The Study On The Synthesis Of Ethyl Palmitate Catalyzed By Immobilized Lipase In Mesoporous Molecular Sieves SBA-15

Palmitic acid ethyl ester is widely used as an emulsifier, biological diesel oil andfood additives, mainly used in essence and spice. But the study of enzymatic synthesisof ethyl palmitate is little, the synthesis of ethyl palmitate researches mainly focus onchemical catalysis synthesis level by now. Our study made use of palmitic acid andethanol as the substrate, amino modified molecular sieve SBA-15as the carrier toimmobilize the pancreatic pig lipase. And we used this complex as a catalyst tosynthesize the esterification reaction. IR、UV spectra and other means were used todetect the conformation after the separation and purification of the product. We usedacid value method to calculate the yield of ethyl palmitate. The method of singlefactor experiment and response surface analysis was used to determine the optimumconditions for the synthesis of ethyl palmitate. This thesis mainly included thefollowing sections:Part one, the synthesis of amino-modified mesoporous SBA-15. We used thetriblock copolymer PEO20-PPO70-PEO20(P123) as template, TEOS as silica sourceunder acidic condition, SBA-15was synthesized by hydrothermal method andcalcined at550℃to remove the residues P123templating agent. SBA-15was aminomodified through the Toluene and APTES，this was the synthetic NH2-SBA-15.SBA-15and NH2-SBA-15were used to characterize the samples by XRD, N2adsorption desorption, FTIR, TEM, SEM,TGA-DTA and other methods. The resultsshowed that: NH2-SBA-15samples synthesized also has long-range orderedhexagonal pore structure, pore size range of it is approximately6-8nm.Part two, the synthesis of the immobilized enzyme. NH2-SBA-15was as acarrier to immobilize porcine pancreatic lipase by covalent crosslinking method.Making use of Bradford to determin the amount of immobilized enzyme and olive oilemulsification to determin the enzyme activity.The nature and stability of the free andimmobilized enzyme and immobilization conditions were explored and optimized.The results showed that the loading rate of immobilized enzyme was82.347%, the optimum temperature of immobilized enzyme was50℃, the optimum pH was7.5，the optimum Km was4.94%.The remaining activity also remained70%of initialactivity after repeated six times. The optimal conditions for the immobilized enzymeby covalent crosslinking method was that: crosslinking time is4h，enzyme dosage was360mg, buffer pH was7.5, temperature was25℃. The immobilized enzymesynthesized by crosslinking method had a high load capacity and better stability.Part three, the synthesis of ethyl palmitate. We used the immobilized enzyme ascatalyst, palmitic acid and ethanol as substrates to synthesize the ethyl palmitate.Invesigated the effects of reaction temperature, time and ethanol amount to the resultswith single factor experiment analysis. Response surface methodology was measuredthat the optimal conditions were as follows, temperature was55.94℃, time was6.72hours, ethanol amount was4.26ml, palmitic acid was1.5g, immobilized enzyme was0.1g and water was0.5ml.We synthesized the ethyl palmitate after using theoptimized process parameters, the average yield was about73.5%.We had successfully synthesized molecular sieve NH2-SBA-15which had alarger aperture.We used the molecular sieves as a carrier to immobilize the porcinepancreatic lipase which had good stability, so it was suitable for non-aqueous phasecatalysis. In this experiment, we used the palmitic acid and ethanol as substrates,immobilized enzyme as a catalyst. We synthesized a yield of about73.5%of ethylpalmitate through process optimization.