Study On CuO/HZSM-5 Degradation Of Lignin And Enhancement Of Higee Microwave Coupling

Lignin is the most abundant carbon source on the planet.Because of its rich aromatic units,lignin is considered to be one of the most potential renewable fuel sources;it can be degraded into high value-added chemicals,which can be used in perfumes,pharmaceutical intermediates,etc.However,due to the complex structure of lignin and the difficulty of separation and degradation,the utilization efficiency of lignin is low.The urgent task to solve this problem is to find an efficient and economical lignin degradation method.In this thesis,CuO/HZSM-5 is used for wet catalytic oxidation of lignin,the lignin oxidative degradation process conditions are systematically explored,the lignin oxidation kinetics are discussed,and the kinetic equation is established.This thesis also studied the law of highgravity coupled reactor to heat the lignin system.The main research content and conclusions are as follows:(1)Catalysts with different loadings were prepared,and CuO(15%)HZSM-5 with better catalytic performance was selected as the catalyst for this investigation.The process conditions of CuO/HZSM-5 oxidative degradation of lignin were systematically explored.The best process conditions are:lignin concentration of 50 g/L,total pressure of 2 MPa,oxygen partial pressure of 0.4 MPa,reaction time of 40 min,NaOH solution The concentration is 2.5 mol/L,the speed of the parallel autoclave is 800 rpm,the reaction time is 40 min,3 g/L CuO(15%)/HZSM-5,150?.Under these conditions,the vanillin concentration is 875.7 mg/L,the syringaldehyde concentration is 1489.9 mg/L,the yield of vanillin was 51.1%(based on guaiacyl lignin),and the yield of syringaldehyde was 31.5%(based on syringyl lignin).(2)Kinetic experiments were carried out at lignin concentration of 40?70 g/L,oxygen partial pressure 0.4?0.7 MPa,130?150?,and it was found that CuO/HZSM-5 oxidative degradation of lignin is a secondary reaction,which is consistent with domestic and foreign The kinetics of oxidized lignin is consistent.(3)The orderliness of high-gravity microwave coupling to strengthen the heat supply of the lignin system was studied,and the law of the influence of time,high-gravity speed,feed flow,microwave source,microwave power,CuO/HZSM-5 on the temperature distribution around the filler and the outlet temperature was explored.It is found that microwave heating requires a stable process.After heating for 4 minutes,the temperature around the filler basically does not change.The temperature distribution at high speed is more uniform,but the heating time is short,and the outlet temperature is lower.Under the same conditions,the greater the flow rate,the greater the temperature distribution The more uniform,the greater the flow rate,the lower the outlet temperature.The outlet temperature of a single microwave is higher than the outlet temperature of dual microwaves.The greater the power,the higher the outlet temperature,and the power has a greater impact on the single microwave,containing CuO/HZSM-5 solution temperature Significantly higher,and with the increase of CuO/HZSM-5 content,the heating rate increases.