Study On The Enhanced Lignin Degradation Process Of Higee-Microwave Coupled Reactor

Lignin is a renewable resource,and high value-added chemicals can be obtained by performing the catalytic oxidation degradation of lignin.Catalytic oxidation degradation of lignin is a gas-liquid-solid multi-phase reaction system,and heat and mass transfer have obvious effects on the lignin degradation.Stirred tank reactor（STR）has poor heat and mass transfer,and the transmission efficiency of the lignin degradation process does not match the reaction origin,which leads to the problem of low process efficiency and low product yield of catalytic oxidation degradation.Therefore,this project proposed to study on the enhanced lignin degradation process of Higee-microwave coupled reactor.Firstly,study on the gas-liquid mass transfer law in Higee-microwave coupled device.Then,we investigted the reaction kinetics of lignin catalytic oxidation degradation in Rotating Packed Bed（RPB）and Higee-microwave coupled reactors,respectively.On the basis,the catalytic oxidation degradation process of lignin in Higee-microwave coupled reactor was studied.The main conclusions were summarized as follows:（1）Study on nano-CuO enhanced gas-liquid mass transfer law in Higee-microwave coupled device.The influence of operating parameters on the mass transfer coefficient（K_Ya）of CO₂ was studied and better operating conditions were obtained:vapor liquid ratio of 60,treatment volume of 300m L·min^-1,rotating speed of 2000 r·min^-1,nano-CuO concentration of 0.4 g·L^-1,CO₂ concentration of 10%,NaOH concentration of 2.0 mol·L^-1.K_Ya of CO₂under this condition was 0.153 kmol·m^-3·s^-1.（2）Reaction kinetics of lignin catalytic oxidative degradation in RPB.The reaction kinetic equation was established,and the reaction series of G-lignin concentration and oxygen pressure were 1.7 and 0.63,respectively;and the apparent activation energy was 23.3 k J·mol^-1.（3）Reaction kinetics of lignin catalytic oxidative degradation in Higee-microwave coupled reactor.The reaction kinetic equation was established,and the reaction series of G-lignin concentration and oxygen pressure were 1.5 and 0.6,respectively;and the apparent activation energy was 20.6 k J·mol^-1.（4）The catalytic oxidative degradation process of lignin by nano-CuO in Higee-microwave coupled reactor.The influence of the condition of lignin catalytic oxidation degradation on the yield was investigated by one-factor experiment,and optimal process conditions were obtained(P_O=0.4 MPa,c _NaOH=2.0 mol·L^-1、rotating speed=1400 r·min^-1、c _SL=50 g·L^-1、c_nano-CuO=2.5g·L^-1、T=418.15 K、t=25 min).Under the better process conditions,the aromatic aldehyde yield was 5.82 wt%.Compared with STR,the aromatic aldehyde yield was 11.3%higher and the lignin degradation efficiency was80%higher in the Higee-microwave coupled reactor.