Preparation Of Manganese Based Perovskite Oxide And Its Catalytic Pyrolysis Performance Of Bagasse Lignin

In the sugar industry,a large amount of bagasse waste is produced,wherein cellulose and hemicellulose can be used for fermentation to produce ethanol,and the remaining 20%-30%of lignin is still not effectively utilized.Due to its complex physical structure and stable chemical properties,it is very difficult to directly convert it into low molecular weight chemicals.By introducing a catalytic action during its conversion process,the cleavage of a particular type of chemical bond can be increased,thereby increasing the selectivity and yield of the product.Therefore,the synthesis of high-efficiency catalysts becomes the key to the catalytic degradation of lignin.Firstly,a series of manganese-based perovskite oxides AMnO₃?A=Sr,Ca,Ba?were synthesized by solid phase method and sol-gel method,and Pr element was doped in SrMnO₃for sol-gel method.Secondly,the crystal phase,surface functional group,morphology,specific surface area,and degree of crystal dispersion of the prepared oxide were characterized using X-ray diffractometer?XRD?,Fourier transform infrared spectrometer?FT-IR?,electron scanning microscope?SEM?,Specific surface area analysis?BET?,Laser particle size analyzer?PSD?,respectively.Finally,the performance of the catalyzed pyrolysis of bagasse lignin was evaluated in a fixed-bed microreactor.The compositions of liquid phase product for the catalytic pyrolysis of bagasse lignin were analyzed by gas chromatography/mass spectrometry?GC/MS?.The results were as following:?1?The optimal synthesis process parameters of solid phase method:calcination temperature is 1100°C,tableting time is 10 min,tableting pressure is 20 Mpa,prepared perovskite oxide particle size is 200-500 nm,dense and smooth structure,and particles The degree of aggregation is higher;the optimum synthesis parameters of the sol-gel method are:pH 8.5,calcination temperature of 800°C,M_EDTA:M_{metal ion}:M_{citric acid}=1:1:1.6,preparation of perovskite oxide particle size is 150 nm,the size is relatively uniform,and it is loose and porous.?2?The results of perovskite catalytic pyrolysis of bagasse lignin thermogravimetric experiments showed that the catalyst SrMnO₃ in AMnO₃?A=Ca,Sr,Ba?prepared by sol-gel method has obvious catalytic effect,and its end point in pyrolysis process the temperature can be lowered by 12°C,and the weight loss rate is increased by 4%,which promotes the formation of more liquid phase products and gas phase products.?3?The catalytic pyrolysis results of bagasse lignin in the fixed bed reaction:the process parameters are reaction is temperature 600°C,reaction time is 2 h,the optimum ratio of catalyst to bagasse lignin is 1:3.The catalyst prepared by the sol-gel method has better catalytic effect.When the catalyst is SrMnO₃,the liquid yield can reach 27.92%.The liquid phase products are mainly phenols,guaiacols,syringols,phenyl ethers and benzophenones.The selectivity of the phenolic product reached 73.26%.?4?With the doping of Pr,the liquid phase yield is higher than that of undoped.When the Pr doping amount is 0.2,Sr_0.8Pr_0.2MnO₃ catalyzes the best solution of bagasse lignin,and the liquid phase yield is 30.91%,phenolic selectivity is as high as 75.18%,indicating that the number of oxygen vacancies is increased after doping,providing more reactive oxygen for the reaction.?5?After the regeneration of Sr_0.8Pr_0.2MnO₃,there was no significant change in the characteristic peak of perovskite before the reaction,and the crystal phase remained unchanged.The catalytic selectivity of the regenerated Sr_0.8Pr_0.2MnO₃ also did not change significantly,indicating that the catalyst has good stability and regeneration performance and can be recycled.