 The esterification reaction path is slightly different in various acidic species types. The whole reaction process is through proton-exchange. Tesser et al. 2005 proposed a kinetic model based on the following hypotheses 1 major part of the active sites are occupied by methanol in a protonated form and the rest part are also occupied 2 fatty acid water and methyl ester reach proton-exchange equilibrium with the protonated methanol 3 inside the resin particles an Eley-Rideal mechanism occurs between protonated fatty acid and the methanol. Deviate from the mechanism shown in Fig. 3 steps of protonation of carbonyl carbon nucleophilic attack proton migration and breakdown of intermediate are undergoing in a proton-exchange way. Transesterification mechanism The transesterification reaction involves catalytic reaction between triglyceride and alcohol . methanol ethanol propanol and butanol to form biodiesel FAMEs and glycerol Fig. 4 . In the reaction three consecutive reactions are required to complete the transesterification of a triglyceride molecule. In the presence of acid or base a triglyceride molecule reacts with an alcohol molecule to produce a diglyceride and FAME. Then a diglyceride reacts with alcohol to form a monoglyceride and FAME. Finally an monoglyceride reacts with alcohol to form FAME and glycerol. Diglyceride and monoglyceride are the intermediates in this process. R1COOCH2 HOCH2 R2COOCH ROH Catalys- R2COoCh R1COOR r3cooCh2 r3cooCh2 fame Triglyceride Diglyceride HO 2 HOC I2 R2COOCH ROH CatalysL HoCh R2COOR r3cooCh2 r3cooCh2 fame Diglyceride Monoglyceride HOCH2 HoCh R3C00CH2 RH_ HOCH2 hoCh R3COOR H0CH2 fame Monoglyceride glycerol Fig. 4. Transesterification reactions of glycosides with alcohol. Mechanism for heterogeneous acid-catalyzed transesterification Acidic or basic functional groups in the active sites of solid catalysts catalyze the reaction by donating or accepting protons. .
