Investigation On Energy Reuse Of Biodiesel Byproduct Glycerol

With the vigorous development of the biodiesel industry,more attention has been drawn to the utilization of biodiesel byproduct.There are a large amount of complex organic compounds in crude glycerol such as methanol,free fatty acid,glycerate,methyl ester and so on.The purification process must be carried on before transforming crude glycerol into high value-added chemicals for reusing.Because of the high cost of purification process,it is much crucial to develop new way to reuse the crude glycerol.Glycerol,a major biodiesel byproduct,is used as the substrate in enzyme biofuel cell.The organic substances is converted into clean energy,which is not just a complete and thorough treatment for the by-product,but also provides a clean and reliable energy reuse.This paper mainly studied the related application of glycerol in enzymatic fuel cell,including enzyme catalytic oxidation of glycerol at anode and oxygen reduction reaction at cathode in glycerol enzyme biofuel cell.First,we had prepared the CNTs/MBH/GDH/CS enzyme modified electrode,in which carbon nanotubes?CNTs?was catalyst carrier,the Glycerol Dehydrogenase?GDH?was enzyme catalysis and the Chitosan?CS?was binder.As was shown in our research,the redox reaction of Meldola's Blue?MBH?on the electrode surface was an adsorption control process,the reaction?2e+H⁺?was a quasi-reversible reaction in neutral conditions,and MBH could effectively oxidize NADH after oxidized on the surface of the electrode to MB⁺,reducing the oxidation over potential of NADH.Using electrochemical methods,the catalytic reaction on the electrode surface of CNTs/GDH/MBH/CS was validated.After the optimization of this enzyme modified electrode,the maximum catalytic current density was 17.86?A/cm²,in which CNTs is 5.0 mg/mL,GDH is 7.5 mg/mL,and MBH is 1.0 mM in the mixture.Then,we had prepared the CNTs/GK/GPO/CS two-enzyme modified electrode,in which carbon nanotubes?CNTs?was catalyst carrier,the Glycerokinase?GK?and Glycerol-3-Phosphate Oxidase?GPO?were enzymes catalysis,the Chitosan?CS?was binder and specially the Ferrocenylmethanol?Fm?in solution was electron transfer mediator.As was shown in our research,Fm was an intermediate to improve the active center of GPO,so that the electronic transfer efficiency in the electrode was improved.And that could achieve the current response of two-enzyme modified electrode to glycerol.Using electrochemical methods,the GK was proved that it could convert glycerol into Glycerol-3-Phosphate under the participation of ATP(Mg²⁺can accelerate this process)and the catalytic reaction reaction on CNTs/GK/GPO/CS electrode surface was occurred.After this two enzyme modified electrode was optimized,the maximum catalytic current density was 135.28?A/cm².in which CNTs is 4.0 mg/m L,GK is 4.0 mg/m L,and GPO is 2.0 mg/mL in the mixture.Finally,we had successfully synthesized sulfur doped carbon by a facile high-temperature molten salt bath method,which was the oxygen reduction catalyst at cathode in enzyme biofuel cell.In the method,high temperature melting K₂S was a source of high concentration of sulfur and salt bath,so as to provide the solid-liquid two-phase interface to promote the contact of sulfur source and carbon source.N₂ ab/desorption and Raman showed S^2-reacted with C,causing the S atom enter into the C skeleton.XPS distinguished three types of sulfur content,that was,K₂S,C-S-C and C-SO_x.The sample S-XC72-950synthesized in 950 ^oC showed chemical doping S is 1.50 at.%,and the doping of the S atom increased the performance of its oxygen reduction.