HTCC/NA2SIO3 Composite Catalytic Membrane And Integrated Process For Biodiesel Preparation

Biodiesel,as a green,safe,renewable fuels,is considered the best alternative to petrochemical diesel.In this paper,sodium silicate(Na2SiO3)and N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan(HTCC)were used as catalytically active materials,and supported by polypropylene nonwoven fabric.A novel composite catalytic membrane HTCC/Na2Si03/NWF was prepared by non-solvent phase inversion and used as a heterogeneous catalyst for continuous transesterification reaction of soybean oil to biodiesel in membrane reactor.The kinetic model of continuous transesterification reaction was established.The low-cost acidified oil was catalyzed to biodiesel by combination alkaline catalytic membrane HTCC/Na2SiO3/NWF with acid catalytic membrane SPSF/PES/NWF.The adsorption of trace fatty acids in biodiesel was investigated with magnesium silicate as the adsorbent.The results are as follows:During transesterification of soybean oil with methanol in membrane reactor filled with HTCC/Na2SiO3/NWF,the conversion of soybean oil to biodiesel is up to 97%and the conversion of soybean oil is maintained over 94.0%in the continuous mode for over 40 h under the optimal conditions of alcohol/oil molar ratio of 9:1,reaction temperature of 60 ?,membrane area of 36.3 cm2,membrane pore volume of 6.52 cm3,residence time 3913 s.The reaction kinetics model of the composite membrane HTCC/Na2SiO3/NWF continuous transesterification of soybean oil to biodiesel was established.The results of kinetic experiments showed that when the volume flow rate was higher than 1.0 ml.min-1,the external diffusion resistance was ignore.The activation energy of the composite membrane HTCC/Na2SiO3/NWF transesterification reaction of soybean oil and methanol was 68,93 kJ/mol,and the pre-exponential factor was 5.58 X 107 min-1.The composite membrane HTCC/Na2SiO3/NWF catalyzed transesterification reaction in the flow-through mode is controlled by reaction kinetics.Biodiesel was continuously prepared from acidic oil and methanol using acid catalyzed membrane SPSF/PES/NWF and base catalyzed membrane HTCC/Na2SiO3/NWF.The acid value was reduced from 100 mg.KOH/g.oil to 0.96 mg.KOH/g.oil,and the conversion of FFA was kept above 98%,which had a good stability and high efficiency.The content of water/FFA was 3%and 1.5%respectively,the conversion of soybean oil to biodiesel was still above 90%,indicating that the base catalyzed membrane HTCC/Na2SiO3/NWF had better tolerance to water/FFA.In the integrated process,the conversion rate of FFA was 99.0%,the conversion of triglyceride was 93.6%and the yield of methyl ester was 97.23%.It is difficult to meet the standard of biodiesel because of trace fatty acids after esterification reaction.In this study,magnesium silicate with good adsorption performance was selected for the adsorption of fatty acids.Under the optimal reaction conditions:the mass of oleic acid methyl ester was 30 g(3.74 mg.KOH/g),the reaction temperature was 50 ?,magnesium silicate/FFA molar ratio 1:1,reaction time was 1 h.The adsorption capacity of the adsorbent was 176.23 mg/g,and after ten times of adsorption reaction,the adsorption capacity was up to 162.48 mg/g,the adsorption capacity of the adsorbent was reduced by 7.8%.The adsorbent after the reaction was regenerated by calcination method.