Synthesis Of Supported Praseodymium Lanthanum Nickelate Perovskite And Its Catalytic Performance For The Pyrolysis Of Lignin

Lignin is the only renewable resource in nature that can produce aromatic-based compounds,and the high value utilization of lignin is achieved by catalytic pyrolysis to phenolic compounds.In this paper,a series of La_1-xPr_xNi O₃ chalcogenides（HLPN-x）were synthesized by a combination of sol-gel and template method,the preparation parameters were optimized,and the characterization instruments such as X-ray diffractometer（XRD）,scanning electron microscope（SEM）,specific surface area tester（BET）,thermogravimetric differential thermal analyzer（TG）,X-ray photoelectron spectroscopy analyzer（XPS）were used to the crystalline phase,morphology,pore structure,thermal stability and elemental endowment valence of the synthesized chalcocite samples were analyzed;HLPN-0.2 was used as a carrier and loaded with two metal active elements,Mg and Mo,by vacuum isovolumetric impregnation,and the monolayer dispersion effect of Mg O or Mo O₃ on HLPN-x was investigated by XRD extrapolation,and the monolayer dispersion thresholds were determined respectively,and their effects on The kinetics and catalytic pyrolysis performance of organic solvent lignin（OL）were investigated,and the composition of the gas and liquid phase products were analyzed qualitatively and quantitatively to obtain their regeneration laws.The main contents of the paper are as follows:（1）HLPN-x chalcogenide samples with honeycomb structure were synthesized by using resorcinol/formaldehyde resin（RF）nanomicrospheres as templates,and their crystallinity could reach 99.75%when x=0.2,and they were loose and porous,and their specific surface area increased from 18.607 m²/g to 33.509 m²/g compared with the samples without added templating agent.（2）HLPN-0.2 was loaded with two metal active elements,Mo and Mg,respectively,by vacuum isovolumetric impregnation,and the dispersion thresholds of Mo O₃/HLPN-0.2 were calculated to be 1.14%and 2.39%for Mg O/HLPN-0.2 by XRD extrapolation.（3）The kinetics of catalytic pyrolysis of OL by HLPN-0.2,1%Mo O₃/HLPN-0.2 and 2%Mg O/HLPN-0.2 were investigated by the Coats-Redfern integration method,and the activation energy of the pyrolysis reaction was 167.75 k J/mol when the pyrolysis temperature was 600°C and the catalyst-to-OL addition ratio was 1:3,compared to that of pure OL.HLPN-0.2,1%Mo O₃/HLPN-0.2 and 2%Mg O/HLPN-0.2 reduced the activation energy of the OL pyrolysis reaction by 36.19 k J/mol,54.94 k J/mol and 70.29 k J/mol,respectively,which proved that the loading of alkaline earth metals was more favorable to the catalytic pyrolysis of lignin.（4）The performance evaluation of OL catalytic pyrolysis was carried out in a miniature fixed-bed reactor under its optimized pyrolysis conditions,i.e.,m（HLPN-0.2）:m（OL）=1:3,a pyrolysis temperature of 600°C,an N₂ rate of 10°C/min,and a holding time of 3 h.Compared with the liquid product yield of 14.88%during the pyrolysis of pure OL with HLPN-0.2,1%Mo O₃/HLPN-0.2 and 2%Mg O/HLPN-0.2 as catalysts,the liquid product yields increased to 21.34%,22.89%and 23.21%,respectively.The selectivity of phenols and guaiacols were improved by 26.62%and 40.07%,respectively,when 1%Mo O₃/HLPN-0.2was used as the catalyst,and the selectivity of guaiacols was improved by 122.88%when 2%Mg O/HLPN-0.2 was used as the catalyst.（5）The catalysts could be regenerated after oxidation under air atmosphere after the reaction and could be recycled.After five reaction-regenerations,the crystalline structures of HLPN-0.2,1%Mo O₃/HLPN-0.2 and 2%Mg O/HLPN-0.2 remained basically unchanged,indicating their good structural stability;the yields of the liquid-phase products after five pyrolysis reactions-regenerations with the three catalysts did not change significantly,indicating their good selectivity.